Vibrotactile activation of the auditory cortices in deaf versus hearing adults

Abstract

Neuroplastic changes in auditory cortex as a result of lifelong perceptual experience were investigated. Adults with early-onset deafness and long-term hearing aid experience were hypothesized to have undergone auditory cortex plasticity due to somatosensory stimulation. Vibrations were presented on the hand of deaf and normal-hearing participants during functional MRI. Vibration stimuli were derived from speech or were a fixed frequency. Higher, more widespread activity was observed within auditory cortical regions of the deaf participants for both stimulus types. Life-long somatosensory stimulation due to hearing aid use could explain the greater activity observed with deaf participants.

Figure 1

Displays the significant activations from fixed-effects analysis in SPM2 with the False Discovery Rate set to p = .001 and a minimum of 10 voxels per cluster. The left column displays the results from the F0 Speech condition and the right column displays the results from the FF condition. The top row of images displays the NH participants. On the left, SPMs for the t-contrasts FOSPEECH > REST (ORANGE t threshold = 3.82) are displayed on both a rendered cortical volume and axial slices. The main axial slice is at Z = 6 in MNI space and is chosen for a good view through Heschl’s gyrus. The inset partial axial slice has crosshairs that intersect at X = -45, Y = -36, and Z = 12 in MNI space. These co-ordinates are at the peak voxel for the vibrotactile-auditory co-activation in Shurmann et al.[4]. On the right, SPMs for the t-contrasts FF > REST (RED t threshold = 4.61) are displayed on both a rendered cortical volume and axial slices. The middle row of images displays the same contrasts for the deaf participants (FOSPEECH > REST- GREEN, t threshold = 3.79; FF > REST-CYAN, t threshold = 3.90). The last row displays the results of the contrast testing explicitly where Deaf > NH in each of the stimulus conditions (FOSPEECH- YELLOW, t threshold = 4.49; FF-PURPLE, t threshold = 4.51). The inset image at the top center of the Figure displays the two axial slices with the primary auditory cortex (area TE 1.0 as defined by Morosan et al.,[24]) shown in BLUE.