Poster B98, Sunday, March 25, 8:00-10:00 am, Exhibit Hall C
Exploring Categorical and Functional Boundaries of Tactile Perception Using Somatosensory Mismatch Responses
Guannan Shen1, Peter J. Marshall1; 1Department of Psychology, Temple University
The current study examines categorical and functional boundaries in somatosensory perception, and explores two potential influences on tactile spatial discrimination: discrete body part representations and motor experiences. The mismatch negativity (MMN), an index of early automatic sensory discrimination, has been shown to be sensitive to categorical boundaries and language experience in the auditory modality. Here, we recorded somatosensory MMN (sMMN) using a tactile oddball paradigm, and compared sMMN elicited by within- and across-boundary oddball pairs. We first leveraged a categorical segmentation of tactile space at the wrist, and presented two pairs of tactile oddball stimuli with equal spatial distances, either across the wrist or within the forearm. Results showed that sMMN amplitude elicited by stimuli across the body part boundary was significantly greater than for sites within the forearm, suggesting a categorical effect on tactile perception at the early pre-attentive stage of somatosensory processing. We then examined sMMN elicited by an oddball contrast of the 3rd finger / thumb, which was significantly larger than for the 3rd / 5th fingers. We suggest this indicates a functional boundary effect on tactile perception of finger stimulation as a result of motor experiences (e.g., grasping, picking up objects). These findings demonstrate that the sMMN is a useful neurophysiological index of pre-attentive processing of somatosensory spatial discrimination, sensitive to both categorical and motor-related functional boundary effects. This paradigm can be potentially used in studying the development of somatosensory representations and body maps in early infancy.
Topic Area: PERCEPTION & ACTION: Other