In the late stages of Huntington's disease, thalamocortical activity becomes which of the following?

• A. Bradykinesia
• B. Rigidity
• C. Unsteady/slow/stiff gait
• D. Thalamocortical inhibition

Answer: (D)

Late in Huntington's disease, the motor system shifts from a hyperkinetic state to a hypokinetic one as the circuitry supporting movement becomes more globally compromised. Movement is driven by thalamocortical output, and this output is tightly regulated by the basal ganglia through inhibitory signals to the thalamus. In earlier stages, loss of neurons in the indirect pathway reduces thalamic inhibition and leaves more thalamocortical activity, producing chorea. As degeneration progresses, the remaining circuits fail to sustain thalamic excitation, so the thalamus is more strongly inhibited, and thalamocortical drive to the cortex is diminished. This results in slower, stiffer, and more rigid movement—classic hypokinetic features of late-stage disease. So the late-stage state is thalamocortical inhibition.

The other options describe movement patterns you can observe—slowness, rigidity, and gait instability—rather than the underlying neural drive to the cortex, which is why they’re not the best description of the late-stage motor state.