Involvement of human primary somatosensory cortex in vibrotactile detection depends on task demand

Studies on monkeys have suggested that the primary somatosensory cortex is responsible for discriminating between different vibrations on the fingertips, but not just for detecting these vibrations. However, similar studies in humans suggest that the somatosensory cortex is required both for detecting and discriminating between tactile stimuli. We used magnetic brain stimulation to interfere with human somatosensory cortex while healthy volunteers detected and discriminated between vibrations applied to their fingertips. We found that the somatosensory cortex is required for keeping vibrotactile stimuli in memory for short periods of time and for comparing two vibrotactile stimuli, but is not required merely for detecting vibrotactile stimulation. This suggests that human primary somatosensory cortex is not always needed for vibrotactile detection.