Time-of-day variation in the sensitization of the acoustic response in pigeons

Abstract

The present study investigated whether the sensitization to acoustic stimuli in pigeons oscillates as a function of the time of day. Both the training and testing were conducted in a single session and the procedure was repeated every 4 h with different experimental and control groups of pigeons. A skeleton photoperiod (two 15-min light pulses to indicate the beginning and the end of the day) was used to prevent the masking effects of the light-dark cycle. The procedure consisted of a baseline exposure to five tone pulses, sensitization training with two electric shocks (5 min interval) starting 5 min later and testing using a series of 40 tone pulses, starting 10 min later. The control birds were exposed to the chamber only. The magnitude of response was measured by an accelerometer located under the floor of the experimental chamber. Sensitization was analyzed by comparing the amplitude of the response during testing to the baseline level. The amplitude of response of the experimental birds varied as a function of the time of day, with significantly greater amplitude during the subjective night (P 5 0.05). Control data showed no daily variation, however, suggesting that the rhythm in sensitization was due to the circadian modulation of a learning process.

Welfare-improving enrichments greatly reduce hens’ startle responses, despite little change in judgment bias

“…Such effects may reflect how much readiness for physical action each state induces 39 . Exploring how known affective states influence startle is therefore important if this response is ever to become useful in welfare assessment, and especially so for non-mammals: birds have startle reflexes homologous with those of mammals 40,41 , but whether these reflexes are subject to similar affective modulation had not been investigated. Assessing the impact of affective state changes on the avian startle reflex, using laying hens as a model, was therefore our second aim.…”

Daily cycling of nitric oxide synthase (NOS) in the hippocampus of pigeons (C. livia)

“…So, the analysis of molecular cycling in the hippocampus of pigeons can add important points to the set of many studies that described a coordinated set of circadian biochemichal, physiological and behavioral rhythms in a wide array of vertebrates, including birds [ 20 - 23 ]. Particularly, pigeons have been much studied in laboratory research on circadian rhythms of feeding, thermal physiology, hormonal variation and metabolism [ 24 - 27 ] as well as on time-of-day variation of behavior and learning [ 28 - 31 ]. Therefore, the present study was performed to elucidate the 24 h cycling of NOS in the hippocampus of pigeons.…”