Clothing pressure alters brain wave activity in the occipital and parietal lobes

2.1 Subjects

A total of 10 young females with similar body shapes were chosen as the subject, and the feature data of their body shapes should fall within the pre-defined range. In order to ensure consistency with subsequent brain wave experiment, the subjects must be as healthy as required in the brain wave test. The range of the physical characteristics is shown in Table 1.

2.2 Experimental material

A girdle (Figure 1) consisting of nylon and spandex was utilized in the study (Table 2). The girdle was designed to provide common girdle functions including breast support, waist narrowing, abdomen flattening and hourglass body curvature. Girdles size S (waist: 61-67cm; circumference 83-93) was used (Table 2).

Figure 1

The girdle in experiment

The girdle consists of a two-layer elastic mesh distributed bilaterally, two small non-elastic sections located along the waist with one larger elastic component, an piping, and a layer of non-elastic fabric in the middle of the two layers of elastic cloth. The girdle has hooks on both sides of the non-elastic part. The piping acts as a support and separates the fabric in the various girdle sections to produce a smooth curved appearance along the waist.

2.3 Experimental equipment

The U.S. Neuroscan EEG/ERPS NuAmps, portable 40-electrode digital DC, and EEG/ERPs amplifier were used to record brain waves. Five

functional regions of the brain were defined: the frontal lobe region F (FP1, FP2, F3, F4, FZ, F7, F8, FT7, FC3, FCZ, FC4, FT8), lobes temporalis region T (T3, T4, TP7, TP8, P7, P8), central region C (C3, CZ, C4), parietal region (P3, PZ, P4, CP3, CPZ, CP4), and the occipital region O (O1, O2, OZ). The electrodes were organized along these regions as shown in Figure 2.

Figure 2

Measurement placement

2.4 Experimental conditions

Data collection was conducted in the brain wave laboratory at a constant temperature （25±2℃) and moisture (65±2℃). The laboratory was effectively shielded from electromagnetic waves. Participants had sufficient sleep the night before testing, and cleaned their hair, did not apply oil or fat substances, and did not perform violent exercises or undergo emotional fluctuations prior to testing. During the experiment, the participants wore the girdle (without a bra) in order to eliminate interference from other clothes.

2.5 Experimental process

The process of brain wave measurement is shown in Table 3. Brainwaves for participants were recorded with and without the girdle with the electrode set at different positions. Prior to each recording session, the participants were allowed to relax by sitting quietly and listening to light music for 30 minutes. Brainwaves were then recorded for 1 minute. The subjects were not permitted to do anything irrelevant to the experiment. Prior to recording sessions, the electrode cat was connected to the amplifier and specific parameters were set.

During data recording, the electric resistance was maintained at a level under 5 KW and the digital sampling rate was 1000Hz. The average brainwave of the electrodes when they are placed above the mastoid bone was used as a reference brainwave. A set of brain wave data was collected beforehand to determine that the baseline and electrodes were correctly set up.

2.6 Data processing and analysis

Power spectrum analysis was adopted for frequency-domain processing of the brain wave data. Relative brainwave spectrum was used as a metric of brain wave rhythm in order to compare brainwave spectrums across different individuals. The relative power is defined as the ratio between the absolute power of a specific frequency band and the total power of all frequency bands.

The brain wave data from 30 electrodes was pre-processed by implementing the following steps: electrooculographic integration, DC correction, electrooculographic elimination, baseline correction, filtering, MARK-free brain wave fragmentation (511ms-long brain wave signal with 512 sampling points), and frequency-domain overlapped averaging (Hanning window function). The pre-processed data then underwent offline analysis to generate brain wave power data across four frequency bands. After which, SPSS 15.0 was utilized to analyze the relative power of the a wave under each condition.

3.1 Impact of clothing pressure on the a wave power

To determine whether α wave power can be used as a reliable measure for clothing pressure comfort, we examined changes in power in 10 female participants with and without a girdle using an electrode located along the parietal region (point P3). Data from subject B is shown to illustrate data analysis results.

As shown for subject B, the maximum power spectrum of the α wave significantly decreases when pressure is applied to the waist (Figure 3; 0.6mV2) when compared to when no pressure is applied (Figure 4; 2mV2), indicating that the a wave intensity decreases when pressure is applied to the waist.

Figure 3

Power spectrum of subject B with the girdle

Figure 4

Power spectrum of subject B without the girdle

Energy analysis of the a wave power spectrum revealed that wave length intensity was significantly different for participants when the girdle was worn when compared to when the girdle was off (Table 4; P≤0.01). Taken together, the data suggests that α wave intensity significantly differs based on clothing pressure.

3.2 Impact of clothing pressure on a wave power under different electrode locations

To determine if changes in α wave intensity are impacted by the location of the electrode, we compared α wave intensity recorded at 30 different locations when participants were and were not wearing a girdle. Duncan analysis of

homogeneous subsets, where the electrode location was defined as a subgroup, revealed that the 30 tested electrode locations could be grouped into four subsets: subset 1 in the occipital and parietal regions (CP3, PZ, P3, O1, O2, OZ), subset 2 in the frontal, central and parietal regions (FC3, FZ, F7, FT7 , FCZ, CPZ, C3, F3, CZ), subset 3 in the frontal and parietal regions (FT8, FC4, CP4 , FP2, F4, P4, FP1, F8), and subset 4 in the temporal region (C4, P8, T4, TP8, T3, TP7, P7) with the exception of location C4 located in the central region. These findings indicate that the a wave power spectrum recorded from electrodes in locations within the same subset were similar. In Figure 5 using different red to show different wave power, the darker color means the higher a wave power. This figure clearly indicates that clothing pressure exerted by wearing a girdle mostly stimulates the parietal and occipital regions.

Figure 5

a wave power spectrum of 30 electrodes distribution map

3.3 Individual difference between subjects

To determine if electrode locations are similar among individuals, the results of the Duncan analysis of homogeneous subsets for each participant was compared. Data analysis showed that the grouping of locations with similar differences in α wave intensities for clothing state (wearing or not wearing girdle) differs for each individual. For example, Duncan homogenous subset analysis of brain wave data recorded from subject A revealed that the 30 electrode locations could be classified into 6

subsets: subset 1 in the occipital region （CP3, CPZ, CP4 , O1, O2, OZ）, subset 2 in the parietal and frontal regions （P3, PZ, P4, F3, FZ, F4), subset 3 along the frontal region （FP1, FP2, F7, F8, FT7）, subset 4 in the frontal lobe region （FC3, FCZ, FC4, FT8）, subset 5 along the central region （T3, C4, C3, CZ, TP7）and subset 6 within the temporal region. （T4, TP8, P7, P8）with some exceptions (T3 of subset 5 was located in the temporal region). However, in both subjects A and B, electrodes recording similar α wave intensities were located in close proximity to each other. In order of descending differences in a wave spectral energy between wearing and not wearing a girdle, the subset recording location options for the subsets of electrode locations were the occipital, parietal, frontal, central, and temporal regions.