Objective: Topographical disorientation (TD) and its consequence getting lost is one of the incipient symptoms in patients with Alzheimer's disease (AD). When occurred, these patients cannot find their way home even in a familiar place. Some abilities are critical to prevent people from getting lost, such as the ability to detect the trivial changes in the environment, to search for useful cues, and to inhibit the influences from the distracters during way-finding. The mentioned abilities are in turn related to attention and possibly to behavioral trait. According to Cloninger, novelty seeking (NS) is a kind of personality and characterized by an inherited tendency toward the activation of behavior such as exploratory activity in response to novelty, impulsive decision making and extravagance in the approach to the cues of reward, and quick loss of temper. The purpose of this was to explore the relationship among novelty seeking (NS) behavior, novelty detection ability and the way-finding.
Method: The participants, including AD patients and normal controls (NC), were recruited from Alzheimer Disease Center at National Cheng Kung University Hospital, with normal or corrected vision of at least 20/50 full vision fields and without limitation of eye movements. The Cognitive Ability Screening Instrument (CASI), MMSE and the Clinical dementia rating scale (CDR) were used to assess their general cognitive functions and dementia severity. Chinese version of tri-dimensional personality questionnaire (TPQ) was used to assess the novelty-seeking behavior. In the Exp1, a habibutation-dishabituation paradigm was applied to assess the visual exploratory behavior with three runs. For each run, a picture of personally familiar street scene was displayed for 5 times, followed by a picture taken from a city far from Tainan, and then followed by a picture of famous landmark in Taiwan for 5 times. We used iView X Hi-speed 1250 video-based eye tracker to measure and record fixation number, fixation duration, saccade number, saccade duration, and saccade amplitude. In theExp2, we designed a task to measure the participants' ability to find their way to a specific location they had been familiar with. We modified parts of the pictures without telling them the facts; for example, we changed the color of a building. The eye movements were recorded and analyzed. In the Exp3, the pictures displayed in the Exp 2 were shown again and the participants were requested to pick up any difference as the ability of novelty detection.
Results: Twelve AD (7 males)and 8 normal control(NC) (2 males) completed the study so far. No difference was detected between AD and NC in the age (71 vs 65 years), educational years (10 vs 9 years) or in the TPQ. As expected, AD group was worse in the MMSE, and in the items of recent memory, orientation andabstract thing as well as the total score of CASI. In the Exp 1, no difference was found in fixation number, fixation duration, saccade number, saccade duration, or saccade amplitude between the groups. In the Exp 2, the eye movements and the way finding ability showed no correlation. Finally, in the Exp 3, no difference in the novelty detection rates between the groups. When divided to high NS and low NS according to the scores of TPQ in each group, the AD patients with high-NS had a better performance in the way-finding task which is finding was not observed in the NC group.
Conclusion: The preliminary result is not consistent with previous studies. As reported by Rӧsler et al(2000), the AD patients showed more fixation numbers and longer fixation time in a visual search task. Moreover, novelty seeking may represent a negative character as an index of distractibility. In this study, AD patients with high NS, however, performed better in the way-finding task. Furthermore, theresult that most parameters did not show difference between AD and NC needs more participants to see the final fact.