Turning bias in virtual spatial navigation: age-related differences and neuroanatomical correlates

Abstract

Rodents frequently exhibit rotational bias associated with asymmetry in lesions and neurotransmitters in the striatum. However, in humans, turning preference is inconsistent across studies, and its neural correlates are unclear. We examined turning bias in 140 right-handed healthy adults (18-77 years old), who navigated a virtual Morris Water Maze. On magnetic resonance images, we measured volumes of brain regions relevant to spatial navigation. We classified turns that occurred during virtual navigation as veering (less than 10°), true turns (between 10° and 90°) and course reversals (over 90°). The results showed that performance (time of platform search and distance traveled) was negatively related to age. The distance traveled was positively associated with volume of the orbito-frontal cortex but not with the volumes of the cerebellum, the hippocampus or the primary visual cortex. Examination of turning behavior showed that all participants veered to the right. In turns and reversals, although on average there was no consistent direction preference, we observed significant individual biases. Virtual turning preference correlated with volumetric asymmetry in the striatum, cerebellum, and hippocampus but not in the prefrontal cortex. Participants preferred to turn toward the hemisphere with larger putamen, cerebellum and (in younger adults only) hippocampus. Advanced age was associated with greater rightward turning preference. Men showed greater leftward preference whereas women exhibited stronger rightward bias.

Keywords: Aging; Brain asymmetry; Brain volume; MRI; Morris Water Maze.

Figure 1

A typical view from within the virtual environment (left) and overhead diagram of the vMWM map (right). Participants viewed the environment from a first person perspective.

Figure 2

Examples of turn typology.

Figure 3

Sex differences in vMWM performance: Distance and time of search by trial.

Figure 4

Distance traveled and time spent in search of a hidden platform in the vMWM as a function of age and trial number. The color codes the magnitude of the performance index, distance and time.

Figure 5

Age differences in regional brain volumes.

Figure 6

Age differences in lateral bias for three types of turns. Asymmetry direction: R > L positive.

Figure 7

Lateral bias for regular turns vs. volume asymmetry. Asymmetry direction: R > L positive.

Figure 8

Lateral bias in reversals vs. volume asymmetry. Asymmetry direction: R > L positive.

Figure 9

Lateral bias in regular turns vs. hippocampal volume asymmetry in younger participants (less than 41 years of age). Asymmetry direction: R > L positive.