memory systems Flashcards
what are the components of a memory system
amount of memory
duration of memory
information type of memory
what is declarative memory broken into
semantic and episodic
what is nondeclarative memory broken into
procedural (skill)
priming
conditioning
memory
the persistence of retriable information
we are no going to retrieve a memory the exact way it was stored
can be applied to more than just human memory
ingram-engram distinction
about whether the information was acquired within an individual’s lifetime
there are no sharp boundaries between ingrams and engrams
both involve storage and retrieval
cognitive capacity and expression form a similar continuum
chomsky hierarchy
outlines types of cognitive (language) functions by memory requirements
the range of operations that can be executed (“grammers”) are constrained by memory
like simple to complex and simple machine
how much memory are we relying on? ie/ not needed for reflexes
type 0: recursively enumerable
- most complex and general
- computable
- unrestricted
- pragmatics in human language
- social implications of language - ie/ saying its cold to the room so the people next to the thermostat turn it up
type 1: context sensitive
- require rules that depend on the context of the symbols around them
- like equal numbers of a,b,c
- syntax of human languages
- humans use vocal communication, order of words in a sentence
- deeper language sotres
type 2: context free
- little more complex
- sentences in a language or embedded in ()
- storing simple units
- animal sounds
type 3: regular/ finite
- simple and easy to describe
- patterns that repeat
- no memory like a reflex
- simple machine with only a few buttons like a vending machine
- lowest amount of memory
- do not need to know just need to know the state that it is in
how long is sensory buffer
less than 1s
depends on modality and how long it is being stored in reflexes/ pathways before the cortex
how long is short term memory
15-30 secs
how long is intermediate term
30+ mins
how long is long term memory
indefinite
some stored for the rest of their life
working memory
manipulating info that is coming through the senses
transformation in short term memory
phonological loop and visuospatial sketchpad controlled by the central executive
both modules have limited timespans and capacity, and do not mutually interfere in the way that similar module information type causes interference
phonological loop
rehearsal of verbal items, especially in sequences , hearing, sound info
visuospatial sketchpad
rehearsal of object location (sequence) information
central executive
theorized to manage working memory
prefrontal cortex
focus and divide attention, task switching
episodic buffer
hold multidimensional code chunks
linking perception, working memory and long term memory
declarative
things you know that you can tell others
explicit
nondeclarative (procedural)
thinking you know that you can show by doing
episodic memory system
remembering your first day of school
extracts and stores the content from our experiences
- when and where did an event occur?
- who and what were present?
- what happened, in what order?
conscious recollection and storage of info and retrieval
can acquire info abut an event that happens only once, yet protect the representation from interfering with each other
semantic
knowing the capital of France
skill learning
knowing how to ride a bike
priming
being more likely to use a word you heard more recently
conditioning
salivating when you see a favourite food
henry molaison
patient HM began having debilitating seizures at 16
at 27 he had his hippocampus (on both sides) and surrounding structures surgically removed
henry could remember some of his past, did not consolidate new episodic memories
- anterograde amnesia
he could develop new skills (ie/ mirror-tracing)
The delayed nonmatching to sample (DNMS) Task
monkeys retrieve a reward behind an object
- after a variable amount of time delay the monkey sees two objects:
1. an object that previously had a reward behind it
2. a novel object (mostly chosen)
in this test trial, the reward is always found behind the novel object
- finding the reward requires memory of which object was searched for
hippocampus and the delayed nonmatching task (DNMS)
surgical removal of both amygdala and hippocampus do not result in DNMS deficit
will still perform the task well
neither structure is directly involved in DNMS memory
- instead, subsequent animal and human research showed that damage to the rhinal cortex caused memory impairment for the DNMS
hippocampus role in episodic memory
a traditional unitary view of hippocampus function is that all its structures are involved in the production of declarative memories
DNMS performance does not rely on episodic memory
hippocampus is important for episodic recollection, but the adjacent cortex is important for familiarity
evidence of the modular hippocampus
young children with MDL damage after ischemic stroke:
- develop normal language and social skills, with fully normal levels of vocabulary and other forms of semantic memory
familiarity information does not require episodic context
- rats with hippocampal damage still learn to recognize objects, but do not retain information about the learning context
what are the properties of episodic memory
has three properties
1. it supports the conscious recollection of contextual spatiotemporal information for later retrieval
- intentional initiation of retrieval-intentional search for a memory
- conscious awareness of remembering (a member trace being successfully activated)
- does not require either to be active
- It automatically captures episodic and incidental information about single episodes of our lives
- does not require the intention to encode or consolidate the memory
- incidental info, no intention, stuff you do not need to know - it includes information about the spatial and temporal context that is protected from interference by other memory traces
- the stability-plasticity dilemma
ie/ can we distinguish between classes or dinner with the same people every night
the brain supports episodic memory through a hierarchy and a loop
remembering emerges when a retrieved memory trace info about the time, place or context of an experience. Once we remember this it becomes easier to remember things
the hierarchy
hippocampus is embedded in neural systems and therefore can interact with other brain regions - has unique intrinsic organization and synaptic connection
episodic experiences are first transduced by sense receptors and then processed hierarchially until they reach the hippocampus
hippocampus can receive info from many areas because it sits on top
uni and polymodal cortical areas support perception processes
perirhinal and parahippocampal areas support associative recall
entorhinal cortex supports spatiotemporal event context
located in medial temporal lobes
level of information increases throughout the hierarchy
info highly processes before in reaches the hippocampus, becomes amodal ( neurons do not know if people are receiving auditory, visual or somatosensory
the loop
hippocampus is insensitive to certain sense ie/ it does not know if it is smell or sound
the hippocampal loop supports sequential indexing integrated (amodal) event infromation
information is the most compressed and abrstact in the hippocampus
anterograde amnesia result from damage to the hippocampus
the indexing theory of episodic memory
accounts for three aspects of the relationship between memory and the brain
1. the role of the hippocampus in episodic engram formation (provides map to cortical areas that contain our experiences) has info about pattern activity represented by strengthening of synapses between neocortex and hippocampal neurons and strengthening neurons
- the nature of the engram
- the role of the hippocampus in memory retrieval
the theory posits that the hippocampus does not store memories, but rather pointers (indices) to memories that are stored in the neocortex
assumes individual features that make up a specific episode establish a memory trace by activating patterns of neocortical activity, which then project to the hippocampus
A - Es of index theory
A. the hippocampus and neocortex at rest (sleep?)
B. experience represented in cortex is processed through the memory hierarchy
C. A subset of the experience (engram) us conjoined with a hippocampal index neuron (s)
D. retrieval cues activate the index in the hippocampus. ie/ what you are doing on new years
E. the index helps to reactivate the of the stored engram
pattern completion and seperation
the index itself has no episodic memory content
- the hippocampus is amodal
pattern completion
the ability for the index to restore an entire memory from a single cue
activate replay of entire experience. possible because synapses represent patterns in neocortex (has been strengthened)
neurons in the neocortex project back to the same hippocampal place that projected to it
pattern seperation
a retrieval cue might activate multiple indices, but most activated one will activate only the engram it is associated with
memories have overlap - if youenter overlap you are not going to know which engram you entered) - ampount of activation determines which is activated
which one gets selected
creates different indices from similar patterns cause convergence on different neurons
evidence for the indexing theory
animal experiments provide a few research advantages
- fear conditioning is a simple form of learning that is easily controlled in rodents
- systematic damage to brain structures can be performed precisely
one observation from fear conditioning studies is that animals who are pre-exposed to a context are more readily fear conditioned to it
- context pre exposure facilitation
based on immediate shock effect
rat placed into locked chamber and shocked within 6 secs later will show no fear to conditioning chamber
however if allowed to explore chamber before, it will show fear to that context
- rat acquired a representation of the context so not preexposed to a shock
context pre exposure facilitation effect
index theory explains the CPFE as resulting from pattern completion of the shock from the context cue
if this is true, rat should be fear conditionable to a context they were pre exposed to but no necessarily shocked in
it also implies that hippocampal damage will prevents CPFE
preexposure created false memory
why is the the hippocampus key
rats also have preference for exploration of novelty
A. when a rat has experience for cubes in context A and cylinder in context B
B. they prefer to spend time with the cylinder in context A and the cube in context B
rats with hippocampal damage will treat explored objects familiar regardless of context
- failure of pattern separation
- more readily generalize fear conditioning between contexts
rats with hippocampal damage can not remember objects they previously explored
keep actively exploring our environments
if they have prior exposure to these object then hippocampal damage does not matter because there is a familiarity
creating false memories (optogenetic)
A. DOX prevents expression of ChR2 in infused DG neurons
B. DOX off rats develop an index for “context A”
C. DOX-on (no new ChR2) rats shocked in context B and blue light applied
D. Rats tested in context A or C
E. Rats with light applied to froze more in context A
- false memory success
inhibiting memory retrieval
A. CA1 neurons injected with ArchT (neuron silencer)
B. DOX-off rats express ArchT are are fear conditioned
C. Application of green light activates ArchT, silencing CA1 neurons
D. and inhibiting their fear
control of cortical engram neurons
production of neurons in the cortex
- many distributed cortical neurons are parts of engrams
- H2B-GFP TetTag mouse expresses green fluorescent protein when DOX is off
A. DOX-on, no GFP expression
B. DOX-off, many neurons in the brain express GFP
C. DOX-on, retrieval activates c-Fos (immediate early gene)
D. Co-expression of GFP and c-Fos reflects engram neurons and were found in many regions
optogenically silencing index neurons in CA1 caused a reduction in co-labelled neurons in several cortical areas
- therefore, the retrieval memories is influenced by the dynamics of hippocampal index neurons
