Rat ultrasonic vocalizations demonstrate that the motivation to contextually reinstate cocaine-seeking behavior does not necessarily involve a hedonic response.
Barker DJ, Bercovicz D, Servilio LC, Simmons SJ, Ma S, Root DH, Pawlak AP, West MO. Rat ultrasonic vocalizations demonstrate that the motivation to contextually reinstate cocaine-seeking behavior does not necessarily involve a hedonic response. Addict Biol. 2014 Sep; 19(5):781-90.