ABC seminar
Petri Ala-Laurila: Vision at its ultimate limits: optimal strategies of neural computation
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Detection of the weakest stimuli is a fundamental challenge for sensory systems. Sensory receptors come close to the fundamental limits imposed by physics: rod photoreceptors encode single photons, pheromone receptors can encode single odorant molecules and auditory hair cells can encode subatomic displacements. However, sensory receptors and downstream neural circuits generate noise. How can weak input signals be retained from being buried under noise? The visual system offers an outstanding possibility to investigate the neural circuit function underlying the detection of the weakest stimuli. At visual threshold the signals traverse the mammalian retina via the so-called rod-bipolar pathway. Recent work by others (Field et al., 2002) and us (Ala-Laurila & Rieke, 2014) has shown that nonlinear dynamics of neural computation and noise filtering are key determinants of high- fidelity signal processing in the retina at visual threshold. My laboratory has taken an integrative approach relying on electrophysiology, molecular techniques, mathematical modeling, and behavioral experiments to investigate retinal signal processing at its sensitivity limits. Our recent work shows that the retina provides the brain with two fundamentally different readouts of the rod’s single-photon responses: a low noise and thresholded readout (provided by On ganglion cells) and a noisy but linear readout (provided by Off ganglion cells). This result resolves a long-standing debate about the neural substrates for absolute visual sensitivity and forms the basis for addressing outstanding questions on retinal signal processing at its ultimate limits. I will provide examples of these questions and our approach to address them in my talk.
Selected recent publications
Ala-Laurila, P. & Rieke, F (2014). Coincidence Detection of Single-Photon Responses in the Inner Retina at the Sensitivity Limit of Vision. Current Biology 24, 2888-2898.
Ala-Laurila, P., Greschner, M., Chichilnisky & Rieke, F (2011). Cone contributions to noise and correlations in the retinal output. Nature Neuroscience 14, 1309-1316.
Luo, D. G., Yue, W.W., Ala-Laurila, P., & Yau, K.W. (2011). Activation of visual pigments by light and heat. Science 332, 1307–1312.