Sayako Masuda

Evaluating the roles of the inferior frontal gyrus and superior parietal lobule in deductive reasoning: An rTMS study

This study used off-line repetitive transcranial magnetic stimulation (rTMS) to examine the roles of the superior parietal lobule (SPL) and inferior frontal gyrus (IFG) in a deductive reasoning task. Subjects performed a categorical syllogistic reasoning task involving congruent, incongruent, and abstract trials. Twenty four subjects received magnetic stimulation to the SPL region prior to the task. In the other 24 subjects, TMS was administered to the IFG region before the task. Stimulation lasted for 10min, with an inter-pulse frequency of 1Hz. We found that bilateral SPL (Brodmann area (BA) 7) stimulation disrupted performance on abstract and incongruent reasoning. Left IFG (BA 45) stimulation impaired congruent reasoning performance while paradoxically facilitating incongruent reasoning performance. This resulted in the elimination of the belief-bias. In contrast, right IFG stimulation only impaired incongruent reasoning performance, thus enhancing the belief-bias effect. These findings are largely consistent with the dual-process theory of reasoning, which proposes the existence of two different human reasoning systems: a belief-based heuristic system; and a logic-based analytic system. The present findings suggest that the left language-related IFG (BA 45) may correspond to the heuristic system, while bilateral SPL may underlie the analytic system. The right IFG may play a role in blocking the belief-based heuristic system for solving incongruent reasoning trials. This study could offer an insight about functional roles of distributed brain systems in human deductive reasoning by utilizing the rTMS approach.

Longitudinal study of spatial working memory development in young children.

This study longitudinally compared activity in the frontal cortex during a spatial working memory task between 5-year-old and 7-year-old children using near-infrared spectroscopy. Eight children participated in this study twice, once at 5 years and once at 7 years of age. Behavioral analysis showed that older children performed the working memory task more precisely and more rapidly than younger children. Near-infrared spectroscopy analysis showed that right hemisphere dominance was observed in older children, whereas no hemispheric difference was apparent in younger children. Children with strengthened lateralization showed improved performance from 5 to 7 years. We therefore offer the first demonstration of the developmental changes in frontal cortical activation during spatial working memory tasks during the preschool period.

The role of inferior frontal cortex in belief-bias reasoning: An rTMS study

The belief-bias effect in syllogistic reasoning refers to the tendency for subjects to be erroneously biased when logical conclusions are incongruent with belief about the world. This study examined the role of inferior frontal cortex (IFC) in belief-bias reasoning using repetitive transcranial magnetic stimulation (rTMS). We used an off-line rTMS method to disrupt IFC activity transiently. Right IFC stimulation significantly impaired incongruent reasoning performance, enhancing the belief-bias effect. Subjects whose right IFC was impaired by rTMS may not be able to inhibit irrelevant semantic processing in incongruent trials. Although left IFC stimulation impaired congruent reasoning, it paradoxically facilitated incongruent reasoning performance, eliminating the belief-bias effect. Subjects whose left IFC was impaired by rTMS may not suffer from interference by irrelevant semantic processing. This study demonstrates for the first time the roles of left and right IFC in belief-bias reasoning using an rTMS approach.

Brain activation in adults who stutter under delayed auditory feedback: An fMRI study

It is well known that some people who stutter (PWS) show an immediate reduction of stuttering when they speak under a condition of delayed auditory feedback (DAF). In the present study, to investigate cortical activations during speech production through the DAF effect, we performed functional magnetic resonance imaging (fMRI) experiments under the NAF (non-altered feedback) and DAF conditions for PWS and people who do not stutter (PWNS). The results are that (1) the PWS showed the higher activation in the right inferior frontal gyrus (Brodmann Area (BA)45) than the PWNS under the NAF condition; (2) the activations of the right superior temporal gyrus and the right middle temporal gyrus were higher under the DAF condition than the NAF in both PWNS and PWS groups; (3) the PWNS showed the higher activation in the right supplementary motor area and superior temporal gyrus than the PWS under both NAF and DAF conditions; (4) the PWNS showed the higher activation in the inferior frontal gyrus(the right BA45 and the bilateral BA46) under the DAF condition than the NAF. These results reconfirm most of the previous findings with some slightly different activation areas, and underscore the involvement of inferior frontal gyrus and superior temporal gyrus in dysfluency.

An fMRI analysis of the efficacy of Euler diagrams in logical reasoning

We compared participant performance and brain activation changes during a syllogism-solving task with and without Euler diagrams, using functional magnetic resonance imaging (fMRI). Our experiment showed that when Euler diagrams were present, (i) response times in the task were significantly shorter than those in the usual reasoning task comprising only sentences, and (ii) the magnitude of activation in the left middle frontal gyrus (near BA 10), left inferior PFC (near BA 47), and left dorsal PFC (BA 6) was reduced. Result (i) provides evidence for the occurrence of cognitive offloading even when participants handle information of both sentences and diagrams in reasoning tasks. Result (ii) suggests that complex processes of inferences can be replaced by simple diagram manipulation. It is argued that cognitive details that are not fully specified by behavioral studies can be made salient using neuroscientific methods.