Transcript Slide 1

Memory (lecture 4)
Thoth
Mnemosyne
Minerva
God/dess of learning, memory & wisdom
Memory in oral cultures
Memory was essential for passing of knowledge:
person to person & generation to generation.
Memory was the fourth of
the five traditional canons of
rhetoric, the others being
invention, arrangement,
delivery, and style.
Memory aided by process of
architectural mnemonic known
as Cicero’s technique: parts of
the speech were associated
with spatial details.
Memory in literate cultures
 Writing: externalized the memory.
 Electronic media: provides fast access to both
verbal and graphical data bases (“the virtual
Cicero’s technique”).
 Eric Havelock: "a modern student thinks he does
well if he diverts a tiny fraction of his psychic powers
to memorize a single sonnet of Shakespeare. In
stead, he pours his energy into search and
reading….
 Memory is extended to artificial fast accessible
devices (soon directly connected to brain).
Memory as a process
Cognitive Ψ: Three stages of memory.
Biological Ψ:
Stages in same/different brain sites?
Neuronal mechanisms of memory?
Life time storage?
Duration of memory: cognitive Ψ
Sensory memory: Vast amount of sensory
information in five modalities kept for very
short time.
Working memory/short-term memory:
Rather limited information kept for short
time in conscious mode.
Long-term memory: Vast amount of
information in subconscious mode.
Duration of memory: biological Ψ
 Short Working-memory:
different sites of frontal
cortex, can we be aware of
all?
 Long-term memory:
migration of information
from hippocampus to
cortex, amnesia in HM
patient.
Technique: experiments by
nature & functional
imaging.
Content of memory
Cognitive Ψ:
 Explicit memory: conscious recollection
of events tagged with time and place.
 Implicit memory: skills with no conscious
recollection of details.
Biological Ψ:
 Explicit memory: evolution-wise recent
brain structures, cortex & hippocampus.
 Implicit memory: evolution-wise old brain
structures.
Conclusions so far
Memory is mediated by multiple brain sites.
Each site:
 Is governed by the three stages of memory:
parallel – distributed processing.
 Processes different content: memory
disintegrates the environment.
 Storing capacity seems to be unlimited
except of working-memory.
 Stores with different time constant.
Working memory (1)
Identity of the letter
Encoding:
 Phonological buffer in
L-hemisphere.
 Semantic buffer in
L-hemisphere.
 Spatial buffer in
R-hemisphere.
Position of the letter
Working memory (2)
Storage:
Low capacity: only 7±2 bits of information.
Disappointed? Don’t despair:
LTM enables chunking and capacity increases to 7±2
chunks of information.
Many working-memory sites?
Fast forgetting due to ‘decay’ and ‘displacement’
(high throughput).
Working memory (3)
Retrieval:
 Easy with minimal mistakes.
 Decision time increases with # of items, i.e., serial
processing.
Decision time paces the
swiftness of conscious
mental computations,
slow thinking!!!
From working-memory to LTM (1)
Maintenance rehearsal in WM: prevents a
decay in a reverberating circuitry.
From working-memory to LTM (2)
In a free recall task:
elaborative rehearsal helps to
encode information in LTM.
LTM (1)
Encoding:
Meaning – the remembered idea.
Elaborate on meaning to add connections between
items.
Exact wording.
Sensory impressions: phonological, visual, smells…
LTM (2)
Storage:
Initial store in hippocampus and later migration to
various cortical sites.
Hippocampus and the surrounding cortex: crossreferencing between the many store sites.
Hippocampus as a cognitive map includes the past
and future (prospective) events.
The many LTM cortical sites
LTM (3)
Storage:
New memories are
consolidated over
period of months
and more.
LTM (4)
Retrieval:
Effortful process – on “tip-of-the-tongue”.
Retrieval cues help - recognition vs. recall.
Failures due to association of one cue with
several items:
* Retroactive interference.
* Proactive interference.
Retrieval cues as
gateways to LTM
‫השראת הגברה‬
‫ארוכת טווח‬
‫(‪ )LTP‬כמנגנון‬
‫שינוי סינפטי‬
‫בדיקה‪ :‬פולס בודד‬
‫למידה‪ :‬רצף פולסים‬
Lessons from amnesia
Hippocampus removed bilaterally.
Spared working-memory.
Anterograde amnesia for explicit-episodic
memory.
Partial retrograde amnesia for explicitepisodic memory.
Other memories spared.
A variety of memories
Priming
Memory aids
END