Article

Ongoing physiological processes in the cerebral cortex.

Section on Cognitive Neurophysiology and Imaging, Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, 49 Convent Dr. 1E-21, MSC 4400, Bethesda, MD 20892, USA.
NeuroImage (Impact Factor: 6.25). 10/2011; 62(4):2190-200. DOI: 10.1016/j.neuroimage.2011.10.059
Source: PubMed

ABSTRACT Functional magnetic resonance imaging (fMRI) has revealed that the human brain undergoes prominent, regional hemodynamic fluctuations when a subject is at rest. These ongoing fluctuations exhibit distinct patterns of spatiotemporal synchronization that have been dubbed "resting state functional connectivity", and which currently serve as a principal tool to investigate neural networks in the normal and pathological human brain. Despite the wide application of this approach in human neuroscience, the neural mechanisms that give rise to spontaneous fMRI correlations are largely unknown. Here we review results of recent electrophysiological studies in the cerebral cortex of humans and nonhuman primates that link neural activity to ongoing fMRI fluctuations. We begin by describing results obtained with simultaneous fMRI and electrophysiological measurements that allow for the identification of direct neural correlates of resting state functional connectivity. We next highlight experiments that investigate the correlational structure of spontaneous neural signals, including the spatial variation of signal coherence over the cortical surface, across cortical laminae, and between the two hemispheres. In the final section we speculate on the origins and potential consequences of ongoing signals for normal brain function, and point out inherent limitations of the fMRI correlation approach.

0 Bookmarks
 · 
58 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recent findings in a range of scientific disciplines are challenging the conventional wisdom regarding the etiology, classification, and treatment of psychiatric disorders. This Review focuses on the current state of the psychiatric diagnostic nosology and recent progress in three areas: genomics, neuroimaging, and therapeutics development. The accelerating pace of novel and unexpected findings is transforming the understanding of mental illness and represents a hopeful sign that the approaches and models that have sustained the field for the past 40 years are yielding to a flood of new data and presaging the emergence of a new and more powerful scientific paradigm.
    Cell 03/2014; 157(1):201-214. · 31.96 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Primate occipitotemporal cortex (OTC) is composed of a mosaic of highly specialized brain regions each involved in the high-level visual analysis and recognition of particular stimulus categories (e.g., objects, faces, scenes, bodies, tools, etc.). Whereas theories attempting to account for this modular organization of category-selective responses in OTC have largely focused on visually driven, bottom-up inputs to OTC (e.g., dimensions related to the visual structure of the world and how it is experienced), other proposals have instead focused on the connectivity of OTC's outputs, emphasizing how the information processed by different OTC regions might be used by the rest of the brain. The latter proposals underscore the importance of interpreting the activity (and selectivity) of individual OTC areas within the greater context of the widely distributed network of areas in which they are embedded and that use OTC information to support behavior. Here, using resting-state fMRI, we investigated the functional connectivity (FC) patterns of OTC regions associated with object-, face-, scene-, body- and tool- related processing defined from task-based localizers acquired in the same cohort of participants. We observed notable differences in the whole-brain FC patterns, not only across OTC regions, but even between areas thought to form part of the same category-selective network. Furthermore, we found that the neuroanatomical location of OTC regions (e.g., adjacency) had little, if any, bearing on the FC networks observed. FC between certain OTC areas and other regions traditionally implicated in sensory-, motor-, affective- and/or cognitive-related processing and the associated theoretical implications are discussed.
    NeuroImage 03/2014; · 6.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although the emerging field of functional connectomics relies increasingly on the analysis of spontaneous fMRI signal covariation to infer the spatial fingerprint of the brain's large-scale functional networks, the nature of the underlying neuro-electrical activity remains incompletely understood. In part, this lack in understanding owes to the invasiveness of electrophysiological acquisition, the difficulty in their simultaneous recording over large cortical areas, and the absence of fully established methods for unbiased extraction of network information from these data. Here, we demonstrate a novel, data-driven approach to analyze spontaneous signal variations in electrocorticographic (ECoG) recordings from nearly entire hemispheres of macaque monkeys. Based on both broadband analysis and analysis of specific frequency bands, the ECoG signals were found to co-vary in patterns that resembled the fMRI networks reported in previous studies. The extracted patterns were robust against changes in consciousness associated with sleep and anesthesia, despite profound changes in intrinsic characteristics of the raw signals, including their spectral signatures. These results suggest that the spatial organization of large-scale brain networks results from neural activity with a broadband spectral feature and is a core aspect of the brain's physiology that does not depend on the state of consciousness.
    Cerebral Cortex 05/2014; · 6.83 Impact Factor

Alexander Maier