Computational, Systems and Developmental Neuroscience

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Neural coding in zebrafish tectum

All your thoughts are just patterns of electrical activity in your brain. What is the `neural code' by which these patterns represent information, and how does it develop? We are investigating these questions using the zebrafish model system. Zebrafish larvae are transparent, therefore we can use genetically-encoded calcium indicators to optically record the activity of many neurons simultaneously, both spontaneously and while they view simple visual stimuli. We then analyse these activity patterns using mathematical tools such as graph theory and information theory.

  • The development of spontaneous activity in the zebrafish brain. The optic tectum in the brain of the larval zebrafish is highly active even without visual input. In a recent paper in Current Biology we looked at this activity every day from 4-9 dpf (days post-fertilization) to examine how this activity develops. Using tools from graph theory we showed how the functional connectivity of the tectum changes over this time. By manipulations like raising fish in the dark we also showed that these changes were dependent on visual input during development.
  • Limitations of neural map topography for decoding spatial information. A very common feature of brain wiring is that neighboring points on a sensory surface (eg, the retina) are connected to neighboring points in the brain. It is often assumed that this “topography” of wiring is essential for decoding sensory stimuli. However, in a recent paper in the Journal of Neuroscience we showed in the developing zebrafish that topographic decoding performs very poorly compared with methods that do not rely on topography. This suggests that, although wiring topography could provide a starting point for decoding at a very early stage in development, it may be replaced by more accurate methods as the animal gains experience of the world.

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