Phase-Dependent Cortical Stimulation and Motor Control

Status: In development

Project Definition

This project investigates how phase-dependent cortical stimulation (PDS) differentially perturbs motor control and neural synchrony, and whether neural features can predict the direction and magnitude of motor disruption.

The central aim is to move beyond neural correlates of stimulation and quantify how timing-specific perturbations reshape the structure of motor behavior.

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Research Questions

• Do peak- and trough-locked stimulation produce symmetric motor effects?
• Are phase-specific motor effects conserved across individuals despite variability in baseline performance?
• Why do single motor metrics fail to capture stimulation outcomes?
• Can neural state features predict behavioral susceptibility to phase-targeted stimulation?

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Key Contributions

Motor Outcome Asymmetry

Most PDS studies focus on neural effects:

• Peak stimulation → increased PAC
• Trough stimulation → decreased PAC

This work demonstrates that motor consequences are asymmetric:

• Over-perturbation (peak) leads to disproportionately worse motor disruption
• Under-perturbation (trough) does not produce an equivalent inverse effect

Neural symmetry does not imply motor symmetry.

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Directional Consistency Over Effect Size

While absolute motor performance varies across individuals:

• Phase-specific motor effects are directionally consistent
• The sign of the effect (disruptive vs permissive) is conserved even when magnitude differs

This suggests phase dependence reflects a shared control principle rather than subject-specific tuning.

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Multivariate Motor Signatures

Motor behavior is inherently multidimensional.

Dimensionality reduction reveals orthogonal motor axes:

• PC1: Vigor–precision tradeoff
• PC2: Tempo modulation
• PC3: Variability–stability balance

No single metric captures stimulation effects.
Motor quality emerges from multivariate structure, not scalar measures.

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Predictive Framing

Rather than post-hoc explanation, this project adopts a predictive approach.

Neural features including:

• Phase–amplitude coupling (PAC)
• Spectral power
• Neural synchrony

are used to predict:

• Direction of motor change
• Magnitude of behavioral disruption

Stimulation effects are treated as state-dependent and forecastable, not uniform.