Article Figures & Data
Figures
- Figure 1.
Schematic overview of the study and the research hypothesis. Participants carried out a dichotic listening task in which they were presented with unpredictable sequences of brief auditory sounds to each ear (tone bursts in one ear and chirps in the other ear) and were instructed to attend to one ear at a time. Their behavioral task was to detect occasional attenuated deviant stimuli in the attended stream. Throughout the experiment, electromyographic activity was recorded from the surface of the left and right posterior auricular muscles (PAMs). These data were analyzed to investigate the hypothesis that sustained anticipatory selective attention would increase the tonic PAM amplitude on the attended side.
- Figure 2.
Time-resolved plot of tonic posterior auricular muscle (PAM) amplitudes during listening trials, categorized according to activity that was recorded from the side that was presented with tone bursts (left) and chirps (right). Mean amplitudes were calculated for five non-overlapping epochs of 36 s duration each over the trial duration of 180 s. Plotted values were assigned to segment centers. Solid lines represent the grand-average amplitudes across participants (N = 17) for the left and right PAM under attend-left and attend-right conditions, and shaded backgrounds show the associated standard errors. Most prominently, and consistently across the sides of presentation of tone bursts and chirp stimuli, tonic amplitudes for both PAMs were larger when attention was directed toward as opposed to away from their side of the head. Additionally, all waveforms presented a general decline in tonic amplitude over the course of the listening trials.
- Figure 3.
Distributions of tonic posterior auricular muscle (PAM) amplitudes for the first and last trial segments from the primary tonic analysis based on ongoing activity, categorized according to activity that was recorded from the side that was presented with tone bursts (left) and chirps (right). The plotted amplitudes correspond to the first and last segment of the time-resolved data shown in Figure 2 and were used to carry out statistical analyses via repeated-measures analyses of variance (RMANOVAs). Boxplots represent the amplitude distributions across participants (N = 17) for the left and right PAM under attend-left and attend-right conditions, and colored dots indicate values that deviated by more than 1.5 times the inter-quartile range from the lower or upper quartile. Consistent with the time-resolved plots shown in Figure 2, the tonic amplitudes for both PAMs were larger when attention was directed toward as opposed to away from their side of the head, independent of the type of stimulus that was presented to each side. Additionally, tonic amplitudes were consistently larger at the beginning as compared to the end of the listening trials.
- Figure 4.
Rectified posterior auricular muscle (PAM) response (PAM) waveforms elicited by chirp stimuli from the secondary tonic analysis based on time-locked activity, categorized into responses to standard (left) and deviant (right) chirps. Amplitudes were normalized with respect to the pre-stimulus period between −100 and 0 ms, ensuring that baseline amplitude differences were not influenced by PAM reflex amplitudes. Solid lines represent the grand-average waveforms across participants (N = 17) for the left and right PAM under attend-left and attend-right conditions, and shaded backgrounds show the associated standard errors. Consistent across both types of chirp stimuli, tonic pre-stimulus amplitudes for both PAMs were larger when attention was directed toward as opposed to away from their side of the head. The noisier baselines in the waveforms elicited by the deviant chirps can be attributed to the much fewer single-trials included in the averages to these infrequent stimuli. Modulations of the PAM reflex were not analyzed in this study and will be presented elsewhere.
Tables
- Table 1.
Summary of statistical details for repeated-measures analyses of variance (RMANOVAs) that were carried out for the tonic posterior auricular muscle (PAM) amplitudes shown in Figure 3
RMANOVA factors Test statistic Side of tone bursts Side of chirps F(1, 16) 0.27 0.05 PAM location p 0.61 0.83 0.02 2.81 · 10−3 F(1, 16) 11.86 11.60 Listening condition p 3.34 · 10−3** 3.61 · 10−3** 0.43 0.42 F(1, 16) 12.34 7.83 Time p 2.88 · 10−3** 0.01* 0.44 0.33 F(1, 16) 0.06 1.21 PAM location × Listening condition p 0.81 0.29 3.65 · 10−3 0.07 F(1, 16) 2.41 0.40 PAM location × Time p 0.14 0.53 0.13 0.02 F(1, 16) 0.04 0.91 Listening condition × Time p 0.85 0.35 2.45 · 10−3 0.05 F(1, 16) 0.01 0.42 PAM location × Listening condition × Time p 0.92 0.53 6.54 · 10−4 0.03 Separate analyses were done for the PAMs on the sides of the head where tone bursts and chirps were presented. The table provides F-values, p-values, and standardized effect sizes as partial eta-squared (
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