Sentence:  Moreover , the dominance in parasympathetic action ( with reciprocal inhibition of the sympathetic ) at the hypothalamic level induces , by its peripheral action , the autonomic symptoms of sleep and , by its action on the <WSD>cortex</WSD> , a lessening in the reactivity of the sensory and motor apparatus of the somatic nervous system . 
Meaning of the word marked with <WSD> tags:  the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum