Areas of Cerebral Cortex concerned with Vibration Sense
The primary somatosensory cortex (SI) is located in the post central gyrus, with the lower limb being represented on the medial surface of the hemisphere, and the head placed laterally near the Sylvian fissure. The pathways between sensory receptors and SI are modality specific and are anatomically and electrophysiologically distinct. As a result the somatosensory cortex is divided into strips, contain neurones that respond specifically to afferent inputs from
The columns of neurones within these strips are modality specific.
- rapidly adapting skin receptors,
- slowly adapting skin receptors,
- muscle and tendon afferents, and
- joint receptors
Brodmann's cytoarchitectonic map of the cerebral cortex was the result of an analysis of the size and shape of cortical neurones. There is a strong correlation between structure and function in the cortex, and the somatosensory cortex is in Brodmann's areas 1,2 and 3a + 3b. These represent parallel strips along the length of the post-central gyrus.
The different Brodmann areas within the post central gyrus are strips in parallel with the central sulcus, and the functional aspect of each strip is that it is modality specific - i.e. it handles information from only only one class of sensory receptor.
Pressure, flutter, and vibratory stimuli activate spatially distinct cortical columns in area 1. Area 3a handles information from muscle receptors; areas
3b and 1 handle the input from rapidly and slowly adapting receptors in skin, and columns of neurones within these areas preserve the modality specificity - i.e. there is no mixing of the modalities of sensory input within these columns.
In area 2, the input is from joint receptors: here the largest areas of cortex (number of cortical columns) are given to the position of large joints (hips, knees, etc) and smaller areas are concerned with smaller joints.