Fundamentals of Neuroscience/Developmental Disorders

Type classification: this is a lesson resource.

Subject Classification: this is a neuroscience resource.

Goals

• To learn the characteristic symptoms of several neurodevelopmental disorders
• To understand how these disorders manifest themselves on a neurological level
• To suggest potential therapies or treatments, as well as other areas of current research

An overview of several brain regions related to the study of Autism, with a review of their basic functions.

Autism

Individuals exhibiting difficulties in social interactions, impaired communication abilities, and restricted, and often repetitive, behavior are diagnosed under the more general heading of Autism spectrum disorders. This diagnostic distinction is made to encompass the wide range of manifestations of these symptoms, ranging from severely debilitating forms that make even basic daily functions challenging (which is generally associated more with the Autism subdiagnosis), to more moderate variants where intellectual capabilities may be at normal or even above average level, although social skills and behavioral flexibility remains underdeveloped (which is generally associated more with the Asperger's Syndrome subdiagnosis).

Issues relating to social cues seem to be a recurrent theme in many Autism diagnoses, with patients often failing to respond to speech, avoiding eye contact, delayed acquisition of language, and abnormal responses to important social signals like facial expressions and lack of well-developed theory of mind. Behaviorally, learning disabilities are common among individuals with Autism, as are repetitive movements like rocking and compulsively-enforced routines. Sensory processing issues have also been suggested, due to abnormal sensitivities to light and touch. Very rarely, an Autistic individual may have exceptional abilities in one specific area, as is the case in Autistic savants.

The causes of Autism or any of its variants is not well established, and indeed comparably less is known compared to several other similar neurological disorders. Although Autism appears to have a strong genetic component, this aspect of the condition is not well understood, and many genes and their interactions with the environment seem to be most responsible. In terms of the brain, Autism does not have a distinct marker, although as might be expected, regions involved in the difficult task of social cognition are of chief interest.

A timeline showing expected cortical development (purple) compared with individuals with ADHD (blue)

A handful of therapies and pharmaceueticals have been produced to try to alleviate some of the symptoms of patients with Autism spectrum disorders. Many of these are aimed at improving social skills and promoting independence, and counteracting learning difficulties with early interventions.

ADD and ADHD

Attention Deficit Disorder and the closely related Attention Deficit Hyperactivity Disorder are two fairly common disorders characterized by difficulties in attention and impulsivity, which often surface as problems in academic or workplace environments. Where inattation and impulsivity are accompanied by a persistent level of hyperactivity, the ADHD specification is made, otherwise the condition is considered as ADD. Further subclassifications exist which focus on whether the difficulties arise mostly from poor concentration and attention (inattention) or by elevated activity and impulsivity (impulsivity and hyperactivity) or both.

Evaluations of the patient in academic or workplace settings as provided by parents, teachers, employers, etc. is the most common method of diagnosis. The root causes of these attentional and other difficulties is a major subject of research. A genetic influence has been suggested, most of which relate to genes pertaining to specific brain functions and circuits. For instance, the growth of cortical projections (especially in the prefronal regions) during normal intellectual development may be somewhat lagging behind in individuals with ADHD. This also helps account for how the symptoms of ADHD tend to change with age, with many patients reporting improvement in impulse control but still lingering lapses in attentional focus.

A variety of options are available for the treatment of ADHD. One of the most common is the use of a drug called Ritalin which acts on dopamine-secreting neurons in the prefrontal cortex in order to boost concentration. Alternative therapies try to address the deficits in learning, such as by providing individualized attention for academic settings.

Learning Disabilities

Learning disabilities involve significant difficulties in the acquisition or use of skills such as language, reasoning, or math. These issues are often distinguished from more broad diagnosis of an intellectual disability by a patient having a specific area or areas of difficulty, yet an average IQ and no major problems in daily functioning outside of those specific areas. Dyslexia is the most common learning disability, which affects reading abilities. Other types of learning disabilities include dyscalculia for math skills or dysgraphia for writing.

In the case of dyslexia, individuals read at an accuracy level that is notably below what would be expected given their age and education level. Often, this deficit in reading is accompanied by other difficulties in understanding or properly using language, such as frequent spelling areas or in organizing and associating word meanings. Many of these symptoms can be generalized as phonological problems, meaning that they deal with the relationship between the letters and sounds of words. Brain imaging has supported this idea by implicating many crucial language processing areas which are not activated as they would be expected to during tasks like reading.

Most learning disabilities which are not too severe in magnitude are addressed by educational supplementing. Increased emphasis is placed on the linkages between the letter patterns of words and the sounds these patterns produce as an intervention for dyslexia. Similarly, greater attention to the foundational principles in mathematics can be beneficial to patients with dyscalculia, and greater exposure to areas of difficulty-whether it be math or reading- is also potentially useful.