# Neuroplasticity > ## Relationship to the nature–nurture debate ## Relationship to the nature–nurture debate Because neuroplasticity is sometimes viewed as a measure of "the extent of humans' innate instincts," plasticity is closely tied to the nature–nurture debate. Advocates of nature emphasize that plasticity is less extensive than people think; advocates of nurture emphasize that it is greater. ## [Pinker](https://wiki.g15e.com/en/pages/Steven%20Pinker.txt) Cases in which plasticity seems high: > Reorganization of brain tissue in response to new tasks is particularly dramatic when people lose a sense or body part. People blind from birth use the visual cortex when reading Braille. People deaf from birth use the auditory cortex when signing. Amputees use the cortical areas formerly responsible for the missing parts when moving other body parts. … > > All this means that the allocation of brain tissue to and processes is not forever fixed by exactly where cells settle inside the skull, but depends on how the brain itself processes information. > > Such dramatic organization can also be seen in brains forming in the . Unlike computers, which are first switched on only after factory assembly is complete, brains are active while being assembled, and that activity can contribute to their assembly. … > > In a remarkable experiment, neuroscientist Mriganka Sur () rewired ferret brains so that signals from the eyes were fed into the primary auditory cortex, the brain area that normally receives signals from the ears. Probing this auditory cortex with an electrode, he found it behaved like visual cortex in many respects. … > > The ferrets even used their rewired brains to move toward objects detectable only by sight. Clearly, information entering the sensory cortex had organized it this way. Visual information had made auditory cortex function like visual cortex. … > > In fact, demonstrations of plasticity are less conclusive than they first appear. The cortical areas supposedly exhibiting neuroplasticity perform very similar activities whether altered or unaltered. --p160-161, [The Blank Slate](https://wiki.g15e.com/en/pages/The%20blank%20slate.txt) But plasticity is lower than it seems: > In most cases, gay men's is not reversed by experience. Some parts of the mind have very little plasticity, and no discovery about sensory cortical wiring changes that fact. --p176, [The Blank Slate](https://wiki.g15e.com/en/pages/The%20blank%20slate.txt) > > Consider now the most astonishing case of neuroplasticity: the ferrets rewired so that visual information entered the auditory and cortex, making these regions behave like the visual thalamus and cortex. Even here, however, water did not turn into wine. Mriganka Sur and his colleagues pointed out that the redirected input did not change the auditory brain's actual wiring, only its pattern of strengths. Accordingly, they found many differences between the repurposed auditory brain and a normal visual brain. Because auditory brain organization is optimized for auditory rather than visual analysis, its representation of the visual field was less sharp and less organized. For example, the visual map was much more accurate horizontally than vertically. This was because the left–right direction in these ferrets mapped onto the auditory cortex's horizontal axis in the genetic map. In a normal animal, that axis receives input from the inner ear, which represents different sound frequencies and is therefore precisely arranged in frequency order. The up–down direction, by contrast, mapped onto the auditory cortex's vertical axis, which normally receives large amounts of information at the same frequency. Mriganka Sur also noted that the new input had not changed the connections between the and other hearing-related brain areas. > > Thus, patterns of input can tune parts of sensory cortex to pick up that information, but only within the limits of existing wiring. --p178-179, [The Blank Slate](https://wiki.g15e.com/en/pages/The%20blank%20slate.txt) > > The impression of unlimited human [neuroplasticity](https://wiki.g15e.com/en/pages/Neuroplasticity.txt) also comes from children's occasional successful recovery from early brain damage. But the existence of —permanent impairments of motor control and language caused by malformations or early brain damage—shows that even the young brain's plasticity is severely limited. --p184, [The Blank Slate](https://wiki.g15e.com/en/pages/The%20blank%20slate.txt)