PERCEPTION.Auditive
perception is fulfilled through cerebral functions highly similar to the
ones that interveen in visual and tactile perception. On the primary cortex
level, the auditive stimulus is received in both hemispheres. This could
be intended to facilitate a reaction in the case of primary audible stimuli
(natural alarms), letís say, that form part of the collective inheritance.
On the other hand, what one could call complex auditive perception, is
found "lateralized". In the left temporal lobe, which is known as "dominant",
the secondary layers of the cortex are especially adapted for the analysis
and the synthesis of talking sounds. In the right lobe, the secondary cortex
is in charge of the perception of complex rythmic structures and of the
organization of sounds of different pitches, thatís to say, of musical
perception.
Local
lesions of the secondary zones of the left temporal cortex in humans, produce
loss of ability to distinguish the sounds of language, which is called
acoustic agnosia or also sensorial afasia. The same lesions when produced
in the opposite lobe, complicating or destroying perception of pitch, timber
and rythmic succesion of sounds, receive the name of sensorial amusia.
This doesn't happen in the perception of other senses. For example, seeing,
functionalized in the occipital cortex, only suffers one type of loss that
is diagnosed as visual agnosia.
Itís
common that a patient goes to the doctor expressing his or her uneasyness
given that he or she doesnít understand what is heard, the words of others
seem to be a meaningless murmur, or what is understood is something totally
different. Probably those symptoms originate from the incipient formation
of a tumor or perhaps they have an easy cure. In any case, what results
difficult for a patient is managing with ease his social, family, or work
life, given that the communicative structure of our society is based in
the "tiranny" of the dominant hemisphere (we live in a conceptual society!),
this is so in eighty percent of humans. For these reasons, itís not common
to receive a visit from a patient suffering from amusia, save counted cases
of musicians or melomaniacs, so the neurologists have not been able to
establish not even approximately a world census of humans suffering from
such illness.
On
the other hand, music accompanied by words is always perceived by both
cortical regions, but the individual establishes priority order in it.
Music,
as an audible organization whose form is the conductive string of content
and whose content is in itself indescipherable, itís abstract and only
translatable in physical and mathematical parameters, itís the human practise
less "reasonable" of many that compose our social structure of communication
and our system of re-creation of memory, thatís to say, culture.
Music apeals to our right hemisphere (non dominant), and becomes practically
impossible to find out which processes eases the preferral of a certain
style of music over another, aside from existing the generalized suspition
that most part of the humanity has not been educated in its musical perception,
when one is probably not found affected by numerous shortcircuits (reversible
or irreversible) in its perceptive mecanism, whether they be of neurological
or physicological nature.
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