Learning and adult neurogenesis

Modulating factors

Physical activity

increase proliferation

Enriched environment

Stress

decreases proliferation

Mouse specificities

strain

species

age

sex

Training protocols

Fewer training trials associated with enhanced cell survival.

More training trials associated with no effect or decreases in survival.

This relationship does not extend itself to training with all types of tasks.

Method uses

BrdU labeling

Confounding factors

Does also detect DNA repair

Changes in integrity blood brain barrier may influence number of cells labeled

Dilution of label due to cell division

Overestimation

Underestimation

Timing of the labelling

Timing should be immediately before or within hours after testing

Subjects should be treated with the tracer and killed within 24 hours (before end of complete cell cycle)

Age of the new cells at time of learning

Young newborn cells (1 week) survival seems to be enhanced by learning.

Older newborn cells survival seems to decrease by learning.

Pastalkova target paper

Does not seem to link to the topic

Types of studies

Studies that correlate number new neurons with learning abilities

Available evidence is incomplete and mixed. Both evidence for and against role neurogenesis in learning.

Studies that examine influence of learning on number new neurons

Mixed and incomplete evidence, due to lack of knowledge of mechanisms of these new cells and varying protocols.

Effect of new neuron depletion on learning and memory

Antimitotic drugs

Can induce nonspecific effects

Timing and duration of neuron depletion may be a critical factor in determining learning deficits.

irradiation

2 Regions

the subgranular zone, dentate gyrus

subventricular zone, lateral ventricles, forebrain

Subparts

Proliferation

Survival

Gould target paper

r

Task 4: Adult neurogenesisEvidence has accumulated suggesting a relationship between newly born cells (neurogensis) in the hippocampus and various types of learning and memory. New neurons in the DG:- Become synaptically integrated- Attain morphological and biochemical characteristics of neurons- Generate action potentialsDo newly born cells in the dentate gyrus participate in learning and memory?

thymidine analog bromodeoxyuridine

Injected one week before training

Associative learning tasks

Hippocampus-dependent

Trace protocol eyeblink response conditioning

Spatial navigation learning Morris water maze

Hippocampus-independent

Delay protocol eyeblink response conditioning

Cue training Morris water maze

Results

Learning of the hippocampus-dependent tasks, increased the number of BrdU-labeled cells in the dentate gyrus, compared to naive controls.

The majority of new hippocampal cells were located in the granule cell layer

Exposure to similar environmental conditions had no effect on the number of BrdU-labeled cells in the dentate gyrus.

Likely that increased number of cells is caused by enhanced survival, not proliferation. = significant differences among groups of pyknotic cells in subgranular zone.

Effect on proliferation checked = BrdU injection during training. = No difference number of cells in conditioned animals and controls