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Chapter 2

PSYC 221 Chapter 2: PSYC221 Chapter 2 Textbook Notes

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PSYC 221
Monica Castelhano

PSYCHOLOGY 221: COGNITIVE PSYCHOLOGY WEEK 1 Chapter 2: Cognitive Neuroscience - What physiological changes happen in your mind when you hear your alarm clock and turn it off in the morning? o Happens in steps: hearing the sound when sound wave shit his ear, stimulate receptors, change sound energy to electrical, reach auditory area of the brain etc o Before this, must know that pressing snooze button will silence alarm temporarily o Complex series of events - Cognitive neuroscience is the study of the physiological basis of cognition - Understand basic principles of nervous system functioning by first considering neurons that are the building blocks and transmission lines of the nervous system o How they are organized to form the brain and signal information about the environment and our actions in the environment Neurons: The Building Blocks of the Nervous System The Microstructure of the Brain: Neurons - Nature of electrical signals in the brain and pathways that they travel began to be discovered in 19 century - By adding special stains to brain tissue, this increases the contrast between different types of tissue o Saw a network called nerve tract that was believed to be continuous which would provide a complex pathway for conducting signals - At the time, microscopes could not show details and without this, the nerve net appeared to be continuous - In 1870s, Camillo Golgi developed a stain completed by immersing slide of brain tissue in silver nitrate, colouring less than 1% of cells completely o Allowed to see structure of a single neuron - Ramon y Cajal wanted to understand the nature of nerve net o Used Golgi stain, staining only a few cells in brain tissue o Decided to study newborn animal brain tissue because lower density of cells ▪ Combination of these saw that they were individual cells ▪ This was the centerpiece of neuron doctrine, the idea that individual cells transmit signals in the NS and these cells are not continuous with other cells - Cell Body: contains mechanisms to keep the cell alive - Dendrites: branch out from the cell body to receive signals from other neurons - Axon/Nerve Fiber: transmit signals to other neurons - Neuron has a receiving and transmitting end and role, according to Cajal was to transmit signals o Won a Nobel Prize in 1906 for his ideas - 1 - PSYCHOLOGY 221: COGNITIVE PSYCHOLOGY - Also concluded: (1) there are also neurons in the brain that pick up info from the environment, like ones in our eyes or on our skin – called receptors – that have same structure but have specialized receptor to pick up info - (2) gap between end of neuron axon and dendrites of another is called a synapse - (3) Neurons are not indiscriminately connected to others, but form connections only with specific neurons to make a neural circuit The Signals that Travel in Neurons - In the 20s, Edgar Adrian recorded electrical signals from single sensory neurons due to development of electronic amplifiers o Made electrical signals generated by a neuron visible - Used microelectrodes (small hollow glass filled with conductive salt solution that pick up electrical signals) on single neurons - The recording electrode is connected to a recording device and the reference electrode is located outside of the tissue o Always measuring difference in charge o Ex. Difference starts as -70mV and when a nerve impulse or action potential is transmitted down the axon, the oscilloscope records these changes - Adrian also found that an AP travels all the way down an axon at same magnitude - Others showed that a chemical neurotransmitter is released at the end of the axon across the synapse to send a signal - Adrian studied the relationship between nerve firing and sense by increasing pressure on skin and recording changes o Height and shape of AP stayed the same, but rate of firing (# of Aps down an axon per second) increased o CONCLUSION: intensity of a stimulus can be represented by rate of nerve firing; rate of neural firing -> related to intensity of stimulation -> related to magnitude of experience - Quality of experience is associated with each sense (ex. Sound for hearing, smell for olfaction, light for vision) o Quality within a sense (ex. Different shapes, colours, movements) o All action potentials are basically the same o Neurons serving different cognitive functions transmit signals to different areas of the brain – called localization of function - 2 - PSYCHOLOGY 221: COGNITIVE PSYCHOLOGY Localization of Function - Specific functions are served by specific areas of the brain - Cognitive functions served by n the cerebral cortex – 3mm thick tissue that covers the brain Localization for Perception - Primary receiving areas for senses is one of the basic demonstrations of localization o Ex. When sound stimulates receptors in the ear, signals reach the temporal lobe - Occipital lobe: vision - Parietal lobe: skin – touch, temperature and pain - Frontal lobe: received signal from all senses; coordination of info from 2 or more senses - Taste and smell = underside of temporal and part of temporal (smell) - Initially identified by noting effects of brain damage - Prosopagnosia is an inability to recognize faces due to damage to lower right side of brain in temporal lobe o Sometimes can’t even recognize their own reflection o Restricted only to faces; can recognize objects, places etc - Localization of function also demonstrated by recording from neurons in different areas of animal brains - Brain imaging allows researchers to see when and where the brain is active when humans carry out cognitive tasks o Position Emission Tomography (PET): centered around concept that blood flow increases to active areas of the brain ▪ Radioactive tracer injected into a person’s bloodstream and then scanned to measure the signal from the tracer at each location in brain ▪ Subtraction technique: - 3 - PSYCHOLOGY 221: COGNITIVE PSYCHOLOGY ▪ Have control state, stimulation state when the person does the task, and the activity due to manipulation is determined by subtracting the control from stimulation activity o Functional Magnetic Resonance Imaging (fMRI): also based on blood flow ▪ Hemoglobin contains a ferrous (iron) molecule and has magnetic properties so when a mag field is presented, hemoglobin lines up ▪ Hemoglobin in areas of high brain activity lose some oxygen, making them more magnetic and so, react more strongly ▪ Subtraction method also used - Fusiform face area (FFA): area that responds to faces; corresponds to prosopagnosia; in temporal cortex - Parahippocampal place area (PPA): activated by images showing indoor and outdoor scenes; important for spatial layout – activity increased for empty and full roo
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