Activation maps measuring the degree of hemispheric lateralisation during a language task

Functional MRI (fMRI) activation maps measuring the degree of hemispheric lateralisation during a language task in 297 subjects, 153 of whom were left-handed. Researchers divided these subjects into three categories: those who presented a strong left lateralisation of cerebral activity (84%); those who showed a distribution of activity in both hemispheres (12.5%) and those who presented a strongly lateralised activity on the right (3.5%). Our two cerebral hemispheres play different roles in our intellectual faculties; certain cognitive functions are hosted preferentially by one or other of the two hemispheres. Researchers assessed the cognitive abilities of the subjects by means of twelve tests designed to quantify most aspects of cognition. Subjects showing no hemispheric dominance for language scored significantly lower than subjects in whom one hemisphere was dominant. This result confirmed the advantage of the division of tasks between the hemispheres and the benefit of specialisation.