Direction specific costs to spatial working memory from saccadic and spatial remapping

Visuospatial memory in apraxia: Exploring quantitative drawing metrics to assess the representation of local and global information

Neuropsychological evidence suggests that visuospatial memory is subserved by two separable processing systems, with dorsal underpinnings for global form and ventral underpinnings for the integration of part elements. Previous drawing studies have explored the effects of Gestalt organisation upon memory for hierarchical stimuli, and we here present an exploratory study of an apraxic dorsal stream patient's (MH) performance. We presented MH with a stimulus set (previously reported by Riddoch et al., Cognitive Neuropsychology, 20(7), 641-671, 2003) and devised a novel quantitative scoring system to obtain a finer grain of insight into performance. Stimuli possessed either good or poor Gestalt qualities and were reproduced in a copy condition and two visual memory conditions (with unlimited viewing before the model was removed, or with 3 s viewing). MH's copying performance was impaired in comparison to younger adult and age-matched older adult controls, with a variety of errors at the local level but relatively few at the global level. However, his performance in the visual memory conditions revealed impairments at the global level. For all participants, drawing errors were modulated by the Gestalt qualities of the stimuli, with accuracy at the global and local levels being lesser for poor global stimuli in all conditions. These data extend previous observations of this patient, and support theories that posit interaction between dorsal and ventral streams in the representation of hierarchical stimuli. We discuss the implications of these findings for our understanding of visuospatial memory in neurological patients, and also evaluate the application of quantitative metrics to the interpretation of drawings.

Working memory in action: Transsaccadic working memory deficits in the left visual field and after transcallosal remapping

Every waking second, we make three saccadic eye movements that move our retinal images. Thus, to attain a coherent image of the world we need to remember visuo-spatial information across saccades. But transsaccadic working memory (tWM) remains poorly understood. Crucially, there has been a debate whether there are any differences in tWM for the left vs. right visual field and depending on saccade direction. However, previous studies have probed tWM with minimal loads whereas spatial differences might arise with higher loads. Here we employed a task that probed higher memory load for spatial information in the left and right visual field and with horizontal as well as vertical saccades. We captured several measures of precision and accuracy of performance that, when submitted to principal component analysis, produced two components. Component 1, mainly associated with precision, yielded greater error for the left than the right visual field. Component 2 was associated with performance accuracy and unexpectedly produced a disadvantage after rightward saccades. Both components showed that performance was worse when rightward or leftward saccades afforded a shift of memory representations between visual fields compared to remapping within the same field. Our study offers several novel findings. It is the first to show that tWM involves at least two components likely reflecting working memory capacity and strategic aspects of working memory, respectively. Reduced capacity for the left, rather than the right visual field is consistent with how the left and right visual fields are known to be represented in the two hemispheres. Remapping difficulties between visual fields is consistent with the limited information transfer across the corpus callosum. Finally, the impact of rightward saccades on working memory might be due to greater interference of the accompanying shifts of attention. Our results highlight the dynamic nature of transsaccadic working memory.

Teaching Physiotherapy Students Physical Examination Skills by Using Photogrammetry: A Randomized Control Trial of 3- Versus 2-Dimensional Images

INTRODUCTION

Education research explains how healthcare professional training could be more efficient and effective by integrating simulation technology. Despite its relevance in training medical students, the evidence of its effectiveness in the manual skill training of physiotherapy students remains limited. The aim of this study was to compare the effectiveness of 3-dimensional (3D) images of real objects produced by photogrammetry and traditional 2-dimensional (2D) images when introducing manual therapy skills to undergraduate physiotherapy students via an online course.

METHODS

In a randomized controlled trial, a group of first-year physiotherapy bachelor honor degree students participated in a 2-hour online course on 3 manual assessment skills: cervical compression, distraction, and flexion-rotation tests. They demonstrated 2 sets of learning materials, including either 3D images of real rotating objects using close-range photogrammetry (experimental group) or traditional 2D images (control group). After their respective training, an Objective Structured Clinical Evaluation procedure was conducted to demonstrate their knowledge about the techniques. A standardized 9-item practical performance test was used as the primary outcome measure for the analyses.

RESULTS

Seventy-seven students participated in the study. The average Objective Structured Clinical Evaluation score for the experimental group (n = 40) was 41.3/50 (±3.9) and the control group (n = 37) was 39.1/50 (±4.5, P = 0.02).

CONCLUSIONS

For learning 3 cervical spine assessment skills, this study shows that photogrammetry creates 3D images of real rotating objects that are more effective than 2D images for first-year physiotherapy students.

On-item fixations during serial encoding do not affect spatial working memory

Ample evidence suggests that there is overlap between the eye-movement system and spatial working memory. Such overlapping structures or capacities may result in interference on the one hand and beneficial support on the other. We investigated eye-movement control during encoding of verbal or spatial information, keeping the display the same between tasks. Saccades to to-be-encoded items were scarce during spatial encoding in comparison with verbal encoding. However, despite replicating this difference across different tasks (serial, free recall) and presentation modalities (simultaneous, sequential presentation), we found no relation between item fixations and memory performance-that is, no costs or benefits. Inducing a change from covert to overt encoding did not affect spatial memory performance as well. In contrast, regressive fixations on prior items, that were no longer on the screen, were associated with increased spatial memory performance. Regressions occurred mainly at the end of the encoding period and were targeted at the first presented item. Our results suggest a dissociation between two types of fixations that accompany serial spatial memory: On-item fixations are epiphenomenal; regressions indicate rehearsal or output preparation.

Working memory in action: inspecting the systematic and unsystematic errors of spatial memory across saccades

Our ability to interact with the world depends on memory buffers that flexibly store and process information for short periods of time. Current working memory research, however, mainly uses tasks that avoid eye movements, whereas in daily life we need to remember information across saccades. Because saccades disrupt perception and attention, the brain might use special transsaccadic memory systems. Therefore, to compare working memory systems between and across saccades, the current study devised transsaccadic memory tasks that evaluated the influence of memory load on several kinds of systematic and unsystematic spatial errors, and tested whether these measures predicted performance in more established working memory paradigms. Experiment 1 used a line intersection task that had people integrate lines shown before and after saccades, and it administered a 2-back task. Experiments 2 and 3 asked people to point at one of several locations within a memory array flashed before an eye movement, and we tested change detection and 2-back performance. We found that unsystematic transsaccadic errors increased with memory load and were correlated with 2-back performance. Systematic errors produced similar results, although effects varied as a function of the geometric layout of the memory arrays. Surprisingly, transsaccadic errors did not predict change detection performance despite the latter being a widely accepted measure of working memory capacity. Our results suggest that working memory systems between and across saccades share, in part, similar neural resources. Nevertheless, our data highlight the importance of investigating working memory across saccades.

Deficits in reflexive covert attention following cerebellar injury

Traditionally the cerebellum has been known for its important role in coordinating motor output. Over the past 15 years numerous studies have indicated that the cerebellum plays a role in a variety of cognitive functions including working memory, language, perceptual functions, and emotion. In addition, recent work suggests that regions of the cerebellum involved in eye movements also play a role in controlling covert visual attention. Here we investigated whether regions of the cerebellum that are not strictly tied to the control of eye movements might also contribute to covert attention. To address this question we examined the effects of circumscribed cerebellar lesions on reflexive covert attention in a group of patients (n = 11) without any gross motor or oculomotor deficits, and compared their performance to a group of age-matched controls (n = 11). Results indicated that the traditional RT advantage for validly cued targets was significantly smaller at the shortest (50 ms) SOA for cerebellar patients compared to controls. Critically, a lesion overlap analysis indicated that this deficit in the rapid deployment of attention was linked to damage in Crus I and Crus II of the lateral cerebellum. Importantly, both cerebellar regions have connections to non-motor regions of the prefrontal and posterior parietal cortices—regions important for controlling visuospatial attention. Together, these data provide converging evidence that both lateral and midline regions of the cerebellum play an important role in the control of reflexive covert visual attention.

Spatial working memory deficits represent a core challenge for rehabilitating neglect

Left neglect following right hemisphere injury is a debilitating disorder that has proven extremely difficult to rehabilitate. Traditional models of neglect have focused on impaired spatial attention as the core deficit and as such, most rehabilitation methods have tried to improve attentional processes. However, many of these techniques (e.g., visual scanning training, caloric stimulation, neck muscle vibration) produce only short-lived effects, or are too uncomfortable to use as a routine treatment. More recently, many investigators have begun examining the beneficial effects of prism adaptation for the treatment of neglect. Although prism adaptation has been shown to have some beneficial effects on both overt and covert spatial attention, it does not reliably alter many of the perceptual biases evident in neglect. One of the challenges of neglect rehabilitation may lie in the heterogeneous nature of the deficits. Most notably, a number of researchers have shown that neglect patients present with severe deficits in spatial working memory (SWM) in addition to their attentional impairments. Given that SWM can be seen as a foundational cognitive mechanism, critical for a wide range of other functions, any deficit in SWM memory will undoubtedly have severe consequences. In the current review we examine the evidence for SWM deficits in neglect and propose that it constitutes a core component of the syndrome. We present preliminary data which suggest that at least one current rehabilitation method (prism adaptation) has no effect on SWM deficits in neglect. Finally, we end by reviewing recent work that examines the effectiveness of SWM training and how SWM training may prove to be a useful avenue for future rehabilitative efforts in patients with neglect.

Statistical learning as a tool for rehabilitation in spatial neglect

We propose that neglect includes a disorder of representational updating. Representational updating refers to our ability to build mental models and adapt those models to changing experience. This updating ability depends on the processes of priming, working memory, and statistical learning. These processes in turn interact with our capabilities for sustained attention and precise temporal processing. We review evidence showing that all these non-spatial abilities are impaired in neglect, and we discuss how recognition of such deficits can lead to novel approaches for rehabilitating neglect.