Cortical Response to a Tactile Stimulus During Attention, Mental Arithmetic and Free Associations

Attention to a stimulus appears to be associated with amplitude fluctuations in 100‐msec or later components of the cortical compound evoked potential (CEP). In this study, changes in amplitude and latency of the CEP to the same tactile stimulus were investigated under three conditions: attention, free associations, and mental arithmetic. In the attention condition S s were asked to estimate varying time intervals between stimuli on a 2‐ to 6‐sec scale. S s were 12 pairs of twins. It was found that the amplitudes of two negative electrocortical potentials were greater when S s were estimating lengths of time intervals between stimuli than during free association or mental arithmetic. Peak latency of the second negative potential was greater in attention than in the other two conditions. Free association CEPs were distinguished by the incidence of a bursts. The results support the hypothesis that attention is associated with certain parameters of the electrocortical response and suggest which aspects of the electrocortical response are most likely to be related to attention.