D. James "Jim" Surmeier (born December 7, 1951), an American neuroscientist and physiologist of note, is the Nathan Smith Davis Professor and Chair in the Department of Neuroscience at Northwestern University Feinberg School of Medicine.
It was in Kitai's lab that he first became interested in the basal ganglia and started investigating the effects of dopamine in the brain, a fundamental question that has driven a lot of his subsequent research as an independent scientist.
By mid-90s, despite widespread consensus regarding the clinical relevance of striatal dopaminergic signaling, the distribution and segregation of different classes of dopamine receptors, into either the same or distinct neuronal populations was unclear and remained widely debated.
In pioneering experiments, using patch clamp recordings in conjunction with single cell gene profiling through RT-PCR, Surmeier reconciled the seemingly confounding results from anatomical and functional studies by showing that the direct (striatonigral) and indirect pathway (striatopallidal) striatal projection neurons predominantly expressed either the D1 or D2 dopamine receptors.
[6][7] Understanding the opposing effects of D1 and D2 receptor signaling and the consequent insights into the dopaminergic modulation of bi-directional synaptic plasticity in the direct and indirect spiny neurons was a conceptual advance that has proven fundamental to understanding striatal function in both behavioral adaptation as well as Parkinson's disease pathology, and continues to provide a foundation for current models of how dopamine controls striatal circuitry.
As a result, the response of the "no-go" pathway (D2 receptor expressing striatopallidal neurons) to depolarizing cortical input is enhanced, providing a potential neural substrate for attentional shift.