Changes in a Chaotic Fluctuation of Eye Movement Produced by Stiff

Shoulder Treatment

Eri Shibayama

, Kasumi Tanaka

and Taira Suzuki

Graduate School of Psychology, J.F. Oberin University, Machida, Tokyo 194-0294, Japan

Moriyama Rehabilitation Clinic, Shinagawa 142-0054, Japan

Keywords: Chaos, Eye Movement, Shoulder Stiffness, Largest Lyapunov Exponent(LLE).

Abstract: Many Japanese people experience physical symptoms known as Katakori (shoulder stiffness or neck pain),

which is considered a psychosomatic phenomenon that is strongly correlated with psychological stress and

stress caused by human relationships. This study examined changes in the chaos of eye movement

accompanied by changes in depression by treating shoulder stiffness. Participants scoring over 1SD from the

mean score having high depression and shoulder stiffness were included in the intervention group and

provided stretching intervention. The control group included participants having high depression and shoulder

stiffness, but they were not provided with the stretching intervention. Moreover, participants scoring lower

than 1SD from the mean score having low depression and no shoulder stiffness were included in the Low

group. The experimental group exercised using a neck and shoulder relaxation technique using a stretch pole

recommended by the stretch pole official site. The results of the experiment indicated that eye movement

LLE(Largest Lyapunov Exponent) changed more significantly when the depression level was high. Moreover,

LLE and the degree of change in LLE decreased after receiving treatment for the stiff shoulder. It is suggested

that the chaotic fluctuation of eye movement might decrease when depression improved, i.e., in people with

low depression.

1 INTRODUCTION

Many Japanese people experience physical

symptoms known as Katakori (shoulder stiffness or

neck pain), which is considered a psychosomatic

phenomenon that is strongly correlated with

psychological stress and stress caused by human

relationships. According to Yokota (2000), the

expression, “having a stiff shoulder” was first used by

Soseki Natsume (1867-1916), a famous Japanese

novelist. Katakori is a symptom of subjectively,

having a sense of discomfort, depression, and mild

pain caused by movement in the neck, upper scapular,

scapular, and middle scapular regions. Objectively,

when palpating these muscles, they are abnormally

tense, and there are tender points or lumps. The

mechanisms of Katakori are diverse, and the causes

of Katakori are as follows; overuse of muscles,

accumulation of fatigue factors caused by blood

circulation disorders, poor blood circulation in

shoulder muscles caused by arteriosclerosis,

insufficient blood circulation caused by maintaining

a particular posture for a long time, such as unnatural

body position, bad posture, humpback, sloping

shoulders, and scoliosis, psychological tension, and

fibrositis of muscles, among others (Sasaki, 1994).

Currently, in Japan, complaints of Katakori are

placed first in the ranking of complaints of physical

symptoms in women, and second in men after

backache (Ministry of Health, Labor and Welfare,

2010). Thus, Katakori is a symptom with a high ratio

of complaints in Japan. In English, however, Katakori

is mainly expressed by using “neck” as follows; neck

pain, chronic neck pain, chronic nonspecific neck

pain, cervical strain, neck tension, stiff neck, and

neck. There are a few terms related to shoulders.

“Neck pain” or “chronic nonspecific neck pain,”

which are often used in documents, are considered

close to the symptom of Katakori in Japan

(Morimoto, 2010). According to Sasaki (1994),

internationally, there are many translations of

Katakori, suggesting there are differences in the

sensory expression of Katakori depending on the

country. Sasaki (1994) indicated that “shoulder

stiffness” might be the most appropriate translation of

Katakori for writing academic papers. Therefore, in

172

Shibayama, E., Tanaka, K. and Suzuki, T.

Changes in a Chaotic Fluctuation of Eye Movement Produced by Stiff Shoulder Treatment.

DOI: 10.5220/0008895501720178

In Proceedings of the 13th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2020) - Volume 4: BIOSIGNALS, pages 172-178

ISBN: 978-989-758-398-8; ISSN: 2184-4305

this article, we used shoulder stiffness as the term

expressing Katakori.

In Japan, shoulder stiffness is regarded as a

physical symptom caused by mental factors.

Takaguchi & Ishoshima(1989) reported that the

frequency of shoulder stiffness associated with

neurosis, i.e. “psychogenic” shoulder stiffness, was

72% in a survey conducted in 1981. Matsuura,

Fuzimoto, Koga, Yasuno, & Sakai(2016) reported

that university students having shoulder stiffness had

high perceived stress or anxiety, and their mental and

physical health levels were rather low. Nagao, Endo,

& Yokota (2011) indicated that although there are

individual physical differences in the position of

shoulder stiffness on the surface or muscle quality,

the correlation between self-palpation of stiffness and

the feeling of stress was relatively high, suggesting

there might be psychogenic factors in shoulder

stiffness. Moreover, Tanaka & Suzuki (2012)

reported that shoulder stiffness and depression, as

well as anxiety, are correlated, and depression was

significantly reduced by providing treatment for

shoulder stiffness.

1.1 Chaos

At the end of the twentieth century, terms such as

“Chaos”, “Fractals”, and “Complex systems” got

much attention in the field of science. Along with The

Theory of Relativity and quantum mechanics, chaos

was sometimes referred to as the three biggest

findings of the twentieth century in the field of

science. Chaos, as academic jargon, in general terms

does not mean, “disordered”. Chaos might be the

order with a dynamic fluctuation. There has been no

strict definition of chaos to date. According to Aihara

(1993), chaos is “a phenomenon with very

complicated, irregular, and unstable behaviors

because of the nonlinearity of the system, although

the system is following deterministic laws, and it is

impossible to predict the future state.” Chaos might

be expressed as a “fluctuation” to facilitate

understanding. A chaotic fluctuation is observed in

various phenomena. The fluctuation is expressed by

quantitative values such as Largest Lyapunov

Exponent (LLE), which is a quantification of

sensitivity to the initial conditions, which is one of the

characteristics of chaos. To date, many bio-

information is reported as chaos. Among them,

research on brain waves from the perspective of chaos

is most advanced because of the ease of measurement.

Many researchers have indicated a correlation

between a chaotic fluctuation expressed by LLE and

mental and physical health.

1.2 Eye Movement

Previous studies have reported that various mental

symptoms and eye movements are correlated. Eye

Movement Desensitization and Reprocessing

(EMDR) is a well-known example of treatment using

eye movement. It is a technique of cognitive

behavioral therapy, developed mainly for PTSD

treatment, effective for mood disorders and anxiety

disorders caused by traumatic experiences (Arimura

et al., 2000).

Sharifa et al. (2013) indicated that the interval

between blinks and the mean duration of blinks were

shorter in patients with depression, compared to

healthy participants. Based on the results depression

screening using eye movement has been developed.

Nishiura, Morita, Ishii, Igimi, & Maeda (2009)

compared exploratory eye movements between

patients with schizophrenia and healthy participants

by presenting a circle and a photo of an infant’s face.

The results indicated that the total moving distance of

the left exploratory eye movement of schizophrenia

patients is shortened when presenting an infant’s

smiling face and a circle, which was different from

healthy participants. Therefore, exploratory eye

movement is regarded as a useful

psychophysiological index.

As described above, eye movement and mental

conditions are correlated. However, correlations

between the chaos of eye movement and mental

conditions have not been sufficiently examined.

Murata & Matsuura (2015) reported that LLE of eye

movement when conducting a visual search tended to

increase as the stimulus became more complicated.

Moreover, Yoshida & Suzuki(2019) measured LLE

of eye movement in university students with high or

low depression to examine correlations between LLE

of eye movement and depression, indicating the

maximum value of LLE of eye movement became

higher when students had higher depression.

Based on the above, it is suggested that shoulder

stiffness and depression, as well as the chaos of eye

movement, might be correlated. This study examined

changes in the chaos of eye movement accompanied

by changes in depression by treating shoulder

stiffness.

2 METHODS

The Japanese version of the Carroll Rating Scale for

Depression (Shima, Shikano, Kitamura, & Asai

,1985) and the Katakori scale (Tanaka & Suzuki,

2012) were administered to university students in

Changes in a Chaotic Fluctuation of Eye Movement Produced by Stiff Shoulder Treatment

173

Tokyo (N=490) from July to November in 2011. The

results indicated a mean score of 13.08 (SD=7.24).

Participants scoring over 1SD from the mean score

having high depression and shoulder stiffness were

included in the intervention group (n=12) and provided

stretching intervention. The control group included

participants having high depression and shoulder

stiffness (n = 11), but they were not provided with the

stretching intervention. Moreover, participants scoring

lower than 1SD from the mean score having low

depression and no shoulder stiffness were included in

the Low group (n =11).

2.1 Equipment, Materials,

Psychological Scales

Eye Link CL Illuminator TT-890 (SR Research Ltd.)

was used to measure eye movements. In this system,

the direction of the eyeball is recorded by using an

infrared camera, and blinks, saccades, the pupilar

diameter, the amplitude of the gaze point in the vertical

and horizontal directions are measured in real-time.

The non-contact remote model of this equipment was

used to reduce participants’ burden. The distance

between the camera and a participant was 70cm. A

height-adjustable chair was used to adjust the eye

height of the participants to the center of the monitor.

The PC monitor was 31.0cm height x 45.0cm wide. A

16mm lens was used for remote photography. The

sampling rate was 500Hz for one eye. Shoulder

stiffness was treated using the Stretch Pole EX (LPN

Corporation) (Figure 1).

Figure 1: Stretch Pole EX (LPN Corporation) (Stretch Pole

Official Site(http://stretchpole.com/)).

2.1.1 The Japanese Version of the Carroll

Rating Scale for Depression

This scale was developed by Shima, Shikano,

Kitamura, & Asai (1985) to assess depressive mood

and includes 52 items. Participants are required to

respond regarding their recent condition using a two-

point scale consisting of “Yes” or “No.” This scale

corresponds to the Hamilton Rating Scale for

Depression (HRSD), which is used to assess the

severity of depression in clinical psychiatry. Therefore,

the consistency with the clinical diagnosis can be easily

established when clinical samples are included as

research subjects. The total score on this scale is 0-52

points. Shima, Shikano, Kitamura, & Asai (1985)

reported that the mean score of a normal control group

on the scale was 6.7 (SD=6.0). A score of 17 is

recommended as the cut-off point for identifying

depression..

2.2 Procedures

1. Eye movement measurement devices and a PC

monitor were set up in a psychology laboratory (a

dark room).

2. Psychological tests and the Katakori scale were

administered (the results were excluded from

analysis in this study).

3. The experimenter assessed the subjective shoulder

stiffnrss(Katakori) of participants with a physical

therapist.

4. The dominant eye was selected. Participants were

requested to make a circle with their fingers and look

at the object with both eyes so that the object is

positioned at the center of the circle. Next, they

closed one eye, and then the other eye. The eye that

could observe the object equally well as when using

both eyes was decided as the dominant eye.

5. After conducting the calibration and validating the

use of the eye movement measurement devices,

participants were requested to fixate a black circle

with a diameter of 18cm on a white drawing paper

for 180 seconds, which was adjusted to the size of

the PC monitor.

6. The experimental group exercised using the Stretch

Pole EX, by referring to basic techniques of its use,

and relaxation methods for the neck and shoulders,

recommended by the official site of the stretch pole.

They conduct breast exercise, diagonal exercise,

floor polishing exercise, scapular exercise, arm

abduction exercise, small fluctuation exercise,

sidelong glance exercise, and neck flexion exercise

(Figure2) for about 10 minutes until they felt

comfortable and felt no pain.

7. Psychological tests and the Katakori scale were

administered (the results were excluded from the

analysis of this study).

8. The experimenter assessed the subjective Katakori

of the participants with a physical therapist.

The control group and the Low group conducted

the procedure 7 after 5.

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Figure 2: Examples of exercise. (Stretch Pole Official

Blog(https://stretchpole-blog.com/stretchpole/stretchpole-

use).

2.3 Ethical Considerations

The experiment was conducted after being examined

for research ethics and getting the approval of the first

author’s research institution. Participants were

instructed that they could quit the experiment even in

the middle for any reasons and that they would incur

no disadvantages for not responding, quitting the

experiment, or based on the content of their

responses. Moreover, they were explained that the

experimental results would be statistically processed

and used only for academic purposes and that the data

would be stored in a USB memory stick that has been

encrypted. They were also told that no individuals

would be identified from the data. The participated

took part in the experiment after giving their consent

to the explanation.

3 RESULTS

Eyeball positions data measured at 500Hz for 180

seconds were analyzed. Since LLE of eye movement

is affected by blinks data under 5SD, and over 5SD

from the mean value of eye movement data were

excluded from the analysis. The calculation method

of LLE was referred to Pham, Thang, Oyama-Higa,

Nguyen, Saji & Sugiyama(2013). Table1 shows

fundamental statistics of LLE of eye movement in

high and low depression groups. The mean eye

movement LLE value in the high depression groups

(intervention group and control group) was 15.63

(SD=5.67), whereas in the low depression group was

17.96 (SD=8.82). The mean standard deviation value

of eye movement LLE in the high depression groups

was 9.08 (SD=6.37), whereas that in the low

depression group was 5.46 (SD=4.00). Table 2 shows

fundamental LLE statistics of intervention and

control groups for the high depression groups. The

mean eye movement LLE value of the intervention

group was 15.81 (SD=6.76), whereas that of the

control group was 15.44 (SD=4.16). The mean

standard deviation value of eye movement LLE in the

intervention group was 13.00 (SD=6.58), whereas, in

the control group, it was 4.80 (SD=1.57). The mean

eye movement LLE value of the intervention group

after the intervention was 5.72 (SD=4.54), and the

mean standard deviation value of eye movement LLE

was 5.31 (SD=2.64).

Table 1: Fundamental statistics of LLE of eye movement in high and low depression groups.

Table 2: Fundamental LLE statistics of intervention and control groups for the high depression groups.

Mean SD SE 95%CI Lower 95%CI Upper

LLE of eye movement(pre) 15.63 5.67 1.18 13.18 18.09

Ðeviation of LLE of eye movement(pre) 9.08 6.37 1.33 6.32 11.83

Mean SD SE 95%CI Lower 95%CI Upper

LLE of eye movement(pre) 17.96 8.82 2.66 12.03 23.89

Ðeviation of LLE of eye movement(pre) 5.46 4.00 1.21 2.77 8.15

High depression group(N=23)

Low depression groups(N=11)

Mean SD SE 95%CI Lower 95%CI Upper

LLE of eye movement(pre) 15.81 6.76 1.95 11.52 20.11

Deviation of LLE of eye movement(pre) 13.00 6.58 1.90 8.81 17.18

LLE of eye movement(post) 5.72 4.54 1.37 2.67 8.77

Deviation of LLE of eye movement(post) 5.31 2.64 0.80 3.53 7.08

Mean SD SE 95%CI Lower 95%CI Upper

LLE of eye movement(pre) 15.44 4.16 1.26 12.64 18.24

Deviation of LLE of eye movement(pre) 4.80 1.57 0.47 3.75 5.86

Intervention group(N=12)

Control group(N=11)

Changes in a Chaotic Fluctuation of Eye Movement Produced by Stiff Shoulder Treatment

175

3.1 Analysis of Variance (ANOVA)

based on the Depression Level

An ANOVA was conducted between high and low

depression groups to examine for significant

differences in eye movement LLE and the standard

deviation of the LLE based on the depression level.

Results indicated no significant difference in the eye

movement LLE (F(1,32)=0.81, p=0.38,η²=0.03),

although the effect size η² showed a small effect. On

the other hand, the standard deviation of the eye

movement LLE in the high depression group was

higher than in the low depression group

(F(1,32)=2.813, p=0.10,η²=0.08), and the effect size

η² showed a mid-sized effect. The above results

indicated that LLE of eye movements tended to be

low when the depression level was high, and the

degree of change in eye movement LLE was larger.

3.2 ANOVA of Pre and

Post-intervention Changes in Eye

Movement LLE

An ANOVA was conducted to examine significant

differences in eye movement LLE and the standard

deviation of LLE between pre and post-intervention.

The results indicated that eye movement LLE

decreased significantly after the intervention

(F(1,11)=18.61,p=0.00,η²=0.63), with a large effect

size η² (Figure3). Regarding the standard deviation of

LLE of eye movement, it also significantly decreased

after the intervention (F(1.11)=9.582,

p=0.01,η²=0.47), with a large effect size η² (Figure4).

Based on the results above, it was indicated that LLE

of eye movement and the amount of the change of

LLE of eye movement decreased by the intervention..

4 DISCUSSION

The results of the experiment indicated that eye

movement LLE changed more significantly when the

depression level was high. Moreover, LLE and the

degree of change in LLE decreased after receiving

treatment for the stiff shoulder. It is suggested that the

chaotic fluctuation of eye movement might decrease

when depression improved, i.e., in people with low

depression.

Saime et al. (2015) reported that the frontal and

parietal lobes of patients with depression tended to be

highly chaotic. On the other hand, Oyama (2012)

reported less chaotic tendencies in the finger

plethysmogram of patients with depression. On the

Figure 3: ANOVA of pre and post-intervention changes in

eye movement LLE.

Figure 4: ANOVA of pre and post-intervention changes in

deviation eye movement LLE.

other hand, for respiration Yeragani, Radhakrishna,

Tancer,& uhde(2002) reported that the LLE for

respiration in panic disorder patients in a standing

position was higher than with the healthy control

group, while Yeragani, Rao, Tancer,&

Uhde(2004)pointed out that serotonin reuptake

inhibitors are effective at decreasing overly-high LLE

in panic disorder patients, indicative of differences

between the findings of preceding studies.

Sometimes, the LLE of healthy participants is lower

than patients with depression. Therefore, the results

require careful discussion. Participants in this study

were ordinary students, and they were classified

based only on the level of depression. On the other

hand, the study by Oyama (2012) included patients

with depression. Comparing the results of the current

study with Oyama (2012) suggests that the chaotic

tendencies in the LLE of biological signals might

increase in people with depressive tendencies.

However, chaotic tendencies might decrease when a

person is diagnosed as depressed (i.e., a high level of

depression). The above discussion is based on

speculation because Saime et al. (2015) also dealt

with patients with depression. Further analysis is

required because sufficient chaos analysis of

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biological signals such as eye movement has not been

conducted.

As described above, shoulder stiffness is regarded

as a physical symptom caused by psychological

factors. According to Takaguchi & Ishozima (1991),

when administering Dosulepin (a medication for

depression) to participants in depressed conditions

with shoulder stiffness, the shoulder stiffness

improved in 13 (52%) participants, which is close to

the efficacy rate for shoulder treatment at that time.

Aoyagi, Suganuma, Kaneko, & Shinbo (2019)

indicated that students with neurotic tendencies

complain not only about psychological symptoms but

also physical symptoms such as headache, fatigue,

and the feeling of suffocation, among others,

suggesting that psychological health might affect the

body and appear as physical symptoms including

shoulder stiffness. Considering such psychosomatic

correlations, although speculative, this study suggests

the possibility that psychological health might be

assessed and treated based on physical symptoms as

suggested by Sharifa et al. (2013), including

depression screening by measuring eye movements.

In the future, treatment and diagnosis might improve

by examining how depression or shoulder stiffness is

affected by moving or not moving the eyeballs

according to certain rules.

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