The songbird nucleus HVC (used here as a proper name) contains projection neurons (PNs) that fire temporally sparse bursts of action potentials to playback of the bird's own song (BOS) but are essentially silent when presented with other acoustical stimuli.
Media coverage after the fire was sparse and insensitive, and civic leaders ran away from the incident, not toward it.
Thus, additional coding schemes based on the timing of action potential firing or on sparse synchronous firing have been suggested (Arabzadeh et al., 2006; Diamond et al., 2008b; Jadhav et al., 2009).
We classified cells based on their response to the first stimulation pulse into four categories (Fig. 4): Cells that did not reach firing threshold (n = 4), sparse firing (1 30 APs; n = 5), train firing (>30 APs, n = 6), and cells entering depolarization block (n = 7).
The light evoked firing was done in neurons that were selected for their sparse firing rate in order to better show the ability of light-activated channelrhodopsin to initiate action potential activity.
We show that this mechanism provides an explanation for the sparse firing patterns observed in response to natural stimuli and fits well with a recently observed interaction of excitatory and inhibitory receptive field plasticity.
During vocalizations, HVC exhibits characteristic sparse firing, which suggests it is a key structure for motor encoding of learned song, and arguably analogous to pre-motor vocal areas in humans.
At the level of the ciliomotor neurons, this regulation involves the switch from sparse firing to rhythmic bursting.
Therefore the ability to maintain sparse firing in granule cells at rest could be an important mechanism for energy conservation in the mammalian brain.
Full field stimulation of ganglion cells with random flicker causes a reduction of spontaneous activity, and these neurons then provide only sparse firing that is tightly linked to the brightness transitions [ 27- 33].
