Differential Performance of Children and Adults in a Vision-Deprived Maze Spatial Navigation Task and Exploration of the Impact of tDCS over the Right Posterior Parietal Cortex on Performance in Adults

Abstract

Spatial navigation involves the use of external (allocentric) and internal (egocentric) processing. These processes interact differentially depending on age. In order to explore the effectiveness of these interactions in different age groups (study 1), we compared the performance of children and adults in a two-session spatial maze task. This task was performed under deprived vision, thus preventing visual cues critical for allocentric processing. Number of correct performances and performance time were recorded as outcome measures. We recruited thirty healthy participants for the children (mean age 10.97 ± 0.55) and the adult (mean age 21.16 ± 1.76) groups, respectively. The results revealed a significantly higher number of correct actions and shorter performance times during maze solving in children compared to adults. These differences between children and adults might be due to developmental and cortical reorganization factors influencing egocentric processing. Assuming that activation of the posterior parietal cortex (PPC) facilitates egocentric spatial processing, we applied excitatory anodal tDCS over the right PPC in a second study with a different healthy adult group (N = 30, mean age 21.23 ± 2.01). Using the same spatial navigation task as in study 1, we evaluated possible performance improvements in adults associated with this neuromodulation method. Compared to a sham stimulation group, anodal tDCS over the right PPC did not significantly improve spatial task performance.

Keywords: adults; children; maze task; posterior parietal cortex; spatial navigation; tDCS.

Figure 1

Spatial navigation task in a physical maze. (A). Outcome measures were obtained in two sessions. All participants performed two versions of the task one week apart between each version, in counterbalanced order across participants. In order to balance the difficulty of both versions of the task, the routes were mirror images of each other. (B) In each version, a different 10-step route was shown and performed by one of the researchers before the start of the task. Then, participants were visually deprived by opaque glasses. During task performance, the research staff provided verbal feedback about success or failure at each step (right, left, or straight ahead) and helped participants to return to the starting point after each wrong step. The task ended after 20 unsuccessful trials. The number of correct performances in each session and performance time were recorded by a second member of the research staff.

Figure 2

Spatial navigation task performance of children (○) and adults (◊). (A) Number of correct performances of the task. (B) Performance time in minutes. (*) Significant differences between groups. (#) Significant differences between sessions (session 1 and 2). Error bars represent standard error of means (SEM). These results indicate that children perform the spatial task correctly at a higher rate than adults in both sessions. Furthermore, children took less time to complete the task compared to adults, and, additionally, they improved their performance times in the second session.

Figure 3

Intensity of the electric field induced by tDCS applied over the right posterior parietal cortex (PPC, corresponding to the P4 EEG electrode position). The images from left to right show, respectively, a dorsal (A), frontal (B), and lateral (C) view of the brain. The electric field (normative strength: normE) intensity (V/m) is represented by the color bar. The red colors (larger number depicted in the color bar) indicate higher electric field intensity—with the highest intensity corresponding to the right parietal cortex and, particularly, the PPC region (intensity values within the red band of the color bar, panel (C))—and a considerable loss of intensity from the regions adjacent to the cortical target. SimNIBS 4.1.0 (Simulation of Non-Invasive Brain Stimulation) was used for modeling the electric field. Red and blue electrodes of the SimNIBS output brain images represent the anodal and cathodal electrode positions, respectively. These positions should not be considered as a direct position over the brain targets, considering the anatomical space between brain and electrode positions over the head.

Figure 4

Spatial navigation task performance of adults under right posterior parietal cortex anodal vs. sham tDCS. (A) Number of correct performances of the task. (B) Performance time in minutes. Error bars represent standard error of means (SEM). These results suggest that, under the stimulation parameters and the cortical target used in the present study, the application of the tDCS protocol did not result in a modulation of performance of a spatial maze task in adults.