TMT stands for the Trail Making Test, which is a neuropsychological test that assesses cognitive abilities such as visual attention, cognitive flexibility, and executive functions. It involves connecting numbered circles in ascending order and then switching to connecting circled letters in an alternating pattern (e.g. 1-A-2-B). The test is used to diagnose brain disorders such as dementia, stroke, and traumatic brain injury, and to evaluate the effectiveness of treatments for these conditions.