In the middle of the past century, scientists thought they had stumbled upon the pleasure circuit in the brain: clusters of neurons that are activated by certain stimuli and induce an emotional state that can lead to addiction and – at least in humans – a subjective sense of well-being.
So it was originally called the pleasure or reward circuit (it includes two regions that seem to play a critical role in getting the party going: the ventral tegmental area and the nucleus accumbens). It involves many types of neurons that, in order to communicate with each other, release substances – neurotransmitters – such as glutamate, GABA, or dopamine. Drugs of abuse, gambling, certain drugs, and other life circumstances can lead to an over-activation of this nervous network and produce significant imbalances that end up modifying both the circuits themselves – the synapses between neurons – and the amount of neurotransmitters that are released in these synapses. This is how addictions and dependencies to certain substances or behaviours emerge.
In popular science, many researchers and popularisers simplify the matter by associating dopamine with pleasure, since dopamine plays an essential role in the nucleus accumbens; but it does not work like that. It is a big – and very common – mistake to relate an encephalic region and a neurotransmitter with a complex function, since the nervous system does not work with isolated modules, nor is there any nerve nucleus that is managed by a single transmitter substance. What we have is networks articulated by the release of a complex chemical broth. The data we now have indicate that the genesis of emotional states and their role in modulating our feelings – subjective perceptions – require more elaborate explanations. For example: the system formed by the ventral tegmental area and the nucleus accumbens does not seem to be directly related to the sensation of pleasure, but is actually more intensely activated by the anticipation of that possible pleasurable thing or situation. Because of this, some researchers have changed the term pleasure or reward circuitry to seeking or anticipatory circuitry. In addictions, motivation orbits around desire and anticipation; the ultimate pleasure – which may or may not come – is for other neural circuits to handle. A person addicted to shopping is more attracted by the colourful and stimulating search than by the actual objects they purchase.
In everyday life, our search circuit is constantly activated: we feel an engaging motivation when we hear of an upcoming visit from a loved one, the announcement that we have a parcel, the smell of a kitchen that anticipates a delicious meal, the preparation of an excursion to the countryside or to the beach, etc. Then it all happens and the visit, the parcel, the meal, or the excursion can be more or less pleasant, but at least we had the initial excitement.
«In popular science, many researchers and popularisers simplify the matter by associating dopamine with pleasure, but it does not work like that»
And all this reflection on the permanent search for pleasure, the continuous generation of expectations, surprise, and desire, is where books come in, which is what I wanted to get at with all the introduction above: a book seems the perfect object to activate the circuit of search or anticipation in a continuous and painless way, albeit, yes, with the possibility of a strong addiction. Each page of a good book – the kind that grabs and holds our minds, the kind that makes us hungrier the more we gobble them down – generates expectation and uncertainty, and activates the desire to discover what surprise the next page has in store, which in turn feeds our desire to search a new. It is expectation, seasoned with surprises, with no end in sight; the perfect addiction, one that feeds us.