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Summary: Biological Perspectives on Memory

A famous brain surgery patient known as H.M. helped convince psychologists that primary and secondary memory were distinct. H.M. had normal primary memory (he could hold a conversation and form complex thoughts) but he had no ability to form new secondary memories (he could not remember anything once his attention was distracted from it).

Much evidence implicates a specific brain area-the hippocampus-in memory. The hippocampus was one of the areas removed in H.M.'s brain operation. The hippocampus seems to integrate information from different areas of the brain, creating memory for facts and events. Memory for sequences and routines-procedural memory-seems to involve other areas of the brain. Procedural memory can be spared even when there is hippocampal damage.

Adrenaline, in small doses, facilitates the formation of new memories. Alcohol, on the other hand, does not help memory and may lead to state-dependent forgetting: memory loss that continues until the same mental state is repeated.

Karl Lashley tried to discover the location of memory traces or engrams. No matter where he cut the brain of a rat, the animals still remembered the route through a maze. Lashley concluded that engrams were stored diffusely throughout the brain, not in specific locations. Modern neuroscientists have drawn the opposite conclusion. Memories for complex tasks such as maze running involve many multiple specialized neural systems for sight, odor, touch, and spatial orientation, and memories for these systems are stored where they are used. These systems are widely distributed in the brain, resulting in the effect Lashley discovered. If one brain area is damaged, otheres can step in to help out with an essential goal such as obtaining food.

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