Spatial and temporal limits in cognitive neuroimaging with fMRI

A large body of research in human perception and cognition has been concern ed with the segregation of mental events into their presumed hierarchical p rocessing stages, the temporal aspect of such processing being termed 'ment al chronometry'. Advances in single-event functional magnetic resonance ima ging (fMRI) have allowed the timing information between the onset of activi ty in different neural substrates as well as the duration of cognitive proc essing during a task, offering new opportunities in the study of human perc eption and cognition. Single-event fMRI studies have also facilitated incre ased spatial resolution in fMRI, allowing studies of columnar organization in humans. Important processes such as object recognition. binocular vision and other processes are thought to be organized at the columnar level; thu s, these advances in the spatial and temporal capabilities of fMRI allow a new of cognitive and basic neuroscience studies to be performed, investigat ing the temporal and spatial relationships between these cortical sub units . Such experiments bear a closer resemblance to single-unit or evoked-poten tial studies than to classical static brain activation maps and might serve as a bridge between primate electrophysiology and human studies. These adv ances are initially demonstrated only in simple visual and motor system tas ks and it is likely to be several years before the techniques we describe a re robust enough for general use.