Abstract
Sustained attention is fundamental for cognition and when impaired, impacts negatively on important contemporary living skills. Degradation in sustained attention is characterized by the time-on-task (TOT) effect, which manifests as a gradual increase in reaction time (RT). The TOT effect is accompanied by changes in relative brain activity patterns in attention-related areas, most noticeably in the prefrontal cortex (PFC) and the right parietal areas. However, activity changes in task-relevant motor structures have not been confirmed to date. This article describes an investigation of such motor-related activity changes as measured with 1) the time course of corticospinal excitability (CSE) through single-pulse transcranial magnetic stimulation; and 2) the changes in activity of premotor (PMC), primary motor (M1), PFC, and right parietal areas by means of near-infrared spectroscopy, during a sustained attention RT task exhibiting the TOT effect. Our results corroborate established findings such as a significant increase (P < 0.05) in lateral prefrontal and right parietal areas activity after the emergence of the TOT effect but also reveal adaptations in the form of motor activity changes--in particular, a significant increase in CSE (P < 0.01) and in primary motor area (M1) activity (P < 0.05).
Highlights
Sustained attention describes a fundamental aspect of cognitive processes vital for the successful execution of many activities of daily living, for example as in driving, or crossing a busy street
The study was split into 2 experiments because of the difficulties in investigating corticospinal excitability (CSE) by transcranial magnetic stimulation (TMS) concurrently with near-infrared spectroscopy (NIRS), for example, the placement of the NIRS optodes interferes physically with the placement of the coil necessitating an increase in the distance between the TMS coil and the scalp
Further it has been demonstrated that TMS can induce artifacts in NIRS measurements when performed over the same area (Näsi et al 2011)
Summary
Sustained attention describes a fundamental aspect of cognitive processes vital for the successful execution of many activities of daily living, for example as in driving, or crossing a busy street. Attention resources are finite and a gradual decrease in attention across time—the so-called time-on-task (TOT) effect—usually arises from tasks requiring sustained attention. The TOT effect manifests behaviorally as an observable increase in reaction time (RT) over time and can have serious consequences in terms of impaired performance in everyday tasks. Other important areas where attention capacity has been identified as relevant include the clinical domain where patients suffering from attention deficit and hyperactivity disorder, can see their goal-directed behaviors disrupted by attentional lapses (Reimer et al 2005). Investigating the neural bases of sustained attention is key to a deeper understanding of this vital cognitive property
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