Rightward Shift of Two-Channel NIRS-Defined Prefrontal Cortex Activity during Mental Arithmetic Tasks with Increasing Levels of State Anxiety

Miwa Horiuchi-Hirose,Kazuhiko Sawada

doi:10.3390/sym12040538

Miwa Horiuchi-Hirose, Kazuhiko Sawada

Open Access

https://doi.org/10.3390/sym12040538

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Abstract

This study was aimed at clarifying the effect of different levels of state anxiety caused by mental arithmetic tasks on the anxiety- and/or task performance-related activation of the frontopolar prefrontal cortex (PFC). Twenty-six healthy male subjects performed two sets of mental arithmetic tasks, which consisted of two difficulty levels. Anxiety levels were evaluated subjectively by the State–Trait Anxiety Inventory-Form JYZ (STAI). Near-infrared spectroscopy (NIRS) measurements revealed greater levels of oxyhemoglobin in the frontopolar PFC during experimental tasks. When the subjects were divided into three anxiety groups based on STAI scores, arithmetic task performance was reduced in the moderate and high state anxiety groups compared the low state anxiety group during the experimental task, but not in the control task. Increased frontopolar PFC activity during the experimental task was observed on either side in the moderate anxiety group. The laterality of frontopolar PFC activity in moderate and high state anxiety groups shifted from left to right dominance, independent of task difficulty. Our findings suggested that reduced task performance increased the difficulty of the arithmetic tasks and was involved in the state anxiety-associated rightward lateralization of the frontopolar PFC.

Highlights

The prefrontal cortex (PFC) undergoes remarkably slow maturation and is probably the last brain region to achieve cortical myelination during adolescence and adulthood [1,2]
PFC was activated by increasing the difficulty of mental arithmetic tasks and its activity shifted with increasing anxiety levels
It was unclear whether state anxiety reduced arithmetic task performance by itself in the present study

Summary

Introduction

The prefrontal cortex (PFC) undergoes remarkably slow maturation and is probably the last brain region to achieve cortical myelination during adolescence and adulthood [1,2]. The BA 10, which presents the most extensive cytoarchitectural region of the human cerebral cortex, is located on the most anterior part of the frontal lobe, comprising the rostral prefrontal (or frontopolar) cortex [7], and is involved in task complexity [8]. The PFC is known to localize to the left hemisphere for positive experiences and to the right hemisphere for negative experiences [11]. There are associations that were reported regarding the frontal activity on the left side with approach-oriented emotional states (anger or joy) and on the right side with withdrawal-oriented emotional states (fear or sadness) [13,14]. The relatively left-dominant frontal activity reflected greater motivation approach and positive effects, and the relatively right-dominant frontal activity reflected greater motivation withdrawal and negative effects [15]

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