Intrinsic bursting enhances the robustness of a neural network model of sequence generation by avian brain area HVC

Abstract

Avian brain area HVC is known to be important for the production of birdsong. In zebra finches, each RA-projecting neuron in HVC emits a single burst of spikes during a song motif. The population of neurons is activated in a precisely timed, stereotyped sequence. We propose a model of these burst sequences that relies on two hypotheses. First, we hypothesize that the sequential order of bursting is reflected in the excitatory synaptic connections between neurons. Second, we propose that the neurons are intrinsically bursting, so that burst duration is set by cellular properties. Our model generates burst sequences similar to those observed in HVC. If intrinsic bursting is removed from the model, burst sequences can also be produced. However, they require more fine-tuning of synaptic strengths, and are therefore less robust. In our model, intrinsic bursting is caused by dendritic calcium spikes, and strong spike frequency adaptation in the soma contributes to burst termination.

Stable propagation of a burst through a one-dimensional homogeneous excitatory chain model of songbird nucleus HVC

“…(A similar result was announced independently by Jin and collaborators [7], who studied a more complicated model. We discuss this preprint briefly in Section IV below.)…”

Motor Origin of Precise Synaptic Inputs onto Forebrain Neurons Driving a Skilled Behavior

“…Previously proposed models of HVC were constructed using strong excitatory inputs linking active ensembles of neurons into a purely feedforward network (Li and Greenside, 2006;Jin et al, 2007). Experimentally, intracellular recordings in HVC of zebra finches (Long et al, 2010) has supported the idea that a chain of synaptically connected neurons drives the motor sequence of singing.…”

“…In the mammalian motor cortex, it has been shown that the process of motor learning is associated with a sparsening (Komiyama et al, 2010) and temporal sharpening (Masamizu et al, 2014;Peters et al, 2014) of neural activity as learned sequences emerge. In the juvenile songbird, the activity of single HVC premotor neurons has not yet been described, but the possibility exists that multiple premotor links may be useful for exploring a range of potential vocal behaviors during song learning.…”

Neural mechanisms for learned birdsong

“…A leading candidate is a ''synfire'' chain comprising HVC RA neurons linked together by their local excitatory connections, an idea incorporated into modeling studies of central song patterning networks (Li and Greenside 2006;Jin et al 2007). In fact, the axons of HVC RA neurons extend local collaterals before exiting HVC, forming excitatory synapses with other HVC RA cells, as well as interneurons and HVC X cells, providing a potential substrate for a synfire chain (Mooney 2000;Mooney and Prather 2005).…”