Chapter 9: A Brain System for Declarative Memory

Question 1

What is the anatomy of the declarative memory system?

Answer 1

para-hippocampal region (PHR)

entorhinal cortex (EC)

hippocampus (HPC)

Question 2

What are the functional role of the different regions in the declarative memory system?

Answer 2

para-hippocampal region: delayed non-match to sample, continuous delayed non-match to sample

hippocampus: transitive inference

Question 3

What is the hierarchy of connections from neocortex to HPC and back?

Answer 3

cortico-hippocampal-cortical loop

when we isolate aspects we see lots of memory disorders

hippocampus receives the most highly processed info in the brain; send back its result of processing to the cortex

sensory modalities project through para-hippocampus on its way to the hippocampus

Question 4

What is the medial temporal lobe?

Answer 4

region “tucked in” in the most medial/mesial portion of the temporal lobe

limbic cortex: hippocampus and para-hippocampal cortices

Question 5

What are the four structures in the brain system for declarative memory?

Answer 5

Entorhinal cortex (EC)

Denti-gyrus (DG): granule cells

CA3: pyramidal cells, auto-associative, more likely to talk to each other than other cells

CA1: output structures of the hippocampus

Question 6

What is the tri-synaptic pathway?

Answer 6

intra MTL connections also form loop

EC –> DG –> CA3 –> CA1 –> sub-EC

Question 7

What is the short pathway in the MTL?

Answer 7

EC –> CA1

Question 8

What are the hippocampal outputs via the fimbria?

Answer 8

overlying axon swath

CA1 & Subiculum –> Deep EC –> Para-hippocampal cortices –> neocortex

main output

Question 9

What are the hippocampal outputs via the fornix?

Answer 9

subcortical axon bundle

CA1/CA3 –> subcortical structures

Question 10

What are the hippocampal outputs via direct connections?

Answer 10

CA1 –> prefrontal cortex

Question 11

What are the hippocampal inputs via the fornix?

Answer 11

subcortical axon bundle

neuromodulatory inputs – medial septum, diencephalic and brainstem inputs

by lesioning you severe modulators that activate the hippocampus

Question 12

What are the hippocampal inputs via the entorhinal cortex (EC-HPC)?

Answer 12

neocortical sensory inputs

long version: perforant pathway

short version: temporal ammonic

Question 13

What is the perforant pathway of hippocampal inputs via the entorhinal cortex?

Answer 13

long version

EC layer II –> DG –> CA3 –> CA1

Question 14

What is the temporal ammonic pathway of hippocampal inputs via the entorhinal cortex?

Answer 14

short version

EC layer III –> CA1

Question 15

What are the hippocampal inputs via the midline thalamus?

Answer 15

nucleus reuniens: RE

frontal cortex –> RE –> CA1

gets specific info from prefrontal

Question 16

What stage of processing is involved in the para-hippocampus?

Answer 16

representation and intermediate buffering of stimuli

high level of processing, but not as high as hippocampus

Question 17

What stage of processing is involved in the hippocampus?

Answer 17

comparison and association of stimuli to existing representational framework – hippocampus

Question 18

What is rationale for the difference in processing between the para-hippocampus and hippocampus?

Answer 18

HPC damage produces less (i.e., more specific) memory impairments than ParaHPC

no way for hippocampus to access info or report it back

Question 19

What was the affects of para-hippocampal and hippocampal lesions on DNMS performance?

Answer 19

hippocampus doesn’t do everything the para-hippocampal does

normal conditions and amygdala + hippocampal lesions performed the task fine

para-hippocampal lesions showed impairment

MTL damage impaired memory of particular object they were given after a long period of time (delay); will pick the novel one (correct) at short delays

Question 20

What was the affects of para-hippocampal and hippocampal lesions on continuous DNMS performance?

Answer 20

present odor, remember if it was presented on the trial that was before; if it gets a match, learn to not respond

hippocampal lesion doesn’t do anything
para-hippocampal lesion had specific and fundamental impairment

different types of para-hippocampal cell activity

different cells for different odors –> discrimination of odors

tracking process that is specific to the ability to retain info about the odor

Question 21

What do the different types of para-hippocampal cell activity in the continuous DNMS task tell us about its function?

Answer 21

para-hippocampus represents an individual stimulus

retains information for the delay

compute whether odor is a match or not

all of the processing in the para-hippocampus is supporting memory function

hippocampal regions do none of this

Question 22

What was the transitivity task performed by rats with para-hippocampal and hippocampal lesions?

Answer 22

task: dig or not dig in flavored sand

pick A w/ B, pick B w/ C, pick C w/ D, pick D w/ E

creates a hierarchy, A above all others, E below (never reward)

B vs. D –> need to know B sits above D, as learned through C (transitivity required)

A vs. E –> transitivity not required, E has never been rewarded

Question 23

What were the results of the transitivity task performed by rats with para-hippocampal and hippocampal lesions?

Answer 23

BC + CD premise pairs: all rats can learn the basic associations

AE end-anchored pair: all rats can remember that A is always rewarded and E never is

BD relational probe: normal can do, fornix and PHR lesions cannot

Question 24

Why can’t rats with para-hippocampal and hippocampal lesions perform the transitivity task?

Answer 24

the lesions don’t allow hippocampal communication to the para-hippocampus

para-hippocampal lesions give you hippocampal damage as well as specific memory damage