In a culture such as ours, with an educational system that until recently was accustomed to catering solely to the needs of a single learning style, the boundary is often blurred between what should or should not be classified as a learning difference which merits special provisions--as a learning "disability." What we are slowly beginning to realize, is that those of us who face difficulties learning something one way may very well be able to learn it through a different approach, one more in tune with an alternative but perfectly natural style of thinking. It is becoming increasingly apparent that teaching styles which are adaptable enough to emphasize the natural strengths of different types of students have far more potential to be effective than those which cater to one way of thinking, and which by default hone in on the weaknesses of all students with ways of learning which are outside (what is beleived to be) the norm.
Loosely speaking, the term "learning disability" refers to a condition which inhibits the processing of a specific kind of information such that one may have difficulties learning via traditional educational approaches. There are many specifically diagnosible learning difficulties with distinct characteristics, the exact causes of which are uncertain. Some of these are dyslexia, dysgraphia, dysphonia, and the list goes on. Attention deficit hyperactivity disorder (ADHA), a more general condition which affects one's overall concentration and behavior, is another common learning obstacle which requires special attention.
It should be emphasized that people with specific learning problems or different learning styles are affected by them to varying degrees at different times in their lives. In addition, it is important to realize that learning differences (and difficulties) are quite often completely uncorrelated with I.Q., and I.Q. tests themselves are often outdated and/or grossly culturally biased. A child with dyslexia may be of above average intelligence and still have problems learning to read due a difficulty processing phonological information. And yet, dyslexic children are often taught to read through strategies which help them to circumvent their difficulties and emphasize their abilities. Some individuals develop their own strategies early on in order to compensate for their learning differences, without even being directly aware that they are doing so, and in some instances a "disability" may not be diagnosed until well into adulthood (if at all). Furthermore, a natural part of human diversity is the fact that some people learn well by listening, whereas others must have the time to translate words into pictures before they are able to fully absorb and retain information. Some people have language-related skills which are more highly developed than their abilities in mathematics or vice verse. There are people who work best in groups, where they can discuss issues critically, and people who work best alone or in a motivationally competitive and individualistic environment. Some learning differences are very general, while others are very specific. Therefore, with so many different kinds of intelligence, there is no completely reliable or just way to measure such a complex and diverse human quality.
Recent evidence, acquired through the use of functional brain imaging, supports more than ever the idea that when our brains undergo a task, that task may be broken up into individual parts, each controlled by a different section or combination of sections of the brain. In light of this, it is understandable how a difficulty in processing or conveying mental input or output can be completely unrelated to what happens to that information once it is fully processed by the individual.
Differences in the ways in which people think may arise from genetics, or from the different physical, cultural, and emotional conditions we all experience in our early lives, or, from a combination of all these. There is evidence that substance abuse can have a large effect on the neurological development of a fetus during pregnancy. Even commonly used substances such as alcohol and caffine have the potential to cause severe damage to a developing nervous system. Meanwhile, other studies have shown that there is often a connection between a child's home and social environments and their natural learning style. It is not uncommon for children who suffer severe traumatic experiences, or grow up under dangerous or abusive conditions to develop mental blocks, which inevitably effect their ability to learn. Family interactions or culturally-related behavior paterns may also determine whether a person learns better in a socially interactive environment or in a more individualistic one (for example, discussion versus reading alone quietly).
There are many common misconceptions about what are commonly called learning disabilities, which often lead to the conscious or unconscious stigmatization of children within the classroom, both by peers and teachers. This can have detrimental effects on self-esteem, and yet, who is to say whether many of the problems children experience in the classroom are the result of learning deficits or of non-adaptive approaches to the material?
The advent of functional imaging (FI) in neurological applications has provided a visual window into the realm of neuroprocessing. Much of what has been found thus far parallels information gained from psychological studies. One fascinating example is gender differences in learning styles. It has been observed that in general (though there is some crossover) males in our society tend to take a very linear (step by step) and individualistic approach to learning and problem solving, while females tend to look at the "whole picture" and learn/work better in more interactive settings. Tests incorporating functional magnetic resonance imaging (fMRI) have shown that this corresponds to differences in brain activity between subjects performing problem solving tasks. Men tend to show activity in one portion of a single hemisphere of the brain at a time, while most women seem to have a stronger connection between the two hemispheres of the and use both simultaneously (Gorman, 1995). Whether these tendancies are genetic, related to hormone levels, or due to early cultural and environmental influences is unknown, but what these results really bring home is the connection between what we do and think and the biological processes controlling and/or resulting from our behavior. And so, are thoughts the random byproducts of physiological processes or are the images which now appear on the computer screens in neurology labs merely the biological reflections of human thought? Perhaps it's a bit of both....
Two commonly known learning disabilities (LDs) are dyslexia (of which there are several forms), and attention deficit hyperactivity disorder (ADHD). Recently, both have been studied in detail through the use of functional imaging (FI). Differences in brain chemistry between LD and non-LD subjects have been observed in both cases. This has several implications. For example, in the case of behavior problems such as obsessive-compulsive disorders, therapy has already been shown to result in visually observable changes in brain chemistry. It is possible to use similar techniques to see how the biological changes induced by medications for ADHD correllate with observed behavior and academic performance. Thus FI may also eventually be useful in terms of learning about the biological changes which may occur as individuals with learning difficulties learn new compensating strategies. The following sections give detailed descriptions of of both ADHD and dyslexia, as well as an overview of some of the recent research being done through the use of FI concerning each topic.
[Personal note: Could it be possible for individuals to learn how to use different parts of their brains on command by observing their own brain activity, or is that just too weird?]
A list of on-line references...
Attention Deficit Hyperactivity Disorder, more commonly known as ADHD (or simply ADD), is a condition which inhibits one's ability to control attention and sometimes general behavior. It is most prevalent in children, though often it persists into adulthood. ADHD is frequently accompanied by hyperactivity, and is most often diagnosed in young boys who exhibit behavior problems--particularly in school where they find it difficult to sit still or to remain quiet in class. Recent studies, however, indicate that ADHD occurs just as often in females as in males. The lower recognition rate is the result of a slight difference in symptoms; girls with ADHD tend to be more outwardly reserved than ADHD boys, though they may be just as restless mentally (Leutwyler, 1996).
ADHD, like most obstacles to the learning process, is not related to intelligence. Children with ADHD usually have severe academic difficulties due to their inability to concentrate, not an inability to understand the material. These children often do poorly grade-wise in school though they may be very intelligent. Also, behavior problems in the classroom, such as the high levels of aggression sometimes seen in ADHD children compared to other children, may cause additional problems.
There is no single cause of ADHD. Studies have been made connecting it with Tourette's syndrome, lead poisoning, fetal alcohol syndrome, retardation, childhood depression, anxiety disorders, immune disorders, thyroid disorders, sleep disorders, substance abuse, and others--though it occurs alone as well. Nearly a quarter of all children diagnosed with ADHD develop bipolar disorder (manic-depression) (Sci. News, 1996 (a)). There is also a very high coincidence rate for ADHD and speech and/or reading disorders, especially dyslexia. In addition, there is no clear-cut diagnosis. ADHD is characterized by a long set of symptoms (such as insomnia, frequent distraction due to peripheral conversations in a room, and difficulties reading or performing other tasks due to mental restlessness) which vary in degree from person to person. To complicate things even further, not everyone with ADHD has exactly the same set of symptoms, and many of the symptoms associated with ADHD are symptoms of other problems as well --quite often of those problems which have a high simultaneous occurrence rate with ADHD.
So how do we know that ADHD really exists? There has been a lot of controversy along these lines over the past few years, partially because of the sudden increase in the number of diagnosed cases (it has more than doubled in the past five years) (Leutwyler, 1996). Many, both within and outside the field of behavior and/or learning disorders, have expressed concern that ADHD is being over-diagnosed. Though this is possible, there are many logical factors which have contributed to the increase. For example, ADHD has now been recognized to exist in significant numbers of girls and adults as well as young boys. It should also be taken into account that the percentage of diagnoses is just now beginning to reach the level expected given predictions of what percentage of the population actually suffers from ADHD (Leutwyler, 1996). Perhaps more concrete proof of its existence, however, lies in the connection between ADHD and certain biochemical and structural brain characteristics. These have been discovered through the use of FI. Studies on ADHD incorporating FI techniques are discussed below in further detail.
ADHD is usually treated with stimulants (typically amphetamine derivatives), and sometimes with anti-depressants (in very mild cases caffeine has even been known to help). It was unknown for sometime why exactly stimulants not only decreased the symptoms of ADHD, but often (surprisingly) have a calming effect on patients. A recent study was conducted on young adults with ADHD using Positron Emission Tomography (PET), a functional imaging technique which measures changes in blood flow in the brain in order to determine regional levels of brain activity. The findings of this study, directed by Daniel R. Weinberger of the National Institute of Health Neuroscience center in Washington D.C., suggest that amphetamines may help to enhance brain activity in regions which are being used for specific tasks while decreasing activity in other regions which may otherwise cause interference. This leads to increased alertness, and sharpness of thinking due to the ability to concentrate on, for example, reading a paragraph or solving a math problem (Sci. News, 1996 (b)). The study found that the degree to which activity was improved was also dependent on the complexity of the tasks involved. Dr. Roy A. Wise, a neuroscientist at Concordia University, Montreal, thinks that perhaps the ability to concentrate better decreases anxiety and frustration in ADHD patients, and thus possibly accounts for the calming effect (Sci. News, 1996 (b)).
The Diagnostic and Statistical Manual of Mental Disorders (ed. 3) defines dyslexia as an inpairment in reading skill development relative to that expected given the level of education and intelligence of the person (Rumsey, 1992). There are varying types and degrees of dyslexia. Though in all cases it is primarily a reading disorder, in some, it may affect one's speech as well (Shaywitz, 1996).
According to recent studies, humans (some at least) comprehend language largely through what is called phonological processing (Damasio, 1996; Bakker, 1992; Shaywitz, 1996). Phonological processing is related to how our brains derive meaning from words by breaking them down into their most fundamental components--phonemes. (An example of a phoneme is the phonetic sound made by a single letter, such as the "kuh" sound made by the letter "k.") This breaking down of phonemes is necessary for (auditory) information to be identified, understood, stored, and remembered (Shaywitz, 1996). A condition in the brain which inhibits phonological processing, or more specifically one's ability to separate phonemes or differentiate between phonemes which sound alike, is most likely responsible for at least one kind of dyslexia (Bakker, 1992; Shaywitz, 1996). But this perspective on dyslexia is a fairly recent development. For years, dyslexia, (called congenital word-blindness prior to the 1930's), was thought to be a visual or auditory defect. Though there have been some reports of visual-perceptual problems in a few dyslexic individuals, the overall evidence that dyslexia is a language-based disorder is quite convincing (Rumsey, 1992). Studies on lexial processing--for example, those led by Hanna and Antonio Damasio at the University of Iowa--have used FI to show what is going on in the brain when people perform different language-related tasks. The results of such research strongly support a phonological model of language processing (Hotz, 1996).
Statistics vary concerning how large a percentage of the population is affected by dyslexia. Estimates for school age children range from 2-8% (Rumsey, 1992) to roughly 20% (Shaywitz, 1996). Contrary to common belief, the number of boys to girls with dyslexia is about equal, however more girls than boys tend to be compensated dylexics (Rumsey, 1992; Shaywitz, 1996). This means that they have learned methods with which to cope with the way their brains process phonological information, and though they may still run into difficulties, they are able to learn to read and often perform as well or even better at some language related tasks than many non-dyslexics. It is interesting that more female dyslexics are compensated than male ones, especially in light of recent studies on gender differences in how humans process information. Compensation may be made easier for those whose brains have a stronger connection between the two hemispheres. In men, phonological processing is believed to take place in a single area in the left hemisphere, whereas in women it tends to take place via the cooperation between that same area in the left side of the brain and the corresponding area on the right side (Shaywitz, 1996).
There are at least two developmental forms of dyslexia, and some research has shown there is also what is referred to as acquired dyslexia--a condition which results from brain lesions of non-genetic origin (for example, a head injury resulting from a car accident) characterized by symptoms similar to those of natural dyslexia. There is also some evidence of naturally occurring brain lesions in people with developmental dyslexia.
A paper (published in 1992 in the Journal Of Learning Disabilities) by Dr. Dirk Bakker, a professor of child neuropsychology at the Free University of Amsterdam, discusses two categories of developmental dyslexia known as L- and P-type dyslexia. Bakker hypothesised that when children are first learning to read, the initial skills required utilize the right side of the brain. In more advanced stages of reading, other skills are needed which use the left side. Thus, about two years after a young child begins learning to read, a hemispheric shift should take place, which Bakker's research supports (Bakker, 1992). P-type dyslexia is characterized externally by a very slow reading rate, which Bakker believes is the result of a failure of this hemispheric shift to occur. The result is that P-type dyslexics are required to derive meaning from words through phonological routes; the extra time required for decoding is what results in the slow reading rate. L-type dyslexics, on the other hand, read much faster but are highly prone to mistakes involving the actual substance within the text. This is may be the result of the shift occurring too early, or perhaps it is that verbal processing started out using only the left side of the brain, and the right sided aspect of learning to read was never developed. Thus L-type dyslexics derive meaning directly from the visual shapes of letters and words (Bakker, 1992). Bakker subsequently developed teaching methods based on these findings, which have been implemented at his institution in the teaching of many severe dyslexics to read. His methods have been shown to be successful, though limited, since improvements generally level off mid-way through treatment (Bakker, 1992).
Bakker's research brings to mind many questions concerning more recent findings related to lexial processing and dyslexia, in particular with respect to gender. However, Bakker's research appears to have involved mostly male subjects, and he does not discuss gender differences in language processing. Language processing, as observed in women using FI, seems to be inconsistent with the hemispheric shift reasoning as an overall explanation for dyslexia. In addition, there is the Damasios' recent assertion that we all process verbal meaning through phonological routes.
Many studies using FI techniques have now been made of dyslexia. An article on dyslexia from 1987, published in volume 44 of the Archives of Neurology, concerns a study led by Judith Rumsey which used a regional cerebral blood flow (rCBF) technique (which required the inhalation of xenon 133). increase in asymmetry of cerebral blood flow in both left and right hemisphere of developmentally dyslexic males depending on tasks, suggesting "inadequate bihemispheric integration" (inability to use both sides of the brain interactively(?)); used xenon 133 inhalation technique (rCBF) preliminary PET studies--dyslexic adults reading single words--suggests "asymmetries of glucose utilization"--similar differences in glucose metabolism to those seen in ADHD (cites Zametkin et al). PET would give better resolution + 3-D in order to study lesions and localization some studies show that some types of dyslexia are genetic (Rumsey et al, 1987)--Archives of Neurology, vol. 44, '87. (fMRI safe for children--no radioisotopes, etc.); (Shaywitz 1996) brain activity of dyslexic has be studied using BEAM topological mapping (EEG/ERP mapping technique; less spatial resolution that MRI; similar color-coding to PET misleading)--shows signs of reduced activity in left hemisphere (Hugdahl, 1995) --involves ability to read words accurately--not a comprehension problem, not due to vision or hearing defect, not acquired neurological disorder; affects 2-8% of school children; occurs in roughly equal number in boys and girls. (Rumsey, 1992)--JAMA, vol. 268, No. 7 not unusually prone to word/letter reversal; difficulty in processing phonemes ("distinctive linguistic units") in spoken and/or written language. phonological model--to be identified, understood, stored, retrieved must be broken into tiny pieces--phonetic units; in dyslexia ability to break up phonemes in impaired; mainly reading disorder, but can also (predictably) affect speech; affects 20% of school children; phonological awareness/training improves ability to read; compensated dyslexics--perform as well as non-dyslexics on tests of word accuracy, but timed tests showed word decoding still slow and difficult. (fMRI safe for children--no radioisotopes, etc.); more female dyslexics are compensated--see article for gender differences..... (Shaywitz--Sci. Am., Nov. '96) increase in asymmetry of cerebral blood flow in both left and right hemisphere of developmentally dyslexic males depending on tasks, suggesting "inadequate bihemispheric integration" (inability to use both sides of the brain interactively(?)); used xenon 133 inhalation technique (rCBF) preliminary PET studies--dyslexic adults reading single words--suggests "asymmetries of glucose utilization"--similar differences in glucose metabolism to those seen in ADHD (cites Zametkin et al). PET would give better resolution + 3-D in order to study lesions and localization some studies show that some types of dyslexia are genetic (Rumsey et al, 1987)--Archives of Neurology, vol. 44, '87. surface (acquired) dyslexia vs. deep (innate) dyslexia -loss of phonological route vs. loss of both phono. and semantic route -neural nets used to simulate brain damage/dyslexia -deep: patients have harder time reading words with abstract meanings than concrete ones -Eleanor Saffran (Temple University--Philly?) (Hinton, et.al. , 1993)--Sci. Am., Oct. '93. brain activity of dyslexic has be studied using BEAM topological mapping (EEG/ERP mapping technique; less spatial resolution that MRI; similar color-coding to PET misleading)--shows signs of reduced activity in left hemisphere (Hugdahl, 1995)