Movement planning and attentional control of visuospatial working memory: evidence from a grasp-to-place task.

In this study, we have investigated the influence of available attentional resources on the dual-task costs of implementing a new action plan and the influence of movement planning on the transfer of information into visuospatial working memory. To approach these two questions, we have used a motor-memory dual-task design in which participants grasped a sphere and planned a placing movement toward a left or right target according to a directional arrow. Subsequently, they encoded a centrally presented memory stimulus (4 × 4 symbol matrix). While maintaining the information in working memory, a visual stay/change cue (presented on the left, center or right) either confirmed or reversed the planned movement direction. That is, participants had to execute either the prepared or the re-planned movement and finally reported the symbols at leisure. The results show that both, shifts of spatial attention required to process the incongruent stay/change cues and movement re-planning, constitute processing bottlenecks as they both reduced visuospatial working memory performance. Importantly, the spatial attention shifts and movement re-planning appeared to be independent of each other. Further, we found that the initial preparation of the placing movement influenced the report pattern of the central working memory stimulus. Preparing a leftward movement resulted in better memory performance for the left stimulus side, while the preparation of a rightward movement resulted in better memory performance for the right stimulus side. Hence, movement planning influenced the transfer of information into the capacity-limited working memory store. Therefore, our results suggest complex interactions in that the processes involved in movement planning, spatial attention and visuospatial working memory are functionally correlated but not linked in a mandatory fashion.

Graft-versus-host reaction in small bowel transplantation and possibilities for its circumvention.

To describe GVHR in small bowel transplantation and its underlying mechanisms and to find methods for circumventing that response, accessory small bowel transplantation was carried out in the rat model. Animals not treated with cyclosporine, irradiation, or removal of the mesenteric lymph nodes of the graft died within 22 days postoperatively due to graft versus host disease. Mesenteric lymph nodes of the graft and recipient spleen and peripheral lymph nodes showed strong immunologic stimulation histologically and high antihost T-cell-mediated cytotoxic antihost reactivity. Seventy-one percent of the animals that had received 15 mg of cyclosporine per kilogram body weight orally survived 150 days after transplantation. After donor irradiation with 50 rads, 77 percent of the recipients survived 120 days. After microsurgical removal of the mesenteric lymph nodes of the graft, 89 percent survived 120 days. We conclude that GVHR plays an important role in small bowel transplantation and that the experimental regimens of donor, graft, and recipient treatment described herein have proved their efficacy for circumventing GVHR.

The functional role of working memory in the (re-)planning and execution of grasping movements.

Three experiments were conducted to dissociate movement planning costs and movement execution costs in working memory (WM). The aim of the study was to clarify what kind of WM processes (verbal, spatial, or both) are recruited during movement planning and movement execution. Therefore, a WM task (verbal and spatial versions) was combined with a high-precision manual action. Participants initially planned a placing movement toward 1 of 2 targets, subsequently encoded verbal or spatial information in WM, and then executed the movement during the retention phase. We tested the impact of movement execution on memory performance (Experiment 1), the role of WM task difficulty as a moderating variable in motor-memory interactions (Experiment 2), and the impact of implementing a new motor plan during memory retention (Experiment 3). Our results show that movement execution disrupted spatial more than verbal memory (Experiment 1) and that this domain-specific interference pattern was independent of WM task difficulty (Experiment 2). Hence, the results of Experiments 1 and 2 demonstrate that executing a prepared movement recruits domain-specific visuospatial memory resources. Experiment 3 involved trials that required the implementation of a new motor plan. The additional planning requirement during the retention phase reduced performance in both WM tasks in equal measure beyond the relative movement execution costs observed in Experiments 1 and 2. These results provide evidence for distinct roles of WM in manual actions, with action execution requiring principally modality-specific capacities and (re-)planning engaging modality-general WM resources.

The costs of changing an intended action: movement planning, but not execution, interferes with verbal working memory.

How much cognitive effort does it take to change a movement plan? In previous studies, it has been shown that humans plan and represent actions in advance, but it remains unclear whether or not action planning and verbal working memory share cognitive resources. Using a novel experimental paradigm, we combined in two experiments a grasp-to-place task with a verbal working memory task. Participants planned a placing movement toward one of two target positions and subsequently encoded and maintained visually presented letters. Both experiments revealed that re-planning the intended action reduced letter recall performance; execution time, however, was not influenced by action modifications. The results of Experiment 2 suggest that the action's interference with verbal working memory arose during the planning rather than the execution phase of the movement. Together, our results strongly suggest that movement planning and verbal working memory share common cognitive resources.