This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Stereoanesthesia is due to lesion ofa) Nucleus Gracilisb) Nucleus cuneatusc) Cerebral cortexd) Spinothalamic tract 
Select and explain. 
A. abc, B. bc, C. acd, D. bcd
A: abc
Answer: A: abc 
Explanation: Astereognosis/Stereoanaesthesia- Loss of ability to recognize size and shape of an object.
Seen in- lesion of somatosensory cortex, lesion of tractus cuneatus, lesion of tractus gracilis.
Somatosensory cortex lesion- proprioception and tactile sensations are lost while pain and temperature sensations are preserved. 
Tractus cuneatus- formed by fasciculus cuneatus (spinal cord) and nucleus cuneatus (medulla). Pass through lateral portion of dorsal column. Carries sensations of dorsal column- proprioception and tactile sensations from upper part of the body.
Tractus gracilis- formed by fasciculus gracilis (spinal cord) and nucleus gracilis (medulla). Pass through medial portion of dorsal column. Carries sensations of dorsal column- proprioception and tactile sensations from lower part of the body.