Environmental effects on fish neural plasticity and cognition

Abstract

Most fishes experiencing challenging environments are able to adjust and adapt their physiology and behaviour to help them cope more effectively. Much of this flexibility is supported and influenced by cognition and neural plasticity. The understanding of fish cognition and the role played by different regions of the brain has improved significantly in recent years. Techniques such as lesioning, tract tracing and quantifying changes in gene expression help in mapping specialized brain areas. It is now recognized that the fish brain remains plastic throughout a fish's life and that it continues to be sensitive to environmental challenges. The early development of fish brains is shaped by experiences with the environment and this can promote positive and negative effects on both neural plasticity and cognitive ability. This review focuses on what is known about the interactions between the environment, the telencephalon and cognition. Examples are used from a diverse array of fish species, but there could be a lot to be gained by focusing research on neural plasticity and cognition in fishes for which there is already a wealth of knowledge relating to their physiology, behaviour and natural history, e.g. the Salmonidae.

How do individuals cope with stress? Behavioural, physiological and neuronal differences between proactive and reactive coping styles in fish

“…Mechanisms that aid an organism to cope with environmental changes regulate individual differences in motivation, which is only possible through differences in the regulation of the neural network and processing of environmental input (Ebbesson and Braithwaite, 2012;Zupanc and Lamprecht, 2000). It is now generally accepted that a complex structural and functional activation of neural networks (in particular, forebrain cell populations), molecular processes and neurotransmitter systems (e.g.…”

Predators inhibit brain cell proliferation in natural populations of electric fish, Brachyhypopomus occidentalis

“…Several authors have proposed that regulating adult neurogenesis may enable animals to alter their behaviour in response to novel environments [22,47,48]. In some animals, brain cell proliferation and subsequent neurogenesis is causally linked to increased cognitive function (memory and learning) and behavioural performance [49].…”

“…We focused our study on the forebrain because it contains regions that probably help coordinate the behavioural response to predators [22,23]. In teleost fish, the dorsolateral telencephalon (DL) participates in spatial orientation and learning, and it is probably homologous to the mammalian hippocampus [23,24], a cell proliferation zone in mammals that is influenced by predator stimuli [9,25].…”

Aluminum exposure impacts brain plasticity and behavior in Atlantic salmon (Salmo salar)

“…Together, these data suggest that exposure to Al toxicity in acidified water has a negative impact on both the brain and learning behavior in salmon. Such an effect is likely to have a negative influence on the ability of the fish to cope with the transition from freshwater to the marine environment, a time when the fish need to perform critical behaviors such as predator avoidance, social interactions and navigation Ebbesson and Braithwaite, 2012). Furthermore, it is possible that the reduced forebrain neural plasticity and cognitive deficit at the critical smolt stage also affect imprinting, by altering the olfactory-telencephalic plasticity associated with smoltification (Ebbesson et al, 1996a;Ebbesson et al, 2003;Folgueira et al, 2004).…”

“…Memories of the natal stream formed during imprinting are later used to return as adults (Hasler and Scholz, 1983;Yamamoto et al, 2010), and thus impaired imprinting could have a profound impact on return success. Such behavioral processes are likely to involve the area of the brain involved in spatial learning and memory, namely the dorsolateral area of the telencephalon (Ebbesson and Braithwaite, 2012).…”