Journal

The Japanese journal of neuropsychology

[Vol.24 No.1 contents]
Japanese/English

Full Text of this Article
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ArticleTitle Development of prefrontal cortex: a cognitive neuroscience perspective
Language J
AuthorList Masao Aihara
Affiliation Department of Pediatrics, Faculty of Medicine, University of Yamanashi
Publication Japanese Journal of Neuropsychology: 24 (1), 40-47, 2008
Received
Accepted
Abstract The prefrontal cortex, which is critical for the temporal organization of cognitive processes, is among the last cortical regions to reach full functional maturity. Prefrontal functions therefore show an unusually long period of vulnerability in which neurons and glia are affected easily by internal and external insults. Furthermore, early frontal lesions can result in deficits not immediately apparent but predisposing to later developmental problems such as learning disabilities, attention deficit/hyperactivity disorder (ADHD), and even problems with moral judgment. To fully appreciate the implications of developmental problems in children with the frontal lobe damage, hypothesis-driven studies are needed to explore functions such as working memory or executive function during childhood, instead of sole reliance on traditional intelligence tests. Two functionally and neurally distinct cognitive selection mechanisms involve the prefrontal lobes: those based on internal representations (context dependent) and those involving exploratory processing of novel situations (context independent). We used a cognitive bias task (CBT) representing contextual reasoning to correlate lateralization with age in the frontal lobes. Young children showed context-independent responses representing right frontal lobe function, while adolescents and adults showed context-dependent responses implicating left frontal lobe function. The locus of frontal cortical control in right-handed male subjects thus shifts from right to left as cognitive contextual reasoning develops. To identify functional anatomy of context-dependent reasoning, we used technetium-99mhexamethyl-propyleneamine oxime (99mTc HM-PAO) single photon emission computed tomography (SPECT) and statistical parametric mapping (SPM99). SPECT activation occurred bilaterally in the dorsolateral prefrontal cortices and middle temporal gyri during performance of the CBT. Additionally, the left inferior frontal cortex and left fusiform gyrus showed significant activation compared with the control task. A neural network linking the temporal and prefrontal cortices participates in context-dependent reasoning.
Keywords frontal lobe function, executive function, context, developmental disorders

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