Age differences in virtual environment and real world path integration

Abstract

Accurate path integration (PI) requires the integration of visual, proprioceptive, and vestibular self-motion cues and age effects associated with alterations in processing information from these systems may contribute to declines in PI abilities. The present study investigated age-related differences in PI in conditions that varied as a function of available sources of sensory information. Twenty-two healthy, young (23.8 ± 3.0 years) and 16 older (70.1 ± 6.4 years) adults participated in distance reproduction and triangle completion tasks (TCTs) performed in a virtual environment (VE) and two "real world" conditions: guided walking and wheelchair propulsion. For walking and wheelchair propulsion conditions, participants wore a blindfold and wore noise-blocking headphones and were guided through the workspace by the experimenter. For the VE condition, participants viewed self-motion information on a computer monitor and used a joystick to navigate through the environment. For TCTs, older compared to younger individuals showed greater errors in rotation estimations performed in the wheelchair condition, and for rotation and distance estimations in the VE condition. Distance reproduction tasks (DRTs), in contrast, did not show any age effects. These findings demonstrate that age differences in PI vary as a function of the available sources of information and by the complexity of outbound pathway.

Keywords: Alzheimer's disease; aging; hippocampus; navigation; path integration; spatial memory.

Figure 1

Schematic of experimental setup: participants wore noise reducing headphones and a blindfold during guided walking (A) and wheelchair propulsion (B) conditions. Data were collected from reflective markers placed on a halo structure worn on the head of the participant. VE condition consisted of passively viewing a movement trajectory on a computer monitor (C) then moving a joystick when responding to the active portion of the task. Guided movements (lighter shaded lines) and participants movements (darker shaded lines) are shown on the schematic.

Figure 2

(A) Mean (± SE) relative distance error (RDE) for young (filled diamond) and older (filled square) participants. Age differences were significant in the VE condition (^*p < 0.05). (B) Mean (± SE) relative rotation error (RRE) for young (filled diamond) and older (filled square) participants. Age differences were significant in the wheelchair (^*p < 0.05) and VE (^*p < 0.01) conditions.

Figure 3

Mean (± SE) relative distance error (RDE) for young (open) and older (filled) participants. Conditions differences were found between VE and wheelchair; VE and walking conditions (^*p's < 0.05).