Biological K/U

Localization of Function

• The idea that certain brain functions are carried out in specific regions of the brain

  • An example of this is the hippocampus carrying out many functions related to memory and emotion

• The opposing idea to localization is that the brain is holistic

  • This is the notion that the functions of the brain are dependent on all or multiple parts of the brain and that these functions cannot be performed in an isolated part of the brain

• Current research shows that these two ideas both are true for different brain functions

Lateralization

• This is a specific type of localization where one hemisphere of the brain is responsible for a particular function

  • This is most obviously seen with language functions

  • Speech and the production of language is performed by one hemisphere while language comprehension is localized to the other hemisphere

• Different types of aphasia help demonstrate how lateralization works

  • Broca’s aphasia reduces the patient’s ability to produce language and affects the Broca’s area

  • Wernicke’s aphasia worsens the patient’s ability to comprehend language and affects the Wernicke’s area

Neurotransmission

• Neurons transmit information through electrical signals 

  • This signalling may require the use of neurotransmitters

• Neurotransmitters are released by a presynaptic neuron as the vesicles holding them fuse with the cell membrane

• These transmitters travel through the synaptic cleft to the postsynaptic neuron where they will bind to the receptors, get lost in the extracellular space, or return to the presynaptic cell via reuptake

• Once the neurotransmitters bind to receptors, a electrical signal will be sent through the postsynaptic neuron and will lead to a signal being sent through the cell if threshold is met

Agonists

• Refers to any chemical increasing the probability of an action potential

• Includes both neurotransmitters and chemicals binding to other sites

Antagonists

• Refers to chemicals inhibiting agonists from having an effect or binding

Neuroplasticity

• The brain’s ability to change its structure to facilitate different cognition and behaviour

Synaptic Plasticity

• The ability of synapses to strengthen, weaken, appear, and disappear

Cortical Remapping

• The movement of one function to another brain region

Hormones

• Are part of a chemical messenger system that influence target cells around the body

• They are generally slower messengers than neurotransmitters are because they are transmitted through the bloodstream rather than through electrical signals

• Hormones increase or decrease the probability of a specific behaviour occurring

Pheromones

• These are chemical messengers that can communicate between member of the same or different species

  • Characteristics such as age or sex can be communicated through pheromones

• The existence of human pheromones has not been determined yet and there is also no clear idea of where these signals are processed and which organ receives them

  • The vomeronasal organ (VnO) is hypothesized to be where pheromones are received but only 50% of the population have them and it appears to be vestigial

  • The accessory olfactory bulb may be where these signals are processed although they disappear as humans age

Kinship Studies

• Measure the frequency across generations or within a generation

• Use case-control studies where individuals are categorized as having or not having a specific behaviour/condition

  • Researchers examine in retrospect if there is a difference in risk factors between groups

Genetics

• Genetic inheritance is a basic principle of genetics and explains how characteristics are passed from one generation to the next.

• Genes and their DNA are passed down from parents to their offspring

• Twin studies allow researchers to look at the effect of genetic inheritance while keeping environmental variables relatively constant.

• Twin studies attempt to solve the problem of not identifying the genotype by using identical (MZ) and fraternal (DZ) twins.

  • Although the genotype is still not identified, MZ twins have the same DNA and DZ twins do not.

  • Comparing MZ and DZ twins allow psychologists to determine whether the disorder is influenced by genetics, as due to both DZ and MZ twins growing up in similar environments, genes are the only factor that may determine whether both twins express the disorder or not

Concordance rate is the probability that a pair of twins will both have the phenotypic trait given that one pair has the trait.

5-HTT Gene

• This gene may play a role in serotonin pathways, a molecule associated with MDD

• Different alleles of this gene may therefore lead to differences in the pathway and increased or decreased risk of MDD

Magnetic Resonance Imaging (MRI)

• A scanning technique used to produce static 3D visualizations of the brain

  • Uses magnetic fields and radio waves to map the activity of hydrogen

  • Depending on the tissue’s density, the concentration of hydrogen is different

• Voxel-based morphometry measures grey matter density in MRI images

• Pixel counting is used to determine the area of brain structures