Presentation on theme: "EE141 1 Attention and Consciousness Janusz A. Starzyk Based on book Cognition, Brain and Consciousness ed. Bernard J. Baars Cognitive Architectures."— Presentation transcript:
EE141 1 Attention and Consciousness Janusz A. Starzyk Based on book Cognition, Brain and Consciousness ed. Bernard J. Baars Cognitive Architectures
EE141 2 Attention and consciousness is brain ability to focus and select information, and then to perceive and understand it, using it to think, memorize, recall, feel, plan and act. Attentional control mechanism determines what will become conscious. We can say please pay attention but not please be conscious. Attentional selection leads to conscious results like eye movement leads to conscious observation of the event that attracted out attention. Consciousness include immediate perceptual world; inner speech and visual imagery; traces of present time in memory; recalling past experiences; feeling pleasure, pain, and excitement; intentions, expectations, and actions; believes about yourself and the world; and well defined concepts. We are conscious even we do not talk about it: the sight of falling star, thoughts about our friend, difference in sounds ‘pa’ and ‘ba’. We control what we are going to be conscious of. We can start to read a book We can decide to pay attention to this lecture We can think about mother’s birthday Introduction
EE141 3 Consciousness Figure shows how selective attention selects among competing inputs. The spotlight in the Friston circle of brain hierarchies is guided by frontal and parietal cortex but it selects visual cortex input. According to Bernard J. Baars “Contrary to past beliefs, many aspects of consciousness are not untestable at all, as shown by productive research traditions on topics like attention, perception, psychophysics, problem solving, thought monitoring, imagery, dream research, and so on.“
EE141 5 Polarities between conscious and unconscious phenomena Conscious Unconscious 11. Strategic control Automatic control 12. Grammatical strings Implicit underlying grammars 13. Rehearsed items inUnrehearsed items in Working Memory Working Memory 14. Wakefulness and Deep sleep, coma, sedation dreams (cortical arousal)(cortical slow waves) 15. Explicit inferences Automatic inferences 16. Episodic memory Semantic memory (autobiographical) (conceptual knowledge) 17. Autonoetic memory Noetic (intellective) memory 18. Intentional learning Incidental learning 19. Normal vision Blindsight (cortical blindness) Consciousness
EE141 6 Attention The term attention is used when there is a clear voluntary or executive aspect. We ask people to pay attention and they can chose to do so or not depending on their decision. Voluntary attention is involved in preparing and applying goal directed selection for stimuli and responses.
EE141 7 Attention Automatic attention selects relevant stimuli particularly prominent or unexpected. Automatic attention can be captured by human face, intense stimuli like pain, or unexpected events. Selective, attention driven by stimuli is bottom-up. Executive, goal-driven attention is top-down. In general voluntary and automatic attention are mixed. We can train ourselves to respond to telephone ring When it rings we pay attention – is it voluntary or automatic? Initially it is voluntary, as we are learning to respond to it, later becomes automatic Voluntary vs stimulus driven attention
EE141 8 Attention Attention selects information for cognitive process Selection may be shaped by emotion, motivation and salience and is under some executive control. Without flexible, voluntary access control, humans would not be able to deal with unexpected emergencies or opportunities. We would not be able to change habitual behavior to take advantage of new opportunities. Without stimulus-driven attention we would not be able to respond quickly to significant events. Thus we need both voluntary and automatic attention.
EE141 9 Experiments on attention Selective listening Subjects were presented with two streams of speech one to each ear They were instructed to repeat each word out loud People only reported hearing one of the two different speech streams They selectively listen to a single stream at a time They could switch between the two
EE Experiments on attention Visual attention is studied using the flanker task (Posner 1984) Subject focuses on the center fixation point – no eye movement allowed. The stimuli flashes just outside of the foveal region of maximum resolution (flank). Then a target appears at the site of flank with 80% probability. When the target appears at the expected location the response time is faster than without flank. When the target appears at the opposite location than the flank the response time is slower than no flank. Attention network task This is a generalization of the flanker task to test three aspects of attention: alerting, orienting, executive attention.
EE Experiments on attention Visual search paradigm (Treisman and Gelade 1980) This tests stimulus driven attention. The red vertical bar pops out automatically in the first image due to effect of parallel search. The same bar on the right hand side requires serial search and it takes longer. Serial search involves voluntary processing by executive regions frontal lobes and parietal cortex.
EE Experiments on attention The Stroop color naming test This tests reaction time to three different color naming cases. The first one has written text unrelated to colors. The second one has written text that correlates with colors. The third one has written text with words different than colors. While the first two tasks have a similar response time, the third takes much longer. The well practiced skill of reading overwrites the color naming and requires executive control to correct the errors.
EE Brain basis of attention Attention can be based on internal goals (finding a friend in the crowd) or external environment (alarm sound, bright colors) William James wrote that attention helps to: Perceive Conceive Distinguish Remember Shorten reaction time For example attention to a location dramatically improves the accuracy and speed of detecting target at this location.
EE Brain basis of attention An example of attention increased sensitivity: The recorded neurons are located in inferotemporal cortex (IT) – area for object recognition. It responds better to some visual objects (flower) than to other. Study showed that neuron begins firing in anticipation of the preferred stimulus at a higher rate than for non preferred stimulus
EE Brain basis of attention Brain must constantly select between competing inputs. Selective attention may involve a binocular rivalry when each eye receives different input. Any sources of input that cannot be integrated into a single consciously perceive whole tend to compete against each other and require selective attention. Prefrontal cortex guides what is selected.
EE Brain basis of attention What determines what object the attentional system selects? Attention cannot be understood without emotion, motivation, and prominence. Salience maps that are sensitive to prominent events exists in many regions. In visual system salience may be encoded down to V1 area. Biologically significant stimuli draw attention. Face recognition neurons respond very actively to threat faces. neurons responses to threat and neutral faces
EE Brain basis of attention Multiple salience maps has been proposed. For example: Posterior parietal cortex controls a visual salience maps, while Prefrontal cortex has a map for top-down, task relevant information and Superior colliculus has attentional guidance system to control the focus of attention
EE Brain basis of attention Human may learn to go against a cue or usual response. For instance he/she may learn not to respond to the telephone ring. This involves executive attention control as in the experiment shown on figure. First the subject learns to follow the cue like in the flanker test, Then the rule changes and the expected target appears on the opposite site of the cue.
EE Brain basis of attention The executive attention involve more prefrontal and parietal regions. Figure to the right shows a similar activation for executive attention in Stroop color-naming task
EE Brain basis of attention Brain areas for selective attention. Voluntary eye movement is controlled by frontal eye field. The anterior cingulate plays a major role in detecting and resolving conflicting information. Right frontal and parietal regions are control spatial guidance to attentional target. The pulvinar nuclei of the thalamus and superior colliculus provide eye movement control.
EE Brain basis of attention Eye movements are highly selectional skills. They are controlled by both cortical and subcortical parts The cortical control include frontal and parietal eye fields guided by explicit goals under control of dorsolateral-prefrontal cortex DL-PFC Subcortical control of eye movement is by superior colliculus SC Most visible selective attention is orienting one’s sensory receptors towards the object: looking, sniffing, listening, or touching. Visual selective attention overlaps brain region for eye movement control.
EE Brain basis of attention In the past, tracking eye movements required sizable lab equipment. Nowadays this has been reduced to a backpack size, so visual attention can be studied in a natural environment. All the brain subcortical regions that control eye movement contain visuospatial maps. These maps are synchronized with each other to focus attention on a selected visual event. There is growing evidence that the maps are synchronized with gamma-band rhythms (about 40 Hz)
EE Brain basis of attention Maintaining attention against distraction requires a significant effort; E.g. trying to study when your roommate plays a loud music Shutting out the distracting activity may overload our processing capability. Such shutting out is easier when you do more routine tasks (e.g. listen to your favorite music). Thus mental effort comes from struggle between voluntary (goal driven) and automatic attention.
EE Brain basis of conscious experience Conscious cognition is close to attention, however not identical. Useful experimental methods to study consciousness include: Inattentional blindness Visual backward masking Change blindness Attentional blink Automaticity due to practice Remembering vs knowing Conscious vs unconscious word priming You may be aware (conscious) of reading this text but you may not be conscious of the touch of your chair, gravitational forces, background conversation, your feelings for a friend, or your major life goals.
EE Brain basis of conscious experience Consciousness is not just the passive experience of sensory inputs, but the active involvement and perception. “Self"-related phenomena such as preference, social cognition, self-recognition, self-modeling, reflection, and planning all may be central to an understanding of consciousness.
EE Brain basis of conscious experience Words may be unconsciously present in your memory before you bring in a specific meaning. When you read that someone likes to fly, you do not bring to your conscious mind other meanings of this word. They are still in your memory, so what mechanism brought the correct meaning to your mind? Research supports that those other meanings were active unconsciously for a few tenth of a second before your mind decided on the right one.
EE Brain basis of conscious experience Experiments compared seen and unseen, novel vs habitual skills, conscious and unconscious processing of the ambiguous stimuli. Binocular rivalry is often used to study conscious vision by delivering two different images to two the two eyes. In the example figure the middle picture disappears due to binocular rivalry
EE Brain basis of conscious experience As long as two different inputs cannot be integrated they will rival. There are many kinds of binocular rivalry: Two different orientations will compete against each other Different color patches will rival If objects in different eyes are moving in different directions, they will rival Pictures of faces and objects will rival.
EE Brain basis of conscious experience The two neighboring inputs can be fused into a single object. You will see a 3D effect after fusion. Count how many woman’s faces you can see after fusion?
EE Brain basis of conscious experience Can you see sphinx and pyramids?
EE Brain basis of conscious experience Binocular rivalry allows comparison between conscious and unconscious picture. Subject is wearing prism goggles so each eye receives different pictures. These two inputs cannot be fused into a single object. Unconscious stimulus is still processed by the visual vortex but subjects reports only the conscious one.
EE Brain basis of conscious experience Visual backward masking. Subjects are presented two faces one after another. The smiling face is shown only for 20 msec. The brain identifies both stimuli but subject is not aware of the smiling face.
EE Brain basis of conscious experience Inattentional blindness. Subjects are asked to watch the basketball being tossed between team players (white-shirted). Most subjects are not aware of the gorilla passing by even if it stands and waves to camera. Ball throwing movie: Ball throwing movie
EE Brain basis of conscious experience Unconscious processes has been studied in several categories: Implicit memory Amnesic patient were given a word like ‘assassin’, and could not recall it later. However given a word fragment like ‘-ss-ss—’ they can retrieve the correct word Implicit learning Children do not learn the language by grammatical rules but by repetitions. The rules are inferred subconsciously. Implicit perception My occur when perceptual cortex is damaged (damage to V1), parietal neglect (inability to perceive half of the visual space), face blindness etc. Automacity Highly practiced and predictable skills become unconscious. Automatic process consumes no attentional resources, nor does it effect ongoing cognitive process or leave trace in the memory. Unconscious cognition Examples are priming or unconscious period between thinking of question and realization of the answer.
EE Brain basis of conscious experience Logothetis (2002) studied visual perception in macaque monkeys. They observed brain activities in case of visual rivalry. 20% of neurons in early visual regions (V1, V2, V4) and about 40% in areas MT and MTS responded to the dominant reportable stimuli and similar % to non-reportable stimuli. However, in object regions of the brain (areas IT and STS) 90% of neurons fired in response to reported stimuli and none for non- reportable.
EE Brain basis of conscious experience Many researchers confirmed that conscious context mobilize frontal and parietal brain regions. Dehaene (2001) used visual backward masking comparing brain activities to a conscious words to the same words when they were masked by a pattern. They used fMRI and evoked potentials to localize hot spots in the brain Comparison of evoked potentials in conscious and backward masked printed words. Conscious words maintain activities for longer period of time after presentation and engage more brain regions.
EE Brain basis of conscious experience Results that conscious context activate larger regions in brain were confirmed by observing responses of individual neurons, through electrodes placed in different brain areas. Another example is conscious and unconscious pain in which unconscious pain barely reached cortex and conscious one engaged large brain areas. While learning new tasks (like walking or simple games) children are very conscious of actions, but after they master it and action becomes more automatic it becomes less conscious. In an experiment with metronome subjects were supposed to repeat its rhythm by tapping. When rhythm was regular it was quickly learned and automated with no activation of executive control and dorsolateral regions. When rhythm was distorted randomly within 3% a little more brain activities were observed, and when it was distorted by 20% a lot.
EE Brain basis of conscious experience Technology allows to observe interactivity of the brain regions. Consider a conscious event like pointing to a cup. It involves activation of: Visual cortex to detect the cup, identify its size, location, shape and retrieve the object memory Prefrontal, premotor and motor regions to decide to point into a cup, generate a plan to move a finger, and move appropriate muscles. A decision to execute the action from prefrontal cortex, parietal spatial maps, and triggering the motor action. Sensory feedback to check whether the action has been accomplished. Each of these steps requires millions of neurons firing in a coordination. Gamma activity (40 Hz) is involved in feature binding, theta activity is involved in episodic retrieval from long-term memory, with rapid moments of synchrony between various brain regions. Brain synchrony
EE Summary Selective attention seem to be focusing of brain resources on the visual cortex. In the opposite flow a visual object mobilize cortical regions. There is a rapid cycle between attentional selection and conscious integration with simultaneous activation of parietal and frontal regions. Attention and conscious perception: selection and integration.
EE Summary A neural net architecture for selective attention and visual consciousness. Visual information flows from V1 to areas V2-V4, an d finally IT where objects are detected. Each area has its inhibitory neurons to sharpen differences at that level. Posterior parietal neurons (PP) bias visual neurons that detect the object in that spatial location. Prefrontal neurons in area 46 are involved in voluntary attentional selection. Attention and conscious flows.