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
[{'content': 'Stereoanesthesia is due to lesion ofa) Nucleus Gracilisb) Nucleus cuneatusc) Cerebral cortexd) Spinothalamic tract \nSelect and explain. \nA. abc, B. bc, C. acd, D. bcd', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Astereognosis/Stereoanaesthesia- Loss of ability to recognize size and shape of an object.\nSeen in- lesion of somatosensory cortex, lesion of tractus cuneatus,\xa0lesion of tractus gracilis.\nSomatosensory cortex lesion- proprioception and tactile sensations are lost while pain and temperature sensations are preserved. \nTractus 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.\nTractus 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.', 'role': 'assistant'}]