Researchers are cautiously optimistic about a revolutionary made-in-Canada treatment for severe and chronic depression -- what could be called a brain pacemaker to override depression. A team at Toronto Western Hospital, which pioneered the technique, has implanted the pacemakers in 16 severely depressed Canadian patients (7 women and 9 men between ages 28 and 71). Eight of the first 12 have had a "positive response" -- meaning their depression has lifted to the point where some returned to work and at least one started a new business. But it's too early to tell with the other four patients, who've received the implants in the last six months.