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Hippocampus and the blood supply to TE: parahippocampal pial section impairs visual discrimination learning in
Abstract:
In the base of each temporal lobe in 4 monkeys (Macaca fascicularis) we sectioned the pia mater in an antero-posterior line along the most medial part of the inferior temporal visual association cortex (area TE), lateral to the parahippocampal cortex. This pial section interrupts the blood flow in branches of the posterior cerebral artery which cross the parahippocampal gyrus en route to area TE. Histologically, the brains of 2 of these animals did not show any abnormalities in cresyl violet stained material, apart from the small cortical damage along the line of the pial section itself. Of the remaining two animals, one had a small unilateral infarct in TE and one had bilateral infarcts in TE. All of these animals were impaired in visual discrimination learning, and the severity of impairment was correlated only imperfectly with the severity of infarction. These results show that pial section along the medial boundary of area TE can affect visual discrimination learning without producing large infarcts. Further, since aspiration lesions of the hippocampal formation require the pia mater to be sectioned in a similar way to that reported here, the effects of such aspiration lesions on visual learning and memory may be mediated in part by effects on TE.
Insights
Pial sectioning near the inferior temporal visual association cortex (area TE) impaired visual discrimination learning in monkeys. This damage occurred even without large infarcts, suggesting area TE
Area of Science:
- Neuroscience
- Primate behavior
- Cerebral blood flow
Background:
- The inferior temporal visual association cortex (area TE) is crucial for visual processing.
- Understanding the vascular supply to area TE is important for interpreting lesion studies.
Purpose of the Study:
- To investigate the effects of restricted blood flow interruption to area TE on visual discrimination learning.
- To determine if damage to area TE, independent of large infarcts, impacts cognitive function.
Main Methods:
- Pia mater sectioning was performed in the medial part of area TE in four macaque monkeys.
- Histological analysis assessed the extent of cortical damage and infarction.
- Visual discrimination learning tasks evaluated cognitive performance.
Main Results:
- Pial sectioning led to impaired visual discrimination learning in all subjects.
- The severity of impairment correlated imperfectly with the extent of infarction.
- Some animals showed significant learning deficits with minimal or no visible infarcts.
Conclusions:
- Pial sectioning of area TE can disrupt visual discrimination learning without causing substantial infarcts.
- These findings suggest that even subtle vascular disruptions in area TE can impact cognitive function.
- The results imply that aspiration lesions of the hippocampal formation might affect visual learning partly through alterations in area TE.