Wellcome Trust International Senior Research Fellow Dr Sumantra Chattarji and his team at the National Centre for Biological Sciences in Bangalore, India, are studying how the wiring of the brain changes under stress. A better understanding of the cellular mechanisms that imprint emotional memories in our brains could lead to better treatments for severe anxiety or post-traumatic stress disorder.

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Stress intrigues memory researchers because of its contrasting impact on different types of memory, and opposite effects on different parts of the brain. Prolonged stress impairs recollection of facts and events, by causing damage to the hippocampus. By contrast, it greatly amplifies emotional memories, by enhancing the wiring of neuronal circuitry in the amygdala.

With collaborators in the USA, Dr Chattarji has begun to identify the biochemical and electrophysiological changes in single neurons that affect the hippocampus and amygdala – and, through them, mouse behaviour. Raising levels of the signalling chemical brain-derived neurotrophic factor, for example, can simultaneously heighten anxiety by strengthening connections in the amygdala, but reduce depressive symptoms by protecting the hippocampus.

The amygdala has received less attention than the hippocampus, but Dr Chattarji's research has identified stress-induced changes in the amygdala that underlie sensitivity to emotional experience. Ultimately, this work will provide a clearer picture of the neural changes that leave people susceptible to flashbacks of highly stressful events, and lead to new approaches to understanding and treating conditions such as stress-induced depression and chronic anxiety.

Image: Dr Sumantra Chattarji, courtesy of Manoj Sudhakaran

External links

• Mitra R et al. Stress duration modulates the spatiotemporal patterns of spine formation in the basolateral amygdala. Proc Natl Acad Sci USA 2005;102(26):9371–6.
• Vyas A et al. Prolonged behavioral stress enhances synaptic connectivity in the basolateral amygdala. Neuroscience 2006 [Epub ahead of print].
• Govindarajan A et al. Transgenic brain-derived neurotrophic factor expression causes both anxiogenic and antidepressant effects. Proc Natl Acad Sci USA 2006;103(35):13208–13.