Discriminative pain perception

Any noxious stimulus will activate both lamina I and lamina V cells (stimuli exciting only lamina V cells are perceived as innocuous). The Lamina I cells signal pain, but because they have large receptive fields, and relay to posterior and reticular thalamic nuclei which do not have precise topographic projections to the cortex, they cannot restrict it well. The localization of painful stimuli depends on the simultaneous firing of lamina V cells, that project in somatotopic fashion to the ventroposterolateral thalamus and so to the primary somatosensory cortex.