Amnesia

From Psy3241

Amnesia is a memory deficit, resulting from brain damage, disease, or injury. Memory loss may be selective or generalized, temporary or permanent, and it may affect short-term memory, long-term memory, or both. Research for amnesia is does not have the ability to be experimentally manipulated. Therefore, amnesia information is reliant on amnesic individuals who volunteer for research.

Diencephalic Amnesia

Damage to the diencephalic structues also has the ability to lead to memory impairments. Cases of diencephalic amnesia were used in a study by Knowlton et. al. hypothesizing separate but parallel learning systems. In patients with amnesia, either with damage to the hippocampal formation or diencephalic midline, participants performed normally on a probabilistic classification task. However, scores for a declarative memory task were poor. The results were opposite for participants with Parkinson's disease. These results demonstrate declarative memory is dependent on the medial temporal lobe or diencephalon, but not on the neostriatum. The opposite is the case for probabilistic classification learning. A 'pure' case of diencephalic amnesia comes in the form of NA. After suffering a freak accident involving a fencing foil, NA had damage to his left dorsal thalamus, his mamillary bodies (bi-laterally), and his mamillo-thalamic tract. He showed normal short-term memory, but was severely impaired in declarative long-term memory, particularly for verbal material.

References

Knowlton, B. J., Mangels, J. A., & Squire, L. R. (1996). A neostriatal habit learning system in humans. Science, 273(5280), 1399-1402.