What we can do and what we cannot do with fMRI

Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany, and Imaging Science and Biomedical Engineering, University of Manchester, Manchester M13 9PL, UK.
Nature (Impact Factor: 42.35). 06/2008; 453(7197):869-878. DOI: 10.1038/nature06976
Source: PubMed

ABSTRACT Functional magnetic resonance imaging (fMRI) is currently the mainstay of neuroimaging in cognitive neuroscience. Advances in scanner technology, image acquisition protocols, experimental design, and analysis methods promise to push forward fMRI from mere cartography to the true study of brain organization. However, fundamental questions concerning the interpretation of fMRI data abound, as the conclusions drawn often ignore the actual limitations of the methodology. Here I give an overview of the current state of fMRI, and draw on neuroimaging and physiological data to present the current understanding of the haemodynamic signals and the constraints they impose on neuroimaging data interpretation.

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    • "However, so far, the association between increased demands on dual-task coordination and increased activation of lPFC, as seen on fMRI, remains correlative. This correlative relationship is a result of the basic nature of the fMRI method, reflecting neuronal mass activity with its implications for drawing judicious conclusions that are most frequently ignored (Logothetis, 2008). For instance, rather than showing simple feed-forward integration of cortical input in the lPFC, fMRI signals cannot unambiguously reflect the underlying functional role since these signals are typically a combination of neural mechanisms, such as a local connectivity with strong excitatory and inhibitory recurrence (Douglas and Martin, 2004). "
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    ABSTRACT: Executive processing in dual tasks is primarily associated with activation of the lateral prefrontal cortex (lPFC), which is demonstrated in functional imaging studies (e.g., Szameitat et al., 2006). However, a causal relation between lPFC activity and executive functions in dual tasks has not been demonstrated so far. Here, we used anodal transcranial direct current stimulation (atDCS [1 mA, 20 min] vs. sham stimulation [1 mA, 30 s]) over the left inferior frontal junction under conditions of random and fixed task order in dual tasks as well as in single tasks in healthy young individuals (Experiment 1). We found that atDCS, if administered simultaneously to the task, improved performance in random-order dual tasks, but not in fixed-order dual tasks and single tasks. Moreover, dual-task performance under random-order conditions did not improve if atDCS was applied prior to the task performance. The identical procedure in Experiment 2 showed no difference in dual-task performance under random-task order conditions when we compared cathodal tDCS (ctDCS) with sham stimulation. Our findings suggest that dual-task performance is causally related to lPFC activation under conditions that require task-order decisions and high demands on executive functioning. Subsequent studies may now explore if atDCS leads to sustained improvements parallel to the training of dual tasks.
    Neuropsychologia 01/2015; 68:8-20. DOI:10.1016/j.neuropsychologia.2014.12.024 · 3.45 Impact Factor
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    • "Most of the contributors to the Special Research Topic used noninvasive techniques, such as fMRI, to trace associations between emotion and cognition, on the one hand, and brain function on the other. Aside from unresolved questions about the origins and significance of the measured signals (e.g., Logothetis, 2008), the most important limitation of these techniques is that they do not address causation. A crucial challenge for future studies is to develop a mechanistic understanding of the distributed networks that support the interplay of emotion and cognition. "
    Frontiers in Human Neuroscience 01/2015; 9. DOI:10.3389/fnhum.2015.00058 · 2.90 Impact Factor
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    • "In neurosciences, imaging plays a central role providing information about brain structure and function. In particular, magnetic resonance imaging (MRI) generates anatomical and functional information on the healthy or diseased brain and is a cornerstone of cognitive neuroscience (Logothetis 2008; Raichle 2009). "
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    ABSTRACT: Advances in neuroscience are underpinned by large, multicenter studies and a mass of heterogeneous datasets. When investigating the relationships between brain anatomy and brain functions under normal and pathological conditions, measurements obtained from a broad range of brain imaging techniques are correlated with the information on each subject’s neurologic states, cognitive assessments and behavioral scores derived from questionnaires and tests. The development of ontologies in neuroscience appears to be a valuable way of gathering and handling properly these heterogeneous data – particularly through the use of federated architectures. We recently proposed a multilayer ontology for sharing brain images and regions of interest in neuroimaging. Here, we report on an extension of this ontology to the representation of instruments used to assess brain and cognitive functions and behavior in humans. This extension consists of a ‘core’ ontology that accounts for the properties shared by all instruments supplemented by ‘domain’ ontologies that conceptualize standard instruments. We also specify how this core ontology has been refined to build domain ontologies dedicated to widely used instruments and how various scores used in the neurosciences are represented. Lastly, we discuss our design choices, the ontology’s limitations and planned extensions aimed at querying and reasoning across distributed data sources.
    Neuroinformatics 01/2015; Volume 13(Issue 1):93-110. DOI:10.1007/s12021-014-9244-3 · 3.10 Impact Factor
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