Distribution of the sacral neurones of origin of the ascending spinal tracts with axons passing through the lateral funiculi of the lowermost thoracic segments: an experimental HRP study in the cat

Brain activity associated with painfully hot stimuli applied to the upper limb: a meta-analysis

The capacity of pain to alert against potential injury or focus attention on damaged tissue is enhanced by the intrinsically aversive nature of the experience. Finding methods to relieve pain will ultimately be facilitated by deeper understanding of the processes that contribute to the experience, and functional brain imaging has contributed substantially toward that end. An impressive body of literature has identified a distributed network of pain-related activity in the brain that is subject to considerable modulation by different stimulus parameters, contextual factors, and clinical conditions. The fundamental substrates of the pain network are yet to be distilled from the highly variable results of studies published thus far. Qualitative reviews of the pain-imaging literature have been contributory, but lack the greater surety of quantitative methods. We employ the activation likelihood estimation (ALE) meta-analytic technique to establish the most consistent activations among studies reporting brain responses subsequent to the application of noxious heat. A network of pain-related activity was replicated for stimuli to either upper limb that included two discernible regions of the mid-anterior cingulate cortex, bilateral thalami, insula, and opercula cortices, posterior parietal cortex, premotor cortex, supplementary motor area, and cerebellum. The findings of the meta-analysis resonate with other streams of information that continue to enhance our understanding of pain in the brain. The results also point toward new areas of research that may be fruitful for the exploration of central pain processing.

Afferent pain pathways: a neuroanatomical review

Painful experience is a complex entity made up of sensory, affective, motivational and cognitive dimensions. The neural mechanisms involved in pain perception acts in a serial and a parallel way, discriminating and locating the original stimulus and also integrating the affective feeling, involved in a special situation, with previous memories. This review examines the concepts of nociception, acute and chronic pain, and also describes the afferent pathways involved in reception, segmental processing and encephalic projection of pain stimulus. The interaction model of the cerebral cortex areas and their functional characteristics are also discussed.

Neural pathways between sacrocaudal afferents and lumbar pattern generators in neonatal rats

Projections of sacrocaudal afferents (SCA) onto lumbar pattern generators were studied in isolated spinal cords of neonatal rats. A locomotor-like pattern could be produced by SCA stimulation in the majority of the preparations. The SCA-induced lumbar rhythm was abolished after blocking synaptic transmission in the sacrococcygeal (SC) cord by bathing its segments in a low-calcium, high-magnesium artificial cerebrospinal fluid and restored when the synaptic block was alleviated by local application of calcium onto specific SC segments prior to SCA stimulation. Thus the SCA evoked lumbar rhythm involves synaptic activation of relay neurons in the SC cord. Functional activation of these relays depends on non-N-methyl-D-aspartate (NMDA) receptors because the lumbar rhythm was abolished when the non-NMDA receptor antagonist CNQX was added to the SC cord. By contrast, pharmacological block of the rhythmicity in the SC cord by specific antagonists of NMDA receptors and alpha1 and alpha2 adrenoceptors did not impair the SCA-induced lumbar rhythm. Midsagittal splitting experiments of parts of the SC and lumbar cord revealed that crossed and uncrossed ascending/propriospinal pathways are coactivated by SCA stimulation. We suggest that these pathways ascend onto the thoracolumbar cord through the lateral, ventrolateral, and ventral funiculi, because a complete block of the lumbar rhythm could only be obtained with a bilateral interruption of all of these funiculi. The relevance of our findings to the neural control of the rhythmogenic networks in the spinal cord is discussed.