Independent causal contributions of alpha- and beta-band oscillations during movement selection

To select a movement, specific neuronal populations controlling particular features of that movement need to be activated, whereas other populations are downregulated. The selective (dis)inhibition of cortical sensorimotor populations is governed by rhythmic neural activity in the alpha (8–12 Hz) and beta (15–25 Hz) frequency range. However, it is unclear whether and how these rhythms contribute independently to motor behavior. Building on a recent dissociation of the sensorimotor alpha- and beta-band rhythms, we test the hypothesis that the beta-band rhythm governs the disinhibition of task-relevant neuronal populations, whereas the alpha-band rhythm suppresses neurons that may interfere with task performance. Cortical alpha- and beta-band rhythms were manipulated with transcranial alternating current stimulation (tACS) while human participants selected how to grasp an object. Stimulation was applied at either 10 or 20 Hz and was imposed on the sensorimotor cortex contralaterally or ipsilaterally to the grasping hand. In line with task-induced changes in endogenous spectral power, the effect of the tACS intervention depended on the frequency and site of stimulation. Whereas tACS stimulation generally increased movement selection times, 10 Hz stimulation led to relatively faster selection times when applied to the hemisphere ipsilateral to the grasping hand, compared with other stimulation conditions. These effects occurred selectively when multiple movements were considered. These observations functionally differentiate the causal contribution of alpha- and beta-band oscillations to movement selection. The findings suggest that sensorimotor beta-band rhythms disinhibit task-relevant populations, whereas alpha-band rhythms inhibit neuronal populations that could interfere with movement selection

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Selective attention modulates temporal processing

A near continuous stream of information reaches our eyes and the task of the visual system is to make sense of it. Visual stimuli arrive in quick succession: sometimes it is necessary to integrate stimuli over time, but other times it is necessary to segregate them. These opposing processes of integration and segregation are two forms of temporal processing, a topic which is underrepresented in the literature as compared to spatial processing. In particular, there is limited understanding about how temporal processing is influenced by selective attention. Selective attention refers to a family of mechanisms by which the limited resources of our mental architecture are diverted to preferentially process stimuli more likely to be relevant. Here, a number of empirical investigations into the effect of endogenous, covert spatial attention on temporal processing are presented. This includes use of a task in which visual stimulation is held constant and only the temporal processing goal (integration versus segregation) and the spatial location of attention are manipulated. There were strong spatial cueing effects: a benefit to performance when validly cued and a cost when invalidly cued. These attentional effects are reliable for both opposing processes of temporal integration and segregation. Furthermore, these spatial cueing effects are robust even when the cues provide no implicit temporal expectations. We used magnetoencephalography and the same task to measure changes in the brain signal associated with these effects, namely shifts in peak alpha frequency for integration as compared to segregation, as well as spatially specific modulations in this metric relative to the locus of attention. These findings of robust spatial cueing effects on temporal processing and of strategic shifts in oscillatory frequency associated with temporal processing goals and allocation of attention are discussed within a temporal windows framework and in the context of other candidate mechanisms. The empirical evidence reported here can be accounted for by the idea of a flexible adaptation of the size of temporal windows, essentially changing the sampling rate of perception in line with task demands