The neuron doctrine, which holds that neurons are the basic elements of the nervous system, has guided research on the brain mechanisms of neuropsychiatric diseases for more than a century. During the past generation we have seen a gradual release of the strict hold that the neuron doctrine has had over our approach to the brain. This is attributable in part to a growing recognition that disturbances in cell-autonomous processes as etiological factors in psychiatric disorders are more the exception than the norm. However, the major reason for the renewed interest in circuits has been the advent of in vivo imaging techniques. These methods allow us to probe the structure and function of the brain in vivo and can be (but unfortunately rarely are) used to follow changes in brain structure and function during the evolving course of an illness. Importantly, we can now obtain measures purported to be proxies for activity changes in distributed circuits (systems) in the brain.
Deutch AY. Extending Corticostriatal Systems. JAMA Psychiatry. 2016;73(8):871-872. doi:10.1001/jamapsychiatry.2016.0242