9.7.1. Negating an image with math_img

The goal of this example is to illustrate the use of the function nilearn.image.math_img on T-maps. We compute a negative image by multiplying its voxel values with -1.

from nilearn import datasets, plotting, image

Retrieve the data: the localizer dataset with contrast maps.

motor_images = datasets.fetch_neurovault_motor_task()
stat_img = motor_images.images[0]

Multiply voxel values by -1.

negative_stat_img = image.math_img("-img", img=stat_img)

plotting.plot_stat_map(stat_img,
                       cut_coords=(36, -27, 66),
                       threshold=3, title="t-map", vmax=9
)
plotting.plot_stat_map(negative_stat_img,
                       cut_coords=(36, -27, 66),
                       threshold=3, title="Negative t-map", vmax=9
)
plotting.show()

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