Lost in thought
Germund Hesslow would like a few things explained

I of the Vortex: From neurons to self by Rodolfo Llinás
Press, £19.50, ISBN 0262122332

BRAINS. What are they for? Prediction, according to Rodolfo Llinás, is "the ultimate function of the brain". An ability to predict dangerous events obviously improves our chances of averting them. Prediction is also useful for fine-tuning movements and saving energy. So far, this sounds reasonable and interesting. But when Llinás suggests that predictive capacity is important to explain what he calls the "mindness state" as well as the self and consciousness, it's hard to tell where he's going.

Llinás is known as a leading experimental scientist who has made major contributions to our understanding of the properties of nerve cells and how they communicate within the brain. In this ambitious book he attempts to outline a coherent view of brain function, tackling all the "big" problems, such as the nature of the self and of consciousness, along the way.

Though I of the Vortex is "aimed toward a general audience", parts of it are difficult even for a specialist. Llinás often begins to discuss specific problems in a deceptively simple style, explaining fairly trivial things in painstaking detail, but rarely makes their relevance to the main argument explicit.

Introducing the basics of his idea of prediction, Llinás calls to mind a situation where you found yourself blinking just before a bug landed in their eye. "You did not see the bug . . . yet you anticipated the event and blinked appropriately to ward off its entry into your eye." He tells us that the anticipatory blink can be explained by "a subconscious sensorimotor image that says close your eye, a bug is coming".

Does this simply mean that stimuli associated with irritation of the eye, through some unspecified mechanism, cause the eye to close? If so, it is trivial and empty--rather like explaining how a drug induces sleepiness by invoking its "dormitive virtues". If the phrase "sensorimotor image" means something more, which I think it does, it becomes more problematic. A familiar example of prediction is Pavlovian conditioning. A classic Pavlovian experiment involves repeatedly presenting subjects with an audible tone, followed by a puff of air to the eye. Both humans and animals learn to blink in response to the tone and in advance of the air puff. Further work shows that this association is formed in the cerebellum--the "little brain" beneath the crinkly grey thing. It works fine when the cerebral cortex above is damaged or absent, and the cortex is where images are usually thought to be located. So where and what is a "sensorimotor image"?

As Llinás approaches his central problem he makes lofty declarations such as "the self is the centralisation of prediction" and "that which we call thinking is the evolutionary internalisation of movement". These sound exciting. But Llinás does not follow them up with explanations of what the neurons in the brain are up to when, for example, prediction occurs or is centralised.

When the book does deal with neurons, a major theme is "oscillations". Llinás has discovered that the excitabilities of neurons in some brain structures oscillate in synchrony. Many neuroscientists believe that such synchronised activity in sets of nerve cells is the mechanism that connects or "binds" different sensory inputs into a coherent experience. Llinás endorses this view--and he also believes that oscillations underlie subjectivity, the self, consciousness and the discontinuous nature of voluntary movements. Exactly how oscillations do these things never becomes clear. As soon as Llinás discusses concrete mechanisms, the argument becomes deeply problematic. In fact, other investigators have contradicted some of his claims about stably synchronised oscillations. This is a book for those who like a lot of "sound and fury" but care less what it signifies.