Reward and aversive stimuli produce similar nonphotic phase shifts.
Circadian rhythms in rodents respond to arousing, nonphotic stimuli that contribute to daily patterns of entrainment. To examine whether the motivational significance of a stimulus is important for eliciting nonphotic circadian phase shirts in Syrian hamsters (Mesocricetus auratus), the authors compared responses to a highly rewarding stimulus (lateral hypothalamic brain stimulation reward [BSR]) and a highly aversive stimulus (footshock). Animals were housed on a 14:10-hr light-dark cycle until test day, when they were given a 1-hr BSR session (trained animals) or a 1-mA electric footshock at 1 of 8 circadian times, and were maintained in constant dark thereafter. Both BSR pulses and footshock produced nonphotic phase response curves. These results support the hypothesis that arousal resulting from the motivational significance of a stimulus is a major factor in nonphotic phase shifts.
Cain
Sean W
SW
Department of Psychology, University of Toronto, Toronto, ON, Canada. swcain@hotmail.com
Verwey
Michael
M
Hood
Suzanne
S
Leknickas
Povilas
P
Karatsoreos
Ilia
I
Yeomans
John S
JS
Ralph
Martin R
MR
D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D003624:Darkness; D004558:Electric Stimulation / Q000379:methods; D004597:Electroshock / Q000379:methods; D008027:Light; D008297:Male; D008647:Mesocricetus; D012201:Reward