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http://www.weizmann.ac.il/home/masagi/MIB /. Neuroscience: Exploring the Brain, 3e. Chapter 21: Attention. Introduction. Attention: State of selectively processing simultaneous sources of information Benefits performance of behavioral tasks
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http://www.weizmann.ac.il/home/masagi/MIB/ Neuroscience: Exploring the Brain, 3e Chapter 21: Attention
Introduction • Attention: • State of selectively processing simultaneous sources of information • Benefits performance of behavioral tasks • Importance emphasized by attention-deficit hyperactivity disorder • Brain Imaging – changes in cortical activity • Study attention by examining behavioral manifestations, e.g., visual attention
Behavioral Consequences of Attention • Attention enhances visual detection
Behavioral Consequences of Attention • Attention Decreases Reaction Times http://www.weizmann.ac.il/home/masagi/MIB/
Physiological Effects of Attention • Shifting Attention • What happens to neural activity? • What brain areas are involved? • Observed in high-level cognitive and numerous sensory areas • e.g., Area V1 to visual cortical areas in the parietal and temporal lobes
Physiological Effects of Attention • Functional MRI Imaging of Attention to Location • Subjects view stimulus • Change location of attended sector • Brain activity shifts retinotopically
Physiological Effects of Attention • PET Imaging Attention to Features • Same-different discrimination task: Color, shape, speed • (A) Selective attention: one feature • (B) Divided attention: all features • Subtract B from A shows brain activity associated with attention to one feature V4, IT and other visual areas in temporal lobe Color & shape • Area MT Speed of motion
Physiological Effects of Attention • PET Imaging of Attention to Features (Cont’d) Color Shape Motion
Physiological Effects of Attention • Enhanced Neuronal Responses in Parietal Cortex • Attention: Experimental vs. Normal conditions • What happens to attention under normal conditions? • Assumption: Attention changes location prior to eye movement • Wurtz, Goldberg, and Robinson • Record neural activity from several brain regions
Physiological Effects of Attention • Enhanced Neuronal Responses in Parietal Cortex • Wurtz, Goldberg, and Robinson • Implications of Superior Colliculus work for explaining these findings
Physiological Effects of Attention • Enhanced Neuronal Responses in Parietal Cortex (Cont’d) • Posterior parietal cortex neurons • Directing eye movements • Response significantly enhanced neuronal response when eyes went to target • Spatially selective effect – not a general increase in excitability
Physiological Effects of Attention • Receptive Field Changes in Area V4 (Response to effective stim. But attention directed at location of ineffective stim.)
How is Attention Directed? • Cortical, subcortical areas • Modulate the activity of neurons in sensory cortex areas • The Pulvinar Nucleus • Guiding attention • Muscimol • GABA agonist • Neuron activity suppressed
How is Attention Directed? • Attention and Eye Movements • Eye moves to attended object • Eye movements & attention closely related • Recent experiments • Brain circuitry: Directing eyes to objects of interest • Frontal Eye Fields (FEF) • Cortical area • FEF neurons
How is Attention Directed? • Attention and Eye Movements (Cont’d) • Experiment • Train monkeys to look at display of small light spots • Place electrode in FEF and determine motor field of neurons at the tip • Small electrical stimulation enhancement? • Results • FEF involved in directing attention; Enhancing visual performance • V4 activity increased
How is Attention Directed? • Attention and Eye Movements • Results (Cont’d) • FEF stimulation mimics physiological and behavioral effects of attention • Electrical stimulation of superior colliculus • Conclusion • Guidance of attention • Integrated with system to move eyes
Physiological Effects of Attention
Concluding Remarks • Studies of attention point to flexibility of the human brain • More mental energy to one location • Enhanced sensitivity & reaction time • Ignore competing stimuli • Can be seen in brain imaging studies • Effects receptive field properties • Why do we need attention? • Cannot process all information simultaneously • Selects what information should access the limited processing resources
Behavioral Consequences of Attention • Neglect Syndrome as an Attentional Disorder • Person ignores objects, people, and their own body to one side of the center of the gaze • Associated with right-sided lesions • Hypothesis: Left hemisphere attends to right hemifield whereas right hemisphere attends to both right and left hemifields