To Acu or not to Puncture?

Even though acupuncture and its reputed role in Traditional Chinese Medicine appears as a true value in East & West, from heart’s “perspective” it feels really as a false value. Acupuncture behaves as a stressor. Its way of approaching the skin, and especially the sensitive mechanoreceptors, fits more in challenging the nociceptors (pain receptors), rather than any other kind of basic skin receptors, such as haptic-stretch-pressure & vibration. This kindling mechanism, this external source of algorithmical conglomerative stress onto the skin, and consequently to other biological systems of the organism which are connected/entangled with it from the embryological phase of the three germ layers, has inevitably a direct link with the autonomic nervous system; the hypothalamic-pituitary-adrenal (HPA) axis with cortisol production, and the sympathoadrenal medullary (SAM) axis which activate the sympathetic nervous system, which dedicates energy to more relevant bodily systems to acute adaptation to stress. The above-mentioned neurobiological mechanisms are the basic major systems that respond to stress, and by extension they can affect through it (stress caused by acupuncture) the immune system.

Ainsley Iggo. 2 August 1924—25 March 2012

Ainsley Iggo's research was focused on the functional properties of sensory receptors in the skin and viscera. He developed a new electrophysiological technique for recording the electrical activity of individual afferent fibres and was the first to record such activity from single unmyelinated afferents, the smallest diameter afferents in sensory nerves. His seminal work contributed to the discovery of nociceptors; the sensory receptors that respond to injury and are at the origin of pain sensation. He also recorded the functional activity of many types of sensory receptor in the skin, muscle and viscera and classified their responses according to their adequate stimuli. These findings gave support to the specificity theory of sensation, particularly of pain. He described the morphology of individually identified receptors, thus providing direct evidence for the long-held assumption that distinct morphological types of skin receptors mediate distinct sensations. Later in life he contributed to studies of sensory neurons in the spinal cord and of the sensory electro-receptors found in animals such as the echidna and the platypus. A native of New Zealand, he moved to the UK in 1950 and spent most of his professional life at the University of Edinburgh, where he created a highly productive research group at the Veterinary School.

Characterising the short-term habituation of event-related evoked potentials

Fast-rising sensory events evoke a series of functionally heterogeneous event-related potentials (ERPs). Stimulus repetition at 1 Hz is known to induce a strong habituation of the largest ERP responses, the vertex waves, which are elicited by stimuli regardless of their modality7, provided that they are salient and behaviourally-relevant. In contrast, the effect of stimulus repetition on the earlier sensor)7 components of ERl’s has been less explored, and the few existing results are inconsistent. To characterize how the different ERP waves habituate over time, we recorded the responses elicited by 60 identical somatosensory stimuli (activating either non-nociceptive A β or nociceptive A5 afferents), delivered at 1 Hz to healthy human participants. We show that the well-described spatiotemporal sequence of lateralised and vertex ERP components elicited by the first stimulus of the series is largely preserved in the smaller-amplitude, habituated response elicited by the last stimuli of the series. We also found that the earlier lateralised sensory waves habituate across the 60 trials following the same decay function of the vertex waves: this decay function is characterised by a large drop at the first stimulus repetition followed by smaller decreases at subsequent repetitions. Interestingly, the same decay functions described the habituation of ERPs elicited by repeated non-nociceptive and nociceptive stimuli. This study provides a neurophysiological characterization of the effect of prolonged and repeated stimulation on the main components of somatosensory ERPs. It also demonstrates that both lateralised waves and vertex waves are obligator}7 components of ERPs elicited by non-nociceptive and nociceptive stimuli.Significance statementOur results provide a functional characterization of the decay of the different ERP components when identical somatosensory (nociceptive and non-nociceptive) stimuli are repeated at 1Hz. East-rising stimuli elicit ERPs obligator)7 contributed by both early lateralised components and late vertex components, even when stimulus repetition minimizes stimulus relevance. This challenges the view that lateralised waves are not obligatorily elicited by nociceptive stimuli. Furthermore, the lateralised and vertex waves habituate to stimulus repetition following similar decay functions, which are unlikely explained in terms of fatigue or adaptation of skin receptors.

Cooling reduces the cutaneous afferent firing response to vibratory stimuli in glabrous skin of the human foot sole

Skin on the foot sole plays an important role in postural control. Cooling the skin of the foot is often used to induce anesthesia to determine the role of skin in motor and balance control. The effect of cooling on the four classes of mechanoreceptor in the skin is largely unknown, and thus the aim of the present study was to characterize the effects of cooling on individual skin receptors in the foot sole. Such insight will better isolate individual receptor contributions to balance control. Using microneurography, we recorded 39 single nerve afferents innervating mechanoreceptors in the skin of the foot sole in humans. Afferents were identified as fast-adapting (FA) or slowly adapting (SA) type I or II (FA I n = 16, FA II n = 7, SA I n = 6, SA II n = 11). Receptor response to vibration was compared before and after cooling of the receptive field (2–20 min). Overall, firing response was abolished in 30% of all receptors, and this was equally distributed across receptor type ( P = 0.69). Longer cooling times were more likely to reduce firing response below 50% of baseline; however, some afferent responses were abolished with shorter cooling times (2–5 min). Skin temperature was not a reliable indicator of the level of receptor activation and often became uncoupled from receptor response levels, suggesting caution in the use of this parameter as an indicator of anesthesia. When cooled, receptors preferentially coded lower frequencies in response to vibration. In response to a sustained indentation, SA receptors responded more like FA receptors, primarily coding “on-off” events.