psych 124c: biological basis of memory

neurons

biological cells that specialize inthe transmission and retention of information

Dendrite (input)

receives input from other neurons

Soma (integration)

the cell body, which contains the nucleus and cellular machinery; integrates incoming signals

Axon (output)

transmits signals to other neurons

Glial cells

other types of brain cells that support neuronalhealth, guide development of nervous system, controlnutrient flow

action potentials

- Neurons process information by electric impulses that travel down the axon

- dendrites reaches a threshold level, the neuron "fires"

- all-or-none electrical impulse known as an "action potential"

- Action potential propagates along axon due to the entry and exit of ions through channels in the cell membrane (changes voltage)

myelin

- Fatty substance that coats and protects the axon

- Helps electrical signals travel quickly down axon

- Produced by glial cells

- Composes white matter pathways in brain

how neurons communicate

- when the action potential reaches the axon terminal, it causes the release of neurotransmitters into the synapse

- neurotransmitters bind to receptors on the post-synaptic dendrite and influence its activation state

neurotransmitters

- glutamate = excitation

- GABA = inhibition

- tell the brain what's important to remember

search for the engram

- physical unit of memory

- Karl Lashley: couldn't find it, assumed it didn't exist

optogenetics: turning memories on and off

- Neurons active during learning (e.g., an electrical shock) can be 'tagged' with proteins (opsins) that are sensitive to different wavelengths of light

- Stimulating those molecules with blue light will inhibit or excite those neurons

- can trigger expression of the learned behavior (e.g., fear response; freezing)

- ex: fear learning

structural

placeholder -> need to know?

hippocampus

- memory for unique episodes

- Contributes to acquisition, storage and retrieval (sometimes) of unique memories

- Glues together spatial, temporal, sensory info into a unified memory (context)

- critical for episodic memory

(does do some implicit eg statistical learning)

Patient HM

- removed HC

- severe anterograde amnesia (couldn't form new memories)

- working memory intact but new declarative not

- showed that memories were transferred to the cortex over time -> systems consolidation

- still good at implicit memory (mirror tracing)

amygdala

- role in encoding, storing, and retrieving highly emotional memories

- important for implicit (fear conditioning) and explicit memory

olfaction

- olfactory bulb has strong connections to areas involved in emotion and memory, like the amygdala

thalamus

- brain's central relay system

- connects important regions, including those related to memory

- sensory info comes there first, then cortex

basal ganglia

- memories of habits or automatic skills

- stressed -> increase in BG behavior. behavior may become more habitual

destination for most memories

cortex, not hippocampus