Abstract
MC is a 38-yr old right-handed female who, apart from some sparing in rostral calcarine cortex, has suffered extensive bilateral hypoxic ischemic cortical damage encompassing her occipital cortices extending dorsally into the temporal lobe bilaterally and the right posterior parietal cortex. Conventional perimetry demonstrated some preserved visual motion perception in her upper left quadrant, but no detection of static stimuli. Despite the extensive damage in visual areas, MC's auditory system is intact. Accordingly, MC was tested on several studies in order better understand the interaction between auditory and visual perception. 1) For instance, although MC was better than chance at indicating whether a silent video contained a face that was talking or nodding (i.e., she appeared to detect mouth motion), this information did not influence her auditory perceptual identity of spoken words (i.e., no McGurk effect), nor did it help her identify speech sounds presented in background noise. 2) Interestingly, in an auditory noise burst localization task, visual transients presented in MC's upper right visual quadrant were associated with slower response times to sounds relative to when no transients were present. In contrast, visual transients presented in her upper left visual quadrant were associated with faster response times relative to when no transients were present. 3) Finally, although MC showed a marked inability to perceive material properties of objects (e.g., textures) through vision, she had no problem carrying out a similar auditory task that involved discriminating dynamic sounds of various manipulated materials (e.g., crumpling paper, plastic, styrofoam, or aluminum foil) from scrambled versions of these sounds as well as from non-verbal human vocalizations. Functional magnetic resonance imaging (fMRI) in this study demonstrated that her material-properties auditory ability relied on regions in the right parahippocampus and posterior middle temporal areas bilaterally.
Supported by grants from the Canadian Institutes of Health Research.