The Parasympathetic Nervous System Is Active When You Are Reading a Book

Introduction

Both fourth dimension-domain analysis and frequency-domain analysis are used every bit methods of analyzing autonomic nervous response. Billeci et al. (2018) and Dodo and Hashimoto (2015) recently used both methods of analysis. Frequency-domain assay (spectral analysis) of short (≤5 min) interbeat interval (IBIs, or R–R intervals) time serial typically yields three peaks: 0–0.04 Hz, very low frequency (VLF); 0.04–0.15 Hz, low frequency (LF); and 0.15–0.40 Hz, loftier frequency (HF). The HF component represents parasympathetic nervous arrangement activity and is strongly influenced by respiratory sinus arrhythmia. VLF and LF are used as indicators of sympathetic nervous arrangement activity. However, as noted by Sawada (1999) and Lahiri et al. (2008), the LF and VLF components are affected by both sympathetic and parasympathetic nervous system activities. Therefore, it is hard to apply spectrum analysis to independently measure out sympathetic nervous system activity. Lorenz plot analysis is a type of time-domain analysis. Notably, Lorenz plot analysis allows parasympathetic and sympathetic nervous system activities to be measured separately (Toichi et al., 1997). Lorentz plot analysis uses the cardiac sympathetic index (CSI) as an indicator of sympathetic nervous arrangement activeness; information technology uses the cardiac vagal index (CVI) equally an indicator of parasympathetic nervous system action. Dullard and Hashimoto (2015) constitute that fourth dimension-domain assay (Lorenz plot analysis) is a useful method for examining autonomic nervous system activity during a cold presser examination (CPT), whereas frequency-domain analysis (spectral analysis) of heart charge per unit variability (HRV) is not.

Obrist (1981) suggested that dissimilar coping types (active or passive) are required depending on the stress-inducing task. With active coping, sympathetic nervous arrangement activity increases and parasympathetic nervous system activity decreases from baseline. During passive coping, sympathetic nervous system activity decreases and parasympathetic nervous system increases from baseline. Allen et al. (2007) reported results of a mental arithmetics task that requires active coping using Lorenz plot assay. In the mental arithmetics task, the CSI increased and the CVI did not change, compared to baseline. Dodo and Hashimoto (2015, 2017) conducted CPT studies that required passive coping. In CPT, the CSI did not modify and the CVI increased, compared to baseline. Indexes activated during tasks that required agile or passive coping were consequent with those identified by Obrist; active coping activated CSI, whereas passive coping activated CVI.

Other tasks that require agile coping include speech and mental arithmetic tasks. Most studies of HRV during speech tasks use frequency-domain analysis (spectral analysis; for review, see Bernardi et al., 2001). Nonetheless, respiratory patterns change with utterance during speech. When analyzing HRV using spectral analysis, Sawada (1999) noted that, with changes in respiratory patterns, the values of both HF and LF components increase. Beda et al. (2007) compared tasks with and without utterance. They suggested that the apply of spectral analysis to assess autonomic function during tasks with utterance was problematic.

Therefore, our study aimed to use Lorentz plot assay (i.e., contained analysis of the sympathetic and parasympathetic nervous systems) to examine influence on the autonomic nervous organization during tasks with utterance.

Materials and Methods

Participants

We selected 40 university students to participate in this study. For participating in the experiment, we paid approximately ix Us dollars (1,000 Japanese yen) to each participant, and we provided all students with written informed consent forms before participation. We asked them to refrain from eating or drinking anything other than water for at least 2 h before arriving at the laboratory. Nosotros excluded four volunteers because they were smokers or were taking medications. Because smoking and medications touch the autonomic nervous system, these were not permitted. We also excluded five volunteers due to electrocardiogram (ECG) artifacts. Thus, we included 31 participants (10 male and 21 female; historic period range: nineteen–29 years; mean age: 21.03 years; SD age: 2.17).

Procedure

Stimuli

We prepared several stories that cited the famous classical essay "Tsurezuregusa" ("Essays in Idleness") by Yoshida Kenkō (1330–1332). Words and expressions used in classical literature are rarely used in mod literature. Therefore, participants could not hands read the stories, as they were hard to comprehend. We selected four of the less familiar stories from the essay. We divided each story into 12 texts. We presented the 12 texts on a display at a constant pace. Each text was presented every 13 s. The intertext interval was two s.

Experiment

The study was composed of 3 phases: (ane) resting phase (R phase), (2) silent reading stage (SR phase), and (iii) reading aloud stage (RA phase). Each stage lasted 3 min. Participants were seated and maintained their posture throughout the experiment. In the R phase, they watched a silent movie. In the SR phase, they were shown text on the display and read information technology in silence. During the RA phase, nosotros asked them to read the text presented on the screen with clear enunciation. Based on the findings of Piferi et al. (2000), we streamed a monochrome silent motion picture in the R stage. The content of the motion picture was summer flower scenery that did non change the psychological state of participants. We gave the following instructions to participants prior to the picture: "Delight sit back in the chair. Please spotter the movie in a relaxed posture without moving."

To forestall the autonomic nervous arrangement from beingness afflicted by the content of the presented story, we randomly showed one of the four stories in each phase. We monitored participants' faces using a video camera placed in front of them and observed their commitment to the task. Furthermore, we recorded any comments they made with their consent.

We asked participants to evaluate their subjective states (degrees of arousal and valence) and mood after the silent reading and reading aloud phases. Later on the RA phase, all participants evaluated their functioning on the reading aloud task (cocky-evaluation).

Psychological Interpretation

Subjective state

We queried participants' degree of arousal and valence according to the dimensions of affect proposed by Russell et al. (1989). Nosotros asked participants to appraise their subjective states (degrees of arousal and valence), using a seven-signal Likert scale. For the degree of arousal, the median score (4) was neutral. The highest score represented depression arousal (seven), while the lowest score denoted loftier arousal (1). Regarding valence, the highest score denoted more positive impact (7), the lowest score denoted more negative touch on (i), and the calibration midpoint (iv) represented neutral affect.

Mood

Nosotros asked participants to judge their subjective moods (happy, melancholy, feeling pleasure, sad, lonely, or satisfied) using a vii-point Likert calibration (Sakaki, 2006). Each descriptor was scored from 1 (not applicative) to seven (perfectly applicable). Nosotros applied opposite scoring for three descriptors (melancholy, sad, and alone). We recorded the full score of the vi descriptors every bit the mood score.

Self-evaluation

We directed participants to charge per unit their operation (fluency) on the reading aloud chore, using a seven-point Likert scale that ranged from poor (one) to excellent (7), while the midpoint (4) denoted average performance.

Autonomic Nervous Response

We recorded heart rate in all iii phases. To appraise HRV, we administered an ECG with three Ag–AgCl disposable electrodes (PSC-SC43m, Senstec Co., Ltd., Tokyo, Japan) arranged in a similar mode to that of a atomic number 82 2 configuration (i.e., two electrodes on the breastbone and one on the left lower abdomen). Nosotros digitized the ECG data using a 12 chip A/D converter at a sampling charge per unit of ane kHz (MaP222A, NIHONSANTEKU Co., Ltd., Osaka, Japan) and recorded data to a notebook computer (T60, IBM Japan, Ltd., Tokyo, Japan).

We evaluated HRV using Lorenz plot assay (MaP1060, NIHONSANTEKU Co., Ltd., Osaka, Japan). We observed fluctuations of the IBI and transformed them into an ellipsoid distribution using the Lorenz plot. Following Toichi et al. (1997), a program (MaP1060) calculated the length of the longitudinal (L) and transverse (T) axes within the ellipsoid distribution. The CVI was calculated as a log10 (50 × T) transformation, and the CSI was calculated as L/T (Toichi et al., 1997).

Statistical Analyses

The data were analyzed using IBM SPSS, Version 25. The Shapiro–Wilk exam was applied to evaluate whether the variables considered were unremarkably distributed. If the data had normal distribution, we performed a paired t-test for psychological measures or a one-way repeated-measure assay of variance (ANOVA) for autonomic nervous response with phases. If the information had a non-normal distribution, we performed the Wilcoxon signed-rank test for psychological measures or the Friedman test for autonomic nervous response amidst phases. We carried out postal service hoc analyses with Bonferroni correction.

Results

The Shapiro–Wilk test was applied to evaluate whether the variables considered were commonly distributed. The data were analyzed using IBM SPSS, Version 25.

Psychological Measures

Subjective State

According to the results of the Shapiro–Wilk exam, state had a non-normal distribution in the R, SR, and RA phases. Thus, we used the Wilcoxon signed-rank test for comparison of subjective state. Arousal scores were significantly higher afterward the SR phase (Thou = four.26, SD = 1.26) than afterward the RA stage (M = three.03, SD = 1.17) (p < 0.05). This consequence means that the degree of arousal was college afterward the RA phase. Valence scores were not significantly different afterwards the SR phase (M = four.48, SD = 0.89), relative to those of the RA phase (M = 4.23, SD = 0.99; Table 1).

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Table 1. Psychological estimation.

Mood

According to the results of the Shapiro–Wilk test, mood had a non-normal distribution in the R, SR, and RA phases. Thus, nosotros used the Wilcoxon signed-rank exam for comparing of mood; notably, information technology did not significantly differ between the SR stage (M = 27.74, SD = 4.88) and the RA stage (Table 1).

Self-Evaluation

The mean self-evaluation score was iii.26 (SD = 1.41).

Autonomic Nervous Response

According to the results of the Shapiro–Wilk examination, CSI and CVI had normal distributions in the R, SR, and RA phases. Thus, we conducted a i-style repeated-measures ANOVA of CSI and CVI values with phase (resting, silent reading, and reading aloud) as the factor. We observed a significant primary result of the stage on CSI [F(2, lx) = three.95, p < 0.05, $η_{p}^{two}$ = 0.12]. CSI values during the R phase (Chiliad = 2.96, SD = 0.91) were significantly lower than in the RA phase (One thousand = three.33, SD = 0.95; d = 0.40; Figure 1). We observed a meaning main consequence of stage on CVI [F(2, 60) = 7.40, p < 0.05, $η_{p}^{2}$ = 0.twenty]. CVI values in the R phase (Chiliad = iv.35, SD = 0.33) and the SR phase (Chiliad = four.29, SD = 0.36) were significantly lower than those in the RA phase (M = 4.44, SD = 0.26; R versus RA: d = 0.30, SR versus RA: d = 0.48; Figure ii).

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Effigy ane. Cardiac sympathetic alphabetize (CSI) changes during the resting, silent reading, and reading aloud phases. Values are expressed every bit ways and SDs. ^∗ p < 0.05.

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Figure 2. Cardiac vagal index (CVI) changes during the resting, silent reading, and reading aloud phases. Values are expressed as ways and SDs. ^∗ p < 0.05.

Give-and-take

Nosotros observed that the degree of arousal was significantly college after the RA stage than afterward the SR phase. Moreover, the sympathetic nervous response was significantly college during the RA phase than during the SR phase, and the parasympathetic nervous response was significantly higher during the RA phase than during the R stage.

Psychological Response

The caste of arousal was greater later the RA phase than after the SR phase. However, there was no difference in valence after the SR phase, nor after the RA phase. In dissimilarity, because there is no significant difference betwixt valence and moods, the emotional influence on the autonomic nervous arrangement acquired past the tasks is considered equivalent for the silent reading and reading aloud weather. The self-evaluation scores were slightly lower than the midpoint ("average") of the seven-category scale. Thus, participants evaluated their reading quality as below average. This signifies that the chosen text was challenging. Co-ordinate to the results of the psychological ratings, reading aloud produces greater psychological loading.

Autonomic Nervous System

There was no significant difference between CSI values, which is an index sympathetic nervous system activeness, during the resting and silent reading phases. However, it was found that CSI values significantly increase during the RA stage rather than in the SR phase. The CSI findings during the RA phase are consistent with an increase in the sympathetic nervous system due to tasks requiring active coping, as noted by Obrist (1981). The CSI did not increase more in the SR phase than during the R phase; this finding suggests that psychological loading in the SR phase is ineffective as an active coping job.

Obrist (1981) indicated that the parasympathetic nervous organization activity decreases below baseline during tasks that require active coping. Nonetheless, our data prove that the CVI, a measure of the parasympathetic nervous system, rises significantly more during the RA phase than in the R stage. The reading aloud chore requires voice and causes participants to respire (expirate) more in the resting and silent reading tasks. Increases in the CVI are considered to effect from activating the parasympathetic nervous system by said expiration. Although the speech chore required participants to perform agile coping, information technology likewise activated both the sympathetic and parasympathetic nervous systems during expiration.

Allen et al. (2007) utilized Lorenz plot assay with a mental arithmetic chore that required agile coping; they found that the CSI increased during the arithmetic chore, which was consistent with our findings in CSI during the RA stage. We speculate that the increase in CSI (i.e., the sympathetic nervous arrangement alphabetize) arose from active engagement in the chore amidst participants. Allen et al. (2007) also reported that the CVI did not change during the mental arithmetic chore. However, we found that the CVI increased during the RA stage. In the RA phase, respiratory pattern changed with utterance, but not with the mental arithmetic chore. The departure in respiratory pattern may have led to the difference in CVI between RA and mental arithmetics tasks. We considered that the increase in CVI (i.e., the parasympathetic nervous arrangement alphabetize) during the RA phase resulted from changes in respiratory blueprint during oral communication.

Limitations

The main purpose of this study was to examine influence on the autonomic nervous system during a reading task with utterance. However, we did not ostend if the participants were reading with attempt or not reading at all during the SR phase. For example, a retentivity task is a method for confirming the date of the participants in reading. Adding a memory task to the reading tasks would change this to a dual job, which is a higher psychological load. Thus, we would not be able to clearly discern the effect of utterance lone. In the present study, we did not add together a memory task during silent reading or reading aloud. We monitored participants' faces using a video camera placed in front end of them; thus, we observed their delivery to the task. No participants closed their optics except to glimmer during the SR phase.

We did non perform the SR and RA phases in random order. The outcome of the RA phase may take been contaminated by habituation. However, arousal during the RA phase was significantly higher than in the SR phase. This suggests that habituation to the reading task did not affect the outcomes of the RA phase.

Conclusion

For speech tasks requiring active coping, we separately analyzed sympathetic and parasympathetic nervous system action, using Lorenz plot analysis. Our results suggest that each effect on the autonomic nervous system is evoked by ii unlike behaviors: one behavior was the activity of reading aloud, which required active coping and led to the activation of the sympathetic nerve system. The other behavior was the activeness of speech with utterance; respiratory pattern inverse during oral communication, and this change led to the activation of the parasympathetic nervous organization. When evaluating the activeness of the autonomic nervous arrangement in tasks associated with utterance, Lorenz plot analysis is recommended.

Data Availability

The datasets generated for this study are available on request to the respective author.

Ideals Statement

This report was carried out in accordance with the recommendations of the Psychological Scientific discipline Ideals Review Committee guidelines, the Ethics Committee of Health Sciences University of Hokkaido. The protocol was approved past the Ethics Committee of Health Sciences Academy of Hokkaido. All subjects gave written informed consent, in accordance with the Declaration of Helsinki.

Writer Contributions

ND contributed to the design of the experiment, functioning of the experiment, data assay, and writing of the manuscript. RH contributed to the design of the experiment, performance of the experiment, and writing of the manuscript.

Funding

This piece of work was supported by the JSPS (Japan Club for the Promotion of Science) KAKENHI Grant No. 26380939 (ND) and the Research Institute of Personalized Health Sciences (RH).

Disharmonize of Interest Statement

The authors declare that the enquiry was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abbreviations

CSI, cardiac sympathetic index; CVI, cardiac vagal alphabetize; HF, high frequency (0.15–0.40 Hz); LF, low frequency (0.04–0.fifteen Hz); R stage, resting phase; RA stage, reading aloud phase; SR phase, silent reading phase; VLF, very low frequency (0–0.04 Hz).

References

Allen, J. J. B., Chambers, A. S., and Towers, D. Due north. (2007). The many metrics of cardiac chronotropy: a pragmatic primer and a cursory comparison of metrics. Biol. Psychol. 74, 243–262. doi: 10.1016/j.biopsycho.2006.08.005

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