How do the functions of the neospinothalamic and paleospinothalamic tracts differ?
The lateral spinothalamic tract (neospinothalamic tract) ascends to the thalamus and cortex with few synaptic connections.
Therefore, sharp pain and the avoidance response can be evoked due to the rapid transmission and perception of pain. In contrast, the dorsomedial thalamic tract (paleothalamic tract) synapses at multiple locations, including the recticular activating system, before reaching the thalamus and limbic system.
Transmission along the paleothalamic system is slow and associated with more indolent visceral-autonomic and emotional/behavioral responses.
Yalsh TL, Wiese AJ: Survey of systems involved in nociceptive processing. In Deer TR, Leong MS, Buvanendran A, et al. (eds): Comprehensive treatment of chronic pain by medical, interventional, and integrative approaches. New York: Springer, 2013, pp 3-21.