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Franz Gall "observed" 1800s

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Franz Gall "observed" that people with bulging eyes had excellent verbal skills. - Conclusion: brain region for such skills resided behind eyes and was overgrown in such people.

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phrenology

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differences in the structure of the skull determines a person's character and mental capacity - bulges and depressions in skull reflected brain development in those regions.

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identify brain areas

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important for certain behaviors

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determine abilities and personalities by...

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by feeling head bumps

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pseudoscience

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phrenology, an important and accurate concept was the idea that different brain areas are responsible for specific functions

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Basic Methods

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consider whether a particular method is intended to provide information about structure or function

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Structure:

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description . of how the brain is constructed in terms of components, chemistry, connections, etc.

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Function

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experiments conducted to manipulate the brain and determining the consequences of that manipulation. Two flavors: - A. Does a change in the brain change in behavior? - B. Does a change in behavior change in the brain?

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- A. Does a change in the brain change in behavior?

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For example - destroy a part of the brain and then ask how that affects behavior - mutate a gene, and ask how that affects behavior, structure, etc.

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- B. Does a change in behavior change in the brain?

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For example - perform a memory task and ask what part of the brain is active (fMRI) - ask whether an exercise program can lead to changes in brain function and/or structure

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independent variable & dependent variable &correlation

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: a true experiment involves manipulation of variables (independent variable) to examine contrast: correlation which examines whether there is an association between variables (no manipulation of variables)

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Typical methods to study the brain include (7)

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- 1. Neuroanatomy - 2. Neurochemistry - 3. Lesion studies - 4. Stimulation/Activation/Inhibition - 5. Pharmacology- 6. Genetic Mutations - 7. Brain Activity: a. Neurophysiology b. Immediate Early Genes c. Imaging: CAT, PET, MRI, fMRI

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Neuroanatomy

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- 1. Neuroanatomy - structures identified, connections determined

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Neurochemistry

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- 2. Neurochemistry - measure chemical make-up; measure changes in chemical content after a treatment (e.g., drug, lesion, or stimulation)

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Lesion studies

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- 3. Lesion studies - relating structure to function

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Stimulation/Activation/Inhibition

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- 4. Stimulation/Activation/Inhibition - turning neurons on or off to induce behavioral effects

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Pharmacology

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- 5. Pharmacology: effects of drugs

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Genetic Mutations

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- 6. Genetic Mutations - function of genes/proteins in CNS

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Brain Activity

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- 7. Brain Activity - determine what parts of the brain are active during different behaviors a. Neurophysiology - measure electrical activity b. Immediate Early Genes - infer activity based on expression of IEGs c. Imaging: CAT, PET, MRI, fMRI

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histology

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study of the fine structure of the brain using thin sections viewed under the microscope. - early neuroscience was built on histological studies by Cajal and Golgi, whose studies are still referenced today

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light microscopy

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what early histologists used and is still being used to magnify images from thin sections (= slices) of stained tissue.

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electron microscopy (EM)

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highly magnified view of synapses, organelles, etc. in very thin sections of tissue (1-2 µm) - scanning EM - highly magnified view of surfaces

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confocal and 2-photon microscopy

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use of lasers to penetrate tissue and provide detailed (highly resolved) images throughout the tissue. - most microscopy requires preparation of tissue by fixation (such as with formaldehyde) followed by sectioning in a microtome ("small" + "to cut")

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general stains

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certain dyes developed from chemicals and pigments that stain components of cells: Examples: - Nissl for ribosomes (found in the soma cytoplasm), - myelin stains for axon bundles, - DAPI for nuclei - Golgi stain fills the entire neuron to allow complete dendritic "trees" to be seen

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tract tracing (connections)

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allows one to map connections between different areas: - inject a special dye into a particular region A of the whole brain - an anterograde tracer will be taken up by the soma and transported down the axon ("anterograde") to the nerve terminals - a retrograde tracer will be taken up by nerve terminals and transported up the axon ("retrograde") to the soma - in both cases, the tracer is linked to a dye or a 'reporter' to allow it to be visualized under the microscope

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brain imaging (live human)

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-CT Scan- computerized tomography -MRI- magnetic resonance imaging -DTI-diffusion tensor imaging -PET- positron emission tomography

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CT scan

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computerized tomography: X-rays are projected through head. Different tissues absorb differently. Detector records what comes through. Useful for localizing defects.

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MRI

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magnetic resonance imaging: different parts of the brain "resonate" at different frequencies to a magnetic field passed through brain in 3D. - provides clearer images of structure than CT

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DTI

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diffusion tensor imaging - used to map white matter tracts in brain

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PET

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positron emission tomography - measures how active a brain area is and is often used in combination with CT to provide structural information

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Neurochemistry

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a. localization of genes/proteins- immunocytochemistry (ICC)-- autoradiography - - in situ hybridization - b. measuring levels or amounts of genes/proteins- blotting-- microdialysis - - microiontophoresis - c. measuring functional activity of proteins- enzyme activity

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immunocytochemistry (ICC)

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(Neurochemistry a. localization of genes/proteins) -use of antibodies to localize specific proteins (enzymes, receptors or neuropeptides) - brain slices are exposed to an antibody for the protein. The antibody is linked to a dye that allows the antibody (bound to the protein) seen under a microscope

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autoradiography

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(Neurochemistry a. localization of genes/proteins)- attach a radioactive molecule to a neurotransmitter such as dopamine - incubate with brain slices, allow the radioactive NT to bind, and then identify the neurons where binding has occurred by localizing the radioactive signal

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in situ hybridization

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(Neurochemistry a. localization of genes/proteins) - localize the messenger RNA (mRNA, which is usually found in the soma or cell body) that contains the code for a particular protein - for example, use this procedure to determine where mRNA for tyrosine hydroxylase occurs. This will tell you where the cell bodies are for neurons that produce dopamine

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blotting

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(Neurochemistry b. measuring levels or amounts of genes/proteins)- RNA or protein from tissue samples can be separated based on electrical charge and transferred to special paper where the RNA/protein of interest can then be identified and compared between samples

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microdialysis

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(Neurochemistry b. measuring levels or amounts of genes/proteins)-- measure level of neurotransmitter released after drug treatment

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microiontophoresis

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(Neurochemistry b. measuring levels or amounts of genes/proteins)- measure level of neurotransmitter released in single neuron after direct application of substance.

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enzyme activity

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(Neurochemistry c. measuring functional activity of proteins)- enzyme assays: dissect region of brain and determine the rate of activity of an enzyme of interest (e.g. tyrosine hydroxylase, acetylcholinesterase, etc)

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Lesions

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- determining consequences of injury or mutation- a. Unintentional brain defect/damage 1. due to trauma/infection 2. due to genetic mutation b. Directed/Intentional 1. Create brain lesions with various methods (need to use a stereotaxic apparatus to locate correct sites) 2. Create mutations 3. Prevent normal function (in vivo or in vitro)

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lesions due to trauma/infection

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(a. Unintentional brain defect/damage) study of humans who have sustained brain damage by accident, injury, illness, etc., as well as iatrogenic surgical "improvements" (e.g., amnesia patient "HM") - study the behavioral deficiencies of people after damage and relate the deficit to the function of the part(s) of brain destroyed.

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lesion due to genetic mutation:

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(a. Unintentional brain defect/damage) - human: hundreds of disorders that are due entirely or partially due to a mutation can be studied - entirely: e.g., trisomy (Down Syndrome), PKU, Fragile X, etc. (all produced mental retardation) -partially: "risk genes" are often polymorphic such that multiple alleles are commonly found in the population. Presence of a particular allele or combinations of alleles may be associated with increased risk of a disorder - mouse: a. behavioral genetics: b. spontaneous mutations:

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behavioral genetics

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mouse-examine different strains of mice to identify differences in behavior: - do strains differ in some known aspect of brain chemistry? Selective breeding can isolate regions of a chromosome associate with a certain behavioral trait

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spontaneous mutations

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shiverer, weaver, reeler, stargazer etc. Describe phenotype and then try to identify what the animal's mutation is (what is its genotype) - other model species - Fruit fly (Drosophila), roundworm (C. elegans), zebra fish (Danio) - as with mice, the relationship between expression of a particular gene and the consequences for nervous system structure and behavior can be tested.

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Directed/Intentional lesions- methods--

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- knife cuts - destroy/disconnect fiber tracts - electrolytic/radiofrequency - destroy everything around electrode - aspiration - suction - neurotoxic: excitotoxins or other drugs that kill cells

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Directed/Intentional lesions- methods-- reversible

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- chemical: muscimol (GABA receptor agonist) or lidocaine (anesthetic) - brain cooling - Transcranial Magnetic Stimulation (TMS): humans - although this is technically "stimulation", the goal is to use magnetic fields to disrupt normal processing in the brain—to in effect create a reversible inactivation. - also used as treatment for depression

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- Behavioral consequences--(Directed/Intentional lesions- methods-- reversible)

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- need to be careful in the interpretation of lesions - damage may not be in desired area, or, another damaged area could be the real target - poor performance may be due to many indirect factors, not just those ascribed to lesioned area. [PROPER CONTROLS?]

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2. Create mutations

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(b. Directed/Intentional --lesions)- use chemicals or irradiation to induce random mutations in genes. - study effects of damage (phenotype) and then try to identify what gene(s) were mutated - Targeted mutations

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- Targeted mutations

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(b. Directed/Intentional --lesions) create knockout mice with a mutation in a known gene. - this is opposite of random mutations where you know the effect but not the mutation. Here, you create the mutation and ask what is the effect?

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Prevent normal function (in vivo or in vitro)

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(b. Directed/Intentional --lesions) - drugs: use agonists/antagonists to stimulate or inhibit normal activity. - antisense oligonucleotides: prevent translation of protein - RNAi - use "interfering" RNAs to silence specific genes.

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Brain stimulation/infusion-a. stimulation

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- stimulate parts of brain with an electrode. - classic studies done by Penfield in the 1960's - newer methods: Deep Brain Stimulation (DBS) - implant permanent electrodes into the brain that can be activated by a stimulator - used increasingly to treat a variety of disorders (such as depression), although how it works is still basically unknown

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Brain stimulation/infusion-b. infusion:

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supply a drug/hormone etc into a particular brain region through a permanent cannula (tube) attached to the skull.

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1. in vivo

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(Brain Activity a. neurophysiology: electrical recording of brain activity) recording from a live animal

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intracellular

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(1. in vivo) microelectrode impaled into a single cell - animal must be immobile (usually anesthetized). Can record action potentials.

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extracellular

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(1. in vivo) microelectrode placed into CSF - record voltage changes occurring from adjacent neuron(s) activity

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2. in vitro

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record from a brain slice preparation

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b. Immediate Early Genes

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(Brain Activity) genes that are activated very rapidly when a cell (neuron) receives a signal: for example, c-fos gene that produces the Fos protein. - used to map the neural pathway for the response to a given stimulus.

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c. 2-deoxyglucose (2-DG)

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(Brain Activity) similar to PET, except that this is done on brain sections from animals

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d. Ca++ imaging

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(Brain Activity) involves chemically linking a molecule that can bind Ca++ ions to a molecule with fluorescent properties: e.g., fura-2. Increased fluorescence means increased influx of calcium, which means greater activity.

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EEG (electroencephalography)

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Older method to record brain activity which is still useful to diagnose certain neurological problems.

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PET scan

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- Subject is injected with a radioactive version of a sugar. Active cells use more sugar and a scanner finds areas that are most radioactive, indicative of areas being used the most - can also be used to find disturbed areas (lesions, tumors), psychological disorders (dopamine hyperactivity), and to localize brain regions that are engaged during different behaviors or cognitive processes.

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functional MRI (fMRI)

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technique that enables brain activity to be assessed by measuring increases in blood flow to active areas of the brain. Advantages over PET: - nothing has to be injected - structural and functional image in same image - better spatial resolution - monitors change in real time (unlike PET, which takes minutes).

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MEG (magnetoencephalography)

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- MEG is a direct measure of brain function, unlike functional measures such as fMRI, PET and SPECT that are secondary measures of brain function that reflect brain metabolism - measures magnetic fields generated by electrical impulses in axons - high temporal and spatial resolution -requires sensitive instrumentation to eliminate environmental magnetic interference and detect minute magnetic fields generated by axons

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