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A persistent unanswered question in cognitive neuroscience has been what are the neural origins of human brain lateralization? Language is strongly lateralized to the left-hemisphere, however, lateralization varies with language experience. Bilinguals demonstrate a greater extent and variability of right-hemisphere involvement for language relative to monolinguals. Here, bilingualism is used as a lens into the conditions that drive brain lateralization. Why does bilingual language processing yields more robust bilateral neural activation relative to monolingual language processing? Neural activation and functional connectivity were measured to test hypotheses about the temporal dynamics of hemispheric recruitment during language processing in monolingual and bilingual children with varying ages of first bilingual language exposure. Hypothesis (1), The human brain is strongly left-hemisphere lateralized for language, but, when faced with the demands of two languages, additional right-hemisphere resources are recruited. Hypothesis (2), The human brain has the potential for enhanced dual hemispheric language processing that can be either potentiated or not based on early life bilingual versus monolingual language experience. If dual language experience places increased cognitive demands on the bilingual brain requiring additional right-hemisphere resources, asynchronous neural activation in left and right hemispheres was predicted. If dual language experience potentiates dual hemispheric language processing, synchronous neural activation in left and right hemispheres was predicted. Furthermore, only early-exposed bilinguals but not later-exposed bilinguals or monolinguals, would show synchronous neural activation across the hemispheres. Early experience with one language (monolinguals) or two languages at different times during a child's development (early-exposed bilinguals, later-exposed bilinguals) revealed differences in the time-course of activation across the two hemispheres' language areas, supporting Hypothesis (2). Monolinguals and later-exposed bilinguals showed asynchronous activation between the hemispheres. Early-exposed bilinguals showed synchronous activation between the hemispheres. The results provide a new view on how different experiences can drive lateralization in development and reveal the neural basis of bilateral activation in the bilingual brain. Synchronous temporal accessing of the hemispheres in bilinguals suggests early life bilingual language experience may support more equal and efficient hemispheric involvement, and, in turn, constitute the brain-based mechanism that makes possible the widely observed linguistic and cognitive advantages in young bilinguals.

A persistent unanswered question in cognitive neuroscience has been what are the neural origins of human brain lateralization? Language is strongly lateralized to the left-hemisphere, however, lateralization varies with language experience. Bilinguals demonstrate a greater extent and variability of right-hemisphere involvement for language relative to monolinguals. Here, bilingualism is used as a lens into the conditions that drive brain lateralization. Why does bilingual language processing yields more robust bilateral neural activation relative to monolingual language processing? Neural activation and functional connectivity were measured to test hypotheses about the temporal dynamics of hemispheric recruitment during language processing in monolingual and bilingual children with varying ages of first bilingual language exposure. Hypothesis (1), The human brain is strongly left-hemisphere lateralized for language, but, when faced with the demands of two languages, additional right-hemisphere resources are recruited. Hypothesis (2), The human brain has the potential for enhanced dual hemispheric language processing that can be either potentiated or not based on early life bilingual versus monolingual language experience. If dual language experience places increased cognitive demands on the bilingual brain requiring additional right-hemisphere resources, asynchronous neural activation in left and right hemispheres was predicted. If dual language experience potentiates dual hemispheric language processing, synchronous neural activation in left and right hemispheres was predicted. Furthermore, only early-exposed bilinguals but not later-exposed bilinguals or monolinguals, would show synchronous neural activation across the hemispheres. Early experience with one language (monolinguals) or two languages at different times during a child's development (early-exposed bilinguals, later-exposed bilinguals) revealed differences in the time-course of activation across the two hemispheres' language areas, supporting Hypothesis (2). Monolinguals and later-exposed bilinguals showed asynchronous activation between the hemispheres. Early-exposed bilinguals showed synchronous activation between the hemispheres. The results provide a new view on how different experiences can drive lateralization in development and reveal the neural basis of bilateral activation in the bilingual brain. Synchronous temporal accessing of the hemispheres in bilinguals suggests early life bilingual language experience may support more equal and efficient hemispheric involvement, and, in turn, constitute the brain-based mechanism that makes possible the widely observed linguistic and cognitive advantages in young bilinguals.

In accordance with an experimental setup this thesis investigates to what extent the participants' attitudes and aesthetic preferences are influenced by the lateral direction of light in moving image sequences. It is also investigated whether the participants' handedness correlates with their advertising evaluation. The purpose of the study is to generate new knowledge of potential biases in moving images that could be applied by image producers to create more compelling commercials. Our work is based on a transdisciplinary theoretical approach and the results are analyzed based on biopsychological, sociocultural and perceptual explanatory models. Three self-designed commercials with a left oriented illumination position were used as stimulus, the stimulus were also inverted horizontally. The participants were asked to assess their attitudes toward the commercials with either left or right oriented lighting. Two surveys were conducted: one with a within-subjects design and one with a between-subjects design, a total of 172 people participated. No significant difference between left and right oriented illumination position occurred in any of the groups for neither feelings toward ad, Aad , Ab , or PI. The results suggests that a bias does not occur in dynamic images, unlike the left oriented bias that has been reliably shown in previous studies that relate to still images. Nor could any correlation be established between reported attitudes and handedness.

O presente trabalho teve por objetivo pesquisar os efeitos que as bandas de freqüência espacial alta e baixa têm no reconhecimento de faces em campo visual lateralizado. Foram distribuídos aleatoriamente 40 participantes em dois grupos. Os voluntários observaram 14 fotos de faces sem filtragem até memorizá-las. A seguir foram apresentadas 56 fotos de faces com filtragens de freqüências espaciais, intercaladas aleatoriamente com apresentações de faces não mostradas anteriormente. Cada uma delas foi exibida na tela durante 300 ms mediante a metodologia de apresentação dicótica. O participante devia responder se a face mostrada pertencia ao grupo de fotos inicialmente observado. As freqüências de respostas permitiram calcular as curvas ROC (Receiver Operating Characteristic) e os parâmetros Az e da preconizado pela Teoria de Detecção de Sinal (MACMILLAN; CREELMAN, 2005) para as faces naturais, faces compostas de freqüências espaciais baixas e faces compostas de freqüências espaciais altas. Os resultados obtidos mostram que as faces Originais foram melhor reconhecidas do que as faces com Freqüências Espaciais Altas (FEA) ou Freqüências Espaciais Baixas (FEB). Ao contrário do achado na literatura, o Hemisfério Esquerdo (HE) teve uma tendência a reconhecer mais eficazmente as faces do que o Hemisfério Direito (HD), independente da condição de filtragem. O HD é igualmente competente do que o HE para processar FEB, mas pior do que o HE para processar FEA. Quanto à performance por gênero, tanto homens quanto mulheres tiveram um desempenho similar quando as faces foram processadas com o HD. O desempenho das mulheres ficou de acordo com a hipótese da FE, pois o reconhecimento que fizeram para as faces com FEA foi melhor do que para as que tinham predomínio de FEB. Os homens, mesmo com o HE, fizeram um reconhecimento melhor das faces com predomínio de FEB do que das faces com FEA. / This study was made with the objective of investigate the effects of high and low spatial frequency bands in face recognition in lateralized visual field. 40 participants were randomly distributed in two groups. The volunteers viewed fourteen non-filtered pictures of faces until they managed to memorize them. After that, fifty six spatial frequency filtered pictures of faces were presented randomly interspersed with pictures of faces previously showed. Each one of them was exhibited in the screen for three hundred milliseconds using the dichotic presentation procedure. The participant should answer whether the face presented belonged to the group of pictures initially viewed. The frequency of responses allowed to calculate the ROC (Receiver Operating Characteristic) Curves and the Az and da parameters praised by the Signal Detection Theory (Macmillan; Creelman, 2005) for natural faces, low spatial frequency composed faces and high spatial frequency composed faces. Results showed that original faces were better recognized than faces with high spatial frequencies (HSF) and low spatial frequencies (LSF). Differently from literature, the left hemisphere was more accurate than the right to recognize faces, regardless of the filter condition. The RH was equivalent to the LH to process LSF, but worse than the LH to process HSF. Concerning the performance of the genders, men and women judged faces in a very similar way when they used the RH. The performance of women agreed with the FE hypothesis, being faces with HSF recognized better than faces with LSF. Men, even using the LH, were more accurate to recognize faces with LSF than HSF.

Humans display a 90% population level bias towards right-handedness, implying the vast majority of people have a left-hemisphere dominant for motor control. Although handedness presents a weak, but very consistent heritability across the literature (estimated to be approximately 25%), to date few genetic loci associated with this complex trait have been identified and replicated in subsequent studies. One such gene which has been found to be associated with handedness and subsequently replicated is PCSK6, most recently through a quantitative GWAS (P < 0.5*10−8, Brandler et al. (2013)). Interestingly, PCSK6 is known to activate Nodal, a morphogen involved in a highly conserved bilaterian pathway known to regulate left-right body axis determination. Here I present the first molecular characterisation of a handedness-associated region by conducting a detailed functional analysis of the PCSK6 locus, combining genetic analysis, in silico prediction and molecular assays to investigate how common genetic variants influence handedness-related phenotypes. Specifically, I defined the associated locus to be 12.7 kb in size, spanning a predicted 1.8 kb bidirectional promoter which controls the expression of both an antisense long non-coding RNA (lncRNA), and a novel short PCSK6 isoform. A series of luciferase-expressing constructs were generated to characterise the promoter, identifying a minimal sequence capable of driving transcription in a sense strand direction. I have demonstrated experimentally that one of the top associated markers in previous GWA studies, rs11855145, directly creates/disrupts a suspected transcription factor bind site in the vicinity of this bidirectional promoter. Further functional studies of the genetic variation within PCSK6 may help explain the molecular regulatory mechanisms affecting gene expression. This project provides a model for assays to study other GWAS-nominated candidate genes, and in particular for establishing the role of noncoding variants. The findings from this study support the role of common variants in influencing complex phenotypes, such as handedness.

Evidências sugerem que a lateralização cerebral é uma característica fundamental dos vertebrados. Nos seres humanos, tem sido sugerido que o hemisfério direito é especializado no processamento de informação emocional negativa e o hemisfério esquerdo no controle da função motora. Em roedores, evidências de lateralização hemisférica são escassas. Diante disso, utilizamos a hemisferectomia para avaliar a importância relativa de cada hemisfério no controle emocional e na atividade motora espontânea em camundongos. Machos adultos foram submetidos à hemisferectomia direita (HD), hemisferectomia esquerda (HE) ou a simulação da cirurgia (SHAM). Para ajudar na interpretação dos resultados, uma amostra adicional de camundongos foi submetida à aspiração unilateral da área frontoparietal esquerda (FPE), da área frontoparietal direito (FPD) ou a simulação da cirurgia (CONT). Quinze dias após a cirurgia, a reatividade emocional e a ambulação foram avaliadas no teste de campo aberto durante 10 minutos (dividido em intervalos de 1 min). A arena de campo aberto consistiu em uma caixa de polipropileno, cujo fundo foi dividido em 16 retângulos do mesmo tamanho. O número total de retângulos cruzados pelo animal foi utilizado como a medida da atividade locomotora espontânea. Considerando-se que os camundongos evitam áreas abertas, a locomoção no centro e o tempo despendido nos retângulos centrais foram utilizados para avaliar a reatividade emocional. Em relação à atividade locomotora as duas técnicas cirúrgicas revelaram assimetrias na direção oposta. A atividade locomotora do grupo HE aumentou ao longo do período de teste e foi maior do que a dos grupos HD e SHAM. Em contraste, a atividade locomotora do grupo FPD diminuiu ao longo do período de teste e foi superior a ambos os grupos, FPE e CONT. Em relação à reatividade emocional, o grupo HE passou menos tempo na área central que os grupos HD e CONT. Não foram observadas diferenças entre FPD, FPE e o grupo CONT. Os nossos resultados sugerem que os dois hemisférios contribuem de forma assimétrica para controlar de reatividade emocional e para controlar de atividade motora em camundongos. De forma semelhante ao que é observado em humanos, o hemisfério direito dos camundongos foi mais associado com o processamento de informação emocional negativa. Em relação aos dados de hiperatividade, as diferenças observadas entre os animais hemisferectomizados e com lesão frontoparietal sugerem que mais de um circuito (ou sistema) lateralizado pode mediar a atividade locomotora espontânea. / Evidence exists indicating that cerebral lateralization is a fundamental feature of all vertebrates. In humans, it has been suggested that the right hemisphere is involved in processing negative emotional information and the left hemisphere is involved in control of motor function. In rodents, evidence for hemispheric lateralization is sparse. In this regard, here, we used unilateral hemispherectomy to study the relative importance of each hemisphere in controlling emotion and spontaneous motor activity in mice. Adult male mice were submitted to right hemispherectomy (RH), left hemispherectomy (LH) or sham surgery (SHAM). To help the interpretation of results an addition sample of mice was submitted to unilateral suction of left frontoparietal area (LFP), right frontoparietal area (RFP) or sham surgery (CONT). Fifteen days after surgery, both the emotional reactivity and the spontaneous locomotor activity were assessed in the open field test 10 min (divided into 1 min intervals). The open field arena consisted of a polypropylene box in which the floor was divided into 16 same-sized rectangles. The total number of rectangles crossed was used as the measure of spontaneous locomotor activity. Considering that mice avoid open areas, the ambulation in the center and time spent in the central rectangles were used to assess emotional reactivity. Regarding locomotor activity, the two surgical techniques reveal asymmetries in opposite direction. The locomotor activity of LH, which increased along the test period, was higher than both RH and SHAM. In contrast, the locomotor activity of RFP which decreased along the test period was higher than both LFP and CONT. Regarding emotional reactivity, the LH group spent less time in the central area than both RH and SHAM groups. No differences were observed between LFP, RFP and CONT groups. Our results suggest that the two hemispheres contribute asymmetrically to control of emotional reactivity and to control of motor activity in mice. Similarly to what is observed in humans, the right hemisphere of mice was more involved in processing negative emotional information. Regarding locomotor hyperactivity, the differences observed between hemispherectomized and frontoparietal-lesioned mice suggest that multiple lateralized circuits (or systems) may underlie spontaneous locomotor activity.

O presente estudo teve por objetivo investigar se o reconhecimento de faces ocorre prioritariamente por processamento analítico ou holístico nos hemisférios cerebrais em homens e mulheres por meio do estudo do espectro de frequência espacial. Para isso, no Experimento I, 40 voluntários (20 mulheres) realizaram duas sessões. Em cada uma delas foram memorizadas 14 faces para uma tarefa de reconhecimento. Nesta, cada face foi apresentada por 300 ms, e em uma das sessões as imagens foram apresentadas somente no hemicampo visual direito, e noutra só no hemicampo visual esquerdo por meio de uma adaptação do método do campo visual dividido. A tarefa dos participantes foi assinalar o grau de confiabilidade de sua resposta (confidence rating method) ao discriminar as faces memorizadas de outras inéditas. Os estímulos da tarefa de reconhecimento foram apresentados em três condições: (1) em frequências espaciais altas, FEAs, (2) em frequências espaciais baixas, FEBs, e (3) sem filtragem, SFE. As frequências de respostas aos graus de confiabilidade permitiram calcular as curvas ROC e os parâmetros Az e da da Teoria de Deteção de Sinal. Por meio destes, foi comparado o desempenho do reconhecimento facial nas diferentes faixas do espectro espacial. De maneira complementar, foi realizado uma ANOVA para testar a diferença dos tempos de resposta no reconhecimento entre as filtragens. Não foi evidenciada especialização hemisférica no reconhecimento de faces com filtragem espacial. Mas homens, de modo tênue, perceberam melhor faces em FEBs e mulheres em FEAs. Para verificar se este resultado não se deu em função da apresentação lateralizada, foi realizado o Experimento II, nos moldes de uma sessão experimental do Experimento I, mas com apresentação central. Vinte voluntários (10 mulheres) participaram do experimento. Novamente, homens e mulheres foram mais sensíveis às faces em FEBs e FEAs, respectivamente. Deste modo, conclui-se que homens utilizam mais recursos holísticos e mulheres, por sua vez, operações analíticas. Os resultados dão bases para a não ocorrência de especialização hemisférica de frequencias espaciais no reconhecimento de faces em longos tempos de exposições. A diferença de sexo observada e nos atenta para a necessidade de controle amostral por sexo em pesquisas da área. / This study aimed to investigate whether face recognition occurs primarily by analytic or holistic processing in the cerebral hemispheres of men and women through the study of the spatial frequency spectrum. Therefore, in Experiment I, 40 volunteers (20 women) performed two sessions. In each of, 14 faces were memorized for a recognition task and each face was presented for 300 ms. Images were presented only in the right visual hemifield in a session, and in another only in the left visual hemifield by means of an adaptation of the method of divided visual field. The participants task was to assign the reliability of their response (confidence rating method) to discriminate the study faces from distractors. The recognition task stimuli were presented in three conditions: (1) at high spatial frequencies, FEAs, (2) at low spatial frequencies, FEBs, and (3) unfiltered, SFE. The frequencies of responses to the degree of reliability used to calculate ROC curves and parameters Az and da of the Signal Detection Theory compared the performance of face recognition in different bands of the spectrum. In a complementary way, an ANOVA was conducted to test response times differences in the recognition between filtering. There was no evidence of hemispheric specialization in face recognition with spatial filtering. But men had better performance in recognizing faces in FEBs and women faces in FEAs. To verify that this result was not in function of lateralized presentation, Experiment II was conducted, along the lines of an experimental session of Experiment I, but with central presentation. Twenty volunteers (10 women) participated in the experiment. Again, men and women were more sensitive to faces in FEBs and FEAs, respectively. Thus it follows that men use holistic resources and women analytical operations. The results provide no basis for the occurrence of hemispheric specialization of spatial frequencies in face recognition over long exposure times. The sex difference observed brings us to the need for control sample by sex in spatial frequency research.

O presente estudo teve por objetivo investigar se o reconhecimento de faces ocorre prioritariamente por processamento analítico ou holístico nos hemisférios cerebrais em homens e mulheres por meio do estudo do espectro de frequência espacial. Para isso, no Experimento I, 40 voluntários (20 mulheres) realizaram duas sessões. Em cada uma delas foram memorizadas 14 faces para uma tarefa de reconhecimento. Nesta, cada face foi apresentada por 300 ms, e em uma das sessões as imagens foram apresentadas somente no hemicampo visual direito, e noutra só no hemicampo visual esquerdo por meio de uma adaptação do método do campo visual dividido. A tarefa dos participantes foi assinalar o grau de confiabilidade de sua resposta (confidence rating method) ao discriminar as faces memorizadas de outras inéditas. Os estímulos da tarefa de reconhecimento foram apresentados em três condições: (1) em frequências espaciais altas, FEAs, (2) em frequências espaciais baixas, FEBs, e (3) sem filtragem, SFE. As frequências de respostas aos graus de confiabilidade permitiram calcular as curvas ROC e os parâmetros Az e da da Teoria de Deteção de Sinal. Por meio destes, foi comparado o desempenho do reconhecimento facial nas diferentes faixas do espectro espacial. De maneira complementar, foi realizado uma ANOVA para testar a diferença dos tempos de resposta no reconhecimento entre as filtragens. Não foi evidenciada especialização hemisférica no reconhecimento de faces com filtragem espacial. Mas homens, de modo tênue, perceberam melhor faces em FEBs e mulheres em FEAs. Para verificar se este resultado não se deu em função da apresentação lateralizada, foi realizado o Experimento II, nos moldes de uma sessão experimental do Experimento I, mas com apresentação central. Vinte voluntários (10 mulheres) participaram do experimento. Novamente, homens e mulheres foram mais sensíveis às faces em FEBs e FEAs, respectivamente. Deste modo, conclui-se que homens utilizam mais recursos holísticos e mulheres, por sua vez, operações analíticas. Os resultados dão bases para a não ocorrência de especialização hemisférica de frequencias espaciais no reconhecimento de faces em longos tempos de exposições. A diferença de sexo observada e nos atenta para a necessidade de controle amostral por sexo em pesquisas da área. / This study aimed to investigate whether face recognition occurs primarily by analytic or holistic processing in the cerebral hemispheres of men and women through the study of the spatial frequency spectrum. Therefore, in Experiment I, 40 volunteers (20 women) performed two sessions. In each of, 14 faces were memorized for a recognition task and each face was presented for 300 ms. Images were presented only in the right visual hemifield in a session, and in another only in the left visual hemifield by means of an adaptation of the method of divided visual field. The participants task was to assign the reliability of their response (confidence rating method) to discriminate the study faces from distractors. The recognition task stimuli were presented in three conditions: (1) at high spatial frequencies, FEAs, (2) at low spatial frequencies, FEBs, and (3) unfiltered, SFE. The frequencies of responses to the degree of reliability used to calculate ROC curves and parameters Az and da of the Signal Detection Theory compared the performance of face recognition in different bands of the spectrum. In a complementary way, an ANOVA was conducted to test response times differences in the recognition between filtering. There was no evidence of hemispheric specialization in face recognition with spatial filtering. But men had better performance in recognizing faces in FEBs and women faces in FEAs. To verify that this result was not in function of lateralized presentation, Experiment II was conducted, along the lines of an experimental session of Experiment I, but with central presentation. Twenty volunteers (10 women) participated in the experiment. Again, men and women were more sensitive to faces in FEBs and FEAs, respectively. Thus it follows that men use holistic resources and women analytical operations. The results provide no basis for the occurrence of hemispheric specialization of spatial frequencies in face recognition over long exposure times. The sex difference observed brings us to the need for control sample by sex in spatial frequency research.

Evidências sugerem que a lateralização cerebral é uma característica fundamental dos vertebrados. Nos seres humanos, tem sido sugerido que o hemisfério direito é especializado no processamento de informação emocional negativa e o hemisfério esquerdo no controle da função motora. Em roedores, evidências de lateralização hemisférica são escassas. Diante disso, utilizamos a hemisferectomia para avaliar a importância relativa de cada hemisfério no controle emocional e na atividade motora espontânea em camundongos. Machos adultos foram submetidos à hemisferectomia direita (HD), hemisferectomia esquerda (HE) ou a simulação da cirurgia (SHAM). Para ajudar na interpretação dos resultados, uma amostra adicional de camundongos foi submetida à aspiração unilateral da área frontoparietal esquerda (FPE), da área frontoparietal direito (FPD) ou a simulação da cirurgia (CONT). Quinze dias após a cirurgia, a reatividade emocional e a ambulação foram avaliadas no teste de campo aberto durante 10 minutos (dividido em intervalos de 1 min). A arena de campo aberto consistiu em uma caixa de polipropileno, cujo fundo foi dividido em 16 retângulos do mesmo tamanho. O número total de retângulos cruzados pelo animal foi utilizado como a medida da atividade locomotora espontânea. Considerando-se que os camundongos evitam áreas abertas, a locomoção no centro e o tempo despendido nos retângulos centrais foram utilizados para avaliar a reatividade emocional. Em relação à atividade locomotora as duas técnicas cirúrgicas revelaram assimetrias na direção oposta. A atividade locomotora do grupo HE aumentou ao longo do período de teste e foi maior do que a dos grupos HD e SHAM. Em contraste, a atividade locomotora do grupo FPD diminuiu ao longo do período de teste e foi superior a ambos os grupos, FPE e CONT. Em relação à reatividade emocional, o grupo HE passou menos tempo na área central que os grupos HD e CONT. Não foram observadas diferenças entre FPD, FPE e o grupo CONT. Os nossos resultados sugerem que os dois hemisférios contribuem de forma assimétrica para controlar de reatividade emocional e para controlar de atividade motora em camundongos. De forma semelhante ao que é observado em humanos, o hemisfério direito dos camundongos foi mais associado com o processamento de informação emocional negativa. Em relação aos dados de hiperatividade, as diferenças observadas entre os animais hemisferectomizados e com lesão frontoparietal sugerem que mais de um circuito (ou sistema) lateralizado pode mediar a atividade locomotora espontânea. / Evidence exists indicating that cerebral lateralization is a fundamental feature of all vertebrates. In humans, it has been suggested that the right hemisphere is involved in processing negative emotional information and the left hemisphere is involved in control of motor function. In rodents, evidence for hemispheric lateralization is sparse. In this regard, here, we used unilateral hemispherectomy to study the relative importance of each hemisphere in controlling emotion and spontaneous motor activity in mice. Adult male mice were submitted to right hemispherectomy (RH), left hemispherectomy (LH) or sham surgery (SHAM). To help the interpretation of results an addition sample of mice was submitted to unilateral suction of left frontoparietal area (LFP), right frontoparietal area (RFP) or sham surgery (CONT). Fifteen days after surgery, both the emotional reactivity and the spontaneous locomotor activity were assessed in the open field test 10 min (divided into 1 min intervals). The open field arena consisted of a polypropylene box in which the floor was divided into 16 same-sized rectangles. The total number of rectangles crossed was used as the measure of spontaneous locomotor activity. Considering that mice avoid open areas, the ambulation in the center and time spent in the central rectangles were used to assess emotional reactivity. Regarding locomotor activity, the two surgical techniques reveal asymmetries in opposite direction. The locomotor activity of LH, which increased along the test period, was higher than both RH and SHAM. In contrast, the locomotor activity of RFP which decreased along the test period was higher than both LFP and CONT. Regarding emotional reactivity, the LH group spent less time in the central area than both RH and SHAM groups. No differences were observed between LFP, RFP and CONT groups. Our results suggest that the two hemispheres contribute asymmetrically to control of emotional reactivity and to control of motor activity in mice. Similarly to what is observed in humans, the right hemisphere of mice was more involved in processing negative emotional information. Regarding locomotor hyperactivity, the differences observed between hemispherectomized and frontoparietal-lesioned mice suggest that multiple lateralized circuits (or systems) may underlie spontaneous locomotor activity.