Maintaining fixation does not increase demands on working memory relative to free viewing

Differential eye movements and greater pupil size during mental scene construction in autobiographical recall

There is growing evidence supporting a role for eye movements during autobiographical recall, but their potential functionality remains unclear. We hypothesise that the oculomotor system facilitates the process of mental scene construction, in which complex scenes associated with an autobiographical event are generated and maintained during recall. To explore this, we examined spontaneous eye movements during retrieval of cued autobiographical memories. Participants' verbal descriptions of each memory were recorded in synchronisation with their eye movements and pupil size during recall. For each memory participants described the place (details of the environment where the event took place) and the event (details of what happened). Narratives were analyzed using the Autobiographical Interview procedure, which separated internal spatial (place) and non-spatial (event, thoughts and emotion) details. Eye movements during recall of spatial details had significantly higher fixation duration and smaller saccade amplitude and peak velocity, and a higher number of consecutive unidirectional saccades, in comparison to recall of non-spatial details. Recurrence quantification analysis indicated longer sequences of refixations and more repetitions of the same fixation pattern when participants described spatial details. Recall of spatial details was also associated with significantly greater pupil area. Overall findings are consistent with the spontaneous production of more structured saccade patterns and greater cognitive load during the recall of internal spatial episodic scene details in comparison to episodic non-spatial details. These results are consistent with the oculomotor system facilitating the activation and correct positioning of elements of a complex scene relative to other imagined elements during autobiographical recall.

"Look at the future": Maintained fixation impoverishes future thinking

We evaluated the relationship between eye movements and future thinking. More specifically, we evaluated whether maintained fixation could influence cognitive characteristics of future thinking. We invited participants to imagine future events in two conditions: while freely exploring a white wall and while fixating a cross on the wall. Results demonstrated fewer and longer fixations, as well as fewer and shorter saccades during maintained fixation condition than in the free gaze condition. Shorter total amplitude of saccades was also observed during the maintained fixation condition than during the free-gaze condition. Regarding the cognitive characteristics of future thinking, fewer spatiotemporal details and less visual imagery, slower retrieval time, and shorter descriptions were observed for future thinking during maintained fixation than during free-gaze condition. These results demonstrate that maintaining fixation results in an effortful construction of future scenarios. We suggest that maintained fixation limits the cognitive resources that are required for future thinking.

Unrestricted eye movements strengthen effective connectivity from hippocampal to oculomotor regions during scene construction

Scene construction is a key component of memory recall, navigation, and future imagining, and relies on the medial temporal lobes (MTL). A parallel body of work suggests that eye movements may enable the imagination and construction of scenes, even in the absence of external visual input. There are vast structural and functional connections between regions of the MTL and those of the oculomotor system. However, the directionality of connections between the MTL and oculomotor control regions, and how it relates to scene construction, has not been studied directly in human neuroimaging. In the current study, we used dynamic causal modeling (DCM) to interrogate effective connectivity between the MTL and oculomotor regions using a scene construction task in which participants' eye movements were either restricted (fixed-viewing) or unrestricted (free-viewing). By omitting external visual input, and by contrasting free- versus fixed- viewing, the directionality of neural connectivity during scene construction could be determined. As opposed to when eye movements were restricted, allowing free-viewing during construction of scenes strengthened top-down connections from the MTL to the frontal eye fields, and to lower-level cortical visual processing regions, suppressed bottom-up connections along the visual stream, and enhanced vividness of the constructed scenes. Taken together, these findings provide novel, non-invasive evidence for the underlying, directional, connectivity between the MTL memory system and oculomotor system associated with constructing vivid mental representations of scenes.

Harnessing Visual Imagery and Oculomotor Behaviour to Understand Prospection

Much of the rich internal world constructed by humans is derived from, and experienced through, visual mental imagery. Despite growing appreciation of visual exploration in guiding episodic memory processes, extant theories of prospection have yet to accommodate the precise role of visual mental imagery in the service of future-oriented thinking. We propose that the construction of future events relies on the assimilation of perceptual details originally experienced, and subsequently reinstantiated, predominantly in the visual domain. Individual differences in the capacity to summon discrete aspects of visual imagery can therefore account for the diversity of content generated by humans during future simulation. Our integrative framework provides a novel testbed to query alterations in future thinking in health and disease.

Restricting Visual Exploration Directly Impedes Neural Activity, Functional Connectivity, and Memory

We move our eyes to explore the visual world, extract information, and create memories. The number of gaze fixations-the stops that the eyes make-has been shown to correlate with activity in the hippocampus, a region critical for memory, and with later recognition memory. Here, we combined eyetracking with fMRI to provide direct evidence for the relationships between gaze fixations, neural activity, and memory during scene viewing. Compared to free viewing, fixating a single location reduced: 1) subsequent memory, 2) neural activity along the ventral visual stream into the hippocampus, 3) neural similarity between effects of subsequent memory and visual exploration, and 4) functional connectivity among the hippocampus, parahippocampal place area, and other cortical regions. Gaze fixations were uniquely related to hippocampal activity, even after controlling for neural effects due to subsequent memory. Therefore, this study provides key causal evidence supporting the notion that the oculomotor and memory systems are intrinsically related at both the behavioral and neural level. Individual gaze fixations may provide the basic unit of information on which memory binding processes operate.

How Older Adults Remember the World Depends On How They See It

Age-related changes in visual exploration and memory have typically been studied separately. However, recent evidence suggests that mnemonic processes both affect, and are affected by, eye movements (EMs). Thus, by relating older adults' memory deficits to age-specific visual exploration patterns, we can improve upon models of cognitive aging.

Eye movements support behavioral pattern completion

The ability to recall a detailed event from a simple reminder is supported by pattern completion, a cognitive operation performed by the hippocampus wherein existing mnemonic representations are retrieved from incomplete input. In behavioral studies, pattern completion is often inferred through the false endorsement of lure (i.e., similar) items as old. However, evidence that such a response is due to the specific retrieval of a similar, previously encoded item is severely lacking. We used eye movement (EM) monitoring during a partial-cue recognition memory task to index reinstatement of lure images behaviorally via the recapitulation of encoding-related EMs or gaze reinstatement. Participants reinstated encoding-related EMs following degraded retrieval cues and this reinstatement was negatively correlated with accuracy for lure images, suggesting that retrieval of existing representations (i.e., pattern completion) underlies lure false alarms. Our findings provide evidence linking gaze reinstatement and pattern completion and advance a functional role for EMs in memory retrieval.