fMRI mpeg movies

Please feel free to use these movies in classes, lectures and talks.

Power point slides of cortical magnification
Obligatory spinning brain

It is apparently mandatory for all fMRI labs to have a movie like this. This brain is currently used by Ed Hubbard.

This movie illustrates the retinotopic mapping techniques used by most vision fMRI labs. The idea for the phase-encoded stimulus comes from Steve Engel (pdf), and was expanded upon by Marty Sereno and Anders Dale. I first saw a movie like this in a talk by Roger Tootell back in 1997. This is a movie of the fMRI response to a subject (Geoff Boynton) viewing a slowly expanding annulus containing a counterphase modulated (8Hz) flickering checkerboard. Each gray region represents a computationally flattened representation of the subject's left and right visual cortices, each with a radious of about 60mm. Visual areas are overlayed in color as V1 (red), v2 (green) and V3 (blue). The actual stimulus during scanning took 40 seconds to complete a full cycle, and six cycles were repeteated. The movie was made by calculating the amplitude and phase of the 6-cycle component of the Fourier transform of the temporal signal. The 'Active' region is the area of cortex that modulates at a particular temporal phase as phase is cycled through 360 degrees to make the movie. Note how the the activity spreads in a systematic manner as the stimulus moves from the fovea to the periphery.

This movie is the response to a wedge stimulus subtending 30 degrees of arc and containing flickering checkerboards. The wedge swept through 360 degrees every 40 seconds. Note how activity sweeps across V1 as the wedge sweeps from vertical to vertical meridian in the contralateral hemifield. Note also how V2 is divided into four regions, each representing 90 degrees of the visual field. The sweep of activity in V2 is in the opposite direction as V1. V3's organization is reversed again so that the activity sweeps in the same direction as V1.

This is a movie illustrating the effects of spatial attention on responses in early visual areas. Subjects were asked to alternate their attention to a sitmulus on either the left or right visual field and perform a speed discrimination task. Only the focus of attention varied, and not the visual stimulus or task difficulty. This movie shows the pattern of activation as a subject alternates attention from left to right, shown on a psuedo-coronal slice of the brain. The blue line denotes the location of primary visual cortex (V1). Note that activity modulates with attention to the contralateral visual field. These are the same data as published in Gandhi et al. (1999) (pdf).

This is a simple movie shows a comparison of the fMRI response to a flickering checkerboard stimulus to the response to a moving dot stimulus, shown in a psuedo-coronal slice of the brain. Note that the both stimuli excite early visual areas (medial, in and near the Calcarine sulcus), but only the moving dot stimulus excites lateral regions. These lateral respones are believed to in the area homologous to MT and MST in the Macaque. We call this area human area MT+.

This is an interesting way to represent fMRI 'statistical parameter maps'. One major drawback of the traditional way of showing spots of activity on brains is that the threshold for what is active is somewhat arbitrary. Conclusions about the results can vary greatly depending on this choice of threshold. This movie allows the viewer to control the threshold by sliding the time-bar back and forth (rather than just running the movie normally). The example here is the fMRI response to a flickering checkerboard grating vs. uniform gray field showin in a coronal slice. Depending on the threshold, you might conclude that checkerboard stimuli excite a 'network of occipital and parietal brain areas', or that the cortical representaion of a checkerboard stimuli can be found in right ventral occipital cortex.

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