Brain Lesions and Neural Activity Tracking

• Ablation involves removing or damaging brain tissue, often in animal studies, like severing the corpus callosum.
• The brain performs a function, while the mind performs the behavior.
• A brain area can be vital in functioning but not necessary to continue.

Producing Brain Lesions

• Methods of producing lesions include using a vacuum, heat, or excitotoxic lesions.
• Heat is effective but kills all tissue, including somas, axons, dendrites, and glial cells.
• Excitotoxic lesions involve exciting neurons to the point of death through liquid injection.

Controls

• Sham lesions, such as saline or placebo injections, serve as controls for excitotoxic lesions.
• Temporary lesions allow observation of before-and-after effects.
• Muscimol, a GABA agonist, excites GABA receptors, temporarily blocking action potentials to create temporary lesions.

Tracking Neural Activity

• Anterograde labeling involves movement from the soma to terminal buttons.
• It identifies which neurons are connected across structures, like the limbic system to the cortex.
• Retrograde axoplasmic transport involves movement from terminal buttons to the soma.
• In Parkinson’s disease, retrograde transport could deliver dopamine from the bloodstream to the axon to address dopamine deficiency in the basal ganglia.
• Transneuronal tracing tracks connections between neurons.
• Viruses can be used to distribute tracking behavior throughout the body, as typical ligands act only on one neuron.
• Tracing can be anterograde, retrograde, or both.

Genetic Methods

• Genetic methods involve targeting specific genes and altering their function.
• "Knock out" refers to turning off gene expression.
• Twin studies are used to study nature vs. nurture, comparing dizygotic and monozygotic twins.
• Adoption studies are also used to examine nature vs. nurture.
• A gene is a segment of DNA that codes for a protein.
• An allele is a form of a gene; everyone has different alleles.
• Exons are expressed, while introns are junk DNA.

Optogenetics

• Optogenetics involves altering genes through genetically modified viruses.
• Genes that embed photo-sensitive ion channels are inserted onto a harmless virus, like inserting photoreceptors (originally available in algae) into rats.
• Able to target specific genes to turn "on" or "off."
• Requires a light source.
• Is not permanent.

Memory

• Inducing flashbacks of positive memories in mice has decreased depression-like behaviors.
• False memories can be planted through optogenetics.
• Specific memories can be erased.
• Memories can be recovered.