Progressive associative phonagnosia: a neuropsychological analysis

Abstract

There are few detailed studies of impaired voice recognition, or phonagnosia. Here we describe two patients with progressive phonagnosia in the context of frontotemporal lobar degeneration. Patient QR presented with behavioural decline and increasing difficulty recognising familiar voices, while patient KL presented with progressive prosopagnosia. In a series of neuropsychological experiments we assessed the ability of QR and KL to recognise and judge the familiarity of voices, faces and proper names, to recognise vocal emotions, to perceive and discriminate voices, and to recognise environmental sounds and musical instruments. The patients were assessed in relation to a group of healthy age-matched control subjects. QR exhibited severe impairments of voice identification and familiarity judgments with relatively preserved recognition of difficulty-matched faces and environmental sounds; recognition of musical instruments was impaired, though better than recognition of voices. In contrast, patient KL exhibited severe impairments of both voice and face recognition, with relatively preserved recognition of musical instruments and environmental sounds. Both patients demonstrated preserved ability to analyse perceptual properties of voices and to recognise vocal emotions. The voice processing deficit in both patients could be characterised as associative phonagnosia: in the case of QR, this was relatively selective for voices, while in the case of KL, there was evidence for a multimodal impairment of person knowledge. The findings have implications for current cognitive models of voice recognition.

Fig. 1

Representative T1-weighted coronal brain MRI sections from each patient (the right hemisphere is shown on the left side of each image). Sections have been selected to show the following regions of potential relevance to voice processing deficits: a, frontal lobes; b, temporal poles; c, anterior temporal lobes; d, mid-temporal lobes including Heschl's gyri; e, temporo-parietal junction. Focal cerebral atrophy is shown in both patients: in QR, bilateral fronto-temporal atrophy accentuated in the right anterior temporal lobe and extending posteriorly and including the superior temporal sulcus; and in KL, bilateral predominantly anterior temporal lobe atrophy, more marked on the right side and in the inferior temporal cortices including the fusiform gyrus.