Ray often wakes up at night talking loudly and incoherently. During this time, his heart rate increases, and he recalls vague images of someone pressing on his chest. However, he is never fully awake and returns to sleep. In the context of sleep disorders, Ray is exhibiting symptoms of _____.

A) sleep terrors
B) nightmares
C) insomnia
D) somnambulism

Ray is exhibiting symptoms of sleep terrors, which are episodes of intense fear during sleep that involve screaming, thrashing, and a high heart rate. These episodes typically occur during the first few hours of sleep and are often followed by a return to sleep with no memory of the event in the morning. Nightmares involve frightening dreams that wake a person up from sleep, while insomnia is difficulty falling asleep or staying asleep. Somnambulism, or sleepwalking, involves walking or performing other activities while asleep.