Chapter 9: A Brain System for Declarative Memory Flashcards
What is the anatomy of the declarative memory system?
para-hippocampal region (PHR)
entorhinal cortex (EC)
hippocampus (HPC)
What are the functional role of the different regions in the declarative memory system?
para-hippocampal region: delayed non-match to sample, continuous delayed non-match to sample
hippocampus: transitive inference
What is the hierarchy of connections from neocortex to HPC and back?
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
What is the medial temporal lobe?
region “tucked in” in the most medial/mesial portion of the temporal lobe
limbic cortex: hippocampus and para-hippocampal cortices
What are the four structures in the brain system for declarative memory?
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
What is the tri-synaptic pathway?
intra MTL connections also form loop
EC –> DG –> CA3 –> CA1 –> sub-EC
What is the short pathway in the MTL?
EC –> CA1
What are the hippocampal outputs via the fimbria?
overlying axon swath
CA1 & Subiculum –> Deep EC –> Para-hippocampal cortices –> neocortex
main output
What are the hippocampal outputs via the fornix?
subcortical axon bundle
CA1/CA3 –> subcortical structures
What are the hippocampal outputs via direct connections?
CA1 –> prefrontal cortex
What are the hippocampal inputs via the fornix?
subcortical axon bundle
neuromodulatory inputs – medial septum, diencephalic and brainstem inputs
by lesioning you severe modulators that activate the hippocampus
What are the hippocampal inputs via the entorhinal cortex (EC-HPC)?
neocortical sensory inputs
long version: perforant pathway
short version: temporal ammonic
What is the perforant pathway of hippocampal inputs via the entorhinal cortex?
long version
EC layer II –> DG –> CA3 –> CA1
What is the temporal ammonic pathway of hippocampal inputs via the entorhinal cortex?
short version
EC layer III –> CA1
What are the hippocampal inputs via the midline thalamus?
nucleus reuniens: RE
frontal cortex –> RE –> CA1
gets specific info from prefrontal
What stage of processing is involved in the para-hippocampus?
representation and intermediate buffering of stimuli
high level of processing, but not as high as hippocampus
What stage of processing is involved in the hippocampus?
comparison and association of stimuli to existing representational framework – hippocampus
What is rationale for the difference in processing between the para-hippocampus and hippocampus?
HPC damage produces less (i.e., more specific) memory impairments than ParaHPC
no way for hippocampus to access info or report it back
What was the affects of para-hippocampal and hippocampal lesions on DNMS performance?
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
What was the affects of para-hippocampal and hippocampal lesions on continuous DNMS performance?
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
What do the different types of para-hippocampal cell activity in the continuous DNMS task tell us about its function?
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
What was the transitivity task performed by rats with para-hippocampal and hippocampal lesions?
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
What were the results of the transitivity task performed by rats with para-hippocampal and hippocampal lesions?
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
Why can’t rats with para-hippocampal and hippocampal lesions perform the transitivity task?
the lesions don’t allow hippocampal communication to the para-hippocampus
para-hippocampal lesions give you hippocampal damage as well as specific memory damage
