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Summary, Synopsis of Predictions, and Concluding Remarks
Published in Robert Miller, Axonal Conduction Time and Human Cerebral Laterality, 2019
Since 1978, quite a variety of examples of hemispheric morphological asymmetry (or related functional asymmetry) in several mammalian species have been reported. Bradshaw (1991) reviewed this subject. In rodents, the right hemisphere appears to be larger than the left (as in humans), and similar asymmetry, though less well documented has been found in mouse, rabbit, cat (Kolb et al., 1982) as well as in dogs and dolphins (review of Bradshaw, 1991). In rats the cortex is thicker on the right in most regions, the length, height and wet weight of the hemispheres is also larger on the right, although subcortical width is not asymmetrical (Kolb et al., 1982). In primates the right frontal lobe and the left occipital lobe appear to be larger than on the opposite sides (as in humans). Emotional responses appear to be dealt with more in the right than the left hemisphere of rats (as in humans). Split-brain monkeys can discriminate faces of monkeys better with the right than the left hemisphere (corresponding to the asymmetry found in humans). Monkeys have a left hand superiority in discriminating tactile shapes (as in humans). Several species of monkey are known to favour the right hand in complex manipulations (perhaps corresponding to human right handedness). In rhesus monkeys, the left face begins to display facial expression at an earlier age than the right face (Hauser, 1993).
Electrode placement
Published in Alan Weiss, The Electroconvulsive Therapy Workbook, 2018
It is estimated that 70% of people are left hemisphere-dominant, resulting in right-handedness. In the 30% who are left-handed, 70% of this group are lateralised for language functions in a manner similar to right-handed people (Bryden, 1982). Of the remainder, 15% have bilateral representation of language, with the other 15% being truly right hemisphere-dominant (Bryden and Steenhuis, 1991; Ramussen and Milner, 1977).
Developmental Dyslexia
Published in Ivanka V. Asenova, Brain Lateralization and Developmental Disorders, 2018
Subjects’ handedness is one of the factors controlled in the studies using dichotic listening paradigm. Right-handedness particularly is among the participants’ selection criteria. That was not made in the present study for two reasons: first because left-handedness and mixed-handedness are among the factors connected to the occurrence of dd [6, 71, 72, 157], and second because it is possible that this factor is connected only to a particular type of dd.
NeurHistAlert 26
Published in Journal of the History of the Neurosciences, 2023
Frank W. Stahnisch, Michel C. F. Shamy
This substantial history of science thesis by Tabea Cornel delves into the problem of left-right-handedness and the concept of neurolocalizationism and brain functioning over the past 150 years. It principally reviews neuroscientific classification practices for diagnostic and research purposes in relation to handedness organization in the human brain. Cornel emphasizes the insights that earlier English-, French-, and German-speaking neurologists and psychologists in the nineteenth and twentieth centuries had provided. As early as 1865, Paul Broca (1824–1880) in Paris had advanced the view that the human language area would be localized in the left hemisphere of the brain. The thesis follows some well-entrenched views about several biases and misperceptions engrained in the anatomic, physiological, pathological, and inheritance-based concepts of left-right-handedness as an alleged criterion of psychological and intellectual superiority in human populations. While the thesis rightly points to the emerging epistemic inconsistencies, based on the often incompatible scientific views of brain functioning and structural cortical localizationism, discussions of critical intra- scientific approaches from systems neurophysiology, Gestalt psychology, and neuro- rehabilitation disciplines would have been valuable, as during the twentieth century they also provided alternative epistemic interpretations and gradually led to a revision of the often derogative applications of handedness criteria in the disability, mental health, and immigration communities in the latter decades of the twentieth century.
Hair Whorl Direction: The Association with Handedness, Footedness, and Eyedness
Published in Developmental Neuropsychology, 2020
Murat Çetkin, Selin Bayko, Tunç Kutoğlu
The human body demonstrates asymmetric features in a structural and functional sense. Handedness, footedness, and eyedness constitute the functional symmetric differences in humans. Handedness (hand preference) is an evident marker of cerebral dominance (Misra, 2007). Handedness, defined as an individual’s preference to use one of his/her hands more than the other hand in special tasks, may have a natural or biological basis (Ghayas & Adil, 2007). In humans, right-handedness is more common than left-handedness. This is a universal reality that does not depend on racial and geographical variables (McManus, 2009). Another parameter considered in the representation of cerebral dominance is footedness (foot preference) (Elias, Bryden, & Bulman-Fleming, 1998; Kalaycıoğlu, Kara, Atbaşoğlu, & Nalçacı, 2008). Footedness is the preference of one lower limb more than the other one in a motor activity (Grouios, Hatzitaki, Kollias, & Koidou, 2009). Footedness was reported to be less affected by social training (Gabbard & Iteya, 1996). The functional mechanism and neural origin of eyedness (ocular dominance) is relatively less known. The brain receives image-related impulses from the binocular visual field. However, an individual usually prefers to use one of his/her eyes more than the other one in certain tasks. This tendency is called eyedness and while performing certain tasks that require the use of one eye, those with right eye dominance prefer to use their right eyes, and those with left eye dominance prefer to use their left eyes (Maples, 2002; Suttle et al., 2009).
Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements
Published in Journal of Motor Behavior, 2019
An additional layer that deserves consideration is how directional components of handedness relate to bimanual performance in conjunction with the degree of handedness. Although literature advocates for the use of degree of handedness over direction, these components may need to be investigated in conjunction with one another. Moreover, when examining callosal size, no significant differences were observed in callosal thickness between left and right handers; however, when considering degree of handedness in addition to direction, left handers, as one group including consistent and inconsistent, displayed large corpus callosums similar to inconsistent right-handers (Josse, Seghier, Kherif, & Price, 2008; Luders et al., 2010). Results provide evidence that inconsistent left handedness, inconsistent right handedness, and consistent left handedness may all be neurologically similar differing from consistent right handedness. Similar patterns have been observed with regard to language lateralization, which a function frequently studied in relation to handedness. Specifically, the lateralization of language is similar in consistent left handers and inconsistent right handers (Szaflarski et al., 2002). Given this pattern, it may be of value to combine inconsistent right handers with both consistent and inconsistent left handers into one group to statistically compare to consistent right handers. To the authors knowledge, assessing differences in performance on bimanual coordination tasks and the presence of the “bimanual advantage” between this combined group and consistent right handers has not been reported.