I’m sure that you would like to improve on this terrible pun–feel free to chime in in the comments! And now let’s move beyond the acronym: this post is about a poster that was shown at #SfN14 on Monday morning, November 17, during the session on Executive function: Decision making.
358.21/SS34. Disrupting inhibition in posterior parietal cortex reduces decision accuracy. K. ODOEMENE, A. M. BROWN, M. T. KAUFMAN, A. K. CHURCHLAND
The authors, from Cold Spring Harbor Laboratory, NY, are interested in understanding how sensory information is used by the brain to inform decision making. They trained mice on a visual discrimination task in which the animals had to learn to recognize that a slowly flashing light was associated with a water reward in one location and a faster flash with a reward at another place. They then injected a viral vector encoding a protein known as a DREADD: a designer receptor exclusively activated by a designer drug (really, that acronym is awesome), into the posterior parietal cortex of both hemispheres. The DREADD here was designed to be expressed only in inhibitory interneurons and was meant to suppress their activity. Injecting the DREADD in itself did not alter the animals’ behavior in any way, since there is no ligand for that receptor in the mouse’s organism (in this case, the ligand was a derivative of clozapine that the authors took care to verify was not metabolized by the mice into clozapine itself, a widely-used anti-dopaminergic drug that would likely have altered performance). AFfter injection of the ligand, however, the mice became worse at performing the task. The authors checked that the mice were indeed attempting to perform the task, although they were a little slower than controls, suggesting that the behavioral effect was not due to a general inhibition of brain functions.
The next steps for the authors will include targeting the regions of cortex that are injected using intrinsic signal optical imaging (the posterior parietal cortex of mice, between the somatosensory and visual cortices, is likely a functionally heterogeneous area and it would be important to know whether the injected region is visual or something else) and electrophysiological recordings to find neural correlates of the perceptual and decision-making stages of the task and their alteration by the DREADD-ligand combination.
I liked discovering the DREADD approach, with which I was not familiar, and I am looking forward to reading more about the neural correlates of that experiment.