Dopamine and inhibitory action control

An important aspect of cognitive control and cognitive flexibility is the ability to stop an ongoing action. This ability is driven by interactions between the prefrontal cortex and the basal ganglia. Some say that dopamine plays a crucial role in response inhibition. However, it might be that the beneficial effects of dopaminergic stimulants on response inhibition are limited to those whose inhibitory efficiency is suboptimal. This research will investigate if there is a dopaminergic impact on response inhibition efficiency in healthy subjects.

This research

During a stop-signal task, participants are presented with a stimulus which tells them to execute a certain response. This stimulus may or may not be followed by a stop-signal, which means they have to abort the response immediately.

How well a participant performs on this task is indicative to his efficiency in actively inhibiting his thoughts and actions. The test assesses the participant’s ability to stop a planned or ongoing action in a voluntary fashion. It can estimate the duration of the covert response-inhibition process.

Dopamine functioning is measured by the spontaneous eyeblink rate.

Conclusion

The results show that the spontaneous eyeblink rate predicts the efficiency in inhibiting action tendencies in a stop-signal task in healthy people. It is difficult however to say anything about the causal direction of this relationship. They do observe a pattern which seems to be consistent with other results, that show that people suffering from dopaminergic imbalances have more difficulty inhibiting their actions in response to stop signals. It seems that dopamine plays a role, not only for those with a suboptimal inhibitory efficiency, but in healthy people also.

A possible explanation for the found pattern may be that the relationship between dopamine and response inhibition follows an inverted U-shape. This means that only an average dopamine level allows optimal response inhibition. When dopamine is too high or too low, this will impair the cognitive processes.