Phonagnosia

Lore & Background

Phonagnosia was first described by a study by Van Lancker and Cantor in 1982, in which subjects were asked to identify which of four names or faces matched a specific famous voice and could not complete the task. Clinical and radiologic findings with computerized tomographic scans suggest that recognition of familiar voices is impaired by damage to the inferior and parietal regions of the right hemisphere, while voice discrimination is impaired by temporal lobe damage of either hemisphere. Studies have shown evidence for a double dissociation between voice recognition and voice discrimination, with some patients performing normally on discrimination tasks but poorly on recognition tasks, and vice versa.

Associative phonagnosia develops with dementia or other focal neurodegenerative disorders. Some research has shown that phonagnosics also have trouble recognizing the sounds of familiar instruments, though they are much less affected in this area compared to voice discrimination. Controversy exists because not all phonagnosics exhibit these symptoms, and separate brain areas handle language and music information. Phonagnosics can correctly detect emotions in voices and match emotions with facial expressions, which is attributed to the limbic system being a separate system within the brain.

A case study of QR, a patient with behavioural variant frontotemporal dementia, showed bilateral fronto-temporal atrophy mostly in the right anterior temporal lobe. Another case, KL, had temporal variant frontotemporal lobar degeneration with progressive right temporal lobe atrophy. More recently, a study of developmental phonagnosia in a 60-year-old woman named KH, who exhibited all symptoms without brain damage, suggested the disorder can result from cognitive abnormalities. No therapy or treatment currently exists for phonagnosia.

Reader's Guide

Phonagnosia is significant as an auditory agnosia that demonstrates a functional separation between structures for linguistic comprehension and those for perception of speaker identity. Its study has revealed a double dissociation between voice recognition and voice discrimination, with distinct neural substrates: right hemisphere inferior and parietal regions for recognition, and temporal lobes of either hemisphere for discrimination. The discovery of developmental phonagnosia in KH, without structural brain damage, challenged the assumption that phonagnosia only results from acquired brain damage, opening avenues for cognitive-based theories. The disorder's association with impairments in recognizing familiar instrument sounds, though controversial, suggests overlapping but distinct neural processing for voices and music. The preservation of emotion detection in voices, linked to the limbic system, underscores the modularity of auditory processing. The lack of treatment highlights the need for further research, as current knowledge remains limited. Phonagnosia's appearance in popular culture, such as in the Tollywood film Prasanna Vadanam, reflects its growing recognition. Its legacy lies in informing understanding of auditory perception, brain lateralization, and the dissociation between different types of auditory recognition.

Did You Know?

• Phonagnosia was first described in a 1982 study by Van Lancker and Cantor.
• Phonagnosics can correctly detect emotions in voices and match emotions with facial expressions.
• The first known case of developmental phonagnosia, KH, had no brain damage associated with the impairment.
• There is currently no therapy or treatment for phonagnosia.