Intelligence in Nature - Jeremy Narby [92]
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P. 130: GUT BRAIN
See Blakeslee (1996).
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P. 130: SIGNALS FROM THE BODY TO THE BRAIN
See Manier (1999) who describes Damasioâs research involving card games and skin measurements. Damasio (1999a) writes in reference to a patient with locked-in syndrome: âThe brain lacks the body as a theater for emotional realizationâ (p. 293).
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P. 131: NEURONS COMMUNICATE AT THE SYNAPSE WITH NEUROTRANSMITTERS
Matthews (2000) writes: âWe can actually watch the intricate molecular dance that takes place when neurons talk to each other, and we learn more about the control mechanisms involved. Neurons communicate at special junctions, known as synapses, where the transmitting cell releases a chemical signal into the small gap separating it from the receiving cell. When the transmitting neuron is stimulated, channels in its plasma membrane at the synapse open, allowing calcium ions to flood into the cell. This prompts sacks containing chemical neurotransmitters to fuse with the plasma membrane, releasing their contentsâthe signalâinto the synaptic gap. These neurotransmitters then diffuse across the gap to the neighboring neuron, where they bind to receptors on the plasma membrane and trigger an electrical responseâ (p.835).
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P. 131: SYNAPTIC CHANGE FOR MEMORY
See Hall (1998) on the importance of sea snail Aplysia californica for research on the role of synaptic change in memory and learning. He quotes Eric Kandel, a biologist who pioneered the molecular study of memory by studying Aplysia brains for more than three decades, who declared: âOne of the wonderful things we began to appreciate is that these goddamn invertebrates can learn anything! I mean, they canât learn to speak French, but all the things that Pavlov and the behavioral psychologists had talked aboutâwhat we now call implicit, or non-declarative, forms of memoryâthey could do in spadesâ (p. 30). Stevens (1996) comments: âA cubic millimeter of cortex contains about a billion synapses, so if each synapse could be either strong or weak, then that volume of cortex could store something like 100 megabytes of information. This number cannot be taken seriously for many reasons, but it does indicate the potential power, and thus the great attraction, of the notion that memories can be stored as patterns of synaptic strengthsâ (p. 471).
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P. 131: MEMORY IS STORED IN THE ENTIRE CORTEX
Fuster (2003) writes: âAt the same time, the evidence for the consolidation of memory in one store implicates the entire cerebral cortex as such a store and synaptic change in cortical networks as the essence of that consolidation. This view agrees fully with what in cognitive circles is known as the unitary theory of memory. There is no need for different neural structures to accommodate different kinds of memory if there is one store that can accommodate all memory, whatever its stage or development or use. What is needed, however, in light of the available physiological and clinical evidence, is a complex topography of cortical networks to accommodate the infinitely diverse contents of memoryâ (p. 121).
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P. 131: ETCHING MEMORIES IN PROTEIN
Damasio (1999b) writes: âMoreover, the process by which newly learned facts are consolidated in long-term memory goes beyond properly working hippocampi and cerebral cortices. Certain processes must take place, at the level of neurons and molecules, so that the neural circuits are etched, so to speak, with the impressions of a newly learned fact. This etching depends on strengthening or weakening the contacts between neurons, known as synapses. A provocative recent findingâ¦is that etching the impression requires the synthesis of fresh proteins, which in turn rely on the engagement of specific genes within the neurons charged with supporting the consolidated memoryâ (p. 78). See âFear Memories