Neural substrates involved in the processing of cognitive information in fish (Pseudotropheus sp)

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Behavioral studies over the last century have shown that fish possess cognitive abilities rivaling those of mammals and birds. Unfortunately though, comparably few studies have successfully identified the neural substrates involved in the processing of cognitive information in fish. Consequentially, some information is available on a very limited number of topics, i.e. classical or instrumental conditioning, avoidance learning and spatial cognition while the brain areas important for many other cognitive abilities remain completely unknown. Such abilities include (but are certainly not limited to) all aspects of social learning (e.g. individual recognition, information transfer or Machiavellian intelligence), discrimination learning (whereby stimuli can vary from 2D to 3D, stationary to moving objects, etc.), categorization abilities and memory storage. I propose that not only the telencephalon but also specific regions within the diencephalon hold key functions for the processing of cognitive information in fish. Brains of (social) species living in complex habitats, such as coral reef fish or cichlids feature several brain areas or nuclei (e.g. the nucleus glomerulosus) not found in more basal teleost fish such as the osteoglossomorpha (e.g. African weakly electric fish), elopomorpha (e.g. eels) and clupeomorpha (e.g. herrings). The development of such derived structures found in the telencephalon or diencephalon of modern teleosts may quite likely be linked to more complex social hierarchies and complex habitats and thereby to more elaborate cognitive abilities. This proposal aims to narrow the gap in the current literature regarding detailed structure-function relationships and the growing need for the identification of brain structures involved in the processing of cognitive information in fishes, located both within and outside of the telencephalon (a prime candidate for cognitive information processing and also the best studied so far). Selective lesion experiments used in combination with behavioral observations of spontaneous behavior (experiment 1A&B) as well as specifically designed training assays (experiment 2) are proposed to reveal the significance of specific brain regions for aspects of individual recognition, visual discrimination, time-place learning and spatial orientation. IEG studies (experiment 3) will shed further light onto specific brain regions involved in the process of visual discrimination learning and specifically recognition of individuals (social cognition). The six target nuclei or areas in this study include three areas from the telencephalon; these are (1) the dorsal zone of the pallium, (2) the lateral zone of the pallium and (3) the medial zone of the pallium. Additionally, three areas are targeted in the diencephalon, which so far have never been investigated in a cognitive context. These are (4) the nucleus glomerulosus, (5) the inferior lobes and (6) the dorsal/ventral thalamus.