The Song Remains the Same

Abstract

Deafness causes speech to deteriorate, but whether this deterioration reflects an active or passive process is unclear. Birdsong - a learned vocal behavior that resembles speech in its dependence on auditory feedback - also deteriorates following deafening. In their 2000 paper, Brainard and Doupe showed that, following deafening, birdsong deteriorates through an active process mediated by a cortex-basal ganglia (BG) circuit.

Keywords: auditory feedback; basal ganglia; birdsong; vocal learning.

Figure 1. Schematic of the song system and comparative anatomy of cortico-BG circuits in songbirds and mammals

A) The songbird brain (shown in sagittal view) contains specialized song circuitry, including a song motor pathway (SMP; red), important for song production, and an anterior forebrain pathway (AFP; black), which is necessary for juvenile song copying and adult forms of auditory-dependent vocal plasticity. B) The AFP shares many similarities to cortico-BG circuitry in mammals. These include a striatopallidal structure (Area X in songbird) that is interposed between cortical premotor and thalamic regions, and that receives input from dopamine releasing neurons in the ventral tegmental area (VTA). Other abbreviations: HVC (used as a proper name); RA (robust nucleus of the arcopallium), DM (dorsomedial nucleus of the intercollicular midbrain region), nXIIts (tracheosyringeal part of the hypoglossal motor nucleus), VRG (ventral respiratory group, comprising nucleus retroambigualis (RAm) and nucleus parambigualis (PAm)); DLM (medial part of the dorsolateral thalamus), LMAN (lateral magnocellular nucleus of the anterior nidopallium); MC (motor cortex). Figure 1A reproduced from [3] and Figure 1B reproduced from [2].