An improved model of forebrain-projecting cortical neurons in the oscine songbirds -

Abstract

Since the late 1960s, songbirds have emerged as a notable neurobiological model for studying aspects of human verbal communication. Songbirds learn to arrange their song elements, analogous to how humans learn to produce spoken sequences with syntactic structure. One of the most fundamental questions in neuroscience is pursued through the study of songbirds, more specifically through the study of zebra finches. Questions on how the brain generates complex sequential behaviors and the neural mechanisms that underlie sequential behavior are the holy grail of the neuroscience field. The telencephalic nucleus HVC (proper name) within the songbird, analogue to the mammalian pre-motor cortex, is situated at a critical point in the pattern-generating premotor brain circuitry of oscine songbirds. HVC contains three interconnected populations of neurons, HVCRA (projecting to forebrain), HVCX (projecting to basal ganglia) and HVCINT (interneurons), which possess specific patterns of excitatory and inhibitory connectivity. HVCRA neurons were of particular interest in this research due to their significance in the propagation of sequential activity, which encodes the zebra finch’s song. Whole-cell intracellular recordings were collected from HVCRA neurons within zebra finch brain slices. The biological data collected was used to create and calibrate a conductance-based HVCRA model. The mathematical model unveiled the expression of important ionic currents, which govern the dynamics of these neurons and that are presumably playing an imperative role in the rhythmogenesis that this cortical area exhibits during singing. The new model allows for a better understanding of the ionic currents responsible for HVCRA’s characteristic sparse bursting firing patterns. The presence of the ionic currents could later be tested and verified using neuropharamacology.