Movement signaling in ventral pallidum and dopaminergic midbrain is gated by behavioral state in singing birds

Abstract

Movement-related neuronal discharge in ventral tegmental area (VTA) and ventral pallidum (VP)is inconsistently observed across studies. One possibility is that some neurons are movementrelated and others are not. Another possibility is that the precise behavioral conditions matterthat a single neuron can be movement related under certain behavioral states but not others. We recorded single VTA and VP neurons in birds transitioning between singing and non-singing states, while monitoring body movement with microdrive-mounted accelerometers. Many VP and VTA neurons exhibited body movement-locked activity exclusively when the bird was not singing.During singing, VP and VTA neurons could switch off their tuning to body movement and become instead precisely time-locked to specific song syllables. These changes in neuronal tuning occurred rapidly at state boundaries. Our findings show that movement-related activity in limbic circuits can be gated by behavioral context.

Songbird subthalamic neurons signal song timing and error and project to dopaminergic midbrain

“…Thus, unlike the nuclei of the song system, where all neurons are singing-related, the songbird STN may serve other more general motor evaluation functions. Notably, a similar intermixing of singing- and non-singing related signals were observed in VP and VTA, and both of these structures exhibited a similarly small fraction of neurons that encoded song timing or error (Chen et al 2019, 2021; Gadagkar et al 2016). A key feature of the DA evaluation signals in singing birds was that the activations occurred when a predicted error did not occur.…”

“…Our results showing movement aligned firing rate modulation of finch STN neurons is consistent with the known motor functions of the mammalian STN (Fife et al 2017; Georgopoulos et al 1983; Hamani et al 2004). In addition, neurons in other areas of the finch brain, namely VTA and VP have been shown to contain neurons that encode movement and display differential encoding of movement depending on the behavioural state of the animal (singing versus nonsinging) (Chen et al 2021). Our results suggest that the finch STN also contains a population of neurons encoding movement independent of state and another smaller population that exhibits singing-related gating of movement signaling.…”