TY - JOUR T1 - Different Mechanisms Generate Maintained Activity in ON and OFF Retinal Ganglion Cells JF - The Journal of Neuroscience JO - J. Neurosci. SP - 5994 LP - 6005 DO - 10.1523/JNEUROSCI.0130-07.2007 VL - 27 IS - 22 AU - David J. Margolis AU - Peter B. Detwiler Y1 - 2007/05/30 UR - http://www.jneurosci.org/content/27/22/5994.abstract N2 - Neuronal discharge is driven by either synaptic input or cell-autonomous intrinsic pacemaker activity. It is commonly assumed that the resting spike activity of retinal ganglion cells (RGCs), the output cells of the retina, is driven synaptically, because retinal photoreceptors and second-order cells tonically release neurotransmitter. Here we show that ON and OFF RGCs generate maintained activity through different mechanisms: ON cells depend on tonic excitatory input to drive resting activity, whereas OFF cells continue to fire in the absence of synaptic input. In addition to spontaneous activity, OFF cells exhibit other properties of pacemaker neurons, including subthreshold oscillations, burst firing, and rebound excitation. Thus, variable weighting of synaptic mechanisms and intrinsic properties underlies differences in the generation of maintained activity in these parallel retinal pathways. ER -