Arousal and sustained attention fluctuate differently with respiration in younger and older adults

Figures

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  Fig. 1.. Task schematic of the Gradual Contrast Change Detection with Experience Sampling (GradCCD-ES) Task. A continuously presented checkerboard, anulus stimulus decreases in contrast after variable intervals which is the target to be identified by participants, who respond with a mouse click upon recognition. Additionally, the stimulus is interrupted with experience-sampling thought probes (TPs) which ask the participant to categorise their attentional state immediately prior to the TP presentation. Each block consists of 48 targets, 16 TPs, and lasts approximately 8 min each. A testing session consisted of eight blocks.

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  Fig. 2.. Bar graphs ofpvalues returned from Rayleigh tests against a null hypothesis of uniformity for respiratory phase angles at the times of target presentation, target response, thought probe (TP) presentation, and TP response. Older adults (OA) in red, younger adults (YA) in blue. Values displayed on graphs indicate the percentage of participants in each group that showed significant (p < 0.05; dashed line) non-uniformity. Significant non-uniformity was a majority group finding (except YA TP presentation), but not an ubiquitous one.

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  Fig. 3.. Polar scatter graphs of the mean resultant vector lengths (VL; radial axis) and respiratory phase angles (angular axis in radians), indicating the strength and angle of respiratory-task event phase-locking, respectively. Dots represent participant means and solid lines represent the direction of the group mean angles, older adults (OA) in red, younger adults (YA) in blue. 0 radians represents exhalation onset, and the respiratory cycle proceeds anti-clockwise. The majority of respiratory phase angles occurred between mid-exhalation and early inhalation.

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  Fig. 4.. Grand-averaged (a) respiration and (b) pupil diameter, -7000 ms pre- and -7000 ms post-target presentation, for each of the inter-target intervals (3, 5, 7 s). Mean respiration and pupil diameter were calculated as the instantaneous phases over the target period, then cosine transformed to give an amplitude-agnostic, phase waveform. Top plots (black) show grand averages of all participants and bottom plots show grand averages split for older adult (OA; reds) and younger adult (YA; blues) groups. Lighter colours either side of mean represent the standard error of the mean (SEM). Vertical dashed line represents target presentation time. Vertical solid lines mark the time of the pre-target peak.

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  Fig. 5.. Pupil diameter amplitude, z-score normalised over the respiratory cycle. After preprocessing, pupil diameter was averaged within a moving phase window bin across the respiratory cycle, window of length π/36 with a 75% overlap. Plotted line with shaded area shows the mean normalised pupil diameter amplitude for each respiratory phase bin, shaded area represents the standard error of the mean (SEM). Plotted line with no shading shows thetstatistic resulting from one-sample permutation testing against 1000 sets of simulation data. Dots above the line indicate significant (p< 0.05) phase bins and dashes indicate phases still significant following multiple comparisons correction. Top shows resultant plot, age groups combined (black), right shows split by the older adult (OA; red) and younger adult (YA; blue) groups. Bottom graphs show the respiratory waveform for reference. The dashed lines on the respiratory waveform represent an approximate window which was commonly phase-locked to task events (as per previous analyses).

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  Fig. 6.. Electroencephalography (EEG)-derived frontal delta and theta, and posterior alpha and steady-state visually evoked potential (SSVEP) over the respiratory cycle. After preprocessing and organising by frequency, frequency-power was averaged within a moving phase window bin across the respiratory cycle, window of length π/36 with a 75% overlap. Plotted line shows thetstatistic resulting from one-sample permutation testing against 1000 sets of simulation data. Dots above the line indicate significant (p< 0.05) phase bins and dashes indicate phases still significant following multiple comparisons correction. Left shows resultant plot, age groups combined (black), right shows split by the older adult (OA; red) and younger adult (YA; blue) groups. Bottom graphs show the respiratory waveform for reference. The dashed lines on the respiratory waveform represent an approximate window which was commonly phase-locked to task events (as per previous analyses).