Lateralized readiness potential elicited by undetected visual stimuli.
Visual stimuli undetected by normal subjects as a result of masking procedures can nonetheless activate response preparation in motor areas and yield a motor response. An unanswered question is whether the same holds for undetected subliminal stimuli that are not responded to. To answer this question, in this study normal subjects were tested on a simple visual reaction time task with stimuli above, at, or below the psychophysical threshold while the lateralized readiness potential (LRP), i.e. an electrophysiological correlate of premotor activation in the primary motor cortex, was computed. We found a reliable LRP not only for suprathreshold stimuli but also for subthreshold stimuli to which subjects did not respond. The main thrust of this study is that it provides evidence that activation of the motor cortex occurs even with subthreshold visual stimuli and without an overt response.
Minelli
Alessandra
A
Department of Neurological and Vision Sciences, Section of Human Physiology, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy.
Marzi
Carlo Alberto
CA
Girelli
Massimo
M
D003265:Contingent Negative Variation / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008029:Lighting; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D011601:Psychophysics / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D012018:Reflex / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*