Lecture 10: Attention Flashcards
Definition of attention
The ability to focus on specific stimuli or locations in our environment.
Is it possible to focus attention on just one thing, even when lots of other things are going on at the same time?
– Selective: attending to one thing while ignoring others.
Due to the fact that we have limited attentional abilities
Under what conditions can we pay attention to more than one thing at a time?
– Divided: paying attention to more than one thing at a time
If we are doing something that doesn’ require a lot of attention then we can do another task.
Selective Attention
- Ability to focus on one message (or visual stimulation) and ignore all others.
- We do not attend to a large fraction of the information in the environment.
- We filter out some information and promote other information for further processing. Important in an evolutionary way, shifted attention when in danger (for survival). Attention is crucial for survival.
Attention in perception
- We can modulate our attention so that we can either see the young lady or the older lady. This is because we can switch are visual spatial attention.
- Alter our perception of the image by altering out attention.
Method used to study attention and how we filter information
Research Method: Dichotic Listening
* One message is presented to the left ear and another to the right ear
* Participant “shadows” one message to ensure he is attending to that message. Participant is asked to focus on only one message and repeat that message.
* Can we completely filter out the message to the unattended ear and attend only to the shadowed message? Can we process the information of the message in the ear that is not being focused on.
Results:
Participants could not report the content of the message in unattended ear: some information was able to pass (low level information/task, does not require a lot of attention).
* Knew that there was a message
* Knew the gender of the speaker
However unattended ear is being processed at some level
* Cocktail party effect: we can ignore everyone and focus on the conversation we are having. We are also able to reorient our attention if someone says our name (our own name does not need a lot of attention to be processed = low threshold)
* Change in gender is noticed
* Change to a tone is noticed
If the activity reaches the treshold then it will be processed . Higher treshold, lots of attention needed to process, won’t process this information when not putting direct attention to hear it.
Load theory of attention: Limited capacity
Load Theory of Attention
* Processing capacity (attentional capacity) – how much information a person can handle at any given moment
* Perceptual load – the difficulty of a given task
* High-load (difficult) tasks use higher amounts of processing capacity
* Low-load (easy) tasks use lower amounts of processing capacity
Stroop Test
Stroop effect
* Name of the word interferes with the ability to name the ink color.
* Cannot avoid paying attention to the meanings of the words. We are used to read a lot so the first thing that we dio is read the word.
* People with alterations to their attentional cortex (prefrontal cortex) will have difficulty doing this because it is a high lead tssk.
Visual spatial attention
Overt Selective attention: How Does Attention Affect our Eye
Movements and Perception?
.
Overt = doing eye mpvement to change the location of out attention
Stimulus salience: areas that stand out and capture attention
* Bottom-up process
* Depends on characteristics of the
stimulus
* Color and motion are highly salient
Scene schema: knowledge about what is contained in typical scenes
* Top-down process
* Help guide fixations from one area of a scene to another
Eyes movements are determined by task
* Top-down process
* Eyes movements preceded motor actions by a fraction of a second
Attention affects our perception. One way to look at this interaction between attention and a visual scene is to look at eye movements. To pay attention to different elements = have to make eye movememts.
Attention map is driven by eye movement and are determined by the task (but what we want to do),.’
Top down processing: goal oriented task, our knowledge and our experiences.
Covert Selective Attention: How Does Attention Affect our Perception without Eye Movements?
Precueing: directing attention without moving the eyes
* Selectivly processs information using our attention without moving our eyes.
Experiment: ask participants to fixsate a cross and then present arrow that either points to right or left.
* Participants respond better and faster to a light at an
expected location than at an unexpected location.
Results:
In valid trials, participants responded faster and also better then in invalid trial, where the reaction times are longer (takes more time to detect target).
Conclusion: it shows that directing attention without moving the eyes at an expected location will enhance perception (make us react faster). When we’re really attentive, we will be quick at responding to others,
at making movement, at making a decision.
Divided Attention (The role of attention while driving)
- Has been shown that when our attention is placed on something else, the rist of accident is 4x higher (using cellphone, even handsfree).
- Attention enhances all of our senses - 100-car naturalistic driving study
– Video recorders placed in cars
– Risk of accident is four times higher when using a cell phone - Strayer and Johnston (2001)
– Simulated driving task
– Participants on cell phone missed twice as many red lights and took longer to apply the brakes - Same result using “hands-free” cell phone
- Traffic, construction, lots of car, trying to find parking = trigger your attentional network.
Omissions: How Does
Attention Affect our
Perception?
Is it true that we are not paying attention to a large fraction of the things happening in our environment?
Inattentional blindness: a stimulus that is not attended is not perceived, even though a person might be looking directly at it.
- there are a lot of things we do not see because we do not perceive stimulattion in our environment if attention is not allocated to it.
Change blindness: A phenomenon where subjects fail to detect even a large change in the visual scene.
- when you don’t know that something is going to change and you are focused on something else, you will not perceive the change.
Physiology of Attention
- Increased activity in specific areas involved in localization when we use attention
- Attention enhances neural response.
- Attentional processing is distributed over many areas of the brain.
- Using fMRI to detect cortical activity during a search task
- Attention to an expected direction of movement caused increased brain activity in a number of brain areas (e.g., V4).
- When there is a lesion that affects this visual spatial attention network, we will see the disorders associated to that network.
Only the fact that the participant moved his attention to different location will change the activity of the visual cortex. The attentional network will modify activity of the visual cortex.
The Frontalparietal Attention Network
When we talk about the frontal parietal network, we’re talking about communication between the frontal lobe and the parietal lobe that eventually communicates with the visual areas.
Frontal lobe
* Frontal Eye Field
(FEF)
* Prefrontal cortex
Parietal lobe
* Lateral
intraparietal
cortex
Visual Areas
* V1, V2, V4, MT
Frontoparietal attention and saliency maps
When there’s an image, we can really separate each of the features of this image into different feature maps. This is bottom up processing because the information is coming from the image and not from our brain.
When we look at expectations, behavioural goals, preferences (what is contained in our working memory = higher order levels) affect how we allocate our atention, it means it is top down processes.
Combine top down processes with bottom up processes what we have is a priority map. Priority map calculates what comes from the top down system and the bottom up system and decide where they neeed to place there attention (Most important place to look at).
Thalamus will receive all of the attentional, perceptual goal oriented information and will try to coordinate all of this network by having bidirectional activity with each of these regions.
Type of task we can use to assess the activity of the posterior dorsolateral prefrontal cortex (include area 6 and 8).
Conditional Associative Learning Task
This type of task depends a lot on on top down attention.
* Ask participants to make associations between a visual stimulation and a manual response. When the participants see the image, he has to respond using the correct button associated with that image.
* Use this kind of task to assess te activity of the posterior dorsolateral prefrontal cortex because it uses a lot of attention
Type of task we can use to assess the activity of the posterior dorsolateral prefrontal cortex (include area 6 and 8).
Visual Search
A lot of distractors. A lot of information that we need to inhibit. Seeing how the regions will activate when we do this task.
Correlates of conditional learning
Area 6 and 8
**Posterior dorsolateral prefrontal cortex:
Area 6DR (dorso-rostral) (not on precentral gyrus) and area 8 **
Prefrontal cortex = granular cortex
We can look at the function of these areas by using conditional learning or a visual search among multiple distractions.
* High-level conditional allocation ofattention to competing stimuli in the environment. When there is a high load task including visual search or switch of attention, these areas are crucial.
* Visual search among multiple distractions
* Allows to switch attention flexibly between different aspects of the visual, auditory and somatomotor environment based on instructions.
* Lesions in these areas will make it difficult to do these tasks.
What do we mean by difficulty in conditional associative learning?
Posterior dorsolateral prefrontalcortex:
* Conditional associative learning:
we will have difficulty learning the rule “if X, then Y”. If you see this image then press the left button. If you see this image press the right button. This is what we call visual motor association.
➢ Visual-visual associations (area 8)
➢ Visual-motor associations (area 6DR)
The studies by Petrides in animal models have demonstrated what?
Studies by Petrides in animal models have demonstrated:
* Area 8 is involved in attention and it is NOT triggered by an automatic, bottom-up, stimulus – driven process but rather by specific rules/goals/intentions, i.e. top-down control. If area 8 is affected we will have difficulty doing the Stroop task, visual search task, visual-visual association task.
* Area 8 is involved in high-level conditional allocation of attention to competing stimuli in the environment
* Allows to switch attention flexibly between different
aspects of the visual (area 8Av) and auditory (area 8Ad) environment
**e.g., someone walks into the room and you see them in your periphery and turn your head
Area 8AV
This can be demonstrated by conditional associative learning tasks (“if X, then Y”)
Visual-visual associations = area 8Av
- “If visual stimulus X is presented, attend to visual stimulus Y”
- Involves a visual search for the correct target amongst multiple distractors based on specific rules that are learned through trial and error (red T example)
- We know that area 8Av has connections to the Frontal Eye Fields (FEF) for control of eye movement, area PG (spatial processing), and the inferotemporal cortex (ventral stream of vision).
Area 8Ad
Auditory-auditory associations = area 8Ad
* “If auditory stimulus X is presented, attend to auditory stimulus Y”
* We know that area 8Ad has connections to area PG and STG (auditory input)
* Imaging studies in humans have supported the animal model results concerning area 8
* Patients with damage to this posterior dorsolateral cortex area 8 will be unable to perform such conditional associative learning tasks
Impacts of Deficits of the Posterior DLPFC
Increased risk of accidents
* DLPFC is involed in:
1) Mental workload
2) Executive control: task switching and task-set reconfiguration, prevention of interference, inhibition, planning, and working memory.
* Greater crash risks in adolescent because DLPFC not completely mature.
Poor Stroop performances
* Increased number of mistakes.
* Increased reaction times.
* Executive control: inhibition, attentional allocation, mental prioritization.
Deficits of te posterior DLPFC is also associated with?
Associated with developmental deficits: ADHD (attention deficit hyperactivity disorder) and Conditional Learning Deficits. ADHD kids have difficulties doing conditional learning taks due to alteration of the dopaminergic system. Prefrontal cortext does not receive adequate dopamine in order to function properly.
Attention deficit hyperactivity disorder:
Symptoms:
* Inattention
* Hyperactivity
* Impulsivity
Structures:
* Prefrontal cortex
Treatment:
* Medication targeting the dopaminergic system
Frontoparietal network at large
Lesions to the dorsal pathway (parietal lobe)
Disorders of visuospatial attention
Simultagnosia
Visual spatial attentional problem
* happens when dorsal pathway is altered. Lesion to parietal cortex.
* Can recognise objects presented one at the time
* Hard when several objects presented simultaneously or a complex scene (only able to display attention to one item, not multiple items).
* Can count objects.
* Can navigate normally in the environment
* Can SEE the scenes but hard to identify them
Reading: Can name words but not non-words, even if they both have a similar spatial span.
Why? words were processed as single objects, while non-word letter strings are processed as multiple objects (i.e., distinct letters).
Unilateral neglect
…or hemineglect.
* Caused by lesions to the parietal cortex.
* They do not have a visual deficit, their deficit is perceptual due to attention. Visual-spatial attention deficit.
* Patients with unilateral neglect are not aware of what’s in one half of space: the half contralateral to the lesion
* Mostly lesions in the right hemisphere → parietal
* If you ask them to draw something, they will neglect the left part of the sheet
* Anosognosia: not aware of their deficits. Not aware that they are neglecting half of their environment.
Right versus left hemisphere
in attention
General neglect mainly happens when there is a lesion in right hemisphere. Because:
The right hemisphere is better for:
* Spatial orientation
* Distribute attention in space
*The left hemisphere is better for language.
* Lesion in the Left posterior parietal area: usually no hemineglect
* They can have Agraphia, Acalculia… (inability to calculate or write)
Why?
→ The right hemisphere posterior parietal area still receives the information by interhemispheric connections and can compensate. When there is a left hemisphere lesion, the right hemisphere will send the adequate information to the left hemisphere, which will allow for compensation.
Tests for unilateral neglect
1) The line bisection test
* Instructions: ‘place a mark with a pencil through the
center of a series of horizontal lines’
* Normal participant will go to center of the line. Someone that will neglect all the left part of each horizontal line will put the middle line more to the right.
2) The Cancellation test:
* Visual search (ex: circle all the A’s - patients with unilateral neglect will only circle all the As on one side)
* Must cross out lines (only cross out lines on the right side, none on the left side).
Personal neglect
- Can also neglect to shave their left face or to put the left sleeve of their sweater
- Ignore one half of their bodies (contralateral to lesion site)
- Parietal lobe: representation of where your body parts are
→ Personal neglect vs extra-personal neglect (ignore a part of our body). Extra-personal neglect is where we neglect a part of the environment.
Balint-Holmes Syndrome
Location of damage:
* Damage to the parieto-occipital lobes on both sides of the brain (bilateral lesion), but a lot of inter-individual variability (not sure what lesion leads to this syndrome).
Deficits:
* Defect in reading and writing
* Fail to recognize position and distances between objects
* Unable to grasp or point accurately to objects
Disorders: (need to asses if the patient has these)
* Simultanagnosia: inability to perceive the visual field as a whole
* Ocular apraxia: inability to disengage/shift attention from fixated objects. Patient will always fixate the right side of his visual field and will not be able to switch his eye movement to the left. Inability to switch attention to the oher visual field.
* Optic ataxia: inability to move the hand to a specific object by using vision. Associaton beween vision and hand movement is altered.
