Appreciation of shape and size of an object placed in hand is lost in the lesion of
Stereognosis is the perception of the form and nature of an object without looking at it. Normal persons can readily identify objects such as keys and coins of various denominations. This ability depends on relatively intact touch and pressure sensation and is compromised when the dorsal columns are damaged.Within the dorsal columns, fibers arising from different levels of the cord are somatotopically organized. Specifically, fibers from the sacral cord are positioned most medially and those from the cervical cord are positioned most laterally. This arrangement continues in the medulla with lower body (eg, foot) representation in the gracilus nucleus and upper body (eg, finger) representation in cuneate nucleus.
Tractus cuneatus
Tractus gracilis
Lateral spinothalamic tract
Spino reticular tract
Nervous system