A Positron Emission Tomographic Study of Auditory Localization in the Congenitally Blind

TLDR

The study aimed to assess functional connectivity between auditory and posterior parietal regions during auditory localization in sighted and congenitally blind participants via inter‑regional correlation analysis of PET rCBF data. PET was used to measure regional cerebral blood flow while subjects performed auditory localization tasks with spectrally and binaurally cued sounds delivered through headphones. Results showed that both groups activated posterior parietal cortex, but blind participants additionally engaged right occipital association areas, and inter‑regional correlation analysis revealed a positive coupling between right posterior parietal and right occipital cortex in the blind, whereas sighted subjects exhibited negative correlations, indicating cross‑modal plasticity in the blind.

Abstract

We have used positron emission tomography (PET) to measure regional cerebral blood flow (rCBF) in sighted and congenitally blind subjects performing auditory localization tasks. During scanning, the spectral and binaural cues of localized sound were reproduced by a sound system and delivered via headphones. During tasks that required auditory localization both the sighted and blind subjects strongly activated posterior parietal areas. In addition, the blind subjects activated association areas in the right occipital cortex, the foci of which were similar to areas previously identified in visual location and motion detection experiments in sighted subjects. The blind subjects, therefore, demonstrated visual to auditory cross-modal plasticity with auditory localization activating occipital association areas originally intended for dorsal-stream visual processing. To determine the functional connectivity of pre-selected brain regions in primary and non-primary auditory and posterior parietal cortex in the two cohorts, we performed an inter-regional correlation analysis on the rCBF data set. During auditory localization in the blind subjects, rCBF activity in the right posterior parietal cortex was positively correlated with that in the right occipital region, whereas in sighted subjects correlations were generally negative. There were no significant positive occipital correlations in either cohort when reference regions in temporal or left parietal cortex were chosen. This indicates that in congenitally blind subjects the right occipital cortex participates in a functional network for auditory localization and that occipital activity is more likely to arise from connections with posterior parietal cortex.