Final answer:
Parkinson's disease involves basal ganglia deficits due to the degeneration of dopaminergic neurons in the substantia nigra, leading to impairments in learning motor tasks, including visually cued operant conditioning, because of dopamine depletion.
Step-by-step explanation:
The basal ganglia deficits in Parkinson's disease result in impairment of learning a visually cued operant conditioning task. Parkinson's disease is a disorder of the basal nuclei, specifically affecting the substantia nigra, where degeneration of dopaminergic neurons occurs. The loss of dopamine here shifts the balance between the direct and indirect pathways within the basal ganglia circuitry. With dopaminergic neurons from the substantia nigra pars compacta (SNc) no longer releasing enough dopamine into the striatum, the direct pathway is less activated while the indirect pathway becomes more dominant. This imbalance leads to hypokinetic phenomena and motor symptoms like tremors and rigidity. Consequently, the cognitive capacity to learn new motor tasks, such as those required for visually cued operant conditioning, is impaired due to dopamine depletion in these pathways.