Color Responses of Flash Visual Evoked Potentials in Normal Adults, Normal Elderly Subjects and Dementia of the Alzheimer Type Using Light Emitting Diodes

Abstract

Background: Since initially we could only employ the red light goggle‐shaped stimuli equipment with flash light emitting diodes (LEDs), we had little information concerning different color responses of visual evoked potentials (VEPs). On our request, Nihon Kohden (Tokyo, Japan) developed green light goggle‐shaped stimuli equipment with LEDs in 1999.The purpose of this study was to determine the effects of green and red flash VEPs in normal adults, normal elderly subjects and patients with dementia of the Alzheimer type (DAT). Methods: Subjects consisted of a normal adult group (n=30), normal elderly group (n=10), and DAT patients (n=7). Transient VEPs of 1 Hz were measured. The recording electrodes were placed at midline‐occipital, left‐occipital and right‐occipital sites in accordance with the ten‐twenty electrode system. Results: In the normal adult group, peak latencies of green flash VEPs increased significantly compared to those of red flash VEPs (N2, P3: p<0.01, N3: p<0.05). The N2 and P3 latencies of both red and green flash VEPs were delayed in the normal elderly and DAT groups compared with those in the normal adult group. The delayed latencies of red flash VEPs were greater than those of green flash VEPs. Conclusion: The difference in latency between green and red flash VEPs corresponds to the difference in the conducting time from three rods (each spectrum peak is 419–420 nm, 530–534 nm, and 558–564 nm) to the visual central system. Each channel from the three rods to the visual central system may have an individual speed reaction, individual ageing and pathological changes. The results indicate that the peak latency of red light reveal elderly and pathological change more easily than that of green light.