What Are the Signs of Left Brain Damage?

The two hemispheres of the human brain show a phenomenon of one side when performing speech and related advanced psychological activities, which is called unilateralization, also known as lateralization, or asymmetry ( asymmetiy). This phenomenon was discovered by clinical neurologists as early as the mid-19th century, and in recent years, due to the adoption of multiple technical methods, people have explored it more deeply and extensively, especially in neuropsychology. The academic circle has become a main research content and has become a subject that has made a major breakthrough in the field of neuroscience.

The activities of the two hemispheres of the brain are not completely separated, but coordinate with each other. Loss of function due to damage to one hemisphere can be compensated by the other hemisphere; in the split brain experiment, some patients have obvious abnormal performance when performing tests that require the participation of both hemispheres, using dual listening and quick indication Other methods have also proved that the specificization of cerebral hemisphere function on both sides is not absolute. Regarding the concept of one side of brain function, there may be such a view: the functional activities of the two hemispheres of the brain have both a relatively independent specificity and a unified unity of mutual cooperation. In terms of a particular cortical advanced function, one hemisphere plays a "superior" role that the other hemisphere cannot. Unilateralization is not absolute but relative. [1]
In recent decades, with the deepening of clinical observation and the development of experimental technology and the use of new methods, although no new materials have been found that conflict with previous clinical observations about the function of the left hemisphere, but for the right hemisphere, It has been noted that it plays a major role in various non-verbal forms of psychological activity, such as perception and memory of images, perception and orientation of time and space, and perception and memory of music. It plays a role even in some aspects of speech activity.
Studies of unilateral somatogenesis have focused on two areas:
(1) Explore the earliest period of lateralization and developmental changes in childhood. (Note: The division of infants and young children here is based on medical standards.)
(2) Compare the degree of similarity of the adult side of the identical twin and the fraternal twin. Anatomical studies have shown that during fetal and neonatal periods, the left and right brains have asymmetric features. Although this suggests a genetic basis for lateralization, there is also evidence that early in life (infancy), language activity is governed by both brain hemispheres. The linguistic process of language was not established until the age of five (Krashen and Harshman 1972). Both cerebral hemispheres are involved in language development at the age of 2 to 3 years, and with the acquisition of reading and writing skills, the lateralization process is also developing. Therefore, damage to the left or right brain during the first one or two years of life (unless it is quite severely damaged) usually does not hinder the development of language function (Basr1962). Children aged 5 to 10 years have aphasia due to left brain injury, but when they are over 10 years of age, symptoms of aphasia are persistent (Su-gar1952). Comparative studies using genetic methods have found evidence of genetic inheritance in one side. SePringer and Sarleman (1975) conducted double-hearing experiments on adults with fraternal and fraternal twins, and the results showed that adults with fraternal twins were more heterosexual than fraternal twins, regardless of size Or direction, both are obviously similar. There are many sources of research on lateralized individual occurrences regarding the causes of the hands.
The above research shows that the occurrence of lateralization is the result of complex genetic and environmental interactions.


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