Studies on Brain Function and Physiology - Essay Example

Studying to find out how the brain works or functions has long been a major consideration in the field of biopsychology. This is the field that deals with application of neurobiology to the study of the physiological, genetic, and developmental mechanisms of behavior in humans. It has long been known that the two hemispheres of the brain are anatomically identical, separated only by a fibrous commissural band (corpus callosum) that is responsible for communication between the two hemispheres. However, studies on brain function and physiology show that the two hemispheres are in fact functionally different. In light of this fact, it has also been noted that one, more often the left hemisphere is dominant (left hemisphere in about 95% of right handed individuals and 60% of left handed individuals). Furthermore, the left hemisphere takes charge of logical processes and language (S. Knecht, 2000) (Speech, song, and writing), and the right controls perception of rhythm, spatial-relation skills, and abstract or intuitive thought as well as emotion (though abstract). These functions have trivially been tagged as feminine. It has also been long known that specific areas of the brain in the dominant hemisphere handle specific tasks. They have been subdivided into ‘areas 1-51’ according to Brodmann’s classification (Brodmanns map of cytoarchitectonics). An example is the 1) Auditory areas: primary, 41 and secondary 22, 42. Interesting research, such as the “split brain studies” on these areas also lends evidence to left-right hemisphere dominance. 2) Visual areas: 17, 18 primary visual 3) Language and speech: Wernicke’s area- 22, Broca’s area-44,45 (breach., 1987) There are varying results however, especially concerning the left-brain and right-brain hemisphere activation. Concerning this, more relevant studies are necessary to ensure confirmation of the appropriate findings. The purpose of this research was to establish whether there actually exists a difference in the functional organization of the brain for language and visual spatial tasks between males and females. The research design was mixed. The sampling method was random with the following layout; Males and hemisphere differences: For the language task and spatial task: Paired t-test for alpha waves Paired t-test for theta waves Females and hemisphere differences For the language task and spatial task Paired t-test for alpha waves Paired t-test for theta waves Sex differences for language task and spatial tasks ANOVA Main effects: Sex Hemisphere Interaction effect Sex and hemisphere Post hoc t-test The hypotheses for the research were; Hypothesis 1: There will be a significant difference in left and right hemisphere activation for the language tasks for males Hypothesis 2: There will be a significant difference in left and right hemisphere activation for the spatial tasks for males Hypothesis 3: There will be a significant difference in left and right hemisphere activation for the language tasks for females Hypothesis 4: There will be a significant difference in left and right hemisphere activation for the spatial tasks for females Hypothesis 5: There will be a significant difference between males and females for the language task Hypothesis 6: There will be a significant difference between males and females for the spatial task The results of the study support the idea that males may have left lateralized dominance over their female counterparts, and females may have that level of dominance particularly somewhere in the right hemisphere of the brain. This further suggests that Verbal and visuospatial abilities are believed to be typically sub-served by different cerebral hemispheres: the left hemisphere for the former and the right hemisphere for the latter (Andrew J.O. Whitehouse., 2009) which could be due to lateralization or specialized function of each hemisphere. Keywords: EEG, right-brain hemisphere, left-brain hemisphere. Introduction There are many things to understand about how the human brain works or functions. Scientists found that the right and left hemisphere of the brain perform essential and respective functions (Clarke, Dewhurst &Aminoff, 1996). In order to substantiate this claim, there are many studies conducted for the hope of validating it (Sperry &Trevarthern, 1990). Some studies show that males have left-brain lateral dominance over their female counterparts (Sommer et al., 2004; Frost et al., 1999; Gur et al., 2000). Thus, the right-brain hemisphere has become subjected as supporting entity of the left-brain hemisphere (Turgeon, 1993). For this reason, this study is aimed to provide a substantial contribution to the growing knowledge concerning the important information in line with the left-brain and right-brain hemisphere of male and female respondents. Regarding this, the following questions were answered at the end of the study. 1. What are the right and left-brain hemisphere activations for the language tasks for males and females, respectively? 2. What are the right and left-brain hemisphere activations for the spatial tasks for males and females, respectively? 3. How significant is the difference on brain hemisphere activations between males and females for the language task? 4. How significant is the difference on brain hemisphere activations between males and females for the spatial task? To answer these questions, the study established the following hypotheses. Hypothesis 1: There will be a significant difference in left and right hemisphere activation for the language tasks for males Hypothesis 2: There will be a significant difference in left and right hemisphere activation for the spatial tasks for males Hypothesis 3: There will be a significant difference in left and right hemisphere activation for the language tasks for females Hypothesis 4: There will be a significant difference in left and right hemisphere activation for the spatial tasks for females Hypothesis 5: There will be a significant difference between males and females for the language task Hypothesis 6: There will be a significant difference between males and females for the spatial task Method Participants An opportunity based sample of 46 participants was recruited for the research project. There were 27 females, of mean age 22.96, S.D. 7.10 and the age range was 20-55. There were 19 males, mean age 22.47, S.D. 5.58 and the age range was 20-45. All of the participants were right handed and had normal or corrected to normal vision. The participants were screened to ensure that none were included with any learning disorders. Apparatus The primary instrument or device used in the study was electroencephalogram (EEG), a device that can measure tiny electrical signals produced by the brain. It thus provides a non invasive way of localizing brain function. The instrument was a Biopac MP 36 model with two EEG Electrodes that were held in place by a latex cap. The EEG data was extracted and analysed using Biopac Student Lab Pro. For the language section, the task required the participants to identify emotional neutral grammatically correct sentences. It was programmed with SuperLab. For the spatial task, participants were required to identify rotated and inverted letters. It was also programmed with SuperLab. Both the language and spatial tasks were presented to the participants on a PC with a 22inch monitor. Design The research was a mixed design; there were both repeated and independent measures. The repeated measures component of the research involved investigating hemispherical activity during the language and spatial task for males and females independently. The independent variable, IV, was hemisphere with two levels, left and right, and the dependent variables, DVs, were alpha and beta activity measured in mV (milivolts). The independent measures component of the research involved comparing hemispherical activity in males and females for the language and spatial task. The IVs were hemisphere, left and right, and sex, males and females, and the DVs were alpha and beta activity measured in mV. The activation in each hemisphere was recorded in males and females whilst they are performing a language task and a visuospatial task. From the data, the proponents were able to statistically analyze the differences in hemispherical activity between left and right hemisphere. This will allow the testing of the hypotheses. As the sex of the participant has also been recorded statistical comparisons between males and females was also been made to identify differences in hemispherical activation during the language and visuospatial tasks. The independent variables were hemisphere for the repeated measures component and the hemisphere and sex for the independent measures component. These were all taken from the actual EEG activity. Procedure The participants were recruited on as opportunity based sample due to availability. They were informed of the nature of the research and their right to withdraw at any time during the study without giving a reason in accordance with BPS regulations. The participants were seated in front of the PC presenting the language and spatial tasks. EEG electrodes were attached to the participants, one set on the left hemisphere and one set the right hemisphere. On both hemispheres the electrodes were positioned in the parietal lobe region and the reference electrode was attached behind the ear. Base line measurements of alpha and beta activity were recorded in both hemispheres with eyes open and eyes closed, this was to ensure that EEG activity was recorded and not noise. The participants were then asked to complete the language task and EEG was continually recorded, the same procedure was repeated for the spatial task. After completing both tasks the EEG electrodes and cap were removed from the participants. The participants were then fully debriefed about the aims of the research and thanked for their participation, contact and support details were also supplied. Results The analysis of variance (ANOVA) was implemented in order to find out the significant difference associated with the respondents’ sex differences in the functional organization of the brain for language and visual spatial tasks by employing two important periodic rhythms in the electroencephalogram (EEG), alpha and beta. Using the alpha and beta periodic rhythms of the EEG on the left and right hemisphere of the brain of the male and female respondents, data were generated and analyzed using ANOVA single factor and two-factor with replication. In Table 1, at alpha periodic rhythm of the EEG, the data left and right activation for the language tasks for male respondents generated F-computed value of 23.56 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.00 which is lower than .05. Table 1. ANOVA: Left and right activation for the language tasks for males (alpha). Source of Variation SS df MS F P-value F crit Between Groups 57.99 1 57.99 23.56 0.00 4.03 Within Groups 127.99 52 2.46 Total 185.98 53 In Table 2, it is shown that the language tasks at right hemisphere are higher than those in the left hemisphere. Table 2. Summary of the difference in the language tasks in males (alpha) Language Tasks Count Sum Average Variance Left (alpha) 27 51.7 1.91 0.40 Right (alpha) 27 107.66 3.99 4.53 In Table 3, at beta periodic rhythm of the EEG, the data left and right activation for the language tasks for male respondents generated F-computed value of 20.74 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.00 which is lower than .05. In Table 4, it is shown that the language tasks at right hemisphere are higher than those in the left hemisphere. Table 3. ANOVA: Left and right activation for the language tasks for males (beta) Source of Variation SS df MS F P-value F crit Between Groups 155.72 1 155.72 20.74 0.00 4.03 Within Groups 390.36 52 7.51 Total 546.08 53 Table 4. Summary of the difference in language tasks in males (beta) Language Tasks Count Sum Average Variance Left (beta) 27 69.84 2.59 0.52 Right (beta) 27 161.54 5.98 14.49 This results show that the mean amplitude for both alpha and beta waves are smaller for the left hemisphere, this indicated that there was a cognitive load in this hemisphere for males performing the language task. For the spatial tasks: In Table 5, at alpha periodic rhythm of the EEG, the data left and right activation for the spatial tasks for male respondents generated F-computed value of 41.31 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.00 which is lower than .05. In Table 6, it is shown that the spatial tasks at left hemisphere are higher than those in the right hemisphere. Table 5. ANOVA: Left and right activation for the spatial tasks for males (alpha) Source of Variation SS df MS F P-value F crit Between Groups 99.55 1 99.55 41.31 0.00 4.03 Within Groups 125.32 52 2.41 Total 224.87 53 Table 6. Summary of the difference in spatial tasks in males (alpha) Spatial Tasks Count Sum Average Variance Left (alpha) 27 168.56 6.24 2.93 Right (alpha) 27 95.24 3.53 1.89 In Table 7, at beta periodic rhythm of the EEG, the data left and right activation for the spatial tasks for male respondents generated F-computed value of 9.82 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.00 which is lower than .05. In Table 8, it is shown that the spatial tasks at left hemisphere are higher than those in the right hemisphere. Table 7. ANOVA: Left and right activation for the spatial tasks for males (beta) Source of Variation SS df MS F P-value F crit Between Groups 110.54 1 110.54 9.82 0.003 4.03 Within Groups 585.15 52 11.25 Total 695.69 53 Table 8. Summary of the difference in spatial tasks in males (beta) Spatial Tasks Count Sum Average Variance Left (beta) 27 191.81 7.10 12.34 Right (beta) 27 114.55 4.24 10.17 These results show that for the spatial task, the mean amplitude for both alpha and beta waves are smaller for the right hemisphere, this indicated that there was a cognitive load in this hemisphere for males performing the visuospatial task. In Table 9, at alpha periodic rhythm of the EEG, the data left and right activation for the language tasks for female respondents generated F-computed value of 0.80 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.37 which is higher than .05. Table 9. ANOVA: Left and right activation for the language tasks for females (alpha) Source of Variation SS df MS F P-value F crit Between Groups 6.09 1 6.09 0.80 0.37 4.03 Within Groups 394.40 52 7.58 Total 400.49 53 In Table 10, at beta periodic rhythm of the EEG, the data left and right activation for the language tasks for female respondents generated F-computed value of 0.50 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.48 which is higher than .05. Table 10. ANOVA: Left and right activation for the language tasks for females (beta) Source of Variation SS df MS F P-value F crit Between Groups 9.64 1 9.64 0.50 0.48 4.03 Within Groups 1002.40 52 19.28 Total 1012.04 53 It can therefore be concluded from the results that the mean amplitude for both alpha and beta waves are very similar for both hemispheres, this indicated that there was a similar cognitive load in each hemisphere for females performing the language task. In Table 11, at alpha periodic rhythm of the EEG, the data left and right activation for the spatial tasks for female respondents generated F-computed value of 40.91 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.00 which is lower than .05 In Table 12, it is shown that the spatial tasks at left hemisphere are higher than those in the right hemisphere. Table 11. ANOVA: Left and right activation for the spatial tasks for females (alpha) Source of Variation SS df MS F P-value F crit Between Groups 115.25 1 115.25 40.91 0.00 4.03 Within Groups 146.48 52 2.82 Total 261.73 53 Table 12. Summary of the difference in the spatial tasks in females (alpha) Spatial Tasks Count Sum Average Variance Left (alpha) 27 146.18 5.41 4.53 Right (alpha) 27 67.29 2.49 1.10 In Table 13, at beta periodic rhythm of the EEG, the data left and right activation for the spatial tasks for female respondents generated F-computed value of 52.82 and F-critical value of 4.03 at .05 level of significance. The P-value is 0.00 which is lower than .05. In Table 14, it is shown that the spatial tasks at left hemisphere are higher than those in the right hemisphere. Table 13. ANOVA: Left and right activation for the spatial tasks for females (beta) Source of Variation SS df MS F P-value F crit Between Groups 86.26 1 86.26 52.82 0.00 4.03 Within Groups 84.92 52 1.63 Total 171.18 53 Table 14. Summary of the difference in the spatial tasks in females (beta) Spatial Tasks Count Sum Average Variance Left (beta) 27 138.71 5.14 2.44 Right (beta) 27 70.46 2.61 0.83 The inference that can be made from the results is that the mean amplitude for both alpha and beta waves are smaller for the right hemisphere, this indicated that there was a cognitive load in this hemisphere for females performing the visuospatial task. A male-female comparison was made to establish whether there was a difference in activation. In Table 15, at alpha periodic rhythm of the EEG, the data left and right activation for the language tasks for male and female respondents generated F-computed value of 15.33 and F-critical value of 3.93 at .05 level of significance. The P-value is 0.00 which is lower than .05. This shows that the amplitude of alpha waves in males is lower in the left hemisphere than the right hemisphere, however this pattern is not observed in the females performing the language task. The amplitude of alpha waves in males in the right hemisphere is similar to the amplitude of alpha waves in both the left and right hemispheres of the females. This would suggest reduced cognitive load in these hemispheres. In Table 16, it is shown that the language tasks in females are higher than their male counterparts. There is also a significant difference between the right and left activation for the two groups under the language tasks, by which right activation was generally higher than the left activation as showcased through a 10.12 F-computed value over the P-value of 0.00 and 3.93 at .05 level of significance. Table 15. ANOVA: Left and right activation for the language tasks between males and females (alpha) Source of Variation SS df MS F P-value F crit Sample 77.00 1 77.00 15.33 0.00 3.93 Columns 50.83 1 50.83 10.12 0.00 3.93 Interaction 13.25 1 13.25 2.64 0.10 3.93 Within 522.39 104 5.02 Total 663.47 107 Table 16. Summary of the difference in the language tasks between males and females (alpha) Summary L_Alpha_lang_amp R_Alpha_lang_amp Total Male Count 27 27 54 Sum 51.70 107.66 159.36 Average 1.91 3.99 2.95 Variance 0.40 4.53 3.51 Female Count 27 27 54 Sum 116.21 134.34 250.55 Average 4.30 4.98 4.64 Variance 6.00 9.17 7.56 Total Count 54 54 Sum 167.91 242 Average 3.11 4.48 Variance 4.59 6.97 The data shows that amplitude of alpha waves in males is lower in the left hemisphere than the right hemisphere, however this pattern is not observed in the females performing the language task. The amplitude of alpha waves in males in the right hemisphere is similar to the amplitude of alpha waves in both the left and right hemispheres of the females. This would suggest reduced cognitive load in these hemispheres. In Table 17, at beta periodic rhythm of the EEG, the data left and right activation for the language tasks for male and female respondents generated F-computed value of 16.97 and F-critical value of 3.93 at .05 level of significance. The P-value is 0.00 which is lower than .05. In Table 18, it is shown that the language tasks in females are higher than their male counterparts. There is also a significant difference between the right and left activation for the two groups under the language tasks, by which right activation was generally higher than the left activation as showcased through a 9.07 F-computed value over the P-value of 0.00 and 3.93 at .05 level of significance. Table 17. ANOVA: Left and right activation for the language tasks between males and females (beta) Source of Variation SS df MS F P-value F crit Sample 227.30 1 227.30 16.97 0.00 3.93 Columns 121.43 1 121.43 9.07 0.00 3.93 Interaction 43.93 1 43.93 3.28 0.07 3.93 Within 1392.76 104 13.39 Total 1785.42 107 Table 18. Summary of the difference in the language tasks between males and females (beta) Summary L_Beta_lang_amp R_Beta_lang_amp Total Male Count 27 27 54 Sum 69.84 161.54 231.38 Average 2.59 5.98 4.28 Variance 0.52 14.49 10.30 Female Count 27 27 54 Sum 182.62 205.44 388.06 Average 6.76 7.61 7.19 Variance 19.94 18.61 19.10 Total Count 54 54 Sum 252.46 366.98 Average 4.68 6.80 Variance 14.48 16.91 The amplitude of beta waves in males is lower in the left hemisphere than the right hemisphere, however this pattern is not observed in the females performing the language task. The amplitude of beta waves in males in the right hemisphere is similar to the amplitude of beta waves in both the left and right hemispheres of the females. This would suggest reduced cognitive load in these hemispheres. In Table 19, at alpha periodic rhythm of the EEG, the data left and right activation for the spatial tasks for male and female respondents generated F-computed value of 8.97 and F-critical value of 3.93 at .05 level of significance. The P-value is 0.00 which is lower than .05. In Table 20, it is shown that the spatial tasks in males are higher than their female counterparts. There is also a significant difference between the right and left activation for the two groups under the spatial tasks, by which left activation was generally higher than the right activation as showcased through a 82.08 F-computed value over the P-value of 0.00 and 3.93 at .05 level of significance. Table 19. ANOVA: Left and right activation for the spatial tasks between males and females (alpha) Source of Variation SS df MS F P-value F crit Sample 23.45 1 23.45 8.97 0.00 3.93 Columns 214.52 1 214.52 82.08 0.00 3.93 Interaction 0.29 1 0.29 0.11 0.74 3.93 Within 271.79 104 2.61 Total 510.05 107 Table 20. Summary of the difference in the spatial tasks between males and females (alpha) Summary L_Alpha_spatial_amp R_Alpha_spatial_amp Total Male Count 27 27 54 Sum 168.56 95.24 263.80 Average 6.24 3.53 4.89 Variance 2.93 1.89 4.24 Female Count 27 27 54 Sum 146.18 67.29 213.47 Average 5.41 2.49 3.95 Variance 4.53 1.10 4.94 Total Count 54 54 Sum 314.74 162.53 Average 5.83 3.01 Variance 3.83 1.74 In both males and females there were reductions in alpha wave amplitudes in the right hemisphere compared to the left hemisphere, this would suggest a greater cognitive load during the visuospatial task. In Table 21, at beta periodic rhythm of the EEG, the data left and right activation for the spatial tasks for male and female respondents generated F-computed value of 13.57 and F-critical value of 3.93 at .05 level of significance. The P-value is 0.00 which is lower than .05. In Table 22, it is shown that the spatial tasks in males are higher than their female counterparts. There is also a significant difference between the right and left activation for the two groups under the spatial tasks, by which left activation was generally higher than the right activation as showcased through a 30.43 F-computed value over the P-value of 0.00 and 3.93 at .05 level of significance. Table 21. ANOVA: Left and right activation for the spatial tasks between males and females (beta) Source of Variation SS df MS F P-value F crit Sample 87.46 1 87.46 13.57 0.00 3.93 Columns 196.05 1 196.05 30.43 0.00 3.93 Interaction 0.75 1 0.75 0.12 0.73 3.93 Within 670.07 104 6.44 Total 954.34 107 Table 22. Summary of the difference in the spatial tasks between males and females (beta) Summary L_Beta_spatial_amp R_Beta_spatial_amp Total Male Count 27 27 54 Sum 191.81 114.55 306.36 Average 7.10 4.24 5.67 Variance 12.34 0.18 13.13 Female Count 27 27 54 Sum 138.71 70.46 209.17 Average 5.14 2.61 3.88 Variance 2.44 0.83 3.23 Total Count 54 54 Sum 330.52 185.01 Average 6.12 3.43 Variance 8.23 6.07 In both males and females there are reduces beta wave amplitudes in the right hemisphere compared to the left hemisphere, this would suggest a greater cognitive load during the visuospatial task. However, the amplitude of the beta waves in the right for females is lower than that of males, suggesting that there was more cognitive demand for females during the visuospatial task. Discussion Alpha as a periodic rhythm in the EEG is a wave pattern linked to the brain when an adult is awake, but relaxed with eyes closed (Mulert and Lemieux, 2009). Beta on the other hand is a periodic rhythm in the EEG associated with the wave pattern of the brain when an individual is exerting mental effort (Stern, 2013). For the left and right hemisphere activation for the language tasks for males, there was a significant difference both at alpha and beta periodic rhythm in the EEG. It was found that the activation was higher at the right hemisphere. In males there will be a significant difference in activation between the left and right hemisphere during a language task For both alpha and beta waves there were significantly lower amplitude waves in the left hemisphere compared to the right hemisphere. This suggested that there was a greater cognitive load in the left hemisphere during the language task and in males this hemisphere is responsible for the processing of language. In males there will be a significant difference in activation between the left and right hemisphere during a spatial task For both alpha and beta waves there were significantly lower amplitude waves in the right hemisphere compared to the right hemisphere. This suggested that there was a greater cognitive load in the right hemisphere during the visuospatial task and in males this hemisphere is responsible for the processing of visuospatial information. In females there will be no significant difference in activation between the left and right hemisphere during a language task For both alpha and beta waves there was no significant difference in the amplitude of the waves between the left hemisphere and the right hemisphere. This suggested that there was a division of the cognitive load between the hemispheres during the language task and in females the left and right hemisphere are responsible for the processing of language. In females there will be a significant difference in activation between the left and right hemisphere during a spatial task For both alpha and beta waves there were significantly lower amplitude waves in the right hemisphere compared to the right hemisphere. This suggested that there was a greater cognitive load in the right hemisphere during the visuospatial task and in females this hemisphere is responsible for the processing of visuospatial information. There will be a significant difference in hemispherical activity between males and females performing a language task For both alpha and beta waves there was a significant main effect of hemisphere and sex (differences between left and right and difference between males and females). There was also a significant interaction between hemisphere and sex, this indicated that the effect of hemisphere was not constant across sex. Post hoc t-tests revealed that there was significantly more activation in the males left hemisphere than in the females during the language task. The amplitude of alpha and beta waves were greater in the females in both left and right hemisphere than the males during the language task suggesting less cognitive load. There will be a significant difference in hemispherical activity between males and females performing a spatial task For both alpha and beta waves there was a significant main effect of hemisphere and sex (differences between left and right and difference between males and females). There was no significant interaction between hemisphere and sex; this indicated that the effect of hemisphere was not constant across sex. Post hoc t-tests revealed that there was significantly more activation in the females’ right hemisphere than in the males during the visuospatial task. The amplitude of alpha and beta waves were greater in the males in both left and right hemisphere than the females during the visuospatial task suggesting less cognitive load. However, there were significantly lower beta amplitudes in the females left hemisphere during the visuospatial task, this indicated that this hemisphere may also be responsible for processing some of the visuospatial information in females. The results support the idea that males may have left lateralized dominance over their female counterparts, and females may have that level of dominance particularly somewhere in the right hemisphere of the brain (Sommer et al., 2004; Frost et al., 1999; Gur et al., 2000). This further suggests that for language tasks, the right hemisphere is most likely activated, while for the spatial tasks, the left hemisphere is used, which could be due to lateralization or specialized function of each hemisphere. It has long been viewed that each hemisphere of the brain performs respective functions. It has also long been thought that the left-brain hemisphere is having its dominance in areas of language and logic, while the right-brain hemisphere focuses on nonverbal, intuitive, holistic level of thinking (Ray et al., 1981). Left-brain hemisphere has been regarded as the dominant overall, which controls all higher reasoning ability making the right-brain hemisphere as a mere subordinate to the left (Davidson et al., 1990). References Andrew J.O. Whitehouse., Dorothy V.M. Bishop. (2009) Corrigendum to “Hemispheric division of function is the result of independent probabilistic biases” Neuropsychologia 47, 1938–1943 S. Knecht., B. dragger., M. Deppe., L. bobe (2000). Handedness and hemispheric language dominance in healthy humans. BRAIN, vol 123 Pp. 2512-2518 Gordon., Breach. Brodmann classification. International Journal of Neuroscience, Vol 37-38 Pp. 36 Clarke, E., Dewhurst, K., &Aminoff, M. 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