Our everyday decisions about whether to "stay" or to "go" are supported by a brain region called the anterior cingulate cortex (ACC), which is part of the prefrontal cortex.
Neuroscientists from Cold Spring Harbor Laboratory (CSHL) have now identified key circuit elements that contribute to such decisions in the ACC.
CSHL associate professor Adam Kepecs and his team have linked specific brain cell types to a particular behavior pattern in mice - a "stay or go" pattern called foraging behavior.
The results showed that the firing of two distinct types of inhibitory neurons, known as somatostatin (SOM) and parvalbumin (PV) neurons, has a correlation with the start and end of a period of foraging behaviour.
Key to solving the problem is a mouse model developed by CSHL Professor Z Josh Huang. The mouse has a genetic modification that allows investigators to target a specific population of neurons with any protein of interest.
Kepecs' group, led by postdocs Duda Kvitsiani and Sachin Ranade, used this mouse to label specific neuron types in the ACC with a light-activated protein - a technique known as optogenetic tagging. Whenever they shone light onto the brains of the mice they were recording from, only the tagged PV and SOM neurons responded promptly with a 'spike' in their activity, enabling the researchers to pick them out from the vast diversity of cellular responses seen at any given moment.
The team recorded neural activity in the ACC of these mice while engaged in foraging behavior. They discovered that the PV and SOM inhibitory neurons responded around the time of the foraging decisions - in other words whether to stay and drink or go and explore elsewhere.
Specifically, when the mice entered an area where they could collect a water reward, SOM inhibitory neurons shut down and entered a period of low-level activity, thereby opening a 'gate' for information to flow in to ACC. When the mice decided to leave that area and look elsewhere, PV inhibitory neurons fired and abruptly reset cell activity.
When researchers record neural activity in cortex, and they don't know which type of neurons they are recording from, a bewildering array of responses is seen. This complicates the task of interpretation.
Hence the significance of the Kepecs team's results, for the first time showing that specific cortical neuron types can be linked to specific aspects of behaviour.