Earlier this month, research by Jeffrey Erlich, NYU Shanghai Assistant Professor of Neural and Cognitive Sciences, partnered with Chunyu Duan and Carlos Brody, was published in Neuron—one of the most influential and relied-upon journals in the field of neuroscience, embracing interdisciplinary strategies that integrate biophysical, cellular, developmental, and molecular approaches with a systems approach to sensory, motor, and higher-order cognitive functions.
In “Requirement of Prefrontal and Midbrain Regions for Rapid Executive Control of Behavior in the Rat,” they explored the neural mechanisms of executive function in the rat using a novel rapid sensorimotor remapping behavior, the Pro/Anti Orienting paradigm.
In this paradigm, on each trial the rat would enter and stay in a central nose port for 1.5 seconds. A Pro or Anti sound-cue would play during the first 1 s of the fixation period. The sound indicated a task of orienting either toward (Pro) or away from (Anti) a future left or right target LED to obtain a reward. After the sound ended, there was another 500ms silent fixation period that required the rat to remember the task. After this delay, the target light would appear on the left or right. For example, if the light was on the left, then on a Pro trial, rats would be rewarded for orienting to the left, but on an Anti trial, rats would be rewarded for orienting to the right The Pro and Anti tasks could switch from one trial to the next.
A switch from one task to the other requires re-routing stimulus-induced neural activity from one associated response to its opposite. Following an automated protocol, rats were trained to perform cued Pro and Anti trials in interleaved blocks. Without further training, rats successfully performed randomly intermingled Pro and Anti trials.
They found that rats could switch the action associated with a stimulus immediately after the change in task cue without any error-driven re-learning. This differs from most behavioral flexibility studies in rodents, in which uncued set shifts or stimulus-action reversals are indicated by errors, and behavior changes gradually over multiple trials.
Multiple behavioral asymmetries suggested that Anti behavior is cognitively demanding while Pro is easier to learn and perform. This is consistent with a prominent hypothesis in the primate literature that Anti requires prefrontal cortex (PFC), whereas Pro could be mediated by midbrain superior colliculus (SC). The asymmetries observed were remarkably consistent with behavioral phenomena observed in monkeys and humans performing executive control tasks, such as the Stroop Task.
Pharmacological inactivation of rat medial PFC supported its expected role in Anti. Remarkably, bilateral SC inactivation substantially impaired Anti while leaving Pro essentially intact. Moreover, SC inactivation eliminated the performance cost of switching from Anti to Pro tasks.
Their results establish a rodent model of single-trial sensorimotor remapping and suggest a critical role for SC in the cognitively demanding Anti task.
Written by Charlotte San Juan and Jeffrey Erlich