Training ambidexterity – A survey-based analysis on the dexterity of ophthalmologists in performing standard ophthalmic procedures

Purpose: Our study was designed to determine ophthalmologists’ dexterity in performing standard ophthalmic procedures at various levels of expertise via a structured questionnaire. Methods: A structured questionnaire was administered via the Google platform from August 20 to September 19, 2022, to assess the perspectives and preferences of ophthalmologists concerning their proficiency in using their right hand, left hand, or both hands to perform routine tasks required in the practice of ophthalmic medicine and surgery. Results: Two hundred and three participants took part in the survey. A majority (n = 162, 79.8%) of the clinicians considered themselves right?handed, nine (4.4%) considered themselves left?handed, and 32 (15.7%) considered themselves ambidextrous. Also, 86% (n = 174) of the participants considered ambidexterity an essential trait in the practice of ophthalmic medicine and surgery. The number of cataract surgeries performed had an impact on the comfort of using both hands for performing anterior vitrectomy (P < 0.001), injection of viscoelastic (P < 0.001), and toric marking (P < 0.05), but not on the performance of capsulorhexis and switching of foot pedals. The number of procedures carried out had an impact on the comfort of using both hands in gonioscopy (P < 0.001), 90 D evaluation (P < 0.001), and 20 D evaluation (P < 0.05). More years of experience had an impact on skills involving the use of both hands for slit lamp joystick usage (P < 0.05) and laser procedures (P < 0.001). Conclusion: Irrespective of a person’s handedness, trained ambidexterity in the required fields is achievable and has a significant impact on one’s ability to perform the required skill optimally and appropriately.

Morphological Analysis of Length of Human Humerus.

Estimating the height plays an important role in identifying unknown bodies. For that, the length of long bones is taken into consideration. This kind of study helps forensic, anatomical, and archaeological cases. It is also useful to orthopaedic surgeons for treatment of proximal and distal humeral fractures, and also for their reconstruction. It is also important in identification of missing persons in medicolegal investigations to define identity of skeleton. Estimation of length of long bones enables quantification of bones, and internal mechanical properties as a possible way to improve the assessment of asymmetry in the humerus. Humerus is a long bone in the upper limb that articulates with scapula at glenohumeral joint and radius and ulna at elbow joint. We wanted to determine the length of humerus and establish a relation between right and left humeri.METHODSThe current study is conducted to determine the length of humerus in a total of 40 humeri (20 right and 20 left) collected from the Department of Anatomy, Guntur Medical College, Guntur. Each humerus is measured using an osteometric board.RESULTSResults are tabulated as mean and standard deviation, and statistically compared between right and left humeri. The right humeri are comparatively bigger than the left humeri. Further results correlated with previous studies. The mean length of the right humerus was 30.05 with the standard deviation 2.339.CONCLUSIONSHumeral length shows a great variation. Asymmetry between right and left humerus should be considered to be hereditary. In many situations the full length of long bones may not be available. In such cases it was confirmed by classical osteometric techniques in which humerus even in fragmented state can be recorded in a forensic case.

Effect of surgeon's handedness on distribution of prosthesis during primary total knee arthroplasty / 中国修复重建外科杂志

Objective: To evaluate the effect of the surgeon's handedness on the distribution of prosthesis during primary total knee arthroplasty (TKA). Methods: A retrospective analysis was performed on 86 patients (100 knees) with primary TKA completed by the same right-handed surgeon between December 2016 and December 2018, including 72 cases of single knee and 14 of bilateral knees. The patients were divided into dominant group (right side) and non-dominant group (left side) according to the operating position of the surgeon and each group had 50 knees. There was no significant difference in gender, age, body mass index, disease duration, clinical diagnosis, preoperative Hospital for Special Surgery (HSS) score, and other general data between the two groups ( P>0.05). The operation time and complications were recorded in both groups. The function of knee was evaluated by HSS score. Hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA) were measured by using X-ray film of full-length lower extremity before TKA and at 2 weeks after TKA that were used to evaluate the coronal position of the prosthesis. Posterior distal femoral angle (PDFA) and posterior proximal tibial angle (PPTA) were measured by using lateral X-ray films at 3 months after operation that were used to evaluate the sagittal position of the prosthesis. Results: There was no significant difference in operation time between the two groups ( t=-1.128, P=0.262). One case of posterior tibial artery thrombosis occurred in the dominant group, and 1 case of poor healing of the incision occurred in each of the dominant group and the non-dominant group. Patients in both groups were followed up 12-34 months with an average of 22.0 months. The HSS scores at last follow-up were 87.2±4.3 in the dominant group and 86.8±5.0 in the non-dominant group. There was no significant difference between the two groups ( t=0.471, P=0.639). No complications such as periprosthetic infection, prosthetic loosening, or periprosthetic fracture occurred during follow-up. There was no significant difference in the HKA, mLDFA, and mMPTA between the two groups before and after operation ( P>0.05). The differences in the incidence of sagittal femoral prosthesis malposition and PDFA between the two groups were significant ( P0.05). Conclusion: The surgeon's handedness is one of the factors affecting the placement of the sagittal femoral prosthesis in primary TKA. The incidence of sagittal femoral prosthesis malposition could increase when the surgeon performs on the non-dominant side.

The relationship of surgeon handedness and experience on operative duration and hearing improvement in ipsilateral and contralateral otologic surgeries

@#Objective: To determine the relationship of the surgeon handedness and operative site laterality on operative duration and hearing improvement in otologic surgery, and to further explore whether this relationship may be related to surgeon experience. Methods: Design: Retrospective Cohort Setting: Tertiary Private Teaching Hospital Participants: Seventy-three (73) patients aged 18 to 65 years old who underwent primary ear surgery under general anesthesia between January 2016 and December 2019 were retrospectively divided into two groups: 39 contralateral and 34 ipsilateral. The operative durations and hearing improvements were compared using independent t-tests, with consideration of surgeon experience in years further stratifying patients. Results: There was no significant difference in operative duration, t(71) = 1.14, p = .26, between the contralateral (M = 281.95 minutes, SD = 71.82) and ipsilateral (M = 261.15, SD = 79.26) groups. This same pattern was more pronounced among surgeons with 10+ years of experience although there was also no significant difference in operative time, t(33) = 1.31, p = .19 for both ipsilateral and contralateral surgeries There was no statistically significant difference, t(36) = -0.72, p = .47, in overall mean hearing gain among patients in the contralateral (M = +2.22 dB, SD = 10.54) and ipsilateral (M = +5.12 dB, SD = 14.26) groups. Although the difference was also not statistically significant, t(16) = -1.94, p = .07 for contralateral (M = 0.00, SD = 5.43) and ipsilateral (M = +7.95 dB, SD = 11.52) procedures performed by surgeons with experience of 10 years or more, a mean hearing gain of +7 dB in the ipsilateral group compared to 0 dB in the contralateral group was notable. Conclusion: This study did not prove that regardless of surgeon experience, right-handed surgeons operating on the right ear and left-handed surgeons operating on the left ear have better ear surgery outcomes of operative duration and hearing improvement compared to right- handed surgeons operating on the left ear and left-handed surgeons operating on the right ear. Future studies on larger samples with more complete data may yet demonstrate this effect.

Experiences of Left-Handed Undergraduates in a Dental Faculty in Malaysia

@#Work environment in dentistry benefits the right-handed dental practitioners. This situation requires the left-handers to work in an adjusted position causing them discomfort and inconvenience. The aim of this study was to explore the experiences of the identified left-handed undergraduate dental students in Faculty of Dentistry, Universiti Sains Islam Malaysia (USIM) in performing dental procedures. The first phase of the study was to determine handedness of the students using the Edinburgh Handedness Inventory Questionnaire that was distributed to all the dental students. This was followed by a qualitative study using the phenomenology approach. Semi-structured interviews were conducted on left-handed students to determine their perceptions on left-handedness in performing dental procedures. The number of students interviewed was based on attainment of the saturation point. The interview was recorded and transcribed verbatim. The transcripts were analysed through coding, categorising and grouping responses into themes. Prevalence of left-handedness in this faculty was 7%. The participants were not aware of the right-handed situation when they enrolled in the faculty. This situation gave rise to psychological impact such as anxiety and stress. Although some participants were able to use their right hand for certain procedures, the dominant hand continued to be their preference. The difficulties encountered when using the non-dominant hand were grip-strength, angulation and positioning of the instruments. Dental procedures in periodontology (such as scaling, root debridement) and oral surgery (tooth extraction, incision and suturing) were found to be very challenging. They experienced muscle fatigue, reduced precision and prolonged time to complete the dental procedures. They felt that they should be given more time to adapt using the right hand under the tutelage of left-handed faculty members. Left-handed dental students faced difficulties in adapting to the right-handed situation and affect their effectiveness and efficiency. Specific activities need to be designed for left-handers to adapt to the situation under the guidance of left-handed faculty members.

Structural magnetic resonance imaging and diffusion tensor imaging study on white matter in left-and right-handed adults / 中华行为医学与脑科学杂志

Objective To explore the differences of macrostructural and microstructural and their correlations in brain white matter (WM) between left-and right-handed adults.Methods Structural magnetic resonance imaging (sMRI) and diffusion tensor imaging (DTI) were performed on twenty-three left-handed (LH) and thirty-two right-handed (RH) healthy subjects.The WM volume,fractional anisotropy (FA) and mean diffusivity (MD) were mearsured and compared between the two groups by using the voxel-based morphometry (VBM) and voxel-based analysis (VBA) methods.Results (1) LH adults showed lower WM volume than RH adults in bilateral splenium of corpus callosum (SC) (Left:x=-15,y=-57,z =13.5,t=-5.160;Right:x=18,y=-42,z=12,t=-3.654;P＜0.001).Compared with the RH adults,the FA values in WM of the left postcentral gyrus (PoCG) (x =-24,y =-46,z =54) and the above left insula (INS) (x =-36,y =-12,z =20) increased (P＜ 0.001),as well as the average FA values,the average length and number of streamlines in WM tracts increased (P＜0.05) in LH adults.Compared with the RH adults,the MD values in the right HIP (x=24,y=-34,z=-2) decreased(P＜0.001),as well as the average MD values decreased,and the average length in WM tracts increased (P＜0.05) in LH adults.(2)There was positive correlation between FA and the volume of right splenium of corpus callosum in LH and RH adults (LH:r=0.716,RH:r=0.471,P＜0.05).There was negative correlation between FA and MD in the left PoCG (LH:r=-0.769,RH:r=-0.841),left INS (LH:r=-0.775,RH:r=-0.744) and right HIP (LH:r=-0.842,RH:r=-0.742) in LH and RH adults (all P＜0.05).Conclusion There are differences in both macrostructure and microstructure of white matter in several brain regions and WM tracts between left-handed and right-handed people,and correlations between these measures were also observed.

Preferencia manual precoz: signo de alarma de accidente cerebrovascular perinatal. Serie de casos / Early handedness: Warning sign of perinatal stroke. Case series

Accidente cerebrovascular presuntamente perinatal es la expresión utilizada para los casos en los que se diagnostica un accidente cerebrovascular antiguo por sus secuelas y no por la sintomatología aguda. Muchos accidentes cerebrovasculares presuntamente perinatales tienen como primera manifestación una hemiparesia congénita, la cual se hace notoria entre el cuarto y el octavo mes de vida como preferencia manual precoz. Es por esto por lo que la preferencia manual clara y persistente desarrollada antes del año de vida debe asumirse como un signo de alarma de una probable secuela motora. En este trabajo, revisamos la historia clínica de 15 casos de accidente cerebrovascular presuntamente perinatal para evaluar la edad en la que la consulta derivó en el diagnóstico, el motivo de consulta y la edad de desarrollo de la preferencia manual.

Presumed perinatal ischemic stroke is the term used for cases in which an old stroke is diagnosed by the consequences of it and not by the acute symptoms. Many presumed perinatal ischemic strokes have congenital hemiparesis as the first manifestation, which is usually noticed between the fourth and eighth month of life as early hand preference. That is why the clear and persistent handedness developed before one year of age must be assumed as a warning sign of probable motor sequelae. In this paper we review the medical records of 15 cases of presumed perinatal ischemic stroke to assess the age at which the consultation led to the diagnosis, reason for consultation and age at development of handedness.

Toward the ‘new century’ of handedness in biology: In commemoration of the 100th anniversary of the birth of Francis Crick.

June 8th of this year marks the 100th birthday of one of the 20th century’s most influential scientists, Francis Crick (1916–2004). Together with James Watson, he discovered the double-helix structure of DNA (Watson and Crick 1953) and led the way for cracking the genetic code, laying the foundation formolecular biology. For the last 28 years of his life, he focused on human consciousness. Life and consciousness were the main themes of Francis Crick’s impressive body of work. The energy and brilliance he exuded throughout his life has been likened to the ‘incandescence of an intellectual nuclear reactor’ (Sacks 2005). The groundbreaking discovery of the ‘right-handed’ double-helix structure of DNA byWatson and Crick might also have been the dawn of the age of ‘Molecular Handedness’. The DNA of every organism on Earth forms a right-handed double helix, but the reason for this preference remains a mystery to date. Life is composed asymmetrically. Natural proteins comprise left-handed amino acids, whereas nucleic acids possess right-handed sugars. The ribosome has been shown to be a ribozyme and, therefore, the evolutionary transition from the putative ‘RNA world’ to ‘RNA/protein world’ would be a key step in the establishment of life. tRNA aminoacylation exists as a bridge between both worlds and chiral-selective nonenzymatic aminoacylation has been shown to occur depending on RNA chirality (Tamura and Schimmel 2004). Crick’s final paper with Christof Koch proposed that the claustrum may be involved in consciousness (Crick and Koch 2005). (The first draft of this manuscript was completed by Crick on July 19th, 2004, and he was still refining it in the hospital on the day he died, July 28th. It is said that he ended the first handwritten draft with the urgent words, ‘What could be more important? So why wait?’ (Ridley 2006)) The claustrum is a thin sheet of grey matter on each side of the head, located concealed between the inner surfaces of the neocortex. The functions of the brain are also asymmetrical. As generally accepted, leftbrain thinking is verbal and analytical, whereas right-brain thinking is non-verbal, intuitive, and visual. Although the claustrum is present on both sides of the brain, is the origin of the human consciousness based on ‘Brain-Handedness’? Crick maintained that the only unsolved problem is the one on consciousness and free will, which might be related to brain-handedness (Crick 1994). He tried to break the shell of scientists and paved the way for thorough investigations on consciousness. In the future, the detailed local circuit diagram of the claustrum would be elucidated, which might contribute to understanding its actual function in terms of ‘Molecular Handedness’. Francis Crick remained indomitable until his last moment. He had no interest in being famous and wealthy. His passion for science will continue to inspire scientists now and forever. Crick offers that, ‘Nature isn’t conspiring against us to make important problems difficult, so given a finite life span, aim high – go after fundamental problems.’ Let us celebrate the 100th anniversary of his birth. The ‘new century’ has the potential for profound discoveries in ‘Handedness’.

Asymmetry, handedness and auricle morphometry / Asimetría, lateralidad y morfometría de la oreja

The aims of this study were to determine various morphometric measurements of auricle, to investigate asymmetry and its relation with handedness in both sexes. Main morphometric measurements of both auricles and hand preferences were determined on 200 male and 200 female healthy university students. All measurements of the auricles were larger in males than the corresponding ones in females and all the differences except earlobe widths were statistically significant. All measurements of left and right auricles were statistically significantly different in both sexes except earlobe length in males, and distance from the highest point of the auricle to the bottom of the intertragic notch and earlobe length in females. Auricle length and distance from the highest point of the auricle to the bottom of the intertragic notch had higher values at the left side and all other measurements were larger at the right side. There was no significant difference between the measurements of the corresponding auricles of the righthanded and lefthanded subjects. All measurements were larger at the right side except auricle length and distance from the highest point of the auricle to the bottom of the intertragic notch in righthanded and lefthanded subjects and all differences except earlobe length were significantly different in righthanded subjects as in the total population but in lefthanded subjects the difference of the auricle width was not significant, either. There was an apparent asymmetry of right and left auricles of normal people in the current study which should be taken in to consideration in plastic surgeries of the external ear, designing the ear devices and forensic applications of earprints.

El objetivo de este estudio fue determinar diversas mediciones morfométricas de la oreja, para investigar la asimetría y su relación con el uso de las manos en ambos sexos. Se realizaron mediciones morfométricas de los pabellones auriculares y las manos de 400 estudiantes universitarios (200 hombres y 299 mujeres). Todas las medidas de las orejas fueron mayores en los hombres y todas las diferencias, excepto las correspondientes al ancho del lóbulo auricular, fueron estadísticamente significativas. Todas las mediciones de los pabellones auriculares izquierdos y derechos presentaron diferencias estadísticamente significativas en ambos sexos, excepto en el caso de la longitud del lóbulo auricular en los hombres, y la distancia desde el punto más alto de la oreja a la parte inferior de la incisura intertrágica en el lóbulo auricular de las mujeres. La longitud de la oreja y la distancia desde el punto más alto de la misma a la parte inferior de la escotadura intertrágica tenían valores más altos en el lado izquierdo y todas las demás mediciones fueron más elevadas en el lado derecho. No hubo diferencia significativa entre las mediciones de las orejas correspondientes a los sujetos diestros y zurdos. Todas las mediciones fueron superiores en el lado derecho, excepto la longitud del pabellón auricular y la distancia desde el punto más alto de la oreja a la parte inferior de la incisura intertrágica en sujetos diestros y sujetos zurdos, y todas las diferencias, excepto la longitud del lóbulo auricular, fueron significativamente diferentes en los sujetos diestros como en la población total, pero en sujetos zurdos la diferencia de la anchura de la oreja no fue significativa. Se encontró una aparente asimetría en las orejas derecha e izquierda de los sujetos del presente estudio que debe tenerse en consideración en las cirugías plásticas del oído externo, para el diseño de los dispositivos de audición y para su aplicación en estudios forenses de las huellas de la oreja.

Interaction between affordance and handedness recognition: a chronometric study

The visualization of tools and manipulable objects activates motor-related areas in the cortex, facilitating possible actions toward them. This pattern of activity may underlie the phenomenon of object affordance. Some cortical motor neurons are also covertly activated during the recognition of body parts such as hands. One hypothesis is that different subpopulations of motor neurons in the frontal cortex are activated in each motor program; for example, canonical neurons in the premotor cortex are responsible for the affordance of visual objects, while mirror neurons support motor imagery triggered during handedness recognition. However, the question remains whether these subpopulations work independently. This hypothesis can be tested with a manual reaction time (MRT) task with a priming paradigm to evaluate whether the view of a manipulable object interferes with the motor imagery of the subject's hand. The MRT provides a measure of the course of information processing in the brain and allows indirect evaluation of cognitive processes. Our results suggest that canonical and mirror neurons work together to create a motor plan involving hand movements to facilitate successful object manipulation.

Distances of palmar flexion creases (haustra digiti) and digital formulae in right and left handed people / Distancia de los pliegues de flexión palmar (haustra digiti) y fórmulas digitales en personas diestras y zurdas

Digital flexion creases are one of the external anatomical landmarks in the hand. In this study, we measured and compared the distances between the digital skin creases (haustra digiti) in the fingers of right-handed and left-handed individuals. We also recorded the digital formulae. No significant difference was detected between left and right-handed females and left and right handed males on distance of skin creases (p>0.05). No difference was detected on haustra digiti of the right handed females their own hands. Females who use their left hand had a significantly longer(p=0.48) distal haustra digiti segment on their right second finger than that of their left hand. However, no significant difference was detected between male individuals on their left and right hand all haustra digiti segments. The rate of hand digital formulae of 3>4>2>5>1 was 78.12% in left-handed females, 66.7% in left-handed males, 54.54% in right-handed females, and 78.57% in right-handed males. Our study has contributed to the literature on the morphological asymmetry of left-handed females.

Los pliegues digitales de flexión constituyen unos de los puntos de referencia anatómicos externos en la mano. En este estudio se midieron y compararon las distancias entre los pliegues digitales de la manos (haustra digiti) de individuos diestros y zurdos. También se registraron las fórmulas digitales. No se detectaron diferencias significativas entre mujeres zurdas y diestras y tampoco entre varones diestros y zurdos en relación a la distancia de los pliegues digitales (p>0,05). No se detectaron diferencias en el haustra digiti de las mujeres diestras. Las mujeres que utilizaban su mano izquierda tenían una diferencia significativamente mayor (p=0,48) en el segmento distal del segundo dedo, comparado con el de la mano derecha. Sin embargo, no se detectaron diferencias significativas entre los individuos de sexo masculino en sus manos izquierda y derecha, a nivel de todos los segmentos de los haustra digiti. La fórmula digital 3>4>2>5>1 se encontró en 78,12% de las mujeres zurdas, en el 66,7% de hombres zurdos, en el 54,54% de mujeres diestras, y en el 78,57% de hombres diestros. Nuestro estudio ha contribuido a la literatura sobre la asimetría morfológica de los pliegues digitales de las mujeres zurdas.

Priming effect of figures that represent external objects or human body parts

A visual stimulus (e.g., a letter, word, or object) may have a lasting effect on the processing of subsequent stimuli. The present study verified the priming effect of a figure (i.e., five-petal daisy) on manual reaction time (MRT) to another equal or different five-petal daisy. Two distinct groups were tested. One group was instructed that the five-petal daisy represented a human hand. The other group was instructed that the five-petal daisy represented a flower. The figures in the pairs of stimuli could share or not share some features such as handedness and view. In both groups, after being informed whether the five-petal daisy represented a flower or human hand, an uninformative flower was presented for 200 ms in the center of the screen. After 1000 ms, a second flower was presented in the same location until the observer responded by pressing a left or right switch. The results showed that prior presentation of the five-petal daisy affected MRT only when the figure represented a human hand. Furthermore, an opposite effect of view on MRT was found. The shorter MRT to the back (dorsal) view of the figure that represented a human hand could be attributable to a faster response to the dorsal view of a hand figure made with a prone posture of the participants' hand than to a front (palm) view. The longer MRT to the back view of the figure that represented a flower may be due to a mental rotation of the object along its vertical axis before selecting the correct response because the response was based on the position of the asymmetrical petal in the canonical front view of the daisy.

The correlation between lateralization of intracerebral hemorrhage in basal ganglia and handedness

PURPOSE: To investigate the correlation between lateralization of cerebral basal ganglia hemorrhage and handedness. METHODS: Medical records and computed tomography (CT) scans for 84 patients with primary hypertensive intracerebral hemorrhage (ICH) in basal ganglia were reviewed. Data of gender, age, handedness, and location of basal ganglia hematoma were statistically analyzed. Data of age, gender, handedness, health condition, and mean blood flow velocity (BFV) in middle cerebral arteries (MCAs) and anterior cerebral arteries (ACAs) on both sides of 114 healthy individuals were statistically analyzed. RESULTS: We found out that the patients with right basal ganglia hemorrhage were mostly left-handed, while patients with left basal ganglia hemorrhage were mostly right handed (p=0.021, r=0.251). And the mean BFV in the right MCAs of left-handed ones are relatively higher, the mean BFV in the left MCAs of right-handers are relatively higher (p=0.008, r=0.248). CONCLUSION: There 's a correlation between lateralization of cerebral basal ganglia hemorrhage and handedness.

Visibilidade dos braços afeta a preferência manual em bebês / Arms visibility affects manual preference in infants

Um aspecto de interesse sobre a formação da preferência manual humana em idades precoces é a extensão em que ela é afetada por informações aferentes. O objetivo deste estudo foi investigar o efeito da oclusão visual do braço preferido sobre a preferência manual e desempenho motor em bebês. Participaram cinco bebês com cinco meses de idade, que realizaram alcances com visão plena ou oclusão visual do braço preferido. O desempenho motor foi avaliado por meio de medidas cinemáticas. Os resultados indicaram que a oclusão visual induziu redução da frequência de alcances unimanuais com o braço ocluído durante e imediatamente após a oclusão visual. Oclusão visual não alterou o desempenho motor. Estes resultados indicam que a formação da preferência manual durante o desenvolvimento motor é afetada pela disponibilidade de informação visual dos braços, embora os bebês pareçam ter pouca capacidade de usar a visão para controle motor.

An interesting aspect about formation of human manual preference in early ages is the extent to which it is affected by afferent information. This study aimed at investigating the effect of visual occlusion of the preferred arm on manual preference and motor performance in infants. Five 5-month-old infants performed reaching movements under full vision or occlusion of their preferred arm. Motor performance was assessed through kinematic measures. Results indicated that visual occlusion led to reduction of frequency of unimanual reaches using the visually occluded arm. Visual occlusion did not impair motor performance. These results indicate that formation of manual preference during motor development is affected by availability of visual afference of the arms, although infants seem to have reduced capacity to use vision for motor control.

The Neural Basis of Optimism and Pessimism

Our survival and wellness require a balance between optimism and pessimism. Undue pessimism makes life miserable; however, excessive optimism can lead to dangerously risky behaviors. A review and synthesis of the literature on the neurophysiology subserving these two worldviews suggests that optimism and pessimism are differentially associated with the two cerebral hemispheres. High self-esteem, a cheerful attitude that tends to look at the positive aspects of a given situation, as well as an optimistic belief in a bright future are associated with physiological activity in the left-hemisphere (LH). In contrast, a gloomy viewpoint, an inclination to focus on the negative part and exaggerate its significance, low self-esteem as well as a pessimistic view on what the future holds are interlinked with neurophysiological processes in the right-hemisphere (RH). This hemispheric asymmetry in mediating optimistic and pessimistic outlooks is rooted in several biological and functional differences between the two hemispheres. The RH mediation of a watchful and inhibitive mode weaves a sense of insecurity that generates and supports pessimistic thought patterns. Conversely, the LH mediation of an active mode and the positive feedback it receives through its motor dexterity breed a sense of confidence in one's ability to manage life's challenges, and optimism about the future.

Lateralization of Cognitive Functions in Aphasia after Right Brain Damage

PURPOSE: The lateralization of cognitive functions in crossed aphasia in dextrals (CAD) has been explored and compared mainly with cases of aphasia with left hemisphere damage. However, comparing the neuropsychological aspects of CAD and aphasia after right brain damage in left-handers (ARL) could potentially provide more insights into the effect of a shift in the laterality of handedness or language on other cognitive organization. Thus, this case study compared two cases of CAD and one case of ARL. MATERIALS AND METHODS: The following neuropsychological measures were obtained from three aphasic patients with right brain damage (two cases of CAD and one case of ARL); language, oral and limb praxis, and nonverbal cognitive functions (visuospatial neglect and visuospatial construction). RESULTS: All three patients showed impaired visuoconstructional abilities, whereas each patient showed a different level of performances for oral and limb praxis, and visuospatial neglect. CONCLUSION: Based on the analysis of these three aphasic patients' performances, we highlighted the lateralization of language, handedness, oral and limb praxis, visuospatial neglect and visuospatial constructive ability in aphasic patients with right brain damage.

Efeito da velocidade do estímulo no desempenho de uma tarefa de antecipação-coincidência em destros e canhotos / Stimulus velocity effect on the performance of a coincidence-anticipation task of right- and left-handers

Destros e canhotos diferem quando comparados em algumas tarefas motoras, parecendo os canhotos usufruir de alguma vantagem em tarefas visuo-motoras. Neste estudo foi analisado, em cada grupo de preferência manual, o efeito da velocidade do estímulo, do sexo e da mão de execução no desempenho de uma tarefa simples de antecipação-coincidência. Participaram 12 destros e 12 canhotos de ambos os sexos, estudantes universitários de Desporto. Empregou-se o "Bassin Anticipation Timer" para avaliar a capacidade de antecipação-coincidência em três velocidades: 268 cm/s, 402,3 cm/s e 536,4 cm/s (6, 9 e 12 mph, respectivamente). Os sujeitos executaram a tarefa tanto com a mão preferida como com a mão não preferida. Principais resultados: 1) apenas os destros foram afetados pela variável velocidade do estímulo, apresentando antecipação das respostas e maior variabilidade na velocidade 268 cm/s, enquanto nas velocidades 402,3 cm/s e 536,4 cm/s as respostas foram enviesadas no sentido do atraso da resposta e com variabilidade menos acentuada na velocidade mais alta; 2) o sexo teve um efeito significativo apenas nos canhotos, sendo o sexo masculino mais preciso e menos enviesado nas suas respostas do que o sexo feminino; 3) a assimetria manual manifestou-se apenas nos canhotos na velocidade de 268 cm/s e no Erro Variável. Concluímos que cada grupo de preferência manual parece comportar-se de forma diferenciada em tarefas perceptivas de Antecipação-Coincidência onde a velocidade do estímulo é manipulada.

Right- and left-handers differ when compared in some motor tasks, and left-handers enjoy some advantage over right-handers in visuo-motor tasks. In this study we intend to analyze the effect of stimulus speed, in a simple coincidence-anticipation task, depending on handedness. Twelve right-handers and twelve left-handers of both sexes, students of Physical Education, participated in this study. The Bassin Anticipation Timer was used to evaluate the coincidence-anticipation ability at three different and random velocities: 268 cm/s, 402.3 cm/s e 536.4 cm/s (6, 9 e 12 mph, respectively). The subjects were evaluated performing the task with the preferred hand and non-preferred hand. The results revealed that: 1) only right-handers were affected by the variable stimulus speed, anticipating responses and being more variable at 268cm/s, while at 402.3 cm/s and 536.4 cm/s responses were late; moreover they were less variable at 536.4cm/s; 2) sex as a main factor was significant only in the left-handed group, males being more accurate and less biased in their responses than females; 3) manual asymmetry was only apparent in the left-handed group at the 268cm/s and in the variable error. The perceptual component of the task seems to be crucial in distinguishing right-handers and left-handers where the speed of the stimulus is manipulated.

Study of handedness and facial asymmetry in teenagers.

Aim of this study was to investigate the distribution and frequencies of facial asymmetry, handedness, arm folding, and digital interlocking. It was also intended to study the correlation between the different functional traits. 200 healthy co-operative volunteers between the age group of 13 & 15 years were selected for the study. Subjects with any deformity of upper limbs & those with the history of injury to vii cranial nerve were excluded from the study. Personal data was collected from the subjects, by providing them a questionnaire, in which they also mentioned whether any of the family members was left handed, if so, their relation to the student. Various tests were conducted to determine handedness & the asymmetry in the face, arm folding, & digital interlocking. Data collected was subjected to tabulation & was subjected to statistical analysis & tested for statistical significance. Chi square test was used with paired T test. Male subjects exhibit a highly significant correlation between handedness and digital interlocking (P<0.01). Female subjects show a highly significant correlation between handedness and digital interlocking (P<0.005). Highly significant correlation exists between digital interlocking and arm folding in both sexes (P<0.0001). Both males and females, exhibit a significant correlation between handedness and vertical wrinkling of the forehead (P<0.05), as well as functional preference of other groups of facial musculatures i.e. winking (P<0.05), and lateral movement of angle of mouth (P<0.01). No significant correlation was seen between facial musculature and sex of the individual. Females showed higher preponderance of left handedness. Significant correlation exists between handedness and the following parameters; digital interlocking, and facial asymmetry.

Sobre a relação entre filogenia e ontogenia no desenvolvimento da lateralidade na infância / The relationship between phylogeny and ontogeny in the development of infant laterality

A lateralidade humana tem sido concebida como sendo predominantemente o resultado de fatores filogenéticos do desenvolvimento humano, enquanto que apenas importância secundária tem sido atribuída à interação indivíduo-ambiente. Neste estudo é apresentada uma revisão crítica da literatura com indicadores da influência de fatores filo e ontogenéticos no desenvolvimento da lateralidade, com particular ênfase aos primeiros anos de vida. A partir dos resultados discutidos, propomos que a lateralidade humana é um processo dinâmico, com efeitos marcantes das experiências sensório-motoras lateralizadas sobre a preferência manual e assimetrias interlaterais de desempenho motor.

Human laterality has been conceived as resulting, predominantly, from phylogenetic factors in human development, whereas individual-environment interaction is thought to play only a minor role. This study aims at presenting a critical review of literature showing evidence of the effect of phylogenetic and ontogenetic factors on the development of laterality, with particular emphasis on the first years of life. From the results presented, we propose that human laterality is a dynamic process, with sharp effects of lateralized sensorimotor experiences over manual preference and interlateral asymmetry of motor performance.

Left-right judgment of haptic stimuli representing the human hand

The handedness recognition of visually perceived body parts engages motor representations that are constrained by the same biomechanical factors that limit the execution of real movements. In the present study, we used small plastic cutouts that represented the human hand to investigate the properties of mental images generated during their haptic exploration. Our working hypothesis was that any handedness recognition task that involves body parts depends on motor imagery. Forty-four blindfolded, right-handed volunteers participated in a handedness evaluation experiment using their index finger to explore either the back or palm view of a haptic stimulus that represented the human hand. The stimuli were presented in four different orientations, and we measured the subjects' response times. Our results showed that stimulus configurations that resemble awkward positions of the human hand are associated with longer response times (p < .006), indicating that the haptic exploration of stimuli that represent body parts also leads to motor imagery that is constrained by biomechanical factors