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PSYC 2220 (44)
Chapter 1

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York University
PSYC 2220
Richard Murray

Sensation + Perception I Chapter 1 Chapter 1 : Introduction Neural Connections Santiago Ramon Y Cajal - organization of neurons - drawings of neurons + their connections - neurons do not touch, they are separate cells with tiny gaps Sir Charles Sherrington - tiny gap = synapse - demonstrated: speed of neural transmission decreases at synapse SYNAPSE: the junction between neurons that permits information transfer greek "to fasten together" - people initially thought that some sort of electrical wave traveled across synapse from one neuron to the next Otto Lowei - proposed: that something CHEMICAL instead of ELECTRICAL is at work at the SYNAPSE - demonstrated: neurons communicate with one another by releasing chemicals called neurotransmitters. because: some neurons increase response of next neuron (excitatory) while others decrease the response of the next neuron (inhibitory) NEUROTRANSMITTER: chemical substance used in neural communication - many diff kinds of neurotrans; individual eurons are selective of which neurotrans excite them and which inhibit psychoactive drugs (amphetamines): increase of decrease the effectiveness of diff neurotrans Neural Firing: The Action Potential Sir Alan Hodgkin + Sir Andrew Huxely - conducted experiments in which they isolated a single neuron from the squid and test how the nerve impulse travels along the axon - pierced axons with electrodes to measure voltage + inject diff. chemicals inside - learned: neural firing = electrochemical - voltage increases along axon: caused by changes in the membrane of the neuron that permit (Na+) ions to rush into the axon from outside. then the membrane quickly changes again in a way that pushes (K+) ions outside the axon, restoring the neuron to its initial resting voltage. - process occurs in 1/1000th of a second every time neuron fires - squids: have giant neurons (1 mm thick) (electroencephalography) EEG: measures electrical activity from population of many neurons in the brain by placing electrodes on the scalp. - doesnt allow researchers to leanr what individual neurons are doing/ to pinpoint the exact area of neural activity. - can be used to roughly localize whole populations of neurons and to measure their activities with temporal accuracy - record MANY responses to a stimulus, then AVERAGE the resulting averaged waveform: event related potential (ERP) ERP: a measure of electrical activity from a subpopulation of neurons in response to particular stimuli that requires averaging many EEG recordings. similar to EEG, measures changes in magnetic activity across populations of many neurons in the brain - neurons make changes to their local magnetic fields in addition to small electrical changes - researchers use SQUIDS (super conducting interference devices) to measure these tiny magnetic fields, but they are very expensive and less common than EEG devices Sensation + Perception I
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