our report in BioPsych.. this ppt is incomplete since the first part of the topic was not included here. i have uploaded our documents and presentations because i don't want to have it deleted.. these files can still be usefull to me and to others. i hope this can help.. book: BioPsych author: J.P. Pinel

1. Cil Flores
Regina Munoz
Kim Ocana

2.  Monkeys with bilateral medial temporal
lobectomies have major problems forming
long-term memories for objects encountered
in the delayed nonmatching-to-sample test.

4.  Intact , well-trained monkeys performed
correctly on about 90% of delayed
nonmatching-to-sample trials when the
retention intervals were a few minutes or less.
 In contrast, monkeys with bilateral medial
temporal lobe lesions had major object-
recognition deficits.

5. 100
80
60
Medial temporal lobe
40 lesions
Normal controls
20
0
8 15 1 minute 10
seconds seconds minutes

6.  The development of the delayed nonmatching-to-
sample test for monkeys provided a means of
testing the assumptions that the amnesia resulting
from medial temporal lobe damage is entirely the
consequence of hippocampal damage.

7. Aspiration lesions of
the hippocampus in
monkeys and rats.
Because of differences
in the size and
location of the
hippocampus in
monkeys and in
rats, hippocampectom
y typically involves the
removal of large
amounts of rhinal
cortex in
monkeys, but not in
rats.

8.  Mumby box
 David Mumby
 Delayed nonmatching-to-sample test for rats
 It was assumed that rats could not perform a task
as complex as that required for the delayed
nonmatching-to-sample test.
Combined bilateral lesions of rats’
hippocampus, amgdala, & rhinal cortex produce
major retention deficits at all but the shortest
retention intervals.

10.  Hippocampal lesions consistently disrupt the
performance of tasks that involve the
memory for spatial location.
 Morris water maze test
◦ Rats with hippocampal lesions learn the task with
great difficulty.
 Radial arm maze test
◦ Intact rats readily learn to visit only those that
contain food, without visiting the same arm more
than once each day.

11.  Radial arm maze test
◦ Reference memory-memory for the general
principles and skills that are required to perform a
task
◦ Ability to visit only the baited arms of the radial arm
maze.
◦ Working memory-temporary memory that is
necessary for the successful performance of a task
on which one is currently working.
◦ Ability to refrain from visiting an arm more than
once in a given day
◦ Rats with hippocampal lesions display major
deficits on both ref. & working memory.

12.  Place cells
◦ Neurons that respond only when a subject is in
specific locations.
◦ By placing a rat in an ambiguous situation in a
familiar test environment, it is possible to
determine whether the rat thinks it is from the
route that it takes to get to the location in the
environment where it has previously been rewarded

13.  Species of birds that
remember where
they store seeds have
larger
hippocampuses than
birds that do not
store
seeds, supporting
the idea that
hippocampus is
important for spatial
memory in many, if
not all, species.

14.  Experiment with humans in virtual-reality
towns (show activity in hippocampus using
positron emission tomography, PET) and with
taxi drivers (bigger hippocampuses measured
with magnetic resonance imaging, MRI) also
support this idea.

15.  Cognitive map theory
◦ O’Keefe and Nadel
◦ There are several systems in the brain that
specializes in the memory for different kinds of
information, and the specific function of the
hippocampus is the storage of memories for spatial
location.

16. Brown and Aggleton
Theory of the role of hippocampus in object
recognition that emphasizes its relation to the
perirhinal cortex.
◦ Perirheral cortex, not the hippocampus, plays a key
role in most object-recognition tasks.

17.  Configural association memory
◦ Based on the premise that spatial memory is one
specific manifestation of the hippocampus’s more
general function.
◦ Hippocampus plays a role in the retention of the
behavioral significance of combinations of
stimuli, but not of individual stimuli.

18.  Inferotemporal Cortex
◦ The cortex of the inferior temporal lobe
◦ Involved in the perception of objects, it is thought
to participate, in concert with perirhinal cortex, in
storing memories of visual paterns.

19.  Amygdala
◦ Plays a role in memory for experiences with
emotional significance.
◦ Rats with amygdalar lesions, unlike intact rats, do
not respond with fear to a neutral stimulus that has
been repeatedly followed y electric foot shocks.

20.  Prefrontal Cortex
◦ The area of frontal cortex anterior to motor cortex
◦ Are not grossly amnesic; they often display no
deficits at all on conventional tests of memory.
Two memory abilities that are often lost by patients
with large prefrontal lesion
 deficit in memory for the temporal order of
events, even when they remember the events
themselves
 Deficits in working memory- the ability to maintain
relevant memories while a task is being completed.

21.  Cerebellum
◦ Thought to participate in the storage of memories
of learned sensorimotor skills through its various
neuroplastic mechanisms
 Striatum
◦ Thought to store memories for consistent
relationships between stimuli and responses- the
type of memories that develop incremental over
many trials.

22.  What is happening within the brain structures
involved in memory?
 The efficiency of synaptic transmission were
the basis of long-term memory- Hebb
 Long-Term Potentiation (LTP) - synapses are
effectively made stronger by repeated
stimulation

23.  Hebb hypothesized that consistent with the
synaptic changes are the neural basis of
learning and memory
 LTP can last for many weeks after multiple
stimulations
 It is developed only if the firing of presynaptic
neuron is followed by the firing of the
postsynaptic neuron.
 Hebb’s Postulate for learning- The Co-
occurrence is necessary for learning and
memory

24. The idea that LTP is related to the neural
mechanisms of learning and memory has
some several observations:
(1) Elicited by levels of stimulation that mimic
normal neural activity
(2) LTP effects greatest in brain areas involved
in learning and memory
(3) Learning can produce LTP-like changes
(4) Drugs that impact learning often have
parallel effects on LTP

25.  All of the evidence is indirect that supports a
role of LTP in learning and Memory
 Has three part process:
1. Induction (learning),
2. maintenance (memory) and
3. expression (recall)

26.  Usually studied at synapses at which NMDA
receptor is prominent.
 NMDA receptor is a receptor for glutamate
which is the main excitatory neurotransmitter
of the brain.
 NMDA receptors do not respond maximally
unless glutamate binds and the neuron is
already depolarized
 Calcium channels do not open fully unless
both conditions are met

27.  Learning Calcium influx only occurs if there is
the co-occurrence that is needed for
LTP, leading to the binding of glutamate at an
NMDA receptor that is already depolarized
 Calcium influx may activate protein kinases
that induces changes causing LTP

28.  The maintenance and expression of LTP
involve changes in both presynaptic and
postsynaptic neurons.
 Only those synapses that were depolarized
before high-frequency stimulation were
involved in LTP
 The maintenance of LTP involves structural
changes which depend on protein synthesis

29.  The discovery of structural changes in
neurons following the induction of LTP
stimulated a search for a mechanism by
which neuron’s activity could change its
structure which led to the discovery of
transcription factors.
 Nitric oxide synthesized in postsynaptic
neurons in response to calcium influx may
diffuse back to presynaptic neurons
Structural changes are now a well-established
consequence of LTP