Hans Strenge

Polysomnographic findings in nights preceding a migraine attack

Sleep recordings were performed in eight patients to analyse sleep alterations preceding migraine attacks. Polysomnographic recordings from nights before an attack were compared with nights without following migraine. We analysed standard sleep parameters and electroencephalogram (EEG) power spectra. The main findings preceding migraine attacks were a significant decrease in the number of arousals, a decrease in rapid eye movement (REM) density, a significant decrease of beta power in the slow wave sleep, and a decrease of alpha power during the first REM period. The results suggest a decrease in cortical activation during sleep preceding migraine attacks. According to the models of sleep regulation, alterations in the function of aminergic or cholinergic brainstem nuclei have to be discussed.

Morning headaches in patients with sleep disorders: a systematic polysomnographic study

OBJECTIVES Patients with sleep disorders suffer more often from headache after awakening than healthy subjects. However, it still is a matter of controversy whether this applies only to patients with sleep apnea syndrome (SAS) or also to patients with other diagnoses of sleep disorders. METHODS We asked all patients in our sleep laboratory about the frequency of past headaches and also ascertained the occurrence of morning headaches after awakening in the sleep laboratory. Polysomnographic recordings from nights before morning headache were compared with nights without following headache. Four hundred and thirty-two patients with sleep disorders (age range 18-86 years, 37% women) and 30 healthy subjects (age range 24-55 years, 27% women) participated in this prospective study. RESULTS The reported frequency of past headaches and the frequency of morning headache in the sleep laboratory were significantly increased in patients with SAS and other sleep disorders compared with healthy subjects. The occurrence of morning headache in the sleep laboratory was associated polysomnographically with a decrease in total sleep time, sleep efficiency and amount of rapid eye movement sleep and with an increase in the wake-time during the preceding night. CONCLUSIONS We conclude that morning headaches in patients with sleep disorders might be associated with particular disturbances of the preceding nights sleep. We speculate that dysregulation in anatomically identical central regions modulating sleep and nociception might be relevant to morning headache, rather than one particular sleep disorder such as SAS.

Are Numbers Special? Comparing the Generation of Verbal Materials From Ordered Categories (Months) to Numbers and Other Categories (Animals) in an fMRI Study

Months, days of the week, and numbers differ from other verbal concepts because they are ordered in a sequence, whereas no order is imposed on members of other categories, such as animals or tools. Recent studies suggest that numbers activate a representation of their quantity within the intraparietal sulcus (IPS) automatically, that is, in tasks that do not require the processing of quantity. It is unclear, however, whether ordered verbal materials in general and not only numbers activate the IPS in such tasks. In the present functional magnetic resonance imaging study word generation of months, numbers, and animals were compared. Word generation of numbers and nonnumerical materials from an ordered category (months) activated the IPS more strongly than generating items from a not‐ordered category such as animals or the verbal control conditions. An ROI analysis of three subregions within the anterior IPS revealed that the most anterior and lateral of these regions, human intraparietal area hIP2, shows a greater sensitivity to ordered materials than the other two areas, hIP1 and hIP3. Interestingly, no difference in activation was observed within the IPS between numbers and months suggesting that the activation of the IPS might not be modulated by the additional quantity information carried by numbers. Hum Brain Mapp, 2008.

Correlation between tests of attention and performance on grooved and Purdue pegboards in normal subjects

This study investigated the relation between tests of manual dexterity and attentional functions with 49 normal, right-handed medical students (26 women, 23 men, ages 19–30 years) who were assessed with a Purdue Pegboard Test, Grooved Pegboard Test, and a Test for Attentional Performance, comprising measures of tonic and phasic alertness and divided attention. Weak to moderately high partial correlations controlling for finger size were obtained between pegboard test performance of the left hand and phasic alertness (r = .31–.5O). Purdue Pegboard Assembly subtest scores were weakly correlated with divided attention (r = −.39). These findings suggest that attention is an important determinant of performance for manual dexterity tests of the nondominant hand.

Non-linear electroencephalogram dynamics in patients with spontaneous nocturnal migraine attacks

The present study was conducted to examine non-linear electroencephalogram (EEG) measures during the development of a spontaneous migraine attack. We investigated the sleep EEG of five patients with migraine without aura in the pain-free interval and at the onset of a nocturnal attack. Sleep EEG recordings were analysed using the method of global dimensional complexity compared to conventional sleep scoring techniques. We found no divergence between classical sleep architecture and the estimated dimensional course nor any relevant short-term changes related to the onset of headache. There was, however, a loss of dimensional complexity in the first two non-rapid eye movement sleep states in the migraine night, with statistical significance during the second sleep cycle. For the first time, these results provide evidence of a global dimension decrease that is related to cortical network changes during a migraine attack.

Changes in cortical dynamics in the preictal stage of a migraine attack.

Neurophysiologic studies suggest that migraineurs without aura have a dysfunction of cortical information processing in the pain-free interval. In this study, the advanced method of nonlinear multielectrode sleep-EEG analysis is used to investigate changes of cortical activity in the preictal time span. Five patients (four women, one man; age range, 29 to 58 years) experiencing migraine without aura participated in the study. The patients spent two blocks in the sleep laboratory. The first block was taken in a headache-free interictal time interval, and the second block when the onset of a migraine attack was most likely. After a nocturnal migraine attack, the patient was asked to mark the maximum of migraine pain in a surface-head scheme. The comparison of preictal and interictal EEGs enabled the authors to obtain a topographical view of changes in cortical dynamics. In each patient map, an area was found that displayed a pronounced focus indicating the region of maximum change in dimensional complexity. It shows a clearly recognizable correspondence with the scalp topography of the later pain perception. These findings indicate an association between cortical status and pain lateralization in the preictal time span.

Unidirectional interference in use of nondominant hand during concurrent Grooved Pegboard and random number generation tasks.

The interference effect between Grooved Pegboard task with either hand and the executive task of cued verbal random number generation was investigated, 24 normal right-handed subjects performed each task under separate (single-task) and concurrent (dual-task) conditions. Articulatory suppression was required as an additional secondary task during pegboard performance. Analysis indicated an unambiguous distinction between the two hands. Comparisons of single-task and dual-task conditions showed an asymmetrical pattern of unidirectional interference with no practice effects during pegboard performance. Concurrent performance with nondominant hand but not the dominant hand of random number generation performance became continuously slower. There was no effect of divided attention on pegboard performance. Findings support the idea that the nondominant hand on the pegboard and random number tasks draw from the same processing resources but that for the executive aspect random number generation is more sensitive to changes in allocation of attentional resources.

Random number generation in native and foreign languages

The effects of different levels of language proficiency on random number generation were examined in this study. 16 healthy right-handed students (7 women, 9 men; aged 22 to 25 years, M = 23.8, SD = .83) attempted to generate a random sequence of the digits 1 to 9 at pacing frequencies of 1, 1.5, and 2 Hz. Randomization was done in German (native language L1), English (first foreign language L2), and French (second foreign language L3). There was a pattern of redundancy and seriation tendencies, increasing with speed of generation for all languages (L1–L3). While using L2 and L3, responses slowed and the number of errors committed increased. Further, there was a peculiar pattern of dissociation in nonrandom performance with an increase of habitual counting in ones and a strong reduction of counting in twos. All effects were most pronounced when subjects used L3 and 2-Hz pacing rates. Slowing and nonrandomness was not correlated with self-assessment parameters regarding language proficiency. We suggest that in a task involving number activation in a nonnative language, lack of proficiency will interfere with random number generation, leading to interruptions and rule breaking, at least when reaching the limits of attentional capacity at higher pacing rates.

Effects of Pregnancy on Slow Cortical Potentials in Migraine Patients and Healthy Controls

Increased negative amplitudes and lack of habituation of contingent negative variation (CNV) in migraine are well established and are supposed to reflect an altered cortical excitability level. Migraine attacks occur less during pregnancy but often relapse after delivery. We investigated the effect of pregnancy on slow cortical potentials and reaction time in migraine patients and healthy controls. Four groups were examined: 14 pregnant migraine patients, 12 non-pregnant migraine patients, 15 pregnant healthy women and 16 non-pregnant healthy women aged 19-38 years. Two recordings were performed in the pregnant subjects: in the 36th week of gestation and 4 weeks after delivery. The nonpregnant subjects were recorded at the same time interval of 8 weeks. Pregnant migraine patients showed significantly fewer migraine days during the third trimester of pregnancy and returned to nearly the former level 4 weeks post delivery. Non-pregnant migraine patients demonstrated a significant reduction of migraine days at the second measurement. There was no effect of pregnancy on CNV amplitudes, but there was an effect of pregnancy on the habituation coefficient and reaction time of migraine patients. Faster habituation from a higher preactivation level was found. As an explanation for the changed habituation level we favour the model of correlation between preactivation level and habituation level, the so-called law of initial value. We found a correlation between preactivation level and habituation. Our study confirms a specific effect of pregnancy on slow cortical potentials in migraine patients.

Random Number Generation in Bilingual Balinese and German Students: Preliminary Findings from an Exploratory Cross-Cultural Study:

Verbal random number generation is a procedurally simple task to assess executive function and appears ideally suited for the use under diverse settings in cross-cultural research. The objective of this study was to examine ethnic group differences between young adults in Bali (Indonesia) and Kiel (Germany). 50 bilingual healthy students, 30 Balinese and 20 Germans, attempted to generate a random sequence of the digits 1 to 9. In Balinese participants, randomization was done in Balinese (native language L1) and Indonesian (first foreign language L2), in German subjects in the German (L1) and English (L2) languages. 10 of 30 Balinese (33%), but no Germans, were unable to inhibit habitual counting in more than half of the responses. The Balinese produced significantly more nonrandom responses than the Germans with higher rates of counting and significantly less occurrence of the digits 2 and 3 in L1 compared with L2. Repetition and cycling behavior did not differ between the four languages. The findings highlight the importance of taking into account culture-bound psychosocial factors for Balinese individuals when administering and interpreting a random number generation test.