MRI raw data is acquired in k-space, not as an image. The center of k-space carries coarse contrast and shape; the edges carry sharp detail. Drag the slider to keep only the central fraction of k-space and watch the reconstruction lose detail — and start ringing. That ringing is the Gibbs / truncation artifact.
Try this: pull the slider down to ~20–30%. Notice the reconstruction still has the right overall shape and contrast (that information lives near the center of k-space) but sharp edges now ring with alternating bright/dark bands, and fine structure blurs away (that information lived at the edges you just threw out). This is exactly why more k-space lines = a bigger acquisition matrix = sharper image, at the cost of scan time.