Light-incubation effects on lateralisation of single unit responses in the visual Wulst of domestic chicks

Giacomo Costalunga,Uwe Mayer,Giorgio Vallortigara,Dmitry Kobylkov,Orsola Rosa-Salva

doi:10.1007/s00429-021-02259-y

Giacomo Costalunga, Uwe Mayer + Show 3 more

Open Access

https://doi.org/10.1007/s00429-021-02259-y

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Abstract

Since the ground-breaking discovery that in-egg light exposure triggers the emergence of visual lateralisation, domestic chicks became a crucial model for research on the interaction of environmental and genetic influences for brain development. In domestic chick embryos, light exposure induces neuroanatomical asymmetries in the strength of visual projections from the thalamus to the visual Wulst. Consequently, the right visual Wulst receives more bilateral information from the two eyes than the left one. How this impacts visual Wulst’s physiology is still unknown. This paper investigates the visual response properties of neurons in the left and right Wulst of dark- and light-incubated chicks, studying the effect of light incubation on bilaterally responsive cells that integrate information from both eyes. We recorded from a large number of visually responsive units, providing the first direct evidence of lateralisation in the neural response properties of units of the visual Wulst. While we confirm that some forms of lateralisation are induced by embryonic light exposure, we found also many cases of light-independent asymmetries. Moreover, we found a strong effect of in-egg light exposure on the general development of the functional properties of units in the two hemispheres. This indicates that the effect of embryonic stimulation goes beyond its contribution to the emergence of some forms of lateralisation, with influences on the maturation of visual units in both hemispheres.

Highlights

Contrary to what was once believed, functional and structural differences between cerebral hemispheres are widespread in the animal kingdom (Vallortigara and Rogers 2005; Frasnelli et al 2012; Rogers et al 2013)
2006), the hippocampal, anterior, tectal and posterior commissures still allow exchange of information between the two hemispheres. This is an additional layer of complexity that needs to be considered in the interpretation of visual lateralization effects in avian species (e.g., Rogers and Sink 1988; Rogers and Deng 1999 showed that lateralization affects structures involved in the processing of bilateral information, see below)
Domestic chicks emerged as a relevant model, after the ground-breaking finding that exposure of chick eggs to light during a specific sensitive period causes the development of visual lateralisation (Rogers 1982)

Summary

Introduction

Contrary to what was once believed, functional and structural differences between cerebral hemispheres (i.e., brain lateralisation) are widespread in the animal kingdom (Vallortigara and Rogers 2005; Frasnelli et al 2012; Rogers et al 2013). 2006), the hippocampal, anterior, tectal and posterior commissures still allow exchange of information between the two hemispheres This is an additional layer of complexity that needs to be considered in the interpretation of visual lateralization effects in avian species (e.g., Rogers and Sink 1988; Rogers and Deng 1999 showed that lateralization affects structures involved in the processing of bilateral information, see below). Following research revealed that light exposure during the development evokes several forms of behavioural and neuroanatomical lateralisation, including asymmetries of the supraoptic decussation, a recrossing tract bringing to each hemisphere projections from its ipsilateral eye (Rogers and Sink 1988; Rogers and Deng 1999). These asymmetries are present only in chicks hatched from light-incubated eggs, but not in dark-incubated chicks

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