Malcolm, aged 35, is severely depressed. because of this he is given electroconvulsive shock therapy. after treatment, he is sent home and does much better. however, his tv-watching behavior is strange. malcolm thinks that last year's episodes of his favorite series are new. malcolm is showing signs of

Malcolm is showing signs of retrograde amnesia.

Explanation:

Amnesia is a memory disorder that causes the individual to lose everything stored in the frontal, temporal and parietal lobes throughout his or her life. Memory loss may be partial when the individual temporarily remains unaware of his past; or total, when you no longer remember and there are no more possibilities for past recall.  Amnesia is usually caused by some kind of degenerative neurological disease or problems related to the parts of the brain responsible for storing information.

A specific type of amnesia is being shown by Malcolm, retrograde amnesia that can be conceptualized as the type of amnesia where the individual remembers only the events that occurred after the trauma, forgetting the past events. Malcolm forgot that he had already watched episodes of his favorite tv show after receiving electroconvulsive shock therapy.