Article

Head models and dynamic causal modeling of subcortical activity using magnetoencephalographic/electroencephalographic data.

Université Pierre et Marie Curie-Paris 6, Centre de Recherche de l’institut du Cerveau et de la Moelle épinière, UMR-S975, 75651 Paris, France.
Reviews in the neurosciences (Impact Factor: 3.26). 01/2012; 23(1):85-95. DOI: 10.1515/rns.2011.056
Source: PubMed

ABSTRACT Cognitive functions involve not only cortical but also subcortical structures. Subcortical sources, however, contribute very little to magnetoencephalographic (MEG) and electroencephalographic (EEG) signals because they are far from external sensors and their neural architectonic organization often makes them electromagnetically silent. Estimating the activity of deep sources from MEG and EEG (M/EEG) data is thus a challenging issue. Here, we review the influence of geometric parameters (location/orientation) on M/EEG signals produced by the main deep brain structures (amygdalo-hippocampal complex, thalamus and some basal ganglia). We then discuss several methods that have been utilized to solve the issues and localize or quantify the M/EEG contribution from deep neural currents. These methods rely on realistic forward models of subcortical regions or on introducing strong dynamical priors on inverse solutions that are based on biologically plausible neural models, such as those used in dynamic causal modeling (DCM) for M/EEG.

1 Bookmark
 · 
155 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Loudness dependence of auditory evoked potentials (LDAEP) evaluates loudness processing in the human auditory system and is often altered in patients with psychiatric disorders. Previous research has suggested that this measure may be used as an indicator of the central serotonergic system through the highly serotonergic innervation of the auditory cortex. However, differences among the commonly used analysis approaches (such as source analysis and single electrode estimation) may lead to different results. Putatively due to discrepancies of the underlying structures being measured. Therefore, it is important to learn more about how and where exactly loudness variation is processed. We conducted a detailed investigation of the LDAEP generators and their temporal dynamics by means of multichannel magnetoencephalography (MEG). Evoked responses to brief tones of five different intensities were recorded from 19 healthy participants. We used magnetic field tomography in order to appropriately localize superficial as well as deep source generators of which we conducted a time series analysis. The results showed that apart from the auditory cortex other cortical sources exhibited activation during the N1/P2 time window. Analysis of time courses in the regions of interest revealed a sequential cortical activation from primary sensory areas, particularly the auditory and somatosensory cortex to posterior cingulate cortex (PCC) and to premotor cortex (PMC). The additional activation within the PCC and PMC has implications on the analysis approaches used in LDAEP research.
    NeuroImage 08/2014; · 6.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Human faces may signal relevant information and are therefore analysed rapidly and effectively by the brain. However, the precise mechanisms and pathways involved in rapid face processing are unclear. One view posits a role for a subcortical connection between early visual sensory regions and the amygdala, while an alternative account emphasises cortical mediation. To adjudicate between these functional architectures, we recorded magnetoencephalographic (MEG) evoked fields in human subjects to presentation of faces with varying emotional valence. Early brain activity was better explained by dynamic causal models containing a direct subcortical connection to the amygdala irrespective of emotional modulation. At longer latencies, models without a subcortical connection had comparable evidence. Hence, our results support the hypothesis that a subcortical pathway to the amygdala plays a role in rapid sensory processing of faces, in particular during early stimulus processing. This finding contributes to an understanding of the amygdala as a behavioural relevance detector.
    NeuroImage 08/2014; · 6.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Assessment of event-related desynchronization (ERD) may assist in predicting recovery from stroke and rehabilitation, for instance in BCI applications. Here, we explore the temporal evolution of ERD during stroke recovery. Ten stroke patients and eleven healthy controls were recruited to participate in a hand movement task while EEG was being recorded. Four measurements were conducted in eight patients within four months. We quantified changes of ERD using a modulation strength measure, Sm, which represents an area and amplitude of ERD. 7/8 patients showed good recovery. Absence-or-reduction of ipsilesional modulation was initially found in stroke patients but not in the healthy controls. In the patient group, two evolutions were found in 6/8 patients: a significant increase in ipsilesional Sm; and a decreasing trend in contralesional Sm. In the only non-recovery patient, absence of ipsilesional modulation was observed, while his contralesional Sm increased with time after stroke. The two evolutions presumably reflect the reorganization of brain networks and functional recovery after acute stroke. The significant increase of ipsilesional Sm in patients with a good recovery suggests an important role of this hemisphere during recovery. Improved understanding of ERD in acute stroke may assist in prognostication and rehabilitation.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 11/2013; · 3.12 Impact Factor

Full-text

Download
53 Downloads
Available from
May 30, 2014