4- Attention Flashcards
What is attention?
Attention is the process by which certain information is selected for further
processing and other information is discarded.
Attentional processes lie at the interface between the external environment and our internal states (goals, expectations and so on).
Attention can be driven by the environment - what is this system called?
Stimulus-evoked attentional system- our attention is being grabbed, so-called “bottom-up”. This is unconscious/automatic. Can be due to unusual noises, smells, etc.
Attention can be driven by our goals- what is this system called?
Goal-evoked system- our attention is being sustained, so-called “top-down”. This is conscious selection of sensory input/actions. Used in activities requiring extended focus e.g. concentrating on speech in a second language or driving on a dark, wet road when tired.
Attention is not a single process but instead 3 networks of distributed anatomical areas associated with different attentional processes. What are these 3 networks/levels of attention?
- Alerting network- readiness
- Orienting network- Location
- Executive control network - reaction/response
How do we know these 3 levels of attention are distinct?
There is low correlations between performance on three levels
Different neurotransmitters involved in the different systems- noradrenaline in alerting and acetylcholine in orienting
Alerting networks- Arousal, tonic alertness, circadian rhythms
Arousal= readiness to detect stimulus
Tonic alertness= a baseline level of attention that enables a person to remain aware and responsive to their environment for long durations
Circadian rhythms= are natural, internal processes that regulate the sleep-wake cycle. Longest reaction times early in the morning, get gradually more alert as day goes on. Associated with diurnal changes, body temp, cortisol secretion.
What is level of arousal regulated by and where is this located?
Level of arousal regulated by reticular formation which is located in brainstem- medulla, pons, midbrain. This is not happening in our consciousness.
Controls sleeping/wakefulness, levels of arousal through neurotransmitter projections.
Noradrenaline is the neurotransmitter in alertness. State effects of noradrenaline
In sympathetic nervous system:
Increased HR, BP.
Widening of pupils
Widening of air passages
Narrowing of blood vessels in non-essential organs. In the extreme, this is ‘fight or flight’ response.
In central nervous system:
This is increased alertness/vigilance
(alertness) Where is noradrenaline network?
Locus Coeruleus- nucleus in pons produces noradrenaline. Projections from here to other brain areas. Particularly interior frontal, inferior parietal lobe and anterior cingulate.
Activation broadly correlates with vigilance and reaction speed.
what is inattentional blindness?
A failure to be aware of a
visual stimulus because
attention is directed away
from it.
What is change blindness?
A failure to notice the appearance/disappearance
of objects between two alternating images. These examples reflect the capacity limitations in our processing sytems rather than a fundamental limitation on vision.
What is perception?
The incoming information that attention selects from. Ultimately forms the content of awareness.
Regions involved in perception e.g. visual ventral stream.
What is awareness?
An outcome (a conscious state) of perceived stimuli that pass through attentional filter
Relationship between attention and awareness derived from studies contrasting conscious and unconscious perception. Findings:
Greater activity in regions involved in perception (e.g. visual ventral stream) when participants are aware of stimulus vs unaware.
There is spread of activity to distant brain regions (frontoparietal network) in aware state.
Moving the focus of attention is called orienting. What is the difference between covert and overt orienting?
Covert orienting= moving attention without moving the eyes or head
Overt orienting= moving the eyes or head along with focus of attention.
Posner’s case study to illustrate that attention operates on a spatial basis:
The ‘attentional spotlight’ is attracted by a sudden change in the periphery- thus attention is externally guided and bottom up- referred to as exogenous orienting.
What is endogenous orientating?
Attention is guided by the goals of the perciever. E.g. presented with words and varied instructipn “focus on the central letter” or “focus on the whole word”. Faster judgements about all letters when focussing on whole word.
Another paradigm that uses endogenous attention is called visual search, what is this?
Participants asked to detect the presence/absence of a specified target object e.g. the letter F in an array of other distracting objects. It is a mix of bottom-up processing (perceptual identification of objects/features) and top-down processing (holding in mind the target and endogenously driven
orienting of attention).
What is attentional blink?
An inability to report a target stimulus if it appears too soon after another target stimulus
What is the role of the ventral route in attention?
Ventral route is the “what” pathway, leading into the temporal lobes and is concerned with identifying objects.
What is the role of the dorsal pathway in attention?
The dorsal route is the “where” pathway that leads to the parietal lobes. It guides action towards objects. Important for spatial orientating.
An area in the parietal lobe called the LATERAL INTRAPARIETAL AREA is involved in attention- explain how.
This area responds to external stimuli (vision/sound), usually unexpected stimuli and is important for eliciting a particular kind of motor response. It contains neurones that respond to salient stimuli in the environment and are used to plan eye movements.
What is pseudo-neglect?
PSEUDO-NEGLECT= In a non-lesioned brain over-attention to the left side of space. For example, there is a general tendency for everyone to bisect lines more to the left of centre.
The right-parietal lobes considered to have more dominant role in spatial attention, therefore right hemisphere lesions have severe spatial attention consequences particularly for the left of space.
What is hemispatial neglect?
A failure to attend to
stimuli on the opposite
side of space to a brain
lesion. Often associated with legions to right posterior parietal lobe.
It is proposed that the left and right parietal lobes have different roles in non-spatial attention- what are these roles?
the right hemisphere is considered important for attending to a salient stimulus
the left hemisphere is important for suppressing a non-salient stimulus or
“ignoring the elephant in the room”
Theories of attention: The feature Integration theory (FIT; Treisman et al)
FIT is a model of how attention selects perceptual objects and binds the different features of those objects (e.g. colour and shape) into a reportable experience. According to FIT, when a target is defined by a conjunction of features e.g. Blue letter H, search becomes slower when there are more items because the items are searched serially.
Evidence has come from visual search paradigm:
If an object does not share features with other objects in the array it appears to “pop out”. When there is a number of distractors, each candidate object must be serially inspected in turn.
Feature Integration Theory is an example of EARLY SELECTION model of attention. What does this mean? Contrast with late selection model.
According to early selection theories, information is selected according to perceptual attributes (e.g., color or pitch).
Late selection theories assume all incoming information is processed up to the level of meaning (semantics) before being selected for further processing.
An example of late selection is negative priming effect- what is this?
If an ignored object
suddenly becomes the
attended object, then
participants are slower at
processing it.
Theories of attention: Biased competition theory
It explicitly rejects a spotlight metaphor of attention (inherent in FIT). Attention is not a dedicated module in the brain, but a wide set of mechanisms for reducing many inputs to limited outcomes.
The biased competition theory explains why damage to the parietal lobe can also lead to extinction. What is this?
In the context of attention, unawareness of a stimulus in the presence of competing stimuli.
Patients with right parietal lobe lesions may fail to notice the stimulus on the left when two stimuli are briefly shown (called extinction), but notice it when it is shown in
isolation. It suggests that attention depends on competition between stimuli.
In competition:
Ipsilateral filed to lesion wins, contralateral side perceived in the absence of competition.
Theories of attention: the premotor theory of attention
The premotor theory of attention assumes that the orienting of attention
is nothing more than the preparation of motor actions- primarily a theory of spatial attention
Consequences of Balint’s syndrome
Damage to both L+R parietal lobes, severe spatial disturbances. May only notice one object at a time (simultanagnosia).
Optic ataxia (using vision to guide hand movements e.g. inability to reach towards object being focused on despite the object being perceived and movement being initiated)
Optic apraxia (fail to make appropriate eye movements, problems with changing focus to new object)
Illusory conjunctions
A situation in which
visual features of two
different objects are
incorrectly perceived as
being associated with a
single object.
Hemispatial neglect is failure to attend to stimuli on opposite side of space to their lesion. How do we test hemispatial neglect?
Copying or drawing from memory- patients tend to omit features on the left
Line bisection- patients tend to misplace the centre of the line towards the right
Cancellation tasks- patient must search for targets in an array, striking through them once found.
How is hemispatial neglect different from hemianopia (a primary visual field deficit)?
Person with hemianopia searches for things that should be there, can take in full visual scene by moving eyes and head to orientate.
Person with hemispatial neglect:
Does not search for things that should be there. Lack of awareness of half of allocentric space. Even mental representation. Not a sharp and absolute border between neglected and non-neglected space.
Representational neglect
Bisiach and Luzzatti (1978) established that neglect can occur for spatial
mental images and not just for spatial representations derived directly from
perception. Patients were asked to imagine standing in and facing a particular
location in a town square that was familiar to them (the Piazza del Duomo,
in Milan; Figure 9.23). They were then asked to describe the buildings that
they saw in their “mind’s eye.” The patients often failed to mention buildings
in the square to the left of the Duomo.
What is double dissociation?
Double Dissociation is when two related mental processes are shown to function independently of each other.
Within objects (object-based) vs between objects (space-based) neglect in regards to reading words.
Patients with left object based neglect may make letter substitution errors in reading words and nonwords (e.g., reading “home” as “come”), whereas patients with space-based (or between object) neglect may read individual words correctly but fail
to read whole words on the left of a page.
Neglect within objects linked to brain damage in ventral stream.
Is neglect a disorder of attention or perception
Although the main symptom of neglect is lack of awareness of perceptual stimuli, neglect is best characterized as a disorder of attention rather than perception.
WHY?
- It tends to be multisensory in nature
- The deficit is more pronounced when demands on attention are high
(e.g., voluntary orienting, presence of competing stimuli)
- There is evidence that neglected
stimuli are perceived (albeit unconsciously
and perhaps less detailed).
Orienting disorder- What is extinction?
Neglect only when there is a competing stimuli. E.g. two things held up. Cannot perceive similar stimuli simultaneously
Orienting disorder- Agnosia. What is visual agnosia?
Inability to recognise objects due to damage to ventral stream.
Contrasted with types of agnosia associated with dorsal stream damage- problem attending to objects especially their spatial location.
Orienting disorder- what is simultanagnosia?
Focus on single objects one at a time. May cause problems with locomotion e.g patient does not notice object in their path. Associated with bilateral lesions to occipital/parietal junction
Executive network of the attention system. What are the two executive networks?
- Immediate reaction- frontoparietal system: Moment-to-moment tasks, especially pre-frontal cortex.
- Sustained response plan- cingulo-opercular system, task set maintenance. Primarily involves anterior cingulate cortex and anterior insula.
Disorders of executive control network/ attentional disorders. These can be acquired (stroke, head injury) and can be developmental (ADHD). Give features of attentional disorders seen in clinical testing:
Distractibility- “name as many animals as you can…“…… “dog, lion, circus, drum, bell, wedding”
Perseveration/inertia/obsessive behaviour- Failure to switch in response to chnaging demands “name as many animals as you can”
dog, cat, cow, horse…
“Now name some types of furniture”
sheep, goat, chicken…
Primary symptoms of ADHD
Distractibility
Hyperactivity
Impulsivity
Associated with reduced activity in prefrontal cortex- reduced activity of dopamine and noradrenaline.
(lasting more than 6 months with normal intelligence and disruption to school performance)
The diagnosis is difficult before 6 years
What are causal factors of ADHD?
Biological factors (biological parents)
Environmental influences e.g prenatal alcohol exposure.
ADHD and the prefrontal cortex
Delayed myelination in prefrontal cortex for ADHD.
Plus, depletion of neurotransmitter dopamine
Inhibitory control in ADHD
Global deficits of tests of attention/executive function. Poorer performance for tests of sustained attention and suppression of prepotent responses.
Poorer performance on Go/No go tasks due to reduced prefrontal activation.
