Computations on the Nervous System: Some Results
Theodore B. Achacoso, William S. Yamamoto in AY's Neuroanatomy of C. elegans for Computation, 2022
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?
Mapping The Cerebral Cortex
Andrew P. Wickens in A History of the Brain, 2014
The better developed left hemisphere also allowed Broca to make another important claim: it was responsible for causing the majority of people to be right-handed. This bold assertion was made partly on the basis that it was known the left-hand side of the brain exercised control over the right-hand sided movements of the body, and vice versa. Although the anatomy of this system was not fully understood at the time,2 it had been established that the situation most likely occurred because fibres from higher areas of the brain, crossed in an area of the brainstem known as the pyramids, before passing on to the spinal cord. Having knowledge of this anatomy, Broca reasoned if the left hemisphere was dominant over the right hemisphere, then it would explain the preponderance of right-handedness. Similarly, left-handedness could be explained by a person having a more dominant right-sided brain. Broca stated these views formally in 1865 by declaring: The majority of men are naturally left-brained, and . . . exceptionally some among them, these people we call left-handers, are on the contrary right-brained.
Functional Specialization of the Brain (General Theoretical Framework)
Ivanka V. Asenova in Brain Lateralization and Developmental Disorders, 2018
Although single-gene models can provide good fit to phenotypic data, the fact that this putative gene has not yet been located impedes their widespread acceptance [50]. Also, recent genome-wide association studies of handedness exclude simple genetic models [10, 169]. Based on the meta-analysis of these studies, McManus et al. [135] estimated that at least forty loci, but possibly up to a hundred, are involved in determining handedness. Similar findings increase the acceptance of the multifactorial models as better suited than monogenic models to explain the development of handedness and language lateralization [152, 169].
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).
Do neurocognitive functions in cannabis induced psychosis groups differ from schizophrenia with cannabis use? A controlled cross-sectional study
Published in International Journal of Psychiatry in Clinical Practice, 2021
Raghav Shah, Abhishek Ghosh, Ajit Avasthi, Ritu Nehra, Chirag K. Ahuja, Niranjan Khandelwal
Patients registered in the clinic with a history of cannabis use and psychosis were screened for early onset, chronic, and heavy cannabis use and with a clinical diagnosis of cannabis induced psychosis or schizophrenia. These clinical diagnoses were done by a different psychiatrist after a detailed interview. Patients meeting the selection criteria were included after obtaining a written informed consent for participation in the study. The socio-demographic and the clinical details were filled in. Handedness was assessed. MINI tool was used to screen patients with any psychiatric disorder other than cannabis dependence/abuse and psychosis. PRISM tool was used to differentiate between independent (schizophrenia) and cannabis induced psychotic disorders. Subsequently the neuropsychological assessments were done in the next one or two sessions. An age, sex, education, and handedness-matched control group meeting the selection criteria was recruited separately. They were screened for any psychiatric disorders by using MINI and also screened for the presence of illicit drugs in urine chromatographic immune-assay. Neuropsychological assessments were done in one or two sessions. The clinical diagnostic interviews were done by a psychiatrist and the neuropsychological assessments were done by clinical psychologists.
Dichotic listening using Mandarin CV-words of six plosives and vowel /a/
Published in International Journal of Audiology, 2020
Xu-Jun Hu, Chi-Chuen Lau
In the current study, all participants (N = 40) were tested dichotically with both sets of Mandarin CV-words and English CV-syllables. The mean scores of correct recognition responses at the right ear (RE) and left ear (LE) were tabulated in Table 2 for each group of participants. For all participants, 65% to 75% of them showed a REA across the two sets of test materials. As handedness was generally accepted to influence the performance in dichotic listening (Knecht et al. 2000), the performance of all participants was analysed separately for the right- and left-handers. The results showed that 90% of the right-handers and 60% of the left-handers had a REA when tested with the Mandarin CV-words (Table 2). The results for the two groups of left- and right-handers could be further examined by categorising the participants with their degree of handedness. For the “slightly left-handed” participants (N = 14), the incidence rates of having a REA were high (64%−71%) when they were tested with the two sets of test materials.
Related Knowledge Centers
- Epigenetics
- Genetic Linkage
- Hand
- Heritability
- Biology
- Fine Motor Skill
- Ambidexterity
- Edinburgh Handedness Inventory
- Genome-Wide Association Study
- Locus