This study (Q26) is one of a series of studies performed in the Szechtman lab at McMaster University and deposited in the FRDR public repository as a collection under the name "A Digital Library of Behavioural Performance in Standardized Conditions - Szechtman Lab Collection". This collection as a whole constitutes a big dataset containing raw data objects of video, track, and path plot records of rats exploring for 55 minutes a large testing environment in a standardized paradigm during chronic treatment with psychostimulant drugs; for details of this big dataset see, https://www.frdr-dfdr.ca/repo/collection/szechtmanlab. The historical context for study Q26 was Project_01 entitled: "Probing the neural circuit mediating sensitization and compulsive checking". This project had two separate studies, designated as Q26NAc1 and Q26NAc2. The title of study Q26NAc1 was "Probing the neural circuit mediating sensitization and compulsive checking: role of the nucleus accumbens core (NAc) on development" and the title of study Q26NAc2 was "Probing the neural circuit mediating sensitization and compulsive checking: role of the nucleus accumbens core (NAc) on expression". Study Q26NAc1 had two experiments, the first one with the title "Effect of an NMDA lesion of the NAc on the development of sensitization and compulsive checking (batch 1)" and the second one, which was a repeat of the first experiment, had the title "Effect of an NMDA lesion of the NAc on the development of sensitization and compulsive checking (batch 2)". The title of experiment in Q26NAc2 was "Effect of an NMDA lesion of the NAc on the expression of sensitization and compulsive checking". For the development study (Q26NAc1), rats received a lesion targeted at the NAc and the effect of this lesion on the induction of compulsive checking in our standard paradigm was measured. For the expression study (Q26NAc2), rats received our standard treatment to induce compulsive checking and then received a lesion targeted at the NAc and the effect of this lesion on the expression of compulsive checking was measured. This dataset has the same Design and Procedure as dataset deposits for StudyID Q25 doi:10.20383/102.0439 and StudyID Q28 doi:10.20383/102.0436