Anterior Cingulate Cortex Is Involved in Changing Plans

Post by Deborah Joye

What's the science?

Imagine that you are driving a car, stopped at a red light. We know that when the light turns green, we are supposed to begin driving again. But if a pedestrian steps into the path unexpectedly, we must quickly change our plan of action to avoid hitting them. This processing of conflicting cues in our environment happens extremely fast and is thought to be helped by a brain region called the anterior cingulate cortex. In general, we think that the anterior cingulate cortex processes the conflicting signals, then sends information to other brain regions that control motor planning, such as the dorsal medial striatum, so that our actions reflect the new information from the environment. While we have inferred from research in humans that the anterior cingulate cortex is involved in the ability to abruptly change plans, no one has demonstrated it experimentally. This week in PNAS, Brockett, and colleagues developed a rodent model to demonstrate that the anterior cingulate cortex is necessary for deciding what to do when signals in the environment change suddenly.

How did they do it?

The authors first modified a STOP-signal task for use in rats. The STOP-signal task is commonly used to test cognitive control in human clinical populations and generally involves asking participants to respond to a cue, such as pressing a button when a light comes on the screen. In some of the trials, another cue will flash which tells the participants to not press the button or to do something else entirely. This model tests how well our brains can respond to cues which conflict with one another. The authors designed this test for use in rats by showing a light that indicates which direction a rat must go to in order to receive a sugar reward. In some of the trials, a second light is shown after the first, indicating that the rat must go the opposite direction instead. The authors then tested the necessity of the anterior cingulate cortex in this task by damaging one side of it in both male and female rats. After recovery from the procedure, rats were trained on the STOP-signal task. The authors also recorded electrical activity from neurons within the dorsal medial striatum to investigate how information from the anterior cingulate cortex is processed in this region before a behavior is produced.

What did they find?

The authors found that damage to the anterior cingulate cortex made the STOP-signal task harder. Specifically, lesioned rats had slower response times and were less accurate when they were forced to change their response direction suddenly (STOP trials) but had similar response times to control rats when they did not have to change their response selection suddenly (GO trials). Interestingly, after the presentation of one STOP trial, rats without an anterior cingulate cortex still performed better on the next consecutive trial if it was also a STOP trial. This shows that lesioned rats were still able to learn about conflicting signals. 

In control rats, neuronal activity in the dorsal medial striatum increased in response to the first light cue, then decreased in response to the second light cue. This means that the majority of recorded dorsal medial striatum neurons changed their firing in response to the conflicting cue. During STOP trials where the rat was able to successfully cancel the initial response, neural firing was delayed in rats with a damaged anterior cingulate cortex. However, when control rats made an error on STOP trials, firing for the initial — but incorrect — movement resembled firing on GO trials in lesioned rats, suggesting that anterior cingulate cortex is necessary for applying a brake on neuronal firing to cancel the first response. This effect was not seen in rats with a lesioned anterior cingulate, again suggesting that this region normally acts as a brake on activity in other brain regions.

What's the impact?

While the function of the anterior cingulate has been inferred based on previous research it has remained controversial. This study is the first to experimentally demonstrate that the anterior cingulate cortex is necessary for processing and correctly responding to conflicting environmental cues. It also provides useful experimental tools for testing this type of higher-level cognition while simultaneously monitoring neuronal activity in rodent models. Overall, these findings present an important contribution to figuring out exactly what the anterior cingulate cortex does and how it sends information to other brain regions that ultimately affect our behavior.

Brockett et al., Anterior cingulate cortex is necessary for adaptation of action plans, PNAS (2020). Access the original scientific publication here.