title: Limitations of Neural Map Topography for Decoding Spatial Information.
abstract: Topographic maps are common throughout the nervous system, yet their functional role is still unclear. In particular, whether they are necessary for decoding sensory stimuli is unknown. Here we examined this question by recording population activity at the cellular level from the larval zebrafish tectum in response to visual stimuli at three closely spaced locations in the visual field. Due to map imprecision, nearby stimulus locations produced intermingled tectal responses, and decoding based on map topography yielded an accuracy of only 64%. In contrast, maximum likelihood decoding of stimulus location based on the statistics of the evoked activity, while ignoring any information about the locations of neurons in the map, yielded an accuracy close to 100%. A simple computational model of the zebrafish visual system reproduced these results. Although topography is a useful initial decoding strategy, we suggest it may be replaced by better methods following visual experience.
  
  
  
  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, here we show 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.
authors.affiliation: Queensland Brain Institute.
authors.forename: Lilach
authors.identifier: 0000-0003-1957-8702
authors.initials: L
authors.lastname: Avitan
authors.affiliation: Queensland Brain Institute.
authors.forename: Zac
authors.identifier: 0000-0002-2515-7296
authors.initials: Z
authors.lastname: Pujic
authors.affiliation: Queensland Brain Institute, School of Mathematics and Physics, and.
authors.forename: Nicholas J
authors.identifier: 0000-0003-1657-4378
authors.initials: NJ
authors.lastname: Hughes
authors.affiliation: School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia.
authors.forename: Ethan K
authors.identifier: 0000-0003-3150-9216
authors.initials: EK
authors.lastname: Scott
authors.affiliation: Queensland Brain Institute, School of Mathematics and Physics, and g.goodhill@uq.edu.au.
authors.forename: Geoffrey J
authors.identifier: 0000-0001-9789-9355
authors.initials: GJ
authors.lastname: Goodhill
mesh_terms: D000818:Animals; D001931:Brain Mapping / Q000379:methods* / Q000592:standards; D005074:Evoked Potentials, Visual; D013028:Space Perception; D013477:Superior Colliculi / Q000502:physiology*; D014796:Visual Perception; D056969:Voltage-Sensitive Dye Imaging / Q000379:methods* / Q000592:standards; D015027:Zebrafish
keywords: computational model; sensory decoding; topographic map; zebrafish