Intelligence in Nature - Jeremy Narby [53]
Short-term memories, which only last up to a minute, do not appear to require protein synthesis. Neuroscientist Barry Connors describes short-term memory as âa dynamic, ephemeral process that has not yet yielded to molecular characterization.â
Long-term memories have recently been associated with the formation not only of new proteins but also of new neurons. For decades, scientists used to believe that the brains of adult animals could not change. But now they have discovered that all animals, including humans, grow new neurons throughout their adult life. And by studying the brains of adult rats, scientists have found that these new neurons are essential for at least one type of memory, fear. Research also indicates that acquiring new knowledge increases the survival of new neurons. Learning, it seems, rejuvenates the brain, from rats to humans.
Recent research on memory has made important discoveries but falls short of explaining how new proteins, strengthened synapses, and new neurons relate to precise memories we can call to mind, such as an image of the Mona Lisaâs face, or a Beatles melody, or the name of Franceâs capital city. After all, proteins, synapses, and neurons are not images, melodies, or names but components of the gelatinous matter that makes up our brains. The mystery remains as to how brain jelly can generate constructs such as mental images. Nevertheless, it now seems established that physical changes in the brain underlie the mental capacities of learning, remembering, and knowing.
Scientists are finding it difficult to learn how the brain learns. According to neuroscientist JoaquÃn Fuster, cognitive information requires the activation of âwide, overlapping, and interactive neuronal networks of the cerebral cortexâ in which âany cortical neuron can be part of many networks, and thus of many precepts, memories, items of experience, or personal knowledge.â And physiologist Eilon Vaadia writes: âIt is widely accepted that large areas of cortex are involved in any behavioral process, and that these areas contain many modules, each consisting of groups of cells that process specific information. It is often assumed that, once the brain matures, each module and each cell fulfills one specific function. But accumulating evidence indicates that this may not be so. Instead it is likely that each cell participates in several different processes. The brain is also constantly changing, and each cellâs effects may be rapidly modified. So it is essential to study a large number of neurons simultaneously to understand how cells communicate and how neuronal interactions are modified in relation to learning and behavior.â
The brain is malleable by nature, otherwise we would neither learn nor know. It wires itself in different ways depending on the experiences we have and the skills we acquire. For example, brain imaging of string musicians shows that the area of cortex that governs the fingering hand is larger than that of the other hand, and that the most-used fingers take up the largest space. There is also increasing evidence that the brain can reconfigure itself when impaired. Brain imaging shows that people who have regained use of a limb after a stroke in their motor cortex have learned to use many distinct parts of their brains in a coordinated fashion to make up for the inactivity of the damaged area. And dyslexic children can learn, by hearing sounds slowly and many times over, to change their brains and use different regions to process language. Some people can even exercise themselves out of paraplegia, because slow and patient exercise allows new parts of their brains to learn to take on the tasks no longer fulfilled by the damaged parts.
Our brains are built to soak up knowledge. They are wired for change. They are transformers. Descartes emphasized