Pain
-
Expectancies can shape pain and other experiences. Generally, experiences change in the direction of what is expected (ie, assimilation effects), as seen with placebo effects. However, in case of large expectation-experience discrepancies, experiences might change away from what is expected (ie, contrast effects). ⋯ In conclusion, even strong underpredictions of pain can reduce pain (ie, cause assimilation), although not significantly more than medium underpredictions. However, strong underpredictions can cause uncertainty and undermine trust. These findings suggest that healthcare providers may wish to be cautious with providing overly positive information about painful medical procedures.
-
Projection neurons in the spinal dorsal horn relay sensory information to higher brain centres. The activation of these populations is shaped by afferent input from the periphery, descending input from the brain, and input from local interneuron circuits. Much of our recent understanding of dorsal horn circuitry comes from studies in transgenic mice; however, information on projection neurons is still based largely on studies in monkey, cat, and rat. ⋯ These neurons exhibited higher action potential discharge frequencies and received weaker excitatory synaptic input than lamina I SPBNs, suggesting this deeper population produces different sensory codes destined for the PBN. Mouse SPBNs from both regions (laminae I and III-V) were often seen to give off local axon collaterals, and we provide neuroanatomical evidence they contribute to excitatory input to dorsal horn circuits. These data provide novel information to implicate excitatory input from parabrachial projection neuron in dorsal horn circuit activity during processing of nociceptive information, as well as defining deep dorsal horn projection neurons that provide an alternative route by which sensory information can reach the PBN.