Study Guides (299,459)
CA (140,971)
York (11,259)
PSYC (1,268)
Final

PSYC 3265 Study Guide - Final Guide: Animal Testing On Rodents, Neocortex, Entorhinal Cortex

24 pages94 viewsFall 2015

Department
Psychology
Course Code
PSYC 3265
Professor
Norman Park
Study Guide
Final

This preview shows pages 1-3. to view the full 24 pages of the document.
Retrieval 6:00
MTL Hippocampal System
- w/in hippocampus: sub-fields! Hippocampus and para-hippocampal cortex surrounding it
- hippocampus next to amygdala
- hippocampus well-suited for formation, storage and retrieval of memories! b/c it represents a closed
circuit. Info keeps flowing, processed, elaborated on over and over. Intricate sub-connections w/in
hippocampus to allow memories to be re-activated at retrieval
Hippocampal Formation
- Hippocampus proper
CA1, CA2, CA3, CA4 subfields *distinguished by cellular structure and connectivity
CA1 particularly vulnerable to damage from hypoxia (loss of O2 to the brain, can be from cardiac
arrest)
- Dentate gyrus:
narrow, concave, wraps around CA4 subfield.
- Subiculum
continuation of CA1 subfield
connects to entorhinal cortex hippocampus and back *closed circuit
- entorhinal neurons (major input to hippocampus) dendate gyrus CA3 CA1 subiculum AND back
around = entorhinal cortex *perferant pathways
- another pathway that exits the hippocampus via the fornix (another major output from the hippocampus
that leads to other brain areas/structures. Bundle of axon tracts that leave hippocampus and send info to
the thalamus, also info from mammillary bodies hypothalamus PFC)
- one pathway for remembering ANOTHER familiarity
- Schaeffer collaterals: auto-associative, allows for info to reverberate w/in the CA3 sub-fields pattern
completion. CA3 related to retrieval, complete memory of an event based on some cues AND info
continually processed in a loop w/in that 1 sub-field
Major input
- receiving info from all major associative neo-cortex areas = association cortex in frontal, parieto-occipital,
and temporal lobes (lateral regions)
- relayed from perirhinal and parahippocampal cortices to entorhinal cortex into the hippocampus
Major output
- Subiculum projects to entorhinal cortex and info flows right back out to association regions *info
elaborated on in the hippocampus, then sent out to the regions that were involved in the initial encoding of
an episode
- same regions involved in initial perceiving/encoding, re-activated when exposed to a stimulus on
subsequent trials (implicit or explicit)
- Fornix projects to diencephalon *important when distinguished b/w recollection and familiarity
* maybe memory not a set of systems WM, encoding, retrieval … MAYBE should be processes same
principles that apply to all types of memories)
PS/PC
find more resources at oneclass.com
find more resources at oneclass.com
You're Reading a Preview

Unlock to view full version

Only half of the first page are available for preview. Some parts have been intentionally blurred.

- Pattern separation (PS, operate at encoding): process that parses similar events (share many features)
into more distinct, non-overlapping representations. Mechanism that allows us to code the details of similar
events as different.
- Pattern completion (PC, operate at time of retrieval): process that interacts with partial information to
reconstruct a complete event. A cue that allows you to retrieve the rest of the memory, based on partial info
re-construct the complete event.
- different processed map on to areas of the hippocampus!
Encoding versus Retrieval: PS versus PC
Current evidence
- initially predicted by Computational models
- Rodent studies = lesioned dendate gyrus, CA3 sub-field AND find the corresponding deficits
- High-resolution fMRI = look at activation at the level of sub-fields, see activation in dendate gyrus versus
CA. )ssues = cant separate CA and CA, see activation in sub-field versus dendate gyrus
- Aging and amnesia = patients w/ hippocampal damage show deficits. Hard to separate the 2 processes
- different processes believed to map onto different sub-fields w/in the hippocampus
- pattern separation occurs in the dendate gyrus. Info from entorhinal cortex, made more distinct here
- neurogenesis occurs in dendate gyrus. Dont know the function of those new neurons, we do know
there is new growth of cells
- pattern completion recurrent collaterals = takes a cue, and completes a pattern. Cue received w/in
region CA3, then can associate cues w/ other details of the event to complete the representation. Related to
retrieval
Patient BL
- 54 y.o. male, 13 years of education
- hypoxia-ischemia secondary to electrical injury/cardiac arrest loss of O2
- CA1 vulnerable to loss of O2, BUT his dendate gyrus specifically affected
- hard to form new memories, but not totally impaired
- average intelligence
- borderline-low average delayed recall
- intact performance on non-memory related cognitive tasks
- hard to differentiate b/w the 2
- dendate gyrus shrunken, all other parts equal in V
Pattern Seperation
- related to encoding
- MST / BPS-O (Stark et al., 2013, 2015)
Study: 128 images of common objects, incidental encoding based on semantic cues of the object
(indoor/outdoor)
Test: 192 images, 64 studied (green), 64 similar lures (blue), 64 foils (red) need to decide if they
studied it: old judgement has to be identical, new hadnt studied it, similar item similar to old
- Participants = B.L. and 20 age-matched controls (mean age, 52; 10 women)
Pattern Separation Results
- hypothesis: if a PS issue, should do well at old, reject new but trouble w/ similar b/c PS means
distinguishing items that overlap from study to test
- results: identical to control for identifying old AND no issue saying the new items are new. Deficit: lures
(decifit specific to PS)
Pattern Completion
- take a cue, use it to fill in the rest of an event that they studied. Want to show dendate gyrus specific to PS,
need to show BL doesnt have issue w/ PL. PC appears to occur at retrieval
- Study: 5 line drawings of scenes (and their fragmentes), followed by brief forced-choice recognition
find more resources at oneclass.com
find more resources at oneclass.com
You're Reading a Preview

Unlock to view full version

Only half of the first page are available for preview. Some parts have been intentionally blurred.

- Test: original 5 scenes learned items plus 5 new images new items. Need to describe the scene and
say how confident they are.
images presented at various levels of completeness
- Participants: B.L. and 17 age-matched controls (mean age, 51; 6 women
Pattern Completion Results
- when 100% complete scenes: can complete scenes for different levels of degradation at the same level of
controls, for the images he studies … PC intact
- when presented w/ new stimuli, hard to differentiate new and old items. Deficit specific to items that look
close to each other (reflects PS problem)
- PC seems intact dendate gyrus needed for PS (confusion b/w old and new iems) at encoding, not PC at
retrieval
Conclusion
- deficient pattern separation in B.L. provides compelling evidence that the dentate gyrus plays a critical
role in this process
- impaired pattern separation results in a bias towards pattern completion. Shows more PC than controls,
b/c PS doesnt happen
Encoding Versus Retrieval
Episodic encoding and binding in MTL
- MTL (contains hippocampus) believed to be responsible for binding features to an integrated memory
trace at encoding
receive highly processed input from many areas when an event is encoded
MTL then binds together input at encoding coherent memory trace
Retrieval and MTL
- at retrieval, a retrieval cue is encoded as part of the memory. Allows you to re-activate. w/ an obvious cue,
use MTL
- content addressable memory = retrieval cue often consists of some of input processed at encoding
- processed retrieval cue converges on MTL at the time of retrieval, triggers pattern completion (activates
other associations) within the hippocampus, which in turn reactivates information in neocortex (same
regions involved in initial perception at the time an event is experienced)
- MTL at the centre of encoding/retrieval, but a different role
- At encodingan event is processed by regions associated with different features of event; processed
information converges at hippocampus and features are bound
- At retrieval-- cue processed by regions associated with features of cue, and then converges to
hippocampus. Cue re-activates memory trace via hippocampus. if retrieval successful cue then connects
with memory trace projects to regions associated with memory.
- episodic retrieval: processes by which stored memory traces are retrieved
- assumed that retrieval produces subjective experience of consciously remembering the past. Feeling of
recollecting or re-experiencing all the details of the episode as if you experience it again
- episodic retrieval is assumed to depend on hippocampal regions that support pattern completion and
frontal lobes that support strategic retrieval cue that isnt effective or hard to access info, call on brain
regions in central executive i.e.. PFC, strategically retrieve info)
thus, there are multiple ways in which a retrieval cue can access memory trace, and partial
information may be enough to access memory trace
Episodic Retrieval
- evidence that hippocampus important for retrieval!
find more resources at oneclass.com
find more resources at oneclass.com
You're Reading a Preview

Unlock to view full version


Loved by over 2.2 million students

Over 90% improved by at least one letter grade.