learning and memory Flashcards
what is learning?
the acquisition of new information
what is memory?
retention of learned information
2 types of memory?
declarative and non-declarative
what is the difference between declarative and non declarative memory?
declarative is explicit, information you can verbally declare
-eg. date of birth, where you were born
non-declarative is implicit, about procedural memory
-eg. motor skills, habits, driving a car
which brain regions are involved with non-declarative memory?
striatum is involved in procedural memory - skills and habits
cerebellum is involved in skeletal musculature
amygdala is involved in emotional responses
types of declarative memory
- working memory
- short term memories
- long term memories
what is working memory?
temporary storage, lasts seconds
what are short term memories?
more stable than working memory
vulnerable to disruption
facts and events stored in short-term memory
what are long term memories?
recalled months or years later
what happens to selective short term memories?
they become long term memories - stored in different parts of the brain
location of the brain involved in working memory?
prefrontal lobe
functions of the pre frontal cortex:
- self-awareness
- capacity for planning and problem solving
what was the method of the delayed response task?
-monkey sitting down, series of wells in front of them
-food placed in 1 of the wells, screen placed in front
-screen comes up, monkey remembers which well had the food in
“cue period” - monkey needs to retain the info in this period
“delay period” - monkey remembering where the food is
“choice period” - choosing the well
what were the results of the delayed response task?
showed the role of the pre frontal cortex in working memory
-the information about which well had the food was retained for a short period of time
-increase in activity during the “delay period” -
sub populations of neurones in the pre frontal cortex have increased activity when the monkey is retaining the information in its short term memory
delayed-saccade task
role of lateral intra-parietal cortex neurones in working memory
- saccadic eye movements to the fixation point, monkey gets a reward if they get it right
- saccadic eye movements enable you to scan the environment quickly
- increase in neuronal firing during delay period
where are memories stored?
the engram
how are all the neurones interconnected?
via neural networks
-group of neurones firing together will lead to heavier modification of electrical circuits, strengthens connections between neurones
what is meant by the term consolidation?
short term memory -> long term memory
where is the hippocampus?
in the medial temporal lobe
information flow through the medial temporal lobe
sensory info goes to cortical association area –> parahippocampal and rhinal cortical areas –> hippocampus –> thalamus and hypothalamus via the fornix
what is the output pathway of the hippocampus and where does it go?
the fornix, goes to the hypothalamus and thalamus
what is movement of sensory info through the media temporal lobe important for?
consolidation
do memories stay in the hippocampus?
not necessarily, they can go to the thalamus and hypothalamus, which sort them out and send them to different regions of the cortex depending on what it is
are all long term memories in the hippocampus?
no, they are also distributed across the brain in the form of engrams
define amnesia?
serious loss of memory or ability to learn
causes of amnesia?
concussion, chronic alcoholism, encephalitis, brain tumour, stroke
types of amnesia?
retrograde
-problems with memories they had before the trauma
anterograde
- problems with memories they have after the trauma
- inability to form memories but long-term memories are stored
what severely compromises hippocampal function?
removal of the medial temporal lobe
consequence of viral encephalitis?
affected hippocampus, significant impairment to declarative memory
-stuck in a short loop
spatial memory and place cells - experiment and results
- Morris water maze
- mouse in the water, has to swim around and get to the platform - can’t see because the water is cloudy
- mouse will use navigational uses to get to the platform faster over time
- if we block the neurones in the hippocampus, you will modulate the spatial neurones, so the mouse loses its navigational abilities
2 models of memory consolidation
- standard model of memory consolidation
- info sent from neocortex areas associated with sensory areas to medial temporal lobe for processing
- synaptic consolidation
- post consolidation, hippocampus not necessary - multiple trace model of consolidation
- hippocampal involvement is continued
- multiple memory traces
- more sophisticated, long-term memories can be modified - useful for PTSD when you want to change unpleasant memories
memory is encoded…
….across a number of neurones
- eg. when you see somebody, its not just cell A firing, its components from cell A, B and C
- if a group of neurones stop working, the entire memory isn’t completely blocked out
trisynaptic circuit
- info flows from entorhinal cortex via performant path to the dentate gyrus
- mossy fibres originate from dentate gyrus and synapse upon pyramidal neurones in CA3 hippocampal regions
- axons from CA3 (Schaffer collaterals) synapse upon pyramidal neurones in CA1 hippocampal regions
what happens in the CA1 hippocampal region?
LTP
explain LTP
glutamate receptors located on CA1 neurones, ionotropic AMPA and NMDA receptors
- glutamate released and binds to post synaptic cell
- stimulation of AMPA receptors, Na+ influx
- activation of NMDA receptors, Na+ and Ca2+ influx
- calcium binds to calmodulin, calmodulin activates kinases
- increased responsivity of AMPA receptors, increased trafficking of AMPA receptors to post-synaptic membrane
- so more depolarisation occurs for a smaller glutamate release
how does LTP affect dendrites?
long lasting structural changes, dendritic spine growth
-when hippocampal receptors express AMPA receptors, the dendrites swell because there is an increase in physical membrane area
