Early- and Late-Light Embryonic Stimulation Modulates Similarly Chicks’ Ability to Filter out Distractors

Abstract

Chicks (Gallus gallus) learned to run from a starting box to a target located at the end of a runway. At test, colourful and bright distractors were placed just outside the starting box. Dark incubated chicks (maintained in darkness from fertilization to hatching) stopped significantly more often, assessing more the left-side distractor than chicks hatched after late (for 42 h during the last three days before hatching) or early (for 42 h after fertilization) exposure to light. The results show that early embryonic light stimulation can modulate this particular behavioural lateralization comparably to the late application of it, though via a different route.

Does Functional Lateralization in Birds Have any Implications for Their Welfare?

“…Light exposure of eggs early in incubation can also influence the development of lateralization manifested after hatching [84] although via a different process than does light-exposure just before hatching since it occurs prior to the establishment of eye to brain connections [85]. Chiandetti et al tested biases in pecking to the left or right side when the birds were presented with an array of grain and they did so by testing chicks hatched from eggs in three groups: one group incubated in the dark, another exposed to light from day 1 to day 3 of incubation, and a third from day 18 until hatching on day 21 [85].…”

Visuospatial attention in the lateralised brain of pigeons – a matter of ontogenetic light experiences

“…Examples from various vertebrate and invertebrate species indicate a profound fitness advantage when brains display a division of labour between the two brain halves 1 – 4 . Lateralised individuals of a species show enhanced sensorimotor and cognitive performances 5 – 9 , are better in conducting two tasks in parallel 10 – 14 , and display efficient interhemispheric cooperation 15 , 16 . Thereby, the hemispheres differ in their modes to analyse and/or to evaluate information that in turn may lead to hemispheric dominances for specific functions.…”

“…Behavioural asymmetries are related to structural and neurophysiological left-right differences in the visual pathways. In chicks and pigeons, the development of visual asymmetries depends on asymmetrical light stimulation during ontogeny 15 , 20 , 21 , 25 , 26 . Owing to the asymmetrical position of the embryo within the egg, the right eye is close to the translucent eggshell and the left eye is occluded by the body.…”

Brain and Behavioral Asymmetry: A Lesson From Fish

“…Chicks with either the left or the right eye covered develop a reversed pattern of asymmetry whereas chicks from eggs incubated in the dark do not exhibit any asymmetry (Rogers, 2008). This neuroanatomical asymmetry is reflected on the behavior as chicks hatched from eggs with their left eye occluded used the right eye (left hemisphere) to distinguish food from pebbles and the left eye (right hemisphere) to monitor a predator; the behavioral asymmetry is reversed in chick hatched from eggs with the right eye occluded (Rogers, 2008(Rogers, , 2014Vallortigara, 2009, 2019;Vallortigara et al, 2011;Chiandetti et al, 2013Chiandetti et al, , 2017. The amount of environmental light received during the development influences lateralization in fish too.…”