Understanding memory is crucial for both everyday life and various cognitive functions.
Outline
Key topics to study for the exam:
Working memory (Short-term memory)
Processes and types of Long-Term Memory (LTM)
Long-term explicit memory
Long-term implicit memory
Long-term potentiation
Amnesia
Working Memory
There are possibly two systems for working memory:
Spatial memory
Object memory
Visual Pathways:
Dorsal: Vision for action (parietal cortex)
Ventral: Vision for perception (temporal lobes)
Processes in Short-Term Memory (STM) and Long-Term Memory (LTM)
Encoding into STM:
Visual objects: Right prefrontal and parahippocampal cortex
Words: Left prefrontal and parahippocampal cortex
Consolidation to LTM:
Involves the medial temporal lobe and hippocampus.
Permanent memory storage may utilize the outermost layer of cortex (Layer I).
Retrieval involves attention (frontal areas) and makes memories plastic for modification, which is significant for PTSD therapy.
Explicit Memory
Types of Explicit Memory:
Episodic Memory: Specific events related to oneself.
Semantic Memory: General knowledge not tied to personal experience (e.g., recognizing friends).
Neural Substrates:
Temporal-frontal-lobes, predominantly in the ventral stream (temporal lobe, hippocampus, and rhinal cortex).
Long-Term Memory and the Hippocampus
Specifically relates to explicit memory (Episodic):
Spatial navigation: Evidence from Morris water maze experiments and studies of London taxi drivers and their hippocampal activation during spatial tasks.
Contextual Memory: Allows reconstruction of contexts from different references.
Long-Term Implicit Memory
Involves emotional memory (fear conditioning) regulated by the amygdala.
Damage to the amygdala impacts emotional memory but not other implicit/explicit forms.
Procedural Learning: Engages the basal ganglia, important in skills learning.
Procedural Memory and the Basal Ganglia
Comprises Striatum, Globus Pallidus, and Substantia Nigra.
Gradual habit learning through reinforcement.
Flexibility: Initially requires frontal cortex engagement, but becomes less flexible over time.
Long-Term Potentiation (LTP)
Involves glutamate receptors, particularly AMPA and NMDA:
NMDA receptor opens after depolarization, influenced by Magnesium ions.
Calcium influx through NMDA leads to CREB protein release, affecting gene expression for extended periods.
BDNF modulates these processes, promoting NMDA receptor activity.
Amnesia
Types:
Anterograde Amnesia: No new memories after the onset.
Retrograde Amnesia: Loss of memories before the amnesia event.
Severity of injury influences time-dependent retrograde amnesia.
HM Patient (Henry Molaison):
Severe anterograde and retrograde amnesia post-hippocampus removal.
Impaired explicit memory but intact implicit and working memory capabilities in certain contexts.