Can prepared responses be stored subcortically?
Quick voluntary responses to environmental stimuli are required of people on a daily basis. These movements have long been thought to be controlled via cortical loops involving processing of the stimulus and generation of a suitable response. Recent experiments have shown that in simple reaction time (RT) tasks, the appropriate response can be elicited much earlier (facilitated) when the "go" signal is replaced by a startling (124 dB) auditory stimulus. In the present experiment we combined a startling acoustic stimulus with an established RT paradigm that involved simple and choice RT. In a simple RT condition the prepared voluntary response was elicited at very short latencies following the startle. However, when cortical processing was required prior to responding (choice RT task), the startle did not facilitate the voluntary response, and gave rise to more movement production errors. Since movements requiring ongoing cortical processing following the stimulus are not facilitated by startle, it is unlikely that the startle facilitation is due to increased neural activation. In contrast, it appears more likely that the startle acts as an early trigger for subcortically stored prepared movements since movements that are prepared in advance can be initiated at such short latencies (<60 ms).
University of British Columbia, 210-6081 University Boulevard, BC V6T 1Z1, Vancouver, Canada.
Anthony N
AN
Carlsen
Romeo
R
Chua
J Timothy
JT
Inglis
David J
DJ
Sanderson
Ian M
IM
Franks
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001696:Biomechanical Phenomena; D002755:Choice Behavior / Q000502:physiology; D004576:Electromyography / Q000379:methods; D005246:Feedback; D005260:Female; D006801:Humans; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D013216:Reflex, Startle / Q000502:physiology*