Biology subjects

Nix, K.

Publications and source records attributed to Nix, K..

3 recordsLinked to original sources

bioRxiv2026

Motivation-dependent communication between cortex and brainstem

Neurons in the medullary brainstem exhibit movement-related patterns of activity, but the neuronal population codes that specify distinct actions, and the mechanisms by which cortex may shape these codes as a function of motivational state, remain unclear. To explore whether coupling between cortex and medulla depends upon motivational context, we trained mice to make both pre-reward "appetitive" licks that served to trigger water availability and rapidly attenuated with satiety, and "consummatory" licks, which occur post-reward release and more slowly attenuated with satiety. Simultaneous recordings from secondary motor cortex and motor medulla revealed that medullary activity was more time-locked than cortical activity to individual licks and exhibited a phase-based population code that encoded lick direction. Correlations between cortex and medulla were stronger during appetitive licks than during consummatory licks, with causal dependency established by optogenetic intervention and supported by multi-region recurrent network models. Population codes underlying behavior shared across the central nervous system, exemplified by cortico-medullary coupling, thus may depend upon the motivational context underlying action.

neuroscience↗

bioRxiv2026

Language Dysfunction Associated with Pathological Brain Connectivity in Children with Epilepsy

Language impairment is common in childhood epilepsy and may arise in part from disruption of the distributed brain networks that support language. In self-limited epilepsy with centrotemporal spikes (SeLECTS)--the most common focal epilepsy of childhood--hyperconnectivity has been linked to poor language outcomes, but the specific network patterns associated with language dysfunction remain unclear, limiting the ability to target neurostimulation rationally. We recorded high-density EEG from 27 children with SeLECTS and 29 age-matched controls during verb generation and rest, and quantified functional connectivity across multiple frequency bands and bilateral frontal, temporal, occipital, and motor regions. Using multivariate pattern analysis, we identified connectivity patterns that predicted language ability, distinguished patterns shared across groups from those specific to SeLECTS and tested whether spatially specific connectivity provided information beyond whole-brain or hemispheric averages and conventional clinical variables. Frontal and occipitotemporal connectivity, particularly within the left hemisphere, predicted language ability across groups, whereas motor-network connectivity emerged as the dominant SeLECTS-specific predictor, linking the epileptogenic network to language dysfunction. Connectivity between specific regions outperformed averaged connectivity measures and predicted language beyond epilepsy diagnosis and antiseizure medication use. Task-based connectivity also outperformed resting-state connectivity. These findings show that language ability is associated with distributed yet spatially specific patterns of brain connectivity, while epilepsy introduces distinct alterations centered on the epileptogenic network. Identifying these disease-specific network patterns provides mechanistic insight into language dysfunction and a rational basis for spatially targeted neuromodulation.

neuroscience↗

bioRxiv2022

Stability of steady-state visual evoked potential contrast response functions

A repeated measure of neural activity that is stable over time when unperturbed is needed to be able to meaningfully measure neuroplastic changes in the brain. With sensory-evoked potentials in particular, repeated presentation of stimuli can generate neuroplasticity by itself under certain conditions. We assessed the repeated-measure within-day and across-day stability of the steady-state visual-evoked potential (ssVEP), a high signal-to-noise electrophysiological readout of neural activity in human visual cortex, in preparation for studies of visual cortical neuroplasticity. Steady-state VEP contrast-sweep responses were measured daily for 4 days (four 20-trial blocks per day, 22 participants). Response amplitudes were stable in individual participants, with measured across-block and across-day coefficients of variation (CV= SD / Mean) of 12{+/-}1% and 19{+/-}2%, respectively. No consistent changes in response amplitude were observed either across blocks or across days. We conclude that contrast-sweep steady-state VEPs provide a stable human neurophysiological measure well-suited for repeated-measures studies.

neuroscience↗