Download Long-term memory

Memory
Human Neurobology 217
Jana Vukovic
[email protected]
Key points:
• Famous cases of memory deficit
• Brain structures involved – hippocampus
• Circuitry of memory – Papez Circuit
• synapse strengthening and long-term
potentiation (LTP)
What is memory?
• Memory is defined as the acquisition, storage,
and retrieval of information.
• All animals learn things from their interaction
with the environment
• Human brain forms memories more effectively
than others
• Maximum behavioural flexibility and most
efficiently adaptation to environment.
Amnesias = memory disorder
Retrograde amnesia
Anterograde amnesia
Cannot remember
events prior to
brain damage
Cannot later remember
events that occur
after brain damage
Brain
damage
occurs
time
HM & NA
• Which brain structures were removed from HM’s brain?
– Hippocampus, hippocampal gyrus, amygdala, uncus were removed
on both sides
• Which brain structures are damaged in NA?
– Thalamus and medial temporal lobe, mammilary bodies missing on
both sides
• Can HM and NA form new long-term memories (declarative)?
– NO.
• Can HM and NA learn new skills (procedural)?
– YES.
• What kind of amnesia do HM and NA have?
– Sever anterograde amnesia.
NA
• Korsakoff's syndrome:
– Found mostly in alcoholics who get most of their calories
from alcohol and become vitamin deficient (thiamine
deficiency)
– Damages mammilary bodies and other nearby parts of
the hypothalamus and thalamus
– This damage produces an amnesia similar to the type of
NA and HM (sever anterograde amnesia)
• Altzheimer’s disease:
– Loss of neurons in hippocampal and prefrontal cortex
produce first signs of memory loss.
• Long-term memories are biologically
different from short-term memories
• Long-term memories are stored
throughout the brain, but the hippocampus
is necessary for the information to reach
long-term storage.
Long-term memory
Declarative Memory
(explicit)
Remembering Knowing facts
events
(semantic m.)
(episodic m.)
Hippocampus
Nearby cortical areas,
diencephalon
Procedural Memory
(implicit)
Skills and Emotional Conditioned
habits association reflexes
Striatum amygdala cerebellum
Motor areas
of cortex
cerebellum
Hippocampus
• Essential for declarative
memory
• Cylindrical structure
• Longitudinal axis
surround thalamus
Out put from hippocampus
Prefrontal
cortex
Association
cortex
Cingulate gyrus
Anterior
Thalamic
nuclei
Mammillo
thalamic
tract
Mamillary
body
Hypothalamus
fornix Hippocampal
formation
Amygdala
Strengthening of synapses
• Long-term potentiation (LTP) is the long-lasting
strengthening of the connection between two neurons
• can last from hours to days, months, and years.
Long-term potentiation of synapses
• Hippocampal slice preparation to study LTP
• single stimulation to input path
• measure hippocampal response baseline
• Give train of stimulation to input path
• Again give single stimulation to input path
• hippocampus response is larger (potentiated)
• Give single stimulation a week later
• Hippocampus response still potentiated (long term
potentiation)
Synapses are strengthened
More dendritic spines on dendrites
where new synapses are made
Dendritic spines from a
cerebellar Purkinje cell, drawn by
Cajal (Ramón y Cajal, 1899b).
Long-term potentiation
Only strong stimulus will dislodge Mg2+ from the NMDA receptor
Exercise and trophic factor production in the adult brain
Describe Papez circuit?
Last Slide