Jérôme Prado

The brain network for deductive reasoning: A quantitative meta-analysis of 28 neuroimaging studies

Over the course of the past decade, contradictory claims have been made regarding the neural bases of deductive reasoning. Researchers have been puzzled by apparent inconsistencies in the literature. Some have even questioned the effectiveness of the methodology used to study the neural bases of deductive reasoning. However, the idea that neuroimaging findings are inconsistent is not based on any quantitative evidence. Here, we report the results of a quantitative meta-analysis of 28 neuroimaging studies of deductive reasoning published between 1997 and 2010, combining 382 participants. Consistent areas of activations across studies were identified using the multilevel kernel density analysis method. We found that results from neuroimaging studies are more consistent than what has been previously assumed. Overall, studies consistently report activations in specific regions of a left fronto-parietal system, as well as in the left BG. This brain system can be decomposed into three subsystems that are specific to particular types of deductive arguments: relational, categorical, and propositional. These dissociations explain inconstancies in the literature. However, they are incompatible with the notion that deductive reasoning is supported by a single cognitive system relying either on visuospatial or rule-based mechanisms. Our findings provide critical insight into the cognitive organization of deductive reasoning and need to be accounted for by cognitive theories.

Distinct representations of subtraction and multiplication in the neural systems for numerosity and language.

It has been proposed that recent cultural inventions such as symbolic arithmetic recycle evolutionary older neural mechanisms. A central assumption of this hypothesis is that the degree to which a preexisting mechanism is recycled depends on the degree of similarity between its initial function and the novel task. To test this assumption, we investigated whether the brain region involved in magnitude comparison in the intraparietal sulcus (IPS), localized by a numerosity comparison task, is recruited to a greater degree by arithmetic problems that involve number comparison (single‐digit subtractions) than by problems that involve retrieving number facts from memory (single‐digit multiplications). Our results confirmed that subtractions are associated with greater activity in the IPS than multiplications, whereas multiplications elicit greater activity than subtractions in regions involved in verbal processing including the middle temporal gyrus (MTG) and inferior frontal gyrus (IFG) that were localized by a phonological processing task. Pattern analyses further indicated that the neural mechanisms more active for subtraction than multiplication in the IPS overlap with those involved in numerosity comparison and that the strength of this overlap predicts interindividual performance in the subtraction task. These findings provide novel evidence that elementary arithmetic relies on the cooption of evolutionary older neural circuits. Hum Brain Mapp, 2011.

Overcoming Perceptual Features in Logical Reasoning: A Parametric Functional Magnetic Resonance Imaging Study

Participants experience difficulty detecting that an item depicting an H-in-a-square confirms the logical rule, If there is not a T then there is not a circle. Indeed, there is a perceptual conflict between the items mentioned in the rule (T and circle) and in the test item (H and square). Much evidence supports the claim that correct responding depends on detecting and resolving such conflicts. One aim of this study is to find more precise neurological evidence in support of this claim by using a parametric event-related functional magnetic resonance imaging (fMRI) paradigm. We scanned 20 participants while they were required to judge whether or not a conditional rule was verified (or falsified) by a corresponding target item. We found that the right middorsolateral prefrontal cortex (mid-DLPFC) was specifically engaged, together with the medial frontal (anterior cingulate and presupplementary motor area [pre-SMA]) and parietal cortices, when mismatching was present. Activity in these regions was also linearly correlated with the level of mismatch between the rule and the test item. Furthermore, a psychophysiological interaction analysis revealed that activation of the mid-DLPFC, which increases as mismatching does, was accompanied by a decrease in functional integration with the bilateral primary visual cortex and an increase in functional integration with the right parietal cortex. This indicates a need to break away from perceptual cues in order to select an appropriate logical response. These findings strongly indicate that the regions involved in inhibitory control (including the right mid-DLPFC and the medial frontal cortex) are engaged when participants have to overcome perceptual mismatches in order to provide a logical response. These findings are also consistent with neuroimaging studies investigating the belief bias, where prior beliefs similarly interfere with logical reasoning.

Variations of response time in a selective attention task are linked to variations of functional connectivity in the attentional network

Although variations of response time (RT) within a particular experimental condition are typically ignored, they may sometimes reflect meaningful changes in the efficiency of cognitive and neural processes. In the present study, we investigated whether trial-by-trial variations of response time (RT) in a cross-modal selective attention task were associated with variations of functional connectivity between brain regions that are thought to underlie attention. Sixteen healthy young adults performed an audiovisual selective attention task, which involved attending to a relevant visual letter while ignoring an irrelevant auditory letter, as we recorded their brain activity using functional magnetic resonance imaging (fMRI). In line with predictions, variations of RT were associated with variations of functional connectivity between the anterior cingulate cortex and various other brain regions that are posited to underlie attentional control, such as the right dorsolateral prefrontal cortex and bilateral regions of the posterior parietal cortex. They were also linked to variations of functional connectivity between anatomically early and anatomically late regions of the relevant-modality visual cortex whose communication is thought to be modulated by attentional control processes. By revealing that variations of RT in a selective attention task are linked to variations of functional connectivity in the attentional network, the present findings suggest that variations of attention may contribute to trial-by-trial fluctuations of behavioral performance.

How Humans Reach: Distinct Cortical Systems for Central and Peripheral Vision

Lesions of the posterior parietal cortex in humans can produce a specific disruption of visually guided hand movements termed optic ataxia. The fact that the deficit mainly occurs in peripheral vision suggests that reaching in foveal and extrafoveal vision relies on two different anatomical substrates. Using fMRI in healthy subjects, the authors demonstrated the existence of two systems, differently modulated by the two reaching conditions. Reaching in central vision involves a restricted network, including the medial intraparietal sulcus (mIPS) and the caudal part of the dorsal premotor cortex (PMd). Reaching in peripheral vision engages a more extensive network, including the parieto-occipital junction (POJ). Interestingly, POJ corresponds to the site of the lesion overlap that the authors recently found to be responsible for optic ataxia. These two sets of results converge to show that there is not a unique cortical network for reaching control but instead two systems engaged in reaching to targets in the central and peripheral visual field.

Heightened interactions between a key default-mode region and a key task-positive region are linked to suboptimal current performance but to enhanced future performance.

According to the default-mode interference hypothesis, suboptimal performance in tasks requiring selective attention occurs when off-task processing (e.g., mind wandering) supported by default-mode regions interferes with on-task processing (e.g., attention) enabled by task-positive regions. In the present functional MRI study, we therefore investigated whether suboptimal performance in a selective attention task was linked to heightened interactions between a key default-mode region (the posterior cingulate cortex; PCC) and a key task-positive region (the left dorsolateral prefrontal cortex; DLPFC). We also investigated whether heightened interactions between the PCC and the left DLPFC were linked to enhanced future performance, consistent with prior data suggesting that such interactions index adaptive changes to the cognitive system. In line with both of these predictions, increases of current-trial functional connectivity between the PCC and the left DLPFC were linked to increases of response time in the current trial (i.e., suboptimal performance), but to decreases of response time in the next trial (i.e., enhanced performance). This double dissociation provides novel support for the default-mode interference hypothesis. Moreover, it suggests the possibility that, in at least some cases, default-mode interference indexes processes that optimize future performance.

Recomposing a fragmented literature: How conditional and relational arguments engage different neural systems for deductive reasoning

Deductive reasoning is traditionally viewed as a unitary process involving either rule-based or visuo-spatial mechanisms. However, there is a disagreement in the neuroimaging literature on whether the data support one alternative over the other. Here we test the hypothesis that discrepancies in the literature result from the reasoning materials themselves. Using functional magnetic resonance imaging, we measure brain activity of participants while they integrate the premises of conditional arguments (primarily Modus Tollens: If P then Q; not-Q) and Relational Syllogisms (i.e., linear arguments of the sort P is to the left of Q; Q is to the left of R). We find that reasoning with Modus Tollens activates the left inferior frontal gyrus to a greater extent than the Relational Syllogisms. In contrast, the Relational Syllogisms engage the right temporo-parieto-occipital junction more than conditional arguments. This suggests that conditional reasoning relies more on so-called syntactic processes than relational reasoning, while relational reasoning may rely on visuo-spatial processes and mental imagery more than conditional reasoning. This investigative approach, together with its results, clarifies some apparently inconsistent findings in this literature by showing that the nature of the logical argument, whether it is relational or conditional, determines which neural system is engaged.

Running the number line: Rapid shifts of attention in single-digit arithmetic

It has been recently proposed that adults might solve single-digit addition and subtraction problems by rapidly moving through an ordered representation of numbers. In the present study, we tested whether these movements manifest themselves by on-line shifts of attention during arithmetic problem-solving. In two experiments, adult participants were presented with single-digit addition, subtraction and multiplication problems. Operands and operator were presented sequentially on the screen. Although both the first operand and the operator were presented at the center of the screen, the second operand was presented either to the left or to the right side of space. We found that addition problems were solved faster when the second operand appeared to the right than to the left side (Experiments 1 & 2). In contrast, subtraction problems were solved faster when the second operand appeared to the left than to the right side (Experiment 1). No operation-dependent spatial bias was observed in the same time window when the second operand was zero (Experiment 1), and no bias was observed when the operation was a multiplication (Experiment 2). Therefore, our results demonstrate that solving single-digit addition and subtraction, but not multiplication, is associated with horizontal shifts of attention. Our findings support the idea that mental movements to the left or right of a sequential representation of numbers are elicited during single-digit arithmetic.

Heightened activity in a key region of the ventral attention network is linked to reduced activity in a key region of the dorsal attention network during unexpected shifts of covert visual spatial attention.

To enable unexpected shifts of covert visual spatial attention, a ventral attention network is thought to dampen activity in a dorsal attention network that maintains the current focus of attention. However, direct evidence to support this view is scarce. In the present study, we investigated this hypothesis by asking healthy young adults to perform a covert visual spatial attention task while their brain activity was recorded with functional magnetic resonance imaging (fMRI). In each trial, participants discriminated the orientation of a target-colored letter in the cued visual field (valid trials) or, occasionally, in the uncued visual field (invalid trials). Consistent with prior work, the ventral attention network was more active in invalid trials than in valid trials. Most importantly, functional connectivity analyses revealed that an increase of activity in the right inferior frontal gyrus (a key region of the ventral attention network) was linked to smaller increases of activity in (a) the right inferior parietal lobe (a key region of the dorsal attention network) and (b) the left dorsolateral prefrontal cortex and dorsal anterior cingulate cortex (other regions enabling the control of attention) in invalid trials, relative to valid trials. These findings provide novel support for the view that key regions of the ventral attention network help to enable unexpected shifts of covert visual spatial attention by dampening activity in brain regions that participate in maintaining the current focus of attention.

Spatial associations in relational reasoning: Evidence for a SNARC-like effect

Relational reasoning (A > B, B > C, therefore A > C) shares a number of similarities with numerical cognition, including a common behavioural signature, the symbolic distance effect. Just as reaction times for evaluating relational conclusions decrease as the distance between two ordered objects increases, people need less time to compare two numbers when they are distant (e.g., 2 and 8) than when they are close (e.g., 3 and 4). Given that some remain doubtful about such analogical representations in relational reasoning, we determine whether numerical cognition and relational reasoning have other overlapping behavioural effects. Here, using relational reasoning problems that require the alignment of six items, we provide evidence showing that the subjects’ linear mental representation affects motor performance when evaluating conclusions. Items accessible from the left part of a linear representation are evaluated faster when the response is made by the left, rather than the right, hand and the reverse is observed for items accessible from the right part of the linear representation. This effect, observed with the prepositions to the left of and to the right of as well as with above and below, is analogous to the SNARC (Spatial Numerical Association of Response Codes) effect, which is characterized by an interaction between magnitude of numbers and side of response.