Atypical left-handers use right brain hemisphere for language and left for inhibition, study finds

Approximately 10% of the human population is left-handed. Among them, one in five exhibits a peculiar brain phenomenon known as atypical language lateralization. While most people attribute their language capability to their left hemisphere, this atypical group of left-handers utilizes their right hemisphere to speak. One of the oldest questions in neuroscience is how this phenomenon impacts brain organization and human behavior.

The Neuropsychology and Functional Neuroimaging Group at the Universitat Jaume I in Castellón, led by researcher César Ávila, recently published a study in eLife providing evidence that language and inhibitory function (typically lateralized in the right hemisphere) are programmed to be located in different hemispheres. It also supports the hypothesis that has linked the presence of atypical brain lateralization with some neurodevelopmental disorders such as schizophrenia, dyslexia, or the autistic spectrum.

The study aimed to understand how inhibitory function (the ability to control certain impulses or automatic responses and adjust them to better fit the situation) is organized in these atypical left-handers with language in the right hemisphere. The results reveal that in these individuals, the left hemisphere takes over inhibitory function, contrary to the norm. This phenomenon extends beyond the cerebral cortices, involving both subcortical circuits and connectivity between hemispheres through the corpus callosum (with greater white matter).

The results also demonstrate that atypical hemispheric specialization is associated with poorer cognitive performance in the linguistic domain, and furthermore, is linked to preclinical traits of some neurodevelopmental disorders among the healthy population. However, the research team has not found direct evidence of a relationship between brain organization and cognitive efficiency and performance during inhibition.

The study involved 86 participants selected after an assessment to determine which hemisphere they used for language. Of these, 50 had typical lateralization, meaning the left hemisphere predominated, and 36 showed atypical lateralization (right). None of the participants were right-handed, and although there were different bilingual conditions, no significant differences were found in the results because of this.

This line of research is one of the constants of the Neuropsychology and Functional Neuroimaging team, which seeks to understand how the brain of this population sector works, showing a predisposition to talent and creativity on one hand, but also to neurodevelopmental disorders such as epilepsy, dyslexia, or autism on the other. They investigate aspects such as whether there is a relationship between education as if one were right-handed and learning problems or factors that increase the likelihood of having atypical language lateralization, such as musical training.

Their future objective is to study these processes in left-handed children, adolescents, and teenagers to impact their education and prevent learning and developmental disorders.

These findings could have significant implications in the study of neonatal injuries that facilitate left-handed development or when evaluating the consequences of brain injuries in the left-handed population. They would also be of interest in the study of brain plasticity and development; language and cognitive control; and in cognitive rehabilitation procedures in patients with psychiatric disorders seemingly associated with a higher prevalence of being left-handed.

Provided by
Universitat Jaume I

Approximately 10% of the human population is left-handed. Among them, one in five exhibits a peculiar brain phenomenon known as atypical language lateralization. While most people attribute their language capability to their left hemisphere, this atypical group of left-handers utilizes their right hemisphere to speak. One of the oldest questions in neuroscience is how this phenomenon impacts brain organization and human behavior.

The Neuropsychology and Functional Neuroimaging Group at the Universitat Jaume I in Castellón, led by researcher César Ávila, recently published a study in eLife providing evidence that language and inhibitory function (typically lateralized in the right hemisphere) are programmed to be located in different hemispheres. It also supports the hypothesis that has linked the presence of atypical brain lateralization with some neurodevelopmental disorders such as schizophrenia, dyslexia, or the autistic spectrum.

The study aimed to understand how inhibitory function (the ability to control certain impulses or automatic responses and adjust them to better fit the situation) is organized in these atypical left-handers with language in the right hemisphere. The results reveal that in these individuals, the left hemisphere takes over inhibitory function, contrary to the norm. This phenomenon extends beyond the cerebral cortices, involving both subcortical circuits and connectivity between hemispheres through the corpus callosum (with greater white matter).

The results also demonstrate that atypical hemispheric specialization is associated with poorer cognitive performance in the linguistic domain, and furthermore, is linked to preclinical traits of some neurodevelopmental disorders among the healthy population. However, the research team has not found direct evidence of a relationship between brain organization and cognitive efficiency and performance during inhibition.

The study involved 86 participants selected after an assessment to determine which hemisphere they used for language. Of these, 50 had typical lateralization, meaning the left hemisphere predominated, and 36 showed atypical lateralization (right). None of the participants were right-handed, and although there were different bilingual conditions, no significant differences were found in the results because of this.

This line of research is one of the constants of the Neuropsychology and Functional Neuroimaging team, which seeks to understand how the brain of this population sector works, showing a predisposition to talent and creativity on one hand, but also to neurodevelopmental disorders such as epilepsy, dyslexia, or autism on the other. They investigate aspects such as whether there is a relationship between education as if one were right-handed and learning problems or factors that increase the likelihood of having atypical language lateralization, such as musical training.

Their future objective is to study these processes in left-handed children, adolescents, and teenagers to impact their education and prevent learning and developmental disorders.

These findings could have significant implications in the study of neonatal injuries that facilitate left-handed development or when evaluating the consequences of brain injuries in the left-handed population. They would also be of interest in the study of brain plasticity and development; language and cognitive control; and in cognitive rehabilitation procedures in patients with psychiatric disorders seemingly associated with a higher prevalence of being left-handed.

Provided by
Universitat Jaume I