Abstract
Interpreting fMRI data relies on the assumption that hemodynamic responses reflect neuronal activity. Some recently reported results seem to suggest that this assumption might be less robust than what has been thought so far. Data by Schummers et al. (2008) suggest that hemodynamic responses depend on functional properties of astrocytes as mediators of neuronal activity to blood vessels, and therefore reflect neuronal tuning properties only indirectly. The question is how much the final outcome differs from a linear integration of the local neuronal responses.
Highlights
In more specific visual stimulus designs involving perceptual suppression of a physically present visual stimulus (Maier et al, 2008), BOLD responses and neuronal ones have been reported to not always go “hand in hand”, suggesting that the relationship between hemodynamic and neuronal responses might depend on stimulus characteristics and behavioral task
The authors failed to predict the recorded hemodynamic changes from local neuronal activity. Does this rule out the latter as cause for the former? Is it conceivable that complex, modulatory phenomena such as attention involve complex links between neuronal and vascular activity, other than those acting in the case of a salient visual stimulus? What is the relation between eye movements, hemodynamic responses and local neuronal activity? Answers to these questions may help to better understand the main observations in (Sirotin and Das, 2009) and its implications for functional brain imaging
A central assumption underlying the interpretation of fMRI data is that hemodynamic responses correspond to local neuronal activity and that they reflect its functional properties
Summary
In more specific visual stimulus designs involving perceptual suppression of a physically present visual stimulus (Maier et al, 2008), BOLD responses and neuronal ones have been reported to not always go “hand in hand”, suggesting that the relationship between hemodynamic and neuronal responses might depend on stimulus characteristics and behavioral task.
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