Biology subjects

Margoliash, D.

Publications and source records attributed to Margoliash, D..

3 recordsLinked to original sources

bioRxiv2024

Cortical Representation of the Glottal Events during Speech Production

To learn complex motor skills, an organism must be able to assign sensory feedback events to the actions that caused them. This matching problem would be simple if motor neuron output led sensory feedback with a fixed, predictable lag. However, nonlinear dynamics in the brain and the bodys periphery can decouple the timing of critical events from that of the motor output which caused them. During human speech production, for example, phonation from the glottis (a sound source for speech) begins suddenly when subglottal pressure and laryngeal tension cross a sharp threshold (i.e. a bifurcation). Only if the brain can predict the timing of these discrete peripheral events resulting from motor output, then, would it be possible to match sensory feedback to movements based on temporal coherence. We show that event onsets in the human glottal waveform, as measured using electroglottography, are reflected in the human electroencephalogram during speech production, leading up to the time of the event itself. Conversely, glottal event times can be decoded from the electroencephalogram. After prolonged exposure to delayed auditory feedback, subjects recalibrate their behavioral threshold for detecting temporal auditory-motor mismatches, and decoded event times decouple from actual movements. This suggests decoding performance is driven by plastic predictions of peripheral timing, providing a missing component for hindsight credit assignment in motor control, in which specific feedback events are associated with the neural activity that gave rise to movements. We discuss parallel findings from the birdsong system suggesting that results may generalize across vocal learning species. Significance StatementTo learn complex motor skills such as speech, the brain must pair actions with sensory feedback. However, feedback is delayed in time relative to actual movement, rendering this "hindsight credit assignment" problem a nontrivial task. We present evidence that events in the glottis, the articulatory organ that generates sound for human speech, are predictively encoded in the human brain during speech production. Given that corresponding events in auditory feedback are known to be prominently encoded in cortex, this highlights a common temporal marker by which articulatory gestures and sensory feedback could be aligned. Findings suggest activity in the human vocomotor system is shaped by biophysical dynamics in the vocal periphery, aligning with corresponding results in the birdsong system.

neuroscience↗

bioRxiv2024

Bursts from the past: Intrinsic properties link a network model to zebra finch song

Neuronal intrinsic excitability is a mechanism implicated in learning and memory that is distinct from synaptic plasticity. Prior work in songbirds established that intrinsic properties (IPs) of premotor basal-ganglia-projecting neurons (HVCX) relate to learned song. Here we find that temporal song structure is related to specific HVCX IPs: HVCX from birds who sang longer songs including longer invariant vocalizations (harmonic stacks) had IPs that reflected increased post-inhibitory rebound. This suggests a rebound excitation mechanism underlying the ability of HVCX neurons to integrate over long periods of time throughout the song and represent sequence information. To explore this, we constructed a network model of realistic neurons showing how in-vivo HVC bursting properties link rebound excitation to network structure and behavior. These results demonstrate an explicit link between neuronal IPs and learned behavior. We propose that sequential behaviors exhibiting temporal regularity require IPs to be included in realistic network-level descriptions.

neuroscience↗

bioRxiv2023

Rhythmically bursting songbird vocomotor neurons are organized into multiple sequences, suggesting a network/intrinsic properties model encoding song and error, not time

In zebra finch, basal ganglia projecting "HVCX" neurons emit one or more spike bursts during each song motif (canonical sequence of syllables), which are thought to be driven in part by a process of spike rebound excitation. Zebra finch songs are highly stereotyped and recent results indicate that the intrinsic properties of HVCX neurons are similar within each bird, vary among birds depending on similarity of the songs, and vary with song errors. We tested the hypothesis that the timing of spike bursts during singing also evince individual-specific distributions. Examining previously published data, we demonstrated that the intervals between bursts of multibursting HVCX are similar for neurons within each bird, in many cases highly clustered at distinct peaks, with the patterns varying among birds. The fixed delay between bursts and different times when neurons are first recruited in the song yields precisely timed multiple sequences of bursts throughout the song, not the previously envisioned single sequence of bursts treated as events having statistically independent timing. A given moment in time engages multiple sequences and both single bursting and multibursting HVCX simultaneously. This suggests a model where a population of HVCX sharing common intrinsic properties driving spike rebound excitation influence the timing of a given HVCX burst through lateral inhibitory interactions. Perturbations in burst timing, representing error, could propagate in time. Our results extend the concept of central pattern generators to complex vertebrate vocal learning and suggest that network activity (timing of inhibition) and HVCX intrinsic properties become coordinated during developmental birdsong learning.

neuroscience↗