COGNITIVE SCIENCE 17

Can You Remember My Name?

Part 2 Jaime A. Pineda, Ph.D.

HIPPO CAMPUS

Hippocampus: The Seahorse

Surrounding areas of hippocampus

(Clark, 2006)Perirhinal, Entorhinal and Parahippocampal Cortices

Hippocampus Malfunctions

• Severe anterograde amnesia

• Mild retrograde amnesia

• Problems navigating space

• Seizures

• Early Alzheimer’s Disease

Hippocampus Functions

• Consolidation of STM to LTM

• Spatial and contextual memory

• Episodic memory

• Declarative memory

• Detection of novel stimuli

• Neurogenesis

  

Spatial Navigation

Time as London taxi driverV

olu

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of h

ipp

ocam

pu

s Spatial Navigation (cont.)

Age Differences in Maintenance Processes

600

800

1000

1200

1400

Rea

ctio

n T

ime

Memory Load

OlderYounger

Age differences increase with increasing memory set size

(Anders, Fozard & Lillyquist, 1972)

L R L R

Rypma, Prabhakaran, Desmond, & Gabrieli, 2001Psychology and Aging

Parahippocampus Hippocampus

Entorhinal cortex

Unimodal and polymodal association areas (frontal,

temporal, and parietal lobes)

Postrhinalcortex

Perirhinalcortex

DGCA3

SUBCA1

Trace Link

Hippocampal model

DG CA3 CA1

Entorhinal cortex

• Relating hippocampal structure to episodic memory function

• Mode shifting between storage and retrieval through novelty detection

• Population dynamics

• Relates parahippocampal structure to episodic memory function

• Sensory integration• ‘Object’ & ‘Context’ input• Retrieval mechanisms

– free recall

– cued recall

– recognition

Parahippocampal model

Hippocampus

Entorhinal cortex

Unimodal and polymodal association areas (frontal,

temporal, and parietal lobes)

Postrhinalcortex

Perirhinalcortex

Dentate gyrus

CA3

CA1subiculum

Trisynaptic Circuit

Circuit of Hippocampus Proper

Fimbria fornix (to mammillary bodies)

Hippocampus Cells

Pyramidal Cells

Place cells inhippocampusmap out the environment

Place cells respond as a function of external cues

Activity-Dependent Synaptic Plasticity

• Short-term plasticities– Facilitation (paired pulse facilitation):

100-200 ms; increased Ca++ increased p(NT release)

– Post-tetanic potentiation: 5-10 sec– Depression: hundreds of ms – few

minutes; caused by repetitive stimulation causing a decrease in p(NT release).

Activity-Dependent Synaptic Plasticity (cont.)

• Long-term plasticities– Short-term potentiation/depression– Long-term potentiation/depression

LTP is a persistent increase in synaptic efficacy that can be rapidly induced

Bliss and Lomo, 1973

NMDA Receptor• “Detects” simultaneous events

(“AND” gate)

• Gated by combination of voltage and ligand

– Glu + Gly opens channel to Ca ++,

– Magnesium (Mg++) block removed by membrane depolarization

• Mediates learning and memory via LTP (long term potentiation)

– Involved in process of addiction; behavioral sensitization, and drug craving

Learning Induced Changes in Dendrites

Effects of Increased NMDA Receptors