Chapter 24.docx

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21 Apr 2012
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Types of memory and amenisa
Learning is the acquisition of new info. Memory is the recall of learned info.
Declarative and nondeclarative memory
Declarative (explicit): memory for facts and events.
Nondeclarative (implicit)
o Procedural: memory for skills, habist and behaviors
Declarative memory can be accessed for conscious recollection; nondeclarative u sually can’t.
Declarative is explicit (conscious effort) and nondeclarative is implicit (direct experience).
Declarative are easy to create and forget.
Long-term,short- term and working memory
Working memory: memory that is remembered over days, months and years. Not all memory
makes it into long- term storage (dinner yesterday vs dinner last week).
Memory that was readily lost was called short- term memory. Short- term memory is selectively
kept through memory consolidation. STM is not necessary required for MC though
Working memory is the information we hold in “our minds”. It is a temporary form o f iformation
storage that’s limite in capacity. Digit span (no of digits a person can remember) is usually 7, plus or
minus 2. One sensory modality can be selectively damaged (i.e. seeing versus hearing 7 numbers),
supporting idea of multiple memory storage sites.
Amnesia
Amnesia: serious inability to recall or create memories, usually caused by disease. Limited amnesia
is more common than absolute amnesia. Dissociated amnesia refers to amnesia w/o cognitive
deficits.
o Retrograde amnesia: memory loss for events before trauma. The loss is graded: the more
recent the event, the weaker the recollection. It might reflect structural changes in the brain
o Anterograde amnesia: inability to create new memories. Severe cases are characterized by
complete lack of learning, whereas most cases need repetition in learning new things
(slower process).
o Transient global amnesia is sudden anterograde amnesia that lasts minuts to days. Perform
appears disoriented and asks the same questions repeatedly. Cerebral ischemia (reduced
blood flow) and trauma seem to play a role. In general, it seems to be a temporary
deprivation of blood to arreas important for learning/ memory.
Box 241. An extraordinary memory
S. Luria (Sherashevsky) came to Aleksandr Luria. He had an insane memory -> could remember lists
of 70 words, lists from 15 yrs earlier, etc. He seemed to create a photograph in his brain of the list
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and simply recall from that (unusual sensory response to stimuli). He also had synthesia (sensory-
response disconnect). Hearing a sound would put a tastein his mouth (multimodal response to
sensory input established strong memory traces). He had trouble processing complex info (i.e. faces
bcz expression changes became stimulus, reading a story bcz each word triggers multiple sensory
modalities). He couldn’t forget though either
Box 24.2 A fish tale of memory loss
Pfiesteria piscicida is a dinoflagellate that releases a neurotoxin to kill fish. Another d, Gambierdiscus
toxicus, produces ciguatoxin in fish that doesn’t’ kill them. Ciguatoxin binds to Na+ channels to
increase excitability. Nausa, diarrhea, neurosymptoms such as numbness and tinbling of mouth,
itching, etc. Pfiesteria patients suffer from memory los, trouble concentrating, disorientation,
confusion.
The Search for the Engram
Engram (memory trace) is the physical location/ representation of a memory
Lashley’s studies of maze learning in rats
Rat’s brains were lesioned. Lesions before learning a maze made it harder for the rat to learn to
avoid the dead ends. Lesions after mae the rat forget where the dead ends were.
o The deficits caused by lesions were dependent on size of lesion, not location. Lashley
asserted that this meant that neural changes are spread out throughout cortex. However,
the size of the elesions could mean damage to several areas
Hebb and the Cell Assembly
Hebb proposed a cell assembly. The basic idea is that there’s a collection of cells that are activated
by a stimulus. The stimulation persists after the stimulus is removed, strengthening the reciprocal
connections between the cells. Partial activation of the assembly causes activation of the entire
aseembly. Destruction of components deosn’t destroy the entire assembly. Hebb’s two points were
that 1) engram is spread widely over the connetions that link components of the assembly and 2)
the neurons that are activated could be the ones activated by sensation and perception
Localization of declarative memories in neocortex
Hebb proposed the idea that we should be able to localize the engram if it is dependent upon a
certain sensory modality
Studies in monkeys
o Macaque monkeys can be taught to discriminate between two differing objects visually. A
lesion is made in the inferotemporal cortex (area IT) of the temporal lobe, a high order
visual area. The monkey can no longer do the task (even though it has vision). Area IT is thus
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