Current Source Density Estimates Research Articles

Object-Based Attentional Modulation of Biological Motion Processing: Spatiotemporal Dynamics Using Functional Magnetic Resonance Imaging and Electroencephalography

Although it is well documented that the ability to perceive biological motion is mediated by the lateral temporal cortex, whether and when neural activity in this brain region is modulated by attention is unknown. In particular, it is unclear whether the processing of biological motion requires attention or whether such stimuli are processed preattentively. Here, we used functional magnetic resonance imaging, high-density electroencephalography, and cortically constrained source estimation methods to investigate the spatiotemporal effects of attention on the processing of biological motion. Directing attention to tool motion in overlapping movies of biological motion and tool motion suppressed the blood oxygenation level-dependent (BOLD) response of the right superior temporal sulcus (STS)/middle temporal gyrus (MTG), while directing attention to biological motion suppressed the BOLD response of the left inferior temporal sulcus (ITS)/MTG. Similarly, category-based modulation of the cortical current source density estimates from the right STS/MTG and left ITS was observed beginning at approximately 450 ms following stimulus onset. Our results indicate that the cortical processing of biological motion is strongly modulated by attention. These findings argue against preattentive processing of biological motion in the presence of stimuli that compete for attention. Our findings also suggest that the attention-based segregation of motion category-specific responses only emerges relatively late (several hundred milliseconds) in processing.

Current source density (CSD) old/new effects during recognition memory for words and faces in schizophrenia and in healthy adults

We previously reported a preserved ‘old–new effect’ (enhanced parietal positivity 300–800 ms following correctly-recognized repeated words) in schizophrenia over mid-parietal sites using 31-channel nose-referenced event-related potentials (ERP) and reference-free current source densities (CSD). However, patients showed poorer word recognition memory and reduced left lateral–parietal P3 sources. The present study investigated whether these abnormalities are specific to words. High-density ERPs (67 channels) were recorded from 57 schizophrenic (24 females) and 44 healthy (26 females) right-handed adults during parallel visual continuous recognition memory tasks using common words or unknown faces. To identify and measure neuronal generator patterns underlying ERPs, unrestricted Varimax-PCA was performed using CSD estimates (spherical spline surface Laplacian). Two late source factors peaking at 442 ms (lateral parietal maximum) and 723 ms (centroparietal maximum) accounted for most of the variance between 250 and 850 ms. Poorer (76.6 ± 20.0% vs. 85.7 ± 12.4% correct) and slower (824 ± 170 vs. 755 ± 147 ms) performance in patients was accompanied by reduced stimulus-locked parietal sources. However, both controls and patients showed mid-frontal (442 ms) and left parietal (723 ms) old/new effects in both tasks. Whereas mid-frontal old/new effects were comparable across groups and tasks, later left parietal old/new effects were markedly reduced in patients over lateral temporoparietal but not mid-parietal sites, particularly for words, implicating impaired phonological processing. In agreement with prior results, ERP correlates of recognition memory deficits in schizophrenia suggest functional impairments of lateral posterior cortex (stimulus representation) associated with conscious recollection. This deficit was more pronounced for common words despite a greater difficulty to recall unknown faces, indicating that it is not due to a generalized cognitive deficit in schizophrenia.

A new method for current source density estimation from local field potentials and optical imaging data

Event Abstract Back to Event A new method for current source density estimation from local field potentials and optical imaging data Csaba Korossy1*, Sandor Borbely2, Zoltan Somogyvari1, Ildiko Vilagi2 and Peter Erdi1, 3 1 Department of Biophysics, KFKI Research Institute for Particle and Nuclear Physics , Hungary 2 Department of Physiology and Neurobiology, Eotvos Lorand University, Hungary 3 Center for Complex Systems Studies, Kalamazoo College, United States A new method for CSD estimation from LFP is presented. It is based on the Loreta method used in EEG/MEG imaging. Information about the confined spatial extent of cortical activity is also incorporated from optical imaging data. The new method is compared with the standard CSD method, and two recently reported inverse methods, the delta-source, and spline iCSD methods. Best results are given by the spline and Loreta methods, however, spline iCSD method gives significant errors when the activity on the brink of the cortex is high. Loreta gives excellent estimations even in these cases. Application of the new method on experimental data is also presented. Conference: 12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009. Presentation Type: Poster Presentation Topic: Research on the cerebral cortex and related structures Citation: Korossy C, Borbely S, Somogyvari Z, Vilagi I and Erdi P (2009). A new method for current source density estimation from local field potentials and optical imaging data. Front. Syst. Neurosci. Conference Abstract: 12th Meeting of the Hungarian Neuroscience Society. doi: 10.3389/conf.neuro.01.2009.04.207 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 06 Mar 2009; Published Online: 06 Mar 2009. * Correspondence: Csaba Korossy, Department of Biophysics, KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary, csabakorossy@yahoo.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Csaba Korossy Sandor Borbely Zoltan Somogyvari Ildiko Vilagi Peter Erdi Google Csaba Korossy Sandor Borbely Zoltan Somogyvari Ildiko Vilagi Peter Erdi Google Scholar Csaba Korossy Sandor Borbely Zoltan Somogyvari Ildiko Vilagi Peter Erdi PubMed Csaba Korossy Sandor Borbely Zoltan Somogyvari Ildiko Vilagi Peter Erdi Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Current-source density estimation based on inversion of electrostatic forward solution: Effects of finite extent of neuronal activity and conductivity discontinuities

A new method for estimation of current-source density (CSD) from local field potentials is presented. This inverse CSD (iCSD) method is based on explicit inversion of the electrostatic forward solution and can be applied to data from multielectrode arrays with various geometries. Here, the method is applied to linear-array (laminar) electrode data. Three iCSD methods are considered: the CSD is assumed to have cylindrical symmetry and be (i) localized in infinitely thin discs, (ii) step-wise constant or (iii) continuous and smoothly varying (using cubic splines) in the vertical direction. For spatially confined CSD distributions the standard CSD method, involving a discrete double derivative, is seen in model calculations to give significant estimation errors when the lateral source dimension is comparable to the size of a cortical column (less than ∼ 1 mm). Further, discontinuities in the extracellular conductivity are seen to potentially give sizable errors for even wider source distributions. The iCSD methods are seen to give excellent estimates when the correct lateral source dimension and spatial distribution of conductivity are incorporated. To illustrate the application to real data, iCSD estimates of stimulus-evoked responses measured with laminar electrodes in the rat somatosensory (barrel) cortex are compared to estimates from the standard CSD method.

Neurophysiological distinction of verb categories.

Neurophysiological brain responses to subcategories of action verbs were recorded using high resolution EEG. Starting 240 ms after word onset, topographies of event-related potentials distinguished between verbs referring to different action types. Current source density estimates revealed that verbs referring to actions executed with the legs (to kick) produced an activity focus close to the vertex, above motor areas involved in the programming of leg movements, whereas face-related verbs (to speak) produced a focus at left-lateral recordings, above perisylvian areas and the cortical representation of the face and articulators. This is evidence that brain mechanisms involved in word processing can differ even between fine-grained lexico-semantic subcategories and already within the first quarter of a second after word onset. We offer an explanation of the data in neurobiological terms.

Current source density estimation and interpolation based on the spherical harmonic Fourier expansion.

A method for the spatial analysis of EEG and EP data, based on the spherical harmonic Fourier expansion (SHE) of scalp potential measurements, is described. This model provides efficient and accurate formulas for: (1) the computation of the surface Laplacian and (2) the interpolation of electrical potentials, current source densities, test statistics and other derived variables. Physiologically based simulation experiments show that the SHE method gives better estimates of the surface Laplacian than the commonly used finite difference method. Cross-validation studies for the objective comparison of different interpolation methods demonstrate the superiority of the SHE over the commonly used methods based on the weighted (inverse distance) average of the nearest three and four neighbor values.

The dendritic origins of penicillin-induced epileptogenesis in CA3 hippocampal pyramidal cells.

Experiments were performed in order to identify the sites of epileptiform burst generation in rat hippocampal CA3 pyramidal cells. A subsequent slow field potential was studied, which is associated with afterdischarge generation. Laminar field potential and current source-density (CSD) methods were employed in hippocampal slices exposed to penicillin. Simultaneous intracellular and extracellular field recordings from the CA3 pyramidal cell body layer showed that whenever an epileptiform burst was recorded extracellularly, individual CA3 neurons underwent an intense depolarization shift. In extracellular records a slow negative field potential invariably followed epileptiform burst generation. In approximately 10% of slices, synchronous afterdischarges rode on the envelope of this negative field potential. Intracellularly a depolarizing afterpotential followed the depolarization shift and was coincident with the extracellular slow negative field potential. A one-dimensional CSD analysis performed perpendicular to the CA3 cell body layer showed that during epileptiform burst generation large current sinks occur simultaneously in the central portions of both the apical and basilar dendrites. The average distance of the peak amplitude for these sinks from the center of the cell body layer was 175 +/- 46.8 microns and 158 +/- 25.0 microns, respectively. A large current source was recorded in the cell body layer. Smaller current sources were observed in the distal portions of the dendritic layers. During the postburst slow field potential a current sink was recorded at the edge of the cell body layer in stratum oriens--a region referred to as the infrapyramidal zone. Simultaneous with the current sink recorded there, smaller sinks were often observed in the dendritic layers that appeared to be "tails" or prolongations of the currents underlying burst generation. Two-dimensional analyses of these field potentials were performed on planes parallel and perpendicular to the exposed surface of the slice. Isopotential contours showed that the direction of extracellular current is mainly orthogonal to the CA3 laminae. Correction of CSD estimates made perpendicular to the cell body layer for current flowing in the other direction did not alter the location of computed current sources and sinks. In order to show that the dendritic currents associated with epileptiform burst generation were active sinks, tetrodotoxin (TTX) was applied locally to the dendrites where the current sinks were recorded.(ABSTRACT TRUNCATED AT 400 WORDS)