Psychology

Psychology

The MTL memory system includes the hippocampal formation (CA fields, dentate gyrus, subicular complex), perirhinal, entorhinal, and parahippocampal cortices. It is known to be important for the storage and processing of declarative memory, which allows for factual recall. It is also known to communicate with the neocortex in the establishment and maintenance of long-term memories, although its known functions are independent of long-term memory. Nondeclarative memory, on the other hand, which allows for the performance of different skills and habits, is not part of the MTL memory system. Most data point to a "division of labor" among the parts of this system, although this is still being debated and is described in detail below.[1]

In animal models, researchers have shown monkeys with damage to both the hippocampus and its adjacent cortical regions were more severely impaired in terms of anterograde amnesia than monkeys with damage localized to hippocampal structures.[1] However, conflicting data in another primate study point to the observation that the amount of tissue damaged does not necessarily correlate with the severity of the memory loss.[9] Furthermore, the data do not explain the dichotomy that exists in the MTL memory system between episodic memory and semantic memory (described below).[1]

An important finding in amnesic patients with MTL damage is the impairment of memory in all sensory modalities – sound, touch, smell, taste, and sight. This reflects the fact that the MTL is a processor for all of the sensory modalities, and helps store these kind of thoughts into memory. In addition, subjects can often remember how to perform relatively simple tasks immediately (on the order of 10 seconds), but when the task becomes more difficult, even on the same time scale, subjects tend to forget. This demonstrates the difficulty of separating procedural memory tasks from declarative memory; some elements of declarative memory may be used in learning...

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