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PSYC 207 (7)


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University of British Columbia
PSYC 207
Michael Souza

Brain Activity 9/14/2012 12:06:00 PM IMAGING BRAIN ACTIVITY •Electrical Recording: -detect changes in the electrical activity of neurons •Brain stimulation: -Induce changes in electrical activity of brain •X-ray Imaging: -Sensitive to density of different parts of the brain, ventricles, nuclei, and pathways •Dynamic imaging: -Record and manipulate ongoing changes in brain activity, including electrical activity of cells, biochemical events, difference in glucose consumption, and flow of blood to various regions RECORDING THE BRAIN’S ELECTRICAL ACTIVITY •Activity of nerve cells has an electrochemical basis (Can be recorded with instruments sensitive to small electrical activity changes) Single-Cell Recording *How does each neuron decode the sensory signals you receive from the world, create what you experience as reality, and allow you to interact with reality? Electrode inserted directly into animal’s brain, adjacent to single neuron Neuron’s electrical activity recorded on a computer Supply info about activity of particular neuron *Most experiments must be done on nonhuman animals (Place electrodes directly on brain tissue) -Brain surgeons permitted access to research Experiments: -Cats & Primates: vision (have excellent vision) -Barn own: auditory -Rats: spatial behavior -Primates: reaching movements •Sensations and experiences are conveyed in the form of action potentials -When observing brain activity, actually measuring action potential over period of time The neuronal code -Neurons exhibit many firing patterns in different animal species -Some discharge @ a rate, seems unrelated to behavior -Others fire in association with observable behavior -Annual event, rhythmical discharge, or spontaneous -James Ranck: notice that action potential had relation to rat behavior -Incorrect theory: action potentials in different neurons might be units of perceived image (like in a photograph, pixels produce the photo) *Representing sensory events: -Time code: presence of an event is signaled by neural firing -Event code: a given neuron’s firing might signal change -Frequency code: intensity of an event, represented by rapidity of cell firing -Bimodal information: neurons that encode this way have a “resting” state characterized by moderate activity, increase in activity = one signal, decrease in activity=opposite/other signal Levels of Neural Processing •Anatomy of brain: suggest to researchers that it must use codes to represent information -Changing numbers of cells: visual information must be transmitted as a code rather than an image •Visual cortex: takes information encoded as dots and translates into visual experience Overview of Nervous System Structure and Function 9/14/2012 12:06:00 PM The Spinal Cord •Spinal-Cord Structure and Spinal Nerves -"Tube of nerves" encased inside ring-like bony vertebrae, dermatomes "skin cuts" •8 Cervical (forelimbs) •12 Thoracic (trunk) •5 Lumbar (hind limbs) •5 Sacral -Each dermatome connected by SNS nerve fibers to the body (including organs and musculature within that dermatome) -Afferent fibers that enter dorsal (posterior in humans) part of spinal cord are called dorsal roots *BRING information from sensory receptors (sensory) -Efferent fibers leaving the ventral (anterior in humans) part are called ventral roots *CARRY information from spinal cord to muscles (motor) -Collateral branches of sensory neurons may cross to other side and influence motor neurons there -Outer spinal cord: white matter -Inner spinal cord: gray matter •Spinal-Cord Function and the Spinal Nerves -François Magendie: Damage... •Dorsal roots: loss of sensation •Ventral roots: loss of movement -Bell hotly disputed, but was proved incorrect, give rise to Bell-Magendie Law -Charles Sherrington: spinal cord retains many functions even after separation from brain •Paraplegia/Quadriplegia: disability of bodies due to spinal cord injuries -Fibers in spinal tracts may regrow in some vertebrates but NOT adult mammals •New growth prevented by inhibitory molecules or scarring -Reflexes -Flexion/Extension •Pain/Temperature fibers: smaller •Touch/muscle sense: larger •Connections between Central and Somatic Nervous Systems -Controlled by CNS -Spinal cord oversees spinal nerves, brain oversees 12 pairs of cranial nerves •Autonomic Nervous System Connections -ANS regulates internal organs and glands by connections through SNS- >CNS -Must keep working during sleep •Sympathetic: "fight or flight" •Arousing sympathetic fibers connect to chain of ganglia near spinal cord •Activation starts in thoracic and lumbar regions •Parasympathetic: "rest and digest" •Calming parasympathetic fibers connect to individual ganglia near target organs (but do not directly control) •3 cranial nerves: 1. Vagus: calming of internal organs 2. Facial: salivation 3. Oculo
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