Neural connectivity as revealed by SEF wave shape: A morphological MEG study
نویسندگان
چکیده
The time varying spatial properties of the evoked cerebral response to external stimuli depicts the characteristics of the excited neural circuitry for the specific sensory involved modality. These spatiotemporal features are reflected in the shape of the brain evoked response, and our aim is to quantitatively characterize individually anatomofunctional features for the somatosensory system (somatosensory evoked fields = SEFs). Suitable tool could be magnetoencephalographic (MEG) signal, being not distorted by the extra-cerebral layers (i.e. the skull and meninges) separating neural currents from the recording apparatus: this allows the waveform of the evoked response to directly describe the spatio-temporal cerebral activation. The morphology of SEFs following median nerve stimulation has been described as two initial peaks of opposite polarity (M20, M30, around 20 and 30 ms from the stimulus onset, [1, 2, 3, 4]), followed by a third component between 50 and 100 ms from the stimulus onset. Despite this pattern, the shape of the response is quite variable from subject to subject. In fact, great inter-individual variability has been previously described recognizing three morphology categories for the latter component ([4], for our data, Fig1): in some subjects it has the same polarity as the preceding one (Fig. 1, S1, 61% of our cases), in others it shows the opposite (Fig. 1, S2, 29% of cases) or is even absent (Fig. 1, S3, 10% of cases). Combined with this inter-individual variability of SEF morphology, a great intra-subjective, interhemispheric similarity of SEF pattern is evident (Fig. 1). Moreover, SEF morphology is very stable when tested in successive independent sessions in the same subject. Our study attempts to define a parameter that describes intra-subject interhemispheric similarity, quantitatively evaluates it in a healthy population and calculates its normative limits. Figure 1: Superimposition of all recording channels in left/right parietal regions (respectively left/right columns) in the 100 ms post-stimulus period. SEFs of three paradigmatic subjects are presented, to show different SEF morphologies (compare S1, S2, S3 in one hemisphere) both in the time intervals before 45 ms and between 45 and 100 ms from the stimulus onset. By comparing SEF from left vs right hemisphere for each subject, the intra-subject interhemispheric shape similarity is appreciable. On the right side, their parameters values are reported (IHC_SI, IHC_par).
منابع مشابه
Prediction of seizure outcome following epilepsy surgery: Asymmetry of thalamic glucose metabolism and cerebral neural activity in temporal lobe epilepsy
OBJECTIVE The objective of this retrospective study is to analyze whether preoperative functional imaging studies using FDG-PET and MEG enable prediction of postoperative seizure outcomes. METHODS Thirty-six patients with intractable temporal lobe epilepsy were studied. Asymmetry index of tCMRgluc (PET-AI) and the equivalent current dipole intensity of first response of SEF (SEF-AI) were dete...
متن کاملCombined MEG and fMRI model
An integrated model for magnetoencephalography (MEG) and functional Magnetic Resonance Imaging (fMRI) is proposed. In the proposed model, MEG and fMRI outputs are related to the corresponding aspects of neural activities in a voxel. Post synaptic potentials (PSPs) and action potentials (APs) are two main signals generated by neural activities. In the model, both of MEG and fMRI are related to t...
متن کاملA wavelet-based method for measuring the oscillatory dynamics of resting-state functional connectivity in MEG
Determining the dynamics of functional connectivity is critical for understanding the brain. Recent functional magnetic resonance imaging (fMRI) studies demonstrate that measuring correlations between brain regions in resting-state activity can be used to reveal intrinsic neural networks. To study the oscillatory dynamics that underlie intrinsic functional connectivity between regions requires ...
متن کاملTask- and stimulus-related cortical networks in language production: Exploring similarity of MEG- and fMRI-derived functional connectivity
Large-scale networks support the dynamic integration of information across multiple functionally specialized brain regions. Network analyses of haemodynamic modulations have revealed such functional brain networks that show high consistency across subjects and different cognitive states. However, the relationship between the slowly fluctuating haemodynamic responses and the underlying neural me...
متن کاملNEURAL NETWORK PREDICTION OF THE EFFECT OF SEMISOLID METAL (SSM) PROCESSING PARAMETERS ON PARTICLE SIZE AND SHAPE FACTOR OF PRIMARY α-Al ALUMINUM ALLOY A356.0.
Abstract: Problems such as the difficulty of the selection of processing parameters and the large quantity of experimental work exist in the morphological evolutions of Semisolid Metal (SSM) processing. In order to deal with these existing problems, and to identify the effect of the processing parameters, (i.e. shearing rate-time-temperature) combinations on particle size and shape factor, ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2001