Is effect of transcranial direct current stimulation on visuomotor coordination dependent on task difficulty?

Transcranial direct current stimulation （tDCS）, an emerging technique for non-invasive brain stimulation, is increasingly used to induce changes in cortical excitability and modulate motor behavior, especially for upper limbs. The purpose of this study was to investigate the effects of tDCS of the primary motor cortex on visuomotor coordination based on three levels of task difficulty in healthy subjects. Thirty-eight healthy participants underwent real tDCS or sham tDCS. Using a single-blind, sham-controlled crossover design, tDCS was applied to the primary motor cortex. For real tDCS conditions, tDCS intensity was 1 mA while stimulation was applied for 15 minutes. For the sham tDCS, electrodes were placed in the same position, but the stimu- lator was turned off after 5 seconds. Visuomotor tracking task, consisting of three levels （levels 1, 2, 3） of difficulty with higher level indicating greater difficulty, was performed before and after tDCS application. At level 2, real tDCS of the primary motor cortex improved the accurate index compared to the sham tDCS. However, at levels 1 and 3, the accurate index was not significantly increased after real tDCS compared to the sham tDCS. These findings suggest that tasks of mod- erate difficulty may improve visuomotor coordination in healthy subjects when tDCS is applied compared with easier or more difficult tasks.

Collaborative information seeking: An investigation of community members' behavior

Purpose： This article reports on an experiment that tested community members＇ collaborative information seeking （CIS） behavior, with an emphasis on how community type and task difficulty can affect user behavior and user awareness in collaboration.Design/methodology/approach： We carried out a laboratory study with 18 participants in 9 pairs using an experimental CIS system. Data were collected from questionnaires, Web logs and semi-structured interviews. Descriptive statistics and two-way analysis of variance （ANOVA） were used for data analysis. Findings： Compared with non-community members, community participants had a better understanding of search tasks and were aware of the ways of completing tasks successfully. They did not depend on the information retrieval system when constructing search queries and would adopt diversified cooperation strategies. They were more likely to recommend information to their partners. However, no significant difference was found between subject- based community and interest-based community in CIS practices and user awareness in collaboration. In addition, task difficulty only influenced user preference of issuing queries and confidence of completing search tasks. Research limitations： Our work was limited by the community type we chose and the small group size, which could affect the generalizability of our findings and should be addressed in future studies. Practical implications： The study results will help inform information system designers as they design collaborative systems to facilitate social communication in the information seeking process. Originality/value： Few studies have investigated community participants＇ information seeking practices. This study provides insights into community-based CIS behavior. The findings will help us understand social interactions among community members during their information seeking process.