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A recent nonlinear system by Friston et al. (2000. NeuroImage 12: 466-477) links the changes in BOLD response to changes in neural activity. The system consists of five subsystems, linking: (1) neural activity to flow changes; (2) flow changes to oxygen delivery to tissue; (3) flow changes to changes in blood volume and venous outflow; (4) changes in flow,(More)
An understanding of the relationship between changes in neural activity and the accompanying hemodynamic response is crucial for accurate interpretation of functional brain imaging data and in particular the blood oxygen level-dependent (BOLD) fMRI signal. Much physiological research investigating this topic uses anesthetized animal preparations, and yet,(More)
The relationship between neural activity and accompanying changes in cerebral blood flow (CBF) and oxygenation must be fully understood before data from brain imaging techniques can be correctly interpreted. Whether signals in fMRI reflect the neural input or output of an activated region is still unclear. Similarly, quantitative relationships between(More)
Unexpected, biologically salient stimuli elicit a short-latency, phasic response in midbrain dopaminergic (DA) neurons. Although this signal is important for reinforcement learning, the information it conveys to forebrain target structures remains uncertain. One way to decode the phasic DA signal would be to determine the perceptual properties of sensory(More)
The temporal relationship between changes in cerebral blood flow (CBF) and cerebral blood volume (CBV) is important in the biophysical modeling and interpretation of the hemodynamic response to activation, particularly in the context of magnetic resonance imaging and the blood oxygen level-dependent signal. measured the steady state relationship between(More)
The relationship between localized changes in brain activity and metabolism, and the blood oxygenation level-dependent (BOLD) signal used in functional magnetic resonance imaging studies is not fully understood. One source of complexity is that stimulus-elicited changes in the BOLD signal arise both from changes in oxygen consumption due to increases in(More)
This article investigates the relation between stimulus-evoked neural activity and cerebral hemodynamics. Specifically, the hypothesis is tested that hemodynamic responses can be modeled as a linear convolution of experimentally obtained measures of neural activity with a suitable hemodynamic impulse response function. To obtain a range of neural and(More)
An essential prerequisite for the accurate interpretation of noninvasive functional brain imaging techniques, such as blood oxygen level dependent (BOLD) fMRI, is a thorough understanding of the coupling relationship between neural activity and the haemodynamic response. The current study investigates this relationship using rat barrel cortex as a model.(More)
We describe a method for imaging the local cortical haemodynamic response to whisker stimulation in the rat without use of anaesthetic or paralytic agents. Female Hooded Lister rats were anaesthetised and a section of skull overlying somatosensory cortex thinned to translucency. A stainless steel chamber was then secured over the thin cranial window.(More)
Optical imaging spectroscopy was used to measure the hemodynamic response of somatosensory cortex to stimulation of the whiskers. Responses to brief puffs of air were compared in anesthetized and unanesthetized rats. The hemodynamic response was approximately four times larger in the unanesthetized animal than the corresponding anesthetized animal. In(More)