Neonatal pain-related stress,functional cortical activity and visual-perceptual abilities in school-age children born at extremely low gestational age

Children born very prematurely (?32 weeks) often exhibit visual-perceptual difficulties at school-age, even in the absence of major neurological impairment. The alterations in functional brain activity that give rise to such problems, as well as the relationship between adverse neonatal experience and neurodevelopment, remain poorly understood. Repeated procedural pain-related stress during neonatal intensive care has been proposed to contribute to altered neurocognitive development in these children. Due to critical periods in the development of thalamocortical systems, the immature brain of infants born at extremely low gestational age (ELGA; ?28 weeks) may have heightened vulnerability to neonatal pain. In a cohort of school-age children followed since birth we assessed relations between functional brain activity measured using magnetoencephalogragy (MEG), visual-perceptual abilities and cumulative neonatal pain. We demonstrated alterations in the spectral structure of spontaneous cortical oscillatory activity in ELGA children at school-age. Cumulative neonatal pain-related stress was associated with changes in background cortical rhythmicity in these children, and these alterations in spontaneous brain oscillations were negatively correlated with visual-perceptual abilities at school-age, and were not driven by potentially confounding neonatal variables. These findings provide the first evidence linking neonatal pain-related stress, the development of functional brain activity, and school-age cognitive outcome in these vulnerable children.     

Alterations in tonotopy and auditory cerebral asymmetry in schizophrenia.

BACKGROUND: Deficits in basic auditory perception have been described in schizophrenia. Previous electrophysiologic imaging research has documented a structure-function disassociation in the auditory system in schizophrenia. This study examines whether the most fundamental level of auditory cortical organization, tonotopy, is altered in schizophrenia. METHODS: The tonotopic organization for five tone frequencies in 19 patients with schizophrenia and 22 comparison subjects was evaluated using magnetoencephalography. Auditory evoked magnetic field dipole locations were examined for the N100m component for each frequency. RESULTS: The expected linear relationship between depth and frequency was found in the comparison subjects but not in the schizophrenia group (p <.004). In addition, normal anterior-posterior asymmetry of the N100m was found to be reduced at all five stimulation frequencies employed in the study (p <.04). No relationships between clinical symptom ratings and either tonotopy or asymmetry were observed. CONCLUSIONS: This finding suggests that the tonotopic organization of the auditory cortex in schizophrenia is disturbed and may help explain the relatively poor behavioral performance of schizophrenia patients on simple frequency discrimination tasks. Alterations in fundamental sensory organization may underlie or interact with higher order cognitive mechanisms to produce changes in cognitive task performance.     

A case of Panayiotopoulos syndrome showing an atypical course

We describe herein a patient with Panayiotopoulos syndrome (PS) showing an atypical course. The patient initially had seizures typical of this syndrome from 3 to 5 years of age. EEG showed right occipital high-amplitude sharp and slow-wave complexes followed by brief generalized discharges of slow waves. Sequential EEGs obtained from 5 to 11 years of age showed both multifocal discharges and generalized spike and wave complexes. With these changes in EEG findings, the patient experienced various types of seizures. The seizures were frequent and showed oculocephalic deviation followed by absence, atonic seizures, generalized tonic clonic convulsions and clonic seizures of the eyelids, which were observed between 7 and 10 years of age. Antiepileptic drugs were only partially effective for these seizures. Ictal EEG recorded at 8 years of age revealed high-voltage slow waves from the bilateral frontal and occipital regions prior to diffuse high-amplitude spike-wave bursts. At 9 years of age, magnetoencephalography (MEG) revealed the calculated dipoles of the preceding bifrontal spike-wave discharges to be in the frontal areas, while those of the following generalized spike-wave bursts were in the bilateral mid-temporal areas. In PS, reportedly, dipoles of multifocal epileptic discharges are usually located in the occipital and Rolandic areas. The unique clinical evolution in our case may be associated with the unusual frontal localization of dipoles detected by MEG.     

急性脑梗死脑磁图体感诱发磁场发生源ECD强度研究

目的:研究急性脑梗死患者脑磁图(magnetoencephalography,MEG)体感诱发磁场发生源等价电流偶极子(equivalentcurrentdipole,ECD)强度变化特征。方法:对15例急性脑梗死患者于发病后3～4周进行体感诱发磁场(SEFS)检测;同时检测16例健康志愿者作为对照。电刺激部位为腕部正中神经处,电流脉冲宽度0.3ms,刺激间隔0.5s。SEFS波峰由ECD评估。结果:所有受检者SEFs的最基本波形为M20,急性脑梗死患者患侧ECD强度减小(P<0.01)。结论:MEG可灵敏地检测出急性脑梗死患者体感皮层中枢功能损伤。     

Somatosensory evoked magnetic fields following passive movement compared with tactile stimulation of the index finger

Cortical processing of passive finger movement was assessed magnetoencephalographically in 12 healthy volunteers and compared with somatosensory evoked magnetic fields (SEF) following tactile stimulation. A new device comprising a clamp-like digit holder facilitated bilateral guidance of the briskly elevated index finger. Both passive movement and tactile stimulation induced activation of the contralateral primary somatosensory (SI) cortex, indicated by six SEF deflections with inter-individually rather consistent peak latencies of 20–230 ms following proprioceptive and 20–300 ms following tactile stimulation. SEF responses to the two stimulus modalities clearly differed with regard to peak latencies, amplitudes and orientations of equivalent current dipoles (ECDs). The strength and orientation of proprioception-related ECDs suggested sequential activation of SI generators, with possible involvement of areas 3a and/or 2 at around 20 ms, area 4 at approximate peak latencies of 65 and 100 ms and area 3b between 150 to 230 ms. Passive movement elicited additional activation of cortical regions outside SI, including the bilateral perisylvian regions and the contralateral cingulate gyrus at latencies of 40–470 and 150–500 ms respectively. The study provides new results with respect to the spatiotemporal analysis of proprioception-related cortical processing and may contribute to a better understanding of the modality-specific organization of the human somatosensory cortex. Electronic Publication     

Early cortical activities evoked by noxious stimulation in humans

Lasers can selectively activate the nociceptors of A-delta fibers. Since nociceptors in the skin are activated via temperature conduction by the laser beam, a latency jittering of cortical responses among trials would affect results obtained with a conventional averaging (C-AVE) technique. We therefore used a new method, latency-adjusted averaging (L-AVE), to investigate cortical responses to noxious laser stimulation in normal subjects. L-AVE was done by averaging trials after adjusting the latency so that the peak latency of an activity in the temporal region of all trials matched on the time axis. Both in C-AVE and in L-AVE, clear activations were found in the contralateral primary somatosensory cortex (SI) and bilateral parasylvian regions, whose activities peaked 163–181 ms after the stimulation. In addition to these three main activities, weak activities peaking at around 109–119 ms could be identified in only L-AVE in similar cortical regions. Since the direction of the source differed between early and main activities, we considered that the early weak activities were cancelled out by the later main activities with an opposite orientation. The results suggested that early cortical processing of noxious information occurs earlier than previous neurophysiological studies have estimated and that the temporal sequence of activations should be reconsidered.     

MEG localization of rolandic spikes with respect to SI and SII cortices in benign rolandic epilepsy

The purpose of this study was to study the relationship between interictal spike sources and somatosensory cortices in benign rolandic epilepsy of childhood (BREC) using a whole-scalp neuromagnetometer. We recorded spontaneous magnetoencephalography (MEG) and EEG signals and cortical somatosensory-evoked magnetic fields (SEFs) to electric stimulation of the median nerve in 9 children with BREC. Interictal rolandic discharges (RDs) and SEFs were analyzed by equivalent current dipole (ECD) modeling. Based on the orientation and locations of corresponding ECDs, we compared generators of RDs with primary (SI) and second somatosensory cortices (SII). Our results showed that RDs and SII responses had similar ECD orientation on the magnetic field maps. The ECDs of RDs were localized 15.3 +/- 1.9 and 12.2 +/- 2.8 mm anterior to SI and SII, respectively. The spatial distance on average from the location of RDs to SII (21.9 +/- 1.6 mm) cortex was significantly shorter than to SI cortex (29.7 +/- 1.7 mm) (P<0.01, Wilcoxon signed-rank test). In conclusion, the cortical generators for RDs in patients with BREC are localized in the precentral motor cortex, closer to hand SII than to SI cortex.     

脑磁图SAM分析法定位皮质运动功能初步探讨

目的利用脑磁图SAM分析法研究健康受试者运动皮质反应及其磁源影像定位价值。方法10例右利手健康受试者给予tone音刺激,受试者听到声音后右手食指触压按键感应器。以运动触发为基点进行平均,选择触发点前后的波形分别用等价电流偶极子(ECD)和合成孔径磁场测量(SAM)进行分析,最终形成三维的脑功能影像图。结果所有10例受试SAM法均定位大脑皮层中央前回,与运动皮层解剖位置一致,ECD法7例定位于中央前回运动中枢,3例定位偏差。结论脑磁图SAM分析方法可以很好地显示皮质运动反应并能对皮层运动功能进行成功定位。     

Interaural Interaction in the Human Auditory Cortex

We studied the effect of binaural, contralateral and ipsilateral stimulation on middle- and long-latency auditory-evoked magnetic fields using trains of 40-Hz clicks. The stimuli evoked both a transient response (N100m) and a 40-Hz response, which presumably reflects coalescence of middle-latency responses. Binaural stimuli elicited significantly larger 40-Hz responses and sustained fields than contralateral stimuli. N100m amplitudes did not differ between binaural and contralateral stimulation; the dipole moments were even smaller to binaural than contralateral stimuli. Responses to the ipsilateral stimuli were always the smallest.