French physician Pierre-Paul Broca further hypothesized that language ability was located in the left hemisphere of the brain.  He based his theory on the autopsies of two men who had lost their power of speech.  Both showed atrophed areas of the left hemisphere of the brain.  He observed that some children whose language-processing area in the left hemisphere had been destroyed nevertheless did develop normal speech.  He reasoned, correctly, that their speech function must have transferred to the same region in the right hemisphere.  Today we know that good teaching and parenting can stimulate brain regions to take on new functions.

German doctor, Carl Wernicke began focusing on stroke patients' inability to understand speech.  When speaking, these patients struggled to think of even simple words such as hat or pencil.  Their inability to understand and use words was accompanied by a loss of ability to read and write.He noticed that as the patients recovered their ability to to understand words, their speech and reading also improved. However the, the ability to call a word to mind quickly, or to express oneself  in writing, remained poor. Wernicke was correct in suggesting that these losses were the result of damage to certain parts of the temporal lobe.

Hughlings Jackson agreed that language is commonly located in the left hemisphere, but he was among the first to suggest that for some people, left-handers, for example, language could be located in the right hemisphere.  Jackson felt that the right hemisphere controls certain types of speech messages because some of his patients who had suffered left hemisphere damage could still use emotional expressions ("Oh my God") or respond with language that had become automatic habits ("yes", "very well").  This knowledge helps us understand the wide variety of differences in abilities among individuals. In addition we now know that the loss of ability in one area because of brain injury may have an effect on other skills that also depend in part on that ability.  For example, language weaknesses and the inability to sort out the order of sounds one hears in words can be linked to reading, writing and comprehension difficulties.

Sir Henry Head did not believe that each brain region served a different function. Head saw the brain as a complex neural network crossing different brain regions. Therefore injury to one area would affect many functions.  Head thought that it was wisest to plan educational interventions based on what professionals observed in their patient's behavior, not try to pinpoint which area of the brain was injured. He used victims of gunshot wounds to the head from WWI to draw his conclusions.

In reaction to so much research with adults, Jon Eisenson suggested that, although children could experience poor language deveopment because of brain injury before, during, or after birth, these delays also could have resulted simply from a lag in their brain's maturation. Unlike adults, the children whom Eisenson studied hadn't lost speech.  They were slow to develop speech skills in the first place, such as vocabulary, grammar, and comprehension. Eisenson believed that these children could not speak correctly because they had a hard time figuring out the meaning of the speech they heard. This was important research into how auditory information is processed.

Charles Osgoode proposed a normal language development model as a way of understanding learning disabilities. He proposed that there were two stages to all behaviors: decoding (interpreting what signals from the environment mean) and encoding (expressing oneself).  Each stage has 3 levels of organization: (1) projection, in which incoming or outgoing signals are wired to appropriate brain areas. (2) integration, in which incoming or outgoing neural signals get organized and (3) representation, in which meaning and thinking take place. This model helped shape the development of tests and remedial programs for children.

Helmer Myklebust firmly established the link between language and learning disabilities.  He proposed that reading depends on inner language, comprehension, and reading skills. This group of researchers reinforced the need for individually tailored, intensive, and early remediation efforts to raise not only the child's language abilitiesbut, as a result, also their intellectual,academic and social skills.

Kurt Goldstein attributed the unusual behavior patterns of some brain-injured veterans of World War I to defective processing of and reaction to visual information. Their frustration with processing visual information extended into daily life as they tried to match their socks in the laundry or hold attention on a speaker. Goldstein listed the following symptoms: 1. Being distracted by objects and people around them. 2. Having trouble figuring out what was important and what wasn't. 3. Repeating behavior over and over again. 4. Showing extreme purposeless behavior.  5.Breaking down emotionally when they couldn't control their behavior. 6. Becoming overly rigid in arranging their personal possessions and time schedules.

Heinz Werner & Alfred Strauss developed interventions to speed up the development of children who showed weaknesses in ability to process visual information.  They noticed that some children were very organized in their learning styles while some were less so, and that some adopted a global aaproach while others were very analytical.  Adapting teaching strategies to children's learning styles continues to be an important strategy today.

William Cruickshank was a student of Werner & Strauss.  He supported the practice of grouping children by their instructional needs rather than their diagnoses, a forerunner of today's inclusive practices.

Newell Kephart  built on Werner's & Strauss' assumptions that perceptual and motor development was the basis for learning, and that incorporating movement into learning would help to catch and focus a student's attention.  Kephart developed a perceptual motor remediation program that worked on balance, coordination,eye movements, eye-hand coordination, and visual perception.

Marianne Frostig developed an assessment and a gross-motor and workbook program to help develop children's visual and motor skills so that they would be more effecient and supportive of learning. Frostig emphasized that intensive reading instruction must accompany the visual-perceptual activites and that any programming for students must take into account past education, social environment, interests, attitudes, temperament, abilities and disabilities.  She was also concerned about developing moral and social behaviors.