Neurophysiological correlates of performance feedback in Blindsight - an ERP study
Sänger, J., and Stoerig, P.
Institut für Experimentelle Biologische Psychologie, Heinrich-Heine-Universität, Düsseldorf
Lesions of the primary visual cortex cause homonymous blindness in the contralateral hemifield. However, patients with fields of cortical blindness may respond to visual stimuli they do not consciously see ('blindsight'). As blindsight improves with practise, we investigated the impact of trial-by-trial feedback upon signal detection performance and how this is processed in the EEG.
Two hemianope patients performed a signal detection task, where half of the trials were followed by a visual feedback to signal response correctness. Although patients reported no stimulus awareness, blindsight performance improved with feedback.
Target-related ERPs show differential modulation of the ipsi- and contralesional N1. An enhanced response-related negativity for correct responses suggests that stimulus and response information was integrated, even in the absence of stimulus awareness. Possibly by virtue of being relatively rare, the error feedback initiated a pronounced P3-like potential which can be associated with an improvement of the implicit performance.