L60 Memory Systems + use lecture slides for LTP etc. (DENSE) Flashcards
what are methods used to study memory?
-behavioral tests (recognition, recall, relearning studies)
-functional organization of memory and attention:
(pharmacological mod, PET, fMRI, MEG)
what function does sleep play in memory?
- recently acquired, non-declaractive memories (procedural, motor learning etc.)
- facilitates rapid processing of declarative hippocampus-mediate memory (EXAM PREP!)
- protects declarative memories from any interferences (EXAM PREP)
when might stress be facilitating learning and memory processing?
- when stress is experienced IN THE CONTEXT AND AROUND THE TIME OF THE EVENT that needs to be remembered (EXAM PREP)
- stress hormones (corticosteroids) and NT released within the cortex of a learning experience induce FOCUSED ATTENTION AND IMPROVES MEMORY of relevant info. Their actions exert on the same circuits as those activated by the situation. (EXAM PREP)
Define declarative memory
conscious memory for facts, places and events
define non-declarative (procedural) memory
subconscious memory for skills, habits, emotional responses and some reflexes
what is the difference between STM and LTM?
new sensory info is processed into INTERMEDIATE MEMORY for several seconds then into STM
depending on the perceived importance, the info may be consolidated into LTM (for days/years)
define amnesiac
lack the ability to add to their declarative memory stores (episodic or semantic)
they can still drive a car or ride a bike (non-declarative - procedural)
define retrograde amnesia
loss of memory of past events before trauma
define anterograde amnesia
inability to form new memories following trauma and can only remember the past
what 2 types of amnesia make up transient amnesia?
retrograde
anterograde
what does psychogenic/dissociative amnesia stem from and what does it primarily effect?
steam from emotional shock or trauma
limbic system
what is the role of the amygdala in the emotion-memory interaction?
- calculates the emotional significance of events
- alerting us to notice emotionally significant events even when we’re not paying attention
- particularly keyed to negative experiences
what is the role of the cerebellum in the emotion-memory interaction?
- motor coordination skills
- remembering strong emotions
- consolidation of long-term memories of fear
what is the role of the prefrontal cortex in the emotion-memory interaction?
- influenced by a combination of mood state and cognitive task, but not by either one alone
- dorsolateral prefrontal cortex is more active when the participants were surprised by unexpected responses
*like if Tula fell down in the middle of lecture
where are long term memories processed?
hippocampus
where are long term memories stored?
cortical association areas
Describe engram
- memory trace/pattern of neuronal firing
- neural network or fragment of memory in a cluster of neurons connected together + possibly to activate at the same time (transiently or repeatedly)
in order to have a memory trace stored as an engram, it involves..?
- strengthening (repeated stimulus) of the synaptic contacts
- morphological changes (shape of spines etc.)
- altered number of synapses
the induced pattern of altered synaptic efficacy is by its nature ____ lasting
long
The retrieval of a whole specific memory can later be obtained by activating only ____ of the components of the memory (e.g. sound, smell, object)
one
what are the 2 types of memory retrieval
- associative retrieval
- strategic retrieval
describe associative retrieval
a cue automatically triggers an experience of remembering
describe strategic retrieval
a deliberate (often conscious) search of memory
what does higher recall involve?
elaborative encoding – integration of NEW info with what you already know…
Memories are records of how we _____ experienced events, not replicas of the events themselves => modified & forgotten incidents
subjectively
what are the types/diversity of engrams?
motor and visual, phonological engrams, etc.
Areas for facts, events, language and places
+ emotional content of our memories
where are engrams located?
-Primary sensory areas (primary visual and auditory cortex, somatosensory cortex)
-Association areas in neocortex
-Medial temporal lobes
-processing in the hippocampal formation
-back to the association areas for consolidation
in memory
What happens with removal of the amygdala, uncut and most of hippocampus in order to tx epilepsy?
- Retained IQ, language, long term memory and ability learn new skills (procedural memory)
- Lost ability to make new memories (immediate/short→long term impairment)
what happens with a lesion to the thalamus, medial temporal lobe, and maxillary bodies from a fencing sword going up the nose?
- Suffered anterograde amnesia
- Retained his IQ, language, procedural skill learning and 2yrs worth of long term memory
What happens with a stroke/TIA that resulted in lesions to the hippocampus suffering marked loss of CA1 neurons?
- Suffered from anterograde amnesia and unable to form new declarative memories
- IQ, memories, & cognitive ability remained intact
All new sensory information destined for long-
term storage in declarative memory is
processed through the _____.
hippocampal formation
describe the hippocampal formation
3 layered region of the cortex in the medial temporal lobe which contains the
- dentate gyrus
- hippocampus
- subiculum
the fornix is the main tract between the ______ and the _____, both which are critical in EPISODIC memory
medial temporal lobe
medial diencephalon
what is damage to the fornix associated with
amnesia
atrophy to surrounding structures
what is associated with higher micro structural integrity of the fornix?
better RECOLLECTION MEMORY
what would a small lesion in the hippocampus at the CA1 area affect?
AMPAR mediated LTP in CA1 pyramidal neurons
the hippocampus shows synaptic ____
plasticity
What is LTP in the hippocampus?
- When CA1 is excited by CA3 impulse trains at high frequencies (100/s), the excitatory synapse undergoes a long lasting increase in synaptic efficiency called long-term potentiation (LTP)
- The potentiation takes place in glutamatergic synapses on dendritic spines in the CA1 neuron
- This long term potentiation is caused by an increase sensitivity to glutamate via insertion of new AMPA receptors
- Additionally, due to the formation of new dendritic spines between CA3 and CA1, the increased number of synapses facilitates an increased responsiveness to synapses from CA3 to CA1
what is the LTP directly caused by?
postsynaptic changes in CA1 neurons
what happens when only a single presynaptic impulse is generated as opposed to a train of impulses?
-A single presynaptic impulse can open the AMPA receptors but the NMDA’s remain blocked by the resident Mg2+ ion
Note - when a train of impulses arrive, it can open the NMDA channel and allows Ca2+ ions to enter
-These Ca2+ ions leads to activation of kinases which leads to ↑AMPA receptors and eventual LTP
what does a ride in intracellular Ca2+ cause activation of?
2 protein kinases
- protein kinase C
- calcium-calmodulin-dependent protein kinase II (CAMKII)
what is hippocampal LTD?
- When CA1 is excited by CA3 impulse trains at low frequencies (1/s), the excitatory synapse undergoes a large persistent fall in synaptic efficiency called long-term depression (LTD)
- Thus, the same synapses showing LTP under intense stimulation will exhibit LTD under weak stimulation
c. The use of _____ receptors is necessary for both LTP and LTD the difference is calcium concentration
NMDA
*the amount of NMDA activation dictates [Ca2+]I thus a direct influence on synaptic strength
what regulates synaptic plasticity?
calcium
High Frequency Stimulation – LTP
-Induces large rise in [Ca2+]I which activates protein kinase who phosphorylates synaptic proteins (including AMPA receptors) leading to LTP
Low Frequency Stimulation – LTD
-Induces very small rises in [Ca ]I which activateds protein phosphatase which dephosphorylates
synaptic protens (including AMPA receptors) leading to LTD
what are the three major anatomical sites with functional synaptic connections to play a role in non-declarative memory?
- Supplemental & PremotorCortex
- Striatum (in the basal ganglia)
- Cerebellum
what are the sole output cells of the cerebellar cortex?
purkinje cells
Purkinje cell receives two major excitatory inputs from?
- Parallel Fiber→ found traversing the outer molecular layer and sends an input
- Climbing fiber→ makes several hundred synapses on the Purkinje’s dendrites
LTD Occurs only in _____ that are activated at the same time as the climbing fibers.
parallel fibers
If the parallel fiber is stimulated alone, it will NOT exhibit this LTD plasticity
what is the mechanism of LTD in the cerebellum?
- Climbing fiber activation strongly depolarized the purkinje cell dendrite which leads to the activation of voltage-gated Ca2+ channels
- Parallel fiber activation leads to AMPA activation and subsequent Na+ influx
- Parallel fiber activation also leads to stimulation of metabotropic receptors to eventually generate PKC
- PKC then phosphorylates the AMPA receptor and causes them to be internalized where it is this reduction of AMPA channels that cause the decreased sensitivity to glutamate and consequently LTD
in the hippocampus, what is the subunit used in LTP and LTD?
GluR1
in the cerebellum, what is the subunit used in LTP and LTD?
GluR2
in the hippocampus, phosphorylation is associated with?
LTP
in the cerebellum, phosphorylation is associated with?
LTD
what receptor is common to both the cerebellum and the hippocampus?
ionotrophic AMPA receptor
Describe Korsakoff Syndrome
- Occurring in chronic alcoholics with Thiamine deficiency
- Atrophy of dorsomedial thalamus and mammillar bodies
- Exhibit confusion, confabulation and severe memory impairment
a. Anterograde amnesia and severe retrograde amnesia prob due to damage to thalamus and hippocampus 4. May also exhibit lesions in neocortex, cerebellum and brainstem
desrcribe ECT
- Employed to treat severe cases of clinical depression which electrically induces seizure
- This is based on epileptics who are also depressed and showed marked improvement in depression following a
seizure - ECT may cause anterograde amnesia dating back several years but usually subsides a few months post-treatment
describe the effects of neurotoxins from dinoflagellate pfiesteria piscicda
- This toxin released into the water can cause confusion, ↓concentration, disorientation and severe memory loss
- Contact may be inhaling or direct contact with the skin