The right hand knows what the left hand is feeling

Abstract

The mislocalization profile, describing incorrect localization of faint tactile stimuli to different regions of the body, has been shown to provide insight into the processing of tactile stimuli. Interhemispheric somatosensory processing was examined in 15 subjects by studying the interference of left-hand stimulation on right-hand perception. In different conditions supra-threshold interference stimuli were applied to the left thumb or little finger either 200 or 500 ms prior to the application of a test stimulus on the right hand. Data show that interference stimuli applied to the left hand massively altered localization responses for stimuli applied to the right side. Stimulating the left thumb yielded an increased number of mislocalizations to the right thumb. Similarly, stimulating the left little finger caused a shift in localization responses towards the right ring finger. Results support the hypothesis that interaction of somatosensory information originating from different sides of the body follows a somatotopic organization.

On the minimization of task switch costs following long-term training

“…This is consistent with some previous findings reporting reduced switch costs when S-R mappings are lateralized across hands (Bradshaw, Nicholls, & Rogers, 1998; but see Charron, Collin, &Braun, 1996, andNefs, Kappers, &Koenderink, 2005). The finding that interference is not completely eliminated under conditions of intermanual task switching (e.g., Braun, Hess, Burkhardt, Wühle, & Preissl, 2005;Thut et al, 1996) may be due to interhemispheric connections (Diedrichsen, Hazeltine, Nurss, & Ivry, 2003), such as the callosal links between the hand representations in the two hemispheres (Wahl et al, 2007).…”

Finger force perception during ipsilateral and contralateral force matching tasks

“…Furthermore, accumulated data have demonstrated that afferent inputs from one hand ascend to both ipsilateral and contralateral somatosensory cortices (Wegner et al 2000;Simoes et al 2002;Nihashi et al 2005;Blatow et al 2007). As such, tactile stimuli applied to fingertips in one hand are reported to be identified and localized in the contralateral corresponding fingertips (Braun et al 2005). This phenomenon of bilateral projections of unilateral hand afferent inputs could also account for a previous report that patients with surgical disconnection of the cerebral hemispheres are able to estimate accurately heaviness of the weight lifted by the contralateral hand (Gandevia 1978).…”

The Hand and the Ipsilateral Primary Somatosensory Cortex: Figure 1.

“…Primates' high capacity for sophisticated bimanual tasks indicates that fusion of information from the hands occurs within the CNS and possibly underlies essential behaviors (Tommerdahl et al, 2006). Psychophysical studies have demonstrated that finger stimulation to one hand can alter perception at the opposite hand (Harris et al, 2001;Braun et al, 2005). These findings suggest a functional role for the fusion of somatosensory information.…”