title: Weak signal amplification and detection by higher-order sensory neurons.
abstract: Sensory systems must extract behaviorally relevant information and therefore often exhibit a very high sensitivity. How the nervous system reaches such high sensitivity levels is an outstanding question in neuroscience. Weakly electric fish (Apteronotus leptorhynchus/albifrons) are an excellent model system to address this question because detailed background knowledge is available regarding their behavioral performance and its underlying neuronal substrate. Apteronotus use their electrosense to detect prey objects. Therefore, they must be able to detect electrical signals as low as 1 μV while using a sensory integration time of <200 ms. How these very weak signals are extracted and amplified by the nervous system is not yet understood. We studied the responses of cells in the early sensory processing areas, namely, the electroreceptor afferents (EAs) and pyramidal cells (PCs) of the electrosensory lobe (ELL), the first-order electrosensory processing area. In agreement with previous work we found that EAs cannot encode very weak signals with a spike count code. However, PCs can encode prey mimic signals by their firing rate, revealing a huge signal amplification between EAs and PCs and also suggesting differences in their stimulus encoding properties. Using a simple leaky integrate-and-fire (LIF) model we predict that the target neurons of PCs in the midbrain torus semicircularis (TS) are able to detect very weak signals. In particular, TS neurons could do so by assuming biologically plausible convergence rates as well as very simple decoding strategies such as temporal integration, threshold crossing, and combining the inputs of PCs.
authors: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada; Department of Physics, University of Ottawa, Ottawa, Ontario, Canada; and sarah_nicola.jung@uni-bielefeld.de.
authors: Sarah N
authors: SN
authors: Jung
authors: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada; Department of Physics, University of Ottawa, Ottawa, Ontario, Canada; and Brain and Mind Institute and Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, Canada.
authors: Andre
authors: A
authors: Longtin
authors: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada; Brain and Mind Institute and Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, Canada.
authors: Leonard
authors: L
authors: Maler
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000502:physiology; D023702:Gymnotiformes / Q000502:physiology*; D008564:Membrane Potentials; D008959:Models, Neurological; D010465:Perception; D012677:Sensation; D011984:Sensory Receptor Cells / Q000502:physiology*; D055672:Static Electricity
keywords: sensory processing; weak signal detection; weakly electric fish