Abstract
Upon early sensory deprivation, the remaining modalities often exhibit cross-modal reorganization, such as primary auditory cortex (PAC) recruitment for visual motion processing in early deafness (ED). Previous studies of compensatory plasticity in ED individuals have given less attention to tactile motion processing. In the current study, we aimed to examine the effects of early auditory deprivation on tactile motion processing. We simulated four directions of tactile motion on each participant’s right index finger and characterized their tactile motion responses and directional-tuning profiles using population receptive field analysis. Similar tactile motion responses were found within primary (SI) and secondary (SII) somatosensory cortices between ED and hearing control groups, whereas ED individuals showed a reduced proportion of voxels with directionally tuned responses in SI contralateral to stimulation. There were also significant but minimal responses to tactile motion within PAC for both groups. While early deaf individuals show significantly larger recruitment of right posterior superior temporal sulcus (pSTS) region upon tactile motion stimulation, there was no evidence of enhanced directional tuning. Greater recruitment of right pSTS region is consistent with prior studies reporting reorganization of multimodal areas due to sensory deprivation. The absence of increased directional tuning within the right pSTS region may suggest a more distributed population of neurons dedicated to processing tactile spatial information as a consequence of early auditory deprivation.
Highlights
Individuals affected by early sensory deprivation often display enhanced perceptual sensitivities for the remaining modalities
Activation, we calculated the percentage of voxels that showed significant BOLD activity within our functionally defined posterior superior temporal sulcus (pSTS) region and anatomically defined (SI/HA, SII, primary auditory cortex (PAC), pSTS) region of interest (ROI) for tactile motion simulation vs. baseline periods
We characterized the directional tuning of voxels within each ROI using a modified population receptive field (pRF) model based on the four directions of tactile motion used in this study
Summary
Individuals affected by early sensory deprivation often display enhanced perceptual sensitivities for the remaining modalities. Visual motion detection (Shiell et al, 2014) and visual motion direction discrimination (Hauthal et al, 2013) appear to be superior in early deaf (ED) participants compared to normal hearing (NH). These behavioral changes are typically accompanied by cross-modal reorganization, where brain areas deprived of default sensory input respond to input from the remaining modalities. Other studies report similar crossmodal reorganization of auditory cortex in ED for processing vibrotactile stimuli (Levänen and Hamdorf, 2001; Auer et al, 2007) and during touches to the face (Karns et al, 2012). Specificity toward vibrotactile frequency demonstrated in the above findings provides evidence of maintained auditory cortex function in ED adults for haptic rather than auditory sensory input
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