Yuko Sassa

Failing to deactivate: the association between brain activity during a working memory task and creativity.

Working memory (WM) is an essential component for human higher order cognitive activities. Creativity has been essential to the development of human civilization. Previous studies from different fields have suggested creativity and capacity of WM have opposing characteristics possibly in terms of diffuse attention. However, despite a number of functional imaging studies on creativity, how creativity relates to brain activity during WM has never been investigated. In this functional magnetic resonance imaging (fMRI) study, we investigated this issue using an n-back WM paradigm and a psychometric measure of creativity (a divergent thinking test). A multiple regression analysis revealed that individual creativity was significantly and positively correlated with brain activity in the precuneus during the 2-back task (WM task), but not during the non-WM 0-back task. As the precuneus shows deactivation during cognitive tasks, our findings show that reduced task induced deactivation (TID) in the precuneus is associated with higher creativity measured by divergent thinking. The precuneus is included in the default mode network, which is deactivated during cognitive tasks. The magnitude of TID in the default mode network is considered to reflect the reallocation of cognitive resources from networks irrelevant to the performance of the task. Thus, our findings may indicate that individual creativity, as measured by the divergent thinking test, is related to the inefficient reallocation of attention, congruent with the idea that diffuse attention is associated with individual creativity.

Regional gray matter volume of dopaminergic system associate with creativity: Evidence from voxel-based morphometry

Creativity has been essential to the development of human civilization and plays a crucial role in cultural life. However, despite a number of functional imaging studies on creativity, the relationship between regional gray matter morphology and creativity has never been investigated in subcortical regions. We used voxel-based morphometry (VBM) to identify the gray matter correlates of individual creativity as measured by the divergent thinking test. We found positive correlations between regional gray matter volume and individual creativity in several regions such as the right dorsolateral prefrontal cortex, bilateral striata and in an anatomical cluster which included areas such as the substantia nigra, tegmental ventral area and periaqueductal gray. These findings suggest that individual creativity, as measured by the divergent thinking test, is mainly related to the regional gray matter of brain regions known to be associated with the dopaminergic system, congruent with the idea that dopaminergic physiological mechanisms are associated with individual creativity.

White matter structures associated with creativity: evidence from diffusion tensor imaging.

Creativity has been essential to the development of human civilization and plays a crucial role in cultural life. However, despite literature that has proposed the importance of structural connectivity in the brain for creativity, the relationship between regional white matter integrity and creativity has never been directly investigated. In this study, we used diffusion tensor imaging and a behavioral creativity test of divergent thinking to investigate the relationship between creativity and structural connectivity. We examined associations between creativity and fractional anisotropy across the brain in healthy young adult (mean age, 21.7 years old; [SD]=1.44) men (n=42) and women (n=13). After controlling for age, sex, and score on Ravens advanced progressive matrices, a test for psychometric measures of intelligence, significant positive relationships between fractional anisotropy and individual creativity as measured by the divergent thinking test were observed in the white matter in or adjacent to the bilateral prefrontal cortices, the body of the corpus callosum, the bilateral basal ganglia, the bilateral temporo-parietal junction and the right inferior parietal lobule. As a whole, these findings indicate that integrated white matter tracts underlie creativity. These pathways involve the association cortices and the corpus callosum, which connect information in distant brain regions and underlie diverse cognitive functions that support creativity. Thus, our results are congruent with the ideas that creativity is associated with the integration of conceptually distant ideas held in different brain domains and architectures and that creativity is supported by diverse high-level cognitive functions, particularly those of the frontal lobe.

The Association between Resting Functional Connectivity and Creativity

The analysis of functional connectivity at rest (rFC) enables us to know how brain regions within and between networks interact. In this study, we used resting-state functional magnetic resonance imaging and a creativity test of divergent thinking (DT) to investigate the relationship between creativity measured by DT and rFC. We took the medial prefrontal cortex (mPFC) to be the seed region and investigated correlations across subjects between the score of the DT test and the strength of rFC between the mPFC and other brain regions. Our results showed that the strength of rFC with the mPFC significantly and positively correlated with creativity as measured by the DT test in the posterior cingulate cortex (PCC). These results showed that higher creativity measured by DT is associated with rFC between the mPFC and the PCC, the key nodes of the default mode network (DMN). Increased rFC between these regions is completely opposite from that is generally expected from the association between higher creativity and reduced deactivation in DMN during an externally directed attention-demanding task shown in our previous study but is similar to the pattern seen in relatives of schizophrenia. These findings are comparable to the previously reported psychological associations between schizotypy and creativity.

Working Memory Training Using Mental Calculation Impacts Regional Gray Matter of the Frontal and Parietal Regions

Training working memory (WM) improves performance on untrained cognitive tasks and alters functional activity. However, WM trainings effects on gray matter morphology and a wide range of cognitive tasks are still unknown. We investigated this issue using voxel-based morphometry (VBM), various psychological measures, such as non-trained WM tasks and a creativity task, and intensive adaptive training of WM using mental calculations (IATWMMC), all of which are typical WM tasks. IATWMMC was associated with reduced regional gray matter volume in the bilateral fronto-parietal regions and the left superior temporal gyrus. It improved verbal letter span and complex arithmetic ability, but deteriorated creativity. These results confirm the training-induced plasticity in psychological mechanisms and the plasticity of gray matter structures in regions that have been assumed to be under strong genetic control.

Effects of Training of Processing Speed on Neural Systems

Processing speed (PS) training improves performance on untrained PS tasks in the elderly. However, PS trainings effects on the PS of young adults and on neural mechanisms are still unknown. In humans, we investigated this issue using psychological measures, voxel-based morphometry, the n-back task [a typical task for functional magnetic resonance imaging (fMRI) studies with conditions of 0-back (simple cognitive processes) and 2-back tasks (working memory; WM)], resting-state fMRI for the analysis of functional connectivity between brain regions during rest (resting-FC), and intensive adaptive training of PS. PS training was associated with (1) significant or substantial improvement in the performance of PS measures, (2) changes in the gray matter structures of the left superior temporal gyrus and the bilateral regions around the occipitotemporal junction, (3) changes in functional activity that are related to simple cognitive processes (but not those of WM) in the left perisylvian region, and (4) increased resting-FC between the left perisylvian area and the area that extends to the lingual gyrus and calcarine cortex. These results confirm the PS-training-induced plasticity in PS and the training-induced plasticity of functions and structures that are associated with speeded cognitive processes. The observed neural changes caused by PS training may give us new insights into how PS training, and possibly other cognitive training, can improve PS.

Multiple brain networks for visual self-recognition with different sensitivity for motion and body part.

Multiple brain networks may support visual self-recognition. It has been hypothesized that the left ventral occipito-temporal cortex processes ones own face as a symbol, and the right parieto-frontal network processes self-image in association with motion-action contingency. Using functional magnetic resonance imaging, we first tested these hypotheses based on the prediction that these networks preferentially respond to a static self-face and to moving ones whole body, respectively. Brain activation specifically related to self-image during familiarity judgment was compared across four stimulus conditions comprising a two factorial design: factor Motion contrasted picture (Picture) and movie (Movie), and factor Body part a face (Face) and whole body (Body). Second, we attempted to segregate self-specific networks using a principal component analysis (PCA), assuming an independent pattern of inter-subject variability in activation over the four stimulus conditions in each network. The bilateral ventral occipito-temporal and the right parietal and frontal cortices exhibited self-specific activation. The left ventral occipito-temporal cortex exhibited greater self-specific activation for Face than for Body, in Picture, consistent with the prediction for this region. The activation profiles of the right parietal and frontal cortices did not show preference for Movie Body predicted by the assumed roles of these regions. The PCA extracted two cortical networks, one with its peaks in the right posterior, and another in frontal cortices; their possible roles in visuo-spatial and conceptual self-representations, respectively, were suggested by previous findings. The results thus supported and provided evidence of multiple brain networks for visual self-recognition.

Effects of working memory training on functional connectivity and cerebral blood flow during rest

Working memory (WM) training (WMT) alters the task-related brain activity and structure of the external attention system (EAS). We investigated whether WMT also alters resting-state brain mechanisms, which are assumed to reflect intrinsic brain activity and connectivity. Our study subjects were subjected to a 4-week WMT program and brain scans before and after the intervention for determining changes of functional connectivity and regional cerebral blood flow during rest (resting-FC/resting-rCBF). Compared with no-intervention, WMT (a) increased resting-FC between the medial prefrontal cortex (mPFC) and precuneus, which are key nodes of the default mode network (DMN), (b) decreased resting-FC between mPFC and the right posterior parietal cortex/right lateral prefrontal cortex (LPFC), which are key nodes of the EAS, and (c) increased resting-rCBF in the right LPFC. However, the training-related decreases in resting-FC between the key DMN node and the nodes of EAS were only observed when the whole brain signal was regressed out in individual analyses, and these changes were not observed when the whole brain signal was not regressed out in individual analyses. Further analyses indicated that these differences may be mediated by a weak but a widespread increase in resting-FC between the nodes of EAS and activity of multiple bilateral areas across the brain. These results showed that WMT induces plasticity in neural mechanisms involving DMN and the EAS during rest and indicated that intrinsic brain activity and connectivity can be affected by cognitive training.

Topological Organization of Functional Brain Networks in Healthy Children: Differences in Relation to Age, Sex, and Intelligence

Recent studies have demonstrated developmental changes of functional brain networks derived from functional connectivity using graph theoretical analysis, which has been rapidly translated to studies of brain network organization. However, little is known about sex- and IQ-related differences in the topological organization of functional brain networks during development. In this study, resting-state fMRI (rs-fMRI) was used to map the functional brain networks in 51 healthy children. We then investigated the effects of age, sex, and IQ on economic small-world properties and regional nodal properties of the functional brain networks. At a global level of whole networks, we found significant age-related increases in the small-worldness and local efficiency, significant higher values of the global efficiency in boys compared with girls, and no significant IQ-related difference. Age-related increases in the regional nodal properties were found predominately in the frontal brain regions, whereas the parietal, temporal, and occipital brain regions showed age-related decreases. Significant sex-related differences in the regional nodal properties were found in various brain regions, primarily related to the default mode, language, and vision systems. Positive correlations between IQ and the regional nodal properties were found in several brain regions related to the attention system, whereas negative correlations were found in various brain regions primarily involved in the default mode, emotion, and language systems. Together, our findings of the network topology of the functional brain networks in healthy children and its relationship with age, sex, and IQ bring new insights into the understanding of brain maturation and cognitive development during childhood and adolescence.

Regional gray and white matter volume associated with Stroop interference: evidence from voxel-based morphometry.

During Stroop tasks, subjects experience cognitive interference when they resolve interferences such as identifying the ink color of a printed word while ignoring the words identity. Stroop paradigms are commonly used as an index of attention deficits and a tool for investigating the functions of the frontal lobes and other associated structures. Despite these uses and the vast amount of attention given to Stroop paradigms, the regional gray matter volume/regional white matter volume (rGMV/rWMV) correlates of Stroop interference have not yet been identified at the whole brain level in normal adults. We examined this issue using voxel-based morphometry in right-handed healthy young adults. We found significant negative relationships between the Stroop interference rate and rGMV in the anterior cingulate cortex (ACC), right inferior frontal gyrus, and cerebellum. Furthermore, we found relationships between the Stroop interference rate and rWMV in bilateral anatomical clusters that extended around extensive WM regions in the dorsal part of the frontal lobe. These findings are the first to reveal rGMV/rWMV that underlie the performance of the Stroop task, a widely used psychological paradigm at the whole brain level. Of note, our findings support the notion that ACC contributes to Stroop performance and show the involvement of regions that have been implicated in response inhibition and attention.