Hmmm, from what I've heard from and read about Susan Greenfield over the last 15 years or so, I would say she thinks a couple of notches deeper on neuroscience matters than most people. She is also very aware of the popular press and the reasons why the public respond the way they do. I wouldn't be surprised if this is a carry on argument from the unproven idea that vaccinations cause autism. There certainly is a huge increase in autism in the last 20 years. Something is causing it.
For what it's worth my opinion is that autism is usually diagnosed before the age of 5 years, sometimes by the age of 3. These kids won't have seen much video games by then - maybe a lot of TV though. I recall reading that autism is pretty much unheard of in developing countries, it's a western phenomena, so something that changed in the last few decades in developed countries is causing this.
I think this all highlights the need for proper research, not knee jerk responses, which may be the exact response the Baroness was after.