## 4 Discussion  
### Effects of the ELF-EF on SC  
In the present study, the effects of a 9000 V ELF-EF treatment on the number of SC-SFs were observed, which was significantly reduced after 20 min of treatment. The simulated induced current was low (below 6 mA/m\({}^{2}\)), and it was revealed that a low-intensity ELF-EF can modulate autonomic activity, as reflected by SC-SFs. The SCL, on the other hand, was not altered by the ELF-EF treatment (Figure 3). SC represents sweating with multifunctional significance, as described in the Methods Section. Among the SC indices, the SCL measures the absolute level of conductance due to the presence of sodium chloride ions in the skin and reflects the total amount of sweat. In the present study, the total amount of sweating was not affected by the ELF-EF treatment. Sweating is affected by various indices, including temperature, metabolism, circulation, and psychological status, leading to changes in the SCL [12; 13; 14]. It was assumed that the low-intensity ELF-EF used in the present study did not modify the sweat gland activity as a whole.  
SC-SFs are intimately related to psychological status, including anxiety and tension [15]. The changes in SC-SFs in the present study may have been evaluated as a reduction in anxiety and tension, which can be a basis for the use of low-intensity ELF-EF treatment applied for stress management in healthcare by reducing sympathetic activity and promoting relaxation.  
SC-SFs are a type of skin conductance response without obvious external triggering stimuli. The response of skin conductance to external stimuli, such as tones, has been utilized to analyze arousal, attention, and habituation in various mental disorders, including schizophrenia [24]. Central noradrenergic activity is involved in controlling the skin conductance response through the sympathetic pathway [24]. Noradrenergic neuronal activity is known to be related to changes in the arousal level [26]. The present results for SC-SFs may have been generated by the effects of the ELF-EF on noradrenergic activity. Future studies with catecholamine measurement are necessary to assess this possibility.  
In the present study, the SCL in the sham session was greater than that in the treatment session both before and after the treatment (Figure 3). The SCL can be affected by various factors, including temperature, metabolism, and circulation [12; 13; 14]; the difference in the SCL found between the EF and sham sessions may be explained by these conditions on the experimental days. It is suggested that the SCL itself is influenced by various conditions other than psychological factors.  
The present study also showed that the number of SC-SFs and the SCL were significantly correlated both before and after the EF treatment (Figure 4). Since a correlation was not observed after the sham treatment, the persistence of the correlation between SCFs and the SCL may have been a result of the effects of the ELF-EF treatment. A study with a larger sample size will be necessary to assess this issue. After the EF treatment, the number of SCFs was reduced without changes in the SCL, and the correlation between these two parameters persisted. This phenomenon can be explained by the effects of the EF treatment on sweating mainly being related to psychological status but not to the control of temperature and metabolism. The measurement of both the SCL and SC-SFs can reveal multiple aspects of the function of sweat.