Interaction between sex-steroids, electric signaling, and electrosensory processing in weakly electric fish

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Sense organs provide a constant stream of input to the brain, and it is one of the main tasks of the brain to filter the incoming information and extract those aspects that are important for making behavioural decisions. The long-term goal of my research is to understand the mechanisms used by the brain to extract behaviourally relevant information from this stream of input. A characteristic feature of sensory processing in the brains of vertebrates is that the input arriving from a sense organ is split into multiple parallel channels that are specialized to process different aspects of the incoming information. As these channels have to work under a variety of different environmental and behavioural conditions (e.g., dim light vs. bright light, searching for food vs. searching for a mate), their response properties are constantly adjusted to these changing conditions. Some of these adjustment mechanisms are built into the individual nerve cells of these channels; some are a consequence of how groups of nerve cells in these channels are interconnected; and some are mediated by changes in the levels of circulating hormones or of neuromodulatory substances that act locally in some channels, but not others. In addition, these three levels of adjustment mechanisms interact with each other. Over the next five years, I will focus on the role of steroid hormones in adjusting how a set of parallel processing channels responds to sensory input. Across vertebrates, steroid hormones are known to be central to the control of reproductive behaviour, including the production and perception of advertisement signals and aggressive signals, but the mechanisms by which they affect sensory processing are still poorly understood. I will address these mechanisms using the electrosensory system of weakly electric fish as a model. Weakly electric fish produce electric fields in the water surrounding their body and sense how their electric field is perturbed by the presence of nearby objects or by the electric fields of other electric fish. They can thus use their electric fields for object (prey) detection as well as communication. In the same way as other sensory systems, the electrosensory system splits the incoming information in multiple parallel channels, each of which is specialized for processing different stimulus aspects. And each of these channels can adjust its processing properties to changing environmental or behavioural conditions. I will study specifically how steroid hormones control information flow in these parallel channels. The electrosensory system is well suited to address this problem because, first, behaviourally relevant stimuli (electric fields of varying properties) can be easily quantified and recreated in behavioural and neurophysiological experiments; second, we can build on a wealth of knowledge on the neuroanatomy, neurophysiological response properties, and the role of various neurotransmitters and neuromodulators; and third, the multiple parallel channels of information processing offer a fantastic and experimentally accessible substrate for exploring how sensory response properties are controlled.