Pain-related evoked potentials are modulated across the cardiac cycle

Evidence suggests that the arterial baroreceptors modulate pain. To examine whether cortical processing of nociception is modulated by natural variations in arterial baroreceptor stimulation during the cardiac cycle, peak-to-peak amplitudes of the N2–P2 pain-related potential and pain ratings were recorded in response to noxious laser stimulation at different times during the cardiac cycle in 10 healthy males. Significant variations in the N2–P2 amplitudes occurred across the cardiac cycle, with smaller amplitudes midcycle, indicating that cortical processing of nociception was attenuated during systole compared to diastole. Pain ratings did not vary across the cardiac cycle. These data support the hypothesis that arterial baroreceptors modulate the processing of nociception during each cardiac cycle

The effect of a paced auditory serial addition test (PASAT) intervention on the profile of volatile organic compounds in human breath: a pilot study

This study sought to identify if detectable changes in human breath profiles may be observed following a psychological intervention designed to induce stress, a paced auditory serial addition test (PASAT). Breath samples were collected from 22 participants (10 male and 12 female) following a double cross-over randomized design with two experimental interventions. One intervention required participants to listen to classical music chosen to be neutral. The other intervention required participants to undertake a PASAT that induced cardiovascular responses consistent with acute stress. Both interventions also involved two sequences of cognitive function tests. Blood-pressure and heart-rate were recorded throughout each intervention and distal breath samples were collected onto Tenax® TA/Carbograph 1 thermal desorption tubes, using an adaptive breath sampler. Samples were collected before and after the PASAT. Breath samples were analysed by thermal desorption gas chromatography-mass spectrometry. Data registration using retention indexing and peak deconvolution followed by partial least-squares discriminant analysis identified six stress sensitive compounds. A principal components analysis model based on these components generated a model that predicted post-PASAT versus post-neutral intervention samples with a sensitivity of 83.3% and a selectivity of 91.6% for females, compared to 100% sensitivity and 90% selectivity for males. Of the six compounds indole, 2-hydroxy-1-phenylethanone, benzaldehyde, and 2-ethylhexan-1-ol were identified on the basis of mass spectral, retention indexing and confirmation against pure standards. 2-methylpentadecane was tentatively identified from mass spectral and retention indexing, whilst one component has yet to be assigned, although the mass spectrum is indicative of a terpene. Indole and 2-methylpentadecane concentrations increased in response to the PASAT intervention, while the other compounds reduced in their abundance in human breath, possibly as a result of ventilation effects

Sensory detection thresholds are modulated across the cardiac cycle: evidence that cutaneous sensibility is greatest for systolic stimulation

The visceral afferent feedback hypothesis proposes that sensorimotor function is impaired by cortical inhibition associated with increased baroreceptor activation. This study is the first to examine the effects of naturally occurring variations in baroreceptor activity across the cardiac cycle on cutaneous sensory detection thresholds. In each trial, an electrocutaneous stimulus was delivered to the index finger at one of three intervals (0, 300, 600 ms) after the R-wave of the electrocardiogram. Separate interleaving up-down staircases were used to determine the 50% detection threshold for each R-wave to stimulation interval. Cutaneous sensory detection thresholds were lower for stimuli presented at R+300 ms than R+0 ms or R+600 ms. The finding that cutaneous sensibility was greater when stimulated during systole than diastole may be accounted for by a modified afferent feedback hypothesis. Copyright © 2009 Society for Psychophysiological Research

Effects of essential hypertension on short latency human somatosensory-evoked potentials

Reduced perception of somatosensory stimulation in patients with essential hypertension may be due to deficits in the ascending somatosensory pathway. Function in the ascending somatosensory pathway was assessed bymeasuring N9, N13, and N20 somatosensory-evoked potentials in 14 unmedicated essential hypertensives and 22 normotensives. N9 amplitudes were smaller and N13 amplitudes marginally smaller in hypertensives than normotensives. N9 amplitudes were inversely associated with blood pressure. N20 amplitudes and N9, N13, and N20 latencies did not differ between groups. In addition, plexus-to-cord, cord-to-cortex, and plexus-to-cortex conduction times were not different between groups. These data suggest that hypertension affects the peripheral nervous system by reducing the number of active sensory nerve fibers without affecting myelination. However, hypertension does not seem to affect the afferent somatosensory pathway within the brain