TACTILE SALIENCE INFLUENCES EXTINCTION

We delivered unilateral (left or right) or bilateral tactile stimuli t o hands or feet of right-brain-damaged patients, six with tactile exti nction and two without. Stimuli were simple touches or sliding stimuli directed proximo-distally (e.g., toward the fingers) or disto-proxima lly (e.g., toward the forearm). Patients were asked to report number t 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 report ing single stimuli, omitted left stimuli under double-stimuli conditio ns. However, the number of left stimuli detected consciously was relat ed to an imbalance of the salience between left and right stimuli. Mor eover, in three patients the extinguished, left-sided stimulus, even w hen inaccessible to consciousness, influenced implicitly the report of the features of the right stimulus. Thus, the relationships between l eft and right stimuli can modulate both overtly and covertly the perfo rmance of extinction patients.