URABE and Tsubokawa1 investigated the effect of unilateral vs bilateral lesions in the centrum medianum in human subjects suffering from intractable pain. They observed that if the pain was well localized and exhibited laterality, then unilateral lesions (placed contralateral to the site of the reported pain) were effective in providing relief. In contrast, if the pain was diffuse and had no laterality, then bilateral lesions were necessary in order to provide pain relief.
In a previous report2 we have stated that lesions in or about the nucleus parafascicularis (Pf), centrum medianum (CM), and other contiguous thalamic nuclei were effective in abolishing an escape reaction elicited by stimulation of the tooth pulp in the cat. However, in this study all lesions were made bilaterally.
In view of the report by Urabe and Tsubokawa,1 it seemed that a comparison of the effect of unilateral vs bilateral lesions on