Imaging studies provide support for the neural mechanisms for these cognitive and behavioral abnormalities, documenting cerebral abnormalities that extend well beyond the primary, secondary, and sensorimotor cortices. Structural imaging, positron emission tomography, functional magnetic resonance imaging (MRI), and single-photon emission computed tomography data reveal a pattern of widespread cortical involvement in ALS, with a worsening of this pattern in cognitively or behaviorally abnormal ALS patients. Mild to moderate cerebral atrophy has been documented in ALS patients with unknown cognitive status, with 50% of the sample having parietal atrophy, 38% having insula atrophy, 32% having frontal atrophy, 20% having temporal atrophy, and 12% having occipital atrophy. In addition, white matter degeneration has also been identified, suggesting a loss of fibers from the temporal and parietal lobes. An investigation10 using voxel-based morphometry identified left middle and inferior frontal gyri, the anterior portion of the superior frontal gyri, the superior temporal gyri, the temporal poles, and the left posterior thalamus as areas of brain atrophy in ALS patients, with patients with comorbid FTLD having more severe frontal atrophy.