title: Hippocampal theta activity related to elicitation and inhibition of approach locomotion.
abstract: This study determined if the hippocampal theta rhythm showed phase relationships or changes in amplitude and frequency with the onset of stimuli and locomotion in a task in which auditory cues initiated and suppressed approach locomotion. Rats with electrodes in the dorsal hippocampus lapped at a milk dipper and were presented a tone which predicted the delivery of a food pellet. In some trials the pellet cue tone was negated by 60-Hz clicks beginning 0.3 s after onset, and no pellet was delivered. A video capture system (20-ms sampling) synchronized to the hippocampal recording system (10-ms sampling) was used to determine the onset of locomotor approach to the pellet area. The findings failed to support proposals that phase-related mechanisms play a role in encoding and retrieval of movement-related information. Neither the pellet cue nor the negating cue reset the theta rhythm, and they did not produce differential evoked potentials. During milk lapping, theta amplitude increased in the 1/2s prior to all pellet cues regardless of their locomotor effect. Frequency also rose but only when a non-negated pellet elicited short-latency locomotion. During locomotor execution, theta peak amplitude peaked earlier than theta frequency by approximately one period. In general during performance of this task, increasing theta amplitude reflected a general preparation to process the cue and increasing theta frequency reflected the readiness to respond to the cue with locomotion.
authors.affiliation: Neuroscience and Behavior Program, Wesleyan University, Judd Hall, Middletown, CT 06459-0408, USA. hsinnamon@wesleyan.edu
authors.forename: Harry M
authors.initials: HM
authors.lastname: Sinnamon
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D001522:Behavior, Animal; D003213:Conditioning, Psychological / Q000502:physiology*; D003463:Cues; D004192:Discrimination, Psychological; D006624:Hippocampus / Q000502:physiology*; D007266:Inhibition, Psychological; D008124:Locomotion / Q000502:physiology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D013826:Theta Rhythm; D013997:Time Factors; D014741:Video Recording / Q000379:methods