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Jimmy Kimber LECOM – Seton Hill OMS1 Physiology Chapter 57: Cerebral Cortex, Intellectual Functions of the Brain, Learning and Memory Learning Objectives 1. Describe the 3 types of neurons in the cortex Granular Neurons (stellate): - Short axons - Function as interneurons that transmit over short distances - Some excitatory – glutmate, some inhibitory – GABA - High concentrations in sensory areas of cortex, and association areas Pyramidal and Fusiform Neurons: - Give rise to almost all output fibers from the cortex - Pyramidal are larger and more numerous - Pyramidal are the source of long, large nerve fibers that go to the spinal cord 2. Briefly summarize the function of each layer Layer IV – most of the incoming specific sensory signals Layer V – very large fibers to the brain stem and cord Layer VI – fibers to the thalamus Layers I, II, III – most of the intra-cortical association functions 3. What is the thalamocortical system? What are its implications regarding the relationship between its components The thalamocortical system is the thalamus and cortex together. The cortex operates in close association with the thalamus and can almost be considered both anatomically and functionally a unit with the thalamus. Relationship: When the thalamus is damaged along with the cortex, the loss of cerebral function is far greater than when the cortex alone is damaged because thalamic excitation is necessary for almost all cortical activity. 4. Know the locations of the major association areas (Figure 57-4) Jimmy Kimber LECOM – Seton Hill OMS1 5. What is the function of primary/secondary motor, sensory areas? Primary Sensory Areas: detect specific sensations – visual, auditory, or somatic – transmitted directly to the brain from the peripheral sensory organs Secondary Areas: located within a few centimeters of the primary areas, begin to analyze the meanings of the specific sensory signals such as – interpretation of shape/texture of an object, interpretation of color, light intensity, directions of lines and angles, and interpretations of the meanings of sound tones and sequence of tones in the auditory signals. 6. What are association areas? List the 3 most important Association Areas: large areas of the cerebral cortex that do not fit into the rigid categories of primary and secondary motor and sensory areas. These receive and analyze signals simultaneously from multiple regions of both motor and sensory cortices as well as subcortical structures. Most Important: parieto-occipitotemporal, prefrontal, limbic association areas 7. Where is the parieto-occipitotemporal association area? Describe its functional subunits Location: in the large parietal and occipital cortical space bounded by the somatosensory cortex anteriorly, visual cortex posteriorly, and the auditory cortex laterally Subunits: - Analysis for Spatial Coordinates of the Body: area receives visual sensory information for posterior occipital cortex and simultaneous somatosensory information from the anterior parietal cortex. From this information, it computes coordinates of visual, auditory, and body surroundings - Area for Language Comprehension: Wernicke’s area – behind the primary auditory cortex in the posterior part of the superior gyrus of the temporal lobe. - Reading - Area for Initial Processing of Visual Language: visual association area that feeds visual information conveyed by words read from a book into Wernicke’s area – angular gyrus area - Area for naming objects: In the most lateral portions of the anterior occipital lobe and posterior temporal lobe; names are learned through auditory input whereas physical natures are learned through visual input 8. Differentiate between Wernicke’s and Broca’s areas Wernicke’s Area: major area for language comprehension, located behind the primary auditory cortex in the superior gyrus of the temporal lobe Broca’s Area: provides neural circuitry for word formation; plans and motor patterns for expressing individual words or short phrases are initiated and executed here. 9. What is the function of the prefrontal association area? - Works with motor cortex to plan complex patterns and sequences Essential to carrying out “thought” processes Elaboration of thoughts – stores working memories Jimmy Kimber LECOM – Seton Hill OMS1 10. Where is the limbic association area and what is its role? Location: anterior pole of the temporal lobe, ventral portion of frontal lobe, and in cingulate gyrus (deep in the longitudinal fissure) Function: behavior, emotions, motivation 11. What is prosophenosia? What causes it? Prosophenosia – inability to recognize faces Cause: extensive damage on the medial undersides of both occipital lobes and along the medioventral surfaces of the temporal lobes 12. What is the importance of Wernicke’s Area? How is it related to handedness? Wernicke’s Area is the area of confluence of the different sensory interpretive areas: somatic, visual, and auditory – that meet in the posterior part of the superior temporal lobe. It is especially highly developed in the dominant side of the brain. This is the left side in almost all right-handed people. It is important in interpreting complicated meanings of different patterns of sensory experiences. 13. What is the angular gyrus? Why does its destruction cause dyslexia? Angular Gyrus – most inferior part of the posterior parietal lobe, lying immediately behind Wernicke’s Area. It fuses with the temporal lobe. Destruction of the Angular Gyrus with retention of Wernicke’s Area causes dyslexia because the person will still be able to interpret auditory experiences, but the stream of visual experiences passing into Wernicke’s area will be blocked. 14. Explain the concept of the dominant hemisphere and its reason for developing: Dominant Hemisphere - Speech and motor control areas are usually much more highly developed in one cerebral hemisphere than in the other. Cause: when we are born, the left posterior temporal lobe is slightly larger than the right. So, the mind directs thoughts to this region. Because of this, it is used to a greater extent than the right and begins to develop at a greater rate. 15. What is the importance of the corpus callosum? The corpus callosum provide fiber pathways for communication between the two hemispheres. This is important because both hemispheres receive and send sensory information. 16. How does our interpretation of language change as we learn to read? Our introduction to language is by way of hearing. This is interpreted by Wernicke’s area with the primary and secondary hearing areas of the temporal lobe. When we begin to read, visual Jimmy Kimber LECOM – Seton Hill OMS1 information conveyed by written words is channed through the angular gyrus into the already developed Wernicke’s language interpretative area of the dominant temporal lobe. 17. What are the functions of the nondominant hemisphere? Why is “dominant” a misnomer? - Understanding and interpreting music Nonverbal visual experiences Spatial relations between the person and their surroundings Significance of body language Intonation in people’s voices Dominant is a misnomer because it really only refers to the language-based intellectual functions. The “nondominant” hemisphere might actually be dominant for other types of intelligence. 18. What are the effects of a prefrontal lobotomy? - Lose ability to solve complex problems Unable to string together sequential tasks to reach complex goals Unable to learn to do several parallel tasks simultaneously Decreased aggressiveness, ambition Inappropriate social responses, including loss of morals, little reticence with sex, excretion Unable to carry through long trains of thought Moods change rapidly from sweetness to rage 19. Which characteristics are associated with the loss of ventral parts of the frontal lobes? Decreased aggressiveness and inappropriate social response 20. What is working memory? What abilities does it provide? Working Memory – ability of the prefrontal areas to keep track of many bits of information simultaneously and to cause recall of this information instantaneously as it is needed for subsequent thoughts Abilities: prognostication, plan for the future, delay action in response to incoming sensory signals, consider consequences of motor actions, solve complicated mathematical/legal/philosophical problems, correlate all avenues of information in diagnosing rare disease, control our activities in accordance with moral laws 21. What is auditory receptive aphasia, visual receptive aphasia? Auditory receptive aphasia (deafness) - result of destruction of portions of auditory association area Visual Receptive Aphasia ( dyslexia) – result of destruction of visual association areas 22. What is Wernicke’s, Global aphasia? Jimmy Kimber LECOM – Seton Hill OMS1 Wernicke’s Aphasia: destruction of Wernicke’s Area results in capability of understanding either spoken or written word, but an inability to interpret the thought that is expressed Global Aphasia: when lesion in Wernicke’s area is widespread and spreads back into angular gyrus, down to the lower temporal lobe, and up to the sylvian fissure, the person will be demented for language understanding and communication. 23. What are 2 stages of mentation? - Formation of thoughts to be expressed as well as the choice of words to be used Motor control of vocalization and the actual act of vocalization itself 24. Which motor areas are controlled by Broca’s Area? The skilled otor patterns for control of the larynx, lips, mouth, respiratory system, and other accessory muscles of speech are all initiated from this area 25. Which areas of the brain are involved in articulation? Facial and Laryngeal regions of the motor cortex activate the muscles Cerebellum, Basal ganglia, and Sensory Cortex all help control the sequences and intensities of muscle contraction. 26. Examine 57-8 and describe the steps involved speaking a heard/written word Hearing to Speech: reception in primary auditory area Wernicke’s area for interpretation arcuate fasciculus tract to Broca’s area activation of motor programs in motor cortex Reading to Speech: activation of primary visual area angular gyrus region Wernicke’s area, etc. 27. What is the function of the corpus callosum? Give examples - - Provides bidirectional neural connection between most of the respective cortical areas of the two cerebral hemisphers (except for anterior temporal lobes, especially amygdala – connected by the anterior commissure) Make information stored in the cortex of one hemisphere available to corresponding cortical areas of the opposite hemisphere: o Cutting corpus callosum blocks information from Wernicke’s area to the motor cortex on the opposite side of the brain. Jimmy Kimber LECOM – Seton Hill OMS1 o o Cutting corpus callosum prevents transfer of somatic and visual information from the right hemisphere into Wernicke’s area in the left dominant hemisphere. Corpus callosum sectioning causes two entirely separate conscious portions of the brain 28. What is the holistic theory of thoughts? Holistic Theory of Thought is a definition of thought in terms of neural activity: a thought results from a “pattern” of stimulation of many parts of the nervous system at the same time, probably involving most importantly the cerebral cortex, thalamus, limbic system, and upper reticular formation of the brain stem. 29. What is consciousness? The continuing stream of awareness of either our surroundings or our sequential thoughts 30. What are memory traces? Memories are stored in the brain by changing the basic sensitivity of synaptic transmission between neurons as a result of previous neural activity. The new or facilitated pathways are memory traces. Once they are established, they can be selectively activated by the thinking mind to reproduce memories. 31. What is positive/negative memory? Negative Memory - the brain has capability to learn to ignore information that is of no consequence. This is the result of inhibition of pathways for this info, and is called habituation. Positive memory – autonomic capability of enhancing and storing memory traces for consequences of pain or pleasure. This results from facilitation of the synaptic pathways, memory sensitization. 32. Define short, intermediate, long-term, working, declarative, and skill memory Short-term: lasts seconds or minutes Intermediate Long-Term: lasts days to weeks Long-Term: lasts years to a lifetime Working Memory: includes mainly short-term memory used during the course of intellectual reasoning but is terminated as each stage of the problem is resolved Declarative: memory of details of an integrated thought (surroundings, time relationship, cause of experience, meaning, and deductions of the experience) Skill: motor activities of the person’s body 33. What are the proposed mechanisms for short-term memory? - Continual neural activity resulting from nerve signals that travel around and around a temporary memory trace in a circuit of reverberating neurons Presynaptic facilitation or inhibition that occurs at synapses lying on terminal nerve fibrils immediately before they synapse with a subsequent neuron Jimmy Kimber LECOM – Seton Hill OMS1 34. Explain memory based on chemical changes in the snail Aplysia When a sensory terminal is stimulated repeatedly but without stimulation of the facilitator terminal, signal transmission at first is great but becomes less and less intense until transmission ceases. This is habituation (negative memory). If a noxious stimulus excites the facilitator terminal at the same time that the sensory terminal is stimulated, then the ease of transmission instead becomes stronger; and it will remain strong for minutes, hours, days 35. What is habituation? What is its mechanism? Habituation – type of negative memory, where sensory signals initiate less and less stimulation without a facilitating signal. Cause: results from progressive closure of calcium channels through the terminal membrane; calcium needed for transmitter release 36. What is facilitation? What is its mechanism? Facilitation – an increase in postsynaptic potential evoked by a second impulse Mechanism: - Stimulation of facilitator presynaptic terminal at the same time as the sensory terminal causes serotonin release at facilitator synapse - Serotonin activates receptors that activate adenylyl cyclase and form cAMP - cAMP activates a protein kinase that phosphorylates potassium channels to block potassium conductance - lack of K+ conductance causes prolonged action potential - prolonged action potential causes prolonged activation of calcium channels allowing great transmitter release ALSO: facilitation can cause long-term changes in membrane properties of the post-synaptic neuron instead of in the presynaptic neuronal membrane 37. What structural changes are associated with development of long-term memory? - Increase in vesicle release sites for secretion of transmitter Increase in number of transmitter vesicles released Increase in number of presynaptic terminals Changes in structures of dendritic spines that permit transmission of stronger signals 38. How do neurons change during learning? When learning occurs, the number of neuronal connections increases based on nerve growth factors released retrogradely from the stimulated cells. 39. What is memory consolidation? Why is it important? Consolidation converts short-term memory to long-term memory. It is repetitive activation of short-term memory, which causes chemical, physical, and anatomical changes in the synapses. It involves codifying information into different classes. Jimmy Kimber LECOM – Seton Hill OMS1 40. How do you transfer short term memory to long term memory? Rehearsal of the same information again and again in the mind accelerates and potentiates the degree of transfer of short-term memory into long-term memory. 41. How are new memories codified? New and old memories are compared for similarities and differences, and part of the storage process is to store the information about these similarities, rather than storing new information unprocessed. So, memories are stored in direct association with other memories of the same type. This is necessary if one is to be able to “search” the memory. 42. What is the result of removal of the hippocampi? Hippocampi may be removed for the treatment of severe epilepsy Result: virtually no capability of storing verbal and symbolic types of memories (declarative types), in long-term memory, or even in intermediate memory. Unable to establish new longterm memories of those types of information that are the basis of intelligence – anterograde amnesia. 43. Why are the hippocampi so important in helping the brain to store new memories? Hippocampi send important output pathways from the “reward” and “punishment” areas of the limbic system. So, they are important in making the decision about which of our thoughts are important enough to remember on the basis of reward/punishment. 44. What is anterograde, retrograde amnesia? Anterograde – unable to establish new long-term memories of those types of information that are the basis of intelligence. Caused by damage to hippocampi Retrograde – amnesia of events in the past; most likely to lose recent memories rather than those that occurred a long time ago (because these have been stored in wide-spread portions of the brain). Caused by damage in thalamic areas