Midterm Flashcards
what is an ingram? what’s an example?
memories that are not learned by an individual in their life
- instinct, built-in adaptations inherited from one’s parents/lineage
- selected when environmental regularities are extremely regular (hyper-stable)
ex) sneezing
what is an engram?
memories that are learned by the individual
- require personal experience
- useful when one’s own experience is unique but still relevant to predicting one’s future (quickly changing environment)
ex) learning skills for a new job
what is an example of combining ingrams and engrams?
learning a language
- the capacity to learn a language is an ingram
- actually learning the language is an engram
how can you study learning and memory? how did Ebbinghaus contribute to this?
learning and memory processes cannot be observed directly, therefore must be inferred by observable behaviour
- Ebbinghaus developed the first scientific methods for assessing the acquisition and retention of a controlled experience
how did Ebbinghaus study “pure memory”?
required a methodology that would separate what the subject has learned from what the subject is being asked to remember
- so he invented the nonsense syllable (nuh, vag, boc)
- he was his only subject
what were Ebbinghaus’ research findings?
- test performance increased the more he practiced a given list
- retention performance was better when he spaced the repetition of a given list rather than when the list was repeated without a break between the learning trials
- Ebbinghaus’ Forgetting Curve
what does Ebbinghaus’ Forgetting Curve (first forgetting curve) tell us?
we forget over time in a non-linear way
- dramatic decrease in % recalled within the first hour, then stabilized but continued to decrease from hrs to days
(most forgetting occurs in the first hr, with progressively less forgetting as time goes on)
- best performance when test was given shortly after learning trial
what did the discovery of the forgetting curve lead to?
led to other scientists proposing theories underlying the structure of memory:
- single trace theory
- dual trace theory
what is the single trace theory?
the forgetting curve can be explained by assuming that the strength a single memory trace declines monotonically (non-linear) as a function of time between learning and the retention test
what is the dual trace theory?
the forgetting curve can be explained as the product of a rapidly acquired short-term trace that has a fast decay rate and a slowly established long-term trace that decays slowly
how did Golgi believe the nervous system was arranged?
NS is an exception to the cell theory, being formed not by independent cells but rather by a gigantic net (syncytium) -> continuous reticulum/network
- protoplasmic processes (dendrites) in contact w/ blood vessels and provide nutrients to the cell
- output end of neurons are continuous w/ each other and formed a reticulum
what were Ramon y Cajal’s 2 big ideas?
- neuron doctrine
- synaptic plasticity hypothesis
what is the neuron doctrine?
the idea that the brain is made of discrete cells called nerve cells, each delimited by an external membrane
- refuted the reticulum theory; neurons are truly independent genetically dervied units that are composed of dendrites, soma, and axon
- argued that axon endings were contiguous with dendrites but not continuous with them -> synapse
- basis of modern neuroscience -> neurons are physiological units that pas electrical current in one direction
what is the synaptic plasticity hypothesis?
the idea that the strength of a synaptic connection can be modified by experience
- certain experiences can strengthen a synapse, creating memories
what are grid cells? how do they work?
neurons located in the entorhinal cortex
- fire at regular intervals as an animal navigates an open area, allowing it to understand its position in space by storing and integrating info about location, distance, direction -> creates a grid/cognitive map
- respond to multiple spatial locations organized in a grid
where do grid cells send information?
place cells in the hippocampus
- active when an animal is in different locations, and the combination of activity in many place cells creates an internal map representing a particular environment
- fire at specific locations!
what are Hebbian cell assemblies?
diffuse circuits of connected neurons that develop to represent specific percepts or concepts -> structural changes in these make lasting memories possible
- Donald Hebb proposed that modified ensembles of neurons called cell assemblies could provide a substrate for memories
what is Hebb’s saying?
neurons that fire together, wire together
- how synaptic connections can be modified
- when an axon of cell A is near enough to excite a cell B and repeatedly/persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cell’s firing B, is increased
how are memories represented at the synaptic level?
the changes in connectivity among the collections of neurons responding to a specific experience
- changes are distributed through the neural systems engaged by the memory-producing event
- duration of the changes can be short-lived or relatively permanent, and the content of the memory will be determined by the specific sets of cell assemblies activated by the memory-producing experience
what is the Bliss and Lomo experiment that led to the discovery of LTP?
discovered LTP by stimulating (SE) the perforant path and recording (RE) in the dentate gyrus in the hpc of living rabbits
what was the method of Bliss and Lomo’s experiment?
- test stimulus: first applied a weak stimulus (WS) to the perforant path and measured synaptic activity
- then applied a strong stimulus (SS) to the perforant path
why is it important to start with a test stimulus?
- establishes a baseline
- helps determine if the inducing stimulus produced LTP, resulting in the test stimulus producing a larger response
what were the results of Bliss and Lomo’s experiment?
the SS produced an enduring increase in the synaptic response to the WS -> enhanced response = LTP
- SS potentiated the response to the WS and this potentiation lasted a relatively long time (several hrs)
what is the most common procedure for studying LTP?
in vitro preparation:
- places slices of hippocampal tissue in a recording chamber
- used to study LTP induced neurons in the CA1 region of the hpc
- done by stimulating the Schaffer collateral fibres and record field potentials from a RE placed in the CA1 region
what is the hippocampus? what does its pathology include? what are its structural correlates?
cortical structure responsible for memory consolidation
- pathology includes anterograde amnesia (inability to form new memories)
- part of the hippocampal formation, which includes the dentate gyrus, hippocampus, and subiculum
what is the trisynaptic organization of the hippocampus?
important in memory formation and LTP:
- neurons in the entorhinal cortex connect to the dentate gyrus (perforant path)
- neurons in the dentate gyrus connect to the CA3 region (mossy fibres)
- neurons in CA3 connect to neurons in the CA1 region (Schaffer collaterals)
where is the hippocampus? why is does this make it an important brain structure?
hpc is part of the medial temporal lobe system, where it is the central structure and works with adjacent regions (entorhinal ctx, perirhinal ctx, parahippocampal corticies)
- responsible for governing long-term memories
- acquiring new memories is a distinct, separable process from other cognitive abilities such as perception
where does LTP occur?
hpc -> suspected mechanism for memory formation
- synapses are fundamental units of storage in the brain
- Schaffer collaterals in hpc are most studied site of LTP
who has patient H.M.? how does this make the hpc an important structure?
had memory deficits, including anterograde amnesia (STM intact, LTM deficient)
- had bilateral MTL removal, which includes hpc
why is the hippocampus thought to be an important brain structure for memory?
- part of MTL
- LTP
- patient H.M.
what are the 3 dimensions of memory traces?
- duration (how long a memory lasts; divided into short-term and long-term)
- state
- vulnerability to disruption
what does “state” mean as a dimension of memory traces?
whether the memory is in an active or inactive state
- active state associated with STM, more prone to disruption
- inactive state associated with LTM, more resilient to disruption
what does “vulnerability to disruption” mean as a dimension of memory traces?
how susceptible the memory is to being lost or disrupted
- active, short-term memories are more vulnerable to disruption (rapid decay) vs inactive, long-term memories that are less vulnerable (slow decay)
what experiment explains how active traces are more prone to disruption? what were the results?
football player has 2 sets of experiences: E1 (before game) and E2 (just prior to head trauma)
- E1 memories are older than E2 memories; trauma produces amnesia for only E2 memories because they are still in an active state when trauma occurs
- E1 memories are not affected b/c they have achieved the inactive, long-term memory state
what can be interpreted from the football experiment?
- memories become more resistant to disruption as they age
- memories in the active state are more vulnerable to disruption than memories that have become inactive
what is the “Levels of Processing” theory for the creation of memory traces?
without encoding
- levels refer to levels of perceptual processing depth (not memory encoding)
- memory trace is understood as a byproduct of perceptual analysis and that trace persistence is a positive function of the depth to which the stimulus has been analyzed
what example factors can increase the depth of retention, according to the LOP theory?
- amount of attention devoted to a stimulus
- stimulus compatibility with the analyzing structures
- processing time available
- motivation
- stimulus salience
what is the “General Abstract Processing System” theory for the creation of memory traces?
with encoding; understanding episodic memory
- act of memory begins with encoding and ends with retrieval
- encoding is not the same thing as perceptual analysis (it is another process)
- perceptual analysis is necessary but not sufficient for memory trace formation
