Friday, December 11, 2015

Exercise enhances frontal brain lateralization characteristic of younger brains.

As we age beyond 40 years or so, mental tasks that require attention, problem solving, decision-making and other types of high-level thinking become less localized to one of our frontal lobes and expand to engage both hemispheres of our prefrontal cortex. This represents a general reorganization and weakening of our brains' function with age. Hyodo et. al. show in a group of Japanese men with no signs of dementia, between between 64 and 75 years old, that increased aerobic fitness correlates with the increased lateralization during task performance characteristic of younger brains. Here are their summaries:

• Association among fitness, brain activation, and cognitive function was examined. 
• Frontal laterality during Stroop task in older men was assessed by fNIRS. 
• We found the association between ventilatory threshold and Stroop performance. 
• The association was mediated by the lateralized prefrontal activation.
Previous studies have shown that higher aerobic fitness is related to higher cognitive function and higher task-related prefrontal activation in older adults. However, a holistic picture of these factors has yet to be presented. As a typical age-related change of brain activation, less lateralized activity in the prefrontal cortex during cognitive tasks has been observed in various neuroimaging studies. Thus, this study aimed to reveal the relationship between aerobic fitness, cognitive function, and frontal lateralization. Sixty male older adults each performed a submaximal incremental exercise test to determine their oxygen intake at ventilatory threshold (VT) in order to index their aerobic fitness. They performed a color–word Stroop task while prefrontal activation was monitored using functional near infrared spectroscopy. As an index of cognitive function, Stroop interference time was analyzed. Partial correlation analyses revealed significant correlations among higher VT, shorter Stroop interference time and greater left-lateralized dorsolateral prefrontal cortex (DLPFC) activation when adjusting for education. Moreover, mediation analyses showed that left-lateralized DLPFC activation significantly mediated the association between VT and Stroop interference time. These results suggest that higher aerobic fitness is associated with cognitive function via lateralized frontal activation in older adults.

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