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Computations on the Nervous System: Some Results
Published in Theodore B. Achacoso, William S. Yamamoto, AY's Neuroanatomy of C. elegans for Computation, 2022
Theodore B. Achacoso, William S. Yamamoto
Reordering the neurons in the matrix, so that all left-sided neurons come first in ganglionic order, and right sided neurons, last, with the unpaired neurons in the middle in roughly anteroposterior order (Figure 1.15), displays right-left symmetry of the connections. Commissural connections are emphasized in the right upper submatrix (RUS, left to right connections) and in the left lower submatrix (LLS, right to left connections). Homolateral connections are in the left upper and right lower submatrices. As in Figure 1.13, short tracts are near the main diagonal, and long tracts are seen farther away from it. Right and left neuronal asymmetry contrasts with the dorsoventral symmetry of the musculature and innervation. By virtue of surface forces in the film of water on the particles of soil on which they live, these nematodes live in a planar environment. Their locomotion is constrained by their dorsoventral muscular symmetry. This asymmetry of the sensory environment may be impressed upon the other sensory and logical processes. One thinks of the flounder, which, having exchanged its right and left for belly and back, respectively, has also moved both eyes to what was once the left side of the body (most of the time). Perhaps, the flounder adapts to the flattening of an otherwise three dimensional world as it matures to live on the ocean bottom. The study of genetic mapping may lend insight into this issue, the evolution of handedness. Does handedness arise from neural asymmetry determined by genetic or embryogenic circumstance?
Motor Aspects of Lateralization: Evidence for Evaluation of the Hypotheses of Chapter 8
Published in Robert Miller, Axonal Conduction Time and Human Cerebral Laterality, 2019
The scheme outlined in Chapter 8 envisages that representations of left hemisphere-lateralized motor function are acquired by a process of learning. This is envisaged to be especially slow, because it involves selection from a wide range of chance combinations of motor fragments those which happen to match prior specifications. Thus a repertoire of modelled motor programs is slowly built up, by a process which is much more protracted than acquisition by direct instruction from the environment, the more usual process of learning. Empirically it is undoubtedly true that these phylogenetically “new” forms of motor co-ordination, using hands, arms and vocal apparatus require long stages of learning: Speech and written language require years for perfection. Other forms of manual dexterity also develop over a period of years. For instance, the percentage of children showing pronounced right handedness increases considerably from age 2 to 8 years (Satz, 1988; Gudmundsson, 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).
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.
Handedness as a neurodevelopmental marker in schizophrenia: Results from the FACE-SZ cohort
Published in The World Journal of Biological Psychiatry, 2022
Jasmina Mallet, Ophélia Godin, Yann Le Strat, Nicolas Mazer, Fabrice Berna, Laurent Boyer, Delphine Capdevielle, Julie Clauss, Isabelle Chéreau, Thierry D’Amato, Julien Dubreucq, Sylvain Leigner, Pierre-Michel Llorca, David Misdrahi, Christine Passerieux, Romain Rey, Baptiste Pignon, Mathieu Urbach, Franck Schürhoff, Guillaume Fond, Caroline Dubertret
The neurodevelopmental hypothesis of schizophrenia (SZ) is supported by various data including potentially increased non-right handedness (NRH) and mixed-handedness in this population. Brain asymmetry, language, and handedness are believed to be very closely tied, although imperfectly (Rodriguez and Waldenström 2008). Handedness is thus a simple way of capturing atypical lateralisation (Barrantes-Vidal et al. 2013) and has been recently shown to be determined in part by both genetic and biological pathways (Satz and Green 1999; Brandler and Paracchini 2014). The frontostriatal monoaminergic circuits implicated in the occurrence of SZ are also lateralised (Klimkeit and Bradshaw 2006). Various hypotheses have been put forward to explain brain asymmetry such as the left hemisphere lag, the left hemisphere being especially vulnerable to insults, and frank differences in hemispheric specialisation (Geschwind and Galaburda 1985). NRH could result from an acute neurodevelopmental impairment (van Dyck et al. 2012; Ho et al. 2017; Wang B et al. 2018) associated with epigenetic processes (due to biological challenges like inflammation/infections for example) that, in addition to genetic factors, are likely to contribute to the SZ pathogenesis. It may thus be reasonably hypothesised that NRH, including mixed-handedness, could be an easy clinical factor to explore abnormal cognitive functions due to brain lateralisation issues (Webb et al. 2013).
Are the Predictions of the Dynamic Dominance Model of Laterality Applicable to Children?
Published in Developmental Neuropsychology, 2020
Alexandre Jehan Marcori, Luis Augusto Teixeira, Juliana Bayeux Dascal, Victor Hugo Alves Okazaki
As hypothesized by Sainburg and Kalakanis (2000), an expected consequence of lateral specialization for motor control functions is the development of lateral preference. Some research suggested that handedness is consolidated by the age of 5–9 years old (Fagard, 2013; Gabbard, 1993; Gaillard & Satz, 1989; McManus et al., 1988), while other results indicated that consistent-lateralized behavior can be observed already at the age of 12 months, depending on the individual trajectory of handedness development (Campbell, Marcinowski, & Michel, 2017; Michel, Babik, Sheu, & Campbell, 2014). In this regard, an early manifestation of more linear movements of the right hand toward a spatial target could be assumed to represent an important factor in the development of manual preference, potentially biasing hand selection in manipulative skills. As Przybyla, Coelho, Akpinar, Kirazci, and Sainburg (2013) have shown, hand selection can be predicted from intermanual performance asymmetries (see also Teixeira & Okazaki, 2007). While our analysis is unable to confirm the relationship between handedness development and hemisphere specialization manifestation, the results are in line with previous literature by showing specialized dynamic control mechanisms with the right hand in early childhood.