Why is neuronal plasticity interesting for psychiatrists?

Abstract

Neuronal plasticity refers to the ability of neuronal networks to change their structure and function to better accommodate to the environmental input.  Plasticity of neuronal networks is believed to underlie learning and memory, but also emotionality and problems with plasticity are connected to several brain disorders, including mood disorders. Moreover, antidepressant treatments have been shown to promote different forms of neuronal plasticity, including neurogenesis, synaptogenesis and neuronal maturation.  Therefore, understanding the mechanisms of developmental and adult plasticity is becoming increasingly important for psychiatrist and may influence the treatment of mood disorders.

Neuronal plasticity occurs at different organizational levels in brain and is always bidirectional, both growth and pruning are needed: Neurogenesis and selective apoptosis; outgrowth and pruning of axons and dendrites; synaptogenesis and synaptic elimination; long-term potentiating and depression of synaptic strength.  The guiding principle of plasticity is neuronal activity: synapses, which are active and thereby reflect the environmental input are maintained, whereas inactive synapses are eliminated.  The aim is the optimization of information processing within the functional networks.

We have investigated how antidepressants influence neuronal plasticity of the mammalian visual cortex. We found that chronic antidepressant treatment reactivates the critical period plasticity in the visual cortex adult rats and thereby helps to repair malfunctioning neuronal networks brought about by imbalanced early experiences.  However, to achieve this, antidepressant treatment needs to be combined with environmental rehabilitation.  This suggests that antidepressant drugs act permissively to facilitate the effects of rehabilitation on the structure of neuronal networks in brain.