MEG in frontal lobe epilepsies: localization and postoperative outcome

Purpose: This study aimed to analyze magnetoencephalography (MEG) localizations of epileptic clusters in different cortical regions of the frontal lobe and relate these findings to postoperative outcomes associated with frontal lobe epilepsy (FLE). Methods: Thirty‐nine patients from the Epilepsy Center of Erlangen‐Nuremberg University with or without lesions on their magnetic resonance imaging (MRI) scans underwent MEG measurements and operation and were then analyzed retrospectively. MEG data were obtained using systems with either 74 or 248 channels. Single dipole analysis assuming a spherical head model was performed for localization. Key Findings: Epileptic clusters were detected by MEG in 30 patients, corresponding to a sensitivity of 76.9%; there was a sensitivity of 66.7% (20 of 30) in patients with monofocal activity (70% had an Engel class 1 outcome) and 33.3% (10 of 30) in patients with multifocal activity (20% had an Engel class 1 outcome). Of the patients who had isolated clusters, the distance between the MEG localizations and the respective lesions was equal to or <3 cm in 90% (18 of 20) of patients (13 of them had an Engel class 1 outcome) and >3 cm in 10% (2 of 20) of patients (one of them had an Engel class 1 outcome). A statistical difference was found between the outcomes of patients with a single focus and with multiple foci (p < 0.05). Significance: Patients with a single focus had better postoperative outcomes compared with patients with multiple foci. MEG localizations close to the lesion marked the lesion or its surrounding network as epileptogenic. Therefore, source localization can provide important information for the presurgical evaluation of patients with FLE.     

Different neural pathways to negative affect in youth with pediatric bipolar disorder and severe mood dysregulation

Questions persist regarding the presentation of bipolar disorder (BD) in youth and the nosological significance of irritability. Of particular interest is whether severe mood dysregulation (SMD), characterized by severe non-episodic irritability, hyper-arousal, and hyper-reactivity to negative emotional stimuli, is a developmental presentation of pediatric BD and, therefore, whether the two conditions are pathophysiologically similar. We administered the affective Posner paradigm, an attentional task with a condition involving blocked goal attainment via rigged feedback. The sample included 60 youth (20 BD, 20 SMD, and 20 controls) ages 8–17. Magnetoencephalography (MEG) examined neuronal activity (4–50 Hz) following negative versus positive feedback. We also examined reaction time (RT), response accuracy, and self-reported affect. Both BD and SMD youth reported being less happy than controls during the rigged condition. Also, SMD youth reported greater arousal following negative feedback than both BD and controls, and they responded to negative feedback with significantly greater activation of the anterior cingulate cortex (ACC) and medial frontal gyrus (MFG) than controls. Compared to SMD and controls, BD youth displayed greater superior frontal gyrus (SFG) activation and decreased insula activation following negative feedback. Data suggest a greater negative affective response to blocked goal attainment in SMD versus BD and control youth. This occurs in tandem with hyperactivation of medial frontal regions in SMD youth, while BD youth show dysfunction in the SFG and insula. Data add to a growing empirical base that differentiates pediatric BD and SMD and begin to elucidate potential neural mechanisms of irritability.     

Impaired engagement of the ventral attentional pathway in ADHD

In the cognitive theories of Attention Deficit Hyperactivity Disorder (ADHD) impaired behavioral adjustment has been linked to a deficit in learning to detect regularities or irregularities in the environment. In the neural level, the P3 component of event-related potential (ERP) is modulated by stimulus probability and has been suggested to index activation of the ventral attention network, which constitutes the reorienting system of the human brain. To explore the cortical basis of late positive ERP components and the engagement of the ventral attentional pathway in ADHD, we used ERP recordings complemented by spatiotemporally sensitive magnetoencephalography (MEG) measurements. We followed the activation evoked by frequent Go and infrequent NoGo stimuli in 10 ADHD adults and 13 control subjects. In the ERP recordings, a prominent positive deflection was detected after the infrequent visual stimuli (late positive component, LPC) in both subject groups. In ADHD adults the difference between the responses evoked by infrequent NoGo and frequent Go stimuli was markedly reduced compared to the control group during the LPC. The MEG recordings revealed that the activation detected during the LPC was localized bilaterally in the posterior temporal cortex. Activation of the left and right temporal regions was enhanced after infrequent NoGo stimuli in both subject groups. In ADHD adults, however, the effect of stimulus frequency was less pronounced. We suggest that the activation in the superior temporal cortices during the LPC reflects the action of ventral attention network. The engagement of this stimulus-driven reorienting system is defective in ADHD.     

Sex differences in sensorimotor mu rhythms during selective attentional processing

We used magnetoencephalography to investigate the effect of directed attention on sensorimotor mu (8–12 Hz) response (mu reactivity) to non-painful electrical stimulation of the median nerve in healthy adults. Mu desynchronization in the 10–12 Hz bandwidth is typically observed during higher-order cognitive functions including selective attentional processing of sensorimotor information (Pfurtscheller, Neuper, & Krauz, 2000). We found attention-related sex differences in mu reactivity, with females showing (i) prolonged mu desynchrony when attending to somatosensory stimuli, (ii) attentional modulation of the mu response based on whether attention was directed towards or away from somatosensory stimuli, which was absent in males, and (iii) a trend for greater neuronal excitability of the primary somatosensory region suggesting greater physiological responsiveness to sensory stimulation overall. Our findings suggest sex differences in attentional control strategies when processing somatosensory stimuli, whose salience may be greater for females. These sex differences in attention to somatosensory stimuli may help elucidate the well-documented sex biases in pain processing wherein females typically report greater sensitivity to experimental and clinical pain.     

Spatiotemporal frequency characteristics of cerebral oscillations during the perception of fundamental frequency contour changes in one-syllable intonation

Accurate perception of fundamental frequency (F0) contour changes in the human voice is important for understanding a speaker's intonation, and consequently also his/her attitude. In this study, we investigated the neural processes involved in the perception of F0 contour changes in the Japanese one-syllable interjection “ne” in 21 native-Japanese listeners. A passive oddball paradigm was applied in which “ne” with a high falling F0 contour, used when urging a reaction from the listener, was randomly presented as a rare deviant among a frequent “ne” syllable with a flat F0 contour (i.e., meaningless intonation). We applied an adaptive spatial filtering method to the neuromagnetic time course recorded by whole-head magnetoencephalography (MEG) and estimated the spatiotemporal frequency dynamics of event-related cerebral oscillatory changes in the oddball paradigm. Our results demonstrated a significant elevation of beta band event-related desynchronization (ERD) in the right temporal and frontal areas, in time windows from 100 to 300 and from 300 to 500 ms after the onset of deviant stimuli (high falling F0 contour). This is the first study to reveal detailed spatiotemporal frequency characteristics of cerebral oscillations during the perception of intonational (not lexical) F0 contour changes in the human voice. The results further confirmed that the right hemisphere is associated with perception of intonational F0 contour information in the human voice, especially in early time windows.     

Magnetoencephalography in pediatric lesional epilepsy surgery

This study was performed to assess the usefulness of magnetoencephalography (MEG) as a presurgical evaluation modality in Korean pediatric patients with lesional localization-related epilepsy. The medical records and MEG findings of 13 pediatric patients (6 boys and 7 girls) with localization-related epilepsy, who underwent epilepsy surgery at Seoul National University Children's Hospital, were retrospectively reviewed. The hemispheric concordance rate was 100% (13/13 patients). The lobar or regional concordance rate was 77% (10/13 patients). In most cases, the MEG spike sources were clustered in the proximity of the lesion, either at one side of the margin (nine patients) or around the lesion (one patient); clustered spike sources were distant from the lesion in one patient. Among the patients with clustered spike sources near the lesion, further extensions (three patients) and distal scatters (three patients) were also observed. MEG spike sources were well lateralized and localized even in two patients without focal epileptiform discharges in the interictal scalp electroencephalography. Ten patients (77%) achieved Engel class I postsurgical seizure outcome. It is suggested that MEG is a safe and useful presurgical evaluation modality in pediatric patients with lesion localization-related epilepsy.     

抑郁症患者识别悲伤表情刺激时磁源性影像动态变化的性别差异

目的 本研究利用脑磁图(MEG)技术以及表情类型识别实验范式来探讨抑郁症患者识别面部悲伤动态表情时功能网络神经基础的性别差异.方法 利用脑磁图检测12例女性抑郁症患者以及11名年龄、受教育年限相匹配的男性抑郁症患者以及正常对照者识别动态表情视频时的脑部反应.结果 与男性抑郁症患者相较,女性抑郁症患者识别面部悲伤动态表情时活动增强的脑区依次为双侧额下回(x,y,z=58/-60,12/22,20/20,T=2.17,1.88)、左前扣带回(x,y,z=64,12,4,T=2.37)、双侧额上回(x,y,z=30/-24,64/-4,0/50,T=2.86,2.36)、左脑干(x,y,z=-12,-16,-18,T=1.96)、右额中回(x,y,z=40,60,4,T=2.22)、双侧中央前回(x,y,z=-62/56,16/10,10/8.T=1.99,2.65)、左海马(x,y,z=-26,-14,-20,T=1.77)、左海马旁回(x,y,z=-16,-12,-20,T=1.72)、右枕中回(x,y,z=50,-76,-14,T=1.75)等;活动减弱的脑区依次为右颞上回(x,y,z=68,-18,2,T=1.85)、右海马旁回(x,y,z=20,-36,-14,T=1.92)、左楔叶(x,y,z=-6,-98,14,T=2.46)、双侧颞中回(x,y,z=52/-34,-80/-62,20/28,T=1.95,2.57)、左楔前叶(x,y,z=-40,-74,38,T=2.58)、右海马旁回(x,y,z=24,-32,-18,T=2.05)等.设P＜0.05时,均差异具有显著性.结论 本研究结果提示抑郁症患者的悲伤情绪识别功能网络存在显著的性别差异.

Abstract：

Objective To explore the gender differences of brain activation between patients with depression in recognition of dynamically sad expression with magnetoencephalography (MEG) technology and the paradigm of expressional experiment,and further to examine its neurological basis. Methods Brain activities were detected using MEG during the recognition of dynamic facial video with 12 female depressed patients, 11 male depressed patients, and their corresponding normal controls matched by age and education. Results Compared with male depression,female depression showed increased activation during different time periods were in turn as follows: bilateral inferior frontal gyrus ( x, y, z = 58/- 60,12/22,20/20, T = 2.17,1.88 ), left anterior cingulate gyrus ( x, y, z = 64,12,4, T = 2.37 ), bilateral superior frontal gyrus ( x, y, z= 30/-24,64/- 4,0/50, T = 2.86,2.36 ),the left brainstem( x, y,z = - 12, - 16, - 18 ,T = 1.96) ,right middle frontal gyrus( x,y,z =40,60,4,T = 2.22 ),bilateral precentral gyrus(x,y,z = -62/56, 16/10, 10/8. T = 1.99,2.65 ) ,left hippocampus ( x,y,z = - 26,- 14, -20,T = 1.77) ,left parahippocampal gyrus(x,y,z = - 16, - 12, -20,T = 1.72) ,right middle occipital gyrus( x ,y ,z = 50, -76, -14 ,T = 1. 75 ),while the decreased brain activation were in turn in right superior temporal gyrus ( x, y, z = 68, - 18,2, T = 1.85 ), right parahippocampal gyrus ( x, y, z = 20, - 36, - 14, T = 1.92 ), left cuneus( x,y,z = -6, -98,14,T =2.46) ,bilateral temporal middle gyrus( x,y,z =52/-34, - 80/-62,20/28,T = 1.95,2.57 ), left pre-cuneus ( x, y, z = - 40, - 74,38, T = 2.58 ), right hippocampus( x, y, z = 24, - 32, - 18,T = 2.05 ) in recognition of dynamically sad expression. ( p ＜ 0. 05, corrected). Conclusion The data suggest that there may be significant gender differences of functional network in depressed patients during recognizing dynamical sad facial expression.     

抑郁症识别正性情绪的脑磁源性影像动态变化

目的 利用磁源性影像(Magnetic source imaging,MSI)技术观察抑郁症患者识别正性动态情绪的神经网络动态变化的特点.方法 利用脑磁图检测12例抑郁症患者及12名年龄、性别、受教育年限近似匹配的健康对照者识别正性动态情绪视频时的脑部反应.结果 与正常对照组相比,抑郁症组识别正性面部情绪时,活动减弱的脑区依次主要为右顶下小叶(t=3.94)、右缘上回(t=3.59)、双侧后扣带回(t=5.04,t=4.85)、左楔前叶(t=3.84)、左颞上回(t=3.58)等;活动增强的脑区依次主要为双侧海马回(t=2.13,t=2.56)、左侧杏仁核(t=2.41)、双侧钩回(t=2.33,t=2.44)、右前扣带回(t=2.15)、左梭状回(t=3.33)等.这些脑区在不同时间段有相应脑区激活异常.设P<0.05时,均差异具有显著性.结论 抑郁症患者的颞内侧皮质、顶叶功能减弱及边缘系统等功能增强与正性情绪识别功能减弱有关,其脑磁源性影像变化特征较正常人有很显著的差异.     

Intermittent theta burst stimulation over primary motor cortex enhances movement-related beta synchronisation

Objective

The objective of this study is to investigate how transcranial magnetic intermittent theta burst stimulation (iTBS) with a prolonged protocol affects human cortical excitability and movement-related oscillations.

Methods

Using motor-evoked potentials (MEPs) and movement-related magnetoencephalography (MEG), we assessed the changes of corticospinal excitability and cortical oscillations after iTBS with double the conventional stimulation time (1200 pulses, iTBS1200) over the primary motor cortex (M1) in 10 healthy subjects. Continuous TBS (cTBS1200) and sham stimulation served as controls.

Results

iTBS1200 facilitated MEPs evoked from the conditioned M1, while inhibiting MEPs from the contralateral M1 for 30 min. By contrast, cTBS1200 inhibited MEPs from the conditioned M1. Importantly, empirical mode decomposition-based MEG analysis showed that the amplitude of post-movement beta synchronisation (16–26 Hz) was significantly increased by iTBS1200 at the conditioned M1, but was suppressed at the nonconditioned M1. Alpha (8–13 Hz) and low gamma-ranged (35–45 Hz) rhythms were not notably affected. Movement kinetics remained consistent throughout.

Conclusions

TBS1200 modulated corticospinal excitability in parallel with the direction of conventional paradigms with modestly prolonged efficacy. Moreover, iTBS1200 increased post-movement beta synchronisation of the stimulated M1, and decreased that of the contralateral M1, probably through interhemispheric interaction.

Significance

Our results provide insight into the underlying mechanism of TBS and reinforce the connection between movement-related beta synchronisation and corticospinal output.     

Effect of afferent input on motor cortex excitability during stroke recovery

Objective

Afferent input is proposed to mediate its effect on motor functions by modulating the excitability of the motor cortex. We aimed to clarify – in a longitudinal study – how afferent input affects motor cortex excitability after stroke and how it is associated with recovery of hand function.

Methods

The motor cortex excitability was studied by measuring the reactivity of the motor cortex beta rhythm to somatosensory stimulation. We recorded the amplitude of the suppression and subsequent rebound of the beta oscillations during tactile finger stimulation with MEG in 23 first-ever stroke patients within one week and at 1 and 3 months after stroke, with concomitant evaluation of hand function.

Results

The strength of the beta rhythm rebound, suggested to reflect decreased motor cortex excitability, was weak in the affected hemisphere after stroke and it was subsequently increased during recovery. The rebound strength correlated with hand function tests in all recordings.

Conclusion

Motor cortex excitability is modulated by afferent input after stroke. The motor cortex excitability is increased in the AH acutely after stroke and decreases in parallel with recovery of hand function.

Significance

The results implicate the importance of parallel recovery of both sensory and motor systems in functional recovery after stroke.