Eyeblink Classical Conditioning to an Olfactory Stimulus in Older Adults, Patients with Alzheimer's Disease and Older Adults at Risk for Alzheimer's Disease
Description:... The goal of this study was to demonstrate eyeblink classical conditioning (EBCC) to an olfactory stimulus and apply this technique to patients with Alzheimer's disease (AD) and those at-risk for AD by virtue of genetic status. A total of 95 people participated in this research: 15 people diagnosed with AD and 80 normal control participants, 28 of whom were carriers of the [special characters omitted]4 allele of apolipoprotein-E. Study 1: The goal of the first study was to determine whether humans could acquire a conditioned response (CR) to an olfactory conditioned stimulus (CS). Ten control subjects were tested in an EBCC delay paradigm with an olfactory CS. Results indicated that participants were able to learn and demonstrate a CR to an odorant stimulus. Study 2: The second study was designed to examine the role of inter-stimulus interval (ISI) on rate of CR acquisition with an olfactory CS. Twenty-four older adults were tested with either a long or a short ISI. Results indicate that acquisition of the CR by older adults is enhanced with a longer ISI. Study 3: Studies have shown that EBCC to auditory tones is a good discriminator of diseased from normal populations. There are not many studies in the field, making replication of those findings important. Given the documented olfactory dysfunction in AD, it was hypothesized that EBCC with an olfactory CS would provide a better discriminator between demented and non-demented older adults than an auditory CS. Performance of 15 patients with AD was compared to that of 30 control participants. Results indicate slowed olfactory CR acquisition in patients with AD. Study 4: This study was designed to examine performance of a group of people at risk for AD by virtue of genetic susceptibility (apoE, [special characters omitted] 4 positive). Performance of 30 healthy control participants (the same participants included in Study 3) was compared to performance of 28 [special characters omitted] 4 positive participants. No differences were found between the groups for overall CR acquisition to an auditory or an olfactory CS; however, the at risk group did evidence a slower rate of acquisition to the olfactory CS.
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