Cognitive Science Chapter

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University of Toronto St. George
Chemical Engineering and Applied Chemistry
Nick Eyles

Cognitive Neuroscience Prof. Shomstein 1/15/08 Cognitive Neuroscience Cognition: Variety of higher mental processes (thinking, perceiving, imagining, speaking, acting, planning, etc.) Neuroscience Biological investigations of the brain Patient HM Case Study Epileptic in 20s in 1953 Seizures from age 10, uncontrollable Despite absence of epileptogenic activity, he received a bilateral medial temporal lobectomy. This stopped his seizures, but made it so he was unable to form new long-term memories. This is a selective memory deficit, not a perceptual/intellectual problem. He has normal short term memory, but Anterograde Amnesia (cant remember anything past surgery) HM does a tracing task: Draw a star while only looking at your hand in a mirror. Even though he cannot make new memories, each day he does it, he gradually improves. Procedural/Muscle memory is separate from memories of events in the past Questions in Cognitive Neuroscience How do biological systems work? Can the brain learn, or does it have dedicated parts? What happens when you take parts away? Localization Vs Antilocalization How does the brain work? Localization Parts of the brain are specific to certain functions 1/17/08 EEG measures brainwaves fMRI Study activity in physical brain (topographic) in millimeter resolution Early Conceptualizations of Mind Aristotle (384-322 BC) -Brain contains cooling fluid so it doesnt overheat Descartes (1620) Dualism -Pineal gland is where mind and body interact - Influences the body through ventricles Spinoza (1650s) Mind and body are the same, the mind is just at a higher level Dual aspect theory Gall and Spurzheim (1810) Create true-to-life diagram of the brain -35 areas with different functions -Believed that brain grows to accomodate functions -Anatomical personology -Localizationists Anti-Localizationist (1824) Florens -All sensations, all perceptions, and all volitions occupy the same seat in these cerebral organs. The faculty of sensation, percept, and volition is then essentially one faculty. He tested this by removing parts of birds brains, and then seeing them recover -Aggregate Field (mass action of brain) 1861 Broca Mr. Leborgne has a stroke in his frontal cortex. After this, all he could say was Tan (this is called aphasia). However, he could understand everything. Showed the Language Production is localized in the frontal cortex Wernicke (1876) Patient can say things, but cannot understand. Produces Nonsense 1870 Frisch and Hitzig Electric stimulation in dog to produce movement Early 1900s German Neuroanatomists -Brodmann, Nissl, Von Bonin, Bailey, Von Economo Others -Golgi, Cajal, Purkinje, Freud, von Helmholtz -Neuron Doctrine They all agree on some form of localization Golgi, believing in mass action, develops a stain to see neurons. He does not notice the Synapses Cajal saw the synapses, and shows that there is localization Sensory and Motor Maps Sir Henry Head sectioned branches of his own radial nerve (in the hand) and did experiments on sensory loss. Lashley: Mass Action Maze Learning with Rats Showed that lesions do not impair learning or performing tasks 20 Century: Localization Penfield and Rasmussen studied those undergoing surgery for seizures. Delivered electric shocks to the brain and showed that stimulating certain regions (the motor cortex) produces specific responses in the body Complex behaviors include many different areas Smaller processes are localized 1/22/08 Psychology story the black box -Goal is to measure behavior and study the mind Empiricists vs. Rationalists Rationalists meaning of life through right thinking about happiness/public good/etc. Empiricists knowledge/meaning through sensory experience Behaviorists try to understand the mind using stimuli/responses Demise of behaviorism Some behavior property of mind alone responds differently to the same output, I.E. optical illusions/apparent motion -Emphasis on built-in properties (mental events) -Internal representations, mental maps, and models -Newell and Simon -Chomsky states that language is formed in the brain Cognitive Neuroscience -How cerebral cortex is organized and functions -Hubel and Wiesel -Marr: Multiple levels of analysis, algorithm, implementation, and computation -requires appeal to biology: how everything is wired MRI created, cognitive neuroscience rises Chapter 2 Cajals Neuron Doctrine -Brain contains individual cells with small gaps between them -Connectional specificity: there are specific pathways that cells attach to to perform certain functions -Dynamic polarization parts of neuron made to send information, parts made to receive Neurons: Like other cells, but some specific properties Glia: Non-neural cells playing supportive function 100-1,000 billion neurons in the brain each makes ~1000 connections on average What do neurons do with this information? 1. Receive information/collect information 2. Process information 3. Produce output 4. Transmit information over a distance Neurons Soma Cell Body Metabolic Machinery: Nucleus, ribosomes, mitochondria, Golgi apparatus. Enclosed in membrane, suspended in cytoplasm Dendrite (afferent) -Receives input from neurons at synapses (postsynaptic) -Treelike may be large arbors (Purkinje) or small (thalamus) -Spiny endings Axon (efferent) -Before synapse (presynaptic) -communicates output of neuron -connects to the soma at the Axon-Hillock -Insulated with myelin sheaths
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