- Intellectual and Developmental Disabilities (IDD)
- Learning disabilities
- Autism Spectrum Disorder (ASD)
- Downs Syndrome
- Fetal Alcohol Syndrome (FAS)
- Cerebral Palsy
- Attention-Deficit Hyperactivity Disorder (ADHD)
- Phenylketonuria (PKU)
- Hypoxia
- Fragile X Syndrome (FXS)
- Rett Syndrome
- Developmental Dyslexia
- Auditory Processing Disorder (APD)

Examples of developmental disorders

Abnormalities in the development of the nervous system that are influenced by both our genes and the environment. Developmental disorders commonly manifest as behavioral abnormalities.

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Brandeis University

California Polytechnic State University, San Luis Obispo

New York University

While not all disabilities can fit neatly into one category, these categories generally encapsulate the types of disabilities through the Impairment Dimension.

-	Cognitive / Intellectual 
-	Chronic Illnesses 
-	Developmental
-	Mental 
-	Physical / Sensory
-	Speech / Communication


Types of Disabilities

- Psychotic disorders
- Antipsychotic drugs
- Mood disorders
- Anxiety disorders
- Eating disorders
- Personality disorders
- Developmental disorders
- Substance use disorders
- Disruptive Behavior Disorders

Focuses of Psychopathology

- Evolution of the Brain and Behavior
- Life-Span Development of the Brain and Behavior

Evolution and Development of the Nervous System

The brain is a highly complex organ that develops in an orderly fashion, as directed by genes and the environment. There are four main stages of brain development that describe how the brain changes in morphology throughout prenatal life. Within these four main stages of brain morphological development, there are six stages describing the development of the nervous system that enable the brain to change in morphology. (Page 194 has images of the morphological changes of the developing brain). 

Stages of Brain Development

In this case, development of the nervous system marks the six distinct stages of cellular development of neurons. The six distinct stages are the following; 

-Neurons form via neurogenesis, or the mitotic division of precursor cells to form neurons.

-The newly formed neurons migrate to their destinations in the developing brain via a process known as cell migration.

-The newly formed neurons become further specialized to execute their assigned tasks via cell differentiation.

-The specialized neurons network with other cells by forming synaptic connections in a process known as synaptogenesis.

-When newly formed neurons or synapses are deemed unnecessary, they are selectively removed (such cell death and synaptic rearrangement are important aspects of plasticity). 

Development of the Nervous System

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Developmental Disorders

Physical and sensory disabilities are defined by physical or sensory impairments to a person's functioning.

Physical/Sensory disabilities

Developmental or acquired impairments to an individual’s speech, language, or hearing. Some individuals may face impairments in more than one area.

Speech/Communication Disabilities

Also called psychological disorders, these are disorders rooted in mental thought patterns that impair the person's functioning, with specific disorders having their own disgnostic criteria. 

Mental Disorders/Mental Illnesses

Chronic illnesses (also referred to as chronic disease or condition) is a condition that lasts for a year or more and requires frequent medical care. Chronic conditions can effect or limit the activities in one's daily life.

Chronic Illness

These include a variety of disabilities that affect cognitive/intellectual ability and functioning.

Cognitive/Intellectual disabilities

Invisible disability is an umbrella term for disabilities that cannot be seen by others and interfere with day-to-day functioning, but do not have a physical manifestation. This "unseen" characteristic is central to the challenges these individuals face in various environments. 

Invisible Disability

Disorder Class: Disruptive, Impulse-Control, and Conduct Disorders

A repetitive and persistent pattern of behavior in which the basic rights of others or major age-appropriate societal norms or rules are violated, as manifested by the presence of three (or more) of the following criteria in the past 12 months from any of the categories below, with at least one criterion present in the past 6 months:
1. Aggression to people and  animals
2. Destruction of property
3. Deceitfulness or theft
4. Serious violations of rules
 
The disturbance in behavior causes clinically significant impairment in social, academic, or occupational functioning.
 
If the individual is age 18 years or older, criteria are not met for Antisocial Personality Disorder
 
Specify age onset:  Individuals show at least one symptom characteristic of conduct disorder prior to age 10 years

[DSM-5] Conduct Disorder Criteria

Borderline Personality Disorder (BPD) is primarily defined by a pervasive pattern of instability across interpersonal relationships, self-image, and mood, combined with significant impulsivity. Individuals with this disorder often experience intense emotions and may engage in frantic behaviors to manage their profound fear of abandonment.

Borderline Personality Disorder

A personality disorder is defined by a pervasive and inflexible personality style that significantly deviates from cultural norms, causing problems for the individual and for others. This pattern typically emerges during adolescence or early adulthood and leads to significant distress or functional impairment.

Personality Disorders

Addictive disorders characterized by a compulsive pattern of drug use and marked by both physical and psychological dependence on the substance. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is used by clinicians to diagnose drug use disorders. Individuals with these disorders often consume more of the substance than intended and persist in its use despite significant adverse consequences.

Substance Use Disorders

Psychotic disorders are severe mental illnesses characterized by thoughts, perceptions, and behaviors that are so impaired the individual cannot function normally and becomes disconnected from reality. This state of being disconnected from the world is known as psychosis. People with these disorders often lose contact with reality and may experience extreme symptoms like hallucinations and delusions. Schizophrenia is a primary example of a psychotic disorder.

Psychotic Disorders

A personality disorder is a long-term deviation in behavior, thoughts, and feelings from the cultural norm and expectancies. Without treatment, a personality disorder causes distress to the individual and creates problems in functioning. 

Personality disorders

Disruptive, Impulse-Control, and Conduct Disorders are a group of conditions characterized by problems related to the self-control of emotions and behaviors. These disorders are distinct from other disorders with emotional or behavioral regulation due to the nature that these problems result in violations of the rights of others and/or significant conflict with societal norms or authority figures. These disorders and their presentation can greatly vary within the category, as well as between individuals. 


Disruptive, Impulse-Control, and Conduct Disorders

Plasticity is how the brain is able to learn and adapt to environments. It exists throughout a person's lifetime, though it tends to be more active in early development when the brain is still forming. Plasticity is one of the key concepts within behavioral neuroscience that affects nearly all systems of the brain and brain functions.

Plasticity

Experience and the environment regulate gene expression in brain development by helping to shape behaviors and a person's surroundings and vice versa. This is called epigenetics.

Genes and Experience Guide Brain Development

- visual deprivation

- early exposure to visual patterns

Individual Differences in Experience Affect Brain Development 

- Memory Impairment

- Alzheimer's Disease 


Brain Changes Due to Aging

The process in which physical/behavioral changes of a population occur over long periods of time. Evolution is a scientific theory that for over the last 150 years, scientists have gathered an overwhelming amount of evidence that supports this theory.  

Evolution 

- Development begins from common structure (dorsal tube)
- Symmetry within brain structures (bilateral symmetry) 
- Construction of spinal nerves with spinal cord (segmentation)
- Communication between brain and spinal cord (hierarchical control) 
- Differentiated neural systems 
- Localized functions

Common Neural Features in Vertebrates

The brain starts off as a single cell: The fertilized egg, or zygote. 

-12 hours after fertilization: The zygote begins dividing such that it forms a small ball of identical cells about 200 micrometers in diameter by three days after fertilization.

-A week after fertilization: The embryo develops three distinct tissue layers that will go on to become the tissues of the body: The ectoderm, the endoderm, and the mesoderm. The nervous system will develop from the ectoderm.

-18 days after fertilization: The ectoderm thickens to develop a structure called the neural plate.

-20 days after fertilization: Cell division at the neural plate proceeds unevenly such that a neural groove forms, essentially an indentation of the neural plate.

-22 days after fertilization: The neural tube forms when the ridges of the neural groove, known as the neural crest. fuse. 

-24 days after fertilization: Development of the nervous system quickens, as the "head" end of the neural tube begins to display the beginning features of the forebrain, midbrain, and hindbrain. The neural tube becomes the interior canal within the central nervous system (CNS) carrying cerebrospinal fluid. Development of the nervous system leads to further differentiation of brain structures. 

Brain Morphological Development

Contrary to the historical belief that all brain cells are present at birth, recent research indicates that neurogenesis, the formation of new neurons, can persist into adulthood. This finding highlights the brain's ongoing capacity for change and development throughout the lifespan.

Neurogenesis in Adulthood

Analyze the following scenario and identify the primary cellular process of brain development that has been disrupted. Explain the cascading effects this disruption would have on at least one subsequent developmental stage.

Disruption in Neural Development

The ventricular zone is a dense region of dividing cells in the developing brain that are the precursors cells of neurons or glia (i.e., the cells that will differentiate to become either neurons or glia). Note that neurons do not form by dividing themselves, but rather by division and differentiation of cells in the ventricular zone.

Ventricular Zone

There are many ways in which a newly formed neuron precisely identifies its destination. Cell migration occurs in an inside-out manner, where the newest cells form the outermost layer of the brain. Two mechanisms of cell migration are known as the following: 

-Radial glial cell migration describes a process in which cells migrate using the scaffolding provided by radial glial cells. Cells might migrate perpendicularly or rostrally to the radial glial cells. 

-Cell adhesion molecules (CAMs) are proteins located on the surface of cells that help migrating cells or developing axons connect with the correct structures of the developing nervous system.

Mechanisms of Cell Migration

On the intercellular level, there are two main mechanisms of neurodegeneration as a result of injury: 

-In retrograde degeneration, a neuron is injured close to the cell body, which initiates cell death of the neuron. If the entire injured neuron atrophies or dies, the neurons that were previously connected to the injured neuron may experience degeneration as well in a process known as transneuronal degeneration. 

-In anterograde degeneration, a neuron is injured farther from the cell body along its axon. The part of the axon that is severed from the neuron is degraded, but the axon may regrow, and new axonal sprouts can connect with postsynaptic cells by the help of CAMs and other factors. 

Mechanisms of Neural Regeneration

There are chemical and structural phenomena that contribute to the development of synapses. Two examples of chemical and structural phenomena are the following: 

-Growth cones are swellings at the tips of axons off which thin, threadlike fibers called filopodia extend. The filopodia of these growth cones can latch onto cellular adhesion molecules (CAMs) , and then contract move the neuron in the direction of the CAM (and, presumably, the location of the postsynaptic cell). Growth cones can also facilitate movement of dendrites, and thereby plasticity, in adults.  

-Chemoattractants and chemorepellents are chemical signals that either attract or repel axonal growth cones, respectively. Gradients of these signaling molecules affect the distribution of neurons during the development of the nervous system. 

Mechanisms of Synaptogensis

Apoptosis is a term used to describe programmed cell death. Cell death is an important aspect of development in both animals and plants, and apoptosis is a selective and organized way to kill cells that was likely established long ago in the course of evolution. 

Apoptosis

Cell-cell interactions describe the process in which one cell influences the differentiation of neighboring cells during the development of the nervous system. This process is a key reason why vertebrate brains are less hardwired and more susceptible to environmental cues and experience. In contrast, invertebrate development, such as in C. elegans, is more hardwired and relies less on cell-cell interactions, making their mitotic lineages strictly predictable and easier to trace.

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