Introduction to cognitive neuroscience

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Janelle Leboutillier

Introduction to Cognitive Neuroscience Introduction: CNS: o Forebrain, Midbrian, Hindbrian, Brain Stem Brain Stem: Includes the midbrain, pons, and medualla from the top of the spinal cord to the diencephalon (subcortical part of the brain) Diencephalon: Thalamus, Hypothalamus control the pituitary gland. Cerebellum: Controls motor functions, coordination, learning and balance. Ventricles: Remnants of the neural tube from neural development and hold the cerebral spinal fluid. Function is unknown but they serve as important landmarks in the PET scan, MRI scan ect. Basal Ganglia: Extremely complicated circuits that are similar to gates that start and stop activity Motor (think Parkinsons Disease problems initiating movement) and Cognitive. Microscopic Anatomy of the Brain: o Shows that there are different types of neurons present in different regions of the brain. The concentration is not uniform. o Cortex: Made up of grey matter that have a high concentration of neurons that are organized in distinct layers. Layer 4: input layer Layers 5 and 6: Output Layer The layers differ in different cortical regions. a. Neuroscience is a biomedical field of study that focuses on animal nervous systems at a fairly fundamental level (Reductionism end of the equation) whereas cognitive psychology is a discipline rooted in the long- standing interest of natural philosophers and psychologists in understanding human mental processes. b. Cognition or the faculty of knowing is considered a largely human faculty and to me, cognition is the ability to be consciously aware of ones actions, thoughts, emotions, and external stimuli. Cognition refers to actions that require problem solving and complex thought rather than those brain processes and behaviors that involve automatic reflexes. c. Cognitive neuroscience is not the best definition, but this course overviews high-end function. d. HISTORY: i. Late 1800s: Psychology began and was finally considered to be a science able to test empirically though experimentation. 1. Measurement: Psychophysics ii. Introspection to Behaviorism to Cognitive 1. Introspection limited 2. Behaviorism: Watson (Behavior is governed by reward Could take anyone and turn them into anything), Skinner (operant conditioning), Thorndike 3. Cognition 2.Why is cognitive neuroscience as a field still something of a mess compared to say physics, chemistry or even neurobiology? a. To begin, let us define cognitive neuroscience as the convergence of cognitive psychology and neuroscience to describe higher order brain functions and associated behaviors on the molecular and cellular level. Cognitive neuroscience is still something of a mess due to the fact that not only are we examining humans we are attempting to study outcomes that vary from one individual to the next. Unlike in a physics lab or chemistry experiment, the outcomes are rarely predictable and describing something like emotion is much less concrete and quantitative than say, a compounds heat of formation. Notes on Chapter 1: The Human Nervous System Cellular Components of the Nervous System: o The cells of the nervous system can be divided into two broad categories: Nerve Cells aka. Neurons: Specialized cells that generate and propagate electrical signals over distances that can be up to a meter or more in humans. Information transmitted in the form of these electrical signals is the basis of sensation, behavior, and physiological processes in all animals it is also the source of the cognitive abilities that reach their most complex expression in human beings. Neuroglial Cells: Supporting Cells or Glia. These cells comprise a variety of cell types that support and hold together the nervous tissue. Unlike neurons, they are not capable for electrical signaling but they have a crucial effect on the speed at which a neurons electrical signals travel. o Similarities to other cells: Cell Body: containing nucleus and organelles such as the ER, ribosomes, Golgi Apparatus, and Mitochondria. o Distinguishing Features: aka. Specialization for intercellular Communication Axon: Conveys information in the form of electrical impulses over distances that range from millimeters to meters in the case of axons that extend from the spinal cord to the arms and legs. Dendrites: Receive information from the axonal endings arising from other nerve cells. Nerve Cells and their Signaling Functions: NEED TO REVIEW o Neurotransmitters: molecules that are released from synapses and change the electrical potential across the membrane of the neuron they contact. Many nerve cells converge on a single target neuron and the terminal axon branches extend to a number of other target neurons. o Axon Hillock: A region at which the convergent input is integrated and if there is enough excitatory stimuli the target neuron will carry the signal forward to its own target cells. o Action Potential: A self-regenerating wave of electrical activity that propagates from its point of initiation at the Axon Hillock to the synaptic endings at the axons terminus. o Ion channels/ion pumps are specialized proteins on axonal membranes that maintain an ionic gradient at a metabolic cost. o Dendrites: provide the major site for the synaptic contacts from other nerve cells. The number of inputs that a particular neuron receives is generally proportional to the complexity of its dendritic arborization: nerve cells that lack dendrites are innervated by just one or a few other nerve cells, whereas those with increasingly elaborate dendrites are contacted by a commensurately larger number of other neurons. o Synaptic Cleft: Where communication between the presynaptic terminal and postsynaptic specialization occurs. Neurotransmitter molecules that are released from synaptic vesicles, or secretory organelles in the presynaptic terminal, bind to neurotransmitter receptors which are proteins embedded in the membrane of the postsynaptic specialization. The binding of neurotransmitters to receptors opens or closes the ion channels in the postsynaptic membrane, which changes its membrane potential. o Step-By-Step: 1. Transmitter is synthesized and then stored in vesicles. 2. An Action potential invades the presynaptic terminal 3. Depolarization of presynaptic terminal causes opening of voltage-gates Ca2+ channels. 4. Influx of Ca2+ through channels Ca2+ causes vesicles to fuse with presynaptic membrane 6. Transmitter is released into synaptic cleft via Exocytosis. 7. Transmitter bind to receptor molecules in the postsynaptic membrane. 8. Opening or closing of postsynaptic channels. 9. Postsynaptic current causes excitatory or inhibitory postsynaptic potential that changes the excitability of the postsynaptic cell. 10. Retrieval of vesicular membrane from plasma membrane. Neural Circuits: Groups of interconnected neurons o Afferent Neurons: Nerve cells that carry information centrally or toward the central nervous system (Brain or Spinal Chord) or toward any neural processing structure. o Efferent Neurons: Nerve cells that carry information peripherally or away from the central nervous system. o Interneurons: Nerve cells that participate only in the local aspects of a circuit as in many components of the brain. o Spinal Reflex ARC: Knee-Jerk Response 1. Afferent (toward the CNS) limp of the reflex arc comprised of bipolar sensory neurons whose cell bodies are located in the dorsal root ganglia of the spinal cord and whose axons end in the special sensory receptors in the re
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