Auditory information processing in sleep: late cortical potentials in an oddball paradigm.

Information processing of auditory stimuli in sleeping healthy volunteers is studied by means of an oddball paradigm. Latencies of the early (N1P2) complex are affected by NREM sleep depth and show a progressive slowing. The amplitude of the early N1 component depends on stimulus type and probability and is increased following deviant stimuli. In strict comparison with waking, late responses (N2-P3) complex only follows deviant stimuli. Both latencies and amplitude increase more in NREM than in REM sleep. Thus the early response is mainly affected by vigilance, the late response mainly depends on stimulus type. Results are discussed in terms of comparison processing, context updating and orienting response patterning hypotheses put forward in cognitive psychophysiology.

Auditory information processing in sleep: habituation to repetitive stimuli.

Habituation to evoked responses is obvious in waking but still controversial in sleep. Single-response analysis proves short-term habituation of auditory evoked potentials in stage 2 NREM sleep. The data are discussed referring to the two-system hypothesis of sensory processing in sleep and to DC instability and sleep maintenance mechanisms in stage 2 NREM. It is suggested that information processing might continue in sleep.

Lack of asymmetry of middle cerebral artery blood velocity in unilateral migraine.

BACKGROUND AND PURPOSE: A recent transcranial Doppler study found reduced blood velocity in seven patients during migraine attacks in the middle cerebral artery at the headache side. This would implicate vasodilation of the middle cerebral artery in the pathogenesis of headache in migraine. We attempted to confirm this finding. METHODS: We determined blood velocity with transcranial Doppler ultrasonography in the middle cerebral arteries of 51 migraine patients with unilateral headache (5 with aura, 46 without aura) and of 14 patients with bilateral headache, during and outside attacks. During attacks, median time from onset of attack to transcranial Doppler examination was 6 hours (range, 1 to 35 hours). RESULTS: We found no difference between blood velocity at the headache and nonheadache sides nor between blood velocity during and outside attacks. Similar results were obtained in a subgroup of 11 patients who were investigated in the first 4 hours of an attack. There were also no differences between attacks with unilateral or bilateral headache. CONCLUSIONS: We cannot support the hypothesis that migraine is associated with vasodilation of the middle cerebral artery ipsilateral to the headache.

Antimigraine drug sumatriptan increases blood flow velocity in large cerebral arteries during migraine attacks.

Sumatriptan, a novel selective 5-hydroxytryptamine1d (5-HT1d) receptor agonist, which is highly effective in the acute treatment of migraine attacks, blocks dural neurogenic plasma extravasation and constricts cranial blood vessels in animal experiments. We measured intra- and extracranial blood flow velocities (BFV) with a transcranial Doppler device in 67 patients during a spontaneous migraine attack, before and after treatment with 3 mg or 6 mg subcutaneous sumatriptan or placebo. Sumatriptan, but not placebo, significantly increased BFV (cm/sec) in the internal carotid and middle cerebral arteries on both sides, without detectably changing the BFV in the common and external carotid arteries. The rise in BFV increased with the dose of sumatriptan, parallel to an increase in proportion of patients improved. There were no significant changes in heart rate, blood pressure, or respiratory frequency after treatment with sumatriptan. The increase in BFV probably reflects vasoconstriction of the large basal intracranial arteries, which may be a mechanism for the antimigraine action of sumatriptan.

Background EEG reactivity in auditory event-related potentials.

Mental activity has influences on auditory event-related potentials (AERP) as well as on some EEG rhythms, notably the alpha rhythm. In this study, background reactivity (BR) of the EEG was investigated in the context of AERPs. Single responses of 14 healthy subjects were analysed in 3 reaction time AERP experiments of increasing difficulty: the first involved one type of tone delivered at random intervals, the second offered two types of tone (an "oddball" design), and the third offered 3 types of tone. Averages were formed and subtracted from the separate responses to reduce their contribution to the EEG. The 1526 msec EEG epoch was divided in 9 overlapping periods, and averaged power spectra were calculated for these periods. Changes in area of the delta, theta, alpha and beta bands in the course of the epoch were calculated. Background alpha and beta activity decreased following infrequent but not following frequent tones. The decrease was larger for more difficult tasks and reached a maximum in the period in which the AERP P3 and N3 peaks fell. Delta and theta powers showed increases rather than decreases; these could be attributed to the contribution of AERP activity to total EEG power. No clear relationships were found between the amount of background reactivity and peak latencies or reaction times. The occurrence of background reactivity, not apparent in an average, shows that the averaged AERP reveals only part of the EEG changes related to mental activity. Background reactivity proved to be more sensitive to task difficulty than P300 latency. The results are discussed in the context of the additive model of evoked potentials.

What is the validity of an "abnormal" evoked or event-related potential in MS? Auditory and visual evoked and event-related potentials in multiple sclerosis patients and normal subjects.

The predictive validity of evoked potentials (EPs) and event-related potentials (ERPs) in multiple sclerosis (MS) has not yet been fully investigated, as only the sensitivity of these tests has sofar been reported. EPs (short, middle and long latency auditory evoked potentials and visual evoked potentials) and ERPs (visual and auditory) were studied in 19 controls and 30 multiple sclerosis (MS) patients. Abnormality thresholds of peak latencies were defined on the basis of the mean plus 2 or 3 standard deviations, based on data from the control group. The effects of changing the latency thresholds and including the absence of peaks in the abnormality definition were assessed. In accordance with earlier reports we found a high sensitivity (up to 93% for bimodal combined EPs and 47% for combined ERPs). False positive rates of separate peaks were low and conformed to expectation. However, combining separate peak measurements increased false positive rates of EPs and ERPs to unacceptably high levels (up to 58% for combined EPs and 32% for combined ERPs). Positive likelihood ratios for bimodal EPs were low (between 1.6 and 4.0, depending on the abnormality definition). They ranged from 1.4 to 2.2 for bimodal ERPs. Abnormal combined EPs or ERPs were therefore not the reliable indicators of functional damage that they are supposed to be. Separate EPs were much more reliable in this respect. ERPs failed to distinguish between the groups, either separately or in combination. Changing the latency threshold and including absent peaks in the abnormality definition influenced the abnormality rates in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Are event-related potentials in multiple sclerosis indicative of cognitive impairment? Evoked and event-related potentials, psychometric testing and response speed: a controlled study.

Bimodal event-related potentials (ERPs), together with evoked potentials (EPs), measures of motor speed (tapping test, EMG latencies and reaction times (RT)), and psychometric test results were studied in a group of 30 multiple sclerosis (MS) patients and 19 controls. ERPs have been advocated as objective tests of cognitive function. In the present study ERPs were compared with the results of psychometric tests, which have a proven validity in measuring aspects of cognitive function that are important in daily life. Abnormal EMG, RT and tapping speed confirmed that motor aspects of performance were slowed in the MS group. In contrast, cognitive non-motor variables such as Raven-IQ and MQ were not significantly abnormal. The proportions of abnormal ERP N2 and P3 latencies did not differ between the groups. It is concluded that the slow performance of MS subjects is therefore most likely not due to cognitive speed decrement, but to motor, executive impairments. No significant relationships between ERP latencies and psychometric test results were found. This held even for a subgroup of 5 MS patients with psychometrically established cognitive impairments. Based on these results, we query the relevance of ERPs as subtle indicators of cognitive impairment in MS.

Blood flow velocities in the vertebrobasilar system during migraine attacks--a transcranial Doppler study.

In this study, blood flow velocity in the basilar artery and both vertebral and middle cerebral arteries was measured with a transcranial Doppler device in 23 migraineurs during and outside a migraine attack. The aim of the study was to compare blood flow velocities during and outside an attack and to examine vascular reactivity to voluntary hyperventilation during both conditions. No differences in blood flow velocity were found. Although blood pressure was increased and end-expiratory CO2 decreased during the attack, this exerted no influence on blood flow velocity. Neither was a difference in vascular reactivity to voluntary hyperventilation detected between the two conditions. These findings support the notion of functional integrity of the examined large arteries during migraine attacks without aura.

Vascular reactivity during migraine attacks: a transcranial Doppler study.

We measured vascular reactivity--expressed i) as decrease in blood flow velocity (cm/sec) per vol% CO2 decrease due to voluntary hyperventilation and ii) as increase of blood flow velocity during the first minute after resuming normal ventilation, per vol% CO2 increase--in the middle cerebral and basilar artery of 48 migraineurs with attacks without aura, and 17 normal controls. We found no differences for both determinants of vascular reactivity between migraineurs during and outside an attack, and between migraineurs and healthy volunteers. We conclude that the vasomotor reactivity is normal during migraine attacks without aura.

Blood flow velocity changes in migraine attacks--a transcranial Doppler study.

A pulsed Doppler device was used to measure blood flow velocities in the common carotid artery, the extracranial part of the internal carotid artery, the external carotid artery, the middle cerebral artery, and the anterior cerebral artery in 31 migraineurs without aura (n = 27) and with aura (n = 4), both during and outside an attack. The aims were to compare blood flow velocity during and between migraine attacks and to study asymmetries of the blood flow velocity. Compared with blood flow velocity values obtained in the attack-free interval, blood flow velocity was lower during attacks without aura in both common carotid arteries, but not in the other extra- and intracranial vessels which were examined. However, during attacks of migraine with aura, blood flow velocity tended to be lower in all examined vessels. There were no asymmetries of the blood flow velocity. We suggest that during migraine attacks without aura there is a dissociation in blood flow regulation in the common carotid and middle cerebral arteries.

The interpretation of dysprosody in patients with Parkinson's disease.

Prosodic features in the speech production of 21 patients with idiopathic Parkinson's disease were tested. The appreciation of vocal and facial expression was also examined in the same patients. Significant intergroup differences were found in the prosody production tasks but, in contrast to previous results, not in the receptive tasks on the recognition and appreciation of prosody and of facial expression. The discrepancy between the production and recognition of prosodic features does not support the suggestion that dysprosody in Parkinson's disease is necessarily a disorder of processing emotional information that could be misinterpreted as a dysarthria.

Cerebral vasculopathy associated with primary varicella infection.

A previously healthy 5-year-old boy developed cerebral vasculopathy, presenting as two episodes of acute hemiparesis 3 and 9 months, respectively, after a primary varicella infection (chickenpox). This association has not been reported before, to our knowledge, although cerebral vasculopathy is a well-known complication of herpes zoster ophthalmicus. The diagnosis was based on the presence of oligoclonal varicella-specific IgG in the cerebrospinal fluid and angiographic findings. Clinical and angiographic follow-up, and serial thymidine kinase activity levels in the cerebrospinal fluid suggested a self-limiting course of the virus-induced vasculopathy. Varicella zoster virus seems to be another potential causative agent to be considered in acute childhood hemiplegia.

Habituation of K-complexes or event-related potentials during sleep.

We examined habituation and dishabituation of evoked K-complexes (equivalent to auditory event-related potentials) during sleep. Habituation is investigated by presenting trains of stimuli with a 5 sec inter-stimulus interval and a 4 min inter-train interval. Habituation is complete by the third identical stimulus in a train and dishabituation occurs after deviant stimuli and after the inter-train interval. Although there are morphological differences between K-complexes in sleep and auditory event-related potentials in wakefulness, they share the phenomenon of habituation to repetitive events.

Cerebral venous thrombosis as presenting sign of myeloproliferative disorders.

Two patients with cerebral venous thrombosis are described. In both patients laboratory findings suggested an underlying haematological disorder and bone marrow biopsy showed a myeloproliferative disorder. Both chronic cerebral venous thrombosis and early myeloproliferative disorders are difficult to diagnose. Their combined occurrence may be less rare than is frequently supposed.