The ability to suppress inappropriate behavioral responses—known as cognitive inhibitory control—is essential for everyday living. The time required for the brain to inhibit a response is called the stop-signal reaction time. Certain conditions such as Parkinson’s disease, attention deficit hyperactivity disorder, schizophrenia, and even normal aging, can affect cognitive inhibitory control, resulting in a slower stop-signal reaction time.
Basic studies are underway to help better understand the mechanisms behind this process, which may ultimately lead to new therapeutic targets for people with cognitive problems affecting stop signal reaction times. One new finding, reported online Sept. 14, 2015 in Nature Neuroscience, provides important new insights. Most research to date on cognitive inhibitory control and stop-signal reaction time has focused on the fronto-basal-ganglia circuit, a part of the brain that helps control movement. Now, researchers from the Laboratory of Behavioral Neuroscience at the National Institute on Aging at NIH and Johns Hopkins University provide new evidence that this cognitive function might also be controlled by the inhibition of neurons in another part of the brain, the basal forebrain, the bottom-front part of the brain typically associated with the wake and sleep states as well as with learning and memory. Changes in the basal forebrain have also been associated with age-related cognitive decline, as well as Alzheimer’s disease.
In the study, investigators trained rats to respond to a sound, but to inhibit their response if the sound was immediately followed by a light signal. Researchers measured the rats’ stop-signal reaction times and recorded neuronal activity in the basal forebrain.
Researchers found that the neurons in the basal forebrain of rats were silenced—not firing signals—immediately before cognitive inhibitory control. The faster the neurons were silenced, the shorter the stop-signal reaction time. This link was further established when scientists artificially silenced basal forebrain neurons and saw that the rats would no longer respond to sound even when there was no light signal. This suggests that basal forebrain neurons alone are powerful enough to exert cognitive inhibitory control over behavior in the rats.
Reference: Mayse, J.D., et al., Basal Forebrain Neuronal Inhibition Enables Rapid Behavioral Stopping. Nature Neuroscience. E-pub Sept 14, 2015. doi: 10.1038/22.4110.