Attention Flashcards
What is:
- Full Parallel Processing
- Selection for Processing
- Selection for Action
- Selective Attention
- Inattentional Blindness
- Change Blindness
FULL PARALLEL PROCESSING: When everything from the visual field is processed in parallel (not sequentially, parallely). Is not the way how the brain usually works
SELECTION for processing: Selecting certain parts of the visual system for in-depth processing.
SELECTION for action: Screening certain parts of the visual field for action, example if you need the hand to land on a specific point.
SELECTIVE Attention: Selection of one or more alternative stimuli for in-depth cognitive processing
Inattentional blindness: Not seeing gorilla while counting basketballs
Change blindness: Failing to notice the appearance/disappearance of objects between two alternating images separated with a brief blank screen
These ‘blindnesses’ do not reflect inadequacy of the visual system, they reflect the capacity limitations of our attentional systems
What is:
- Perception
- Attentional Processes
- Attention
Perception
Making sense of the external environment.
Attentional processes
interface between the external environment and our internal states (goals, expectations and so on).
Attention
Cascade of bottom-up (i.e attention grabbed by environment) and top-down (i.e. attention sustained by our goals) influences in which selection takes place.
Attention is the process by which certain information is selected for further processing and other information is discarded. Attention is needed to avoid sensory overload.
What is:
- Visual Attention
- Orienting
- Covert Orienting
- Overt Orienting
- Inhibtition of Return
- Exogenous Orienting
- Endogenous Orienting
VISUAL ATTENTION = spotlight on salient object
ORIENTING = moving focus of attention
COVERT orienting (moving attention without moving the eyes or head) and
OVERT orienting (moving the eyes or head along with the focus of attention)
Overt and covert attention are controlled by highly similar networks in Parietal (IPS) (Intraparietal sulcus) and frontal cortex (FEF) (Frontal eye
INHIBITION OF RETURN: This is the slowing of reaction time associated with going back to the previously attended location.
EXOGENOUS ORIENTING: When attention is externally guided and bottom-up
ENDOGENOUS ORIENTING: When attention is guided by goals of perceiver
SPATIAL attention study to illustrate that attention operates on a spatial basis
POSNER Cueing paradigm
3 boxes, press a button when you see a target. Sometimes a visual cue (flashing light) preceded the target. When cue preceded target by upto 150ms, participants were faster at detecting target, when there was a delay of 300ms or more they were slower. This is because the spotlight initially shifts to the cued location, but if the target does not appear, attention shifts back to another location (DISENGAGEMENT)
Spatial and Non-spatial Attentional Process
- Non-spatial
- Object-Based
- Attentional Blink
Non-Spatial attention mechanism
Object-based attention and time-based/temporal (not to be confused with temporal lobes) attentional processes.
Object-Based
When two objects (e.g., a house and a face) are transparently superimposed in the same spatial location, then participants can still selectively attend to one or the other.
Different areas of the brain are activated, attending to a face will activate the fusiform face area, and attending to a house will activate the parahippocampal place area even though both objects are in the same spatial location.
Attentional Blink
An inability to report a target stimulus if it appears soon after another target stimulus. Example: a series of objects (e.g., letters) are presented in rapid succession (~10 per second) and in the same spatial location. The typical task is to report two targets that may appear anywhere within the stream which are referred to as T1 and T2 (e.g., white letters among black; or letters among digits). What is found is that participants are “blind” to the second target, T2, when it occurs soon after the first target, T1 (typically 2–3 items later).
Attention
Frontoparietal Network in Attention
At what stage does the signal coming in via the retina get amplified by attention?
- Neurons in V1 (early stage) only get a small boost if attention was being paid compared to when it was not, however, a much larger boost is seen in V4 (late selection). Computational model studies to understand the mechanism showed that its the tuning function that gets amplified (seen as an amplitude gain on a graph) i.e. better signal to noise ration, i.e. relevant parts get boosted (when you pay attention) while the noise is left behind (unattended) in the V4.
- More recent studies in V1 and LGN (lateral geniculate nucleus) have shown firing rates in these areas when there is attention.
- Two main areas in attention task selection:
- Frontal Regions involved in task selection and motor selection, and
- Parietal Regions acting as a hub that pulls together bottom-up (sensory) signals with top-down (goal-based) signals.
- Two main routes:
- Ventral Route (or “what” pathway) leading into the temporal lobes is concerned with identifying objects.
- Dorsal Route (or “where” pathway) leading into the parietal lobes is specialized for locating objects in space. It plays an important role in attention, spatial or otherwise. Also guides action toward objects and some researchers also consider it a “how” pathway as well as a “where” pathway.
- Two main attention-related circuits involving the parietal lobes:
- Dorso-dorsal Circuit (involving LIP & FEF) that is involved in attentional orienting within a salience map; and a
- Ventro-dorsal Circuit (involving the right temporoparietal junction, TPJ and Ventral PFC) acts as the circuit breaker and directs attention away from its current focus.
- Lateral Intra Parietal Area (LIP) (From single cell monkey studies) Is a region in posterior parietal lobe, contains neurons that respond to salient stimuli in the environment and are used to plan eye movements. LIP responds to external sensory stimuli (vision, sound) and is important for eliciting a particular kind of motor response (eye movements, termed SACCADES)
What is so special about LIP
- Does not respond to most visual stimuli, but only to stimuli that are unexpected (e.g., abrupt, unpredictable onsets) or relevant to the task.
- When searching for a target in an array of objects (e.g., a red triangle), LIP neurons respond more strongly when the target lands in its receptive field than when a distractor (e.g., a blue square) does.
- Respond more when a target is linked to either a strong reward or strong punishment.
- Sudden changes in luminance are a salient stimulus to these neurons, analogous to how luminance changes drive attention in the Posner cueing task.
- Neurons in this region have response characteristics associated with both exogenous and endogenous attention.
- It is suggested that it contains a salience map (more on this in the last slide) of space in which only the locations of the most behaviorally relevant stimuli are encoded.
- However, it also represents salience in a non-spatial way too, since it responds strongly to task-relevant targets and rewards.
- LIP also respond to the current position of the eye (its responsiveness depends on the two sources of information being multiplied together). This information can be used to plan a saccade—i.e., overt orienting of attention. There is also evidence that they may support covert orienting.
- Lesioning LIP in one hemisphere leads to slower visual search in the contralateral (not ipsilateral) visual field even in the absence of saccades.
- Spatial attention to sounds is also associated with activity in LIP neurons.
- Some neurons in LIP remap (Adjusting one set of spatial coordinates to be aligned with a different coordinate system) sound locations to be relative to the angle of the eyes so they can be used to plan saccades. instead of being located relative to the head/ears
Frontal Eye Field (FEF)
- Part of the frontal lobes
- Responsible for voluntary movement of the eyes.
Hemispheric differences in parietal lobe contributions to attention
Right hemisphere: attends to a salient stimulus
Left hemisphere: suppresses a non-salient stimulus
Hemispatial Neglect
- A failure to attend to stimuli on the opposite side of space to a brain lesion.
- The right parietal lobes of humans have a dominant role in spatial attention than its left hemisphere equivalent.
- So neglect is far more severe in a right hemisphere lesion.
Pseudo-Neglect
In a non-lesioned brain there is over-attention to the left side of space.
Feature Integration Theory (FIT)
VISUAL SEARCH: A task of detecting the presence or absence of a specified target object in an array of other distracting objects. It is a mix of bottom-up processing (perceptual identification of objects and features) and top-down processing (holding in mind the target and endogenously driven orienting of attention) (Eg, finding letter F from an array of other letters).
SERIAL & PARALLEL search: Parallel is when you don’t need to search around, you do a parallel processing and find the target pops out from all the background information, the set size doesn’t matter in this. Serial is when you have to search one by one and larger the set size longer it takes. Processing in the brain is different for both these types of searches.
Feature integration theory (FIT) is a model of how attention selects perceptual objects and binds the different features of those objects (e.g., color and shape) into a reportable experience. Most of the evidence for it (and against it) has come from the visual search paradigm. Example it is easier to find a blue ‘T’ within an array of red ‘L’s instead of a blue ‘T’ in an array if red ‘T’s
POP-OUT: The ability to detect an object among distractor objects in situations in which the number of distractors presented is unimportant.
ILLUSORY CONJUNCTIONS: A situation in which visual features of two different objects are incorrectly perceived as being associated with a single object. For example, if displays of colored letters are presented briefly so that serial search with focal attention cannot take place, then participants may incorrectly say that they had seen a red “H” when in fact they had been presented with a blue “H” and a red “E”
EARLY SELECTION AND THEORIES AROUND IT
There are three stages to an input - Registration - Perceptual analysis - Semantic coding/analysis. The Filter model concerns with the extent of processing that an input signal might attain before it can be selected or rejected by internal attentional mechanisms.
EARLY SELECTION mechanisms of attention would influence the processing of sensory inputs before the completion of perceptual analyses (FIT is an example of that). In contrast,
LATE SELECTION mechanisms of attention would act only after the complete perceptual processing of the sensory inputs, at stages where the information had been recoded as a semantic or categorical representation (e.g., “chair”).
BROADBENT’s FILTER MODEL: In this model, a gating mechanism determines what limited information is passed on for higher level analysis. So messages from input channels pass through a selective filter that moves the information to a limited capacity decision channel and then either information is stored in the long term memory store or it is responded to. The gating mechanism is needed at stages where processing has limited capacity.
LATE SELECTION AND THEORIES AROUND IT
LATE SELECTION: A theory of attention in which all incoming information is processed up to the level of meaning (semantics) before being selected for further processing.
NEGATIVE PRIMING (is an example of late selection): If an ignored object suddenly becomes the attended object, then participants are slower at processing it. The effect can also be found if the critical object is from the same semantic category. This suggests that the ignored object was, in fact, processed meaningfully rather than being excluded purely on the basis of its color as would be expected by early selection theories such as FIT.
COCKTAIL PARTY Effect: At a cocktail party you can zone in and out of a conversation. Selective auditory attention allows you to talk to the person next to you while with covert attention you can attend to a conversation going on behind you. In a lab this setup is called DICHOTIC LISTENING wherein a headphone plays different sounds in both ears. In such a scenario input from one ear is neglected.
Such information processing BOTTLENECKS seem to occur at stages of perceptual analysis that have a limited capacity. What is processed are the high-priority inputs that you selected. In the cocktail party experiments, however, sometimes salient information from the unattended ear was consciously perceived, for example, when the listener’s own name or something very interesting was included in a nearby conversation proving that information in the unattended channel could reach higher stages of analysis, but with greatly reduced signal strength.
SALIENCY MAP
Computational model for the different maps in the brain in which data processes, for example there seems to be a different map for things like orientation, colour, shape, intensity etc. Saliency map is the average of all the unusual conspicuousness in the visual field across all the different features to determine where you would pay attention.
This is without any top down endogenous attention. This explains why and where our attention is directed when we have a feature contrast in our visual environment.
This is why we are able to make sense of a watercolour painting even if the colour does not follow exact shape, we can still make out what the object is.