Metamodal Coupling of Vibrotactile and Auditory Speech Processing Systems Through Matched Stimulus Representations

Abstract

SummaryIt has been postulated the brain is organized by “metamodal”, sensory-independent cortical modules implementing particular computations. Yet, evidence for this theory has been variable. We hypothesized that effective metamodal engagement requires not only an abstract, “cognitive” congruence between cross-modal stimuli but also a congruence between neural representations. To test this hypothesis, we trained participants to recognize vibrotactile versions of auditory words using two encoding schemes. The vocoded approach preserved the dynamics and representational similarities of auditory speech while the token-based approach used an abstract phoneme-based code. Although both groups learned the vibrotactile word recognition task, only in the vocoded group did trained vibrotactile stimuli recruit the auditory speech network and lead to increased coupling between somatosensory and auditory speech areas. In contrast, the token-based encoding appeared to rely on paired-associate learning. Thus, matching neural input representations is a critical factor for assessing and leveraging the metamodal potential of cortical modules.

Evidence for a Spoken Word Lexicon in the Auditory Ventral Stream

“…We used whole-head echo-planar imaging (EPI) sequences (flip angle = 70°, echo time [TE] = 35 ms, field of view [FOV] = 205 mm, 102 × 102 matrix) with a 64-channel head coil. Building off other auditory localizer ( Damera et al, 2021 ) and RA paradigms ( Chevillet et al, 2013 ), a slow (repetition time [TR] = 9,000 ms, acquisition time [TA] = 1,680 ms) and a fast (TR = 3,360 ms, TA = 1,680 ms) clustered acquisition paradigm were used for the auditory localizer and RA scans, respectively. Fifty-four axial slices were acquired in descending order (thickness = 1.8 mm, 0.18 mm gap; in-plane resolution = 2.0 × 2.0 mm 2 ).…”

Evidence for a Spoken Word Lexicon in the Auditory Ventral Stream

“…We used whole-head echo-planar imaging sequences (flip angle = 70°, TE = 35 ms, FOV = 205mm, 102x102 matrix) with a 64-channel head coil. Building off previous auditory localizer 65 and RA paradigms in our lab 46 , a slow (TR = 9000 ms, TA = 1680 ms) and a fast (TR = 3360 ms, TA = 1680 ms) clustered acquisition paradigm were used for the auditory localizer and RA scans, respectively. 54 axial slices were acquired in descending order (thickness = 1.8 mm, 0.18 mm gap; in-plane resolution = 2.0 x 2.0 mm 2 ).…”