scientific papers spurred many universities to invest large sums of money in fMRI machines, or âbrain scanners.â
Researchers also repeated Penfieldâs mapping of the sensory and motor homunculi. They observed which locations in area 3 were activated by touching parts of the body, and which locations in area 4 were activated when the subject moved parts of the body. It was thrilling to reproduce Penfieldâs maps with fMRI rather than his crude method of opening up the skull. Researchers also studied remapping, verifying Ramachandranâs claim of a downward shift of the face representation in area 3 of amputees. As the theory predicted, the shift occurredonly in those amputees who experienced phantom limb pain, not in pain-free amputees.
Amputation may not be injury to the brain, but itâs still a highly abnormal kind of experience. Do brains remap in more normal forms of learning? Violinists and other string musicians use the left hand to finger the strings of their instruments. Studies show enlargement of the left-hand representationwithin area 3, which is likely due to extensive musical practice. Itâs impressive that fMRI can not only assign functions to Brodmann areas but also resolve fine changes within a single area. This research is far more sophisticated than studies of total brain size like Galtonâs. It is bound to tell us more interesting things about cortical remapping, and it may even be useful for understanding crippling disordersof movement that seem to be caused by too much practice. Such disorders, known as focal dystonias,have tragically ended the careers of brilliant musicians.
Explaining learning in terms of the expansion of cortical areas or subareas, however, is still in the spirit of phrenology. Itâs not so different in concept from the studies of cortical thickening, and the correlations are still statistically weak. The approach may be powerful, but it has limitations. For example, studies of Braille readers also show an enlarged hand representation. The remapping approach cannot easily distinguish between learning violin and Braille,which are two very different skills. And even if this particular problem can be solved, the general difficulty will remain.
Researchers have one other way of studying changes in the brain, which does not depend on the concept of remapping. Using fMRI, they have attempted to find differences in the level of activation of brain regions. For example, they have reported lower activation of the frontal lobe in schizophrenicsperforming certain mental tasks. At the moment such correlations are statistically weak, but this intriguing line of research may well tell us much about brain disordersand possibly lead to superior methods of diagnosing them.
At the same time, fMRI studies may have a fundamental limitation. Brain activation changes from moment to moment, roughly as quickly as thoughts and actions change. To find the cause of schizophrenia, we must identify some brain anomaly that is constant. Suppose that your car starts to shake whenever you drive faster than 30 miles per hour and turn the steering wheel to the right. This behavior is intermittent, so itâs only a symptom. Itâs caused by something wrong with your car at a more basic level. Noticing symptoms is crucial, but itâs only the first step toward identifying the underlying cause.
Â
Why are we still trying to use phrenology to explain mental differences? Itâs not because the strategy is good. Itâs because we have failed to come up with a better one. Do you know the joke about the policeman who comes upon a drunk crawling on the ground near a lamppost? The drunk explains, âI lost my keys around the corner.â The policeman asks, âWell, why donât you search over there?â The drunk replies, âI would, but thereâs more light under the lamppost.â Like the drunk who works with what heâs got, we know that size
Researchers also repeated Penfieldâs mapping of the sensory and motor homunculi. They observed which locations in area 3 were activated by touching parts of the body, and which locations in area 4 were activated when the subject moved parts of the body. It was thrilling to reproduce Penfieldâs maps with fMRI rather than his crude method of opening up the skull. Researchers also studied remapping, verifying Ramachandranâs claim of a downward shift of the face representation in area 3 of amputees. As the theory predicted, the shift occurredonly in those amputees who experienced phantom limb pain, not in pain-free amputees.
Amputation may not be injury to the brain, but itâs still a highly abnormal kind of experience. Do brains remap in more normal forms of learning? Violinists and other string musicians use the left hand to finger the strings of their instruments. Studies show enlargement of the left-hand representationwithin area 3, which is likely due to extensive musical practice. Itâs impressive that fMRI can not only assign functions to Brodmann areas but also resolve fine changes within a single area. This research is far more sophisticated than studies of total brain size like Galtonâs. It is bound to tell us more interesting things about cortical remapping, and it may even be useful for understanding crippling disordersof movement that seem to be caused by too much practice. Such disorders, known as focal dystonias,have tragically ended the careers of brilliant musicians.
Explaining learning in terms of the expansion of cortical areas or subareas, however, is still in the spirit of phrenology. Itâs not so different in concept from the studies of cortical thickening, and the correlations are still statistically weak. The approach may be powerful, but it has limitations. For example, studies of Braille readers also show an enlarged hand representation. The remapping approach cannot easily distinguish between learning violin and Braille,which are two very different skills. And even if this particular problem can be solved, the general difficulty will remain.
Researchers have one other way of studying changes in the brain, which does not depend on the concept of remapping. Using fMRI, they have attempted to find differences in the level of activation of brain regions. For example, they have reported lower activation of the frontal lobe in schizophrenicsperforming certain mental tasks. At the moment such correlations are statistically weak, but this intriguing line of research may well tell us much about brain disordersand possibly lead to superior methods of diagnosing them.
At the same time, fMRI studies may have a fundamental limitation. Brain activation changes from moment to moment, roughly as quickly as thoughts and actions change. To find the cause of schizophrenia, we must identify some brain anomaly that is constant. Suppose that your car starts to shake whenever you drive faster than 30 miles per hour and turn the steering wheel to the right. This behavior is intermittent, so itâs only a symptom. Itâs caused by something wrong with your car at a more basic level. Noticing symptoms is crucial, but itâs only the first step toward identifying the underlying cause.
Â
Why are we still trying to use phrenology to explain mental differences? Itâs not because the strategy is good. Itâs because we have failed to come up with a better one. Do you know the joke about the policeman who comes upon a drunk crawling on the ground near a lamppost? The drunk explains, âI lost my keys around the corner.â The policeman asks, âWell, why donât you search over there?â The drunk replies, âI would, but thereâs more light under the lamppost.â Like the drunk who works with what heâs got, we know that size
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