The local brain temperature is monitored as an indicator of functional neural activation21. Temperature changes in the LHb following peripheral stimulation were monitored as described previously43 with slight modifications. In brief, under pentobarbital-induced anesthesia (50 mg/kg, i.p.), an access hole was drilled through the skull over the habenula (coordinates: anterior, −3.5 mm; lateral, ±0.7 mm; deep, −4.9 mm) or the control site (coordinates: anterior, −3.5 mm; lateral, ±2.0 mm; deep, −4.9 mm), and a thermocouple needle microprobe (NJ-07013, World Precision Instruments, USA) was slowly lowered to the desired target depth. The thermocouple probe was connected to a BAT-12 digital thermometer (Physitemp, USA) and a data acquisition system (Powerlab, ADinstrument, Australia). The LHb temperature was measured while body temperature was maintained at approximately 36.5 °C with a heating pad.