Simultaneous auditory agnosia: Systematic description of a new type of auditory segregation deficit following a right hemisphere lesion

Abstract We investigated auditory processing in a young patient who experienced a single embolus causing an infarct in the right middle cerebral artery territory. This lead to damage to auditory cortex including planum temporale that spared medial Heschl’s gyrus, and included damage to the posterior insula and inferior parietal lobule. She first reported difficulty hearing all sounds, which fully recovered within days, but she subsequently reported chronic difficulties with segregating speech from noise and segregating elements of music. Clinical tests showed no evidence for abnormal cochlear function. Follow-up tests confirmed difficulties with auditory segregation in her left ear that spanned multiple domains, including speech-in-noise and music streaming. Testing with a stochastic figure-ground task—a way of estimating generic acoustic foreground and background segregation—demonstrated that this was also abnormal. This is the first demonstration of an acquired deficit in the segregation of complex acoustic patterns due to cortical damage, which we argue is a causal explanation for the symptomatic deficits in the segregation of speech and music. These symptoms are analogous to the visual symptom of simultaneous agnosia. Consistent with functional imaging studies on normal listeners, the work implicates non-primary auditory cortex. Further, the work demonstrates a (partial) lateralisation of the necessary anatomical substrate for segregation that has not been previously highlighted. Highlights Rare case of auditory agnosia in a young patient with a right-hemisphere infarct Damage affecting non-primary auditory cortex, but sparing primary auditory cortex Generalised auditory segregation deficit, revealed by auditory figure-ground task This explains segregation deficits for speech-in-noise and music streaming The deficit affects stimuli presented on the left