Examining tactile spatial remapping using transcranial magnetic stimulation
Date: 2012-06-21 09:00 AM – 10:30 AM
Last modified: 2012-04-24
Abstract
Previous research has provided evidence for two stages of tactile processing (e.g. Groh & Sparks, 1996; Azañon & Soto-Faraco, 2008). First, tactile stimuli are represented in a somatotopic representation that does not take into account body position in space, followed by a representation of body position in external space (body posture representation, see Medina & Coslett, 2010). In order to explore potential functional and neural dissociations between these two stages of processing, we presented eight participants with TMS before and after a tactile temporal order judgment (TOJ) task (see Yamamoto & Kitazawa, 2001). Participants were tested with their hands crossed and uncrossed before and after 20 minutes of 1 Hz repetitive TMS (rTMS). Stimulation occurred at the left anterior intraparietal sulcus (aIPS, somatotopic representation) or left Brodmann Area 5 (BA5, body posture) during two separate sessions. We predicted that left aIPS TMS would affect a somatotopic representation of the body, and would disrupt performance in both the uncrossed and crossed conditions. However, we predicted that TMS of body posture areas (BA5) would disrupt mechanisms for updating limb position with the hands crossed, resulting in a paradoxical improvement in performance after TMS. Using thresholds derived from adaptive staircase procedures, we found that left aIPS TMS disrupted performance in the uncrossed condition. However, left BA5 TMS resulted in a significant improvement in performance with the hands crossed. We discuss these results with reference to potential dissociations of the traditional body schema.
References
Azanon, E., & Soto-Faraco, S. (2008). Changing reference frames during the encoding of tactile events. Current Biology, 18, 1044–1049.
Groh, J. M., & Sparks, D. L. (1996). Saccades to somatosensory targets. 1. Behavioral characteristics. Journal of Neurophysiology, 75, 412–427.
Medina, J. & Coslett, H.B. (2010). From maps to form to space: Touch and the body schema. Neuropsychologia, 48, 645-654.
Yamamoto, S., & Kitazawa, S. (2001). Reversal of subjective temporal order due to arm crossing. Nature Neuroscience, 4, 759–765.
Groh, J. M., & Sparks, D. L. (1996). Saccades to somatosensory targets. 1. Behavioral characteristics. Journal of Neurophysiology, 75, 412–427.
Medina, J. & Coslett, H.B. (2010). From maps to form to space: Touch and the body schema. Neuropsychologia, 48, 645-654.
Yamamoto, S., & Kitazawa, S. (2001). Reversal of subjective temporal order due to arm crossing. Nature Neuroscience, 4, 759–765.