Chapter 5 part 2

• Stereotaxic surgery is the first step in many biopsychological experiments, allowing experimental devices to be precisely positioned in the depths of the brain
• Two requirements in stereotaxic surgery: an atlas to provide directions to the target site and an instrument for reaching the target
• A stereotaxic atlas is used to locate brain structures, representing the brain in two-dimensional frontal brain slices with all distances given in millimeters from a designated reference point
• The stereotaxic instrument has two parts: a head holder for positioning the brain and an electrode holder for the device to be inserted, with precision gears allowing movement in three dimensions: anterior–posterior, dorsal–ventral, and lateral–medial
• Lesion methods involve damaging, destroying, or inactivating a part of the brain to assess the behavior of the subject and determine the functions of the lesioned structure
• Four types of lesion methods:

  • Aspiration lesions: delicate removal of cortical tissue through suction
  • Radio-frequency lesions: destroying tissue with high-frequency current
  • Knife cuts: sectioning to eliminate conduction in a nerve or tract
  • Reversible lesions: temporarily eliminating activity in a brain area for testing purposes
• Interpreting lesion effects can be challenging due to the brain's complex structure, leading to potential misinterpretations of lesion effects
• Electrical brain stimulation involves delivering electrical current across the tips of a bipolar electrode to understand the function of neural structures, often producing behavioral effects opposite to lesions at the same site
• Electrical brain stimulation can elicit various behavioral responses depending on the location of the electrode tip, current parameters, and test environment
• Invasive electrophysiological recording methods include:

  • Intracellular unit recording: provides a moment-by-moment record of fluctuations in one neuron's membrane potential
  • Extracellular unit recording: records neuron activity in extracellular fluid, providing firing records but no membrane potential information
  • Multiple-unit recording: involves recording from multiple neurons simultaneously; the electrode tip is much larger than that of microelectrode
  • Invasive EEG recording: a method of recording brain activity through electrodes placed directly on the brain's surface
• Pharmacological research methods involve administering drugs to observe behavioral consequences:

  • Routes of drug administration include feeding, intragastric injection, intraperitoneal injection, intramuscular injection, subcutaneous injection, and intravenous injection
• Selective chemical lesions:

  • Neurotoxins like kainic acid or ibotenic acid can be administered by microinjection to selectively destroy certain neurons
  • 6-hydroxydopamine (6-OHDA) selectively taken up by neurons releasing norepinephrine or dopamine
• 2-Deoxyglucose (2-DG) technique:

  • Involves placing an animal injected with radioactive 2-DG in a test situation to measure brain activity
• Cerebral dialysis:

  • method of measuring the extracellular concentration of specific neurochemicals in behaving animals
• Immunocytochemistry:

  • Labels antibodies with a dye or radioactive element to locate neuroproteins in the brain
• In situ hybridization:

  • Locates peptides and proteins in the brain by exploiting the transcription of mRNA sequences
• Gene knockout techniques:

  • Create organisms lacking a specific gene under investigation
  • Knockout mice are the products of gene knockout techniques
• Gene knockin techniques:

  • Replace or add genes in an organism
  • Transgenic mice contain genetic material from another species
• Gene editing techniques like CRISPR/Cas9:

  • Allow researchers to edit genes at a particular time during development
• Green fluorescent protein (GFP) in neuroscience:

  • Activated in specific cells for visualization in biological research
• Optogenetics:

  • Uses opsins as light-sensitive ion channels to hyperpolarize or depolarize neurons by inserting an opsin gene into a particular type of neuron