Lecture 6 Brain Function Specialization in Whole Brained Individuals and Sensation and Perception JND s and Thresholds Left Brain Right Brain and Us Using the same techniques as for the corpus callosum patients you can map information into the right or left hemispheres of normal brained people What you look at in this case is the amount of time it takes for the people to complete a certain task given which hemisphere the information is mapped to If the information goes into the hemisphere with the mechanisms to process the info the processing should be quicker than if the information goes into the other hemisphere and must be moved to the correct one Independent variable which hemisphere the information is mapped to Dependant variable time it takes to name an object complete a certain Theory whole brained individuals have specialization of function just like the corpus callosum patients Prediction naming will be faster if information is routed to the left hemisphere rather than the right hemisphere if the information is routed to the hemisphere with the mechanisms that complete the task the task will take a shorter amount of time to complete than if the information is routed to the other hemisphere task Perceptual Asymmetry Perceptual Asymmetry means that there is an asymmetry in function in the brain for perceptual tasks depending on which side of the brain the information first enters Do Perceptual Asymmetry and Specialization of Function have any affect on us NO 1 Information transmission is so fast relative to the speed that we operate in the world its unnoticeable 2 It is virtually impossible to get information into one hemisphere rather than the other tactile information in the dark is one exception 3 Most of what we do involves functions that are all over the brain there is almost nothing we do that is all in one hemisphere rather than the other Exception if a particular area of the brain is damaged then localization of function may be an issue Structure There is no evidence that supports the concept of left brained right brained people Neuroimaging techniques Typically non invasive very valuable Function EEG net of electrodes is placed on head CAT takes multiple X rays computer each electrode is sensitive to combines them to show a electrical activity in a column underneath the electrode give people tasks and see where the activity in the brain is taking place fairly exact PET inject patient with radioactive MRI used to construct very detailed picture of the brain glucose give person a task and scan the brain area processing information will be using lots of glucose horizontal slice of the brain fMRI functional MRI combination of structure and function imaging Sensation and Perception Outline General Definitions Psychophysics Thresholds JND s Psychophysical scaling The Visual System The retina Perception of Color Information Processing Tri chromatic theory Opponent process theory processing of sensory input Sensation involved with the stimulation of the sense organs by external stimuli Perception selection organization and interpretation of sensory information information Definitions The world as we experience it is a sensory phenomenon we do not experience raw sensory input we select organize and interpret this raw information it may or may not be an accurate depiction of what is going on Thresholds What is the absolute minimum intensity of a stimulus that people are aware of How bright does a light have to be before you can see it Experiment Method of Limits Showed people dimmer and dimmer lights and asked them when they could see the light THIS DOESN T WORK People develop expectations that the light will get dimmer and this expectation is an extraneous variable it can significantly affect the results Experiment Method Constant Stimuli Instead of stepping down the intensity present the lights randomly to people so they cannot build up an expectation We don t know the absolute threshold for light because there is too much variance within individuals and across individuals Thus the absolute threshold is the intensity of the stimulus that is detected 50 of the time you can tell that it increases JND s The Breakthrough of Scientific Psychology Just Noticeable Difference how much of an increase must there be in a stimulus before JND s are a function of the intensity of the original stimulus they don t increase directly with the intensity of the original stimulus they increase proportionally to the intensity of the original stimulus The stimulus must increase by x not x amount these percentages are called Waber fractions JND s are a constant proportion of the original stimulus However although JND s work over most of the sensory range they break down at the limits JND s were the start of the science of psychology you could objectively measure a purely mental phenomenon
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