Wikipedia
Phonagnosia (from Ancient Greek φωνή phone, "voice" and γνῶσις gnosis, "knowledge") is a type of agnosia, or loss of knowledge, that involves a disturbance in the recognition of familiar voices and the impairment of voice discrimination abilities in which the affected individual does not suffer from comprehension deficits. Phonagnosia is an auditory agnosia, an acquired auditory processing disorder resulting from brain damage, other auditory agnosias include cortical deafness and auditory verbal agnosia also known as pure word deafness.
Since people suffering from phonagnosia do not suffer from aphasia, it is suggested that the structures of linguistic comprehension are functionally separate from those of the perception of the identity of the speaker who produced it.
Phonagnosia is the auditory equivalent of prosopagnosia. Unlike Prosopagnosia, investigations of phonagnosia have not been extensively pursued. Phonagnosia was first described by a study by Van Lancker and Cantor in 1982. The subjects in this study were asked to identify which of four names or faces matched a specific famous voice. The subjects could not complete the task. Since then, there have been a couple studies done on patients with phonagnosia. The clinical and radiologic findings with computerized tomographic scans cat scan in these cases 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. These studies have also shown evidence for a double dissociation between voice recognition and voice discrimination. Some patients will perform normally on the discrimination tasks but poorly on the recognition tasks; whereas the other patients will perform normally on the recognition tasks but poorly on the discrimination tasks. Patients did not perform poorly on both tasks.
Associative phonagnosia is a form of phonagnosia that develops with dementia or other focal neurodegenerative disorders. Some research has led to questions of other impairments in phonagnosics. Recently, studies have shown that phonagnosics also have trouble in recognizing the sounds of familiar instruments. As it is with voices, they also show deficiency in distinguishing between sounds from different instruments. Although the disability is shown, phonagnosics are much less affected in this area of sound discrimination. In distinguishing voices, it is a complete agnosia, but this is not the case for musical instrument sounds, as they can correctly identify some of them. Controversy arises in that not all phonagnosics exhibit these symptoms, and so not all researchers agree that it should be attributed to the damage suffered that causes phonagnosia. Much debate has arisen over the fact that it seems that separate areas of the brain are utilized to handle information from language and music. This has led some researchers to skeptically consider this impairment as a clear symptom of the disorder. Again, more research is needed to create a clearer conclusion.
An interesting attribute that phonagnosics possess is that they can correctly detect emotions in voices when someone talks to them. They can also correctly match an emotion with a facial expression. Although surprising, this finding is sensible because it is known and well agreed upon that the limbic system, involved in expressing emotions and detecting emotions of others, is a separate system within the brain. The limbic system is made up of several brain structures including the hippocampus, amygdala, anterior thalamic nuclei, septum, limbic cortex and fornix.
Presently, there is no therapy or treatment for phonagnosia. Clearly, more research is needed to accomplish the feat of developing treatment for the disorder. The lack of treatment stems from the lack of knowledge about the disorder. Increased research will reveal vital information needed to formulate effective treatments and therapies.