Biomedical subjects

Michael Siniatchkin

Publications and source records attributed to Michael Siniatchkin.

8 recordsLinked to original sources

PubMed2006

Spreading photoparoxysmal EEG response is associated with an abnormal cortical excitability pattern.

Photosensitivity or photoparoxysmal response (PPR) is a highly heritable electroencephalographic trait characterized by an abnormal cortical response to intermittent photic stimulation (IPS). In PPR-positive individuals, IPS induces spikes, spike-waves or intermittent slow waves. The PPR may be restricted to posterior visual areas (i.e. local PPR with occipital spikes only) or spread to anterior non-visual cortical regions (i.e. PPR with propagation). The mechanisms underlying the PPR and causing its spread remain to be clarified. In unmedicated PPR-positive individuals and PPR-negative control participants without any history of previous seizures, we used focal transcranial magnetic stimulation (TMS) to investigate the excitability of the visual or primary motor cortex (M1). In the first experiment [18 healthy control subjects (i.e. without PPR in electroencephalography: 6 females, mean age 26.5 +/- 7.34 years) and 17 healthy participants with PPR (7 females, mean age 25.18 +/- 12.2 years) were studied], occipital TMS was used to elicit phosphenes or to suppress the visual perception of letter trigrams. PPR-positive individuals with propagation had lower phosphene thresholds and steeper stimulus-response curves than individuals without PPR or with occipital spikes only. Occipital TMS also induced a stronger suppression of visual perception in PPR-positive subjects with propagation relative to subjects without PPR or with occipital spikes. In the second experiment, we applied TMS over the right M1 without concurrent IPS and measured the motor threshold, the stimulus response curve, and the duration of the cortical silent period (CSP) in PPR positive individuals with propagation and in PPR-negative control participants [15 right-handed healthy subjects without PPR (3 males, mean age 17.7 +/- 3.6 years) and 14 right-handed healthy individuals showing a PPR with propagation (3 males, mean age 17.4 +/- 3.9 years)]. PPR-positive individuals showed no changes in these excitability measures relative to the PPR-negative control participants. We also measured the modifiability of the CSP by continuous IPS at a frequency of 18 or 50 Hz. While IPS reduced the duration of the CSP in PPR-negative control subjects, IPS had no effect on the duration of the CSP in PPR-positive individuals. Our results provide first time evidence that the propagation of the PPR is associated with increased excitability of the occipital but not the motor cortex. The stronger inhibitory effect of TMS on visual perception and the failure of IPS to shorten the CSP in PPR-positive participants may possibly reflect adaptive changes that prevent the provocation of seizures during the PPR.

Adolescent↗

PubMed2006

A single dose of sulthiame induces a selective increase in resting motor threshold in human motor cortex: A transcranial magnetic stimulation study.

Sulthiame is a carbonic anhydrase inhibitor that is widely used to treat partial and myoclonic seizures. In 11 healthy adults, we applied transcranial magnetic stimulation (TMS) to the primary motor cortex. Using a cross-over study design, we found that a single oral dose of sulthiame (5 mg/kg) produced a significant increase of resting motor threshold relative to placebo. No other TMS measure of corticomotor excitability was altered after a single dose of sulthiame. The selective increase in motor threshold suggests that sulthiame produces its antiepileptic effect by reducing the axonal excitability of cortical neurons.

Administration, Oral↗

PubMed2006

Neurophysiological reactivity before a migraine attack.

Migraine patients are characterized by increased amplitudes and reduced habituation of the contingent negative variation (CNV) response, especially before a migraine attack. As shown previously, migraine provoking and precipitating agents can cause CNV abnormalities. However, it is unclear whether the temporal relation to the migraine attack determines how the brain reacts to a migraine precipitant. In this study, experimentally-induced achievement stress, one of the typical precipitants for migraine, was examined for its effects upon the CNV response. CNV was recorded during conditions of rest and stress, both before and after a migraine attack, as well as during a headache-free interval. The neurophysiological reactivity to stress in migraineurs was compared with those of healthy subjects. Before a migraine attack, migraine patients demonstrated significantly more pronounced neurophysiological reactivity to stress: the amplitude of the early CNV component was more increased and its habituation was more reduced in the stress condition, especially 1-3 days before an attack compared with changes of CNV amplitudes and habituation under stress obtained after an attack, during the headache-free interval, or in healthy controls. The study demonstrates that the brain of migraine patients is characterized by increased susceptibility to migraine provoking agents before an actual attack.

Adult↗

PubMed2005

Are migraineurs hypersensitive? A test of the stimulus processing disorder hypothesis.

The concept of hypersensitivity in migraineurs was advanced mainly on the basis of studies on information processing in which increased amplitudes and reduced habituation in cortical evoked and event related potentials were found in migraine sufferers. The present investigation examined whether migraineurs exhibit hypersensitivity within three different experimental paradigms and various non electrocortical response parameters. Samples of 24 migraine, 19 tension-type headache sufferers, and 24 normal controls were compared regarding their subjective estimation of intensity and discomfort due to visual and acoustical stimuli. Subjects also participated in an experiment using the eyeblink startle response paradigm. In a last experimental task the Stroop test was applied. The trait variables emotionality, arousal, and extraversion were also measured. None of the experimental tasks revealed the predicted hypersensitivity of migraineurs in relation to the control samples. The series of experiments was conducted a second time with half of the participants in order to replicate the findings. The conclusions remained the same. The results of earlier studies on cortical processing can not be interpreted as demonstrating general hypersensitivity in the sense of a dispositional trait in migraine afflicted individuals irrespective of the involved response system.

Acoustic Stimulation↗

PubMed2002

Slow cortical potentials in migraine families are associated with psychosocial factors.

OBJECTIVE: The aim of the study was the determination of the relationships between neurophysiological and psychosocial factors within the pathogenesis of migraine. METHODS: The contingent negative variation (CNV), parent-child interactions and theirs relationship were investigated in 30 families with a migraine child and 20 healthy families. RESULTS: (1) None of the groups of children, independent of diagnosis, differed according to amplitude or habituation of the CNV. (2) Parents from migraine families exerted significantly more control over migraine children compared with interactions with healthy brothers/sisters. (3) The strong relation between CNV habituation/amplitude and abnormal pattern of parent-child interactions (especially overwhelming dominance and control) was found only for young migraineurs. This relation was not seen in healthy families or for healthy siblings of migraine children. CONCLUSION: This study provides significant evidence for a strong influence of family interactions on the development and maintenance of neurophysiological abnormalities in the migraineous headache. The role of psychosocial factors in the etiopathogenesis of migraine has to be investigated in further studies in more detail.

Adult↗

PubMed2002

On the pathophysiology of migraine--links for "empirically based treatment" with neurofeedback.

Psychophysiological data support the concept that migraine is the result of cortical hypersensitivity, hyperactivity, and a lack of habituation. There is evidence that this is a brain-stem related information processing dysfunction. This cortical activity reflects a periodicity between 2 migraine attacks and it may be due to endogenous or exogenous factors. In the few days preceding the next attack slow cortical potentials are highest and habituation delay experimentally recorded during contingent negative variation is at a maximum. These striking features of slow cortical potentials are predictors of the next attack. The pronounced negativity can be fed back to the patient. The data support the hypothesis that a change in amplitudes of slow cortical potentials is caused by altered habituation during the recording session. This kind of neurofeedback can be characterized as "empirically based" because it improves habituation and it proves to be clinically efficient.

Adolescent↗

PubMed2002

[Role of family in development of neurophysiological manifestations in children with migraine].

Migraine is a familial disorder. The aim of this study was to compare the relationship between specific neurophysiologic pathogenetic mechanisms of migraine such as abnormal information processing and enhanced cortical excitability on the one hand, and parent-child-interactions and personality traits such as neuroticism and extraversion on the other hand in migraine and healthy families. The correlation and factor analyses demonstrated that the stronger the control over a child and the more intensive the suppression of a child's independence by a parent during a stressful situation in migraine families, the more pronounced the loss of habituation of the contingent negative variation (CNV), and the greater the neuroticism in a migraine child. The CNV amplitude was independent of psychosocial conditions in the family but represented similarities in information processing between parents and their children suffering from migraine. This could be possibly explained by genetic influences on information processing in migraine. In healthy families only the relationship between parameters of parent-child-interaction could be observed. This investigation demonstrates that the neurophysiological disposition to a migraine attack as well as personality traits in migraine could be influenced by psychosocial factors such as parent-child interactions and that different parameters of information processing in headache patients are related to either non-genetic familial conditions (habituation) or functional genetic factors (amplitude).

Arousal↗

PubMed2001

Contingent negative variation in subjects at risk for migraine without aura.

Migraine is a complex disease with a significant genetic background. One possible strategy to investigate the genetics of migraine is the evaluation of functional vulnerability markers or biological elementary endophenotypes in individuals with the greatest probability of developing the disorder (high-risk design). In this study the contingent negative variation (CNV) was recorded in 35 high-risk subjects with a positive family history of migraine without aura (FHP), 35 low-risk individuals without a positive family history (FHN), and 35 migraineurs (migraine without aura). FHP subjects and migraine patients differed significantly from FHN individuals with regard to amplitude and habituation slope of the early CNV component (initial CNV or iCNV). FHP participants demonstrated the same iCNV abnormalities and distribution among iCNV characteristics as migraineurs. The amplitude of the iCNV correlated significantly with the relative number of subjects suffering from migraine among first- and second-degree relatives. The higher the density of affected individuals in the family, the more pronounced were the CNV abnormalities in relatives. This study provides evidence that the familial factor contributes to the abnormal amplitude, and to a lesser degree, habituation of the iCNV, and that the iCNV may be used as a functional-genetic vulnerability marker in further research of migraine genetics.

Adolescent↗