Adult Neurogenesis Challenging the dogma

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.”

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

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

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

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)