We examined eyelid movements during spontaneous, voluntary, and trigeminal reflex blinks in 16 patients with mild to moderate Parkinson's disease (PD) off medication and 14 controls. Voluntary and reflex blink amplitudes tended to be smaller than normal for PD patients, whereas eyelid kinematics (amplitude-maximum velocity relationship) for all three blink types were normal. Spontaneous blink rate was less than normal for 10 patients and abnormally high for 6 patients. A significant positive correlation between spontaneous blink amplitude and blink rate was found. These observations suggest that PD modifies the gain of a premotor blink circuit shared by spontaneous, voluntary, and reflex blinks.

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Our aim was to investigate changes in movement-related cortical potentials (MRCPs) in ALS patients with different degrees of upper motor neuron (UMN) involvement. Since respiratory failure is the main cause of death in ALS, changes in inspiratory-related (sniffing) potentials were studied in addition to finger-flexion-related potentials. Subjects (21 ALS, 19 controls) performed two self-paced motor tasks while their EEGs were recorded. The first task required flexions of the right index finger and the second, brisk nasal inspirations. The early (BP1), late (BP2) and motor potential (MP) components of MRCPs were evaluated. Results showed that patients generated higher MRCPs than controls. However, this effect was most significant in the subgroup of patients with low UMN burden (LUB). The high UMN burden (HUB) subgroup did not differ from controls, but had significantly lower MP amplitudes than the LUB subgroup. Progressive UMN deterioration was associated with an initial increase, followed by a later decrease, in MP amplitudes in ALS. In conclusion, the increased MRCPs in LUB compared to HUB patients indicate different processes of ALS pathophysiology that force opposing changes in MRCP amplitudes.

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