Rigidity is characterized by a velocity ... muscle tone and can be caused by a .... lesion

Rigidity is characterized by a velocity-independent increase in muscle tone. This means that the resistance to passive movement remains constant, regardless of the speed at which the movement is performed. It is a type of hypertonia, or increased muscle tone, and is different from spasticity, which is velocity-dependent.

Rigidity can be caused by a lesion in the basal ganglia, a group of structures in the brain involved in coordination of movement. These lesions can be due to various conditions, including Parkinson's disease, Huntington's disease, and other forms of parkinsonism. In Parkinson's disease, for example, there is a loss of dopamine-producing cells in the substantia nigra, a part of the basal ganglia. This leads to an imbalance in the activity of the basal ganglia, resulting in symptoms such as rigidity, bradykinesia (slowness of movement), and tremor.