Temporal Lobe Pathologies
Visual agnosia: not knowing what is seen A person with generalized visual agnosia experiences shapes but doesn’t see objects under normal aspects (i.e., as tables, apples, mountains, and so on). Prosopagnosia is a specific visual agnosia characterized by inability to recognize faces. A prosopagnosic may seek social connections by talking and touching instead of relying on vision. The condition is specific to faces, and a person with this condition may still see the rest of the world under normal aspects.
Wernicke’s aphasia: language comprehension impairment Wernicke’s area lies in the posterior lateral sulcus. Someone lesioned here may utter grammatical but nonsensical sentences and suffer poor language understanding.
Conduction aphasia: language connectivity disorder Wernicke thought his area commanded Broca’s area to produce grammatically correct sentences in speech and writing. He then hypothesized about a disconnection disorder, in which Wernicke’s and Broca’s areas were intact but had become disconnected. Such a disorder has been found, manifesting itself in patients who recognize that what they say is nonsensical. Wernicke’s area cannot adequately command Broca’s area, and communication fails.
Loss of hearing Damage to the auditory cortex leads to hearing loss. A person may still respond reflexively to alarming sounds, such as loud bangs. Such reflexive responses are initiated by limbic brain structures.
Memory disorders If the hippocampus is damaged, this affects memory. See the section “Limbic System” later in this chapter.
Temporal Lobe Summary
The temporal lobe allows normal perception of a rich and structured world with things automatically encountered and perceived under normal aspects. It is also importantly involved in our linguistic and symbolic abilities, as well as in memory. Damage to certain areas of the temporal lobe can lead to numerous forms of breakdown of normal perception. Damage to other areas can lead to language and memory impairments.