Do P1 and N1 evoked by the ERP task reflect primary visual processing in Parkinson's disease?

OBJECTIVES

To evaluate whether P1 and N1 evoked by ERP tasks could appropriately reflect primary visual processing in Parkinson's disease (PD).

METHODS

We recorded ERPs in 13 PD patients with duration of illness less than 5 years and 18 age-matched normal control subjects. P1 and N1 from Oz were evoked by a visual oddball and a delayed matching S1-S2 task. The effect of different events on P1 and N1 was studied. All patients were given an ECD-SPECT examination, and the SPECT images were overlaid on the 3D-MRI. The correlation of P1 or N1 to the regional cerebral blood flow (rCBF) was studied.

RESULTS

P1 was not influenced by different events. There was no significant P1 differences between the PD and the normal group. N1 was significantly shorter and smaller in the patients than that in the normal group. N1 amplitude after the waveform subtraction (target-frequent) in the PD group did not show significant difference with that in the normal controls, nor with the N1 before the subtraction. Nd, the subcomponent of N1 after the subtraction in the patients was significantly earlier and smaller than that in the normal controls. P1 only weakly correlated with the rCBF in the occipital lobe. N1 was correlated with the rCBF in a global region.

CONCLUSIONS

The results provided some evidence that P1 might reflect the primary visual processing, and N1 might be involved in both primary and cognitive visual processing. The altered N1 in the PD patients might be due to the deformed Nd.