Intact tactile detection yet biased tactile localization in a hand-centered frame of reference: A case study

• Authors: Yuqi Liu, Georgetown University; Alexandria O'Neal, University of Delaware; Robert D. Rafal, University of Delaware; Jared Medina, Emory University
• Journal Title: Neuropsychologia
• Volume: Volume 147
• Publisher: Elsevier | 2020-10-01, Pages 107585-None
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1016/j.neuropsychologia.2020.107585
• Subjects: Biology, Neuroscience; Biology, Anatomy
• Keywords: tactile detection; tactile localization; somatotopic reference frame; external reference frame; proprioception

Abstract

We examined the performance of an individual with subcortical damage, but an intact somatosensory thalamocortical pathway, to examine the functional architecture of tactile detection and tactile localization processes. Consistent with the intact somatosensory thalamocortical pathway, tactile detection on the contralesional hand was well within the normal range. Despite intact detection, the individual demonstrated substantial localization biases. Across all localization experiments, he consistently localized tactile stimuli to the left side in space relative to the long axis of his hand. This was observed when the contralesional hand was palm up, palm down, rotated 90° relative to the trunk, and when making verbal responses. Furthermore, control experiments demonstrated that this response pattern was unlikely a motor response error. These findings indicate that tactile localization on the body is influenced by proprioceptive information specifically in a hand-centered frame of reference. Furthermore, this also provides evidence that aspects of tactile localization are mediated by pathways outside of the primary somatosensory thalamocortical pathway.