Effects of Information-Processing Demands on Physiological Response Patterns

Abstract

The present study investigated the effects of increased attentional and encoding/rehearsal demands on a number of physiological measures. Encoding/rehearsal demands were varied by manipulating the number of letters (1, 3, or 5) comprising a briefly presented set that the subject was instructed to encode, retain, and, 5 s later, compare with a single test letter. Attentional demands were varied by presenting the subject with a cue stimulus (the numeral 1, 3, or 5) 5s prior to the presentation of the letter set, informing the subject of the number of letters contained therein. The physiological measures recorded were heart rate, eyeblinks, “probe-evoked” potentials sampled from the intervals preceding and following the letter set, and “task-evoked” potentials elicited by the cue, memory set, and test stimuli. Unique patterns of physiological activity occurred in the intervals preceding and following the memory set. In the interval preceding the memory set, where attentional demands were varied by set size, probe ERP P1-N1 amplitude increased with set size. In the subsequent interval, where encoding and rehearsal demands were varied, probe ERP N1-P2 amplitude declined with increasing set size. There was also evidence for interval and set-size effects on heart rate, blink rate, and task ERPs. These results have implications for multiple-resource theories of attention.