The reticular formation receives much afferent input, both from the spinal cord and from other parts of the brain. The lateral column of the reticular formation is an important reception area for incoming sensory and other afferent inputs; inputs from collaterals arising from ascending spinal sensory tracts and from spinoretic-ular tracts are especially prominent. The lateral column is made up of nuclei consisting chiefly of small cells, including the parvicellular nucleus in the medulla and pons and the parabrachial nucleus in the pons and midbrain.