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Chapter 1

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University of Toronto Scarborough
Zachariah Campbell

CHAPTER 1 Neuropsychology: the study of the relation between behaviour and brain function  Draws information from anatomy, biology, biophysics, ethology, pharmacology, physiology, physiological psychology, philosophy etc. Strongly influenced by:  Brain hypothesis: brain is source of behaviour  Neuron hypothesis: the unit of brain structure and function is the neuron Brain Hypothesis What is the Brain? Brain: tissue found within the skull (Old English word)  Has two mostly symmetrical halves called hemispheres: Cerebrospinal fluid (CSF): salty fluid that cushions the brain and may play a role in removing metabolic waste Cerebral cortex: crinkled tissue that covers the rest of the brain  Gyri: folds of the cortex  Sulci: creases of the cortex o Large sulci are called fissures. o Longitudinal fissure: divides the two hemispheres o Lateral fissure: divides the hemispheres into halves Lobes are named after the bones that they lie under  Frontal  Temporal  Occipital  Parietal The cerebral cortex constitutes most of the forebrain: named due to the fact that it is the front piece to develop from an embryo’s ‘tube’ of a brain  Functions from this area are usually referred to as higher functions: dealing with planning, thinking, and perception Brain stem:  Connected to the spinal cord: this descends down the back of the spinal column How is the Brain Related to Rest of the Nervous System? Brain is protected by skull and spinal cord is protected by the vertebrae. Together, they are referred to as the Central Nervous System (CNS). It is connected to the rest of the body through nerve fibers.  If damaged, the CNS will not repair itself Peripheral Nervous System (PNS): responsible for carrying information to and from the CNS  Will repair itself if damaged Sensory pathways: collections of fibers carry information for specific sensory systems, like vision and touch.  Somatic Nervous System (SNS): system used to carry sensory information from one side of the body to the hemisphere on the opposite side of the body Motor pathways: groups of nerve fibers that connect the brain and spinal cord to the body’s muscles through the SNS  Again, mainly uses motor pathways from one side of the brain to muscles on the other side of the body Autonomic Nervous System (ANS): pathways that control organ functions like lungs, heart etc. The Brain versus the Heart Alcmaeon of Croton (ca. 500 BC)  Located mental processes in the brain = brain hypothesis Empedocles of Acragas (ca. 490 – 430 BC)  Located mental processes in the heart = heart hypothesis Hippocrates and Galen were also supporters of the brain hypothesis Aristotle: the Mind (348 – 322 BC) First to develop formal hypothesis for behaviour.  Nonmaterial psyche was responsible for human thoughts, emotions, thinking, and also processes like imagination, pain, pleasure etc.  Psyche was independent of the body but worked through the heart to produce action Mentalism: philosophical position that a person’s mind is responsible for behaviour  Influenced idea that while the mind is a nonmaterial and have no parts, the brain is thought to work as whole  A lot of terms (perception, sensation, etc) come from this school of thought Descartes: the Mind-Body Problem (1596 – 1650) The body is like a machine: it is material and has spatial extent; responds mechanically and reflexively to stimulus that are presented. The mind was nonmaterial and had no spatial extent; decided what movements the body should make. Descartes located the point of action in the mind as the pineal body. He decided this because the pineal body is the only structure without two halves and is located close to the ventricles. He proposed that the mind used this structure to control CSF to open and close valves all over the body, forcing it into action. He assumed the cortex was just a cover for the pineal body. Today the pineal gland: thought to take part in controlling biorhythms. Dualism: mind and body are separate but can interact. Mind-body problem: a person is conscious and rational only because of the mind. However, how can a nonmaterial entity control a material object?  In order for the mind to control the body, it needs energy. For the mind to produce energy, it would be introducing new energy to the physical world, violating a fundamental law of physics.  Two ways of explaining this away: o Arguing that the mind and body interact and parallel but while the body can affect the mind, the mind can’t affect the body o Monists: mind and body are one unit Descartes also proposed that animals did not have minds. Unfortunately, this led to the inhumane treatment of animals, mentally ill, and children because they ‘did not have minds’ and could not feel pain. It was actually thought that children below the age of 7 did not have a mind and that the mentally ill had ‘lost their minds’. Darwin and Materialism Materialism: rational behaviour can be explained by the working of the nervous system and not the nonmaterial mind.  This perspective started with Darwin and Alfred Russell Wallace Many animals of different species had the same systems, even in different bodies – led to the idea that the similarities could be explained if all animals evolved from a common ancestor. According to Darwin, all things had common descent: as descendants from that one original organism, they developed structural and behavioural traits that fit their environment. However, they retained many similar characteristics that showed the relation to one another.  The nervous system was one characteristic that was similar, as was the brain Today, when neuroscientists use the term ‘mind’, they are referring to the collective functioning of the brain. Experimental Approaches to Brain Function Localization of Function Franz Josef Gall and his partner Johann Casper Spurzheim – one of first to propose idea that different parts of the brain have different functions.  Proposed that the cortex and its gyri were actually functioning parts of the brain and not just covering for the pineal body.  The cortex supposedly produced behaviour through the control of other parts of the brain and spinal cord through the corticospinal tract.  The two hemispheres are connected through the corpus callosum and are therefore intact Localization of function: the brain might produce differences in individual abilities (Gall) Phrenology: study of the relation between the skull’s surfaces and a person’s faculties (Spurzheim)  This was viewed by some people as a way to assess people’s personality. They invented a method called cranioscopy: a device is placed around a person’s skull to measure it and then the areas are correlated with a phrenological map  This all pretty much ridiculous However, some holdbacks from Gall are:  Naming lobes after bones  Gall’s phrenological map was precursor of many maps of the brain Localization and Lateralization of Language Jean Baptiste Bouillaud – argued that certain functions are localized in the cortex and speech is localized in the frontal lobes (in accordance with Gall). Paul Broca  Studied a man who had received a brain injury and could only swear and say ‘tan’  It was proposed that he should have damage to his frontal lobe, if Bouillaud was right o Tan had a lesion on the left frontal lobe  As a result of his studies, Broca located speech in the third gyrus of the frontal lobe on the left side of the brain  Broca demonstrated that functions could have a localized area. He also identified localization: functions could be localized to a side of the brain Broca’s area: the anterior speech region of the brain  Broca’s aphasia: syndrome that results from damage to that area Sequential Programming and Disconnection Carl Wernicke  Aware that the part of the cortex that receives the sensory pathway from the ear is located behind Broca’s area, in the temporal lobe (the auditory complex)  Suspected a connection between the functioning of hearing and that of speech.  He described an aphasia that was related to damage in that area, that was different from Broca’s aphasia o Damage was associated in the first temporal gyrus o No opposite-side paralysis was observed (this is a characteristic is Broca’s aphasia) o Patients could speak fluently but made little sense (with Broca’s aphasia, patients could not articulated but seemed to understand the meaning of words) o Although patients were able to hear, they couldn’t understand or repeat what was said to them  Wernicke’s area: region of temporal lobe associated with the aphasia In Wernicke’s area, sounds are processed into auditory images or ideas of objects. From Wernicke’s area, auditory ideas are sent along the arcuate fasciculus to Broca’s area, where the representation of speech movements are stored. From there, neural signals are sent to muscles to make the appropriate speech movements.  If the temporal lobe was damaged, speech movements are still mediated by Broca’s area but they don’t make sense because the person can’t monitor words Conduction aphasia: if the fibers connecting the two areas were cut, a person would retain speech sounds/movements along with comprehension, but speech would still be impaired because the person could not judge their speech Wernicke’s research demonstrated that while functions may be located in one area, there needs to be interacting in order for it to all work. Alexia: loss of the ability to read, due to disconnection between Wernicke’s area and the visual area of the brain Apraxia: inability to make a series of movements, due to disconnection between motor area and sensory area Loss and Recovery of Function Pierre Flourens  His work involved removing parts of the brains of animals and seeing how they dealt with the loss.  When he removed portions of the cortex, he found that, initially, animals would
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