Methods

1. Blindly Biased: Restricting Cue Access Impacts Spatial Orientation in a Human Analogue of the Water Maze B.P. Apger, D.M. Grimelli, J.R. Köppen, S.S. Winter, D.G. Wallace Department of Psychology, Northern Illinois University, DeKalb, IL, USA Introduction Experiment 1 Figure 5: Average absolute heading error is plotted for each block of place training and both blocks of matching-to-place testing. Figure 8: Average absolute heading error is plotted for the allocentric and egocentric groups across blocks of place training. Wandering behavior is characteristic of the progression of Dementia of the Alzheimer‘s Type (DAT). The types of deficits mediating wandering are not clearly defined. Use of environmental cues to maintain spatial orientation has been a focus of previous research. The current set of experiments examine the role of self-movement cues in human spatial orientation in a manipulatory scale version of the Morris water maze. Restricting access to self-movement cues appears to bias specific response characteristics. These results prompt future research investigating spatial orientation deficits seen during the progression of DAT. Place training and matching-to-place testing were examined in a tabletop bead maze while participants were blindfolded. Figure 2: Topographic searching patterns of a representative participant during each block (A, B, C, D) of place training. A B Methods Figure 6: Average correlation between peak speed and shortest distance is plotted for each block of place training and both blocks of matching-to-place testing. Figure 9: Average correlation between peak speed and shortest distance is plotted for the allocentric and egocentric groups across blocks of place training. Blindfolded participants were wheeled into a 10’x10’ room and positioned at a square table that held the bead maze. The maze consisted of a circular arena (.482 m diameter), divided into four quadrants and filled with beads. A piece of Velcro tape was hidden in one of the four quadrants. Beginning with their fingertip positioned at a random location around the perimeter of the maze, participants were instructed to search for the hidden Velcro over a series of 20 trials. In Experiment 1, 20 participants searched for the Velcro which was held in an absolute location across a series of 20 trials (place training). On the 21st through 26th trials, Velcro was repositioned every two trials to a new quadrant in the maze (matching-to-place testing). In Experiment 2, 13 participants were assigned to either an allocentric or egocentric condition and searched for the Velcro over a series of 20 trials. In the egocentric condition, the Velcro was held in a relative location to the participant. In the allocentric condition, the Velcro remained in an absolute location within the maze. Between each trial, participants moved to a new random location around the table. While moving between trials, the blindfold was removed and participants in both groups had access to visual room cues. Topographic and kinematic characteristics of hand movement were assessed across four blocks of five trials. Figure 1: Diagram of the apparatus used in the current study. C D Figure 3: Topographic searching patterns of a representative participant during the first (A) and second (B) trials of matching-to-place testing. Experiment 2 Conclusions A B • Self-movement cues are sufficient to guide performance in the manipulatory scale version of the water maze tasks: • Participant performance significantly improved across place training trials. This observation is consistent with encoding the location of the Velcro tape. • Participant performance improved during matching-to-place testing. This observation is consistent with updating the representation of the Velcro tape location. • Restricting access to self-movement cues at the manipulatory scale biases specific response characteristics when participants are restricted to allocentric or egocentric reference frames: • The allocentric group displayed an improvement in direction, but not distance estimation. • The egocentric group displayed an improvement in distance, but not direction estimation. • These results prompt future research investigating the effects of reference frame on the nature of the representation encoded and may provide insight to the spatial orientation deficits seen during the progression of DAT. Place learning was examined while blindfolded participants searched for the Velcro tape that was fixed relative to either an allocentric or egocentric reference frame. Figure 7: Schematic view of allocentric (left) and egocentric (right) conditions is presented for two consecutive trials as the participant shifts positions around the apparatus. Figure 4: Kinematic (left) and topographic (right) graphs of a representative participant on paths of varying distance. Correspondence should be addressed to Douglas G. Wallace: dwallace@niu.edu or wallacelab.weebly.com