Ludwig Van Beethoven
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L'orecchio umano è perfettamente sintonizzato per distinguere differenti frequenze sonore di varia altezza ed intensità al fine di discernere i suoni ed i rumori che ci circondano.
Altri mammiferi rispetto man, and also exhibit different much more effective performance of the auditory system, but a recent discovery of human attributes to the presence of a single neuron in the brain capable of discerning the finer auditory information. Dr. Itzhak Fried
, professor of neurology and director of the UCLA research center for epilepsy, and colleagues at the Hebrew University and the Weizman Institute of Science report in the January issue of the journal Nature, the discovery in humans of a single neuron capable of a spectacular selectivity and can decipher differences of up to one-tenth of an octave in the frequency range of audible sound.
In fact, the ability of these neurons to decipher the more subtle differences in terms of audible frequencies far surpasses, about thirty times more, the ability to transfer information of the acoustic nerve to the brain.
This is a capacity far greater than that of other mammals but with greater hearing about the frequency range, with the exception of bats.
It 's a paradox, the researchers note, that the neurons of a sound musically untrained ear can decipher small differences in frequency much better than the peripheral auditory nerve.
With other peripheral nerves, eg. those of the skin, the ability to distinguish differences is limited by the tactile receptors in the skin and associated neurons do not show greater sensitivity, in contrast with the hearing where the sensitivity of the neuron exceeds that of the peripheral nerve.
The Israeli researchers, Israel Nelken and Yael Bitterman, the Hebrew University, revealed how neurons respond to different sounds, recording the brain activity of four patients suffering from epilepsy CONSENTING incurable by the use of intracranial electrodes in order to identify the focal point of their fault.
recording of brain activity was effetttuata form using the soundtrack to the films of Sergio Leone The Good, the Bad and the Ugly. "
The result surprised the researchers, a single neuron was able to distinguish subtle frequency differences up to a tenth of an octave.
As a reference point, a cat and a mouse are able to distinguish changes in the eighth, respectively, the cat and the rat third octave.
An octave is the interval between a frequency x, and double it, eg. 1000 Hz and 2000 Hz third octave 1000 Hz and 1333 Hz, one-tenth octave 1000 to 1100 hz.
's a mystery how the evolution has probably retained a capacity unused.
How is developed?
This selectivity is not necessary for the understanding of language but may have played a role in understanding music.
Even untrained listeners are able to decipher differences so mild.
It 'obvious that this capacity is correlated with the cognitive system, the principle of working memory and learning ability, but only further research will be able to unravel the puzzle.
E 'is interesting to note that: This is
acuity of sensors in the human auditory cortex of the brain and not the ability to discern information through the auditory nerve, which could explain the perceived susceptibility to certain human psychoacoustic phenomena.
untrained subjects with normal hearing ability, able to discern differences between the auditory nerve can not carry, can explain the existence phenomena of acoustic perception is not rationally demonstrable.
The document points out the research does not need such a capacity for differentiation hearing, but from another angle it is noted that the discernment of the language is not tied only to the deciphering of words, and that the speech does contain a wide variety information beyond the mere noise of the message. Very thin
variations in tone of voice can be strongly indicative of the emotional state of the person.
The fact that a single neuron can have such discernment questions the default analysis of the brain in large blocks, related to its dimensioni fisiche ed il rapporto tra sensibilità all'ascolto e variazioni strutturali della corteccia uditiva.
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