Quantitative responses of spinothalamic lamina I neurones to graded mechanical stimulation in the cat

Nociceptive spinothalamic tract (STT) neurones in lamina I of the lumbosacral spinal cord of anaesthetized cats were characterized by recording their responses to graded mechanical stimulation with controlled forces of 10-120 g and probes of 5.0, 0.5 and 0.1 mm2 contact area. Neurones were identified by antidromic activation from the contralateral thalamus, and cells that responded to noxious stimulation were categorized as either nociceptive specific (NS, n = 20) or as polymodal nociceptive (HPC, responsive to heat, pinch and cold, n = 19) based on their responses to quantitative thermal stimuli. The mean responses of the 39 units increased linearly as stimulus intensity increased, and the population stimulus-response curves evoked by each of the three probes were all significantly different from each other. Thresholds were 45 g for the 5.0 mm2 probe, 30 g for the 0.5 mm2 probe and 20 g for the 0.1 mm2 probe. Further analysis showed that the NS neurones encoded both stimulus intensity and area (probe size) significantly better than HPC neurones in terms of their thresholds to individual probes, their peak discharge rates, their suprathreshold responsiveness and their ability to discriminate the three different probe sizes. These differences are consistent with the known differences between the mechanical encoding properties of A-fibre nociceptors, which provide the dominant inputs to NS neurones, and C-fibre nociceptors, which are the dominant inputs to HPC cells. Comparison of the stimulus-response curves of NS and HPC neurones indicated that the discharge of NS neurones better match the psychophysics of mechanical pain sensations in humans than the discharge of the HPC neurones do. Our findings support the view that NS neurones have a prominent role in mechanical pain and sharpness, and they corroborate the concept that the lamina I STT projection comprises several discrete channels that are integrated in the forebrain to generate qualitatively distinct sensations

Roles, caring and learning to teach science

Classroom narratives and stories are rich and powerful in offering deep insights into classrooms and the reality of teaching-a reality critically re-examined in this forum. Discussing Maria's narratives led to reflections about what it takes to support teachers to become agents of more equitable science practices. Factors such as time and identity-work are key dimensions of the authors' struggle, but they also address understanding students in profound ways. The ways in which contradictions at different levels in the educational system can become sources of growth, reflection and action are discussed; yet no simple answers follow. Teaching and becoming a teacher are best understood as life-long processes of reflection and action and as political acts that entail challenging many boundaries. They also involve putting oneself into vulnerable roles and positions. This dialogue opens up many questions about how we can collaborate, guide and support both novices and experienced professionals in education as researchers, science staff developers, and teacher educators. It seeks to support the on-going quest to make science education authentic and equitable