Socio-constructivism and connectivism theories pinpoint the importance of collaboration for learning. Nevertheless , the online social interactions underlying the collaboration processes are still not well understood. As a result, learning designers have difficulties creating effective collaborative activities in Massive Open On-line Courses (MOOCs). As for online learners, they are often isolated and require a lot of self-regulation to succeed. The research effort presented in this paper covers a review of visualization techniques supporting the online collaborative learning process. Our findings show that some visualizations have the potential to develop the learners' reflexivity. Therefore, we give an overview of collaboration importance and how it could be enhanced with such visualizations. Our goal is to identify a new approach to visualize learners' activities in MOOCs, while supporting collaboration and self-regulation.