mGluR5 KO mice exhibit elevated breakpoints relative to WT littermates in touchscreen PR4 schedule. a Number of trials completed in FR5-UC. b Target touches in FR5-UC (Total number of responses at the target screen location). c Blank touches in FR5-UC (Total number of responses at the 4 non-target screen locations). d Reward collection latency during FR5-UC (Time between completion of the final target touch of a trial and entry to the reward magazine for reward collection). e-f Rate of IR beam breaks in the front and rear zones of the touchscreen apparatus during FR5-UC. g Breakpoint in PR4 (Number of target responses emitted by an animal in the last successfully completed trial, before session termination or 60 min time-out). h Target touches in PR4. i Blank touches in PR4. j Reward collection latency during PR4. k-l Rate of IR beam breaks in the front and rear zones of the touchscreen apparatus during PR4. m Percentage of maintained restricted body weight relative to the baseline free-feeding weight. WT group n = 10 and mGluR5 KO group n = 10, unpaired t test; ***p < 0.001. All data are presented as means ± s.e.m.