Introduction:

  In August 1945, Japan's national system changed from an imperial system to democracy, forcing a change in the behavior of the Japanese people. The following considerations were made from the perspective that changes in national systems may affect the growth of cognitive function. In the imperial dictatorship system, the prefrontal cortex function, which allows people to make decisions and act on their own, was not allowed to activate, and subordinates from upper to lower were at the center of action in Japan. After the country was forced to change to democracy, the freedom of individual action that demonstrated the functions of the prefrontal cortex came to be respected. In other words, the norms of behavior have changed 180 degrees.

　Japanese people who encountered the changes described above were shocked in their thinking process. I thought that this shock might have affected the development of the prefrontal cortex in elementary school students who were 6 to 12 year’s old, through previous many research ^1-６). So, I conducted an investigation using the CKPT, which largely reflects the function of the prefrontal cortex⁷⁾.

Methods

1. CKPT

  CKPT (Japanese version of CWPT) was devised in 2003 as a test method that can classify cognitive function at PCSD（Preclinical Stage of Dementia）^8）before the onset of dementia. For the first time in 2019, it was announced at an international conference^9） that there is a correlation with WCST as criterion-related validity, sensitivity = 1, specificity = 0.963, and in the same year it was published as a paper in the HOSA Journal of Alzheimer's and Neurodegenerative Disease¹⁰⁾. Furthermore, we presented a study that derived diagnostic criteria from large-scale data of 1325 people using CKPT at an international conference in 2019¹¹⁾, and in 2020 we published the diagnostic criteria for CKPT in the same journal¹²⁾. Since then, we has published research results such as the results of using CKPT on healthy elderly people¹³⁾ and a report on comparing the normality of large-scale data over 15 years¹⁴⁾.

The feature of CWPT is described following:

When a subject encounters color words (Fig.1) picked-out reading the story, he determines whether the meaning matches the printed color of the color word and picks-out as many color words as possible, by marking 〇 (match) and × (mismatch). One feature is a test that measures work ability and attention distribution ability, and the other feature is a test that measures memory ability of listening to questions (Fig.2) about the episodes written in the story without looking at the story after 2 minutes. The score of CWPT named Index1 is a product of them. In other words, it can be said to be a test that not only reflects the function of the frontal lobe, but also can comprehensively judge a person's cognitive function, including the ability to understand and execute complex test methods.

When MMSE¹⁵⁾, CDR¹⁶⁾, FAB¹⁷⁾, etc., which are conventionally known as neuropsychological tests for dementia, are applied to people before MCI, the histograms of those scores are biased towards high scores (Fig. 3). On the other hand, the CKPT score (Index 1) shows a normal distribution, so a feature of this test is that it is possible to classify cognitive function using the mean value, mean value ± SD, and mean value ±1.5SD (Fig.4).​

Fig.1 Sample of CWPT（Story）

Fig.2 Sample of CWPT（Questions）

Fig.3 The histogram of MMSE, FAB, etc. before MCI

Fig.4 The histogram of CKPT before MCI
A:Excellent, B:Good, C and D:Normal, E:Slight disorder, F:Docter’s diagnosis is needed

2. Subjects

　The large-scale data of 2555 subjects that had already been collected during about 10 years was divided into three groups shown on Table 1. They are B:1st to 6th grade elementary school age groups (6 to 11 years old), A:older age groups, and C:younger age groups on August 15, 1945. A comparative study will be conducted by age group. Table 1 shows the entire group.　Table 2 shows the numbers of grouping subjects from large-scale data according to the rules in Table 1. The vertical items indicate the age when the test was taken for each gender, and the numbers indicate the number of subjects in each group.

Table1 Subjects grouping by age in 1945

2. Analysis

 In past research, we divided large-scale data by gender and age and tested the histogram of each CKPT score (Index 1), and it was found that the results showed normality¹²⁾. In this research, I decided to consider the same procedure for each group and taken ages on Table 2.

Table2 Subjects in each group
Total: 2557 subjects

Results

Table 3 shows normality examination of CKPT Score using Shapiro-Wilk test. If significance p value is 0.05 or more, it follows normal distribution. If significance p value is less than 0.05, it is given a yellow line. It is found that every condition has normal distribution for male, but there are tree conditions which don’t have normal distribution. They are group A and 80’s, group B and 80’s, and group C and 80’s.

Table3 Normality examination of CKPT Score using Shapiro-Wilk test

If significance p value is 0.05 or more, it follows normal distribution.

If significance p value is less than 0.05, it is given a yellow line.

Considerations

1. The fact that male showed a normal distribution under all conditions suggests that the development of cognitive functions in all male was unperturbed by changes in the national system and adapted to them. We speculate that the reason was that all of the male were forced to focus on finding food to survive as they suffered from extreme starvation.
2. Previous research has shown that for female, the histogram by age shows a normal distribution¹²⁾. However, in order to examine the effects of changes in the national system, we divided into groups before and after ages 6 to 12, who were elementary school students at the time of the change in the national system, and found that in all groups, those in their 80s did not show a normal distribution. It means that there was a dispersion. Although further analysis is required, these results seem to suggest that there are factors that make female more sensitive to changes in the national system than male.

Summerly

Previous studies have investigated the development of the frontal lobe from multiple angles, showing that it is most pronounced between the ages of 8 and 15, but we attempted to verify this using the CKPT, which strongly reflects the functions of the frontal lobe. Specifically, we assumed that development might be hindered by changes in Japan's national system. As shown in the results, men were not affected, but women became affected.

It is said that the frontal lobe continues to develop after the age of 8 to 15. This analysis shows that even if a large shock is given to children between the ages of 6 and 12, when their frontal lobes are still developing, they have the ability to overcome them.