1. Adult Neurogenesis
Challenging the dogma

2. Neurogenesis
The process by which new neurons are generated in the brain
Until the 1990’s, it was widely accepted that neurogenesis did not occur in the adult brain
“In the adult centers the nerve paths are something fixed, ended and immutable. Everything may die, nothing may be regenerated.”

3. Support for Adult Neurogenesis
3H- Thymidine Autoradiography
Technique used to identify proliferating cells
1960’s: Altman published a series of papers reporting thymidine autoradiographic evidence for new neurons
In the hippocampus , the olfactory bulb, and in the cerebral cortex of an adult rat
Neocortex of an adult cat
1970’s: Kaplan finds further evidence for the notion of neurogenesis
Cerebral cortex of adult rats
Mitosis in the brain of adult rhesus macaque monkeys

4. Opposition to Adult Neurogenesis
Pasko Rakic
Leading student of primate brain development
“All neurons of the rhesus monkey brain are generated during prenatal and postnatal life”
Eckenhoff and Rakic
Failed to find support for neurogenesis in the adult
Questioned the reports of adult neurogenesis in rats with the suggestion that they never stop growing

5. Altman’s Work is Vindicated
Avian Neurogenesis
Demonstration of neurogenesis in adult birds
New Techniques for Detecting Neurogenesis
New methods for labeling new cells
Regulation of Neurogenesis

6. Current Research Akers et. al. (2014)
Because not all experiences are ultimately remembered, it is likely that forgetting processes continuously clear stored hippocampal information
High levels of neurogenesis disrupt established hippocampus- dependent memories
Because neurogenesis reconfigures hippocampal circuits (thus reducing the ability of a given set of cues to reinvoke the same pattern of activity)