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Neuroimaging and behavioral evidence has suggested that the lateral prefrontal cortex is involved in individual differences in working memory capacity (WMC). However, few studies have localized the neural structures that differentiate high and low WMC individuals, considering the functional architecture of the prefrontal cortex. The present study aimed to identify a frontal region that underlies individual differences from the perspective of the hierarchical architecture of the frontal cortex. By manipulating an episodic factor of cognitive control (control in selecting an appropriate task set according to a temporal context) and using a parametric modulation analysis, we found that both high- and low- WMC individuals have similar activation patterns in the premotor cortex (BA6, 8), caudal prefrontal cortex (BA44, 45), and frontopolar cortex (BA10, 11), but differed in the rostral part of the prefrontal cortex (BA46/47); high WMC individuals showed greater activation in the higher episodic control condition, whereas low WMC individuals showed reduced activation when episodic control was required. Similar patterns of activation were found in the right inferior parietal and middle/inferior temporal cortices. These results indicate that the rostral prefrontal cortex, which supports episodic cognitive control, possibly by sending a weighting signal toward the inferior parietal and middle/inferior temporal cortices that modulate saliency and sensory processing, underlies individual differences in WMC. Episodic control account, which considers the organization of the prefrontal cortex, fits well with previous findings of individual differences in WMC., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The Default Mode Network (DMN) regions exhibit deactivation during a wide variety of resource demanding tasks. However, recent brain imaging studies reported that they also show activation during various cognitive activities. In addition, studies have found a negative correlation between the DMN and the working memory network (WMN). Here, we investigated activity in the DMN and WMN regions during preparation and execution phases of a verbal working memory task. Results showed that the core DMN regions, including the medial prefrontal cortex and posterior cingulate cortex, and WMN regions were activated during preparation. During execution, however, the WMN regions were activated but the DMN regions were deactivated. The results suggest that activation of these network regions is affected by allocation of attentional resources to the task relevant regions due to task demands. This study extends our previous results by showing that the core DMN regions exhibit activation during task preparation and deactivation during task execution.

Different people make different responses when they face a frustrating situation: some punish others (extrapunitive), while others punish themselves (intropunitive). Few studies have investigated the neural structures that differentiate extrapunitive and intropunitive individuals. The present fMRI study explored these neural structures using two different frustrating situations: an ego-blocking situation which blocks a desire or goal, and a superego-blocking situation which blocks self-esteem. In the ego-blocking condition, the extrapunitive group (n = 9) showed greater activation in the bilateral ventrolateral prefrontal cortex, indicating that these individuals prefer emotional processing. On the other hand, the intropunitive group (n = 9) showed greater activation in the left dorsolateral prefrontal cortex, possibly reflecting an effortful control for anger reduction. Such patterns were not observed in the superego-blocking condition. These results indicate that the prefrontal cortex is the source of individual differences in aggression direction in the ego-blocking situation.

A number of recent neuroimaging studies using self referential tasks have investigated whether self referential processing depends on a unique neural basis that operates specifically in the medial prefrontal cortex. However, these studies have provided contradictory results despite the use of similar methodologies. We hypothesized that these discrepancies are partially related to the task-difficulty that presents dissociations reaction times in the self- and other-referential tasks. We therefore measured brain activity during self and other referential tasks to determine if such activity can be dissociated according to the reaction times (fast versus slow) for the trait words. Activation differed across self and other only in the slow word condition. The self referential condition with slow reaction time produced greater activation in the ventromedial prefrontal cortex, whereas the other referential condition with slow reaction time produced activation of the middle temporal gyrus. Results suggested that the task-difficulty might affect whether or not brain activities within MPFC would be dissociated between self- and other-referential processing., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

This study examined dissociations between brain networks involved in theory of mind, which is needed for guessing others' mental states, and the self, which might constitute the basis for theory of mind's development. We used event-related fMRI to compare a condition that required participants to guess the mental state of a subject featured in first-person perspective sentences (1stPP condition) with a third-person perspective sentence condition (3rdPP condition). The caudate nucleus was marginally more activated in the 1stPP than in the 3rdPP condition, while the left dorsolateral prefrontal cortex (DLPFC) was significantly more activated in the 3rdPP condition as compared to the 1stPP condition. Furthermore, we examined the correlation between activation (signal intensity) of the caudate nucleus and left DLPFC with that of the right DLPFC, which is thought to be closely connected with sense of self. We found a significant correlation between caudate nucleus and right DLPFC activation in the 1stPP condition, and between left and right DLPFC activation in the 3rdPP condition. Although theory of mind and the self both appear to recruit the right DLPFC, this region seems to be accessed through the left DLPFC during theory of mind tasks, but through the caudate nucleus when tasks require self reference.

Background: The anterior prefrontal cortex (PFC) exhibits activation during some cognitive tasks, including episodic memory, reasoning, attention, multitasking, task sets, decision making, mentalizing, and processing of self-referenced information. However, the medial part of anterior PFC is part of the default mode network (DMN), which shows deactivation during various goal-directed cognitive tasks compared to a resting baseline. One possible factor for this pattern is that activity in the anterior medial PFC (MPFC) is affected by dynamic allocation of attentional resources depending on task demands. We investigated this possibility using an event related fMRI with a face working memory task., Methodology/principal Findings: Sixteen students participated in a single fMRI session. They were asked to form a task set to remember the faces (Face memory condition) or to ignore them (No face memory condition), then they were given 6 seconds of preparation period before the onset of the face stimuli. During this 6-second period, four single digits were presented one at a time at the center of the display, and participants were asked to add them and to remember the final answer. When participants formed a task set to remember faces, the anterior MPFC exhibited activation during a task preparation period but deactivation during a task execution period within a single trial., Conclusions/significance: The results suggest that the anterior MPFC plays a role in task set formation but is not involved in execution of the face working memory task. Therefore, when attentional resources are allocated to other brain regions during task execution, the anterior MPFC shows deactivation. The results suggest that activation and deactivation in the anterior MPFC are affected by dynamic allocation of processing resources across different phases of processing.

In recent years, several neuroimaging studies have suggested that the neural basis of the self-referential process1 is special, especially in the medial prefrontal cortex (MPFC). However, it remains controversial whether activity of the MPFC (and other related brain regions) appears only during the self-referential process. We investigated the neural correlates during the processing of references to the self, close other (friend), and distant other (prime minister) using fMRI. In comparison with baseline findings, referential processing to the three kinds of persons defined above showed common activation patterns in the dorsomedial prefrontal cortex (DMPFC), left middle temporal gyrus, left angular gyrus, posterior cingulate cortex and right cerebellum. Additionally, percent changes in BOLD signal in five regions of interest demonstrated the same findings. The result indicated that DMPFC was not special for the self-referential process, while there are common neural bases for evaluating the personalities of the self and others.

Working memory refers to the temporary maintenance and processing of information and involves executive processes that manipulate the contents of the working memory. The role of the executive function in the human left dorsolateral prefrontal cortex (LDLPFC) was explored using transcranial magnetic stimulation (TMS) after confirming the LDLPFC activation using fMRI. We applied double-pulse TMS having a 100-ms inter-pulse interval to LDLPFC immediately after the subjects finished reading the sentences of the reading span test (RST) task, an efficient measure of verbal working memory, in which dual tasks that include both sentence comprehension and word maintenance are required. Using eight normal participants, we found a significant deterioration of performance, i.e., decreased number of correctly reported words, in RST due to TMS stimulation of LDLPFC. Evidence suggests that transient functional disruption of the LDLPFC impairs performance in the maintenance processing of the RST task.

We examined aging effects on activation in the anterior cingulate cortex during a verbal working memory using functional magnetic resonance imaging. Ten young (mean age 25 years) and 10 elderly (mean age 69 years) healthy adults performed the reading span test in which performance reflects individual differences in verbal working memory. We found an age-related difference in executive function in the prefrontal cortex; younger participants showed significant anterior cingulate cortex activation whereas the elderly did not. We found that the anterior cingulate cortex plays a critical role in executive function related to working memory. We found that behavioral deficits in verbal working memory because of aging result from the deterioration of cognitive control owing to decreased activation of the anterior cingulate cortex.

Attention shifting in the working memory system plays an important role in goal-oriented behavior, such as reading, reasoning, and driving, because it involves several cognitive processes. This study identified brain activity leading to individual differences in attention shifting for dual-task performance by using the group comparison approach. A large-scale pilot study was initially conducted to select suitable good and poor performers. The fMRI experiment consisted of a dual-task condition and two single-task conditions. Under the dual-task condition, participants verified the status of letters while concurrently retaining arrow orientations. The behavioral results indicated that accuracy in arrow recognition was better in the good performers than in the poor performers under the dual-task condition but not under the single-task condition. Dual-task performance showed a positive correlation with mean signal change in the right anterior cingulate cortex (ACC) and right dorsolateral prefrontal cortex (DLPFC). Structural equation modeling indicated that effective connectivity between the right ACC and right DLPFC was present in the good performers but not in the poor performers, although activations of the task-dependent posterior regions were modulated by the right ACC and right DLPFC. We conclude that individual differences in attention shifting heavily depend on the functional efficiency of the cingulo-prefrontal network.