A 72-year-old man has had poorly controlled hypertension for the past 20 years. Over the past day he has had a severe headache with nausea, followed by confusion, then convulsions. On examination he is afebrile, but his blood pressure is now 260/150 mm Hg. There is bilateral papilledema. Which of the following pathologic lesions is most likely to have developed in his brain during the past day?