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8: Attention and Consciousness Cognitive Neuroscience David Eagleman Jonathan Downar Chapter Outline Awareness Requires Attention Approaches to Studying Attention and Awareness Neural Mechanisms of Attention and Awareness Sites of Attentional Modulation Synchronization, Attention, and Awareness 2 Chapter Outline Coma and Vegetative State: Anatomy of the Conscious State Anesthesia and Sleep: Rhythms of Consciousness Theories of Consciousness 3 Awareness Requires Attention Change Blindness Inattentional Blindness 4 Change Blindness It has long been known that there is a connection between attention and awareness. Stage magicians use covert misdirection to accomplish their craft. Change blindness is when a person does not notice even a major change in a scene. 5 Change Blindness 6 Change Blindness In many real-world examples, people are blind to the changes around them. People fail to notice when the person they were talking to changes in mid conversation. People fail to notice differences between two images, such as the tail of the airplane in the previous image. 7 Inattentional Blindness In one experiment, subjects were instructed to count the number of passes one team made in a basketball game. An actor in a gorilla costume walked through the middle of the game. Only half the subjects noticed the gorilla. In a more difficult version, only 8% noticed the gorilla. 8 Inattentional Blindness 9 Approaches to Studying Attention and Awareness Attentional Orienting Paradigms: Aiming the “Spotlight” of Attention The Oddball Paradigm: Monitoring a Physiological Measure of Attention Uncoupling Sensory Input from Perception: Sensory Rivalry 10 Attentional Orienting Paradigms The subject maintains their attention on a fixation cross while the stimulus appears on one of two nearby boxes. The subject presses a button to indicate where the stimulus is as soon as they notice the stimulus. A cue may suggest where the stimulus will appear. 11 Attentional Orienting Paradigms 12 Attentional Orienting Paradigms If the cue correctly predicts the stimulus, there is a reaction time benefit. If the cue incorrectly predicts the stimulus, there is a reaction time cost. Top-down mechanisms focus voluntary (endogenous) attention. Bottom-up mechanisms focus involuntary (exogenous) attention. 13 The Oddball Paradigm The subject is presented with a series of stimuli that are all then same, then a novel stimulus (“oddball”) is presented. A physiological measure, such as fMRI or EEG, is used to monitor the response to the oddball. 14 Uncoupling Sensory Input from Perception Perceptual rivalry occurs when the stimulus can be interpreted in one that one way. If you present a different image to each eye, the precept alternates between the two. Ambiguous figures can also be used. Precepts can often be reversed voluntarily. 15 Uncoupling Sensory Input from Perception 16 Neural Mechanisms of Attention and Awareness Seeking the Correlates of Consciousness Hemineglect: A Disorder of Attention and Awareness Neural Correlation of Attention: A Single Network or Many? 17 Seeking the Correlates of Consciousness Attention and awareness both involve widespread networks. If subjects are not attending to a particular stimulus, activation does not spread beyond sensory areas. If subjects are aware of a stimulus, the activity spreads beyond sensory areas, into frontal and parietal areas. 18 Seeking the Correlates of Consciousness 19 Hemineglect: A Disorder of Attention and Awareness Damage to right lateral parietal, lateral premotor, or medial motor areas can cause hemineglect. In hemineglect, the patient fails to attend to stimuli presented in one side of space, typically the right side. These deficits are not due to sensory problems. 20 Hemineglect: A Disorder of Attention and Awareness 21 Hemineglect: A Disorder of Attention and Awareness The attentional deficit covers multiple sensory modalities Pointing out the deficits to the patient does not help resolve the problem for more than a brief time. The unattended stimuli do activate the primary sensory cortices, but the activation does not spread. 22 Neural Correlation of Attention: A Single Network or Many? There are several attentional networks. Spatial attention involves lateral superior parietal regions. Nonspatial attention involves lateral inferior temporal regions. Internally guided spatial tasks involve medial prefrontal and parietal regions. Attending to the emotions of others involves medial prefrontal cortex and precuneus. 23 Neural Correlation of Attention: A Single Network or Many? 24 Sites of Attentional Modulation: Neurons and Neural Populations The Biased-Competition Model of Attention Attention and Single Neurons: Enhancing the Signal Attention and Local Groups of Neurons 25 The Biased-Competition Model of Attention Different stimuli are represented by activity within large populations of neurons. Multiple different populations compete to influence behavior and attention selects among these different populations. Both bottom-up and top-down factors influence which population is selected. 26 The Biased-Competition Model of Attention 27 Attention and Single Neurons: Enhancing the Signal In V4, the activity of the neurons is modulated by attention. The attended stimulus get greater control over the activity of the neuron, increasing the gain of the neuron’s response. Attention can also decrease the threshold needed to activate a neuron. Attention can increase signal-to-noise ratio. 28 Attention and Single Neurons: Enhancing the Signal 29 Attention and Single Neurons: Enhancing the Signal 30 Attention and Local Groups of Neurons Researchers record local field potentials to summarize the activity of large groups of neurons. Attention seems to reduce the correlated noise in a population of neurons, making the signal more apparent and obvious. 31 Synchronization, Attention, and Awareness Synchronization links the activity of different neurons in different parts of the brain. This may provide a solution to the binding problem. Attention can increase synchronization in pairs and in populations of neurons. 32 Synchronization, Attention, and Awareness 33 Synchronization, Attention, and Awareness 34 Coma and Vegetative State: Anatomy of the Conscious State Why Should Synchronization Matter? Unconsciousness: Coma and Vegetative State Midbrain and Thalamus: Key Players in the Conscious State 35 Why Should Synchronization Matter? Sleep, coma, and vegetative state are altered states of consciousness. Synchronization at high frequencies (about 40 Hz) leads to attention. Synchronization at lower frequencies (about 10 Hz) does not produce attention. 36 Why Should Synchronization Matter? 37 Why Should Synchronization Matter? One proposal is that synchronization is just the means to communicate more efficiently. By synchronizing the activity of different neurons, useful patterns of information emerge. 38 Why Should Synchronization Matter? 39 Unconsciousness: Coma and Vegetative State Brain activity differs in different levels of consciousness. Activity in low level sensory areas is similar in comatose and recovered patients. In recovered patients, activity increases in the lateral and medial prefrontal and parietal cortex. 40 Unconsciousness: Coma and Vegetative State 41 Midbrain and Thalamus: Key Players in the Conscious State Neurons in the midbrain reticular activating system project throughout the cortex. When the organism is alert, these neurons fire at a high rate. The firing rate slows down when the organism is asleep. Activity within the reticular activating system helps maintain consciousness. 42 Midbrain and Thalamus: Key Players in the Conscious State The intralaminar nuclei of the thalamus interact with the reticular activating system to maintain awareness. These nuclei are particularly vulnerable to oxygen deprivation. Deep brain stimulation of the intralaminar nuclei is a potential treatment to restore consciousness. 43 Midbrain and Thalamus: Key Players in the Conscious State 44 Anesthesia and Sleep: Rhythms of Consciousness Sleep: Unraveling the Rhythm of Consciousness Anesthesia: Reversible, Artificial Unconsciousness 45 Sleep: Unraveling the Rhythm of Consciousness Sleep is divided into multiple stages. Non-Rapid Eye Movement (NREM) Three stages Not associated with dreaming Overall reduction in metabolic activity Rapid Eye Movement (REM) This stage is where dreams typically occur Metabolic activity similar to awake state 46 Sleep: Unraveling the Rhythm of Consciousness 47 Sleep: Unraveling the Rhythm of Consciousness During sleep, the activity of different areas is desynchronized. When awake, TMS stimulation activates a wide network of areas. When asleep, TMS stimulation fades out without spreading widely. 48 Sleep: Unraveling the Rhythm of Consciousness 49 Anesthesia: Reversible, Artificial Unconsciousness Anesthetics inhibit neuronal activity. As anesthetic dose is increased, metabolic activity in the brain decreases. At some point, consciousness is abruptly lost. Activity in high order association areas is reduced. Significant decrease in thalamic activity. 50 Anesthesia: Reversible, Artificial Unconsciousness 51 Theories of Consciousness Dualism: The Mind-Body Problem Functionalist Theories of Consciousness Consciousness and the Integration of Information 52 Dualism: The Mind-Body Problem Dualism is the idea proposed by Descartes that the mind and the brain are two different things. Today, few accept this as correct. Nonmaterial faculties such as memory or emotion are now understood to be outgrowths of the brain. 53 Functionalist Theories of Consciousness Mental states depend on the functional role they play. The higher-order theory of consciousness suggests that a conscious perception requires: A lower-order representation A higher-order representation A functional link that connects the two 54 Functionalist Theories of Consciousness 55 Functionalist Theories of Consciousness The global-workspace theory of consciousness suggests There are many separate subunits within the brain. Consciousness involves coordinating activity with these subunits. 56 Functionalist Theories of Consciousness 57 Consciousness and the Integration of Information The integrated information theory of consciousness suggests: Consciousness is informative. Consciousness is highly integrated. 58 Consciousness and the Integration of Information 59