Psyc201 Test 1, Week 2 Flashcards
Research Methods: Imaging
EEG, fMRI, PET, Microscopy.
Research Methods: Manipulation
Brain damage, drugs, genetic manipulations, direct brain stimulation.
Brain Damage (Manipulation)- pros and cons
(“spontaneous” or induced). Pros: Reveals role of specific brain areas. Cons: Lesions in humans are often large and variable. Animal studies allow for more controlled lesions.
Chemical Lesions
Solution to brain damage (manipulation).
Direct Brain Stimulation (manipulation)
Electrical or magnetic stimulation to activate brain regions.
Deep Brain Stimulation
Used therapeutically, especially for Parkinson’s disease, by implanting electrodes in the basal ganglia.
Transcranial Magnetic Stimulation (TMS) (stimulation of brain)
- low level: neuronal excitation
- high level: neuronal inhibition
- Mostly used for cortical studies (2-3 cm depth)- don’t go much further, subcortical structures aren’t accessible by this technique
Direct stimulation of the brain (electrical or magnetically) Pros and Cons
Pros: Reversible, non-invasive. Cons: Stimulates/inhibits all cells, limited to cortical areas.
Microscopic Imaging
High spatial resolution, but only post-mortem.
Electroencephalogram (EEG) (electric imaging)
Measures electrical activity on the scalp. Pros: High temporal resolution. Cons: Low spatial resolution, mainly cortical.
Structural MRI (magnetic imaging)
Measures hydrogen, good spatial resolution, shows brain structure.
Functional MRI (fMRI) (magnetic imaging)
Measures BOLD (blood oxygen level dependent), reflects brain activity (function). Pros: Good spatial resolution. Cons: Low temporal resolution, measures correlations, not causality.
Types of Imaging
- Microscopic imaging.
- Electrical imaging.
- Magnetic imaging.
- Chemical Imaging.
Positron Emission Tomography (PET) (chemical imaging)
PET scans use small amounts of radioactive substances, called radiotracers or radiopharmaceuticals, that are injected, inhaled, or swallowed
* Works with relatively weak radioactive compounds.
* The compounds are selected because they bind to proteins of interest.
Advantage: we can measure changes in brain chemistry, spatial resolution is reasonable.
Limitations: expensive, requires synthesis of radioactive ligands, low temporal resolution
Early Brain Development
Starts around 3 weeks into gestation, involves neurogenesis, gliogenesis, synaptogenesis, myelination, and synaptic pruning.
Brain Size at Birth
Approximately 300 grams.
Brain Size at 1 Year
Approximately 1000 grams, near adult size.
Neurogenesis
Development of new neurons.
Development Sequence
Sensory systems develop before integrative systems.
Synaptic Pruning
Strengthening useful synapses and eliminating unnecessary ones.
Axon Pathfinding
Axons follow chemical trails to their targets, guided by factors like NGF.
Nerve Growth Factor (NGF)
Protein released by target cells that strengthens axon connections.
Apoptosis
Natural cell death process when axons don’t receive NGF.
Prefrontal Cortex Development
Last brain structure to fully develop, myelination completes around age 20.
Brain Plasticity After Damage
- Neurons are postmitotic so they can’t divide and so cells can replicate when they die.
- However, new cells are being formed in some brain structures, such as the hippocampus and striatum.
- These new cells are more related to learning and memory, not to recovery
Brain compensates through increased activity in surrounding areas, collateral sprouting, and denervation supersensitivity.
Stroke
Temporary dysregulation of blood flow, either ischemia (lack of blood) or hemorrhage (excess blood). Both forms of stroke impair the Na+/K+ pump, leading to excess Na+ inside the cell.
This increased Na+ leads to enhanced glutamate release, which can ultimately kill cells
tPA (tissue plasminogen activator)
Used to break up blood clots in stroke treatment, must be administered quickly (within 4.5 hours).
Collateral Sprouting
the growth of intact axons into neighboring denervated territory
Denervation Supersensitivity
Increased sensitivity of receptors after loss of input.
Phantom Limbs
Caused by reorganization of the somatosensory cortex after amputation.
Axonal sprouting
The growth of new nerve endings which connect with other undamaged nerve cells to produce new neural pathways
Blending Theory of Heredity
Incorrect theory that offspring are an average of their parents’ traits.
Gregor Mendel
Discovered basic principles of heredity through pea plant experiments.
Elements of Hereditary
There are two elements of heredity, one from each parent. Often one element dominates, and the other is recessive.
Allele
A variant form of a gene. (in flower scenario, w and P)
Homozygous
Having two identical alleles for a trait (e.g., ww or PP).
Heterozygous
Having two different alleles for a trait (e.g., wP, Pw).
Chromosomes
Structures containing genes, 23 pairs in humans.
DNA Bases
Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
DNA Structure
Double helix composed of sugar-phosphate backbones and base pairs (A-T, C-G).
DNA Replication
Process of producing two identical DNA copies (molecules) during cell division.
Transcription
Process of DNA being copied into RNA.
Translation
Process of RNA being used to create proteins. Proteins are made up of amino acids.
3 bases form the code for one amino acid.
RNA Bases
Adenine (A), Uracil (U), Cytosine (C), Guanine (G).
Mutation
A change in the DNA sequence.
COMTVal158Met Mutation
A single DNA base change affecting dopamine breakdown and executive function. (COMT is a protein that breaks down dopamine)
Epigenetics
Changes in gene expression without altering the DNA sequence, often due to environmental factors.
DNA in the nucleus
DNA is very long (about 2 meters) so to get it into a cell nucleus (about 0.006 cm3), it has to be very tightly bound.
Therefore chromosomes have special proteins (histones) that are positively charged to bind the negatively charged DNA.
Epigenetic Changes vs. Mutations
Epigenetic changes alter protein production (quantitative), mutations alter protein structure (qualitative).
