Esther Visser performed her 1st MSc internship (Research Master Brain & Cognitive Sciences at UvA) within the team of Michel van den Oever, with Mariana Matos as her daily supervisors from January 2015 until July 2015. Her project involved optogenetic stimulation of cocaine memories, to unravel the role of these memories in relapse to cocaine seeking. The resulting research report won the national biology MSc thesis prize, The Darwin. As a side-project, she contributed with her experiments to a recently published manuscript in Neuropsychopharmacology about the role of Brevican in cocaine memories by the team of Michel van den Oever and Sabine Spijker. Esther analysed in Brevican heterozygous mice whether viral over expression of Brevican in the hippocampus and medial prefrontal cortex was able to rescue the increase in remote cocaine place preference memory.