Exposure to a theta-burst patterned magnetic field impairs memory acquisition and consolidation for contextual but not discrete conditioned fear in rats.
Preceding or immediately following fear-conditioning rats were exposed for 30 min to either a sham field, one of two symmetrical (sine-wave 7, 20 Hz) magnetic fields or to one of two complex magnetic fields whose waveforms were modeled after salient electrophysiological patterns within either the hippocampal formation (theta-burst) or the amygdaloid complex (burst-firing). The magnetic fields were presented in successive 2s intervals through each of the three spatial planes and then simultaneously within all three planes. Field strengths ranged between 0.5 and 1 microTesla. Only the group exposed after the conditioning to the theta-burst (hippocampal) magnetic fields displayed evidence of forgetting, as inferred by their marked attenuation of freezing behavior, during contextual extinction 24h later. This powerful treatment explained 75% of the variance in the extinction scores. Behavioral responses to the discrete conditioned stimulus were not affected. These findings are consistent with the involvement of the hippocampus in learned fear to contextual stimuli but not to discrete auditory stimuli and suggest that physiologically relevant stimuli may be delivered to the brain by weak, complex magnetic fields whose intensities are ubiquitous within modern environments.
McKay
B E
BE
Behavioral Neuroscience Laboratory, Laurentian University Sudbury, Ontario, P3E 2C6, Canada.
Persinger
M A
MA
Koren
S A
SA
D000161:Acoustic Stimulation; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D003213:Conditioning, Psychological / Q000502:physiology; D004574:Electromagnetic Fields / Q000009:adverse effects*; D055590:Electromagnetic Phenomena / Q000295:instrumentation / Q000379:methods; D005108:Extinction, Psychological / Q000502:physiology; D005239:Fear / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology*; D008569:Memory Disorders / Q000209:etiology* / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar