Music perception in acquired prosopagnosia.

BACKGROUND: Acquired prosopagnosia is often associated with other deficits such as dyschromatopsia and topographagnosia, from damage to adjacent perceptual networks. A recent study showed that some subjects with developmental prosopagnosia also have congenital amusia, but problems with music perception have not been described with the acquired variant. OBJECTIVE: Our goal was to determine if music perception was also impaired in subjects with acquired prosopagnosia, and if so, its anatomic correlate. METHOD: We studied eight subjects with acquired prosopagnosia, all of whom had extensive neuropsychological and neuroimaging testing. They performed a battery of tests evaluating pitch and rhythm processing, including the Montréal Battery for the Evaluation of Amusia. RESULTS: At the group level, subjects with anterior temporal lesions were impaired in pitch perception relative to the control group, but not those with occipitotemporal lesions. Three of eight subjects with acquired prosopagnosia had impaired musical pitch perception while rhythm perception was spared. Two of the three also showed reduced musical memory. These three reported alterations in their emotional experience of music: one reported music anhedonia and aversion, while the remaining two had changes consistent with musicophilia. The lesions of these three subjects affected the right or bilateral temporal poles as well as the right amygdala and insula. None of the three prosopagnosic subjects with lesions limited to the inferior occipitotemporal cortex exhibited impaired pitch perception or musical memory, or reported changes in music appreciation. CONCLUSION: Together with the results of our previous studies of voice recognition, these findings indicate an anterior ventral syndrome that can include the amnestic variant of prosopagnosia, phonagnosia, and various alterations in music perception, including acquired amusia, reduced musical memory, and subjective reports of altered emotional experience of music.

Right hemi-alexia.

While pure alexia was long considered a disconnection syndrome, it may also be a selective visual word agnosia due to damage to the visual word form area. Disconnection is still the likely explanation of hemi-alexias, though, particularly when splenial lesions damage inter-hemispheric projections and cause left hemi-alexia. An intra-hemispheric disconnection causing right hemi-alexia is theoretically possible but seems very rare, with only a single report that has been challenged on the grounds of inadequate perimetry. We describe the case of PH, who had a severe reading deficit in her right hemifield. Detailed perimetry showed only a small relative hemi-scotoma along the horizontal meridian, while word reading was impaired over a much larger expanse of her right hemifield, in which object recognition was spared. Reading, lexical decisions, and perceptual discrimination of words were impaired in the right hemifield, and this extended to letters and numbers, with a trend to an effect on the perception of an unfamiliar script, namely Korean. On magnetic resonance imaging she had a large left lateral occipital meningioma with vasogenic edema of occipital white matter tracts. Functional magnetic resonance imaging showed that the visual word form area was located just anterior to the mass. Her perceptual abnormalities resolved after resection of the tumor. We conclude that right hemi-alexia exists and is most likely due to intra-hemispheric disconnection of occipital input to the visual word form area.

Facial identity and facial speech processing in developmental prosopagnosia.

The neural substrate of acquired prosopagnosia, including its lateralization, remains a matter of investigation. Face processing networks in healthy subjects are right dominant, and acquired prosopagnosia usually results from right or bilateral lesions. Nevertheless, there may be a complementary contribution of the left hemisphere to certain types of face processing. Prior reports suggest that this might be processing faces depicted by line contours, or lip reading. We performed two behavioural studies in seven subjects with developmental prosopagnosia. The first examined their ability to match faces across viewpoint changes, with either unaltered photographs or images that had been reduced to line elements. Prosopagnosic subjects had normal performance with line-contour faces, but failed to show the normal benefit from the additional information in unaltered photographs. The second experiment examined their ability to perceive facial speech patterns. Prosopagnosic subjects could detect, discriminate and identify facial speech patterns, but most showed reduced use of these cues or anomalous audiovisual integration in the McGurk effect, with only one subject performing normally. We conclude that developmental prosopagnosia can be associated with a subtle impairment in lip reading, which in prior studies of acquired lesions has been associated more with left than with right fusiform damage.

Prosopagnosia: current perspectives.

Prosopagnosia is a selective visual agnosia characterized by the inability to recognize the identity of faces. There are both acquired forms secondary to brain damage and developmental forms without obvious structural lesions. In this review, we first discuss the diagnosis of acquired and developmental prosopagnosia, and the challenges present in the latter case. Second, we discuss the evidence regarding the selectivity of the prosopagnosic defect, particularly in relation to the recognition of other objects, written words (another visual object category requiring high expertise), and voices. Third, we summarize recent findings about the structural and functional basis of prosopagnosia from studies using magnetic resonance imaging, functional magnetic resonance imaging, and event-related potentials. Finally, we discuss recent attempts at rehabilitation of face recognition in prosopagnosia.