Abstract
PurposeCognitive processing generally deteriorates as people age. Recent neuroimaging studies have shown that the prefrontal cortex (PFC) is involved in human-specific behavior, such as preparing for future actions and prospective memory; hence, the PFC may be voluntarily activated even during the “resting” condition that precedes task execution. The purpose of the present study was to investigate changes in voluntary pre-task activation as a result of aging using a paradigm that includes a longer intertrial interval (e.g., 30 sec) than has been used in previous studies.MethodsA total of 120 cognitively normal adults (young: 60, old: 60) participated in this near-infrared spectroscopy (NIRS) study. All subjects performed 6 repetitions of the working memory task, which included a 30 sec resting period and a 28.8 sec task period. The resting period was divided into baseline and pre-task (preT) periods, and the task period was divided into early easy task (eT) and late difficult task (dT) periods. We then normalized the data, analyzed the magnitude of task-related NIRS responses in each period and compared the results between groups using an analysis of variance test.ResultsStatistical analyses revealed a significant interaction between group × optode location × period, in which hemodynamic responses in the PFC during the preT period were smaller in the elderly in than young adults. By contrast, during the task period, the hemodynamic responses were higher in the lateral PFC in the elderly than in young adults. Spearman's rank correlation analysis showed a positive correlation between hemodynamic changes during the preT period in the PFC and correct answer ratios in both groups.ConclusionsThese findings suggest that more pre-task activation in the anterior PFC is related to better cognitive performance in humans. Thus, a reduction in this activation might partly explain cognitive decline in the elderly.
Highlights
The anterior prefrontal cortex (PFC) is involved in humanspecific behavior, such as preparing for future information processing [1,2,3], preparing for future actions [4], thinking about the future [5], and prospective memory [6,7,8]
We examined the positions of the emitter and detector probes of the current near-infrared spectroscopy (NIRS) system in some subjects using MRI (Hitachi Medical Co., MRP-7000AD, 0.3T) and confirmed that the photodiodes in the center of the bottom row were located on the rostrum of the PFC (Fig. 1B, 1C)
To examine brain hemodynamic changes in the PFC region covered by the NIRS device, we evaluated D[oxygenated hemoglobin (oxy-Hb)] changes quantitatively throughout the whole experimental session on 16 channels
Summary
The anterior prefrontal cortex (PFC) is involved in humanspecific behavior, such as preparing for future information processing [1,2,3], preparing for future actions [4], thinking about the future [5], and prospective memory [6,7,8]. Exploiting the strength of EEG (i.e., high time resolution), Berchicci et al demonstrated that older subjects prepared for the action with greater anticipation and higher cost, as indicated by an earlier latency onset and amplitude of movement, related to cortical potentials in the PFC [12,13]. These previous studies examined brain activity using a
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