Psychometrically matched tasks evaluating differential fMRI activation during form and motion processing.

Objective: Deficits in visual perception and working memory are commonly observed in neuropsychiatric disorders and have been investigated using functional MRI (fMRI). However, interpretation of differences in brain activation may be confounded with differences in task performance between groups. Differences in task difficulty across conditions may also pose interpretative issues in studies of visual processing in healthy subjects.

Deep brain stimulation creates an informational lesion of the stimulated nucleus.

Deep brain stimulation (DBS) is an effective treatment for movement disorders, but the mechanisms are unclear. DBS generates inhibition of neurons surrounding the electrode while simultaneously activating the output axons of local neurons. This dual effect does not explain two hallmarks of DBS effectiveness: symptom relief is dependent on using a sufficiently high-stimulation frequency, and clinical effects are analogous to those produced by lesion.