Lidocaine brain injections for anxiety...not.

Just under a fortnight ago, the Daily Mail printed an article entitled: "The injection that can cure phobias... unless, of course, you're terrified of needles". In it, the reporter (David Derbyshire, listed as the Environmental Correspondent) suggested that the research, "...could lead to new treatments for phobia." Indeed, the comments section (no longer available on the Daily Mail website) included people who were suggesting that they would sign up for injections to cure their phobias.

The article was reporting a study by Japanese researchers (open access):

Yoshida M, Hirano R. Effects of local anesthesia of the cerebellum on classical fear conditioning in goldfish. Behavioral and Brain Functions. 2010;6(1):20. (Paper here)

The study appeared to be either a replication of a similar study by the same lead author, which involved a number of methods (cooling, ablation) to 'inactivate' the goldfish cerebellum.

Yoshida M, Okamura I, Uematsu K. Involvement of the cerebellum in classical fear conditioning in goldfish. Behavioural Brain Research. 2004;153(1):143-148. (Paper here | Not open access)

In the study, they essentially used an electric shock as the unconditioned stimulus, and light as the conditioned stimulus. In response to the shock, goldfish will naturally exhibit slowing of the heartbeat (bradycardia), and by repeated pairings of the light and the shock, they were able to cause the goldfish to demonstrate bradycardia in response to the light alone. The basic process of classical conditioning is explained at Wikipedia.

Injecting lidocaine into the cerebellum had no effect on the goldfishes response to the first light stimulus nor the electric shock. However, it was found that goldfish with lidocaine in their cerebellums were less able to learn the association between the light and the shock.


So, a superficial glance might suggest that anaesthetising your cerebellum might stop you from getting anxious.

There are some problems with the interpretation of this study demonstrated by the press that picked it up:

1. For many people, a simple phobia might not be so problematic as to warrant injections of local anaesthetic into their cerebellums. Since the cerebellum is essential (in humans) for the coordination and sequencing of complex motor actions, anaesthetising it might result in you being unable to move out of the way of one's feared stimulus. But of course, you will no longer be afraid of it.
2. Classical fear conditioning is not the only learning mechanism involved in the maintenance of phobic responses. In more complex organisims (such as humans), instrumental learning/ operant conditioning also plays a part, and not all phobias have a classical conditioning explanation.
3. There are already effective treatments for most anxiety disorders, and simple phobias. Graded exposure has been around for decades, but due to the emphasis of mental health services on 'severe' mental disorders, many of these simple behavioural treatments have been left out of many people's therapeutic armamentarium.
4. Such a 'treatment' would only prevent the acquisition of a specific association, and there is nothing to suggest that you can wipe out a fear of spiders with an injection that would, of course, be temporary.

I would be surprised if we were seeing lidocaine injections into the brain being available on the NHS at anytime in the near future.