In broad terms, the phrase learning disability covers any of a range of conditions that affect a person's ability to learn new information. These conditions all affect the brain in some fashion. The most common causes are:
  • defects or errors in brain structure
  • lack of communication between various parts of the brain
  • incorrect quantities of various neurotransmitters, or problems in the brain's use of these transmitters
    • common neurotransmitter problems include insufficient dopamine, improper serotonin regulation, and excessive dopamine reuptake where emitting neurons reabsorb too much dopamine after releasing them to communicate with other neurons (also implicated in depression).

People who born with severe learning disability and with an IQ lower than __ are called mentally retarded (possessing mental retardation). However, the word "retarded" has been abused as an insult to mean somebody is "slow".

Major afflictions that impair learning

Down syndrome, or Trisomy 21

Ultimately caused by an extra chromosome in the genetic makeup of the sufferer. One of the primary consequences of the extra chromosome is mild to severe mental retardation. Other genetic conditions with similar consequences include Trisomy 13 and Fragile X Syndrome.
This condition has several forms in varying degrees of severity. The three primary forms are
  • difficulty in phonetic mapping, where sufferers have difficulty with matching various orthographic representations to specific sounds
  • difficulty with spatial orientation, which is stereotyped in the confusion of the letters <b> and , as well as other pairs. In its severest form, <b> and , all distinguished primarily by orientation in handwriting, look identical to the dyslexic
  • difficulty with sequential ordering, such that a person can see a combination of letters and recognize what word it corresponds to with the help of phonetic mapping, but cannot properly sequence the letters when spelling words.
  • Dyslexia has obvious effects on the ability to learn to read and/or write, as well as more subtle effects on processing visual information
    Language processing disorders
    These are poorly-studied, but have clear effects on learning. Effects can be semantic, syntactic or analytical, or can resemble aphasias.
    Some people have difficulty with planning, sequencing, using inductive logic, or with verbal expression. All can interfere with learning, at both the input and output phases of the process.
    Attention Deficit Hyperactivity Disorder (ADD and ADHD)
    AD(H)D sufferers have difficulty in intiating and maintaining concentration. The underlying neurological causes are not always clear. It also appears that many persons labeled as ADD/ADHD either suffer from other problems, or have not had the thorough neruological analysis needed to help manage their condition.
    Alzheimer's disease
    A condition of the elderly, in which the ability to retain new information is lost. As the condition progresses, the patient begins losing lifelong memories, with the most recent to go first. Eventually, they often regress to childhood, and have such poor memory that they cannot perform simple tasks such as walking from one room to another because they forget where they are going en route.
    Brain injury
    This has multiple causes, and consequently, multiple effects. A few common ones are:
    Stroke - can lead to aphasia
    Damage to the brain tissue - effect depends on what area of the brain is injured
    Lesions and Tumors - effect depends on what area is injured.
    Dysgraphia - inability to write, regardless of ability to read
    Color blindness
    While not a true learning disability, it affects the ability to perceive visual information. When such information is presented in a way that is confusing to the color-blind, learning is compromised.
    Physical handicaps can also impede learning when proper accommodations are not made.
    Blindness interferes with the ability to process visual information, so information must be presented in tactile or auditory form to be learnt.
    Deafness and hearing impairment interfere with the ability to process auditory information. Information presented in auditory format is meaningless to the deaf, and not properly perceived by the hearing impaired. Learning occurs best when accommodation is made by providing visual and tactile means for acquiring information, as well as providing Sign Language interpreters where needed.

    Related conditions: