Detection-related Slow Potentials and Time of Day

Abstract

This chapter discusses the detection-related slow potentials and time of day. The results show that in threshold detection task the relationship between decision confidence and the late positive component (LPC) is not significantly affected by the time of day at which the task is performed. The relationship between the LPC and the time of day variable, however, appears puzzling in view of the significant circadian variation of the mean LPC values only. Apparently, the observed variations of the LPC are - to different degrees - influenced by two independently acting factors: a task-specific, decision-related factor and a non-specific state factor. The latter probably can be equated with the tonic level of alertness, fluctuating circadianly, as also evidenced in other physiological indices such as the mean total “cerebral electrical output” and mean total plasma cortisol levels. Further experimentation is needed to investigate whether there is a common factor underlying the time dependency of the early contingent negative variation (CNV) and the LPC. Both slow potentials are thought to be of an endogenous nature and to reflect higher cognitive functions. This suggests the existence of a general, non-specific circadian modulation of some aspects of cognitive processing.