Lecture 15 Memory Flashcards
(20 cards)
What were beliefs about memory before the case of HM?
- Memory was thought to be distributed throughout the cortex
- No specific brain region was believed to be dedicated to memory
What were beliefs about memory after the case of HM?
- Memory is a distinct cerebral function
- There are multiple types of memory processes
- Memory is separable from perceptual and cognitive abilities
- The medial temporal lobe is critical for memory
What brain structures were removed in HM’s surgery?
- Amygdala
- Most of both hippocampi
- Part of the parahippocampal gyrus
What were the effects of HM’s surgery on his memory?
- Severe anterograde amnesia (couldn’t form new declarative memories)
- Poor retrograde memory for recent years before surgery
- No significant change to personality, attention span, or verbal memory
Define retrograde amnesia
Impairment of memory for events prior to the brain injury
Define anterograde amnesia
Inability to form new memories after brain injury
What kind of memory did HM retain after his surgery?
- Procedural memory was intact
- Could learn new motor skills (e.g., mirror drawing)
- No conscious memory of having learned the task
What is declarative memory?
Conscious memory for facts and events (e.g., names, faces, stories)
What is procedural memory?
Non-declarative memory for skills and procedures (e.g., riding a bike)
What is the hippocampal formation composed of?
- Dentate gyrus
- Hippocampus (CA1 to CA3)
- Subiculum
- 齿状回
- 海马（CA1 至 CA3）
- 下托
What is the role of the hippocampal formation?
- Learning and consolidation of new information
- Supports relational memory (e.g., associating names with faces)
What types of tasks demonstrate the role of the hippocampus in relational memory?
Paired-associate learning tasks (e.g., name-face or word-object pairs)
What is Papez’s circuit, and what happens when it is damaged?
- Emotional experience and expresssion
- Declarative memory impairment, especially in hippocampus and anterior thalamic nuclei
- limbic system = papez circuit + amygdala
- Often implicated in Alzheimer’s disease
What is the amygdala’s role in memory?
- Supports memory for emotionally arousing experiences
- Lesions impair fear conditioning and memory for emotional events
What is the role of the frontal lobes in memory?
- Memory encoding and retrieval strategies
- Damage leads to impaired contextual memory (source, order), confabulation
How does the diencephalon 间脑 contribute to memory?
- Involves thalamus and hypothalamus
- Lesions cause various memory problems:
- Anterior and medial thalamus: amnesia
- MMT: episodic memory loss
- Dorsal medial nucleus: selection of memory
- Intralaminar nuclei: semantic and retrieval deficits
What is Hebb’s rule of synaptic plasticity?
“Neurons that fire together, wire together” — repeated activation strengthens synaptic connections
What is Long-Term Potentiation (LTP)?
- Improves the efficacy of the synapses
- increased or decrease neurotransmitter release or receptors number on post-synaptic membrane
- associated with glutamatergic synapses
- Occurs in hippocampus (CA1, dentate), entorhinal cortex, amygdala, prefrontal cortex
What are other forms of synaptic plasticity besides LTP?
Long-Term Depression (LTD): weakens synapses
Habituation: decreased response to repeated stimuli
Sensitization: increased response after a strong stimulus
What are the key memory-related findings from HM’s case?
- Temporal lobe, especially hippocampus, critical for declarative memory
- Procedural memory can remain intact
- Memory involves multiple brain structures (MTL, Papez’s, frontal lobes, diencephalon)
- Memory depends on synaptic plasticity mechanisms like LTP
