Kosslyn SM.
If neuroimaging is the answer, what is the question?
Philos Trans R Soc Lond B Biol Sci. 1999 Jul 29;354(1387):1283-94.
"It is unclear that we will come to a better understanding of mental processes simply by observing which neural loci are activated while subjects perform a task. Rather, I suggest here that it is better to come armed with a question that directs one to design tasks in ways that take advantage of the strengths of neuroimaging techniques (particularly positron emission tomography and functional magnetic resonance imaging). Here I develop a taxonomy of types of questions that can be easily addressed by such techniques. The first class of questions focuses on how information processing is implemented in the brain; these questions can be posed at a very coarse scale, focusing on the entire system that confers a particular ability, or at increasingly more specific scales, ultimately focusing on individual structures or processes. The second class of questions focuses on specifying when particular processes and structures are invoked; these questions focus on how one can use patterns of activation to infer that specific processes and structures were invoked, and on how processing changes in different circumstances. The use of neuroimaging to address these questions is illustrated with results from experiments on visual cognition, and caveats regarding the logic of inference in each case are noted. Finally, the necessary interplay between neuroimaging and behavioural studies is stressed." [Abstract] [PDF]

Jung-Beeman M, Bowden EM, Haberman J, Frymiare JL, Arambel-Liu S, et al.
Neural Activity When People Solve Verbal Problems with Insight.
PLoS Biol 2(4): e97 DOI:10.1371/journal.pbio.0020097. 2004.
"People sometimes solve problems with a unique process called insight, accompanied by an “Aha!” experience. It has long been unclear whether different cognitive and neural processes lead to insight versus noninsight solutions, or if solutions differ only in subsequent subjective feeling. Recent behavioral studies indicate distinct patterns of performance and suggest differential hemispheric involvement for insight and noninsight solutions. Subjects solved verbal problems, and after each correct solution indicated whether they solved with or without insight. We observed two objective neural correlates of insight. Functional magnetic resonance imaging (Experiment 1) revealed increased activity in the right hemisphere anterior superior temporal gyrus for insight relative to noninsight solutions. The same region was active during initial solving efforts. Scalp electroencephalogram recordings (Experiment 2) revealed a sudden burst of high-frequency (gamma-band) neural activity in the same area beginning 0.3 s prior to insight solutions. This right anterior temporal area is associated with making connections across distantly related information during comprehension. Although all problem solving relies on a largely shared cortical network, the sudden flash of insight occurs when solvers engage distinct neural and cognitive processes that allow them to see connections that previously eluded them." [Full Text]

Parsons, Lawrence M., Osherson, Daniel
New Evidence for Distinct Right and Left Brain Systems for Deductive versus Probabilistic Reasoning
Cereb. Cortex 2001 11: 954-965
"Deductive and probabilistic reasoning are central to cognition but the functional neuroanatomy underlying them is poorly understood. The present study contrasted these two kinds of reasoning via positron emission tomography. Relying on changes in instruction and psychological ‘set’, deductive versus probabilistic reasoning was induced using identical stimuli. The stimuli were arguments in propositional calculus not readily solved via mental diagrams. Probabilistic reasoning activated mostly left brain areas whereas deductive activated mostly right. Deduction activated areas near right brain homologues of left language areas in middle temporal lobe, inferior frontal cortex and basal ganglia, as well as right amygdala, but not spatial–visual areas. Right hemisphere activations in the deduction task cannot be explained by spill-over from overtaxed, left language areas. Probabilistic reasoning was mostly associated with left hemispheric areas in inferior frontal, posterior cingulate, parahippocampal, medial temporal, and superior and medial prefrontal cortices. The foregoing regions are implicated in recalling and evaluating a range of world knowledge, operations required during probabilistic thought. The findings confirm that deduction and induction are distinct processes, consistent with psychological theories enforcing their partial separation. The results also suggest that, except for statement decoding, deduction is largely independent of language, and that some forms of logical thinking are non-diagrammatic." [Full Text]

Goel V, Dolan RJ.
Differential involvement of left prefrontal cortexin inductive and deductive reasoning.
Cognition. 2004 Oct;93(3):B109-21.
"While inductive and deductive reasoning are considered distinct logical and psychological processes, little is known about their respective neural basis. To address this issue we scanned 16 subjects with fMRI, using an event-related design, while they engaged in inductive and deductive reasoning tasks. Both types of reasoning were characterized by activation of left lateral prefrontal and bilateral dorsal frontal, parietal, and occipital cortices. Neural responses unique to each type of reasoning determined from the Reasoning Type (deduction and induction) by Task (reasoning and baseline) interaction indicated greater involvement of left inferior frontal gyrus (BA 44) in deduction than induction, while left dorsolateral (BA 8/9) prefrontal gyrus showed greater activity during induction than deduction. This pattern suggests a dissociation within prefrontal cortex for deductive and inductive reasoning." [Abstract]

Knauff M, Fangmeier T, Ruff CC, Johnson-Laird PN.
Reasoning, models, and images: behavioral measures and cortical activity.
J Cogn Neurosci. 2003 May 15;15(4):559-73.
"The goal of this study was to investigate the neurocognitive processes of mental imagery in deductive reasoning. Behavioral studies yielded four sorts of verbal relations: (1) visuospatial relations that are easy to envisage both visually and spatially; (2) visual relations that are easy to envisage visually but hard to envisage spatially; (3) spatial relations that are hard to envisage visually but easy to envisage spatially; and (4) control relations that are hard to envisage both visually and spatially. In three experiments, visual relations slowed the process of reasoning in comparison with control relations, whereas visuospatial and spatial relations yielded inferences comparable to those of control relations. An experiment using functional magnetic resonance imaging showed that in the absence of any correlated visual input (problems were presented acoustically via headphones), all types of reasoning problems evoked activity in the left middle temporal gyrus, in the right superior parietal cortex, and bilaterally in the precuneus. In the prefrontal cortex, increased activity was found in the middle and inferior frontal gyri. However, only the problems based on visual relations also activated areas of the visual association cortex corresponding to V2. The results indicate that cortical activity during reasoning depends on the nature of verbal relations. All relations elicit mental models that underlie reasoning, but visual relations in addition elicit visual images. This account resolves inconsistencies in the previous literature." [Abstract] [PDF]

Knauff M, Mulack T, Kassubek J, Salih HR, Greenlee MW.
Spatial imagery in deductive reasoning: a functional MRI study.
Brain Res Cogn Brain Res. 2002 Apr;13(2):203-12.
"Various cognitive theories aim to explain human deductive reasoning: (1) mental logic theories claim syntactic language-based proofs of derivation, (2) the mental model theory proposes cognitive processes of constructing and manipulating spatially organized mental models, and (3) imagery theories postulate that such abilities are based on visual mental images. To explore the neural substrates of human deductive reasoning, we examined BOLD (blood oxygen level dependent) contrasts of twelve healthy participants during relational and conditional reasoning with whole-brain functional magnetic resonance imaging (fMRI). The results indicate that, in the absence of any correlated visual input, reasoning activated an occipitoparietal-frontal network, including parts of the prefrontal cortex (Brodmann's area, BA, 6, 9) and the cingulate gyrus (BA 32), the superior and inferior parietal cortex (BA 7, 40), the precuneus (BA 7), and the visual association cortex (BA 19). In the discussion, we first focus on the activated occipito-parietal pathway that is well known to be involved in spatial perception and spatial working memory. Second, we briefly relate the activation in the prefrontal cortical areas and in the anterior cingulate gyrus to other imaging studies on higher cognitive functions. Finally, we draw some general conclusions and argue that reasoners envisage and inspect spatially organized mental models to solve deductive inference problems." [Abstract]

Zacks JM, Ollinger JM, Sheridan MA, Tversky B.
A parametric study of mental spatial transformations of bodies.
Neuroimage. 2002 Aug;16(4):857-72.
"TWO CLASSES OF MENTAL SPATIAL TRANSFORMATION CAN BE DISTINGUISHED: Object-based spatial transformations are imagined movements of objects; and egocentric perspective transformations are imagined movements of one's point of view. The hypothesis that multiple neural systems contribute to these mental imagery operations was tested with functional MRI. Participants made spatial judgments about pictures of human bodies, and brain activity was analyzed as a function of the judgment required and the time taken to respond. Areas in right temporal, occipital and parietal cortex and the medial superior cerebellum appear to be differentially involved in object-based spatial transformations. Additionally, midline structures and lateral parietal cortex were found to decrease in activity during the spatial reasoning tasks, independently of the judgment required or of the latency of response. The results are discussed in terms of a model of spatial reasoning that postulates specialized subsystems for performing object-based and egocentric perspective image transformations." [Abstract]

Goel V, Gold B, Kapur S, Houle S.
Neuroanatomical correlates of human reasoning.
J Cogn Neurosci. 1998 May;10(3):293-302.
"One of the important questions cognitive theories of reasoning must address is whether logical reasoning is inherently sentential or spatial. A sentential model would exploit nonspatial (linguistic) properties of representations whereas a spatial model would exploit spatial properties of representations. In general terms, the linguistic hypothesis predicts that the language processing regions underwrite human reasoning processes, and the spatial hypothesis suggests that the neural structures for perception and motor control contribute the basic representational building blocks used for high-level logical and linguistic reasoning. We carried out a [(15)O] H(2)O PET imaging study to address this issue. Twelve normal volunteers performed three types of deductive reasoning tasks (categorical syllogisms, three-term spatial relational items, and three-term nonspatial relational items) while their regional cerebral blood flow pattern was recorded using [(15)O] H(2)O PET imaging. In the control condition subjects semantically comprehended sets of three sentences. In the deductive reasoning conditions subjects determined whether the third sentence was entailed by the first two sentences. The areas of activation in each reasoning condition were confined to the left hemisphere and were similar to each other and to activation reported in previous studies. They included the left inferior frontal gyrus (Brodmann area 45, 47), a portion of the left middle frontal gyrus (Brodmann area 46), the left middle temporal gyrus (Brodmann areas 21, 22), a region of the left lateral inferior temporal gyrus and superior temporal gyrus (Brodmann areas 22, 37), and a portion of the left cingulate gyrus (Brodmann areas 32, 24). There was no significant right-hemisphere or parietal activation. These results are consistent with previous neuroimaging studies and raise questions about the level of involvement of classic spatial regions in reasoning about linguistically presented spatial relations." [Abstract] [PDF]

Goel V, Dolan RJ.
Functional neuroanatomy of three-term relational reasoning.
Neuropsychologia. 2001;39(9):901-9.
"In a recent study we demonstrated that reasoning with categorical syllogisms engages two dissociable mechanisms. Reasoning involving concrete sentences engaged a left hemisphere linguistic system while formally identical arguments, involving abstract sentences, recruited a parietal spatial network. The involvement of a parietal visuo-spatial system in abstract syllogism reasoning raised the question whether argument forms involving explicit spatial relations (or relations that can be easily mapped onto spatial relations) are sufficient to engage the parietal system? We addressed this question in an event-related fMRI study of three-term relational reasoning, using sentences with concrete and abstract content. Our findings indicate that both concrete and abstract three-term relational arguments activate a similar bilateral occipital-parietal-frontal network. However, the abstract reasoning condition engendered greater parietal activation than the concrete reasoning condition. We conclude that arguments involving relations that can be easily mapped onto explicit spatial relations engage a visuo-spatial system, irrespective of concrete or abstract content." [Abstract] [PDF]

Goel, V.
Cognitive Neuroscience of Deductive Reasoning.
In Cambridge Handbook of Thinking & Reasoning, Eds. K. Holyoak & R. Morrison. Cambridge UniversityPress. 2003. [PDF]

Goel V, Dolan RJ.
Anatomical segregation of component processes in an inductive inference task.
J Cogn Neurosci. 2000 Jan;12(1):110-9.
"Inductive inference underlies much of human cognition. The essential component of induction is hypothesis selection based on some criterion of relevance. The purpose of this study was to determine the neural substrate of inductive inference, particularly hypothesis selection, using fMRI. Ten volunteers were shown stimuli consisting of novel animals under two task conditions, and asked to judge whether all the animals in the set were the same type of animal. In one condition, subjects were given a rule that specified the criteria for "same type of animal". In the other condition, subjects had to infer the rule without instruction. The two conditions were further factored into easy and difficult components. Rule inference was specifically associated with bilateral hippocampal activation while the task by difficulty interaction was associated with activation in right lateral orbital prefrontal cortex. We interpret the former in terms of semantic encoding of novel stimuli and the latter in terms of hypothesis selection. Thus, we show an anatomical dissociation between task implementation and task difficulty that may correspond to a critical psychological distinction in the processes necessary for inductive inference." [Abstract]

Goel V, Gold B, Kapur S, Houle S.
The seats of reason? An imaging study of deductive and inductive reasoning.
Neuroreport. 1997 Mar 24;8(5):1305-10.
"We carried out a neuroimaging study to test the neurophysiological predictions made by different cognitive models of reasoning. Ten normal volunteers performed deductive and inductive reasoning tasks while their regional cerebral blood flow pattern was recorded using [15O]H2O PET imaging. In the control condition subjects semantically comprehended sets of three sentences. In the deductive reasoning condition subjects determined whether the third sentence was entailed by the first two sentences. In the inductive reasoning condition subjects reported whether the third sentence was plausible given the first two sentences. The deduction condition resulted in activation of the left inferior frontal gyrus (Brodmann areas 45, 47). The induction condition resulted in activation of a large area comprised of the left medial frontal gyrus, the left cingulate gyrus, and the left superior frontal gyrus (Brodmann areas 8, 9, 24, 32). Induction was distinguished from deduction by the involvement of the medial aspect of the left superior frontal gyrus (Brodmann areas 8, 9). These results are consistent with cognitive models of reasoning that postulate different mechanisms for inductive and deductive reasoning and view deduction as a formal rule-based process." [Abstract] [PDF]

Acuna BD, Eliassen JC, Donoghue JP, Sanes JN.
Frontal and parietal lobe activation during transitive inference in humans.
Cereb Cortex. 2002 Dec;12(12):1312-21.
"Cortical areas engaged in knowledge manipulation during reasoning were identified with functional magnetic resonance imaging (MRI) while participants performed transitive inference (TI) on an ordered list of 11 items (e.g. if A < B and B < C, then A < C). Initially, participants learned a list of arbitrarily ordered visual shapes. Learning occurred by exposure to pairs of list items that were adjacent in the sequence. Subsequently, functional MR images were acquired as participants performed TI on non-adjacent sequence items. Control tasks consisted of height comparisons (HT) and passive viewing (VIS). Comparison of the TI task with the HT task identified activation resulting from TI, termed 'reasoning', while controlling for rule application, decision processes, perception, and movement, collectively termed 'support processes'. The HT-VIS comparison revealed activation related to support processes. The TI reasoning network included bilateral prefrontal cortex (PFC), pre-supplementary motor area (preSMA), premotor area (PMA), insula, precuneus, and lateral posterior parietal cortex. By contrast, cortical regions activated by support processes included the bilateral supplementary motor area (SMA), primary motor cortex (M1), somatic sensory cortices, and right PMA. These results emphasize the role of a prefrontal-parietal network in manipulating information to form new knowledge based on familiar facts. The findings also demonstrate PFC activation beyond short-term memory to include mental operations associated with reasoning." [Abstract]

Wharton CM, Grafman J, Flitman SS, Hansen EK, Brauner J, Marks A, Honda M.
Toward neuroanatomical models of analogy: a positron emission tomography study of analogical mapping.
Cognit Psychol. 2000 May;40(3):173-97.
"Several brain regions associated with analogical mapping were identified using (15)O-positron emission tomography with 12 normal, high intelligence adults. Each trial presented during scanning consisted of a source picture of colored geometric shapes, a brief delay, and a target picture of colored geometric shapes. Analogous pictures did not share similar geometric shapes but did share the same system of abstract visuospatial relations. Participants judged whether each source-target pairing was analogous (analogy condition) or identical (literal condition). The results of the analogy-literal comparison showed activation in the dorsomedial frontal cortex and in the left hemisphere; the inferior, middle, and medial frontal cortices; the parietal cortex; and the superior occipital cortex. Based on these results as well as evidence from relevant cognitive neuroscience studies of reasoning and of executive working memory, we hypothesize that analogical mapping is mediated by the left prefrontal and inferior parietal cortices." [Abstract]

Luo Q, Perry C, Peng D, Jin Z, Xu D, Ding G, Xu S.
The neural substrate of analogical reasoning: an fMRI study.
Brain Res Cogn Brain Res. 2003 Oct;17(3):527-34.
"This study investigated the anatomical substrate of analogical reasoning using functional magnetic resonance imaging. In the study, subjects performed a verbal analogy task (e.g., soldier is to army as drummer is to band) and, to control for activation caused by purely semantic access, a semantic judgment task. Significant activation differences between the verbal analogy and the semantic judgment task were found bilaterally in the prefrontal cortex (right BA 11/BA 47 and left BA45), the fusiform gyrus, and the basal ganglia; left lateralized in the postero-superior temporal gyrus (BA 22) and the (para) hippocampal region; and right lateralized in the anterior cingulate. The role of these areas in analogical reasoning is discussed." [Abstract]

Ruff CC, Knauff M, Fangmeier T, Spreer J.
Reasoning and working memory: common and distinct neuronal processes.
Neuropsychologia. 2003;41(9):1241-53.
"The neuronal processes underlying reasoning and the related working memory subsystems were examined with functional magnetic resonance imaging (fMRI). Twelve volunteers solved relational reasoning problems which either supported a single (determinate) or several alternative solutions (indeterminate). In a second condition, participants maintained the identical premises of these problems in working memory without making inferences. Although problems were presented in auditory format, activity was detected for both reasoning and maintenance in a network comprising bilaterally the secondary visual cortex, the posterior cingulate cortex, and the medial anterior frontal cortex. In direct comparisons, reasoning was associated with stronger dorsolateral and medial prefrontal activation than maintenance, whereas maintenance led to stronger lateral parietal activation than reasoning. Participants' visuo-spatial abilities ("Block Design" score) covaried positively with behavioral performance and negatively with activity of the precuneus for reasoning, but not for maintenance. These results support the notion that relational reasoning is based on visuo-spatial mental models, and they help to distinguish the neuronal processes related to reasoning itself versus to the maintenance of problem information in working memory." [Abstract]

Delazer M, Domahs F, Bartha L, Brenneis C, Lochy A, Trieb T, Benke T.
Learning complex arithmetic-an fMRI study.
Brain Res Cogn Brain Res. 2003 Dec;18(1):76-88.
"Aim of the present functional magnet resonance imaging (fMRI) study was to detect modifications of cerebral activation patterns related to learning arithmetic. Thirteen right-handed subjects were extensively trained on a set of 18 complex multiplication problems. In the following fMRI session, trained and untrained problems (closely matched for difficulty) were presented in blocked order alternating with a number matching task and a fact retrieval task. Importantly, left hemispheric activations were dominant in the two contrasts between untrained and trained condition, suggesting that learning processes in arithmetic are predominantly supported by the left hemisphere. Contrasting untrained versus trained condition, the left intraparietal sulcus showed significant activations, as well as the inferior parietal lobule. A further significant activation was found in the left inferior frontal gyrus. This activation may be accounted for by higher working memory demands in the untrained as compared to the trained condition. Contrasting trained versus untrained condition a significant focus of activation was found in the left angular gyrus. Following the triple-code model [Science 284 (1999) 970], the shift of activation within the parietal lobe from the intraparietal sulcus to the left angular gyrus suggests a modification from quantity-based processing to more automatic retrieval. The present study shows that the left angular gyrus is not only involved in arithmetic tasks requiring simple fact retrieval, but may show significant activations as a result of relatively short training of complex calculation." [Abstract]

Menon V, Mackenzie K, Rivera SM, Reiss AL.
Prefrontal cortex involvement in processing incorrect arithmetic equations: evidence from event-related fMRI.
Hum Brain Mapp. 2002 Jun;16(2):119-30.
"The main aim of this study was to investigate the differential processing of correct and incorrect equations to gain further insight into the neural processes involved in arithmetic reasoning. Electrophysiological studies in humans have demonstrated that processing incorrect arithmetic equations (e.g., 2 + 2 = 5) elicits a prominent event-related potential (ERP) compared to processing correct equations (e.g., 2 + 2 = 4). In the present study, we investigated the neural substrates of this process using event-related functional magnetic resonance imaging (fMRI). Subjects were presented with arithmetic equations and asked to indicate whether the solution displayed was correct or incorrect. We found greater activation to incorrect, compared to correct equations, in the left dorsolateral prefrontal cortex (DLPFC, BA 46) and the left ventrolateral prefrontal cortex (VLPFC, BA 47). Our results provide the first brain imaging evidence for differential processing of incorrect vs. correct equations. The prefrontal cortex activation observed in processing incorrect equations overlaps with brain areas known to be involved in working memory and interference processing. The DLPFC region differentially activated by incorrect equations was also involved in overall arithmetic processing, whereas the VLPFC was activated only during the differential processing of incorrect equations. Differential response to correct and incorrect arithmetic equations was not observed in parietal cortex regions such as the angular gyrus and intra-parietal sulcus, which are known to play a specific role in performing arithmetic computations. The pattern of brain response observed is consistent with the hypothesis that processing incorrect equations involves detection of an incorrect answer and resolution of the interference between the internally computed and externally presented incorrect answer. More specifically, greater activation during processing of incorrect equations appears to reflect additional operations involved in maintaining the results in working memory, while subjects attempt to resolve the conflict and select a response. These findings allow us to further delineate and dissociate the contributions of prefrontal and parietal cortices to arithmetic reasoning." [Abstract] [PDF]

Prabhakaran V, Rypma B, Gabrieli JD.
Neural substrates of mathematical reasoning: a functional magnetic resonance imaging study of neocortical activation during performance of the necessary arithmetic operations test.
Neuropsychology. 2001 Jan;15(1):115-27.
"Brain activation was examined using functional magnetic resonance imaging during mathematical problem solving in 7 young healthy participants. Problems were selected from the Necessary Arithmetic Operations Test (NAOT; R. B. Ekstrom, J. W. French, H. H. Harman, & D. Dermen, 1976). Participants solved 3 types of problems: 2-operation problems requiring mathematical reasoning and text processing, 1-operation problems requiring text processing but minimal mathematical reasoning, and 0-operation problems requiring minimal text processing and controlling sensorimotor demands of the NAOT problems. Two-operation problems yielded major activations in bilateral frontal regions similar to those found in other problem-solving tasks, indicating that the processes mediated by these regions subserve many forms of reasoning. Findings suggest a dissociation in mathematical problem solving between reasoning, mediated by frontal cortex, and text processing, mediated by temporal cortex." [Abstract]

Jacqueline N. Wood & Jordan Grafman
HUMAN PREFRONTAL CORTEX: PROCESSING AND REPRESENTATIONAL PERSPECTIVES
Nature Reviews Neuroscience 4, 139 -147 (2003); doi:10.1038/nrn1033
"Through evolution, humans have acquired 'higher' cognitive skills — such as language, reasoning and planning — and complex social behaviour. Evidence from neuropsychological and neuroimaging research indicates that the prefrontal cortex (PFC) underlies much of this higher cognition. A number of theories have been proposed for how the PFC might achieve this. Although many of these theories focus on the types of 'process' that the PFC carries out, we argue for the validity of a representational approach to understanding PFC function." [Abstract] [PDF]

Curtis CE, D'Esposito M.
Persistent activity in the prefrontal cortex during working memory.
Trends Cogn Sci. 2003 Sep;7(9):415-423.
"The dorsolateral prefrontal cortex (DLPFC) plays a crucial role in working memory. Notably, persistent activity in the DLPFC is often observed during the retention interval of delayed response tasks. The code carried by the persistent activity remains unclear, however. We critically evaluate how well recent findings from functional magnetic resonance imaging studies are compatible with current models of the role of the DLFPC in working memory. These new findings suggest that the DLPFC aids in the maintenance of information by directing attention to internal representations of sensory stimuli and motor plans that are stored in more posterior regions." [Abstract] [PDF]

Walter H, Bretschneider V, Gron G, Zurowski B, Wunderlich AP, Tomczak R, Spitzer M.
Evidence for quantitative domain dominance for verbal and spatial working memory in frontal and parietal cortex.
Cortex. 2003 Sep-Dec;39(4-5):897-911.
"Neuroimaging studies in humans have shown that different working memory (WM) tasks recruit a common bilateral fronto-parietal cortical network. Animal studies as well as neuroimaging studies in humans have suggested that this network, in particular the prefrontal cortex, is preferentially recruited when material from different domains (e.g. spatial information or verbal/object information) has to be memorized. Early imaging studies have suggested qualitative dissociations in the prefrontal cortex for spatial and object/verbal WM, either in a left-right or a ventral-dorsal dimension. However, results from different studies are inconsistent. Moreover, recent fMRI studies have failed to find evidence for domain dependent dissociations of WM-related activity in prefrontal cortex. Here we present evidence from two independent fMRI studies using physically identical stimuli in a verbal and spatial WM task showing that domain dominance for WM does indeed exist, although only in the form of quantitative differences in activation and not in the form of a dissociation with different prefrontal regions showing mutually exclusive activation in different domains. Our results support a mixed dimension model of domain dominance for WM within the prefrontal cortex, with left ventral prefrontal cortex (PFC) supporting preferentially verbal WM and right dorsal PFC supporting preferentially spatial WM. The concept of domain dominance is discussed in the light of recent theories of prefrontal cortex function." [Abstract]

Reichle ED, Carpenter PA, Just MA.
The neural bases of strategy and skill in sentence-picture verification.
Cognit Psychol. 2000 Jun;40(4):261-95.
"This experiment used functional Magnetic Resonance Imaging to examine the relation between individual differences in cognitive skill and the amount of cortical activation engendered by two strategies (linguistic vs. visual-spatial) in a sentence-picture verification task. The verbal strategy produced more activation in language-related cortical regions (e.g., Broca's area), whereas the visual-spatial strategy produced more activation in regions that have been implicated in visual-spatial reasoning (e.g., parietal cortex). These relations were also modulated by individual differences in cognitive skill: Individuals with better verbal skills (as measured by the reading span test) had less activation in Broca's area when they used the verbal strategy. Similarly, individuals with better visual-spatial skills (as measured by the Vandenberg, 1971, mental rotation test) had less activation in the left parietal cortex when they used the visual-spatial strategy. These results indicate that language and visual-spatial processing are supported by partially separable networks of cortical regions and suggests one basis for strategy selection: the minimization of cognitive workload." [Abstract]

N. F. Ramsey, J. M. Jansma, G. Jager, T. Van Raalten, and R. S. Kahn
Neurophysiological factors in human information processing capacity
Brain Advance Access published on March 1, 2004, DOI 10.1093/brain/awh060.
Brain 127: 517-525.
"What determines how well an individual can manage the complexity of information processing demands when several tasks have to be executed simultaneously? Various theoretical frameworks address the mechanisms of information processing and the changes that take place when processes become automated, and brain regions involved in various types of information processing have been identified, as well as sequences of events in the brain. The neurophysiological substrate of human information processing capacity, i.e. the amount that can be processed simultaneously, is, however, unresolved, as is the basis of inter-individual variability in capacity. Automatization of cognitive functions is known to increase capacity to process additional tasks, but behavioural indices of automatization are poor predictors of processing capacity in individuals. Automatization also leads to a decline of brain activity in the working memory system. In this study, we test the hypothesis that processing capacity is closely related to the way that the brain adjusts to practice of a single cognitive task, i.e. to the changes in neuronal activity that accompany automatization as measured with functional MRI (fMRI). Using a task that taxes the working memory system, and is sensitive to automatization, performance improved while activity in the network declined, as expected. The key finding is that the magnitude of automatization-induced reduction of activity in this system was a strong predictor for the ability to perform two different working memory tasks simultaneously (after scanning). It explained 60% of the variation in information processing capacity across individuals. In contrast, the behavioural measures of automatization did not predict this. We postulate that automatization involves at least two partially independent neurophysiological mechanisms, i.e. (i) streamlining of neuronal communication which improves performance on a single task; and (ii) functional trimming of neuronal ensembles which enhances the capacity to accommodate processing of additional tasks, potentially by facilitating rapid switching of instruction sets or contexts. Finally, this study shows that fMRI can provide information that predicts behavioural output, which is not provided by overt behavioural measures." [Abstract]

Osaka N, Osaka M, Kondo H, Morishita M, Fukuyama H, Shibasaki H.
The neural basis of executive function in working memory: an fMRI study based on individual differences.
Neuroimage. 2004 Feb;21(2):623-31.
"Using fMRI, neural substrates of the executive system were investigated with respect to differences in working memory capacity. To explore the executive control processes, reading span test (RST) and read conditions were performed. Two subject groups were selected: those with large working memory capacities, labeled high-span subjects (HSS) according to the reading span test, and those with small working memory capacities, labeled low-span subjects (LSS). Significant activation was found mainly in three regions in comparison with the control: anterior cingulate cortex (ACC), left inferior frontal gyrus (IFG), visual association cortex (VAC) and superior parietal lobule (SPL). For both groups, the fMRI signal intensity increased in ACC and IFG during the RST condition compared to that under the read condition. A group difference was also found in the ACC and IFG region, specifically a significant increase in signal intensity was observed only for the HSS group but not for the LSS group. Behavioral data also showed that the performance was better in HSS than in LSS. Moreover, the cross correlation of signal change between ACC and IFG was higher in HSS than in LSS, indicating that the network system between ACC and IFG was more activated in HSS compared to that of LSS. These results suggest that executive function, that is, working attention controlling system is more active in HSS than in LSS. Moreover, the results confirmed our hypothesis that there is a general neural basis for the central executive function in both RST and previous LST (listening span test) tasks despite differences in modality-specific buffers." [Abstract]

Gray JR, Chabris CF, Braver TS.
Neural mechanisms of general fluid intelligence.
Nat Neurosci. 2003 Mar;6(3):316-22.
"We used an individual-differences approach to test whether general fluid intelligence (gF) is mediated by brain regions that support attentional (executive) control, including subregions of the prefrontal cortex. Forty-eight participants first completed a standard measure of gF (Raven's Advanced Progressive Matrices). They then performed verbal and nonverbal versions of a challenging working-memory task (three-back) while their brain activity was measured using functional magnetic resonance imaging (fMRI). Trials within the three-back task varied greatly in the demand for attentional control because of differences in trial-to-trial interference. On high-interference trials specifically, participants with higher gF were more accurate and had greater event-related neural activity in several brain regions. Multiple regression analyses indicated that lateral prefrontal and parietal regions may mediate the relation between ability (gF) and performance (accuracy despite interference), providing constraints on the neural mechanisms that support gF." [Abstract] [PDF]

Duncan, John, Seitz, Rudiger J., Kolodny, Jonathan, Bor, Daniel, Herzog, Hans, Ahmed, Ayesha, Newell, Fiona N., Emslie, Hazel
A Neural Basis for General Intelligence
Science 2000 289: 457-460
"Universal positive correlations between different cognitive tests motivate the concept of "general intelligence" or Spearman's g. Here the neural basis for g is investigated by means of positron emission tomography. Spatial, verbal, and perceptuo-motor tasks with high-g involvement are compared with matched low-g control tasks. In contrast to the common view that g reflects a broad sample of major cognitive functions, high-g tasks do not show diffuse recruitment of multiple brain regions. Instead they are associated with selective recruitment of lateral frontal cortex in one or both hemispheres. Despite very different task content in the three high-g-low-g contrasts, lateral frontal recruitment is markedly similar in each case. Many previous experiments have shown these same frontal regions to be recruited by a broad range of different cognitive demands. The results suggest that "general intelligence" derives from a specific frontal system important in the control of diverse forms of behavior." [Full Text]

Prabhakaran V, Smith JA, Desmond JE, Glover GH, Gabrieli JD.
Neural substrates of fluid reasoning: an fMRI study of neocortical activation during performance of the Raven's Progressive Matrices Test.
Cognit Psychol. 1997 Jun;33(1):43-63.
"We examined brain activation, as measured by functional magnetic resonance imaging, during problem solving in seven young, healthy participants. Participants solved problems selected from the Raven's Progressive Matrices Test, a test known to predict performance on a wide range of reasoning tasks. In three conditions, participants solved problems requiring (1) analytic reasoning; (2) figural or visuospatial reasoning; or (3) simple pattern matching that served as a perceptual-motor control. Right frontal and bilateral parietal regions were activated more by figural than control problems. Bilateral frontal and left parietal, occipital, and temporal regions were activated more by analytic than figural problems. All of these regions were activated more by analytic than match problems. Many of these activations occurred in regions associated with working memory. Figural reasoning activated areas involved in spatial and object working memory. Analytic reasoning activated additional areas involved in verbal working memory and domain-independent associative and executive processes. These results suggest that fluid reasoning is mediated by a composite of working memory systems." [Abstract]

Cabeza R, Dolcos F, Graham R, Nyberg L.
Similarities and differences in the neural correlates of episodic memory retrieval and working memory.
Neuroimage. 2002 Jun;16(2):317-30.
"Functional neuroimaging studies have shown that different cognitive functions activate overlapping brain regions. An activation overlap may occur because a region is involved in operations tapped by different cognitive functions or because the activated area comprises subregions differentially involved in each of the functions. To investigate these issues, we directly compared brain activity during episodic retrieval (ER) and working memory (WM) using event-related functional MRI (fMRI). ER was investigated with a word recognition test, and WM was investigated with a word delayed-response test. Two-phase trials distinguished between retrieval mode and cue-specific aspects of ER, as well as between encoding/maintenance and retrieval aspects of WM. The results revealed a common fronto-parieto-cerebellar network for ER and WM, as well as subregions differentially involved in each function. Specifically, there were two main findings. First, the results differentiated common and specific subregions within the prefrontal cortex: (i) left dorsolateral areas were recruited by both functions, possibly reflecting monitoring operations; (ii) bilateral anterior and ventrolateral areas were more activated during ER than during WM, possibly reflecting retrieval mode and cue-specific ER operations, respectively; and (iii) left posterior/ventral (Broca's area) and bilateral posterior/dorsal areas were more activated during WM than during ER, possibly reflecting phonological and generic WM operations, respectively. Second, hippocampal and parahippocampal regions were activated not only for ER but also for WM. This result suggests that indexing operations mediated by the medial temporal lobes apply to both long-term and short-term memory traces. Overall, our results show that direct cross-function comparisons are critical to understand the role of different brain regions in various cognitive functions." [Abstract] [PDF]

Rypma, Bart, Berger, Jeffrey S., D'Esposito, Mark
The Influence of Working-Memory Demand and Subject Performance on Prefrontal Cortical Activity
J. Cogn. Neurosci. 2002 14: 721-731
"Brain imaging and behavioral studies of working memory (WM) converge to suggest that the ventrolateral prefrontal cortex (PFC) mediates a capacity-limited storage buffer and that the dorsolateral PFC mediates memory organization processes that support supracapacity memory storage. Previous research from our laboratory has shown that the extent to which such memory organization processes are required depends on both task factors (i.e., memory load) and subject factors (i.e., response speed). Task factors exert their effects mainly during WM encoding while subject factors exert their effects mainly during WM retrieval. In this study, we sought to test the generalizability of these phenomena under more difficult memory-demand conditions than have been used previously. During scanning, subjects performed a WM task in which they were required to maintain between 1 and 8 letters over a brief delay. Neural activity was measured during encoding, maintenance, and retrieval task periods using event-related functional magnetic resonance imaging. With increasing memory load, there were reaction time increases and accuracy rate decreases, ventrolateral PFC activation decreases during encoding, and dorsolateral PFC activation increases during maintenance and retrieval. These results suggest that the ventrolateral PFC mediates WM storage and that the dorsolateral PFC mediates strategic memory organization processes that facilitate supracapacity WM storage. Additionally, high-performing subjects showed overall less activation than low-performing subjects, but activation increases with increasing memory load in the lateral PFC during maintenance and retrieval. Low-performing subjects showed overall more activation than high-performing subjects, but minimal activation increases in the dorsolateral PFC with increasing memory load. These results suggest that individual differences in both neural efficiency and cognitive strategy underlie individual differences in the quality of subjects' WM performance." [Abstract]

Silvia A. Bunge, Itamar Kahn, Jonathan D. Wallis, Earl K. Miller, and Anthony D. Wagner
Neural Circuits Subserving the Retrieval and Maintenance of Abstract Rules
J Neurophysiol 90: 3419-3428, 2003. First published 10.1152/jn.00910.2002
"Behavior is often governed by abstract rules or instructions for behavior that can be abstracted from one context and applied to another. Prefrontal cortex (PFC) is thought to be important for representing rules, although the contributions of ventrolateral (VLPFC) and dorsolateral (DLPFC) regions remain under-specified. In the present study, event-related fMRI was used to examine abstract rule representation in humans. Prior to scanning, subjects learned to associate unfamiliar shapes and nonwords with particular rules. During each fMRI trial, presentation of one of these cues was followed by a delay and then by sample and probe stimuli. Match and non-match rules required subjects to indicate whether or not the sample and probe matched; go rules required subjects to make a response that was not contingent on the sample/probe relation. Left VLPFC, parietal cortex, and pre-SMA exhibited sensitivity to rule type during the cue and delay periods. Delay-period activation in these regions, but not DLPFC, was greater when subjects had to maintain response contingencies (match, non-match) relative to when the cue signaled a specific response (go). In contrast, left middle temporal cortex exhibited rule sensitivity during the cue but not delay period. These results support the hypothesis that VLPFC interacts with temporal cortex to retrieve semantic information associated with a cue and with parietal cortex to retrieve and maintain relevant response contingencies across delays. Future investigations of cross-regional interactions will enable full assessment of this account. Collectively, these results demonstrate that multiple, neurally separable processes are recruited during abstract rule representation." [Abstract] [PDF]

Petrides M, Pandya DN.
Comparative cytoarchitectonic analysis of the human and the macaque ventrolateral prefrontal cortex and corticocortical connection patterns in the monkey.
Eur J Neurosci. 2002 Jul;16(2):291-310.
"A comparison of the cytoarchitecture of the human and the macaque monkey ventrolateral prefrontal cortex demonstrated a region in the monkey that exhibits the architectonic characteristic of area 45 in the human brain. This region occupies the dorsal part of the ventrolateral prefrontal convexity just below area 9/46v. Rostroventral to area 45 in the human brain lies a large cortical region labelled as area 47 by Brodmann. The ventrolateral component of this region extending as far as the lateral orbital sulcus has architectonic characteristics similar to those of the ventrolateral prefrontal region labelled by Walker as area 12 in the macaque monkey. We designated this region in both the human and the monkey ventrolateral prefrontal cortex as area 47/12. Thus, area 47/12 designates the specific part of the zone previously labelled as area 47 in the human brain that has the same overall architectonic pattern as that of Walker's area 12 in the macaque monkey brain. The cortical connections of these two areas were examined in the monkey by injecting fluorescent retrograde tracers. Although both area 45 and area 47/12 as defined here had complex multimodal input, they could be differentiated in terms of some of their inputs. Retrograde tracers restricted to area 47/12 resulted in heavy labelling of neurons in the rostral inferotemporal visual association cortex and in temporal limbic areas (i.e. perirhinal and parahippocampal cortex). In contrast, injections of tracers into dorsally adjacent area 45 demonstrated strong labelling in the superior temporal gyrus (i.e. the auditory association cortex) and the multimodal cortex in the upper bank of the superior temporal sulcus." [Abstract]

Wallis JD, Anderson KC, Miller EK.
Single neurons in prefrontal cortex encode abstract rules.
Nature. 2001 Jun 21;411(6840):953-6.
"The ability to abstract principles or rules from direct experience allows behaviour to extend beyond specific circumstances to general situations. For example, we learn the 'rules' for restaurant dining from specific experiences and can then apply them in new restaurants. The use of such rules is thought to depend on the prefrontal cortex (PFC) because its damage often results in difficulty in following rules. Here we explore its neural basis by recording from single neurons in the PFC of monkeys trained to use two abstract rules. They were required to indicate whether two successively presented pictures were the same or different depending on which rule was currently in effect. The monkeys performed this task with new pictures, thus showing that they had learned two general principles that could be applied to stimuli that they had not yet experienced. The most prevalent neuronal activity observed in the PFC reflected the coding of these abstract rules." [Abstract]

Jon M. Fincham, Cameron S. Carter, Vincent van Veen, V. Andrew Stenger, and John R. Anderson
Neural mechanisms of planning: A computational analysis using event-related fMRI
PNAS 99: 3346-3351. 2002.
"To investigate the neural mechanisms of planning, we used a novel adaptation of the Tower of Hanoi (TOH) task and event-related functional MRI. Participants were trained in applying a specific strategy to an isomorph of the five-disk TOH task. After training, participants solved novel problems during event-related functional MRI. A computational cognitive model of the task was used to generate a reference time series representing the expected blood oxygen level-dependent response in brain areas involved in the manipulation and planning of goals. This time series was used as one term within a general linear modeling framework to identify brain areas in which the time course of activity varied as a function of goal-processing events. Two distinct time courses of activation were identified, one in which activation varied parametrically with goal-processing operations, and the other in which activation became pronounced only during goal-processing intensive trials. Regions showing the parametric relationship comprised a frontoparietal system and include right dorsolateral prefrontal cortex [Brodmann's area (BA 9)], bilateral parietal (BA 40/7), and bilateral premotor (BA 6) areas. Regions preferentially engaged only during goal-intensive processing include left inferior frontal gyrus (BA 44). The implications of these results for the current model, as well as for our understanding of the neural mechanisms of planning and functional specialization of the prefrontal cortex, are discussed." [Full Text]

Newman SD, Carpenter PA, Varma S, Just MA.
Frontal and parietal participation in problem solving in the Tower of London: fMRI and computational modeling of planning and high-level perception.
Neuropsychologia. 2003;41(12):1668-82.
"This study triangulates executive planning and visuo-spatial reasoning in the context of the Tower of London (TOL) task by using a variety of methodological approaches. These approaches include functional magnetic resonance imaging (fMRI), functional connectivity analysis, individual difference analysis, and computational modeling. A graded fMRI paradigm compared the brain activation during the solution of problems with varying path lengths: easy (1 and 2 moves), moderate (3 and 4 moves) and difficult (5 and 6 moves). There were three central findings regarding the prefrontal cortex: (1) while both the left and right prefrontal cortices were equally involved during the solution of moderate and difficult problems, the activation on the right was differentially attenuated during the solution of the easy problems; (2) the activation observed in the right prefrontal cortex was highly correlated with individual differences in working memory (measured independently by the reading span task); and (3) different patterns of functional connectivity were observed in the left and right prefrontal cortices. Results obtained from the superior parietal region also revealed left/right differences; only the left superior parietal region revealed an effect of difficulty. These fMRI results converged upon two hypotheses: (1) the right prefrontal area may be more involved in the generation of a plan, whereas the left prefrontal area may be more involved in plan execution; and (2) the right superior parietal region is more involved in attention processes while the left homologue is more of a visuo-spatial workspace. A 4CAPS computational model of the cognitive processes and brain activation in the TOL task integrated these hypothesized mechanisms, and provided a reasonably good fit to the observed behavioral and brain activation data. The multiple research approaches presented here converge on a deepening understanding of the combination of perceptual and conceptual processes in this type of visual problem solving." [Abstract]

Sylvester CY, Wager TD, Lacey SC, Hernandez L, Nichols TE, Smith EE, Jonides J.
Switching attention and resolving interference: fMRI measures of executive functions.
Neuropsychologia. 2003;41(3):357-70.
"Is there a single executive process or are there multiple executive processes that work together towards the same goal in some task? In these experiments, we use counter switching and response inhibition tasks to examine the neural underpinnings of two cognitive processes that have often been identified as potential executive processes: the switching of attention between tasks, and the resolution of interference between competing task responses. Using functional magnetic resonance imaging (fMRI), for both event-related and blocked design tasks, we find evidence for common neural areas across both tasks in bilateral parietal cortex (BA 40), left dorsolateral prefrontal cortex (DLPFC; BA 9), premotor cortex (BA 6) and medial frontal cortex (BA 6/32). However, we also find areas preferentially involved in the switching of attention between mental counts (BA 7, BA 18) and the inhibition of a prepotent motor response (BA 6, BA 10), respectively. These findings provide evidence for the separability of cognitive processes underlying executive control." [Abstract]

Konishi S, Uchida I, Okuaki T, Machida T, Shirouzu I, Miyashita Y.
Neural correlates of recency judgment.
J Neurosci. 2002 Nov 1;22(21):9549-55.
"The prefrontal cortex plays a critical role in recollecting the temporal context of past events. The present study used event-related functional magnetic resonance imaging (fMRI) and explored the neural correlates of temporal-order retrieval during a recency judgment paradigm. In this paradigm, after study of a list of words presented sequentially, subjects were presented with two of the studied words simultaneously and were asked which of the two words was studied more recently. Two types of such retrieval trials with varied (high and low) levels of demand for temporal-order retrieval were intermixed and compared using event-related fMRI. The intraparadigm comparison of high versus low demand trials revealed brain regions with activation that was modulated on the basis of demand for temporal-order retrieval. Multiple lateral prefrontal regions including the middle and inferior lateral prefrontal cortex were prominently activated. Activation was also observed in the anterior prefrontal cortex and the medial temporal cortex, regions well documented to be related to memory retrieval in general. The modulation of brain activity in these regions suggests a detailed pathway that is engaged during recency judgment." [Full Text]

Hideaki Kawabata, and Semir Zeki
Neural Correlates of Beauty
J Neurophysiol 91: 1699-1705, 2004. 10.1152/jn.00696.2003
"We have used the technique of functional MRI to address the question of whether there are brain areas that are specifically engaged when subjects view paintings that they consider to be beautiful, regardless of the category of painting (that is whether it is a portrait, a landscape, a still life, or an abstract composition). Prior to scanning, each subject viewed a large number of paintings and classified them into beautiful, neutral, or ugly. They then viewed the same paintings in the scanner. The results show that the perception of different categories of paintings are associated with distinct and specialized visual areas of the brain, that the orbito-frontal cortex is differentially engaged during the perception of beautiful and ugly stimuli, regardless of the category of painting, and that the perception of stimuli as beautiful or ugly mobilizes the motor cortex differentially." [Abstract]

Moran JM, Wig GS, Adams RB Jr, Janata P, Kelley WM.
Neural correlates of humor detection and appreciation.
Neuroimage. 2004 Mar;21(3):1055-60.
"Humor is a uniquely human quality whose neural substrates remain enigmatic. The present report combined dynamic, real-life content and event-related functional magnetic resonance imaging (fMRI) to dissociate humor detection ("getting the joke") from humor appreciation (the affective experience of mirth). During scanning, subjects viewed full-length episodes of the television sitcoms Seinfeld or The Simpsons. Brain activity time-locked to humor detection moments revealed increases in left inferior frontal and posterior temporal cortices, whereas brain activity time-locked to moments of humor appreciation revealed increases in bilateral regions of insular cortex and the amygdala. These findings provide evidence that humor depends critically upon extant neural systems important for resolving incongruities (humor detection) and for the expression of affect (humor appreciation)." [Abstract]

Mattay VS, Berman KF, Ostrem JL, Esposito G, Van Horn JD, Bigelow LB, Weinberger DR.
Dextroamphetamine enhances "neural network-specific" physiological signals: a positron-emission tomography rCBF study.
J Neurosci. 1996 Aug 1;16(15):4816-22.
"Previous studies in animals and humans suggest that monoamines enhance behavior-evoked neural activity relative to nonspecific background activity (i.e., increase signal-to-noise ratio). We studied the effects of dextroamphetamine, an indirect monoaminergic agonist, on cognitively evoked neural activity in eight healthy subjects using positron-emission tomography and the O15 water intravenous bolus method to measure regional cerebral blood flow (rCBF). Dextroamphetamine (0.25 mg/kg) or placebo was administered in a double-blind, counterbalanced design 2 hr before the rCBF study in sessions separated by 1-2 weeks. rCBF was measured while subjects performed four different tasks: two abstract reasoning tasks--the Wisconsin Card Sorting Task (WCST), a neuropsychological test linked to a cortical network involving dorsolateral prefrontal cortex and other association cortices, and Ravens Progressive Matrices (RPM), a nonverbal intelligence test linked to posterior cortical systems--and two corresponding sensorimotor control tasks. There were no significant drug or task effects on pCO2 or on global blood flow. However, the effect of dextroamphetamine (i.e., dextroamphetamine vs placebo) on task-dependent rCBF activation (i.e., task - control task) showed double dissociations with respect to task and region in the very brain areas that most distinctly differentiate the tasks. In the superior portion of the left inferior frontal gyrus, dextroamphetamine increased rCBF during WCST but decreased it during RPM (ANOVA F (1,7) = 16.72, p < 0.0046). In right hippocampus, blood flow decreased during WCST but increased during RPM (ANOVA F(1,7) = 18.7, p < 0.0035). These findings illustrate that dextroamphetamine tends to "focus" neural activity, to highlight the neural network that is specific for a particular cognitive task. This capacity of dextroamphetamine to induce cognitively specific signal augmentation may provide a neurobiological explanation for improved cognitive efficiency with dextroamphetamine." [Abstract]

Mazoyer B, Zago L, Mellet E, Bricogne S, Etard O, Houde O, Crivello F, Joliot M, Petit L, Tzourio-Mazoyer N.
Cortical networks for working memory and executive functions sustain the conscious resting state in man.
Brain Res Bull. 2001 Feb;54(3):287-98.
"The cortical anatomy of the conscious resting state (REST) was investigated using a meta-analysis of nine positron emission tomography (PET) activation protocols that dealt with different cognitive tasks but shared REST as a common control state. During REST, subjects were in darkness and silence, and were instructed to relax, refrain from moving, and avoid systematic thoughts. Each protocol contrasted REST to a different cognitive task consisting either of language, mental imagery, mental calculation, reasoning, finger movement, or spatial working memory, using either auditory, visual or no stimulus delivery, and requiring either vocal, motor or no output. A total of 63 subjects and 370 spatially normalized PET scans were entered in the meta-analysis. Conjunction analysis revealed a network of brain areas jointly activated during conscious REST as compared to the nine cognitive tasks, including the bilateral angular gyrus, the left anterior precuneus and posterior cingulate cortex, the left medial frontal and anterior cingulate cortex, the left superior and medial frontal sulcus, and the left inferior frontal cortex. These results suggest that brain activity during conscious REST is sustained by a large scale network of heteromodal associative parietal and frontal cortical areas, that can be further hierarchically organized in an episodic working memory parieto-frontal network, driven in part by emotions, working under the supervision of an executive left prefrontal network." [Abstract]

Johnson-Frey SH.
What's so special about human tool use?
Neuron. 2003 Jul 17;39(2):201-4.
"Evidence suggests homologies in parietofrontal circuits involved in object prehension among humans and monkeys. Likewise, tool use is known to induce functional reorganization of their visuotactile limb representations. Yet, humans are the only species for whom tool use is a defining and universal characteristic. Why? Comparative studies of chimpanzee tool use indicate that critical differences are likely to be found in mechanisms involved in causal reasoning rather than those implementing sensorimotor transformations. Available evidence implicates higher-level perceptual areas in these processes." [Abstract]

Goel V, Dolan RJ.
Reciprocal neural response within lateral and ventral medial prefrontal cortex during hot and cold reasoning.
Neuroimage. 2003 Dec;20(4):2314-21.
"Logic is widely considered the basis of rationality. Logical choices, however, are often influenced by emotional responses, sometimes to our detriment, sometimes to our advantage. To understand the neural basis of emotionally neutral ("cold") and emotionally salient ("hot") reasoning we studied 19 volunteers using event-related fMRI, as they made logical judgments about arguments that varied in emotional saliency. Despite identical logical form and content categories across "hot" and "cold" reasoning conditions, lateral and ventral medial prefrontal cortex showed reciprocal response patterns as a function of emotional saliency of content. "Cold" reasoning trials resulted in enhanced activity in lateral/dorsal lateral prefrontal cortex (L/DLPFC) and suppression of activity in ventral medial prefrontal cortex (VMPFC). By contrast, "hot" reasoning trials resulted in enhanced activation in VMPFC and suppression of activation in L/DLPFC. This reciprocal engagement of L/DLPFC and VMPFC provides evidence for a dynamic neural system for reasoning, the configuration of which is strongly influenced by emotional saliency." [Abstract] [PDF]

Houde O, Zago L, Crivello F, Moutier S, Pineau A, Mazoyer B, Tzourio-Mazoyer N.
Access to deductive logic depends on a right ventromedial prefrontal area devoted to emotion and feeling: evidence from a training paradigm.
Neuroimage. 2001 Dec;14(6):1486-92.<