Intelligence in Nature - Jeremy Narby [52]
Peopleâs bodies sometimes know things before people themselves do. In a controlled experiment, scientists asked people to draw cards from four decks, two of which were heavily skewed with penalties. Skin measurements showed that people contemplating the bad decks began sweating more profusely before they themselves could verbalize an intuition about which decks to avoid. Such research shows that emotions are a mix of brain states and body experiences, which include increased heart rate, hormonal activity, and input from the gut brain. It also shows that the body plays a role in the reasoning process. Having a gut feeling is not just a metaphor.
We often think of emotions as mental phenomena, but many emotions require the body to play themselves out. People may feel fear in the pits of the stomachs, or love in their hearts. And when they are deprived of all bodily sensations, they have difficulty experiencing emotion; for instance, people suffering from âlocked-in syndromeââwhich means they are so thoroughly paralyzed that they can only communicate through eye movementsâreport an astonishing lack of fear about their condition. According to neurologist Antonio Damasio, this is because they have no way of using the body as âa theater for emotional realization.â
Though the brain and body work together to know the world, the brain seems to be the key organ that people use to articulate and store their knowledge. Our brains harbor our minds and memories. But what is mind? And what is memory? Mind derives from the Old English gemynd, meaning memory or thought, and stems from the Greek mnasthai, meaning to remember. Mind and memory go together.
Most current theories say that long-term memories are determined by the ways in which neurons connect with one another. Connections between neurons are called synapses. A synapse is a gap, a small space where neurons exchange chemicals known as neurotransmitters. When a neuron communicates with a neighbor, it fires an electrical impulse down its body to the synapses, where it causes the influx of charged calcium atoms; this in turn triggers the release of neurotransmitters, which squirt through the synapses over to the receiving neurons, where they set off new electrical impulses. Recent evidence suggests that synapses strengthen and even duplicate if they are used frequently, and weaken and become less efficient at transmitting charges if they are not used.
Research also reveals that all species with brains, from snails to humans, change the synaptic connections between neurons when they learn and remember. And to carry out these changes, they use the same molecules. Humans are united with other species down to the memory bank and back.
Many scientists now believe that memories are formed and stored in the brainâs pattern of synapses. As each neuron in the human brain can have up to ten thousand synapses, the overall brain can take on almost limitless configurations. Memory appears to be stored in the entire cerebral cortex and to be consolidated through synaptic change in neuronal networks. When our synaptic connections get stronger because we have just learned something, our neurons activate their DNA and synthesize fresh proteins. Scientists now suggest, mainly extrapolating from research on rat brains, that knowledge and memories are etched onto neuronal circuits in this way. Likewise, there is evidence that each time an old memory is brought to mind, the brain consolidates it by making new proteins, before