Final answer:
A cerebellar lesion affects coordination and balance, leading to ataxias, whereas a basal nuclei lesion affects the regulation of voluntary movement, potentially resulting in movement disorders like Parkinson's disease.
Step-by-step explanation:
A lesion in the cerebellum primarily affects coordination and balance, resulting in ataxias, which are characterized by a lack of voluntary coordination of muscle movements. This can make activities such as walking or reaching for objects difficult and uncoordinated. The cerebellum compares the intended movement from the cerebral motor command with proprioceptive feedback and sends corrective commands, a process crucial for smooth and coordinated movements.
In contrast, a lesion in the basal nuclei can lead to movement disorders such as Parkinson’s disease, which is marked by tremors, stiffness, and bradykinesia (slow movements). The basal nuclei are involved in regulating voluntary movement and motor learning, as well as adjusting movements initiated by the cerebral cortex. Lesions here disrupt the balance of neurotransmitters, leading to impaired initiation and regulation of movement.