Flexible Coupling of Respiration and Vocalizations with Locomotion and Head Movements in the Freely Behaving Rat

Figure 4

Walking. (a) Example of walking behavior. Left: video frames coinciding with right hindlimb (top) and right forelimb (bottom) contact. Right: respiration (intranasal pressure, a.u.) and frontwards () and upwards () head acceleration. Times with emission of ultrasonic vocalizations are painted in red on the respiration signal. Vertical gray lines mark the time of footsteps (right/left triangles: fore- and hindlimbs; filled and open symbols: left and right limbs). Max. speed at this progression was 0.46 m/s. (b) Alignment of respiration and acceleration signals to footsteps from hind- (left panels) and forelimbs (right panels). For each, left plot is mean ± s.e.m. traces for respiration and accelerations at the footstep times. Right phase plots are distribution of , , and respiration cycle phases at the same footstep times. Colors are as in (a). Red arrows represent mean phase with the amplitude of the vector proportional to Phase Locking Value (a full radius equals PLV = 0.5). As a guide for interpreting these graphs, the phase plots for hindlimb footsteps show that at those times the oscillation was typically near its peak, with a PLV of 0.46; was near its trough with a PLV of 0.30 while respiration was less synchronized, with PLV 0.16 and mean phase near the peak of inhalation. (c) Joint distribution of mean respiratory rate and head acceleration rate for each walking episode with marginal distributions on the sides (top: ; bottom: ). Warm colors represent highest concentration of values (see color gradient in (d)). Dashed line follows the diagonal. Gray shading in the acceleration marginal distribution represents the cases included in the analysis in (d)–(f). (d) Alignment of respiration to all acceleration peaks detected in the analyzed walking progressions. Each row corresponds to a different cycle, sorted from top to bottom by acceleration cycle duration. Dashed lines mark the beginning and end of each acceleration cycle. (e) Phase locking of the respiratory cycle to the acceleration peaks. (f) Phase locking of the acceleration cycle to the peak of exhalation.