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Chapter 21

Chapter 21.docx

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Department
Neuroscience
Course Code
NROC64H3
Professor
Matthias Nemier

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Chapter 21: Attention  Attention= state of selectively processing simultaneous sources of information enables us to concentrate on one object over many others in our visual field interactions btwn modalities also occur  Cortical activity is altered by the attention we exert Behavioral Consequences of Attention  Most of the time we are paying attention to something imaged on our fovea, but it is possible to shift attention to objects imaged on parts of the retina outside the fovea shifting attention to some location on the retina enhances visual processing in many ways= enhanced detection and faster reaction times  Enhanced detection: o Experiment done for studying the effects of directing visual attention to different locations o The expectation of the observer based on the cues influenced her ability to detect the subsequent targets arrow cues caused the observer to shift her attention to th side where the arrow pointed even though her eyes didn’t movecovert shift of attention made it easier o detection the flashed targets compared to the trials when the central cue was a plus sign o Observer was also less sensitive to the targets on the side of fixation opposite to where the arrow cue pointed o Attention makes things easier to detect= reason wby we can listen in on one convo among many when we give it our attention  Faster reaction times: studies have shown that attention increases the speed of reations in perceptual studies o Experiments also showed that an observers reaction times were influenced by where the central cue told him to direct his attention o Attention can alter the speed of visual processing or the time it takes to make a decision about pressing the button  Neglect syndrome= Attentional disorder= person appears to ignore objects, people and sometimes is own body to one side of the center of gaze unilateral deficit in attention o Severe cases= patient acts as if half the universe no longer exists o Less common following left hemi damage= mostly studied in regard to neglect of the left half of the space as a result of right cerebral cortex damage o Patients also show denial o In extreme cases= refuse to believe that a limb on their left side is part of their body o If person asked to close here eyes and point toward the midline of her body, she will point too far to the right if blind folded and aksed to explore objects placed on a table before them, patients behave normally in exploring objects to the right byt are haphazard about probing to the left o Most commonly associated with lesions in p.p cortex in RH, also results from damage to the right hemi PFC, cingulate cortex and other areas o Proposal= ppc is involved in attending to objects at diff positions in extrapersonal space neglect syndrome might be a disruption of the ability to shift attention o The RH appears to be dominant for understanding spatial relationships and in split brain studies it has been shown to be superior at solving complex puzzles  consistent with general loss of spatial sense after RH lesions o Hypo= left hemi is involved in attending to objects in the right visual field whereas the right hemi is involved in attending to objects in the left and right visual fields Physiological Effects of Attention  Effects of attention can be seen in sensory areas from are V1 to visual corical areas in the parietal and temporal lobe experiments show the consequences of giving attention to a location or a feature  Enhancements in detection and reaction are selective for spatial location  FMRI shows that there may be selective changes in brain actiitvty associated with spatial shifts in attention  Areas of highest brain activity move way from the occipital pole as the attended sector moves out from the fovea the pattern of brain activity shifts retinotopically, even through the visual stim are the same regardless of which sector is attended hypo= these images show the neural effect of the spotlight of attention moving to different locations  FMRI results are consistent with the behavioral observation that visual attention can be moved independently of eye position  We are able to pay particular attention to visual features such as color to enhance our performance  While humans performed a same different discrimination task= 2 ways done to isolate the effect of attention= 2 diff versions of the experiment conducted o 1) Selective attention experiments: told to pay attention just to 1 attribute o 2) divided attention experiments: subjects asked to monitor all features and base their same diff judgements o researchers then subtracted the divided from the selected to obtain images of changes in brain activity associated with attention to one feature o different areas of cortex had higher activity when diff attributes of the stimuli were being discriminated ventromedial occipital cortex was afdected by attention to colorfand shape discrimination teask and not affected by speed of the disc task o areas in parietal cortex were influenced by
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