Spatiotopic and retinotopic memory in the context of natural images

Abstract

Neural responses throughout the visual cortex encode stimulus location in a retinotopic (i.e., eye-centered) reference frame, and memory for stimulus position is most precise in retinal coordinates. Yet visual perception is spatiotopic: objects are perceived as stationary, even though eye movements cause frequent displacement of their location on the retina. Previous studies found that, after a single saccade, memory of retinotopic locations is more accurate than memory of spatiotopic locations. However, it is not known whether various aspects of natural viewing affect the retinotopic reference frame advantage. We found that the retinotopic advantage may in part depend on a retinal afterimage, which can be effectively nullified through backwards masking. Moreover, in the presence of natural scenes, spatiotopic memory is more accurate than retinotopic memory, but only when subjects are provided sufficient time to process the scene before the eye movement. Our results demonstrate that retinotopic memory is not always more accurate than spatiotopic memory and that the fidelity of memory traces in both reference frames are sensitive to the presence of contextual cues.

Figure 1.

Experimental design. (A) Experiment design for the spatiotopic and retinotopic tasks. For the spatiotopic task, the memory cue locations (black dots) are at the same physical location as the correct memory locations (blue dots), so the black dots are hidden behind the blue in this panel. (B–D) Example trials for Experiments 1 through 3. Observers were instructed to fixate on the white dot until a black memory cue flashed on the screen. After another brief fixation period, observers made a saccade to the new location of the memory cue. A successful saccade within 800 ms prompted the mouse to appear on the screen, signaling observers to move the mouse to the remembered location. A green feedback square indicated the correct response location. (C) In Experiment 2, a salient visual mask appeared after the memory cue. (D) In Experiment 3, a naturalistic image background appeared before each trial. The fixation dot was red to make it easier for observers to find on the screen.

Figure 2.

Memory accuracy in experiment 1 (gray background), experiment 2 (gray background with mask), and experiment 3 (image background). * indicate p < 0.05.

Figure 3.

Memory accuracy in Experiment 1 (A), Experiment 2 (B), and Experiment 3 (C), with data broken down by saccade direction. *P < 0.05.

Figure 4.

(A) Experiment design for Experiments 4 and 5. Three different background conditions (gray screen, image background, scrambled texture) were presented in a randomized order. There was only free viewing in Experiment 4. Example trial presented to the right. (B) Memory accuracy in Experiment 4 (free viewing). (C) Memory accuracy in Experiment 5 (no free viewing). *P < 0.05.

Figure 5.

Experimental design and results for Experiment 6. (A), Example trials for Experiment 6 (B), Memory accuracy for Experiment 6 with data broken down by saccade direction. *P < 0.05.