Poster D98, Monday, March 26, 8:00-10:00 am, Exhibit Hall C
Biased tactile localization with an intact somatosensory system: A case study
Yuqi Liu1, Alexandria O'Neal1, Jared Medina; 1University of Delaware
We report the performance of an individual with a small, subcortical infarct in the right hemisphere that damaged white matter tracts including the superior and anterior corona radiata, while leaving both thalamus, primary somatosensory cortex and related somatosensory pathways intact. Using a staircase task, his tactile detection ability on both hands was well within the range of normal controls. However, he demonstrated a peculiar deficit in tactile localization on his contralesional (left) hand. When asked to localize suprathreshold tactile stimuli presented to his contralesional hand (by pointing with his ipsilesional hand, see Rapp, Hendel & Medina, 2002), he accurately detected all stimuli. However, he consistently mislocalized tactile stimuli to the left side of his hand (ulnar bias with palm down, radial bias with palm up). This pattern was highly consistent over multiple sessions, 90° hand rotation, and using different response modalities. Furthermore, this bias was specific to contralesional tactile localization, as he was normal at localizing ipsilesional tactile stimuli, visual stimuli on hand outlines, general pointing to targets, and did not demonstrate this bias in a finger movement task. Given normal tactile detection and intact somatosensory regions, along with highly impaired tactile localization, this suggests the role of additional pathways for localizing touch on the body. Furthermore, this bias was not somatotopic, providing evidence for processing tactile localization in a hand-centered, external frame of reference.
Topic Area: PERCEPTION & ACTION: Other