The Virtual Tray of Objects Task as a novel method to electrophysiologically measure visuo-spatial recognition memory

We explored a novel method to electrophysiologically measure visuo-spatial recognition memory using a modified version of the Virtual Tray of Objects Task (VTOT). Event-related potentials (ERP) were recorded from 18 healthy volunteers during performance in the VTOT. Participants were required to detect random repetitions of three-dimensional visual stimuli (OLD) and to refrain from responding to non-repeated stimuli (NEW). Differences in ERP between the NEW and OLD conditions were tested for statistical significance using assumption-free non-parametric analyses. Further, a correlation between ERP and behavioral measures was sought. Significant OLD-NEW effects were found for four ERP components showing distinct spatio-temporal characteristics: a posterior positive component appearing at 100 ms (P100), a left-lateralized negative component peaking at ≈250 ms (N250), a frontal negative component at ≈300-450 ms (FN400), and a right late frontal negativity (rLFN) at ≈500-720 ms. Moreover, individual differences in the OLD-NEW effect computed for the rLFN positively correlated with repeated stimulus recognition efficiency. However, there were no late left parietal P600 old/new effects. These findings suggest that the P100 component might reflect early visual perception processes taking place during performance in the task, whereas the N250 and FN400 components could be linked to stimulus-dependent access to visual memory representations and familiarity-related processes, respectively. In contrast, we propose that the rLFN component could be associated with higher-level cognitive functions, such as attention and monitoring processes. Altogether, our results suggest that the ERP version of the VTOT could play a role in the electrophysiological assessment of visuo-spatial memory and related sub-processes.