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CNS sensory and motor (Lecture 1).docx

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McGill University
PHGY 209
Erik Cook

CNS sensory and motor (Lecture 1): Reading List: will be tested on the final. • Chapter 6 (Structure of the nervous system): Section D, but skipAutonomic NS • Chapter 7 (Sensory physiology) • Chapter 8 (Consciousness, the brain, and behavior) • Chapter 10 (Control of movement) Structure and function of the central nervous system (idea evolving in the late 1800s) • The brain is not a bag of cells. It is organized. o You can understand the liver’s function by studying a single liver cell. o But you cannot only study a single neuron and describe its physiological and molecular components to understand the functioning of the brain. • The interactions through the trillions of synaptic contacts provide our thoughts. • All neurons are the same, but it’s how they’re connected that makes each one of us slightly different. • Here is a map of how the brain worked, developed by neuroscientists in the late 1800s. Not quite accurate, but good concept. o Self-esteem lobe(?) at the top (will be on the final) o Tune area near the eye: always an interesting question why above the eye and not the ear o Hope area We got to understand the structure and the function relationship through the unfortunate occurrence of brain injuries (100,000 injuries for the past 10,000 years). • Phineas Gage (1823-1860): worker on the railroad in Vermont. Drill holes in rock, pack dynamite down holes, his job = camping iron and hamming it down. The explosives ignited while he was digging, yet he survived, so the physicians studied him closely. o Effects: Loss of vision in one eye. Personality change. Management skills lost, which made him unable to maintain his job; he, in fact, joined the circus. Died 12 years later. o Using modern techniques, scientists tried to diagnose what the brain injury was and tried to link it back to the effects on behaviour. o The iron bar is found in the Harvard Medical School library. In late 1800s, if the brain has a map, maybe we can drill holes and get rid of the “bad” parts. • Pre-frontal lobotomy: Dr. Burhat took 6 schizophrenic patients and drilled holes in their heads. As a result, two of them died, but four got better, yet their personalities changed making their behaviour less severe. • By the 1830s, Dr. Menoz took out or damaged the pre-frontal areas from psychiatric patients around the eyes, whose state became less severe. Scientists started thinking this may cure mental illness. (?) • Dr. Walter Freeman took lobotomy and structure-function idea too far. Infected a thin device and popped it through a thin scar above the eye, wiggled it around and took it out. Did 25 in one day on one of his patient, which was barbaric, since this wasn’t treating the symptoms, but damaged the brain instead. o In fact, there isn’t just one place in the brain that goes bad, in mental illness, it’s distributed, which makes it difficult to treat. How do we observe the brain in action? How do we learn about how the NS works without damaging the brain? • Each cubic millimeter of brain tissue contains up to 100,000 neurons and 100 million synapses (since each neuron communicates with 10,000 other neurons). o Slide on the right shows neurons in a genetically modified mouse. We see the cell bodies, dendrites, etc. o Slide on the left shows neurons, each expressed in a different colour.Above the coloured region, we see a section of densely packed dendrites, where all synapses take place. Clearly, due to the density, it is almost impossible to measure and study each neuron individually. Single neuron electrophysiology consist in putting tiny metal electrodes/antennas right up next to neurons and listen toAPs generated by them. • The noise heard “pa-pa-pa-paa!” is, in the fact, the neural code. • We are interested in knowing what these neurons say to each other. It is still not perfectly clear. We know that there are neurons in the …cortex that are selectively activated when you look at a face, even if you never saw this person before. • We know this thanks to studies using electrical physiology and animal models, like monkey. • On the diagram showing the “Recording in area MT of
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