The posterior columns (Fasciculus cuneatus/Fasciculus gracilis) carry information to the brain regarding proprioception, vibration, discriminative touch and pressure. Physical exam findings suggest a lesion here (the spinothalamic tract carries pinprick/pain and temperature, and these were normal). Since the patient has abnormal findings in the lower extremities, and normal findings in the upper extremities, the answer is Fasciculus gracilis. This is because information from body areas below the level of T6 is carried by gracilis and information from body areas above the level of T6 is carried by cuneatus.