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Phasic visual alertness in Alzheimer's disease and ageing
Andrea Tales1, Janice L Muir, Antony Bayer
1School of Psychology, Cardiff University, Cardiff CF11 3YG, Wales, UK. andrea.tales@north-bristol.swest.nhs.uk
Neuroreport
|December 25, 2002
Summary
Patients with Alzheimer's disease (AD) show a reduced ability to react quickly to visual stimuli. Unlike healthy adults, those with AD do not benefit from an alerting cue, suggesting impaired alertness.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Neurology
Background:
- The alerting effect enhances reaction times via noradrenergic activity.
- Alzheimer's disease (AD) involves noradrenergic system dysfunction and reduced noradrenaline.
- This dysfunction may impair the alerting effect in AD patients.
Purpose of the Study:
- To investigate the alerting effect in Alzheimer's disease patients.
- To determine if AD patients exhibit a reduced or abolished alerting effect compared to controls.
- To explore the implications of impaired alertness for AD diagnosis and daily functioning.
Main Methods:
- Reaction time measurements to a visual target stimulus.
- Inclusion of a preceding visual alerting cue (200 ms prior).
- Comparison between 17 AD patients, 19 age-matched controls, and 13 younger controls.
Main Results:
- Alerting cues significantly reduced reaction times in both young and older healthy adults.
- Alzheimer's disease patients showed no significant change in reaction times with the alerting cue.
- This indicates a marked inability to increase phasic alertness in AD.
Conclusions:
- The alerting effect is abolished in individuals with Alzheimer's disease.
- Impaired phasic alertness may contribute to functional deficits in AD.
- The alerting effect could serve as a simple diagnostic or progression monitoring tool for AD.