Fluctuations of sensorimotor processing in migraine: A controlled longitudinal study of beta event related desynchronization

Background: The migraine brain seems to undergo cyclic fluctuations of sensory processing. For instance, during the preictal phase, migraineurs experience symptoms and signs of altered pain perception as well as other well-known premonitory CNS-symptoms. In the present study we measured EEG-activation to non-painful motor and sensorimotor tasks in the different phases of the migraine cycle by longitudinal measurements of beta event related desynchronization (beta-ERD). Methods: We recorded electroencephalography (EEG) of 41 migraine patients and 31 healthy controls. Each subject underwent three EEG recordings on three different days with classification of each EEG recording according to the actual migraine phase. During each recording, subjects performed one motor and one sensorimotor task with the flexion-extension movement of the right wrist. Results: Migraine patients had significantly increased beta-ERD and higher baseline beta power at the contralateral C3 electrode overlying the primary sensorimotor cortex in the preictal phase compared to the interictal phase. We found no significant differences in beta-ERD or baseline beta power between interictal migraineurs and controls. Conclusion: Increased preictal baseline beta activity may reflect a decrease in pre-activation in the sensorimotor cortex. Altered pre-activation may lead to changes in thresholds for inhibitory responses and increased beta-ERD response, possibly reflecting a generally increased preictal cortical responsivity in migraine. Cyclic fluctuations in the activity of second- and third-order afferent somatosensory neurons, and their associated cortical and/or thalamic interneurons, may accordingly also be a central part of the migraine pathophysiology.publishedVersio

Effects of insufficient sleep on sensorimotor processing in migraine. A randomised, blinded crossover study of event related beta oscillations

Background Migraine has a largely unexplained connection with sleep and is possibly related to a dysfunction of thalamocortical systems and cortical inhibition. In this study we investigate the effect of insufficient sleep on cortical sensorimotor processing in migraine. Methods We recorded electroencephalography during a sensorimotor task from 46 interictal migraineurs and 28 controls after two nights of eight-hour habitual sleep and after two nights of four-hour restricted sleep. We compared changes in beta oscillations of the sensorimotor cortex after the two sleep conditions between migraineurs, controls and subgroups differentiating migraine subjects usually having attacks starting during sleep and not during sleep. We included preictal and postictal recordings in a secondary analysis of temporal changes in relation to attacks. Results Interictally, we discovered lower beta synchronisation after sleep restriction in sleep related migraine compared to non-sleep related migraine (p=0.006) and controls (p=0.01). No differences were seen between controls and the total migraine group in the interictal phase. After migraine attacks, we observed lower beta synchronisation (p<0.001) and higher beta desynchronisation (p=0.002) after sleep restriction closer to the end of the attack compared to later after the attack. Conclusion The subgroup with sleep related migraine had lower sensorimotor beta synchronisation after sleep restriction, possibly related to dysfunctional GABAergic inhibitory systems. Sufficient sleep during or immediately after migraine attacks may be of importance for maintaining normal cortical excitability.publishedVersio

Effects of recreational angling and air exposure on the physiological status and reflex impairment of European grayling (Thymallus thymallus)

European grayling (Thymallus thymallus) is a popular recreational fish that may be lifted out of the water to facilitate hook removal or for admiration. To evaluate the effects of air exposure and angling-induced exhaustive exercise on released grayling condition, we assessed blood physiology and reflexes of grayling after angling and air exposure in the subarctic River Lakselva (Norway) at midsummer temperatures (i.e., 17–18 °C). Blood samples were drawn 30 min after angling and analyzed for lactate anions, glucose, sodium ions, and pH. Reflex impairment was determined with orientation and tail grab reflex action assessments immediately after landing, after air exposure, and after 30 min holding. Blood physiology did not indicate an exacerbating effect of air exposure relative to just angling-induced exercise, but significant and prolonged reflex impairment was associated with the 120 s air exposure interval. Anglers must take care to minimize air exposure to adhere to best handling practices.publishedVersio

Accuracy of neuropathic pain measurements in patients with symptoms of polyneuropathy: validation of painDETECT, Self-Completed Leeds Assessment of Neuropathic Symptoms and Signs, and Douleur Neuropathique 4

Pain is a common symptom in patients referred to polyneuropathy assessment. Diagnostic evaluation and choice of treatment may depend on whether the pain is likely to be neuropathic or not. This study aimed to investigate the diagnostic accuracy of 3 tools commonly used to differentiate between neuropathic and nonneuropathic pain. To accomplish this, we included patients with bilateral distal lower extremity pain, referred to neurological outpatient clinics at 5 Norwegian University hospitals for polyneuropathy assessment. The patients filled in Norwegian versions of painDETECT, the Self-Completed Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS), and the clinician-rated Douleur Neuropathique 4 (DN4). All patients underwent a clinical examination and nerve conduction measurements and were classified according to the NeuPSIG neuropathic pain criteria (reference standard). In total, 729 patients were included, of which 63% had neuropathic pain by the reference standard. Only DN4 demonstrated high sensitivity (0.87), whereas all 3 tools had low specificity (≤0.65). Importantly, the tools' predictive ability was unsatisfactory; The probability of getting a correct test result was 3 quarters at best, and at worst, no better than two fifths. Consequently, we show that neither DN4, painDETECT, nor S-LANSS can be confidently used to assess neuropathic pain in a neurological outpatient population with symptoms of polyneuropathy

Experimental pain and migraine: Investigating the effect of non-invasive cortical modulation of pain, and phasic alterations of pain in migraineurs

Background: Both clinical symptoms, imaging findings, and neurophysiological measures suggest varying cyclic alterations in CNS-function between, before, during and after the migraine headache. Altered pain perception (preictal and ictal allodynia) seems to be a common non-obligatory clinical symptom in migraine. However, the pathophysiological mechanisms controlling this periodicity are still mostly unknown. Quantitative sensory testing (QST), including pain thresholds and pain scores during tonic stimulation, and laser-evoked potentials (LEP) are useful measures of pain perception and processing. We explored how these measures change before, during and after migraine headache in a blinded longitudinal study. Repetitive transcranial magnetic stimulation (rTMS) may alter the activity in stimulated and connected cortical areas. This method can help us understand the contribution of the stimulated cortical regions in migraine pathophysiology. We measured the effect of rTMS to the secondary somatosensory cortex (S2), a cortical area important for pain processing. The main aim of the studies was to investigate changes in experimental pain measures in migraineurs, both between homeostatic states, here defined by migraine phase, and by external modulation of cortical excitability with rTMS. Methods: In the first study, we explored the effect of high-frequency navigated rTMS and sham stimulation to S2 on thermal detection and pain thresholds, and pain scores; comparing 26 migraineurs in the interictal phase with 31 controls. In the second study, we measured both QST-measures and LEP four times in 49 migraineurs. The four sessions were categorized by migraine diaries and measures obtained between attacks were compared with recordings from the periods before, during and after an attack. Also, we compared interictal recordings with 30 controls. In both studies, the investigators were blinded during recording and analysis of the data. Main results: - RTMS to S2 increased cold and heat pain thresholds in controls compared to migraineurs in the interictal phase. - Pain scores by prolonged heat stimulation of both forehead and hand decreased in the preictal phase. - Trigeminal pain scores increased, and cold pain thresholds decreased (higher absolute temperature), during headache. - There was a subtle lack of habituation of the N1 LEP-amplitude in the ictal phase. Conclusions: We found slightly altered central processing of pain in migraineurs. Effects were observed both as altered pain-modulation after cortical stimulation and by changes through the cyclic migraine-phase process. Interictal slight hyperalgesia, followed by short-lasting preictal hypoalgesia and ictal (and partly postictal) hyperalgesia was generally observed. The increased trigeminal pain sensitivity during headache complies with clinical symptoms and previous neurophysiological findings. However, since interictal and preictal alterations were observed for pain elicited from both hand and face, a general alteration in pain processing like central sensitization (as opposed to a regional trigeminal affection), is supported. The lack of an analgesic effect by navigated rTMS may reflect non-optimal target, increased thalamocortical activation or decreased intracortical inhibition, and/or reduced activity of the descending pain modulation system in migraineurs. The preictal hypoalgesia may be caused by transient thalamocortical hypoactivity, cortical hypoexcitability or excessive intracortical inhibition, or by increased endogenous analgesia. The wellknown autonomic symptoms before and during migraine, combined with the presently observed hypoalgesia, suggest a possible increase in hypothalamic cyclic modulation of both autonomic control and pain processing. Although there were few significant results, with moderate effect sizes, our findings highlight the preictal phase as a promising focus in further studies

Using acoustic telemetry to monitor the effects of crowding and delousing procedures on farmed Atlantic salmon (Salmo salar)

The aim of this study was to demonstrate the feasibility of acoustic telemetry for monitoring fish during farm operations and gather knowledge about Atlantic salmon responses during crowding and delousing events in a commercial sea-cage. 21 fish were equipped with a novel transmitter tag type using data from pressure sensors and accelerometers to compute swimming depth and swimming activity of individual fish. The fish were monitored over four months, during which they were subjected to three thermal delousing events. In the periods before and after delousing, the fish generally exhibited a circadian rhythm in both swimming activity and depth, with high activity and deep swimming during daytime and low activity and shallow swimming during night. Swimming activity recorded during crowding and delousing events was significantly higher than background swimming activity levels registered a day before and after delousing. Although activity levels differed significantly between the three events and between the different stages within each event, the highest activity levels were consistently measured during thermal treatment. Swimming depth differed significantly between delousing events and was strongly influenced by daylight. In summary, crowding and delousing induced increased movement in the fish, while swimming depth appeared to be less sensitive to these operations. The conclusion of the study is that acoustic telemetry is a suitable tool for monitoring fish during challenging operations such as crowding and delousing, as well as during normal cage management. Moreover, this study provides new knowledge on how the behaviour of Atlantic salmon may be affected by delousing.publishedVersio

Habituation of laser-evoked potentials by migraine phase: a blinded longitudinal study

Abstract Background Migraineurs seem to have cyclic variations in cortical excitability in several neurophysiological modalities. Laser-evoked potentials (LEP) are of particular interest in migraine because LEP specifically targets pain pathways, and studies have reported different LEP-changes both between and during headaches. Our primary aim was to explore potential cyclic variations in LEP amplitude and habituation in more detail with a blinded longitudinal study design. Methods We compared N1 and N2P2 amplitudes and habituation between two blocks of laser stimulations to the dorsal hand, obtained from 49 migraineurs with four sessions each. We used migraine diaries to categorize sessions as interictal (> one day from previous and to next attack), preictal (< one day before the attack), ictal or postictal (< one day after the attack). Also, we compared 29 interictal recordings from the first session to 30 controls. Results N1 and N2P2 amplitudes and habituation did not differ between preictal, interictal and postictal phase sessions, except for a post hoc contrast that showed deficient ictal habituation of N1. Habituation is present and similar in migraineurs in the interictal phase and controls. Conclusions Hand-evoked LEP amplitudes and habituation were mainly invariable between migraine phases, but this matter needs further study. Because hand-evoked LEP-habituation was similar in migraineurs and controls, the present findings contradict several previous LEP studies. Pain-evoked cerebral responses are normal and show normal habituation in migraine

Effects of recreational angling and air exposure on the physiological status and reflex impairment of European grayling (Thymallus thymallus)

European grayling (Thymallus thymallus) is a popular recreational fish that may be lifted out of the water to facilitate hook removal or for admiration. To evaluate the effects of air exposure and angling-induced exhaustive exercise on released grayling condition, we assessed blood physiology and reflexes of grayling after angling and air exposure in the subarctic River Lakselva (Norway) at midsummer temperatures (i.e., 17–18 °C). Blood samples were drawn 30 min after angling and analyzed for lactate anions, glucose, sodium ions, and pH. Reflex impairment was determined with orientation and tail grab reflex action assessments immediately after landing, after air exposure, and after 30 min holding. Blood physiology did not indicate an exacerbating effect of air exposure relative to just angling-induced exercise, but significant and prolonged reflex impairment was associated with the 120 s air exposure interval. Anglers must take care to minimize air exposure to adhere to best handling practices.publishedVersio

Fluctuations of sensorimotor processing in migraine: A controlled longitudinal study of beta event related desynchronization

Background: The migraine brain seems to undergo cyclic fluctuations of sensory processing. For instance, during the preictal phase, migraineurs experience symptoms and signs of altered pain perception as well as other well-known premonitory CNS-symptoms. In the present study we measured EEG-activation to non-painful motor and sensorimotor tasks in the different phases of the migraine cycle by longitudinal measurements of beta event related desynchronization (beta-ERD). Methods: We recorded electroencephalography (EEG) of 41 migraine patients and 31 healthy controls. Each subject underwent three EEG recordings on three different days with classification of each EEG recording according to the actual migraine phase. During each recording, subjects performed one motor and one sensorimotor task with the flexion-extension movement of the right wrist. Results: Migraine patients had significantly increased beta-ERD and higher baseline beta power at the contralateral C3 electrode overlying the primary sensorimotor cortex in the preictal phase compared to the interictal phase. We found no significant differences in beta-ERD or baseline beta power between interictal migraineurs and controls. Conclusion: Increased preictal baseline beta activity may reflect a decrease in pre-activation in the sensorimotor cortex. Altered pre-activation may lead to changes in thresholds for inhibitory responses and increased beta-ERD response, possibly reflecting a generally increased preictal cortical responsivity in migraine. Cyclic fluctuations in the activity of second- and third-order afferent somatosensory neurons, and their associated cortical and/or thalamic interneurons, may accordingly also be a central part of the migraine pathophysiology

Fluctuations of sensorimotor processing in migraine: A controlled longitudinal study of beta event related desynchronization

Background The migraine brain seems to undergo cyclic fluctuations of sensory processing. For instance, during the preictal phase, migraineurs experience symptoms and signs of altered pain perception as well as other well-known premonitory CNS-symptoms. In the present study we measured EEG-activation to non-painful motor and sensorimotor tasks in the different phases of the migraine cycle by longitudinal measurements of beta event related desynchronization (beta-ERD). Methods We recorded electroencephalography (EEG) of 41 migraine patients and 31 healthy controls. Each subject underwent three EEG recordings on three different days with classification of each EEG recording according to the actual migraine phase. During each recording, subjects performed one motor and one sensorimotor task with the flexion-extension movement of the right wrist. Results Migraine patients had significantly increased beta-ERD and higher baseline beta power at the contralateral C3 electrode overlying the primary sensorimotor cortex in the preictal phase compared to the interictal phase. We found no significant differences in beta-ERD or baseline beta power between interictal migraineurs and controls. Conclusion Increased preictal baseline beta activity may reflect a decrease in pre-activation in the sensorimotor cortex. Altered pre-activation may lead to changes in thresholds for inhibitory responses and increased beta-ERD response, possibly reflecting a generally increased preictal cortical responsivity in migraine. Cyclic fluctuations in the activity of second- and third-order afferent somatosensory neurons, and their associated cortical and/or thalamic interneurons, may accordingly also be a central part of the migraine pathophysiology