Tactile salience influences extinction

We delivered unilateral (left or right) or bilateral tactile stimuli to hands or feet of right-brain-damaged patients, six with tactile extinction and two without. Stimuli were simple touches or sliding stimuli directed proximo-distally (e.g., toward the fingers) or disto-proximally (e.g., toward the forearm). Patients were asked to report number (one or two), type (touch or slide), and direction (proximo-distally or disto-proximally) of the experimental stimuli. Nonextinction patients performed perfectly. Extinction patients, although accurate in reporting single stimuli, omitted left stimuli under double-stimuli conditions. However, the number of left stimuli detected consciously was related to an imbalance of the salience between left and right stimuli. Moreover, in three patients the extinguished, left-sided stimulus, even when inaccessible to consciousness, influenced implicitly the report of the features of the right stimulus. Thus, the relationships between left and right stimuli can modulate both overtly and covertly the performance of extinction patients.