Disruption of classical conditioning in patients with Alzheimer's disease.

One of the primary features of Alzheimer's disease (AD) is a disorder of memory. Although considerable effort has been devoted to characterizing this memory disorder, simple forms of memory such as classical (Pavlovian) conditioning have not been studied. The prevailing view has been that these simple forms of memory are not affected in AD. These forms of memory, however, may be of particular interest because they are beginning to be well understood at the neurobiological level. Because of this, when memory disorders are detected, it may be possible to specify their neurobiological substrate. We now report that classical conditioning of the eyeblink response is disrupted in AD patients compared to age-matched controls. This deficit in conditioning is not due to nonassociative factors such as changes in sensitivity to stimuli or disruption of the motor response. The results are considered in terms of using simple forms of memory to help generate hypotheses regarding the neurobiology of age-related memory disorders.