Attentional modulation of somatosensory processing during the anticipation of movements accompanying pain : an event-related potential study

Attending to pain-relevant information is crucial to protect us from physical harm. Behavioral studies have already suggested that during anticipation of pain somatosensory input at the body location under threat is prioritized. However, research using daily life cues for pain, especially movements, is lacking. Furthermore, to our knowledge, no studies have investigated cortical processing associated with somatosensory processing during threatened movements. The current study aims to investigate whether movements accompanying pain automatically steer attention toward somatosensory input at the threatened location, affecting somatosensory evoked potentials (SEPs). Healthy volunteers were cued to perform movements with the left or the right hand, and one of these movements could be accompanied by pain on the moving hand. During movement anticipation, a task-irrelevant tactile stimulus was presented to the threatened or pain-free hand to evoke SEPs. During anticipation of movements accompanying pain, the N120 component was increased for tactile stimuli at the threatened relative to the hand without pain. Moreover, the P200 SEP was enhanced during anticipation of movements accompanying pain relative to movements without pain, irrespective of which hand was stimulated. These findings show that the anticipation of pain-accompanying movements may affect the processing of somatosensory input, and that this is likely to be driven by attentional processes. PERSPECTIVE: This study shows that the anticipation of pain-related movements automatically biases attention toward stimuli at a pain-related location, measured according to SEPs. The present study provides important new insights in the interplay between pain and attention, and its consequences at the cortical level

Hypervigilance for bodily sensations in the back during a movement task in people with chronic and recurrent low back pain

Objectives: The current study assessed the role of hypervigilance for bodily sensations in the back in long-term low back pain problems. Methods: People with chronic low back pain, recurrent low back pain, and no low back pain were compared on the extent to which they attended to somatosensory stimuli on the back during a movement task. To measure hypervigilance, somatosensory event-related potentials (SEPs) to task-irrelevant tactile stimuli on the back were measured when preparing movements in either a threatening or a neutral condition, indicated by a cue signaling possible pain on the back during movement or not. Results: Results showed stronger attending to stimuli on the back in the threat condition than in the neutral condition, as reflected by increased amplitude of the N96 SEP. However, this effect did not differ between groups. Similarly, for all 3 groups the amplitude of the P172 was larger for the threatening condition, suggesting a more general state of arousal resulting in increased somatosensory responsiveness. No significant associations were found between somatosensory attending to the back and theorized antecedents such as pain catastrophizing, pain-related fear, and pain vigilance. Discussion: The current study confirmed that individuals preparing a movement attended more toward somatosensory stimuli at the lower back when anticipating back pain during the movement, as measured by the N96 SEP. However, no differences were found between participants with chronic low back pain or recurrent low back pain, or the pain-free controls

Somatosensory attentional modulations during pain-related movement execution

Pain serves to protect against bodily threat, and therefore initiates protective responses such as attending toward threat-relevant information. Since pain is often exacerbated by executing movements, these motor actions may serve as cues for pain. Up to date, however, pain-related attention during movement remains largely unexplored. While it has been shown that the preparation of a pain-related movement leads to enhanced processing of somatosensory information, it is unclear how the actual execution of a movement interacts with somatosensory attention. In the current study, we examined whether somatosensory processing is enhanced at a moving body part when the movement is expected to be associated with pain. Participants were asked to execute hand movements which were occasionally followed by a pain stimulus. To measure somatosensory attention, a task-irrelevant, innocuous tactile probe was presented on either hand to evoke a somatosensory evoked potential (SEP). The results showed an elevation of the N120 SEP at the hand performing a potentially painful movement, indicating heightened attention toward tactile information at the threatened moving hand compared to the non-threatened hand. Additionally, the P200 SEP also showed enlarged responses when performing a pain-related movement compared to a no-pain-related movement. These results show that not only the anticipation, but also the execution of pain-related movements, may modulate the processing of somatosensory input, driven by attentional processes

Somatosensory attending to the lower back is associated with response speed of movements signaling back pain

The present study investigated if preparing a movement that is expected to evoke pain results in hesitation to initiate the movement (i.e., avoidance) and, especially, if the allocation of attention to the threatened body part mediates such effect. To this end, healthy volunteers (N = 33) performed a postural perturbation task recruiting lower back muscles. In 'threat trials', the movement was sometimes followed by an experimental pain stimulus on the back, whereas in 'no-threat trials', a non-painful control stimulus was applied. Electroencephalography (EEG) was used to assess attending to the lower back. Specifically, somatosensory evoked potentials (SEPs) to task-irrelevant tactile stimuli administered to the lower back were recorded during movement preparation. Reaction times (RTs) were recorded to assess movement initiation. The results revealed faster responses and enhanced somatosensory attending to the lower back on threat trials than on no-threat trials. Importantly, the amplitude of the N95 SEP component predicted RTs and was found to partially mediate the effect of pain anticipation on movement initiation. These findings suggest that somatosensory attending might be a potential mechanism by which pain anticipation can modulate motor execution

Representing multiple observed actions in the motor system

There is now converging evidence that others’ actions are represented in the motor system. However, social cognition requires us to represent not only the actions but also the interactions of others. To do so, it is imperative that the motor system can represent multiple observed actions. The current fMRI study investigated whether this is possible by measuring brain activity from 29 participants while they observed 2 right hands performing sign language gestures. Three key results were obtained. First, brain activity in the premotor and parietal motor cortex was stronger when 2 hands performed 2 different gestures than when 1 hand performed a single gesture. Second, both individual observed gestures could be decoded from brain activity in the same 2 regions. Third, observing 2 different gestures compared with 2 identical gestures activated brain areas related to motor conflict, and this activity was correlated with parietal motor activity. Together, these results show that the motor system is able to represent multiple observed actions, and as such reveal a potential mechanism by which third-party social encounters could be processed in the brain

Mild temperature hydrothermal oxidation of anaerobic fermentation filtrate for carbon and nitrogen recovery in a regenerative life support system

Hydrothermal oxidation of fermentation filtrate was conducted in a tubular reactor to recover carbon (as CO2) and nitrogen (as NH4+ or NO3-) at mild temperature destined for use in a regenerative life support system. Temperature, residence time (tR), and the oxidizer equivalence ratio (OER) were the experimental variables in the oxidation tests. The highest carbon recovery achieved was 68.2%, with 80.1% of the total nitrogen being retained in the form of NH4+ or NO3- at 380 ℃, tR = 48 s and OER = 4.0. The effect of temperature, residence time and OER on carbon and nitrogen distribution were discussed. Moreover, a first-order reaction rate was applied by means of regression analysis to estimate the carbon conversion rates. Prolonging the residence time at 380 ℃ with OER = 3.0 is proposed to be a promising modification to increase both carbon and nitrogen recovery from the filtrate