The sensory-limbic model of pain memory: Connections from thalamus to the limbic system mediate the learned component of the affective dimension of pain

Abstract

Stimulation in the human somatosensory thalamus, posteroinferior to the human principal sensory nucleus (ventralis caudalis), has been reported to reproduce previously experienced pain associated with a strong affective dimension. In these reports, pains with a strong affective dimension were reproduced by stimulation within and posteroinferior to the core (posteroinferior region) of the ventralis caudalis only in patients with previous experience of such pain. Similar vivid experiential responses have been reported with stimulation over the parasylvian cortex. Thus, the connection from the posteroinferior region to the secondary somatosensory cortex and insular cortex may explain the reproduction, by thalamic stimulation, of pain with a strong affective dimension. The secondary somatosensory and insular cortex are involved in nociceptive pathways that have similar characteristics to cortical areas known to be involved in visual memory through corticolimbic connections. Therefore, stimulation-evoked pain with a strong affective dimension may be explained by a model in which limbic structures are altered by previous experience of pain with a strong affective dimension and triggered, through thalamic corticolimbic connections, to reproduce that pain. This sensorylimbic model could form the framework for testable hypotheses regarding the anatomic and physiologic substrates of learning processes involved in the affective dimension of pain.