Neurotransmitters and Genetics Flashcards

Neurotransmitters

• Role of Neurotransmitters: Neurotransmitters relay electrical signals between neurons.

  • Neurons don't physically touch; neurotransmitters facilitate communication across the synapse.

  • When an electrical signal reaches the axon terminal, neurotransmitters are released into the synapse.

  • They travel across the synapse and bind to receptors on the neighboring neuron, triggering a new electrical impulse.

• Impact on Psychiatry: Research on neurotransmitters has transformed psychiatry.

  • Most drug treatments affect core neurotransmitters, influencing their availability or action in the brain.

  • This field is continuously evolving, with new substances being identified as neurotransmitters.

• Specific Neurotransmitter Systems: Extensively studied and will be discussed regarding specific disorders in later chapters.

Genetics

• Behavioral Genetics: Applying genetics to study behavior has revolutionized abnormal psychology.

  • Research spans from the cellular to the population level.

• Behavioral Genetics Approaches: Include family, twin, and adoption studies.

  • Provide insights into whether behavioral traits or psychological disorders run in families.

  • Help determine the extent to which these patterns are due to genetics (heritability) or environment.

• Modern Molecular Genetics Approaches: Use genome-wide methods to examine genetic associations.

  • Allow scientists to discover genetic loci associated with complex traits.

  • Most behavioral traits and disorders are influenced by a combination of many genes and environmental factors (complex traits).

Genetics Basics

• DNA: The building block of life is deoxyribonucleic acid (DNA).

• Human Genome: The complete collection of DNA in humans.

  • Mapped by the Human Genome Project (completed in 2021).

  • Approximately 30,000 genes make up each person.

  • Each gene is a section of DNA; together, genes make an organism unique.

• Chromosomes: In humans, genes are contained on 23 pairs of chromosomes.

  • 22 somatic (bodily) chromosome pairs.

  • One sex chromosome pair.

    • Females typically have two X chromosomes (one from each parent).

    • Males typically have one X chromosome (from the mother) and one Y chromosome (from the father).

• Biological Sexes: There are six different biological sexes

  • X (one in 2000-5000 females)

  • XX (most common female)

  • XXY (one in 500-1000 males; Klinefelter syndrome)

  • XY (most common male)

  • XYY (one in 1000 males; Jacob's syndrome)

  • XXXY (one in 18000-50000 males)

• Alleles: Genes can exist in different forms called alleles.

  • Specific alleles create variation in species.

• Behavior Geneticists: Study genetic effects on personality, attitudes, and abnormal behavior (e.g., extroversion, depression, schizophrenia).

• Behavioral Genetics: Refers to the study of the relationship between genetics and environment in determining individual differences in behavior.

Family Studies

• Family Studies: Focus on whether traits and disorders run in families and, if so, why.

  • Examine family members of someone with a particular disorder (proband).

  • Determine if they are more likely to have the disorder than family members of people without it.

  • If the disorder is more common in the proband's family, it is considered familial or to aggregate in families.

• Family Study Methods:

  • Family History Method: Uses information from one or a few family members to gather information about other family members.

  • Family Study Method: Involves direct interviews with each consenting family member (more reliable).

• Familial Aggregation: Important first step in understanding whether genes might influence a disorder.

• Environmental Influences: Cultural context and shared environmental factors within families can influence behavior.

  • Observed familial aggregation could be due to genetic factors, shared environmental factors, or a combination.

• Large Family Studies: Used to explore the extent to which genes or environment contribute to liability to a disorder or trait.

Adoption Studies

• Adoption Studies: Genetically related individuals live in separate families and do not share a common family environment.

  • Similarities between biological parents and their adopted-away offspring represent genetic contributions.

  • Similarities between adopted children and their adoptive parents measure environmental contributions.

Twin Studies

• Twin Studies: Study similarities and differences between monozygotic (MZ) and dizygotic (DZ) twin pairs.

  • Used to identify genetic and environmental contributions to psychological disorders.

• Monozygotic (MZ) Twins: Start as a single fertilized egg that splits, resulting in genetically identical individuals.

  • Behavioral differences between MZ twins allow examination of environmental influences.

• Dizygotic (DZ) Twins: Result from the fertilization of two eggs by different sperm.

  • DZ twins share, on average, one-half of their genes (like other siblings).

  • Behavioral differences can result from genetic and/or environmental effects.

• MZ Twins Reared Apart: Genes and familial environment are distinctly separated.

  • Studies can examine non-shared environmental factors.

Molecular Genetics

• Molecular Genetics: Used to identify specific genes related to the presence of a disorder.

  • Twin and adoption studies indicate whether genes are involved but do not identify specific genes.

• Primary Methods:

  • Genome-Wide Linkage Analysis: Narrows the search for genes from the entire genome to specific areas on specific chromosomes.

    • Requires large families with many affected individuals or large samples of affected relative pairs.

    • Researchers look for regions of the genome that affected relatives share.

  • Candidate Gene Association Studies: Compares specific genes in a large group of individuals with a specific trait or disorder to a control group.

    • Researchers choose genes in advance based on knowledge of the biology of the trait or gene function.

  • Genome-Wide Association Studies (GWAS): Uses large samples of cases and controls.

    • Tests hundreds of thousands of genetic variants scattered across the genome for association.

Gene-Environment Interactions and Correlations

• Genotype: The genes in our DNA responsible for a specific trait.

• Phenotype: The observable, physical expression of that trait.

• Gene-Environment Interactions: Environmental exposure interacts with genetic risk factors to influence the development of psychological disorders (e.g., stressful life events, cannabis use, child maltreatment in individuals with genetic risk for schizophrenia, severe depression, and bipolar disorder).

• Gene-Environment Correlations: A person's genotype impacts the environment they experience.

  • Example: Children with impulsivity (genetically related to their mother's ADHD) may experience higher levels of hostile parenting.

Epigenetics

• Epigenetics: Focuses on heritable changes in gene expression not caused by changes in the DNA sequence itself but rather by environmental exposures.

  • The epigenome can react and adapt to a rapidly changing environment.

  • Environmental factors can influence which genes are activated or silenced.

  • These changes may be passed down to succeeding generations.

Learning Objectives Summaries

• Nervous System: Two main parts are the central nervous system (CNS) and the peripheral nervous system.

  • CNS consists of the brain and spinal cord.

  • The peripheral nervous system includes the sensory, somatic, and autonomic nervous systems.

  • The autonomic nervous system includes the sympathetic and parasympathetic systems.

• Neurotransmitters: Chemicals that relay electrical signals from one neuron to the next across the synapse.

  • Most drug treatments for psychological disorders affect one or more core neurotransmitters.

• Genetics Research Methods:

  • Family Studies: Examine whether family members of someone with a disorder are more likely to have the disorder.

  • Adoption Studies: Examine genetically related individuals in separate families to differentiate genetic and environmental effects.

  • Twin Studies: Compare concordance rates between monozygotic and dizygotic twin pairs.

  • Candidate Gene Association Studies: scientists compare one or a few specific genes in a large group of individuals who have a specific trait or disorder with a well matched group of individuals who do not have that trait or disorder.

  • Genome-Wide Association Studies: are where scientist compares millions of genetic variants across the genome.

Research at the Individual Level

• Individual Level Research: Complements large group-based studies by allowing for richer examination of details.

• Methods of Study: Case studies and single-case designs.

Case Studies

• Case Study: A comprehensive description of an individual or group of individuals using clinical data.

  • Provides a detailed narrative of abnormal behavior and/or its treatment, but does not allow to draw conclusions about causes of behavior.

• Benefits of Case Studies:

  • Allow examination of rare phenomena.

  • Can generate hypotheses for group studies.

  • May help understand particularly rare behavior (e.g., mass shootings).

• Variations and Limitations:

  • The amount and type of data included vary considerably.

  • Case studies do not allow us to make any firm conclusions about the causes of symptoms or change following treatment because there is not experimental control.

Single-Case Designs

• Single-Case Designs: Experimental studies conducted at the individual level.

  • Incorporate control conditions to demonstrate causal relationships.

  • Control for alternative hypotheses and can lead to causal inferences.

  • Require fewer resources than group-based research and allow for more detailed attention to individual patterns of change.

  • Each person is a complete experiment, participating at various times in both treatment and comparison conditions.

• Baseline Assessment: Measures the behavior targeted for change before implementing any experimental or control condition.

  • Baseline monitoring continues until the behavior pattern is stable.

  • Treatment is then applied and withdrawn with continuous assessment of the target behavior.

• Design Strategies:

  • ABAB Reversal Design: Alternates between baseline (A) and treatment (B) phases.

    • Behavior is first evaluated at the baseline until stability is demonstrated.

    • The treatment is then applied and assessment continues until behavior stability is achieved.

    • Evidence that the treatment was the cause of the behavior change obtained when withdrawn behavior returns to baseline during the second A phase.

    • Further evidence is obtained when the intervention is applied again, another B phase, and another behavior change takes place.

    • Multiple Baseline Design: Only one AB sequence applied, sequence is repeated across individuals, settings, or behaviors when a treatment cannot be reversed.

• Limitations of Single-Case Designs:

  • Do not allow researchers to generalize the results of heterogeneous groups of people.

  • Furthermore, they do not address the impact of differences may be very important in determining treatment response.

  • In some cases, reversing a treatment is unethical or impractical.

Learning Objective Summaries

• Case Studies: Allow the examination of rare phenomena and can be used to generate hypotheses for group studies.

  • They do not allow us to determine the causes of symptoms or change following treatment.

• Single-Case Designs: Experimental studies at the individual level.

  • Most common design is the ABAB reversal design.

  • A and B are alternated such that treatment occurs only during the B phase.

  • These designs, however, cannot be used if learning during the B phase cannot be reversed.

  • In these cases, multiple baseline designs may be used to examine separate AB sequences across individuals, settings, or behaviors.

Research at the Group Level

Studies based on groups of people are the most common types of used in psychology.

Using groups allow researchers to draw conclusions based on the average performance across all participants

Group based studies may be correlational or experimental in nature