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15 Cards in this Set
- Front
- Back
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Brain Imaging Techniques: fMRI
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based on increase in blood flow to the local vasculature that accompanies neural activity in the brain (high activity)
noninvasive measurement that can record signals from all regions of the brain blood oxygenation is closely related to neural activity BUT not a direct measure of it used to located tumors (different energy responses) has emerged in the last 15 years |
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visualizing empathy
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psychopaths are thought to have disfunction in the brain that controls pain
people who never physically felt pain can't relate to someone else's pain experiments show that you don't have to feel pain to have an empathetic neural response |
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measuring electrical signals in neurons
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need to measure the membrane potential (voltage) across plasma membrane
negative resting potential in relation to outside neurons are unique cells because they are excitable |
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the squid giant axon
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1 mm in diameter (100-1000x larger than mammalian axons)
used for a lot of experimental research for electrical measurements 1st recorded intracellular action potentials from nerve cells 1st experimental measurement of ion currents that produce action potentials explore cytoplasm ionic composition large synapses that have been valuable in understanding the fundamental mechanisms of synaptic transmission giant axons evolved to enhance survival simple neural circuit that activates contraction of mantle muscle (jet propulsion effect that allows squid to move away from predators at remarkably fast speed) |
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genetic approaches in neuroscience
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model systems (worms, flies): rapid unbiased genetic approaches
genetic approaches in mice: - knock-out animals: delete a specific gene of interest - knock-in animals: replace a specific gene of interest with an exogenous gene (outside organism) - transgenic animals: insert copy of exogenous gene into genome under control of regulatory elements of specific gene of interest - tools: labeling select neurons, identifying neural networks, activating neurons within a network, inhibiting neurons within a network |
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model organisms
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fruitfly Drosophila melanogaster:
mouse Mus musculus nematode Caenorhabditis elegans ability to do genetic analysis and manipulation in each of these species majority of genes in genomes of these animals are expressed in the developing and adult brain |
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gene number in model systems
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human: 20,000
mouse: 25,000 D. rerio (zebrafish): 24,000 D. melanogaster (fruit fly): 15,000 C. elegans (nematode): 19,000 |
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the nematode C. elegans
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have a very rapid life cycle (less than 2 days)
- reaches adulthood in ~40 hours - rapid genetics, translucent body, powerful screens each adult hermaphrodite worm has only 959 cells (302 are neurons) - each neuron has been ablated and the resulting behavioral phenotype has been established - using EM, each neural circuit has been mapped - can also examine behavior (very simple behavioral response; move away if stimulated) tradeoff: not as complex; don't understand neural functions |
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the mouse Mus Musculus
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mammalian model system (closer to that of humans)
established genetic techniques long history of study of behavior, anatomy, and development expensive to study in costs and time |
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genetic methods in mice
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gene disruption or "knock-outs_ test the neccesity of a specific gene
with homologous recombination, insert some other gene transgenics: insertion of exogenous gene/transgene |
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transgenic uses
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in C. elegans, can be used to identify specific cell types in vivo
- also localization of a protein of interest within a cell - ODR10: odorant receptor gene in nematodes - green fluorescent protein (GFP): reporter gene that emits intense green light when certain wavelengths of light are used to excite it |
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genetic approaches to study neural circuits
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neurons do not work in isolation; they are components of intricate and complex neural circuits
major goal in neuroscience: identify function of circuits new genetic approaches are being developed to: - label neurons in a circuit - identify neurons that are synaptically coupled - define the role of a specific neuron within a circuit |
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brainbrow: individual neurons labeled
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in mice, transgenic techniques, combined with fluorescent reporters have been used to map neural circuits
- red, yellow, blue; change amount of each: different dosages of different colors to represent individual neurons trace each process separately |
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calcium imaging
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genetically encoded calcium sensor
green fluorescent protein fused to calcium binding protein visualize activity of neuron based on response of calcium sensors no voltage/currents necessary |
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optogenics
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using light to control activity
channels open in response to light: neurons are excited or inhibited photo-activatable ion channels/pumps are used to excite or inhibit specific neurons within a circuit can test role of specific neuron within circuit channelrhodopsin (ChR2): activate neurons halorhodposin (NpHR): inhibit neurons genetically encoded neuronal inhibitor in neurons that activate muscles needed for motility |
