Auditory agnosia and auditory spatial deficits following left hemispheric lesions: evidence for distinct processing pathways

Auditory recognition and auditory spatial functions were studied in four pa tients with circumscribed left hemispheric lesions. Patient FD was severely deficient in recognition of environmental sounds but normal in auditory lo calisation and auditory motion perception. The lesion included the left sup erior, middle and inferior temporal gyri and lateral auditory areas (as ide ntified in previous anatomical studies), but spared Heschl's gyrus. the aco ustic radiation and the thalamus. Patient SD had the same profile as FD, wi th deficient recognition of environmental sounds but normal auditory locali sation and motion perception. The lesion comprised the postero-inferior par t of the frontal convexity and the anterior third of the temporal lobe, dat a from non-human primates indicate that thr latter are interconnected with lateral auditory areas. Patient MA was deficient in recognition of environm ental sounds, auditory localisation and auditory motion perception, confirm ing that auditory spatial Functions can be disturbed by left unilateral dam age; the lesion involved the supratemporal region as well as the temporal. postero-inferior frontal and antero-inferior parietal convexities. Patient CZ was severely deficient in auditory motion perception and partially defic ient in auditory localisation, but normal in recognition of environmental s ounds; the lesion involved large parts of the parieto-frontal convexity and the supratemporal region. We propose that auditory information is processe d in the human auditory cortex along two distinct pathways. one lateral dev oted to auditory recognition and one medial and posterior devoted to audito ry spatial functions. (C) 2000 Elsevier Science Ltd. All rights reserved.