Kalervo Suominen

Interictal Cardiovascular Autonomic Responses in Patients with Temporal Lobe Epilepsy

Summary: Purpose: To measure interictal cardiovascular autonomic functions in patients with either refractory or well‐controlled temporal lobe epilepsy (TLE).

Cardiovascular autonomic reflexes in brain infarction.

Background and Purpose Increased sympathetic activity is associated with cardiovascular complications in stroke, but the role of the parasympathetic nervous system has not been carefully outlined. In the present study our purpose was to assess quantitatively autonomic cardiovascular disturbances in brain infarction by measuring cardiovascular autonomic reflexes. Methods We studied the autonomic regulation of cardiovascular functions prospectively in 40 patients with brain infarction (acute phase, 1 month, and 6 months) and in 55 healthy control subjects by recording heart rate and blood pressure responses to normal and deep breathing, the Valsalva maneuver, tilting, and isometric work. Results In the acute phase, heart rate responses to normal breathing, deep breathing, the Valsalva maneuver, and tilting were significantly (P<.05) impaired in both hemispheric and brain stem infarctions, thus indicating hypofunction of the parasympathetic nervous system. At 1 month heart rate responses to normal breathing (brain stem, P<.05), the Valsalva maneuver (brain stem, P<.01), and tilting (hemispheric, P<.05) were still significantly lower than those of the control subjects, but at 6 months significant suppression of the response was found only in tilting (hemispheric, P<.05). Conclusions These findings suggest that in addition to the previously well‐established sympathetic hyperfunction, brain infarction also seems to cause parasympathetic hypofunction, which may be involved in cardiovascular and other known manifestations of autonomic failure associated with stroke. (Stroke. 1994;25:787‐792.)

Deficient auditory processing in children with Asperger Syndrome, as indexed by event-related potentials.

Asperger Syndrome (AS) is characterized by normal language development but deficient understanding and use of the intonation and prosody of speech. While individuals with AS report difficulties in auditory perception, there are no studies addressing auditory processing at the sensory level. In this study, event-related potentials (ERP) were recorded for syllables and tones in children with AS and in their control counterparts. Children with AS displayed abnormalities in transient sound-feature encoding, as indexed by the obligatory ERPs, and in sound discrimination, as indexed by the mismatch negativity. These deficits were more severe for the tone stimuli than for the syllables. These results indicate that auditory sensory processing is deficient in children with AS, and that these deficits might be implicated in the perceptual problems encountered by children with AS.

Infra-Slow EEG Fluctuations Are Correlated with Resting-State Network Dynamics in fMRI

Ongoing neuronal activity in the CNS waxes and wanes continuously across widespread spatial and temporal scales. In the human brain, these spontaneous fluctuations are salient in blood oxygenation level-dependent (BOLD) signals and correlated within specific brain systems or “intrinsic-connectivity networks.” In electrophysiological recordings, both the amplitude dynamics of fast (1–100 Hz) oscillations and the scalp potentials per se exhibit fluctuations in the same infra-slow (0.01–0.1 Hz) frequency range where the BOLD fluctuations are conspicuous. While several lines of evidence show that the BOLD fluctuations are correlated with fast-amplitude dynamics, it has remained unclear whether the infra-slow scalp potential fluctuations in full-band electroencephalography (fbEEG) are related to the resting-state BOLD signals. We used concurrent fbEEG and functional magnetic resonance imaging (fMRI) recordings to address the relationship of infra-slow fluctuations (ISFs) in scalp potentials and BOLD signals. We show here that independent components of fbEEG recordings are selectively correlated with subsets of cortical BOLD signals in specific task-positive and task-negative, fMRI-defined resting-state networks. This brain system-specific association indicates that infra-slow scalp potentials are directly associated with the endogenous fluctuations in neuronal activity levels. fbEEG thus yields a noninvasive, high-temporal resolution window into the dynamics of intrinsic connectivity networks. These results support the view that the slow potentials reflect changes in cortical excitability and shed light on neuronal substrates underlying both electrophysiological and behavioral ISFs.

Interictal cardiovascular autonomic responses in patients with epilepsy.

Summary: Purpose: To evaluate the interictal autonomic nervous system function in 84 patients with epilepsy: 37 with newly diagnosed, previously untreated epilepsy, and 47 patients receiving long‐term carbamazepine (CBZ), phenytoin (PHT), or valproate (VPA) monotherapy, or CBZ plus PHT, or CBZ plus VPA for their seizure disorder.

Automatic analysis and monitoring of burst suppression in anesthesia

Objective.We studied the spectral characteristics of the EEGburst suppression patterns (BSP) of two intravenous anesthetics,propofol and thiopental. Based on the obtained results, we developed amethod for automatic segmentation, classification and compactpresentation of burst suppression patterns. Methods.The spectralanalysis was performed with the short time Fourier transform and withautoregressive modeling to provide information of frequency contents ofbursts. This information was used when designing appropriate filters forsegmentation algorithms. The adaptive segmentation was carried out usingtwo different nonparametric methods. The first one was based on theabsolute values of amplitudes and is referred to as the ADIF method. Thesecond method used the absolute values of the Nonlinear Energy Operator(NLEO) and is referred to as the NLEO method. Both methods have beendescribed earlier but they were modified for the purposes of BSPdetection. The signal was classified to bursts, suppressions andartifacts. Automatic classification was compared with manualclassification. Results.The NLEO method was more accurate,especially in the detection of artifacts. NLEO method classifiedcorrectly 94.0% of the propofol data and 92.8% of thethiopental data. With the ADIF method, the results were 90.5% and88.1% respectively. Conclusions.Our results show thatburst suppression caused by the different anesthetics can be reliablydetected with our segmentation and classification methods. The analysisof normal and pathological EEG, however, should include information ofthe anesthetic used. Knowledge of the normal variation of the EEG isnecessary in order to detect the abnormal BSP of, for instance, seizurepatients.

Neurophysiologic correlates of deficient phonological representations and object naming in prematurely born children.

OBJECTIVE The aim of this follow-up study was to evaluate the development of object naming ability and auditory processing in prematurely born children. Furthermore, we investigated whether the mismatch negativity (MMN) parameters at the age of 4 years correlate with the MMN parameters and naming ability at the age of 6 years. METHODS Twelve very low birth weight (VLBW) preterm children (mean age 5 years 7 months) and matched controls were studied. Object naming was measured by the Boston naming test. Auditory event-related potentials (ERPs), especially the MMN, were recorded for Finnish syllables (standard /taa/; deviants /ta/ and /kaa/) in an oddball paradigm. RESULTS VLBW preterm children scored significantly lower in the object naming test than their controls. The MMN amplitude for consonant change was significantly smaller in the preterm group compared to the controls. The MMN amplitude at the age of 4 years correlated with the MMN amplitude at the age of 6 years. Furthermore, absence of the MMN at the age of 4 years predicted naming difficulties at the age of 6 years. CONCLUSIONS VLBW preterm children with a difficulty to preattentively discriminate changes in syllables, as indexed by the diminished change detection response, MMN, seem to have sustained naming difficulty. Therefore, it is reasonable to record the MMN along with the language development from infancy, in order to identify the children at risk for language deficiencies and to provide appropriate rehabilitation.

BOLD signal increase preceeds EEG spike activity—a dynamic penicillin induced focal epilepsy in deep anesthesia

In 40-60% of cases with interictal activity in EEG, fMRI cannot locate any focus or foci with simultaneous EEG/fMRI. In experimental focal epilepsy, a priori knowledge exists of the location of the epileptogenic area. This study aimed to develop and to test an experimental focal epilepsy model, which includes dynamic induction of epileptic activity, simultaneous EEG/fMRI, and deep anesthesia. Reported results are from seven pigs (23 +/- 2 kg) studied under isoflurane anesthesia (1.2-1.6 MAC, burst-suppression EEG) and muscle relaxant. Hypo- and hypercapnia were tested in one pig. Penicillin (6000 IU) was injected via a plastic catheter (inserted into the somatosensory cortex) during fMRI (GRE-EPI, TE = 40 ms, 300 ms/two slices, acquisition delay 1700 ms) in 1.5 T (N = 6). Epileptic spikes between acquisition artifacts were reviewed and EEG total power calculated. Cross-correlation between voxel time series and three model functions resembling induced spike activity were tested. Activation map averages were calculated. Development of penicillin induced focal epileptic activity was associated with linear increase and saturation up to approximately 10-20%, in BOLD activation map average. Its initial linear increase reached 2.5-10% at the appearance of the first distinguished spike in ipsilateral EEG in all six animals. Correlated voxels were located mainly in the vicinity of the penicillin injection site and midline, but few in the thalamus. In conclusion, development of focal epileptic activity can be detected as a BOLD signal change, even preceding the spike activity in scalp EEG. This experimental model contains potential for development and testing different localization methods and revealing the characteristic time sequence of epileptic activity with fMRI during deep anesthesia.

Atypical perceptual narrowing in prematurely born infants is associated with compromised language acquisition at 2 years of age

BackgroundEarly auditory experiences are a prerequisite for speech and language acquisition. In healthy children, phoneme discrimination abilities improve for native and degrade for unfamiliar, socially irrelevant phoneme contrasts between 6 and 12 months of age as the brain tunes itself to, and specializes in the native spoken language. This process is known as perceptual narrowing, and has been found to predict normal native language acquisition. Prematurely born infants are known to be at an elevated risk for later language problems, but it remains unclear whether these problems relate to early perceptual narrowing. To address this question, we investigated early neurophysiological phoneme discrimination abilities and later language skills in prematurely born infants and in healthy, full-term infants.ResultsOur follow-up study shows for the first time that perceptual narrowing for non-native phoneme contrasts found in the healthy controls at 12 months was not observed in very prematurely born infants. An electric mismatch response of the brain indicated that whereas full-term infants gradually lost their ability to discriminate non-native phonemes from 6 to 12 months of age, prematurely born infants kept on this ability. Language performance tested at the age of 2 years showed a significant delay in the prematurely born group. Moreover, those infants who did not become specialized in native phonemes at the age of one year, performed worse in the communicative language test (MacArthur Communicative Development Inventories) at the age of two years. Thus, decline in sensitivity to non-native phonemes served as a predictor for further language development.ConclusionOur data suggest that detrimental effects of prematurity on language skills are based on the low degree of specialization to native language early in development. Moreover, delayed or atypical perceptual narrowing was associated with slower language acquisition. The results hence suggest that language problems related to prematurity may partially originate already from this early tuning stage of language acquisition.

Cardiovascular autonomic dysfunction correlates with brain MRI lesion load in MS

OBJECTIVE The aim of the present study was to investigate the cardiovascular autonomic control in clinically definite multiple sclerosis (MS) patients with a standardised battery of cardiovascular tests and to correlate these findings with the brain magnetic resonance imaging (MRI) lesion load. METHODS Fifty-one patients with MS and 50 healthy controls were studied. Brain MRI was performed in all patients showing typical MS lesions. The cardiovascular tests were carried out using a standardised battery. RESULTS Heart rate (HR) responses to deep breathing (P < 0.05) and tilt table testing (P < 0.001) were significantly decreased in MS patients when compared to those of the controls. Blood pressure (BP) responses in the tilt table test were also impaired in MS patients (diastolic P < 0.001, systolic P < 0.05). Of the different brain areas investigated the total volume of the midbrain MRI lesions (P < 0.05) was the one most clearly associated with the impaired BP responses. CONCLUSIONS MS results in both reduced HR variation and decreased BP reactions indicating disturbed cardiovascular regulation. In particular, the midbrain lesions found in MS are associated with cardiovascular dysfunction.