sentences:  This work has revealed the mechanism for noninvasive brain imaging methods such as functional magnetic resonance imaging (fMRI).The Sur laboratory has also shown how neurons of the mature visual cortex alter their responses dynamically based on the configuration of visual stimuli in space and time.The laboratory studies the mechanisms by which visual neurons at the earliest stages of cortical processing are influenced not only by "bottom up" visual inputs but also in "top down" manner by mental state, including attention, arousal, and expectation.