Effects of social interaction on monocular/unihemispheric sleep in male and female domestic chicks

Area of Science:

• Neuroscience
• Ethology
• Animal Behavior

Background:

• Unihemispheric sleep, common in birds, allows one hemisphere to rest while the other remains alert.
• Avian brain lateralization plays a role in cognitive functions and sleep patterns.
• Social housing can influence behavioral and physiological responses in developing animals.

Purpose of the Study:

• To investigate the effects of social rearing and isolation on unihemispheric sleep patterns in male and female domestic chicks.
• To explore sex-specific differences in sleep lateralization in response to social environment.
• To correlate eye-closure biases with potential hemispheric activation during wakefulness.

Main Methods:

• Domestic chicks were reared in pairs for the first week post-hatching.
• In the second week, chicks were either housed with a conspecific (Conspec-chicks) or isolated (No-Conspec-chicks).
• Monocular/unihemispheric sleep was assessed by observing eye closure in relation to sex and social condition.

Main Results:

• In the first week, female chicks showed a bias for right unihemispheric sleep, while males did not exhibit a bias.
• In the second week, both sexes in the Conspec-chicks group preferred left unihemispheric sleep.
• Female No-Conspec-chicks showed no bias, whereas male No-Conspec-chicks exhibited a bias for right unihemispheric sleep.

Conclusions:

• Social housing significantly impacts unihemispheric sleep lateralization in domestic chicks, with sex-specific effects.
• The presence or absence of a social partner influences the direction of sleep lateralization.
• These findings suggest a link between social environment, brain lateralization, and vigilance strategies during sleep in birds.