Light exposure of the embryo and development of behavioural lateralisationin chicks, I: olfactory responses

Chicks exposed to light during late foetal life experience stimulation of t he right eye only and, in consequence, develop asymmetries of the crossed v isual projections from thalamus to forebrain and differences in performance of some visual tasks when using the right or left eye. The present study c ompared dark- and light-incubated chicks in a test of olfaction in which cl ove oil odour was presented together with a coloured bead. When the chicks were tested with a blue bead and using the right nostril (left nostril occl uded by wax), head shaking and pecking were elevated, compared to pretest r esponses to an unscented, white bead. No significant elevation of head shak ing occurred in chicks tested with the blue bead and using the left nostril , although pecking increased, which indicates that these chicks attended to the visual parameters of the bead but not the odour. It appears that, when the left nostril is used, attention to an attractive visual stimulus suppr esses responses to olfactory input to the left hemisphere. When the clove o il odour was presented together with a less attractive, red bead, no signif icant lateralisation emerged. Light or dark experience prior to hatching ha d no effect on the lateralised performance of the blue-bead lest. (C) 1998 Elsevier Science B.V. All rights reserved.