7.2 and 7.3 Flashcards
Primacy effect
Higher memory performance for items at beginning of a list
Recency effect
Higher memory performance for items towards end of the list
Serial Position effect
Combines primacy effect and recency effect; we have higher memory performance for items towards beginning and end of lists than for items in the middle
Glanzer and Cunitz 1966
Recency effect is disrupted when there is a delay before recalling items
Hippocampal System
Hippocampus and neighboring structures in the medial temporal lobe
-quick formation of memories but lost easily; supports initial learning of arbitrary, new information
-one-shot loearning
Neocortex
Long-term memories are stored in the neocortex
-it takes a long time to cement memories in the neocortex but they are solid once there; the effects of experiences take time to accumulate
Complementary memory system
The hippocampal system and the neocortex form a complementary memory system
Reactivation
During retrieval of a memory, brain mechanisms that were involved in the initial perceptual and cognitive experiences show patterns of activity similar to what accurred during initial encoding
The subsequent memory effect/paradigm
Brain activity is higher for remembered items than for forgotten ones at the time of initial encoding
Consolidation
The act of stabilizing memories
-synaptic consolidation and system consolidation
Synaptic Consolidation
Happens over seconds to hours
-form of long-term potentiation
-occurs when the second cell fires immediately after the first
-synapses are potentiated by creating new receptor sites-more NT can be released
Long-term potentiation
communication across a synapse strengthens future communication between the pre and post synaptic neurons
System Consolidation
Re-organization of brain circuits to store new memories
-occurs over weeks, months, and years
Hebbian learning/ Hebb’s Rule
cells that fire together wire together
Standard Model of Consolidation (for explicit memories)
Consolidation begins in the hippocampus and is slowly transferred to other parts of the cortex
-The hippocampus has the structure to work as an auto-associator; a particular type of network that “remembers” specific configurations
Consolidation and Multiple Trace Memory Model
-In initial state, cortical neurons are not active
-When learning something for the first time specific neurons will be activated in different areas of the cortex
-The hippocampus tracks which of these cells were active in each area
-The event/learning takes place repeatedly and the hippocampus continues tracking neurons active in each area
-With recall, memories are retrieved from the hippocampus and the hippocampus re-activates cortical patterns and we re-experience the event/learning/moment that was previously experienced
-With repeated recall, the different patterns are united
-Eventually the hippocampus is not needed anymore, these memories are stored in the cortex
Multiple Trace Theory and Distributed Code
We create multiple “traces” or associations of neurons when an event repeatedly takes place
-our final memory comes involves the associations of neurons that were present in all traces/exposures
Memory Retrieval
Reactivation of the brain regions involved during the initial encoding
Population coding
representation or coding by a group of neurons - information is represented as patterns across neurons and not within individual neurons alone
advantages of using patterns of activity across neurons: virtually limitless combinations of possible representations or objects, and therefore encoding memories
Sleep and consolidation (Louie and Wilson 2001)
REM sleep is essential for consolidation of memories of not just facts but also perceptual and motor skills
Experiment: Rat runs in a maze and finds treats; track the firing of place cells at specific locations in the maze
Findings: During REM sleep, patterns of neural activation across place cells corresponded with activity of the same cells while the rat was running the maze
Cognitive Map Theory
The hippocampus constructs a map of the environment, providing a basis for spatial memory and navigation
Hippocampus Place Cells
Fire when an individual is in a certain environmental location
-more allocentric representation
Entorhinal Cortex Grid Cells
Fire when the individual moves around around in space; tracks movement and positions
Head Direction Cells
Encode the direction of the rat’s head
Hippocampal volume and correlation with spatial navigation ability (Weisberg and Ekstrom 2021)
Larger hippocampal volumes in certain individuals (such as taxi drivers) may be driving a correlation but in the general population there is no correlation
Spatial Frameworks
A way of representing locations in reference to other points
Egocentric framework
Spatial relation of other objects to oneself
ie. turn right, turn left
-parietal cortex
Allocentric framework
Spatial relation of other objects with eachother
-hippocampus (place cells)
-objective location
View-point depended
Spatial memory is view-point dependent: it relies on egocentric representations
