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Chapter 21

Chapter 21

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Matthias Niemeier

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Chapter 21: Attention Introduction o Attention: state of selectively processing simultaneous sources of information  There is interactions between modalities  Has to do with preferential processing of sensory information  ADHD: inattention, hyperactivity and impulsiveness  5-10% of all school aged children worldwide  Some continue to show symptoms as adults  Cause: unknown  Smaller prefrontal cortex and basal ganglia  Hereditary  Non genetic factors: brain damage, pre mature birth.  D4 and D2 dopamine receptor gene and dopamine transporter gene  Ritalin: mild central nervous system stimulant, increases dopamine effect  Cortical activity affected by attention Behavioural Consequences of Attention o We place object on fovea o Can pay attention to something on retina outside fovea Enhanced Detection o Experiment: cue stimulus at fixation point, half trials small target flashed left or right after delay period  Cue: plus sign (equally likely target left or right), arrow (4x more likely it would appear on side arrow points to)  Had valid and invalid cues with arrows (valid 4x more likely than unlikely) There was a covert switch in attention without moving the eyes that made valid cues more  detected than neutral and invalid cues less detected than neutral  Less sensitive to side opposite of attention Faster Reaction Times o Experiment 2: told to push button when they perceive a stimulus at either location  Same arrows or plus  Invalid greater reaction time than neutral and valid had a smaller reaction time than neutral  20-30 msec difference o Attention can alter speed of visual processing Neglect Syndrome as an Attentional Disorder o Neglect syndrome: ignore objects, people and sometimes themselves to one side of center gaze o Less common after left hemisphere damage o Best studied after damage to the right side (neglect left side); right has to do with spatial sense o Often also show denial o Draw wrong, point wrong, o Lesions in posterior parietal cortex in right hemisphere  also after prefrontal cortex, cingulate cortex and others  Posterior parietal: involved in attending to objects at different positions in extrapersonal space  Neglect: hard to capture attention on neglected side or disengage attention from neglected side Physiological Effects of Attention o Changes in activity that have to do with attention Functional MRI Imaging of Attention to Location o Enhancement in detection and reaction time are selective for spatial location o Attention like a spotlight o Use fMRI to study o Experiment:  Focus on center and press button based on colour and orientation of lines  Pattern of brain activity shifts retinotopically  Most activity in segment that was being attended to PET Imaging of Attention to Features o Features: ex. Speed, shape, colour o PET  Experiment:  Had to determine whether two successive images where the same or different  Recorded brain activity when attending to different features  Selective attention: attended to one feature  Divided attention: attended to all features  Subtracted divided attention from selective attention to get image of changes in brain activity associated with attention to one feature  Findings:  Ventromedial occipital cortex and V4 and IT and other visual areas in temporal lobe for shape and colour
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