L13-VisualSystemII

L13-VisualSystemII - Visual System II Receptive Field...

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Visual System II Receptive Field Organization o On-Center RGC, Off-surround Increase firing rate of action potential of ganglia cell when light is shined on On area of the RGC, especially in the beginning of the period; off area will decrease the firing rate o Off-Center RGC, On-surround Exact opposite responses; disinhibition of cell when light goes away; excitation occurs as a result (off-response rebound effect) o If a dark spot is shined on an on-center RGC would be inhibited because the light is only shining on the surrounding field. Likewise, off-center would be excited. On-center receptive field o LGN On-cell recording Available on Toolkit Receptive Field Structure o When light is shone, the photoreceptor hyperpolarizes (shut off NT release from dark current). Hyperpolarization leads to decreased transmitter release from the photoreceptor onto the bipolar cell (NT=glutamate). Two types of bipolar cells are distinguished by the glutamate receptors (metabotropic: mGLUr (inhibitory); ionotropic: AMPA (excitatory)). mGLUr hooked up to on-center ganglion cells AMPA hooked up to off-center ganglion cells o Therefore, hyperpolarization on off-center and depolarization on on-center o Turning off the light shuts off the Glutamate receptor on the photoreceptor and ultimately decreases the firing rate of the on-center ganglion cell o ****** See Powerpoint ****** Firing rate in On-Center RGCs o Cell A: Completely on dark bar: response rate constant o Cell B: Slightly on light bar (only inhibitory part is located in light
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L13-VisualSystemII - Visual System II Receptive Field...

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