The neural language of song: Brain mechanisms for sensorimotor syntax control

Descripción del proyecto

Sustratos neuronales de la sintaxis jerárquica

Las reglas sintácticas jerárquicas definen cómo se organizan las unidades simples para formar otras más complejas. Las secuencias motrices obedecen a reglas sintácticas jerárquicas, ya se trate de atarse los cordones o de cantar una canción. Financiado por el Consejo Europeo de Investigación, el equipo del proyecto NeuralSyntax pretende estudiar el canto del canario y descifrar reglas sintácticas jerárquicas mediante la investigación de las secuencias conductuales y neuronales. Partiendo de sus estudios anteriores para identificar estados neuronales ocultos que mantienen una memoria de sílabas cantadas durante varios segundos y predicen las transiciones siguientes, el equipo intentará diseccionar los mecanismos de transición. Procurará revelar la actividad neuronal subyacente a las transiciones entre sílabas, la selección de la siguiente sílaba, la adaptación de las reglas sintácticas a nuevas canciones y la remodelación estacional de las reglas sintácticas.

Objetivo

Our motor sequences obey syntax rules. From tying shoes to giving a speech, choosing the next action requires our brain to remember past actions, bridge across many seconds, and apply rules that create hierarchical syntax. Whereas past studies revealed how primary motor cortex drives actions, we poorly understand the transition mechanisms by which the brain strings actions into hierarchical variable sequences. The key obstacle is identifying deep hierarchical syntax rules in behavior and in neural sequences. This obstacle is met by studying birdsong that naturally segments to sequences of syllables. In the zebra finch, juveniles learn once from a tutor and fix a single sequence driven by a robust song-locked activity. Here, to study hierarchical syntax rules I will use canaries: virtuosos that learn and adapt such rules along and across seasons. Canaries produce a huge repertoire of songs that enable separate analysis of neural states and syllable acoustics when studying their rich and dynamic syntax rules. My previous work in canaries identified hidden neural states that keep a memory of sung syllables over several seconds and predict upcoming transitions. Here, I leverage this model to dissect transition mechanisms and elucidate: 1) neural activity in the premotor nucleus HVC that underlies flexible transitions between syllables; 2) integration of auditory and thalamic inputs for applying hierarchical syntax rules to select the next syllable; 3) neural state dynamics when adapting syntax rules for new songs; and 4) seasonal remodeling of HVC via neurogenesis. We use imaging, electrophysiology, and neural network simulations that integrate data across behavior, neural activity, and circuit levels of analysis. Our work will map the process by which basal ganglia and thalamocortical circuits generate and adapt hierarchical syntax rules over time, sensory, and social contexts, and might offer insights to dysfunction of motor sequence control in maladaptive conditions.