For VPL lesions, ibotenic acid (0.5 μl/site) was bilaterally microinjected (third-order neurons of the DC pathway)39. The anesthetized rat (pentobarbital, 50 mg/kg, i.p.) was placed in a stereotaxic frame, and two holes were drilled in the skull to access the following coordinates: anterior, −2.5~−3 mm; lateral, ±2.75~3 mm; deep, 6 mm40. A 26-gauge Hamilton syringe (Reno, NV, USA) filled with either ibotenic acid or saline was infused at a rate of 0.5 μl/min using a microinjection pump (Pump 22, Harvard Apparatus, USA). The syringe was left in place for at least 5 min to facilitate diffusion after injection. For electrolytic lesion of bilateral LHb, tungsten electrodes insulated except at 0.5 mm tip were inserted in the following coordinates: anterior, −3.5 mm; lateral, ±0.7 mm, deep −4.9 mm. Lesions were made by passing ± 0.35 mA of DC current for 8 sec alternately. The rats were allowed to recover for at least 7 days after surgery.