The hemodynamic inverse problem: Making inferences about neural activity from measured MRI signalsписьмо
Аннотация: Cognitive events rely on rapid information flow among interdependent brain areas. Estimates from single-unit physiology in monkeys and human electrophysiological scalp recordings suggest communication between brain areas takes place on the order of tens to hundreds of milliseconds (1). A challenge to the study of human cognition has been to develop noninvasive methods to measure the temporal orchestration of information processing. Limitations were initially imposed by the imaging devices themselves. Positron emission tomography (PET) methods based on short-lived isotopes, for example, take about a minute to make a measurement (2). The advent of functional MRI (fMRI) changed the landscape of human brain imaging by providing a tool that can make measurements on the sub-second time scale (3, 4). However, the use of fMRI solves only part of the problem. An even greater challenge surrounds the temporal sluggishness of the correlates of neuronal activity to which modern imaging devices are sensitive. Most fMRI studies measure brain activity indirectly through changes in blood vasculature that accompany neuronal activity. Although the exact origins of these vascular changes are debated (5, 6), they are temporally slow, begin seconds after a neuronal event, and last for tens of seconds (7). For isolated cognitive acts, which can often be completed in under a second, the sluggish nature of the measured response means that a signal is detected after the neuronal event has subsided. It is against this backdrop that the work of Bellgowan et al. in a recent issue of PNAS (8) can be appreciated. Their study uses a modeling approach to make inferences about neural activity timing differences of ≈100 milliseconds. To understand the basis of this surprisingly high temporal resolution, it is important to consider the evolution of fMRI.
Год издания: 2003
Авторы: Randy L. Buckner
Издательство: National Academy of Sciences
Источник: Proceedings of the National Academy of Sciences
Ключевые слова: Functional Brain Connectivity Studies, Advanced MRI Techniques and Applications, Neural dynamics and brain function
Другие ссылки: Proceedings of the National Academy of Sciences (HTML)
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PubMed Central (HTML)
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Открытый доступ: green
Том: 100
Выпуск: 5
Страницы: 2177–2179