Chick learning was compared in two experimental groups: isolated and paired chicks (these two groups are known to experience different stress levels). 295 chicks were divided into the following groups: 1) magnetic field exposure - isolated chicks, 2) magnetic field exposure - paired chicks, 3) sham exposure - isolated chicks, and 4) sham exposure - paired chicks. Within each group, chicks were randomly and further divided into one of three testing time sets of 10, 30, or 120 min (according to different stages of memory formation following hatching).
Exposure duration: 60 min/day on embyonic days 12 - 18
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The data demonstrated that magnetic field exposure in ovo during late incubation impaired young chick's memory in the passive avoidance test, depending on the stress level and the time of memory consolidation. Memory was intact at 10 minutes in both isolated and paired chicks with or without magnetic field exposure. However, magnetic field exposure did influence the performance of isolated chicks at 30 and 120 minutes, but not the performance of paired chicks.
With the exception of increased hatch weight in chicks exposed to magnetic field, there were no other obvious differences in hatching success, hatching time, and abnormalities.
The data suggest a potential disruption of memory formation following in ovo exposure to magnetic field, but this effect was only evident in the more stressed, isolated chicks.