Causes
To understand a possible/probable hypothesis for the cause for NLD, one should know the basics of the human brain. The brain is divided into two hemispheres, the right and left, which typically complement each other in functioning but are suited for different types of processing. The right hemisphere can integrate information from several sensory modalities at once (can interpret visual and spoken information at once, thereby clarifying how a facial expression can change the meaning of a verbal message) and is best for processing novel information. The left hemisphere processes information presented in a step-by-step fashion and is best at using information once it is well practiced or rote. Spoken language is processed by the left hemisphere, visual or nonverbal information is processed by the right hemisphere, and the right hemisphere also becomes involved in understanding anything novel or contradictory between the verbal and nonverbal messages.
Although neuroscientists are not in complete agreement about the cause of the disorder, Byron Rourke's (1995) "white matter, right hemisphere deficit" hypothesis is commonly accepted as a way to understand these confusing manifestations. Rourke suggests that bundles of fibers connect various parts of the brain and that if these fibers are blocked or have not developed normally at one or several places, communication between or among the parts is impaired. These impairments may be profound or quite mild, so that different students show different characteristics.
The NLD syndrome reveals itself in impaired abilities to organize the visual-spatial field, adapt to new or novel situations, and/or accurately read nonverbal signals and cues. It appears to be the reverse syndrome of dyslexia. Although academic progress is made, such a student will have difficulty "producing" in situations where speed and adaptability are required. Whereas language-based learning disorders have been shown to be genetic in origin, heredity has not, as yet, been linked to NLD. It is known that nonverbal learning disabilities involve the performance processes (generally thought of neurologically as originating in the right cerebral hemisphere of the brain, which specializes in nonverbal processing).
Brain scans of individuals with NLD often confirm mild abnormalities of the right cerebral hemisphere. Developmental histories have revealed that a number of the children suffering from nonverbal learning disorders who have come to clinical attention have at some time early in their development: (1) sustained a moderate to severe head injury, (2) received repeated radiation treatments on or near their heads over a prolonged period of time, (3) congenital absence of the corpus callosum, (4) been treated for hydrocephalus, or (5) actually had brain tissue removed from their right hemisphere.
All of these neurological insults involve significant destruction of white matter (long myelinated fibers in the brain) connections in the right hemisphere, which are important for intermodal integration. Hence, current evidence and theories suggest that early damage (disease, disorder, or dysfunction) of the right cerebral hemisphere and/or diffuse white matter disease, which leaves the left hemisphere (unimodal) system to function on its own, is the contributing cause of the NLD syndrome (definitely not dysfunctional home lives). Clinically, this learning disorder classification resembles an adult patient with a severe head injury to the right cerebral hemisphere, both symptomatically and behaviorally.
Although neuroscientists are not in complete agreement about the cause of the disorder, Byron Rourke's (1995) "white matter, right hemisphere deficit" hypothesis is commonly accepted as a way to understand these confusing manifestations. Rourke suggests that bundles of fibers connect various parts of the brain and that if these fibers are blocked or have not developed normally at one or several places, communication between or among the parts is impaired. These impairments may be profound or quite mild, so that different students show different characteristics.
The NLD syndrome reveals itself in impaired abilities to organize the visual-spatial field, adapt to new or novel situations, and/or accurately read nonverbal signals and cues. It appears to be the reverse syndrome of dyslexia. Although academic progress is made, such a student will have difficulty "producing" in situations where speed and adaptability are required. Whereas language-based learning disorders have been shown to be genetic in origin, heredity has not, as yet, been linked to NLD. It is known that nonverbal learning disabilities involve the performance processes (generally thought of neurologically as originating in the right cerebral hemisphere of the brain, which specializes in nonverbal processing).
Brain scans of individuals with NLD often confirm mild abnormalities of the right cerebral hemisphere. Developmental histories have revealed that a number of the children suffering from nonverbal learning disorders who have come to clinical attention have at some time early in their development: (1) sustained a moderate to severe head injury, (2) received repeated radiation treatments on or near their heads over a prolonged period of time, (3) congenital absence of the corpus callosum, (4) been treated for hydrocephalus, or (5) actually had brain tissue removed from their right hemisphere.
All of these neurological insults involve significant destruction of white matter (long myelinated fibers in the brain) connections in the right hemisphere, which are important for intermodal integration. Hence, current evidence and theories suggest that early damage (disease, disorder, or dysfunction) of the right cerebral hemisphere and/or diffuse white matter disease, which leaves the left hemisphere (unimodal) system to function on its own, is the contributing cause of the NLD syndrome (definitely not dysfunctional home lives). Clinically, this learning disorder classification resembles an adult patient with a severe head injury to the right cerebral hemisphere, both symptomatically and behaviorally.