Sequence of preparatory set for response movement

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.

Effects of foreperiod on response latency of different movement patterns

In an analysis of the influence of the preparatory process on motor output by measuring the EMG latencies of synergic muscles for elbow flexion and forearm supination the optimum foreperiod was between 2.0 and 2.2 sec., and a specific effect on movement pattern was not observed. However, reduction in EMG-RTs was larger in forearm supination than in elbow flexion. Those results reconfirmed previous reports.

Effect of reaction time condition on EMG activities of the biceps brachii muscle in elbow flexion and forearm supination

Under simple- and choice-RT conditions, the biceps brachii muscle was examined in 8 healthy male subjects to determine how the temporal and spatial characteristics of elbow flexion and forearm supination differed at the initial phase of EMG activity and whether preparation or the presence of response uncertainty influenced the EMG outputs of the two movements. In the simple-RT condition, RT of supination was significantly faster than that of flexion but EMG activity of supination was less than that of flexion. In contrast, in the choice-RT condition, RT of flexion was significantly faster than that of supination but EMG activity of flexion was significantly reduced compared to supination. These findings indicate that advanced preparation or motor set facilitates the differentiation of RTs and EMG activities of the response movements and that response uncertainty causes a significant change in the temporal and spatial specificity of both elbow flexion and forearm supination.