It's a Jungle in There: How Competition and Cooperation in the Brain Shape the Mind by David A. Rosenbaum
Authors: David A. Rosenbaum
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excitement that occurs fairly regularly but not nonstop, for that could exhaust you. And you would not want to be endlessly isolated or interminably inhibited, for then your draw on metabolic resources could get dangerously low.
Being a sensory neuron or a motor neuron would give you a good chance of being called on regularly. Your neighbors would want to be in contact with you because sensing and moving are primary tasks. Afferent and efferent fibers are like essential personnel. They serve critical functions. Everyone relies on them.
Other neurons, so-called interneurons—the neurons lying between the afferent and efferent neurons—are important too because they allow forcommunication between the fibers that directly contact sensory receptors and muscle effectors. Interneurons that are removed from direct contact with afferent and efferent fibers tend to support functions that are less directly tied to specific afferent or efferent functions. What they do is more abstract or intellectual. The farther interneurons are from the sensory and motor edges of the nervous system (measured in number of synapses), the more abstract or intellectual their functions tend to be.
Macroscopic Features of Brain Organization
Just as neural fibers entering the back of the spinal cord serve sensory functions, whereas neural fibers exiting the front of the spinal cord serve motor functions, fibers in the back of the brain (opposite the face) also tend to support perception. Brain fibers in the front of the brain (toward the face) tend to support action. This generalization helps make sense of the quote from Geoffrey Hinton, “The brain is locally global and globally local.” Globally speaking, action-related functions are represented toward the front of the brain while perception-related functions are represented toward the back. Between these two poles, the functions are more graded, shading roughly from less to more action-based the farther frontward you go.
The second generalization concerns side-to-side organization. Considering the left versus the right side of the brain, a different division emerges. The left cerebral hemisphere of the human brain is thought be specialized for language, at least in most people. Meanwhile, the right side of the brain is thought to be specialized for spatial processing and artistic or intuitive thinking, again in most people.
These differences were made famous by Michael Gazzaniga and Roger Sperry in the 1960s. Gazzaniga and Sperry studied neurological patients who underwent split-brain surgery to alleviate severe epilepsy. Cutting the major neural tract separating the left and right cerebral hemispheres—the
corpus callosum
—created a kind of “fire lane” that stopped the spread of the neural storm producing epileptic symptoms.
Separating the two cerebral hemispheres led to a surprising result. Visual stimuli shown briefly to the visual field that projected to the
left
cerebral hemisphere could be named by the split-brain patients, but visual stimuli shown briefly to the visual field that projected to the
right
cerebral hemisphere could not. This outcome suggested that the left cerebral hemisphere had access to language while the right cerebral hemisphere did not.
It was not that the right cerebral hemisphere was simply dumb, however, as shown in another test where the same visual stimuli were shown to the left or right cerebral hemispheres of the same patients. This time, the patients were instructed to reach out and grasp the visually pictured object. The reaching was done without visual feedback. When the visual stimulus was projected to the
right
cerebral hemisphere, the correct object could be identified through touch, but it could not be named. When the visual stimulus was projected to the
left
cerebral hemisphere, the correct object could be named but could not be identified through touch. Thus, the right hemisphere could display haptic recognition of the seen object, but the left
Being a sensory neuron or a motor neuron would give you a good chance of being called on regularly. Your neighbors would want to be in contact with you because sensing and moving are primary tasks. Afferent and efferent fibers are like essential personnel. They serve critical functions. Everyone relies on them.
Other neurons, so-called interneurons—the neurons lying between the afferent and efferent neurons—are important too because they allow forcommunication between the fibers that directly contact sensory receptors and muscle effectors. Interneurons that are removed from direct contact with afferent and efferent fibers tend to support functions that are less directly tied to specific afferent or efferent functions. What they do is more abstract or intellectual. The farther interneurons are from the sensory and motor edges of the nervous system (measured in number of synapses), the more abstract or intellectual their functions tend to be.
Macroscopic Features of Brain Organization
Just as neural fibers entering the back of the spinal cord serve sensory functions, whereas neural fibers exiting the front of the spinal cord serve motor functions, fibers in the back of the brain (opposite the face) also tend to support perception. Brain fibers in the front of the brain (toward the face) tend to support action. This generalization helps make sense of the quote from Geoffrey Hinton, “The brain is locally global and globally local.” Globally speaking, action-related functions are represented toward the front of the brain while perception-related functions are represented toward the back. Between these two poles, the functions are more graded, shading roughly from less to more action-based the farther frontward you go.
The second generalization concerns side-to-side organization. Considering the left versus the right side of the brain, a different division emerges. The left cerebral hemisphere of the human brain is thought be specialized for language, at least in most people. Meanwhile, the right side of the brain is thought to be specialized for spatial processing and artistic or intuitive thinking, again in most people.
These differences were made famous by Michael Gazzaniga and Roger Sperry in the 1960s. Gazzaniga and Sperry studied neurological patients who underwent split-brain surgery to alleviate severe epilepsy. Cutting the major neural tract separating the left and right cerebral hemispheres—the
corpus callosum
—created a kind of “fire lane” that stopped the spread of the neural storm producing epileptic symptoms.
Separating the two cerebral hemispheres led to a surprising result. Visual stimuli shown briefly to the visual field that projected to the
left
cerebral hemisphere could be named by the split-brain patients, but visual stimuli shown briefly to the visual field that projected to the
right
cerebral hemisphere could not. This outcome suggested that the left cerebral hemisphere had access to language while the right cerebral hemisphere did not.
It was not that the right cerebral hemisphere was simply dumb, however, as shown in another test where the same visual stimuli were shown to the left or right cerebral hemispheres of the same patients. This time, the patients were instructed to reach out and grasp the visually pictured object. The reaching was done without visual feedback. When the visual stimulus was projected to the
right
cerebral hemisphere, the correct object could be identified through touch, but it could not be named. When the visual stimulus was projected to the
left
cerebral hemisphere, the correct object could be named but could not be identified through touch. Thus, the right hemisphere could display haptic recognition of the seen object, but the left
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