Prof. Xiaolin Zhou's group has published an original research in Cerebral Cortex which revealed the neural dynamics of reward-induced response activation and inhibition
Humans are biased for reward, and often show automatic response tendency towards reward-predictive stimuli. Although the bias for reward can be beneficial in an evolutionary sense, it nevertheless causes undesirable behavioural consequences when it is in conflict with the current goal. Thus, top-down cognitive control is needed to overcome such prepotencies in order to realize task goal and ensure healthy functioning. The latest study from Prof. Xiaolin Zhou’s group has revealed how the human brain implements this dynamic process, with the combination of behavioural modelling, EEG, and fMRI-DCM.
In a series of experiments, the researchers presented a lateral target in the visual field, the location of which could be at the same side or the opposite side of the correct response hand (Fig. 1A). This lateral target stimulus triggers an automatic response tendency of the spatially corresponding hand, which needs to be overcome if the activated hand is opposite to what the task requires, thereby delaying the response. In particular, high or low reward was associated with different identities of the target. Relative to low-reward targets, high-reward targets elicited larger behavioural conflict, suggesting an increase in the automatic response tendency induced by the stimulus location. This tendency was accompanied by modulations of the lateralized readiness potential (LRP) over the motor cortex (Fig. 1B), and was inhibited soon after if the high-reward targets were incongruent with the correct response hand.
Fig. 1. (A) Experimental design. (B) The ERP component LRP over motor cortex (left panel) and parameter estimates extracted from primary motor cortex (M1) (right panel) in different experimental conditions.
Moreover, this process was accompanied by enhanced theta oscillations in medial frontal cortex (MFC) (Fig. 2A) and enhanced activity in a fronto-basal ganglia network (Fig. 2B). With dynamical causal modelling (DCM), the authors further demonstrated that the connection from pre-supplementary motor area (pre-SMA) to right inferior frontal cortex (rIFC) played a crucial role in modulating the reward-modulated response inhibition (Fig. 2C).
Fig. 2. (A) Topographical distribution of the power change in theta oscillation (left panel), and the power change at FCz as a function of frequency and time. (B) Brain areas involved in the inhibition on the inappropriate, reward-induced response activation. (C) The dynamic causal modeling (DCM) for pre-SMA, rIFC, rSTN and rCaudate.
The convergent behavioural, EEG and fMRI-DCM evidence revealed a dynamic neural model of reward-induced response activation and inhibition, which underlies the approach-approach conflict between two desired responses in a real-world situation. The results also shed light on the neural communication between reward and cognitive control in generating adaptive behaviours.
Wang L, Chang W, Krebs R, Boehler NC, Theeuwes J, Zhou X. (in press). Neural dynamics of reward-induced response activation and inhibition. Cerebal Cortex. https://doi.org/10.1093/cercor/bhy275