Event-related potential prolongation in Alzheimer's disease signifies frontal lobe impairment: evidence from SPECT imaging.

BACKGROUND

The N2 and P3 components of auditory event-related potentials (ERPs) and single-photon emission computed tomographic (SPECT) images are separate independent biological markers of cerebral function and are abnormal in Alzheimer's disease (AD). The relationship between ERP N2 and P3 latencies and regional cerebral perfusion abnormalities in AD is unknown.

METHODS

ERP and SPECT data were obtained one week apart in 18 patients with "probable" AD of mild or moderate severity, and 12 healthy age-matched elderly controls. Average premotor frontal, anterior temporal, inferior parietal, and occipital cortical/cerebellar perfusion ratios were calculated from the SPECT data and correlations with ERP N2 and P3 latencies derived for AD and control groups separately.

RESULTS

ERP N2 latency was correlated significantly with the average frontal perfusion ratio (r = -.59; p < .009), but correlations with average temporal, parietal, and occipital ratios were nonsignificant in the AD group. Similarly, ERP P3 latency was correlated significantly with the average frontal perfusion ratio (r = -.65; p < .004), but not with the other perfusion ratios in the AD group. In the control group, a partial correlation between the average frontal perfusion ratio and the ERP N2 latency was noted (r = -.52; p < .09), but no other ERP/SPECT correlations approached statistical significance.

CONCLUSION

ERP N2 and P3 latency delay in AD is a function of differential frontal lobe hypoperfusion.