Does a warning signal accelerate the processing of sensory information? Evidence from recognition potential responses to high and low frequency words

Electrophysiological and behavioral data were obtained in 12 subjects who detected valid words in a background stream of random letter strings. Behavioral reaction time (RT) showed significant effects of warning signal presentation and the frequency of word usage in printed literature. Cross-correlation functions were used to estimate delays of electrophysiological responses. The critical response was the recognition potential (RP). The RP is a response of the brain that occurs when a person views recognizable images, such as words, pictures, or faces. Its latency is usually less than 300 ms. Both the RP and longer latency activity occurring at approximately 400-600 ms were delayed more for low than for high frequency words. The longer latency responses showed shorter delay if a warning signal was presented, but the RP did not. The results supported the idea that a non-informative warning signal decreases RT by altering response-related processes without facilitating sensory processes. (C) 2001 Elsevier Science B.V. All rights reserved.