Objective The ability to encode the intensity of a painful stimulus is an essential component of the neural processes involved in pain perception.It is well accepted that stimulus intensity is encoded by sensory pathways.However, the role of the affective pathway in the processing of noxious stimulus intensity is unclear.In this study, we hypothesized that neurons in the medial pathway may also play a role in noxious stimulus intensity coding, and that spike counts may best convey information related to stimulus intensity.Methods Multichannel single-unit recordings were used to investigate the activity of individual neurons and neuronal ensembles in the rat brain following application of painful laser stimuli to the paw.Four brain regions were monitored, including two that are associated with the lateral sensory pain pathway, namely the ventral posterior lateral thalamic nucleus (VPL) and the primary somatosensory cortex (SI), and two that are associated with the medial pathway involved in affective aspects of pain perception, namely the medial dorsal (MD) thalamic nuclei and the anterior cingulate cortex (ACC).Neuron number coding, firing rate coding, and spike count coding were examined in this study.Results Our results show that neurons in the affective pathway can encode noxious stimulus intensity, and this capability appears to be comparable to that in the sensory pathway.We also found that optimal intensity discrimination depends on the collective contributions of both pain pathways.Conclusion This study draws attention to the role of the affective pain pathway in the processing of noxious stimulation.Additionally, we provide evidence that spike count coding may be the most reliable method for examining sensory processing in the brain.