2/6/2025 | 11:00 AM - 1:00 PM | Regency A

Cross-modal brain plasticity in haptic perception, kinesthetics & spatial navigation: Profound interhemispheric asymmetry

Author(s)

Lora Likova | Smith-Kettlewell Eye Research Institute
Kristyo Mineff | Smith-Kettlwell Eye Research Institute
Zhangziyi Zhang | Smith-Kettlewell Eye Research Institute
Michael Liang | Smith-Kettlewell Eye Research Institute
Christopher Tyler | Smith-Kettlewell Eye Research Institute

Abstract

Introduction: The occipito-temporal cortex incorporates a pivotal brain area traditionally associated with visual motion processing, area hMT+. Previously considered exclusively visual, its role has been expanded by recent findings to include sensitivity to visual tasks beyond motion, such as static body parts, handedness, and tool usage. This leads to the question of how this extended visual functionality is reorganized in the absence of vision, particularly for non-visual self-produced motion like haptic perception or kinesthetically-guided body-motion during navigation?

Methods: A group of totally blind subjects underwent the Cognitive-Kinesthetic Memory-Drawing Training (Likova, 2012), tailored for spatial navigation, using raised-line tactile maps. The whole brain was scanned before and after the training in a Siemens 3T Prisma scanner while the navigational maps were (i) haptically explored with left hand to be memorized (30 s); after  a 20 s rest period, the maps were (ii) drawn-from-haptic-memory based on kinesthetic feedback only using a stylus with the opposite hand (30 s). Before and after training, a custom Virtual Reality (VR) system was used to assess the transfer of training effect to the participants’ navigational abilities. 

Results: Both non-visual tasks strongly activated hMT+ despite the lack of any vision or visual motion. Moreover, our paradigm revealed an unsuspected interhemispheric functional asymmetry in the occipitotemporal cortex. The left-hand haptic memory encoding task activated the right-hemisphere hMT+ only but failed to do so in its ipsilateral hemisphere. In contrast, the right-hand kinesthetic drawing-from-haptic-memory task strongly activated hMT+ bilaterally. Further post-training analyses revealed for the first time a large-scale massive brain reorganization in the blind forming previously unknown clusters of occipitotemporal areas neighboring hMT+, which, expressed the same left/right asymmetry as hMT+ per se. The profoundly asymmetric pattern of hMT+ thus spread across neighboring visual areas despite their well-known distinct functionality in the sighted, turning them instead into large homogeneous clusters with asymmetric responses in the blind.

Granger Causal connectivity analysis was run pre & post training to investigate the brain reorganization at network level – including all of the areas of each cluster, as well as the classic motor, somatosensory and memory areas.  Remarkably, inputs to hMT+ derived entirely from the frontal and prefrontal cortex, while outputs from hMT+ went entirely to posterior cortex, including key areas of the navigational network. The VR assessments demonstrated highly significant improvement in both speed and precision of the navigational performance post-training, confirming transfer of learning effects.

Conclusions: This study provides multifaceted insights into non-visual functionality of the visual-motion complex, its novel interhemispheric asymmetries, and their implications for functional brain architecture and learning-induced plasticity. Furthermore, the results revealed for the first time the emergence of training-driven functional-homogenization of occipitotemporal clusters surrounding hMT+, highlighting a remarkable form of cross-modal reorganization in the blind. The VR assessments confirmed the behavioral relevance of these learning effects and their transfer from the hand-scale to full body-scale of navigation. These findings advance our understanding of neuroplasticity and sensory compensation, demonstrating how the brain adapts to the absence of vision to optimize spatial navigation, haptic perception and kinesthetics.