Brain structure & function
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Using optimized voxel-based morphometry, we performed grey matter density analyses on 59 age-, sex- and intelligence-matched young adults with three distinct, progressive levels of musical training intensity or expertise. Structural brain adaptations in musicians have been repeatedly demonstrated in areas involved in auditory perception and motor skills. However, musical activities are not confined to auditory perception and motor performance, but are entangled with higher-order cognitive processes. ⋯ Grey matter density increased with expertise in areas known for their involvement in higher-order cognitive processing: right fusiform gyrus (visual pattern recognition), right mid orbital gyrus (tonal sensitivity), left inferior frontal gyrus (syntactic processing, executive function, working memory), left intraparietal sulcus (visuo-motor coordination) and bilateral posterior cerebellar Crus II (executive function, working memory) and in auditory processing: left Heschl's gyrus. Conversely, grey matter density decreased with expertise in bilateral perirolandic and striatal areas that are related to sensorimotor function, possibly reflecting high automation of motor skills. Moreover, a multiple regression analysis evidenced that grey matter density in the right mid orbital area and the inferior frontal gyrus predicted accuracy in detecting fine-grained incongruities in tonal music.
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Determining the normal developmental trajectory of individual GABAergic components in the prefrontal cortex (PFC) during the adolescent transition period is critical because local GABAergic interneurons are thought to play an important role in the functional maturation of cognitive control that occurs in this developmental window. Based on the expression of calcium-binding proteins, three distinctive subtypes of interneurons have been identified in the PFC: parvalbumin (PV)-, calretinin (CR)-, and calbindin (CB)-positive cells. Using biochemical and histochemical measures, we found that the protein level of PV is lowest in juveniles [postnatal days (PD) 25-35] and increases during adolescence (PD 45-55) to levels similar to those observed in adulthood (PD 65-75). ⋯ At the synaptic level, our electrophysiological data revealed that a developmental facilitation of spontaneous glutamatergic synaptic inputs onto PV-positive/fast-spiking interneurons parallels the increase in prefrontal PV signal during the periadolescent transition. In contrast, no age-dependent changes in glutamatergic transmission were observed in PV-negative/non fast-spiking interneurons. Together, these findings emphasize that GABAergic inhibitory interneurons in the PFC undergo a dynamic, cell type-specific remodeling during adolescence and provide a developmental framework for understanding alterations in GABAergic circuits that occur in psychiatric disorders.