Scalp Current Density Mapping Research Articles

Scalp Current Density Mapping in the Analysis of Mismatch Negativity Paradigms

MMN oddball paradigms are frequently used to assess auditory (dys)functions in clinical populations, or the influence of various factors (such as drugs and alcohol) on auditory processing. A widely used procedure is to compare the MMN responses between two groups of subjects (e.g. patients vs controls), or between experimental conditions in the same group. To correctly interpret these comparisons, it is important to take into account the multiple brain generators that produce the MMN response. To disentangle the different components of the MMN, we describe the advantages of scalp current density (SCD)-or surface Laplacian-computation for ERP analysis. We provide a short conceptual and mathematical description of SCDs, describe their properties, and illustrate with examples from published studies how they can benefit MMN analysis. We conclude with practical tips on how to correctly use and interpret SCDs in this context.

From upright to upside-down presentation: a spatio-temporal ERP study of the parametric effect of rotation on face and house processing.

BackgroundWhile there is a general agreement that picture-plane inversion is more detrimental to face processing than to other seemingly complex visual objects, the origin of this effect is still largely debatable. Here, we address the question of whether face inversion reflects a quantitative or a qualitative change in processing mode by investigating the pattern of event-related potential (ERP) response changes with picture plane rotation of face and house pictures. Thorough analyses of topographical (Scalp Current Density maps, SCD) and dipole source modeling were also conducted.ResultsWe find that whilst stimulus orientation affected in a similar fashion participants' response latencies to make face and house decisions, only the ERPs in the N170 latency range were modulated by picture plane rotation of faces. The pattern of N170 amplitude and latency enhancement to misrotated faces displayed a curvilinear shape with an almost linear increase for rotations from 0° to 90° and a dip at 112.5° up to 180° rotations. A similar discontinuity function was also described for SCD occipito-temporal and temporal current foci with no topographic distribution changes, suggesting that upright and misrotated faces activated similar brain sources. This was confirmed by dipole source analyses showing the involvement of bilateral sources in the fusiform and middle occipital gyri, the activity of which was differentially affected by face rotation.ConclusionOur N170 findings provide support for both the quantitative and qualitative accounts for face rotation effects. Although the qualitative explanation predicted the curvilinear shape of N170 modulations by face misrotations, topographical and source modeling findings suggest that the same brain regions, and thus the same mechanisms, are probably at work when processing upright and rotated faces. Taken collectively, our results indicate that the same processing mechanisms may be involved across the whole range of face orientations, but would operate in a non-linear fashion. Finally, the response tuning of the N170 to rotated faces extends previous reports and further demonstrates that face inversion affects perceptual analyses of faces, which is reflected within the time range of the N170 component.

Specific temporal response to human voice in young children

Event Abstract Back to Event Specific temporal response to human voice in young children Ophélie Rogier1*, S. Roux1, C. Barthélémy2 and N. Bruneau1 1 INSERM U930, Université François-Rabelais de Tours, France 2 Hôpital Bretonneau, Service de Pédopsychiatrie, France Voice is one of the most important social stimuli. Functional magnetic resonance imaging (fMRI) studies in adults have localized voice processing along the upper bank of the superior temporal sulcus (STS), particularly on the right side (review in Belin et al., Trends in Cognitive Sciences, 2004). These cerebral regions, also called temporal voice areas (TVA), mature early since neonates clearly discriminate this particular auditory stimulus, as demonstrated using behavioural methods (DeCasper and Fifer, Science, 1980). The aim of the present study was to evidence electrophysiological correlates of voice processing in children. Twelve 6-7-year-old children participated in this study. Cortical auditory evoked potentials (AEPs) were recorded during passive listening to human vocal sounds (foreign words, laughs, sighs, coughs…) and environmental sounds (alarms, cars, musical instruments, streams…). Stimuli were derived from those used in Belin et al.’s studies, additionally segmented in 500-ms samples in order to accommodate AEP methodology. While cortical AEPs to both vocal and non-vocal stimuli displayed similar successive P1 and N250 waveforms at fronto-central sites (Fz, Cz), temporal responses showed clear differences according to stimulus, specially on the right side. A negative N1c wave culminating at around 160 ms was evoked by environmental sounds on both left and right temporal sites. Such N1c waves were not recorded in response to voice stimuli, which evoked a large positive deflection on the right side in the 100-250 ms latency range. Scalp current density mapping showed that a radially-oriented source underlay this positivity. We might hypothesize that this generator is localized in the superior temporal sulcus, previously demonstrated to be specifically activated by voice in fMRI studies. This temporal response to voice appears a reliable marker for further investigation of voice perception abilities in children with communication disorders. Conference: 10th International Conference on Cognitive Neuroscience, Bodrum, Turkey, 1 Sep - 5 Sep, 2008. Presentation Type: Poster Presentation Topic: Perceptual Processing and Recognition Citation: Rogier O, Roux S, Barthélémy C and Bruneau N (2008). Specific temporal response to human voice in young children. Conference Abstract: 10th International Conference on Cognitive Neuroscience. doi: 10.3389/conf.neuro.09.2009.01.322 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: 10 Dec 2008; Published Online: 10 Dec 2008. * Correspondence: Ophélie Rogier, INSERM U930, Université François-Rabelais de Tours, Tours, France, o.rogier@chu-tours.fr 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 Ophélie Rogier S. Roux C. Barthélémy N. Bruneau Google Ophélie Rogier S. Roux C. Barthélémy N. Bruneau Google Scholar Ophélie Rogier S. Roux C. Barthélémy N. Bruneau PubMed Ophélie Rogier S. Roux C. Barthélémy N. Bruneau 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.

Left temporal impairment of auditory information processing in prematurely born 9-year-old children: An electrophysiological study

Children born preterm more than average display cognitive difficulties that are significant enough to prevent normal schooling. The aim of our study was to provide better understanding of the long-term neuropathological processes associated with preterm injury, through the hypothesis that mild cognitive disorders might be related to slight deficits in primary functions such as attention and perception. Assessment of auditory pre-attentive processes was performed by recording the obligatory sensory response (N250) and the change-detection response (Mismatch Negativity, MMN). Topographic study of these responses was performed in fifteen 9-year-old children born preterm (27–33 weeks gestational age) matched to fifteen control children born at term. The auditory stimulus sequence consisted of 1000 Hz standard and 1100 Hz deviant tones (15%) delivered binaurally with an interstimulus interval of 700 ms. The results showed that MMN was similar in both groups. Analysis of the responses to standard repetitive tones demonstrated significantly smaller N250 wave amplitude in children born preterm. Scalp current density maps showed that this reduction in amplitude was associated with lower activity of both frontal and left supratemporal generators. Although the functional significance of the N250 wave in children remains to be clarified, our results indicate a disorder of auditory processes related to prematurity that might have consequences on the development of higher-level processes.

Hypersensitivity to acoustic change in children with autism: Electrophysiological evidence of left frontal cortex dysfunctioning

Exaggerated reactions to even small changes in the environment and abnormal behaviors in response to auditory stimuli are frequently observed in children with autism (CWA). Brain mechanisms involved in the automatic detection of auditory frequency change were studied using scalp potential and scalp current density (SCD) mapping of mismatch negativity (MMN) in 15 CWA matched with 15 healthy children. Compared with the response in controls, MMN recorded at the Fz site in CWA showed significantly shorter latency and was followed by a P3a wave. Mapping of potentials indicated significant intergroup differences. Moreover, SCD mapping demonstrated the dynamics of the different MMN generators: Although temporal component was evidenced bilaterally in both groups, it occurred earlier on the left hemisphere in CWA, preceded by an abnormal early left frontal component. The electrophysiological pattern reported here emphasized a left frontal cortex dysfunctioning that might also be implicated in cognitive and behavioral impairment characteristic, of this complex neurodevelopmental disorder.

Scalp current density mapping in presurgical evaluation of partial epilepsy

Scalp current density mapping in presurgical evaluation of partial epilepsy

Event-related brain potentials elicited by visual and auditory stimuli: Application of scalp current density mapping

This chapter describes the neuropharmacology of amyotrophic lateral sclerosis (ALS) as expressed on transmitter-related enzymes and receptors in the central nervous system (CNS) and skeletal muscle, with emphasis on cholinergic mechanisms. ALS and other degenerative disorders, such as Parkinson's disease and dementia of the Alzheimer type, are neuropathologically characterized by preferential vulnerability of some neuronal systems and relative resistance of other neuronal systems. Irrespective of the aetiology, the progressive neuronal degenerations should be accompanied by transmitter dysfunction at the synapses of the fiber tracts involved. Insight into such mechanisms might lead to the development of symptomatic pharmacological therapy. In ALS, the degenerative changes are restricted to the cortical spinal tracts and to the lower motor neurons in the brainstem and spinal cord, although the involvement of nonmotor pathways is increasingly recognized. The chapter also focuses on some closely allied therapeutic trials and the search for neurotrophic disturbances and neurotoxic factors in ALS. The different hypotheses concerning the aetiology of ALS are reflected by the large number of treatment strategies, which are discussed in the chapter.

Several attention-related wave forms in auditory areas: a topographic study

The purpose of this study was to progress in the understanding of the electrogenesis of attention-related wave forms in order to highlight some of the underlying attentional processes. ERPs were recorded from 16 electrodes, from 12 subjects who attended selectively to either high or low pitch tones delivered at a constant inter-stimulus interval of 800 msec to either right or left ear, while ignoring a concurrent sequence of tones of the other pitch delivered to the other ear. The attention-related wave forms were obtained by subtracting ERPs to unattended tones from ERPs to the same tones when they were attended. These wave forms were topographically displayed by both potential maps and scalp current density maps and compared with the corresponding maps of the N 1 component of the ERPs, to determine the similarity of their generators. It has been shown that the attention effect is expressed by at least two components in specific auditory areas, one of small amplitude, occurring during the ascending slope of the N 1 component, sensitive to the pitch of the attended stimulus, and possibly originating in the supratemporal plane of the auditory cortex; another of large amplitude, peaking symmetrically over both hemispheres and having a different topography from that of the N 1 component. As described by other authors, a third, later, component appears over frontal areas, but probably originates from deeper sources of the brain. Models of selective attention processes, particularly the ‘attentional trace’ concept, are discussed in the light of these results.

Scalp current density mapping: value and estimation from potential data.

Scalp current density (SCD) makes possible the identification of scalp sources and sinks of current. SCD is reference independent and its peaks and troughs are sharper than those of the scalp potential (SP). SCD, by comparison to SP, reflects mainly the activity of cortical generators. SCD mapping appears to be a valuable tool to spatially split smeared SP distribution due to simultaneously active generators. The SCD map may be computed from any sufficiently smooth mathematical SP map. An evaluation of the error of SCD estimation is given for a surface spline method of interpolation of SP. An example of the simultaneous use of SP and SCD in the analysis of somatosensory evoked data is given.