LINEAR-SYSTEMS ANALYSIS OF FUNCTIONAL MAGNETIC-RESONANCE-IMAGING IN HUMAN V1

The linear transform model of functional magnetic resonance imaging (f MRI) hypothesizes that fMRI responses are proportional to local averag e neural activity averaged over a period of time, This work reports re sults from three empirical tests that support this hypothesis. First, fMRI responses in human primary visual cortex (V1) depend separably on stimulus timing and stimulus contrast, Second, responses to long-dura tion stimuli can be predicted from responses to shorter duration stimu li, Third, the noise in the fMRI data is independent of stimulus contr ast and temporal period, Although these tests can not prove the correc tness of the linear transform model, they might have been used to reje ct the model. Because the linear transform model is consistent with ou r data, we proceeded to estimate the temporal fMRI impulse-response fu nction and the underlying (presumably neural) contrast-response functi on of human V1.