The team recorded neural activity in the ACC of these mice while they 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.
"The brain is complex and continuously active, so it makes sense that these two types of inhibitory interneurons define the boundaries of a behavior such as foraging, opening and then closing the 'gate' within a particular neural circuit through changes in their activity," says Kepecs.
This is an important advance, addressing a problem in behavioral neuroscience that scientists call "the cortical response zoo." When researchers record neural activity in cortex during behavior, and they don't know which type of neurons they are recording from, a bewildering array of responses is seen. This greatly 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 behavior.
"We think about the brain and behavior in terms of levels; what the cell types are and the circuits or networks they form; which regions of the brain they are in; and what behavior is modulated by them," explains Kepecs. "By observing that the activity of specific cell types in the prefrontal cortex is correlated with a behavioral period, we have identified a link between these levels."
|Contact: Peter Tarr|
Cold Spring Harbor Laboratory