Untitled Flashcards Set

• Attention: any of the very large set of selective processes in the brain

  • to deal with the impossibility of handling all inputs at once, the nervous system has evolved mechanism that are able to restrict processing to a subset of things, places, ideas or moments in time.

• There are several types of Attention

  • Selective attention: The form of attention involved when processing is restricted to a subset of the possible stimuli.

  • External: Attending to stimuli in the world.

  • Internal: Attending to one line of thought over another or selecting one response over another.

  • Overt: Directing a sense organ toward a stimulus, like turning your eyes or your head.

  • Covert: Attending without giving an outward sign you are doing so.

  • Divided: Splitting attention between two different stimuli.

  • Sustained (vigilance): Continuously monitoring some stimulus.

• Inattentional Blindness: a failure to notice a stimulus that would be easily reportable if it were attended.

• Change blindness is a failure to notice a change between 2 scenes.

  • If the change does not alter the gist, or meaning, of the scene, quite large changes can pass unnoticed.

  • Demonstrates that we don’t encode and remember as much of the world as we might think we do.

Bottom-up and Top-Down Processing

• Bottom-up processing: Automatic, driven by external stimulus, salient

• Top-down processing: Controlled, goal-driven

• Interaction: Working together in complementary roles

• Reaction time (RT): A measure of the time from the onset of a stimulus to a response.

• Cue: A stimulus that might indicate where (or what) a subsequent stimulus will be.

  • Cues can be valid (correct information), invalid (incorrect), or neutral (uninformative).

• Stimulus onset asynchrony (SOA): The time between the onset of one stimulus and the onset of another.

Theories of Attention

• “spotlight” model: attention is restricted in space and moves from one point to hte next. areas within the spotlight receive extra processing

• “zoom lens” model: the attended region can grow or shrink depending on the size of the area to be processed.

• Visual search: Looking for a target in a display containingdistracting elements.

• Guided search: Attention is restricted to a subset of possible items based on information about the item’s basic features(e.g., color or shape).

  • Target: The goal of a visual search.

  • Distractor: In visual search, any stimulus other than the target.

  • Set size: The number of items in a visual search display.

• Inhibition of return (IOR): The relative difficulty in getting attention (or the eyes) to move back to a recently attended (or fixated) location.

  • During searches, IOR stops you from getting stuck continually revisiting one spot.

Visual Search

• The efficiency of visual search is the average increase in RT for each item added to the display

  • many searches are inefficient.

  • Serial self-terminating search: A search from item to item, ending

  when a target is found

• Feature search: (efficient)Search for a target defined by a single attribute, such as a salient color or orientation.

  • Salience: The vividness of a stimulus relative to its neighbors.

  • Parallel: In visual attention, referring to the processing of multiple stimuli at the same time.

• Conjunction search: Search for a target defined by the presence of two or more attributes.

  • No single feature defines the target

  • Defined by the co-occurrence of two or more features

• Scene-based guidance: Information in our understanding of scenes helps us find specific objects in scenes in the real world.

• The binding problem: The challenge of tying different attributes of visual stimuli, which are handled by different brain circuits, to the appropriate object so we perceive a unified object.

  • Illusory conjunction: An erroneous combination of two features in a visual scene.

    • – provides evidence that some features are represented independently and must be correctly bound together with attention.

• Feature integration theory is a limited set of basic features can be processed in parallel pre- attentively, but that the other properties, including the correct binding of feature to objects, require attention.

• preattentive stage: the processing of a stimulus that occurs before selective attention is deployed to that stimulus.

• Rapid serial visual presentation (RSVP) -An experimental procedure in which stimuli appear in a stream at one location typically the point of fixation) at a rapid rate (typically about eight per second).

• RSVP is used to study the temporal dynamics of visual attention

• Attentional blink: The difficulty in perceiving and responding to the second of two target stimuli amid a RSVP stream of distracting stimuli.

  • The second target is often missed if it appears within 200 to 500 ms of the first target.

• Reflects the limitations of the brain's processing capacity and the time needed to reset attention.

The Neural Basis of Attention

• 3 ways responses of a cell could be changed by attention:

  1. Response enhancement

     • Attention increases the overall firing rate of a neuron when its preferred stimulus is presented.

     • This means that the cell becomes more responsive to the attended stimulus, effectively amplifying the neural signal.

       • For example, if a neuron responds to a specific orientation of a visual stimulus, attention to that stimulus will cause the neuron to fire more strongly than it would without attention.

     • This mechanism improves the signal-to-noise ratio, making the attended stimulus more salient.

  2. Sharper tunning

     • Attention can make a neuron’s response more selective, effectively narrowing its tuning curve.

     • This means the neuron responds more specifically to a preferred stimulus while reducing responses to less optimal stimuli.

       • For example, if a neuron is sensitive to a range of orientations (e.g., ±20° around its preferred orientation), attention may narrow this range, making it more selective for the exact preferred orientation.

     • This increases the precision of the neural representation, improving perceptual accuracy.

  3. Altered Tuning

     • Instead of just enhancing or sharpening responses, attention can shift a neuron’s tuning preference toward the attended stimulus.

     • This means that if attention is directed to a stimulus that is slightly different from the neuron’s usual preferred stimulus, the neuron may shift its preference to better match the attended feature.

       • For example, a neuron that normally prefers 45° orientation might shift its tuning to 50° if attention is directed to that angle.

     • This allows neurons to dynamically adapt to relevant stimuli, optimizing perception based on behavioral demands.

• Fusiform Face area (FFA) an area in the fusiform gyrus of human extrastriate cortex that responds preferentially to faces, according to fmrti studies

• Visual-field defect: A portion of the visual field with no vision or with abnormal vision, typically resulting from damage to the visual nervous system

  • damage to the parietal lobe can cause a visual field defect such that one side of the world is not attended to

• Neglect: in visual attention, the inability to attend to or respond to stimuli in the contralesional visual field,

  • typically neglect of the left visual field after damage to the right parietal lobe

  • ex. patient can not see left side of drawing

  • Attention can be object-based: sometimes neglect on one side of an object rather than one side of the visual field.

2 Pathways to Scene Perception

• Selective pathway: permits the recognition of one or a very few objects at a time. this pathway passes through the bottleneck of selective attention

• nonselective pathway: contributes information about hte distribution of features across a scene as well as information about the “gist” of the scene. This pathway does not pass through the bottle neck of attention

  • The nonselective pathway computes ensemble statistics.– Ensemble statistics: The average and distribution of properties, suchas orientation or color, over a set of objects or a region in a scene.

  • The nonselective pathway computes scene gist and layout veryquickly.

  • Spatial layout: The description of the structure of a scene (e.g.,enclosed, open, rough, smooth) without reference to the identity ofspecific objects in the scene.44