Graham Lawton reports the highs, lows and psychedelic purple doors involved in taking MDMA while having his brain scanned...

I'm taking part in a groundbreaking study on MDMA, the drug commonly known as ecstasy. The research is run by David Nutt of Imperial College London, a former government adviser and one of the few UK researchers licensed to study class-A drugs.

His main aim is to discover what MDMA does to the human brain, something that, remarkably, has never been done before. A second goal is to study MDMA as a therapy for post-traumatic stress disorder. The experiment is also being filmed for a Channel 4 documentary called Drugs Live: The Ecstasy Trial, which will be broadcast in the UK next week.

Over the next hour I ride ferocious surges of serotonin that balloon me higher and higher, while trying to focus on a series of tasks. The fMRI machine is going through its repertoire of rackets – rhythmic clankings, throaty roars and what sounds like organ music. At times I feel amazing, at others panicky. Keeping my head still is very, very hard. But I ride it out.

When I'm pulled out 90 minutes later, the drug effects have plateaued. My mind is clear, my movement feels smooth and, aside from some jaw clenching, I feel content and sociable. And surprisingly psychedelic: a purple door is throbbing before my eyes.

I perform psychological tests, but my heart isn't in it. I'm more interested in chatting to the psychologists, doctors, nurses and porters. Finally I head home, and wake up the following day feeling pretty good.

Symptoms

If your computer won't start up normally, you may need to use a disk repair utility to fix the issue. Mac OS X includes two utilities for this—Disk Utility and fsck (a command-line utility). You can also use these even when your computer starts just fine but you want to check the disk for possible file system issues. For Mac OS X 10.4.3 or later, check out "About live verification in Mac OS X 10.4.3 or later," below.

Important: If you're using Mac OS X 10.4 or later, you should use Disk Utility instead of fsck, whenever possible.

In some situations, file system errors may prevent your computer from starting up. This can occur after an improper shutdown, forced restart, or power interruption. If your computer shows any of the following symptoms on startup, use a disk repair utility:

Your computer partially starts but then displays a command line in a text-only environment. You may see the message, "file system dirty, run fsck." Below it, you'll see what's called a command-line prompt, indicated by a number sign (#), that allows you to type a command. If you see this, you'll need to run fsck from the command line (see "Use fsck if necessary," below). Your computer starts but either it won't reach the login screen, or it may reach the login screen but not load the Desktop after you log in. However, you can start up in single-user mode.

If your computer exhibits either of the above issues, here are some things to try to get your computer back to starting up properly again. If you can't start from the Recovery System or Internet Recovery in OS X Lion and Mountain Lion, or you can't find the system discs that came with your computer, see "Use fsck," below.

Resolution Try a Safe Boot

If you're using Mac OS X 10.2 or later, you can start up your computer in Safe Mode, which includes an automatic disk check and repair. If you're using Mac OS X 10.1.5 or earlier, skip to the next section. A Safe Boot, which starts up your computer into Safe Mode, may allow you to start up your computer successfully using a reduced version of the system software. To do this, follow these steps:

Start up in Safe Mode. After the system has fully started up, restart your computer again normally.

If the computer successfully restarts, you do not need to do any more troubleshooting. If the issue persists, try Disk Utility.

Try Disk Utility Start from the Recovery System or Internet Recovery (OS X Lion or Mountain Lion).
If your computer shipped with a Mac OS X Install disc, insert the installation disc, and restart the computer while holding the C key. If using a Recovery partition or Internet Recovery (OS X Lion and later): When your computer finishes starting up, choose Disk Utility from the Utilities window.
If using an installation disc: Choose Disk Utility from the Installer menu.
Important: If you started from an installation disc, do not click Continue in the first screen of the Installer. If you do, you must start from the disc again to access Disk Utility. Click the First Aid tab. Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions. Select your OS X volume. Click Repair. Disk Utility checks and repairs the disk.

Tip: With Mac OS X v10.6 and earlier, always start up your computer from an Install or Restore disc when using Disk Utility to verify or repair your startup volume. Otherwise, you might see some disk error messages.