Introduction to Attention

Introduction to Attention

• Suffering a stroke can impact vision, but not always to total blindness.
• Neurologists use tests involving common objects to evaluate a stroke patient's visual and attentional capabilities.
• Specific stroke symptoms include seeing only one object at a time
• Bálint's syndrome results from bilateral damage to the posterior parietal and occipital cortex and causes visual attention and awareness disturbances.
• Sensory systems face information overload daily, consciously aware of a tiny fraction of available sensory input
• The study of attention focuses on how the brain selects information and why

Information Overload

• The world contains vast information, beyond individual comprehension
• Robert Louis Stevenson observed the world's fullness and its capacity to bring happiness
• The nervous system prioritizes stimuli for survival, demanding decisions about what to process
• This chapter covers the meaning of attention, relevant anatomical structures, and the impact of brain damage on attention
• Discussion also includes how attention influences sensation and perception, along with brain networks for attentional control

Selective Engagement

• William James insightfully noted key characteristics of attention in the late 19th century
• It involves being able to choose the focus, it can be voluntary
• It involves the limitation to focus on "one out of what seem several simultaneously possible objects"
• Further described is selective attention: prioritizing some inputs, thoughts, and actions while ignoring irrelevant distractions
• Optimal attention strategies involve attending to relevant stimuli in current behaviors and goals
• Goal-driven control is shaped by individual behavioral goals, learned priorities from personal experience, and evolutionary adaptations
• Stimulus-driven control is less dependent on behavioral goals
• It is important to check out sudden loud sounds; loud noise may be a warning of danger

Cortical & Subcortical Structures

• Attentional control mechanisms determine attentional focus with cortical and subcortical networks
• Cortical areas for attention: superior frontal, posterior parietal, posterior superior temporal, and anterior cingulate
• Subcortical areas: superior colliculus and pulvinar nucleus of the thalamus
• Damage to these impairs overt and covert attention
• Attention has effects on sensory systems and signal processing

Selectivity of Attention

• Focus on the specific stages of information processing where "selection" of inputs/outputs occurs
• The influence on how sensory inputs are coded, stored in memory, processed to be semantically understood, and finally acted on in a challenging world is key
• Chapter focuses on selective attention mechanisms and role in awareness

Essential Concepts of Attention

• Selective attention hones on a stimulus/thought/action, ignoring distractions
• Arousal represents overall brain state, whereas selective attention picks specifically what to focus on at that level
• Attention relies on specific cortical and subcortical networks
• Attention processes sensory inputs, stores information in memory, and effects understanding/actions

Neuropsychology and Attention

• The understanding of the brain's attention systems has been aided by brain damage examinations
• Various attentional deficits can be seen, but few provide direct system clues
• ADHD involves neural processing with different white matter throughout the attention network, which is shown through structural MRI studies
• Those who are affected by ADHD cannot identify the affected parts of the brain very easily
• Research into syndromes such as spatial neglect and Bálint's syndrome aids in better comprehending control mechanisms
• Lesions/strokes help to map and localize attention functions in vivo
• Brain damage has aided comprehension of attention mechanisms

Brain Damage Effects

• Neglect exhibits easy notice on right side, with hair combed only on the right too
• Patients can lack any knowledge they have such deficits
• Severity and location of any such lesion will determine specific symptoms
• Unilateral spatial neglect is common, typically from stroke damage in one hemisphere, and damaging one hemisphere will cause attention biases
• Right hemisphere lesions cause left visual field neglect from the bias in attention
• Awareness limited or lost over lesion location and deficits regarding it

Case Study - Raderscheidt

• Anton Räderscheidt had a stroke in the right hemisphere at 67, causing left-sided neglect evidenced through recovery after stroke
• He showed progressive canvas use for more & more portrait face after a number of months in time
• The final result had a symmetrical face in the end though asymmetrical characteristics still were observed

Observations on Vision and Neglect

• Those affected still had normalized & undamaged vision - the affected individuals have deficits to pay attention
• Direct acting in the specific opposite of the side being bilaterally damaged
• Eye movement patterns reveal that while searching for a direction - these movements still have bias though visual range

Eye Movement and Neglect, Continued

• Patterns during rest and during visual search can present the hemisphere in the left of a lesion
• Neglect patients' eye movements bias toward the proper visual field, so they search the range in full extent and have appropriate movements left and right
• Line cancellation tests and other tests are used to diagnose these forms of neglect by those who suffered
• Cancellation tests involve patients with left-sided neglect to bisect lines - but tend to bisect on those lines to the right midline
• The visual space itself is as much to blame as only certain lines being cancelled
• Copy objects tests - those of right-hemisphere will copy clock and struggle - and cannot draw entire shapes
• When memory is brought up - cannot draw the image either

Conclusions on Milan Observations

• Milan in Italy - Luzzatti did studies regarding people with unilateral injury and had those people describing what they saw
• This lead to memory being something which just cannot be described with those kinds of visual images due to specific neglect

Visual Field Testing Observations

• Testing people and their fields reveals even slight blindness within the eye
• While flashes of light appear and those with such conditions are shown - each stimuli - they see each one and still have such field defects
• This concludes - a visual stimulus will be raised - a field will be seen (whether the opposite is occurring simultaneously is irrelvant)

Overview and Extinction

• Presentation was done on the eyes and brain stroke with stimulus - showing it off on one part of left and right
• Patient responds properly at the singular moment - yet the visual stimuli is also demonstrating no real vision
• Extinction reveals more major loss and that in both fields things may simultaneously be seen however its only that the field gets registered
• Biases can occur from the affected areas - which helps with analysis and seeing specific effects
• Marshall and Halligan share the information that - its all about focus or concentration really

Syndromes and Deficits

• Comparing deficits is possible to Bálint's Syndromes
• For those involved there - certain vision can happen as those three characteristics can prove it
• Difficulty is involved in the visual field from which is seen - while the patient sees combo or spoon - not otherwise simultaneous
• The doctor asked again to try but it doesn't help at all
• Apraxia is the true form that affects eye movements and saccades
• Cannot make any eye movements in time
• And cannot be guided

Overview of Limb Findings

• Asking limb or hand to grasp a comb - difficult time if such vision is asked
• Findings reveal and showcase neglect - and this means damages affect
• Brain gets affected - certain lobes at each point are affected
• Parietal damage is shown and occipital damage as much
• Spatial attention is an example and shows specific things
• Coordinate based attention proves it
• Brain mechanism gets proved again

Overview, Continued

• Brain gets easily affected even when objects do not and there are no spatial effects to be seen
• Memory can get easily divided by the mind due to sensory input and not so much the rest
• Patients affected go through reduced attention capacity as has been touched on
• These problems help consider how attention has - how attention works - and finally - what things to expect
• Unilateral injury may result from damage through the parts - which has limited processing capabilities
• Brain's main goal = prevent overload

Attention Models

• Voluntary = when a user intentionally attends to something. It is top-down and goal-driven. Goals and rewards control what we focus on
• Reflexive = Bottom-up stimulus catches the attention i.e. a loud bang. A balance is important
• Overt = When you turn your head to see better. Covert is when appear focused but are paying attention to students behind you
• Some focus on covert because involves changes rather than aiming of sense organs

Testing Vision Processing with Experiments

• Helmholtz studied aspects of very briefly perceived stimuli and built a screen with letters to test;
• Helmnotz noted to see it properly involved those eyes fixed to screen's center though that focus could actually stray - to which he paid attention (covert again)
• Helmholtz saw to perceive letters - when they were in the focus, did this better and that meant
• These findings - its all about voluntary movements with our intention though those eyes never changed course
• Experiments quantify the impacts in a measurable way and they quantify that affect through very accurate details

Understanding Perception better with Methodologies

• Understanding what takes to perform - and make sense - of it all - boils down to simply just how each factor does and can take affect
• Its about examining how well someone responds to such target and it's measured on different conditions/levels
• Cuing methodology and cueing tasks themselves enable focus due to just info given
• Cuing tasks give more than just some details that the upcoming stimulus is likely. This cued/controlled form = endogenous in form, where response is controlled and the intentions come from
• Reflexive behavior still comes in that though - the cues to something which gets physical. That's exogenous control through a lightning flash
• Finally though = the researchers had to figure in for not at all

Understanding Posner and the Cues/Reactions

• The target and how well they correlate determines if trial is called: valid = good connection, invalid = none, neutral = little
• By not permitting some types of time though - at some point one has to wonder why or what and to ask
• Reaction comes faster with what they get - showing benefit of attentions itself is so amazing
• Participants still were required to go through test - showing it even
• Response time gets affected by different things as those cues start getting observed
• Some of the key people suggest the stimulus helps what processing is meant and that influences

Focus Explained

• Changes are consistent as proposed as the participants - when they are watching stimulus - will affect their processing abilities
• Minute changes can matter and the targets themselves must then be tested
• But response time can only give so much as to how things work
• This question can be resolved with tests as well
• Sensory processes must be fully understood to truly figure out things with great affect

Event-Related Potential Studies

• Event Related Potential studies are those done to test the processes during attention
• Auditory context are also enhanced which shows the signal strengths of this
• Visual areas are more affected so long as what was found for those original aspects are also met
• This proves both selection and attention have influence

Take Home points

• Attention = voluntary/goal directed or reflexive/stimulus-driven, and can be overt/covert
• With earlier-selection, a stimulus doesn't need full perceptual analysis before being rejected/further processed
• In contrast, late-selection sees both attended and unattended stimuli processed equivalently, and selection only occurs at a semantic/ meaning-encoding area

What Determines Focus?

• Limited capacity stages are important for it - where there can be only certain kinds of sensory encoding
• Prevents overflow
• Spatial attention is metaphorically described - either chosen or reflexes

Neural Mechanisms and Potential Factors of Selectivity

• This should still not mean only aspects of what is studied to date are relevant
• Modalities of sensory still affect these and visual cortex was taken on as a model
• Processing incoming at the right points may help
• These functions and tests show high levels of potential factors

Spatial and Visual Aspects

• Spatially directed - can be reflexive = vision on the door is common place and does get pulled over.
• This can still be the Cortex and Subcortex
• Attention, though, still has those aspects and has used other methods
• With recordings, scientists also see several aspects are there with the effect
• Those signals (from a good stimuli ) will be affected over time
• Attended to the stimuli - are the ERPs

Stimuli and Observations

• Positive things to note - those are voltages which means the ones attended mean greater amplitude then unattended stimuli
• Earlier ones found those effects in the studies
• So what exactly is at work from all those things - the stimuli (where is this, what will be there) is now an ongoing search from several levels
• A key - at long range and the VLP (to this point)

Further Testing of Spatial Effects

• What these scientists had to ask themselves
• And what the researchers found to determine
• Results involved the hemispheres both affected
• They also asked where the two meet
• Spatial is better

Subcortical and Cortical Factors

• Alot can filter by itself - on whether such areas of the eyes receive
• The areas of these parts = that if something does work or not shows that - something - can be selected

Brain Areas and their Components

• To do those things - the people went back to several aspects
• At some points one has to wonder - do scientists even know the effect in full though no test has truly had
• Is more focus on the part = did most ever do what should though there where also several results coming forward

Tests

• Those experiments where - one of these regions where the hemispheres did not measure up to the task
• Where its known = if its in the right and it is done right. That was it.
• 20 to 30 percent at key points to the task is enough for them