Fig. 4.

Neural activity is modulated by respiration. (A1) Exemplary neuron in the STN whose spiking activity was significantly non-uniform along the respiratory cycle (surrogate test on Rayleigh statistic for non-uniformity, P = 10⁻⁴). Top: Circular histogram of spike density across the respiratory phase. The green line represents the mean vector of the distribution, with its angular direction being the preferred spiking phase for the neuron (ϕ = 3.8 rad). Middle: Raster plot for the neural spikes as a function of the respiratory phase across the different respiratory cycles. Bottom: Cumulative histogram of spikes across respiratory cycles binned in π/5 rad bins. (A2) Exemplary neuron in the Vim whose spiking activity was significantly non-uniform along the respiratory cycle (surrogate test on Rayleigh statistic for non-uniformity, P = 2 × 10⁻³). Conventions are as in panel (A1). Preferred spiking phase ϕ = 5.1 rad. (B) Proportion of neurons whose activity was significantly modulated by the respiratory phase in the three recorded regions. The total number of neurons tested in each region is shown in parentheses. (C) Distribution of preferred spiking phases for the 22 significantly modulated neurons. Circles indicate individual values (color-coded by region). No significant phase preference overall was identified [Rayleigh test for non-uniformity, z(21) = 0.37, P = 0.69].