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The Neural Basis of Speech and Language

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The Neural Basis of Speech and Language © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CHAPTER © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC The NeuralNOT FOR SALE Basis OR DISTRIBUTION of NOT FOR SALE OR DISTRIBUTION Speech and Language 2 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Introduction © Jones & BartlettThis section Learning, gives the LLC reader a brief overview ©of Joneswhat takes & Bartlett place neurally Learning, when LLCa per- son starts a conversation by saying, “Hello. How are you? How was your vacation NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION trip?” to another individual whom the person meets on the street. Simply put, the steps involved would be as follows: 1. Basic vision: seeing a person on the street 2. Visual perception: recognizing the person as someone the speaker knows 3. Cognition:© theJones desire & to Bartlett speak with Learning, this person LLC about a trip that the speaker© Jones may & Bartlett Learning, LLC want to takeNOT in FORthe future SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4. Language: searching for the right sounds, syllables, words, and sentences, all pre- sented in the right order, with meaning properly related to the greeting and the subject matter, to be expressed with a positive attitude © Jones5. Motor & Bartlettprogramming Learning, or planning: LLC readying the speech© mechanism Jones & Bartlettjust prior Learning, to LLC NOT speakingFOR SALE so that OR the DISTRIBUTION production is correct NOT FOR SALE OR DISTRIBUTION 6. Motor production or execution: speaking 7. Feedback: (1) from self: hearing and feeling oneself speak and then using that information as a guide for further appropriate speaking (e.g., usually we know when something said does not sound right, and we either repeat it or put it into © Jones & Bartlettdifferent Learning, words); LLC (2) from others: looking© at Jones and listening & Bartlett to another Learning, person LLC speak NOT FOR SALE ORto helpDISTRIBUTION determine what to say next (e.g.,NOT responding FOR SALE to questions OR DISTRIBUTION from someone who looks and sounds angry as opposed to someone who does not). Responding to auditory feedback from oneself or from others involves the hearing of sound (basic hearing). Recognizing that sound as speech and not some other envi- ronmental noise© is Jones auditory & perception.Bartlett Learning, Understanding LLC what is said is language© Jones com- & Bartlett Learning, LLC prehension. All NOTof the FORsteps SALEmentioned OR above,DISTRIBUTION with the exception of cognition,NOT will FOR be SALE OR DISTRIBUTION commented on in the neural outline that follows. The neural basis for cognition (think- ing and behavior) probably involves bilateral cortical areas (especially the frontal lobes) as the prime movers, assisted by subcortical and brainstem systems. Because of the wide- spread neural activity, localization of cognitive functions is quite difficult. However, cognition© Jones and & Bartlett defects of Learning, cognition areLLC noted in other parts of© this Jones manuscript & Bartlett (e.g., Learning,the LLC chaptersNOT FOR dealing SALE with OR right DISTRIBUTION hemisphere damage, dementia, andNOT traumatic FOR SALEbrain injury). OR DISTRIBUTION The information in the following outline has been gleaned from Bhatnagar (2008), Duffy (2005), Kent (1997), Webb and Adler (2008), Webster (1999), and Zemlin (1998); the organization of the outline mostly follows that of Webb and Adler, with © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 9 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 74738_CH02_FINAL.indd 9 1/30/12 2:55 PM © Jones & 10Bartlett Chapter Learning, 2 The LLCNeural Basis of Speech and Language© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION details from Bhatnagar. The reader is referred to these sources for further elaboration of any of the topics mentioned in the outline. In a number of places within the outline, examples are given of the speech and/or language problem that can occur if there is damage to certain por- tions of the neural system. Most of the speech and/or language problems given as examples © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC are mentioned further in other parts of this text. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Definitions The Neuron © JonesThe neuron,& Bartlett or nerve Learning, cell, consists LLC of a cell body, dendrites,© Jones and an &axon Bartlett (Figure Learning, 2.1). The cell LLC NOT bodyFOR (intracellular) SALE OR DISTRIBUTIONcontains a high concentration of potassiumNOT and FOR low SALE concentrations OR DISTRIBUTION of sodium and chloride, compared to the fluids outside the cell body (extracellular). The concentrations Dendrites © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cell Body © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Axon © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Motor EndNOT Plate FOR SALE OR DISTRIBUTION Muscle © Jones & BartlettFIGURE Learning, 2.1 A neuron, LLC with its cell body, dendrites, and axon,© Jones synapsing & at Bartlett the myoneural Learning, junction of the LLC muscle. © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 74738_CH02_FINAL.indd 10 1/30/12 2:56 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, DefinitionsLLC 11 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION are reversed in the extracellular fluids, thus creating an electrical current for transmission of neural impulses. Dendrites are numerous short projections that carry neural impulses to the cell body. The axon carries neural impulses away from the cell body. The neuron can trans- mit neural impulses to other neurons, glands, or muscles. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC The juncture at which neural impulses are transmitted is called a synapse; neurochemical transmitters aid NOTin moving FOR the SALE neural OR impulses DISTRIBUTION along. Myelin, a fatty sheath thatNOT insulates FOR SALE the OR DISTRIBUTION larger axons, is said to increase the speed of neural transmission and also to reduce interfer- ence with the neural message. There may be about 100 billion neurons in the human nervous system. Axons can produce anywhere from 1000 to 10,000 synapses, and their cell bodies and© Jones dendrites & Bartlettreceive neural Learning, data from LLC about 1000 other neurons.© Jones As a result,& Bartlett the number Learning, of LLC synapsesNOT FOR occurring SALE in OR the DISTRIBUTION brain may be about 100 trillion. NOT FOR SALE OR DISTRIBUTION Nerve Cell Structure Cell Body (also called perikaryon, or soma) © Jones & Bartlett1. Protoplasm Learning, refers LLC to the nucleus and cytoplasm.© Jones & Bartlett Learning, LLC NOT FOR SALE2. OR Cytoplasm DISTRIBUTION is composed of a watery substanceNOT FOR and proteinSALE ORmolecules, DISTRIBUTION and is enclosed within the cell membrane. Microscopic structures in cytoplasmic materials include the following: a. Neurofibrils (which tend to become tangled in Alzheimer disease) serve as channels for intracellular communication. b. Mitochondria© Jones contain & Bartlett enzymes Learning, involved with LLC cellular metabolic energy.© Jones & Bartlett Learning, LLC c. RibosomesNOT are FOR protein SALE granules OR DISTRIBUTION involved in the synthesis of RNA. NOT FOR SALE OR DISTRIBUTION d. Lysosomes contain enzymes that participate in intracellular digestion. e. Golgi complexes are responsible for protein secretion and transportation. Axons© Jones and & Dendrites Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT1. NerveFOR SALEfiber means OR DISTRIBUTION an axon and its covering sheath. NOT FOR SALE OR DISTRIBUTION 2. Axons are efferent (motor) structures that transmit information away from the cell body to other neurons. They depend on cytoplasmic proteins for survival. 3. Axon hillock refers to a cone-shaped region of the cell. Axons extend longer distances than dendrites. At their ends, they may branch into smaller multiple filaments, called © Jones & Bartletttelodendria, Learning, that LLC include synaptic knobs©, Jonesor end &in Bartletta terminal Learning, bouton (knob). LLC Both NOT FOR SALE ORtypes DISTRIBUTION of knobs contain neurotransmitters.NOT FOR SALE OR DISTRIBUTION 4. Dendrites are afferent (receptive) structures that transmit information to the cell body from other cells via synaptic sites. They tend to be short and have many branches. When they have spikes or spines, this increases the surface available for synapses with other nerve cells. Many© ofJones these spines& Bartlett atrophy Learning, from disuse LLC as part of typical maturation.© Jones One theory & Bartlett
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