Appreciation of shape and size of an object placed in hand is lost in the lesion of: (A) Tractus cuneatus, (B) Tractus gracilis, (C) Lateral spinothalamic tract, (D) Spino reticular tract
Answer is A. 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.