Tri-axial recording of event-related potentials during passive cognitive tasks in patients with alzheimer's disease

Abstract

Standard methods used to assess cognitive function in patients with Alzheimer's Disease (AD) often use instructions to direct attention and gauge task difficulty, and measure only the output of processing, i.e., the patient's behavioral response. Because this may focus assessment on functions that are observable and to periods when patient comprehension is not compromised, the present study presented stimuli without instruction, manipulated task difficulty by varying stimulus factors, and used the brain's electrical response as the dependent variable. Because the recording electrode's position on the scalp may limit full examination of the voltage distribution of these responses, a Tri-Axial method of recording electrical activity within a Cartesian coordinate system was used. Results suggest attention may inhibit habituation so that inputs can be represented, discriminated and consolidated. For the control group, the levels of task difficulty modulated electrical peaks presumed to reflect the brain's ability to perform these functions. In the AD group, these responses were attenuated or absent, suggesting that dysfunctional attentional processing may underlie response errors often attributed to memory.

Key Words:

• Habituation
• attention
• dishabituation
• passive task
• voltage trajectory
• vector magnitude