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Chapter 1

chapter 1-psyb65.pdf

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David Nussbaum

CH. 1 PSYB65- The Development of Neuropsychology ( bordeux) • traumatic brain injury (TBI): wound to brain tht results from blow to head • memory + attention are required for solving everyday problems- mental skill referred to as executive function • neuropsychology: study of the relation between behaviour and brain function --> influenced by two traditional foci of experimental and theoretical investigations into brain function: 1.) brain hypothesis, the idea that the brain is the source of behaviour 2.) neuron hypothesis, the idea that the unit of brain structure and function is the neuron, or nerve cell. The Brain Hypothesis What is the Brain? • Brain is old english word for: tissue found within the skull --> has two almost symmetrical halves called hemispheres, one on the left side of the body & other on the right. (constituting the telencephalon) • basic plan of the brain is that of a tube filled with salty fluid called cerebrospinal fluid ( CSF) that cushions the brain and may play a role in removing metabolic waste • outer layer is the cerebral cortex ( usually referred to as just the cortex): --> layer of gray matter on surface of cerebral hemispheres & composed of neurons & their synaptic connections which form from four to six sublayers --> most conspicuous outer feature of the brain is the crinkled tissue that has expanded from front of the tube to such an ex-tent that it folds over and covers much of the rest of the brain --> cortex means “bark” in Latin, chosen b/c appearance resembles that of bark & its tissue covers most of the rest of the brain • gyri: fold of the cortex; convulsion of the cortex of the cerebral hemispheres • sulci: creases between the folds (the cracks) (fissures – when the sulci are really big) • longitudinal fissure: DIVIDES the two hemispheres (also called sagittal fissure) • lateral fissure: DIVIDES each hemisphere into halves (separates temporal and parietal lobes, also called sylvian fissure) • cortex of each hemisphere divided into 4 lobes: 1.) temporal lobe- located same place as thumb on upraised fist; underneath lateral fissure 2.) frontal lobe- lying above temporal love, located in front of the brain 3.) parietal lobe- located behind the frontal lobe 4.) occipital lobe- at the very back of head; function in vision • brain's hemispheres are connected by pathways called commissures: --> largest one is corpus callosum- fiber system connecting homotopic areas of the two hemispheres.Asplit-brain patient is one whose corpus callosum has been severed • forebrain- cerebral cortex makes up most of ; cerebral hemispheres, basal ganglia, thalamus, amygdala, hippocampus, septum • brainstem- remaining “tube” underlying the cortex, includes the Hypothalamus, midbrain, hindbrain • spinal cord- brainstem is connected to spinal cord, which descends down back in the vertebral column --> e.g folded fingers is cortex, heel of hand is brainstem, arm represents spinal cord --> forebrain= mediates higher cognitive functions (thinking, perception, planning) --> brainstem= mediates regulatory functions such as eating, drinking, moving --> spinal cord= responsible for sending commands to the muscles How is the Brain Related to the Rest of the Nervous System? • Central nervous system (CNS): part of the nervous system tht is encased int he bones and includes brain & spinal cord; it is connected to rest of body thru nerve fibers • peripheral nervous system (PNS): some nerve fibers carry info away from CNS, and others bring info to it; collective name for all the neurons in the body that are located outside the brain & spinal cord; PNS tissue will regrow after damage • sensory pathway- conveys sensory info to the brain --> organized into sensory pathways, collections of fibers carry messages for specific sensory systems, such as hearing, vision, and touch --> sensory pathways carry info collected on one side of the body mainly to the cortex in the opposite hemisphere by means of a subdivision of the PNS called the somatic nervous system ( SNS) -->brain uses this information to construct its current images of the world, its memories of past events, and its expectations about the future • Motor pathways: are the groups of nerve fibers that connect the brain and spinal cord to the body’s muscles through the SNS --> movements produced by motor pathways include the eye movements ur using to read this book, hand movements u'll make while turning the pages, and posture of body as u read  Sensory and motor pathways also influence the muscles of your internal organs, such as the beating of your heart, the contractions of your stomach, and the raising and lowering of your diaphragm, which inflates and deflates your lungs --> The pathways that control these organs are a subdivision of the PNS called the autonomic nervous system (ANS): part of the nervous system tht controls the functions of all the parts of the body, with the exception of the skeletal muscles, so tht the body and its organs are prepared for rest or for vigorous activity The Brain Versus the Heart • oldest surviving recorded hypotheses are those of two Greeks: -Alcmaeon of Croton located mental processes in the brain & so believed in the brain hypothesis - Empedocles ofAcragas located them in heart & so subscribed to cardiac hypothesis • Hipprocrates & Galen argued strongly for brain hypothesis - Galen noted tht pressure on brain causes cessation of movement & even death whereas pressure on the heart causes jus pain • we now accept brain hypothesis Aristotle: The Mind • greek philopsherAristotle, 1 to develop theory of behaviour: --> proposed tht nonmaterial psyche was responsible for human thoughts, perceptions, and emotions and for such processes as imagination, opinion, desire, pleasure, pain, memory, & reason --> he believed psyche worked thru heart to produce action • philosophical position that a person’s mind is responsible for behaviour is called mentalism, meaning “of the mind” Descartes: The Mind-Body Problem • René Descartes, French anatomist and philosopher, described relation between the mind and the brain • Descartes proposed tht the body is like machines • Described as nonmaterial and without spatial extent, the mind, as Descartes saw it, was different from the body: -->body operated on principles similar to those of a machine, but the mind decided what movements the machine should make • he located the site of action of the mind in the pineal body ( small structure high in the brainstem): --> this was based on the logic that the pineal body is the only structure in the nervous system not composed of two bilaterally symmetrical halves and moreover that it is located close to the ventricles • his idea was that the mind, working through the pineal body, controlled valves that allowed CSF to flow from the ventricles through nerves to muscles, filling them and making them move --> ppl later argued against this, when pineal gland is damaged, there are no changes in behaviour • pineal gland- symmetrical structure in the epithalamus, thought by Descartes to be the seat of the soul, but now thought to take part in the circadian rhythms and known as pineal gland • dualism- theory tht there are two distinct entities tht underlie human consciousness: one is mind (or soul), the other is the body • Descartes’s dualism originated what came to be known as the mind– body problem: for Descartes, a person is capable of being conscious and rational only because of having a mind, but how can a nonmaterial mind produce movements in a material body?  To understand the problem, consider that, in order for the mind to affect the body, it would have to expend energy, adding new energy to the material world. The spontaneous creation of new energy violates a fundamental law of physics, the law of conservation of matter and energy. Thus, dualists who argue that mind and body interact causally cannot explain how  Philosophers called monists avoid the mind– body problem by believing that the mind and body are one  Descartes also proposed tht animals do not have minds-machinelike Darwin and Materialism th • by the middle of the 19 century, another theory of the brain and behaviour was taking shape: the modern perspective of materialism, the idea that rational behaviour can be fully explained by the working of the nervous system without any need to refer to a nonmaterial mind • perspective had its roots in evolutionary theories ofAlfred Russell Wallace & Charles Darwin  Darwin: all living things are said to have common descent- refers to evolutionary theory tht all animals descend from same ancestor --> as the original descends spread to various habitats thru million of years, they underwent structural and behavioural adaptations; at the same time retained many similar characteristics that reveal their relatedness to one another ExperimentalApproaches to Brain Functional Localization of Function • first theory to present idea tht diff parts of the brain have diff functions was developed by German anatomist, Franz Josef Gall & partner Spurzheim: --> proposed tht cortex & its gyri were functioning parts of the brain and not just coverings for pineal body --> they supported their position by showing through dissection that the brain’s most distinctive motor pathway, the corticospinal (cortex to spinal cord) tract, leads from the cortex of each hemisphere to the spinal cord on the opposite side of the body --> they suggested, the cortex sends instructions to the spinal cord to command movement of the muscles • Also proposed tht the cortex produces behvaiour through control of other parts of the brain & spinal cord through corticospinal tract • Gall developed a general theory of how the brain might produce differences in individual abilities into a theory called localization of function (hypothetically, the control of each kind of behaviour by diff specific brain area --> e.g he proposed that a memory area of the cortex located behind the eyes would cause the eyes to protrude • they proposed tht a bump on skull indicated well-developed cortical gyrus & thus greater capacity for certain behaviour; depression in same area indicated underdeveloped gyrus • e.g person with good memory had protruding eyes • person with hugh degree of musical ability, artistic talent, math skills wud have bumps on other parts of skull • gall correlated bumps in region of cerebellum w/ brain's “amativeness” (sexiness) center • Spurzheim produced term phrenology- study of the relation between skull's surface features and person's faculties --> map of the relation between brain functions & the skull surface = phrenological map • Phrenology was used by some to make personality assessments - used method called cranioscopy, in which a device was placed around the skull to measure the bumps and depressions there - these measures were then correlated with the phrenological map to determine the person’s likely behavioural traits - produced extremely superficial personalities; faculties like faith, self-love are impossible to define, quantify objectively Localization and Lateralization of Language • Bouillaud argued from clinical studies that certain functions are localized in the cortex and, specifically, that speech is localized in the frontal lobes, in accordance with Gall’s theory • Bouillard also suggested tht part of the brain tht controls them mite be left hemisphere - physicians had long recognized tht damage to a hemisphere of the brain impaired movement of the opposite side of the body • Figure 1.6: Broca's area is located in posterior third of the inferior, or third, convulsion (gyrus) of the frontal lobe in the left hemisphere • Broca located speech in the third convulsion (gyrus) of frontal lobe on left side of brain • He demonstrated that language was localized; thus different regions of the cortex could have specialized functions. He also discovered something new: functions could be localized to a side of the brain, a property that is referred to as lateralization  since speech is central to human consciousness= left hemisphere is referred to as the dominant hemisphere, to recognize its special role in language  Due to Broca’s contribution, the anterior speech region of the brain is called Broca’s area, and the syndrome that results from its damage is called Broca’s aphasia (defect of speech) Sequential Programming and Disconnection • many scientists began to argue against strict interpretation of Broca's findings  Wernicke was aware that the part of the cortex that receives the sensory pathway, or projection, from the ear— called the auditory cortex—> is located in the temporal lobe, behind Broca’s area. He therefore suspected a relation between the functioning of hearing and that of speech  he described cases in which aphasic patients had lesions in this auditory projection area that differed from those described by Broca in four ways: 1. Damage was evident in the first temporal gyrus 2. No opposite- side paralysis was observed (Broca’s aphasia is frequently associated with paralysis of the right arm and leg, as described for Tan) 3. Patients could speak fluently, but what they said was confused and made little sense (Broca’s patients could not articulate, but they seemed to understand the meaning of words) 4. Although the patients were able to hear, they could neither understand nor repeat what was said to them • Wernicke’s finding that the temporal lobe also is implicated in language dis-proved the strict localizationists’view • Wernicke’s syndrome is called Wernicke’s aphasia: inability to comprehend speech or to produce meaningful speech; subsequent to lesions to the posterior cortex (also called sensory aphasia, fluent aphasia) • region of the temporal lobe associated with this form of aphasia is called Wernicke’s area: posterior part of the superior temporal gyrus, roughly equivalent to area 22 • Wernicke proposed that auditory information travels to the temporal lobes from the ears. In Wernicke’s area, sounds are processed int
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