By Jaeeon Lee

While we navigate our environment, our brains have to process myriad streams of information coming from different senses and translate them into distinct behavior. For instance, I might see a cup of coffee on my desk and reach towards the cup with my right hand, while texting on the phone with my left hand. As I hear the doorbell ring, I might also turn my head towards the door and start walking while still texting and sipping the last remainder of the coffee. How can our brain simultaneously control our different body parts without interference?

It turns out that a set of brain structures called the basal ganglia are involved in transforming sensory information into various motor commands. We tested the hypothesis that the basal ganglia might be divided into topographical channels, each controlling a distinct behavior. We first used an anterograde tracer to map the anatomy. We were able to confirm that distinct pathways of the basal ganglia remain segregated in all the output nuclei of the basal ganglia. Furthermore, the nature of the brain regions targeted by some of the pathways made specific prediction about what kinds of behavior they might trigger. Indeed, using a spatially focal optogenetic approach, we were able to confirm that specific regions within striatum only triggered a single behavior (i.e. licking or locomotion). Moreover, stimulating a locomotion-inducing striatal region while the mice were licking did not interfere with the ongoing licking, suggesting a parallel model of basal ganglia.

Distinct pathways in the basal ganglia mediate either turning (left) or licking (right).

A key feature of our study is the ability to both anatomically and functionally isolate a circuit of interest. It is now possible to define the pathway within the basal ganglia relevant for a given behavioral task, and then anatomically define the regions downstream of the pathway. This would allow much more precise and targeted investigation of the computations occurring within the basal ganglia. We hope that future investigations can take advantages of the tools developed in this study to further elucidate the functional role of the basal ganglia.

Jaeeon Lee is a graduate student in the PhD Program in Neuroscience, working in the lab of Bernardo Sabatini in the Department of Neurobiology at Harvard Medical School. 

This story also appears in the HMS Neurobiology Department newsletter, The Action Potential.

Learn more in the original research article:
Anatomically segregated basal ganglia pathways allow parallel behavioral modulation. Lee J, Wang W, Sabatini BL. Nat Neurosci. 2020 Nov;23(11):1388-1398. doi: 10.1038/s41593-020-00712-5.