Eric Orriols

The influence of action on episodic memory: A virtual reality study

A range of empirical findings suggest that active learning is important for memory. However, few studies have focused on the mechanisms underlying this enactment effect in episodic memory using complex environments. Research using virtual reality has yielded inconsistent results. We postulated that the effect of action depends on the degree of interaction with the environment and freedom in the planning of an itinerary. To test these hypotheses, we disentangled the interaction and planning components of action to investigate whether each enhances factual and spatial memory. Seventy-two participants (36 male and 36 female) explored a virtual town in one of three experimental conditions: (a) a passive condition where participants were immersed as passenger of the car (no interaction, no planning); (b) a planning-only condition (the subject chose the itinerary but did not drive the car); (c) an interaction-only condition (the subject drove the car but the itinerary was fixed). We found that itinerary choice and motor control both enhanced spatial memory, while factual memory was impaired by online motor control. The role of action in memory is discussed.

Intermittent theta burst stimulation over left BA10 enhances virtual reality-based prospective memory in healthy aged subjects

Prospective memory (PM) refers to a complex cognitive ability that underpins the delayed execution of previously formulated intentions. PM performance declines early in normal aging and this process is accentuated in Alzheimers disease. The left frontopolar cortex (BA10) has been consistently assigned a major role in PM functioning, but whether it can be noninvasively modulated to enhance PM performance in aged people has not been addressed so far. Here, we investigated the effects of modulating left BA10 by means of theta burst stimulation (TBS), using either excitatory (intermittent TBS), inhibitory (continuous TBS) or control (vertex) TBS in healthy aged subjects. The behavioral effects were assessed using a reliable and ecological virtual reality PM task that included both event- and time-based retrievals. As compared with vertex stimulation, event-based PM performance significantly improved after excitatory stimulation, whereas inhibitory stimulation had no significant effect. Additionally, and across the different types of stimulation, performance for congruent links between the event-based PM cue and the action to be performed was significantly better as compared with incongruent links. In conclusion, intermittent TBS might provide a relevant interventional strategy to counteract the decline of cognitive functions and memory abilities in normal aging.

The planning of a sequence of saccades in pro-and antisaccade tasks : Influence of visual integration time and concurrent motor processing

Previous studies have shown that a saccade is coded in a specific reference frame according to its goal: to aim for a new object or to explore an object which has already been fixated. In a two saccade sequence, the second saccade aiming for a new object is programmed in a retinocentric reference frame in which the spatial location of the second object is stored in spatial memory before the first saccade and updated after its execution. The second saccade exploring the same object is coded in an oculocentric reference frame in which object size is directly transformed into a fixed motor vector, encoded in motor memory before the first saccade and simply applied after its execution. The integration of parafoveal visual information appears to be crucial in the selection of the appropriate reference frame. The two experiments presented here investigate how and when the saccadic system integrates visual information to plan a sequence of saccades. In separate blocks, subjects were asked to execute a sequence of prosaccades directed toward a single object or two short objects, or to execute a sequence of antisaccades in the opposite direction of the stimuli. The latency of the initial saccade was modulated by using the Gap-200, Gap-0 and Overlap-600 ms paradigms. The results show that the time available for segmenting the visual stimulation into discrete objects and application of a specific reference frame according to this segmentation is critical for saccadic planning.

Landmark and route knowledge in children's spatial representation of a virtual environment.

This study investigates the development of landmark and route knowledge in complex wayfinding situations. It focuses on how children (aged 6, 8, and 10 years) and young adults (n = 79) indicate, recognize, and bind landmarks and directions in both verbal and visuo-spatial tasks after learning a virtual route. Performance in these tasks is also related to general verbal and visuo-spatial abilities as assessed by independent standardized tests (attention, working memory, perception of direction, production and comprehension of spatial terms, sentences and stories). The results first show that the quantity and quality of landmarks and directions produced and recognized by participants in both verbal and visuo-spatial tasks increased with age. In addition, an increase with age was observed in participants’ selection of decisional landmarks (i.e., landmarks associated with a change of direction), as well as in their capacity to bind landmarks and directions. Our results support the view that children first acquire landmark knowledge, then route knowledge, as shown by their late developing ability to bind knowledge of directions and landmarks. Overall, the quality of verbal and visuo-spatial information in participants’ spatial representations was found to vary mostly with their visuo-spatial abilities (attention and perception of directions) and not with their verbal abilities. Interestingly, however, when asked to recognize landmarks encountered during the route, participants show an increasing bias with age toward choosing a related landmark of the same category, regardless of its visual characteristics, i.e., they incorrectly choose the picture of another fountain. The discussion highlights the need for further studies to determine more precisely the role of verbal and visuo-spatial knowledge and the nature of how children learn to represent and memorize routes.

Virtual reality as an ecologically valid tool for assessing multifaceted episodic memory in children and adolescents

The majority of episodic memory (EM) tests are far removed from what we experience in daily life and from the definition of this type of memory. This study examines the developmental trajectory of the main aspects of episodic memory—what, where, and when—and of feature binding in a naturalistic virtual environment. A population of 125 participants aged from 6 to 24 years was asked to navigate, by using a joystick, in a virtual urban environment composed of specific areas, and to memorize as many elements as possible (e.g., scenes, details, spatial and temporal contexts). The ability to recall factual content associated to details or spatiotemporal context increased steadily from the age of 8 to young adulthood. These results indicate main developmental differences in feature binding abilities in naturalistic events which are very sensitive to age in comparison with a standard EM assessment. Virtual reality therefore appears to be an appropriate technique to assess crucial aspects of EM development in children and adolescents and it should provide helpful tools for the detection of subtle memory deficits.

Is binding decline the main source of the ageing effect on prospective memory? A ride in a virtual town

ABSTRACT Objective: This study was designed to improve our understanding of prospective memory (PM) changes in ageing, and to identify the cognitive correlates of PM decline, using a virtual environment, to provide a more realistic assessment than traditional laboratory tasks. Design: Thirty-five young and 29 older individuals exposed to a virtual town were asked to recall three event-based intentions with a strong link between prospective and retrospective components, three event-based intentions with a weak link, and three time-based intentions. They also underwent retrospective episodic memory, executive functions, binding in working memory, processing speed, and time estimation assessments. Results: Older individuals recalled fewer intentions than young adults. While age-related PM decline affected the recall of both prospective and retrospective components, the recall of the latter seemed more challenging for older individuals when the link was weak. This PM decline was linked to an age-related decline in the binding process in working memory, as well as in processing speed, executive functioning, and episodic memory, depending on the nature of intentions. Conclusion: PM appears to be sensitive to ageing, even when the device is thought to be ecological. This decline is particularly pronounced when controlled processes are needed.

Do Preterm Infants Perceive Temporal Synchrony? An Analysis with the Eye-Tracking System

The aim of this study was to investigate auditory–visual temporal asynchrony in preterm infants using a habituation procedure coupled with an eye-tracking system in order to examine visual behavior accurately and determine specific visual areas of interest. Sixteen term infants, twelve low-risk near-term (LBW) preterm infants and eight Very Low Birth Weight (VLBW) preterm infants were tested at four months post term. Infants were habituated with an auditory–visual synchronic situation: a visual ball bounced back in synchrony with an auditory sound. In the test phase, an asynchronized situation and a synchronized situation were presented alternately three times. The results showed that VLBW infants spent more time looking at the target before being habituated compared to LBW preterm infants and full-term infants.Specific areas of interest showed that VLBW infants spent less time on the target than LBW and full-term infants and had a more heterogeneous visual exploration. Nevertheless, VLBW infants had the same novelty reaction as the other infant groups. Moreover, the study of areas of interest revealed that whatever the age group, infants looked more at the area where the sound was produced during the asynchronized trial. This result suggests that infants perceive asynchrony. We suggest that VLBW preterm infants show the same ability to habituate and novelty recovery through an early learning experience due to earlier additional extra-uterine exposure.