Learning & Memory: The neural substrate Flashcards
Procedural memory
- aka implicit, non-declarative and reflexive memory
- Motor skills and habits that are basically automatic b/c used so many times
- Anatomic substrates:
a. Cerebellum (motor skills)
b. Nucleus accumbens (non-motor skills, habits)
Declarative memory
-aka explicit memory
-Conscious recognition/recollection of learned facts and experiences
2 forms:
a. Episodic - memory of events
b. Semantic - memory of words, language and rules
Post-tetanic stimulation
- Brief, high-frequency discharge of presynaptic neuron which produces an increase in NT release that lasts ~60 seconds and increases probability of AP in post-synaptic cell
- Mechanism: High lvl of stimulation allows more Ca2+ to enter the pre-synaptic terminal than the Ca2+ ATPase can remove, causing more vesicles to fuse to the cell membrane and increased NT release
Long-Term Potentiation (LTP)
- Series of changes in pre- (increased NT release) and post-synaptic (increased response to NT release) neurons which leads to an increased response to the same NT release (NMDA receptors) and typically follows a strong stimulation
- Changes must last > 30-60 mins
- Associated w/ gene transcription changes mediated by cAMP response element binding protein (CREB) to trigger physical changes in neurons
Long-Term Potentiation (LTP): Post-synaptic neuron changes
- Increased Ca2+ entry into the post-synaptic cell –> binds calmodulin
- Ca2+-calmodulin triggers increase in adenylyl cyclase activity to increase cAMP lvls
- cAMP activates PKA which then phosphorylates AMPA receptor causing an increased Na+ influx in response to EAA –> more depolarization
Long-Term Potentiation (LTP): Pre-synaptic neuron changes
- Increased Ca2+ entry into post-synaptic cell –> binds calcineurin
- Ca2+-Calcineurin activates Nitric oxide synthase
- NOS converts Arginine –> citrulline + NO
- NO diffuses to the pre-synpatic cell and causes an increase in cGMP and increased NT release
Creating a declarative/explicit memory: Encoding
- Attending to new information (focus, attention)
- Linking new information to previously learned information
- Emotion major component b/c needs to have emotional value to remember it
Creating a declarative/explicit memory: Storage of information
- Temporary storage of information
- Anatomical substrates: hippocampus, parahippocampal cortex, prefrontal cortex
- Interconnections to neocortex and amygdala via nucleus basalis of Meynert (cholinergic projection, particular target of Alzheimer’s Disease)
- Physiological substrate = long-term potentiation
Anatomical substrates for short-term memory
- Hippocampus
- Parahippocampal cortex
- Prefrontal cortex
Creating a declarative/explicit memory: Consolidation
- Process of making a memory permanent via physical changes in synaptic structure
- Requires hippocampus, temporal lobes and Papez circuit
- Memory is repeatedly sent through Papez circuit to promote conditions required for long-term potentiation and neuronal plasticity to create new synapses in the associated regions of the brain involved in the memory (e.g. visual info stored in occipital lobe)
Consolidating memory from short- to long-term: Papez circuit
Hypothalamus/mammillary bodies (physical response to memory) –> anterior thalamus (sensory information coming in) –> cingulate cortex (emotion) –> hippocampus (short-term memory) –> hypothalamus/mammillary bodies
Creating a declarative/explicit memory: Retrieval
- Recalling or using a memory by bringing it into working memory
- Reassembling the long-term memory requires the neocortex, parahippocampal regions and the hippocampus:
1. Info related to each component of memory sent to parahippocampal regions
2. Components are then sent to hippocampus, from the parahippocampal cortex, for the memory to be “reconstructed”
3. Info travels back through the parahippocampus to cortex - Parahippocampus prolongs life of cortical “trace” of memory
4. Working memory uses retrieved memories
Working memory: Three-Component Model
- Phonological loop (Broca’s and Wernicke’s areas) - provide/interpret auditory information associated w/ memory (e.g. words, rule associated w/ event)
- Visuospatial loop (Occipital cortex, others) - provides/interprets visual information associated w/ memory
- Central executive (Prefrontal cortex) - directs/uses the information from the other two loops
Working memory: Three-Component Model - Anatomical substrate for Phonological loop
- Broca’s and Wernicke’s areas
- Provide/interpret auditory information associated w/ memory (e.g. words, rule associated w/ event)
Working memory: Three-Component Model - Anatomical substrate for Visuospatial loop
- Occipital cortex and other brain areas associated w/ vision
- Provides/interprets visual information associated w/ memory
