Active exploration of an environment drives the activation of the hippocampus–amygdala complex of domestic chicks

Abstract

In birds, like in mammals, the hippocampus critically mediates spatial navigation through the formation of a spatial map. This study investigates the impact of active exploration of an environment on the hippocampus of young domestic chicks. Chicks that were free to actively explore the environment exhibited a significantly higher neural activation (measured by c-Fos expression), compared to those that passively observed the same environment from a restricted area. The difference was limited to the anterior and the dorsolateral parts of the intermediate hippocampus. Furthermore, the nucleus taeniae of the amygdala showed a higher c-Fos expression in the active exploration group than the passive observation group. In both brain regions, brain activation correlated with the number of locations that chicks visited during the test. This suggest that the increase of c-Fos expression in the hippocampus is related to increased firing rates of spatially coding neurons. Furthermore, our study indicates a functional linkage of the hippocampus and nucleus taeniae of the amygdala in processing spatial information. Overall, with the present study, we confirm that, in birds like in mammals, hippocampus and amygdala functions are linked and likely related to spatial representations.

Spatial cognition and the avian hippocampus: Research in domestic chicks

“…Even fewer may exist in galliformes, such as quails and chickens, which retained more ancestral traits compared to neoaves (Prum et al, 2015). This hypothesis is supported by our most recent paper (Morandi-Raikova and Mayer, 2022). In our study, chicks that could actively explore an environment had a higher c-Fos expression in the anterior hippocampus and in the dorsolateral parts of the intermediate hippocampus, compared to those that passively observed the same environment from a restricted area (Figure 2J).…”

“…In summary electrophysiological confirmation studies with domestic chicks are urgently needed at this point. Our study (Morandi-Raikova and Mayer, 2022) together with studies in other birds (Agarwal et al, 2021;Payne et al, 2021) indicate that future studies in chicks should focus in on the anterior hippocampus, which increased the density of c-Fos immunoreactive cells after active exploration of a novel environment. Moreover, it is important to investigate if also other spatially coding cells (e.g., head direction cells, border cells, or grid cells) are existent in chicks' hippocampi.…”

Environmental change or choice during early rearing improves behavioural adaptability in laying hen chicks

“…We hypothesised that, when compared to a treatment representing standard rearing conditions; (1) a higher level of environmental change, achieved by repeated changes of litter and perch types, would result in mild stress during rearing but provide coping experience, thereby reducing fearfulness and leading to greater adaptability when challenged with novelty 11 , 12 ; (2) a higher level of environmental choice, achieved by simultaneously providing a variety of litter and perch types, would help to fulfil motivation for behavioural activities such as foraging and dustbathing leading to greater comfort and agency, along with enhancement of spatial skills 17 , 37 including practicing the different bodily actions needed to land and balance on the different perch types 15 , 31 ; while (3) higher levels of both environmental change and choice would enhance both adaptability and agency, and lead to the most advantageous outcomes in terms of both welfare during rearing and adaptability in response to novelty.…”

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“…A more complex rearing environment for farm animals such as laying hens (Gallus gallus domesticus) could encourage the gathering of information and promote the development of spatial navigation skills (16)(17)(18) as well as spatial learning and problem solving in general (19)(20)(21). In other words, rearing in a complex environment could increase the likelihood that laying hens are sufficiently behaviorally flexible to make the most of the opportunities offered to them later in life, thereby contributing to long-term positive welfare.…”