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MIT 9 01 - Study Notes

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Motor control: reflexes9.01 Review for the first half of the semester See also: flashCube definition file, classes 1-21. [Bracketed items below were not discussed in lectures, or will be discussed after the midterm more extensively.] Goals of scientists trying to explain mind and behavior in brain terms: (Exact dates are not essential; see the flashCube items) Stimulus→ Response models from Descartes onward: Pursuing the first type of goal of explaining behavior in terms of underlying circuits. Descartes (1662): reflex arc LaMettrie (1748): The soul is an enlightened machine. Human is unique species only in complexity of reflex connections. Bell (1811), Magendie (1822): the "law of roots". Sechenov (1866): reflexology as a philosophy of human and animal nature. Pavlov (1900): conditional (conditioned) reflexes; influenced development of American S-R psychology, with emphasis on learning. Ramon y Cajal: Used Golgi stain to study anatomy of CNS; the neuron is the basic unit of the nervous system; showed connections between neurons from input to output. Sherrington: synapses (named by him), excitatory and inhibitory; spinal reflex integration. Donald MacKay: "The logical indeterminacy of free choice"; even with the assumption of physiological cause-effect relationships underlying all behavior, a person's responsibility for choices remains. Second type of goal (localization of function): Phrenology's extremes: Franz Joseph Gall (1825); collecting anecdotal stories as method. Paul Broca (1861): 2 cases of disturbed speech (aphasia), with lesions in lower part of left frontal lobe. This region became known as Broca's area. Fritsch and Hitzig (1870): Defined "motor cortex" with electrical stimulation of dog brain, as the region where movements could be elicited with the weakest currents.. Betz (1874): Discovered giant pyramidal cells in layer 5 of motor cortex, using Nissl stain for cell bodies. Carl Wernicke (1874): Discovered a second area for language, located in temporal lobe; proposed a model for speech generation involving connections from this area (now called Wernicke's area) and Broca's area, later promoted by Boston behavioral neurologist Norman Geschwind in 1960’s – 1980’s. Pierre Flourens (1824): Experimenter who found evidence for general localization of function but not for the modular subdivisions claimed by phrenologists. (Experiments on pigeon brain described in class: defined general functions of hindbrain, cerebellum, optic lobes, forebrain.) Goltz (1876): Experiments on dogs; conclusions similar to those of Flourens (considered "anti-localization" in nature). Critique: Inadequate analysis of behavior. Karl Lashley (1920s, 1930s): tried to localize the engram (the physical changes underlying a memory) for maze learning in rats. Presented evidence for "equipotentiality" and "mass action" of neocortex, no longer generally accepted after more recent studies. What is specifically localized in brain? Not psychological functions, but only physiological processes in a structural substrate. 9.01 - Neuroscience & BehaviorFall 2003Massachusetts Institute of TechnologyInstructor: Professor Gerald SchneiderD.M. MacKay: Do brains think? This is a poor question; "...if we want to use language consistently, we cannot say that brains think or decide. Brains do those physical things appropriate in their own logical dimensions as correlates of what people do when deciding, thinking, feeling, hoping, fearing, believing, and so forth." (from "A mind's eye view of the brain.") The third type of goal: finding mere correlations of brain and behavioral events. Example 1: Using EEG to define states of sleep and arousal, in terms of brain states rather than localized functions. Example 2: Modern studies of human brain using functional imaging, to define brain modules for specific functions. (Dangers: Temptation to return to phrenology-like maps; sophisticated knowledge of both anatomy and of information flow underlying behavioral functions will be needed.) Modern "subsystems" analysis: Use of information flow logic, and considering the brain as a "massively parallel" computer. Difficult for such models to take account of 1) modulating influence of diffuse connections and changes in chemical environment; 2) the complexity of single neurons, with generation of spontaneous rhythmic changes. ---------------------------------------------------------------------------------- Properties of neurons: Primitive cellular mechanisms: irritability, conduction, movement (contractions via contractile proteins), secretion, membrane specializations for irritability (transducer mechanisms), endogenous activity. Receptor potential in specialized epithelial cells (receptor cells) → generator potential in primary sensory neurons Graded response Decremental conduction Regions of a neuron for reception, conduction, and transmission. Dendrites vs. axon and axon telodendria All-or-none response, non-decremental conduction (action potential) Boutons (boutons termineaux = end buttons, or endfeet) EPSP vs. IPSP Spatial summation, temporal summation Axon hillock Resting potential Semipermeable membrane Sodium-potassium pump Three types of transducer mechanism (chemo-, mechano-, and photoreceptors) Myelin: role of oligodendrocytes (CNS) and Schwann cells (PNS) (these are two types of glial cells, or glia) Nodes of Ranvier Saltatory conduction Synapse and bouton (not the same concept) Oxytocin and the milk ejection reflex (a neuro-humoral reflex) Axo-axonal synapses and presynaptic inhibition or facilitation. Reciprocal synapses Serial synapses Primary sensory neurons of the nasal epithelium [Primary sensory neurons of the taste system] Primary sensory neurons of the dorsal root ganglia 2Endogenous activity and pacemaker loci in cell membranes [Entrainment of an endogenous rhythm (oscillator)] Evolution of Nervous Systems: Major types of neurons: primary sensory, secondary sensory, interneuron, motor neuron. Peripheral ganglia (dorsal root vs. autonomic) Notochord Amphioxus vs. other chordates: the shape of the neural tube Cranial nerves vs spinal nerves Head receptors and expansion of regions of the neural tube in evolution: What probably caused the earliest expansion of the endbrain (telencephalon)? Can you give examples of what probably caused later expansions? Introduction to CNS as a system of interconnected cells: Dermatome Segmental conduction vs.


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