Background: Muscle fatigue has been known to influence brain activity, but very little is known about how cortical centers respond to muscle fatigue. Objective: This study was conducted to investigate the effects of muscle contraction and fatigue induced by two different percents of maximal voluntary contraction (MVC) on Electroencephalography (EEG) signals. Material and Methods: In this quasi-experimental study, EEG signals were recorded from twenty-one healthy human subjects during three phases (rest, pre fatigue and post fatigue) contraction of Adductor pollicis muscle (APM) at 30% and 70% MVC. The mean powers of EEG bands (alpha, beta and gamma) were computed offline in the frequency domain. Results: None of the three phases with each percent of MVC revealed significant differences for all bands (p>0. 05). Comparison of two hemispheres showed that right hemisphere gamma band activity was enhanced during pre-fatigue state at 30% MVC (p= 0. 042) and post-fatigue state at 70% MVC (p= 0. 028). Right hemisphere beta band activity also increased prominently at 70% MVC in post-fatigue condition (p = 0. 030). Conclusion: These results suggest muscle contraction and fatigue at 30% and 70% MVC have no significant effect on EEG activity, but the trends of beta and gamma band activities are almost similar in each percent of 30% and 70% MVC. Right brain hemisphere shows more activity than left hemisphere in beta and gamma rhythm after fatigue state at 70% MVC.

Introduction: The purpose of this study was to compare laterality in the asymmetric transfer of strength and velocity in children with 11 to 13 years of age.Materials and Methods: In this semi-empirical study, 28 students (mean age, 11.6±0.62 years), who were recruited from junior high schools of Kashmar, Iran, were divided into two groups of 14 each. One group practiced strength training with the right hand and speed training with the left hand and in another group the usage of hands were reversed, meaning that strength training was practiced with the left hand and speed training with the right one. Participants had practiced for 3 sessions a week over a 4-week period.Results: The results of one-way ANOVA showed that there was significant difference in magnitude of strength transfer between the two groups. The magnitude of strength transfer from the left hand to right one was significantly greater than the vise versa (P=0.029). However in “Velocity” variable, there was no significant difference.Conclusion: According to results of this study and specialization of right hemisphere in control of strength, it seems that the magnitude of strength transfer from left hand to right hand is greater than the opposite direction.

Background/Objectives: The structural changes of brain (cerebral and lateral ventricles volumes) in schizophrenia are controversial. This is partly due to the heterogenicity of the schizophrenia subtypes. In this study we compared the changes in the volumes of cerebral hemispheres and lateral ventricles in 3 subtypes of schizophrenia (paranoid, undifferentiated and residual) with normal controls.Materials and Methods: 29 schizophrenia patients (21 men, 8 women) of 3 subtypes of paranoid, undifferentiated, and residual (according to DMS-IV criteria) were compared with 29 age- and gender-matched normal controls. All cases and controls underwent 3-D brain MRI of full coronal series, 1.5 mm slices without interslice gaps. The hemispheres and lateral ventricles were outlined and their volumes were calculated using Cavalieri’s Principle. The results were statistically analyzed.Results: The brain was slightly but insignificantly smaller in the schizophrenia patients. Only the residual subtype showed a significant reduction in cerebral and hemispheric volumes than controls (p<0.05). The volumes of right and left ventricle, separately and together were larger than controls (p<0.03). The ventricle-to-brain ratios (VBRs) were greater in the cases (p<0.05). The paranoid subtype patients had larger ventricles and VBRs than controls (p<0.05). The lateral ventricle volumes and VBRs in the undifferentiated subtype were similar to the controls. In the residual subtypes, the ventricular volumes were similar to and the VBRs were larger than controls (p<0.05).Conclusion: Schizophrenia is a heterogeneous disorder regarding its symptoms and neuropathological changes. The patterns of change in the cerebral and ventricular volumes differed in the studied 3 subtypes.

Narrow, rapidly flowing currents of air located near the tropopause are known as jet streams. These jets, often found nearly girdling the globe while exhibiting large meridional meanders, are among the most ubiquitous structural characteristics of Earth’s atmosphere and are known to play a substantial role in the production of sensible weather in the mid-latitudes. Jet streams are classified into two different types subtropical jet and polar-front jet streams. Subtropical jets are driven by angular momentum transport from the tropics and are centered at the poleward boundaries of the Hadley cell and polar-front jets are driven by baroclinic eddies and are associated with weather and climate events, such as precipitation and cold wave processes.To study whether jet streams have been changing in the past decades, we used the historical data of NCEP/NCAR from the National Centers for Environmental Protection and the National Center for Atmospheric Research, covering 1948 to 2023.We have used the daily means of u, v components, temperature and geopotential height, at 6 levels from 400 to 100 hPa and daily means temperature at 4 levels from 1000 to 700 hPa.In this paper, we firstly calculated the wind speed index, pressure index and latitude index that were defined by Archer and Caldeira (2008) to characterize the strength, the pressure level, and the latitudinal position of a jet stream, respectively. Then after that the variability of the characteristics of jet streams of both hemispheres in warm and cold seasons were investigated.In addition, the temperature trend in the upper and lower troposphere was determined by calculating the average seasonal temperatures over latitudinal zones 0°-15°, 15°-30°, 30°-45°, 45°-60°, 60°-75°, 75°-90° in northern and southern hemisphere at upper levels of 400, 300, 250, 200, 150, 100 hPa and lower levels of 1000, 925, 850, 700 hPa.We found that, in general, the jet streams have moved poleward in both hemispheres so that the shift of subtropical jets in the northern hemisphere was 0.061 (0.019) °/decade in DJF poleward (JJA) and in the southern hemisphere was 0.307 (0.223) °/decade in DJF (JJA) for 1948-2023. Also in the southern hemisphere, the subtropical jet in winter and summer is weakening but the polar front jet is strengthening. In the northern hemisphere, in both warm and cold seasons the trend of wind speed is increasing in the poleward side of the jet axis, and is decreasing in the southern side of its axis, while the trend of the maximum wind speed is upward. One of the important factors of these changes can be related to the upward temperature trend in the tropical and subtropical regions of both hemispheres.In this statistical period, the smallness of the slope of the zonal mean of seasonal temperature trend of the lower levels of the tropical region, compared to the slope of the average temperature trend of the upper levels of the subtropical region, has caused strengthening of the Hadley cell convection which is less than the weakening of its meridional circulation range. This could be one of the factors that lowered the trend of the jet streams speed in both hemispheres. Also, the results show that the mass-flux weighted pressure in the DJF season is minimum around the equator and is minimum in the JJA season around the orbit of 12°N from the west of Mauritania to the southeast of China.

Purpose: This study is designed to determine the sexual dimorphism pattern in volume of the cerebral hemispheres and lateral ventricles in schizophrenia using magnetic resonance imaging (MRI) and to compare it with normal sexual dimorphism pattern in healthy brains.Materials and Methods: This study is performed on 29 healthy volunteers (21 males, 8 females) and 29 patients suffered from schizophrenia (21 males, 8 females) after exact psychiatric examinations based on DSM-IV criteria. Males and females in each group were in the same age. The brains of patients and controls serially sectioned in full coronal series of 1.5 mm thickness by a 1.5 tesla MRI. The volumes of whole brain, hemispheres, and lateral ventricles and the ventricular - Brain Ratios (VBRs) were estimated by Cavalieri's principle. Finally the sex difference for each parameter was evaluated by t-student and non – parametrical Mann- Whitney tests.Results: The volumes of the whole brain and each of its hemispheres were significantly smaller in healthy females than those males (P<0.005). The volume of the right ventricle was also smaller in healthy females than those males (P<0.05). The volume of both lateral ventricles was tended to be smaller in females than males (0.05<P <0.1). However, the volume of the left ventricle was similar between two sexes in healthy controls. In schizophrenics, the volume of the whole brain and each of its hemispheres were significantly smaller in females than males (P < 0.005), but there were not any significant sex difference in ventricular volumes. VBRs were similar between two sexes in healthy controls. In schizophrenics, the- VBRL and the YBRW were significantly higher in females than males.Conclusion: The lateral ventricular volumes, particularly in left, are larger in schizophrenic females than those males. On the other word, since the VBRL and the VBRw are higher in schizophrenic females than those males, it is concluded that the internal cerebral atrophy in schizophrenia is more severe in females than males, particularly in the left hemisphere.

Background and Aim: One of the most important capabilities of central auditory nervous system is dichotic listening processing, which undergoes changes with aging, similar to peripheral hearing. The results of the studies about comparison of functional asymmetry of cerebral hemispheres between musician and non-musician elderlies reveal advantages of musician old age in dichotic listening processing. In the present investigation, functional asymmetry of cerebral hemispheres is investigated in dichotic listening musician and non-musician elderlies with normal hearing using dichotic digit test.Material and Methods: The current cross-sectional study was performed on 40 right-handed musician (N=20) and non-musician (N=20) elderlies aged 60 to 80 years with normal hearing using the Persian version of the dichotic digit test. Data was analyzed running independent t test and man-whitny test. Finally, the results of right and left ears were compared in Non-Forced Attention (NF), Forced Right (FR), and Forced Left (FL) attention conditions.Results: Comparison of dichotic digit test results in divided attention condition showed significant difference between the two groups (p-value<0/001). Also, in FR and especially in FL conditions, there were significant differences for correct scores in both ears between musician and non-musician elderlies (p-value=0/001).Conclusion: The results of the present study confirmed better function in musician elderlies compared with non-musician elderlies in divided attention and competitive environment particularly in FL attention condition. In fact, musician elderlies' desire to acquire information through both ears in noisy places, unlike their non-musician counterparts. Finally, musician elderlies showed lower hemispheric asymmetries with higher scores obtained in dichotic digit test.