Damage to or surgical removal of hippocampal formation has severe and very specific consequences
Memories established before lesion
New short-term (up to a few minutes) memories
Creation of new long-term explicit memories
Development of new long-lasting implicit memory
the medial temporal lobes can be assumed to be a major component involved in the formation of semantic and episodic long-term memories
working memory relys on medial temporal structures
lexical memory is dependent of the medial temporal structures
heavy impairment in certain spatial tasks provides further evidence for the association of the hippocampus with spatial memory (
What are the two types of memory?
EXPLICIT MEMORY:
Factual knowledge of people, places, things, and events, along with concepts derived from this knowledge
Explicit (declarative) memory is recalled by conscious effort, and can involve assembly and association of many pieces of information in different modalities
IMPLICIT MEMORY:
Acquired information on how to perform skills and on associations between stimuli and responses Implicit (nondeclarative)
memory is recalled unconsciously
Different regions of the brain are responsible for staged acquisition and storage of different types of memory
Where is Short-term memory (Working memory) located?
prefrontal cortex
Where is Long-term memory modulated?
– Modulated by hippocampus and amygdala, stored diffusely
What is the Hebb rule?
“Neurons that fire together get wired together.”
The hypothesis proposed by Donald Hebb that the cellular basis of learning involves strengthening of a synapse that is repeatedly active when the postsynaptic neuron fires.
"when an axon of cell A ... excite a cell B and repeatedly or 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 cells firing B, is increased" (Hebb, 1949)
What is Long-Term Potentiation (LTP)?
LTP is a candidate mechanism for Hebbian learning (synaptic plasticity)
LTP is a persistent increase in synaptic strength (as measured by the amplitude of the EPSP) that can be rapidly induced by brief neural activity
Where does Long-Term Potentiation (LTP) occur?
LTP has been found in mammalian neocortical regions, and in subcortical nuclei
LTP has also been found in the peripheral nervous system of mammals
LTP has mainly been studied in the hippocampus, a vital structure for memory
What Forms of synaptic plasticity exist?
Post-tetanic potentiation (PTP)
Short-term potentiation (STP)
Long-term potentiation (LTP)
Long-term depression (LTD)
depotentiation
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