Chapter 13: The Temporal Lobes

- Anatomy
    - Temporal lobe consists of all the tissue that lies below the Sylvian fissure and anterior to the occipital and parietal cortex
    - Brodmann identified 10 temporal lobe areas, but there are many more
    - Regions on the lateral surface can be divided into those that are auditory
        - Brodmann's areas 41, 42, and 22
    - Also divided into areas that form the visual stream on the lateral temporal lobe
        - Areas 20, 21, 37, and 38

- Connections of the temporal cortex
    - 4 distinct types of cortico-cortical connections
        - Hierarchical progression of connections from primary and secondary auditory and visual areas, ending in temporal pole
        - Series of parallel projections from the visual and auditory association areas into the polymodal regions of the superior                 temporal sulcus
        - Projection from the auditory and visual association areas into medial temporal regions
        - Series of parallel projections from the association areas to the frontal lobe
- Theory of temporal lobe function
    - Does not have a unitary function
    - 3 basic functions
        - Processing auditory input
        - Visual object recognition
        - Long-term storage of sensory input 
    - Matching visual and auditory information- cross-modal matching 
        - Also involves the cortex of the STS 
- Asymmetry of temporal lobe function
    - Sensitive to epileptoform abnormalities
        - Surgical removal of the abnormal temporal lobe is beneficial in treating epilepsy 
    - Damage to the left temporal lobe- deficits in verbal memory
    - Damage to the right temporal lobe- - deficits in nonverbal memory 
- Disorders of auditory perception
    - Bilateral damage to the auditory cortex produces cortical deafness 
        - Little disruption of sensitivity to changes in sound frequency or intensity 
    - Study by Tallal and Piercy- found that cortical lesions appear to increase the time needed between sounds to discriminate the sounds 
        - Related to common complaint of people with left temporal lobe damage that people are speaking too quickly 
- Disorders of visual perception
    - Do not normally have large deficits in visual perception
    - Milner- found that patients with right temporal lobectomies had trouble interpreting cartoon drawings
        - McGill Picture- Abnormalities test- can't find anything abnormal about the pictures
        - Perform poorly on the Mooney Closure test and related tests

Image: http://www.mst.nl/neurochirurgie/Onderzoek/tinnitus.doc/tinnitus-3.jpg
Comments