Memory and Cognition Flashcards
what does cognition relate to?
highest order of brain function and relates to behaviour that deals with thought processing ie make sense of a stituation
what is neuronal plasticity?
ability of central neurons to adapt their neuronal connections in responses to “learning” experiences.
where are memories formed?
the limbic system
what behaviour is the limbic system responsible for?
instinctive behaviour, eg drives for thirst, sex, hunger etc. but also important in emotive behaviour which in turn are drive by seeking reward or avoiding punishment
why are reward and punishment central aspects to learning?
They form the “affective components” of sensory experiences. Motivation to learn comes from gaining a reward or avoiding a “punishment”. Gives a task significance.
which of our experiences are barely remembered?
Experiences that are neither rewarding or punishing (insignificant experiences)
what is the limbic system responsible for in relation to memory?
selecting what experiences are stored in memory (based on the significance of the event)
where does almost all sensory information go through?
hippocampus, which in turn relays information to other limbic system structures.
what is the hippocampus central for?
learning and the formation of memories
what occurs when the hippocampus is damaged?
immediate (sensory) memory (seconds in length) and intact long-term memory (from time before damage), but are unable to form new long-term memories-Anterograde amnesia
describe Immediate or Sensory memory
a few seconds. Describes the ability to hold experiences in the mind for a few seconds. Based on different sensory modalities. Visual memories decay fastest (<1s), auditory ones slowest (<4s).
describe Short-term memory
seconds - hours. Often called Working Memory. Brain’s “post-it note”. Used for short term tasks such as dialling a phone number, mental arithmetic, reading a sentence. Associated with reverberating circuits.
describe Intermediate long-term memory
hours to weeks e.g. what you did last weekend. Associated with chemical adaptation at the presynaptic terminal.
describe Long-term memory
hours to lifetime. e.g. where you grew up and your childhood friends. Associated with structural changes in synaptic connections.
how does short-term memory work?
is an electrical phenomenon. It depends on maintained excitation from reverberating circuits i.e. they need to be constantly refreshed.
what occurs to the reverberation over time if deemed significant?
eventually this reverberation results in consolidation of the memory in long term memory storage
what occurs to the reverberation over time if deemed insignificant?
reverberation fades and no consolidation occurs
what is Retrograde amnesia?
can’t remember events leading up to the injury, although recall of events that happened a long time ago is usually unaffected, probably because they are better rehearsed and more deeply ingrained
often presents with anterograde amnesia
if only the thalamus is damaged, and the hippocampus spared, what type of amnesia is seen?
retrograde amnesia is seen. Suggests thalamus is required for “searching” our existing memory bank.
how does Intermediate Long-Term Memory work?
Involves chemical changes in presynaptic neuron:
Increasing Ca++ entry to presynaptic terminals, increases neurotransmitter release and hence “strengthens” the synapse.
how does Long-Term Memory work?
Involves structural changes at synapses:
Increase in NT release sites on presynaptic membrane.
Increase in number of NT vesicles stored and released.
Increase in number of presynaptic terminals
what is Long Term Potentiation?
greater change in graded membrane potential in the post-synaptic cell (EPSP) which “strengthens the synapse”
(occurs along with structural changes at synapses in long term memory)
what are the two types of long-term memory?
Declarative or Explicit Memory
Procedural/ Reflexive/Implicit Memory
describe Declarative Memory
Abstract memory for events (episodic memory) and for words, rules and language (semantic memory).
Is based mainly in the hippocampus
describe Procedural Memory
Acquired slowly through repetition. Includes motor memory for acquired motor skills such as playing tennis, and rules based learning such as, in the UK, always driving on the left.
Is based mainly in the cerebellum (independent of hippocampus)
what does consolidation require?
takes time (hours/days) requires attention
what occurs to “new memories”
“coded” then stored in the sensory and association areas of the cortex
what does coding of new memories result in?
new memories being stored alongside other existing memories the brain deems similar.
which part of the brain assess the significance of an event in short term memory?
The frontal cortex and its association with the reward/punishment centres in the limbic system
what does the frontal cortex do if an experience is considered useful?
“gates” the Papez circuit
ie the experience is allowed through where it continues consolidation
describe the papez circuit
hippocampus, to mammillary bodies, to anterior thalamus, to cingulate gyrus and back to hippocampus
Reverberating activity then continues where after the papez circuit?
the frontal cortex then the sensory and association areas until the consolidation process is complete.
