Some quantitative measures of structural asymmetry in fields 41 and 22 of the human auditory cortex.

The aim of the present work was to perform a quantitative study of the cytoarchitectonic features of cortical fields 41 and 22 in the left and right hemispheres of the human brain. Studies addressed frontal sections of the brains of 10 subjects (right-handers) aged 29-59 years, stained with cresyl violet by the Nissl method; sections were 20 microm thick. The following quantitative parameters were measured: volume of field, thickness of cortex, and neuron field profile area. The results showed that field 22, which is the associative component in the processing of speech stimuli, was characterized by left-hemisphere asymmetry of measures of cortical volume, cortical thickness, and the neuron field profile area. Field 41, which is a projection field involved in the reception of sound stimuli, was characterized by right-hemisphere asymmetry for measures of neuron field profile area but no asymmetry in favour of either hemisphere for cortical volume or cortical thickness.