The biology of memory (psychology notes)

Which structures in the brain mediate memory?  Is it possible to study the brain as in input-output system, with central controlling processes that influence how memory works?  With MRI and PET scans it has been possible to identify anatomically distinct brain structures that mediate memory such as the hippocampus and the frontal lobes.

l.  Hippocampus:  located in the limbic system which is responsible for emotional behavior, the hippocampus appears to be important for declarative memory and conscious learning.  It is a vital structure for the encoding functions of working on short term memory (STM).  Damage to this structure leads to a preservation of old facts but difficulty in learning and retaining new facts.  Difficulty in forming memories among some older people may be due to too many stress hormones which interfere with the hippocampus and resulting attention and memory.  This limits the development of new declarative memories.

2.  Amygdala:  located in the limbic system, this structure is involved in emotional conditioning.  It has been shown that with amnesiacs, after they have been conditioned to dislike someone they continue the emotional reaction even though they cannot remember the person to whom they have this reaction.  Damage to this structure leads to difficulty in consciously learning and storing new facts (Declarative Memory) but not all facts.  New skills can be learned indicating that this structure is involved in procedural and not declarative memory.  The fact that we retain skills from early childhood indicates that procedural memory is mediated by other brain structures.  The fact that we cannot remember events before age two indicates we cannot establish very firm declarative memories.  This is in keeping with what is known about the hippocampus.  It is one of the last brain structures to mature fully.  Without a mature hippocampus, as is the case in early childhood -  no firm declarative memories.  This helps explain infantile amnesia -- the inability to remember our very early years between birth and four years of age.

3.  Frontal lobes:  located in the front portions of the cerebral cortex the frontal lobes develop thinking strategies for encoding and retrieval of items.  This structure is also involved in conscious memory and controls the hippocampus which is involved in declarative memory.  The frontal lobes gives the hippocampus direction and controls how it organizes information in incoding.  The frontal lobes also influence the retrieval of relevant information since the hippocampus lacks intelligent discrimination as to which information is relevant doing the retrieval process.  The frontal lobes focus attention and inhibit irrelevant responses.  Further, the frontal lobes influence the ability to remember where and when.  That is episodic memory and learning that requires organization and elaboration.

4.  Neostriatum:  located in the subcortex it controls motor activity and learning of new skills.

5.  Cerebellum  -  located below the cortex toward the back of the brain, it controls muscular conditioning as may occur in fear conditioning.  The hippocampus on the other hand is involved in more complex conditioning.