The Effect of Midbrain Phasic Dopamine Signal Manipulation on Cognitive Control Deficit

Cognitive control deficits are seen in many psychological and brain disorders. The dual mechanism of control (DMC) theory assumes two proactive (PC) and reactive control (RC) modes for cognitive control and uses the AX version of continuous performance test (AX-CPT) as the main research paradigm. This test determines deficits in cognitive control modes in various disorders. Midbrain dopamine signal plays an important role in the pathophysiology of various disorders with cognitive control deficits and plays a key role in DMC theory.
The present study was a computer simulation to investigate the effect of midbrain dopamine signal manipulation on cognitive control deficits. Simulation is based on LEABRA cognitive architecture and using the PBWM model as a model of working memory and PVLV model as a model of midbrain dopaminergic system. This investigation has been implemented in the emergent computer simulation software where the AX-CPT is presented to the model and the model performance was measured. Simulation results are calculated in three proactive control behavioral index (PCB), PC, and RC indices.
With increasing gain of phasic dopamine signal from 0 to 100 percent, a 15 to 45 percent changes occurred in the trend of curves. Increasing up to 15 percent, the error indices sharply decreased, PC was reduced, RC is increased, and PCB tends from PC to RC. Increasing from 15 to 45 percent, PC was increased, RC was reduced, and PCB tends from RC to PC. These trends were damped between 45 to 100 percent enhancement. Indices related to the average reaction time showed a reversed pattern of error indices.
The results of the error indices by decreasing phasic dopamine level indicate an increase in PC deficit and RC improvement as well as a greater tendency toward RC. These results are consistent with the hypodopaminergic pattern and DMC mechanism deficits in attention deficit hyperactivity disorder, depression, negative symptoms of schizophrenia as well as chronic addiction of cocaine and alcohol and Parkinson's disease.