Wednesday, December 26, 2007

From Learning to Memory

In reference to Just Do It:

We've talked quite a bit about all the various types of learning that exist, which, as Kandel pointed out, all occur at synaptic levels.

All this has made me think about memory. What's the point learning something if you can't remember it later? I've spent a number of weeks, months even, trying to soak up that Buzsáki book, Rhythms of the brain.

I found a footnote in it (p. 288) about the synesthetic memory of a Russian named Shereshevskii (which in his case was thought to have interfered with face recognition), explicit and implicit types, kinds of each, all of which use/are used by specific parts of the brain. It might be good to review these:

A. IMPLICIT: "previous experiences aid in the performance of a task without conscious awareness of these previous experiences (Schacter, 1987).

Types are:
a) Priming: "previous contact with something can implicitly aid in its subsequent recall or recognition", "can be conceptual or perceptual", "the remembered item is remembered best in the form in which it was originally encountered" (context is everything)

b) Illusion-of-truth effect: "a person is more likely to believe a familiar statement than a new one." (a danger for older people - they can become more easily preyed upon)

c)Procedural:"long-term memory of skills and procedures, or "how to" knowledge (procedural knowledge)." (linked to cerebellum and the basal ganglia function)

B. EXPLICIT (aka declarative memory): "conscious, intentional recollection of previous experiences and information", "some scientists suggest that episodic memory might be dependent on the right hemisphere, and semantic memory on the left hemisphere." (brain regions involved are medial temporal lobe; hippocampus and related areas of the cerebral cortex)

Types are:
a) Episodic: "memory of events, times, places, associated emotions, and other conception-based knowledge in relation to an experience."

b) Semantic: "memory of meanings, understandings, and other concept-based knowledge unrelated to specific experiences"

Neural structures involved in explicit memory:
"Most are in the temporal lobe or closely related to it, such as the amygdala, the hippocampus, the rhinal cortex in the temporal lobe, and the prefrontal cortex. Nuclei in the thalamus also are included, because many connections between the prefrontal cortex and temporal cortex are made through the thalamus.

The regions that make up the explicit memory circuit receive input from the neocortex and from brainstem systems, including acetylcholine, serotonin, and noradrenaline systems."

Evidence for the distinction between implicit and explicit
Brooks & Baddeley, 1976
Graf & Schacter, 1985, 1987
Jacoby & Dallas, 1981
Tulving, Schacter, & Stark, 1982


Longterm memory: anything longer than 30 seconds, stored as meaning

Short term memory: stored only for about 20 seconds and discarded

Sensory memory: "ability to retain impressions of sensory information after the original stimulus has ceased" Two types:
1. Iconic: "short term visual memory (a sensory memory), named by George Sperling in 1960"
2. Echoic memory : "the auditory version of sensory memory"

(Thank you Wikipedia.)

Here is a very entertaining WNYC radio program on memory, from June 07. It discusses one more kind, creative memory.

More about memory in this program also, about 11 minutes in.

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