Pavlovian Acquisition.

Pavlovian training utilized a food-predictive conditioned stimulus (CS+) as well as a conditioned stimulus predictive of no food delivery (CS−). A CS− was included to uncover whether any alterations in behavior were specific to reward-predictive cues, or rather to environmental stimuli in general. Auditory tones at the frequency of 8 kHz or 15 kHz, discriminable for mice (De Hoz & Nelken, 2014), were used as conditioned stimuli and were presented for a duration of 120 sec. One food pellet (Bio-Serve formula {"type":"entrez-nucleotide","attrs":{"text":"F05684","term_id":"669500","term_text":"F05684"}}F05684) was delivered on average every 30 sec throughout presentation of the CS+, whereas no food was delivered during the CS−. Between each CS presentation was an intertrial interval (ITI) when no tones were played and no food was delivered. The ITI duration varied pseudorandomly from 60 sec to 180 sec, with an average duration of 120 sec. Pavlovian training sessions occurred daily for a total of 7 days, with each session including 10 CS+ and 10 CS− tones presented in pseudorandom order. Mouse entries into the food magazine were recorded via infrared beam breaks.