Visual-tactile stop signal inhibition

This study investigated voluntary inhibition of programmed movements upon infrequent presentation of visual or tactile stop signals. Participants were to perform fast saccadic or manual responses to a visual or tactile target, but to cancel the response on the 25% of trials in which a stop signal of the other sensory modality was additionally presented. Reaction times were measured in each of the three experiments reported. Additionally, in two of these amplitudes of saccadic movements were collected, and event-relatedpotentials on inhibition of manual responses were recorded in the third. The data was compared with predictions made by the race model proposed by Logan & Cowan (1984). Tactile stimuli were successfully utilized both as go and as stop signals. Participants' inhibition success was related to the delay of stop signal presentation. About half of the participants resorted to strategic responding in a subconscious attempt to increase stopping success. In each experiment, the reaction times of some participants showed small violations of the race model assumptions. The saccadic amplitude data from the failed inhibition trials exhibited strongly hypometric eye movements relative to responses on go trials, and the size of this effect increased with the duration of concurrent processing of the go and stop signals. This influence of the stop processing on the go response was interpreted as a contradiction to the context-independent processing supposed by the race model. No conclusive evidence was obtained on the effects of varying the spatial position of the stop signal in the horizontal plane. Stop signal equivalents of the no-go enhancements were found in the eventrelated potentials. Their latencies and amplitudes differed greatly between successful and failed inhibition trials, but not across conditions with different stop signal timing. The effects were assumed to be a reflection of a prior decision to inhibit, rather than the manifestation of this decision.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Oldenburg

Year

2004

Author dc:creator

• Åkerfelt, Annika

• [Keine Schlagwörter von Autor/in vergeben.]

Repository record source_url

http://oops.uni-oldenburg.de/165

OAI identifier oai:identifier

oai:oops.uni-oldenburg.de:165