110 Receptive fields 2008

110 Receptive fields 2008 - Lecture 3: Receptive fields...

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Lecture 3: Receptive fields Topics to be discussed: The structure of receptive fields Receptive fields and the functional organization of the retina Relationship between receptive fields and visual perception Receptive fields and the organization of the retina’s output The structure of a receptive field : Some history and some definitions: The study of neuronal responses to light stimuli is performed by inserting a fine microelectrode to the retina of an anesthetized animal to record action potentials (also known as ‘spikes’; and many spikes over time are known as ‘spike-trains’). Using extracellular recording the investigator notes the number of spontaneous action potentials (i.e., evoked without stimulation) vs. the number of action potentials evoked by different types of visual stimuli. By using several types of different visual stimuli, the researcher can search for the preferred stimulus of a neuron. In this context, a preferred stimulus is one that evokes the strongest excitation in terms of the number of action potentials per unit time. The number of action potentials per unit time (typically 1 second) is known as the firing-rate of a neuron . Surprisingly, just shining diffuse (i.e., light stimulation over the entire retina) light stimuli on the retina (or on a screen facing the animal) does not alter the recorded neuron's firing rate. The breakthrough came in 1953 when Kuffler found that one has to use small , circular light stimuli rather than diffuse light. Next, Kuffler found that for every ganglion cell in the retina there is only a small, circular area (in the retina, or equivalently, on the screen in front of the animal where the stimulus is presented) where a stimulus can modulate (change) the firing-rate of a neuron’s spike train. The neuron responds to the stimulus only within this area. This area is known as the
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This note was uploaded on 04/14/2010 for the course BIO SCI BIO N110 taught by Professor Leon,chance&parker during the Spring '09 term at UC Irvine.

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110 Receptive fields 2008 - Lecture 3: Receptive fields...

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