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Neuroscience: Exploring the Brain, 3e

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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Neuroscience: Exploring the Brain, 3e

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  1. http://www.weizmann.ac.il/home/masagi/MIB/ Neuroscience: Exploring the Brain, 3e Chapter 21: Attention

  2. 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

  3. Behavioral Consequences of Attention • Attention enhances visual detection

  4. Behavioral Consequences of Attention • Attention Decreases Reaction Times http://www.weizmann.ac.il/home/masagi/MIB/

  5. 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

  6. Physiological Effects of Attention • Functional MRI Imaging of Attention to Location • Subjects view stimulus • Change location of attended sector • Brain activity shifts retinotopically

  7. 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

  8. Physiological Effects of Attention • PET Imaging of Attention to Features (Cont’d) Color Shape Motion

  9. 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

  10. Physiological Effects of Attention • Enhanced Neuronal Responses in Parietal Cortex • Wurtz, Goldberg, and Robinson • Implications of Superior Colliculus work for explaining these findings

  11. 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

  12. Physiological Effects of Attention • Receptive Field Changes in Area V4 (Response to effective stim. But attention directed at location of ineffective stim.)

  13. 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

  14. 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

  15. 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

  16. 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

  17. Physiological Effects of Attention

  18. 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

  19. End of Presentation

  20. 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

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