AttentionAttention
Charlene O’ConnorCharlene O’Connor
July 20, 2005July 20, 2005
Cognitive NeurologyCognitive Neurology
AttentionAttentionWilliam James (1907)William James (1907)
““Everyone knows what Everyone knows what attention is. It is the taking attention is. It is the taking
possession by the mind in clear possession by the mind in clear and vivid form of one out of and vivid form of one out of
what seem several what seem several simultaneous objects or trains simultaneous objects or trains
of thought”.of thought”.
Attention Required!Attention Required! Search for a blue thing.Search for a blue thing. Feel the seat against your back.Feel the seat against your back. Listen to extraneous noiseListen to extraneous noise Prepare to tap the desk next time Prepare to tap the desk next time
you hear a cough.you hear a cough. All require “attention” to different All require “attention” to different
internal or environmental internal or environmental information and “setting up”.information and “setting up”.
OutlineOutline
What is attention?What is attention? Neuroanatomical structures of attentionNeuroanatomical structures of attention Models of attention: Posner & PetersenModels of attention: Posner & Petersen
Orienting Orienting Application: neglectApplication: neglect
AlertingAlerting Application: neglectApplication: neglect
ExecutiveExecutive Application: neglectApplication: neglect
Attentional ImpairmentsAttentional Impairments
““Attention can be Attention can be likened to a likened to a
spotlight that spotlight that enhances the enhances the
efficiency of the efficiency of the detection of events detection of events
within its beam” within its beam” Posner et al Posner et al
(1980).(1980).
Understanding attentionUnderstanding attention
Attention is required to limit entry to a Attention is required to limit entry to a finite capacity processing system by finite capacity processing system by selectingselecting only a subset of all available only a subset of all available information.information.
Attention itself is a Attention itself is a resourceresource of limited of limited capacity which can be divided between capacity which can be divided between tasks.tasks.
Attention is responsible for Attention is responsible for vigilancevigilance over timeover time
Processing and attentional capacity is Processing and attentional capacity is linked to linked to arousal arousal and and alertnessalertness. .
Attentional NetworksAttentional Networks (Mesulam, 1990)(Mesulam, 1990)
Attention is not a property of a Attention is not a property of a single cell nor the collective single cell nor the collective function of the whole brainfunction of the whole brain
Models of Attention:Models of Attention:Posner & Petersen (1990)Posner & Petersen (1990)
Attention system anatomically Attention system anatomically separateseparate
Attention carried out by a network of Attention carried out by a network of anatomical areasanatomical areas
Areas involved carry out different Areas involved carry out different functions that can be specified in functions that can be specified in cognitive termscognitive terms
Posner & Petersen’s Posner & Petersen’s Model of AttentionModel of Attention
Orienting:Orienting: directed attention directed attention disengage and shift attentiondisengage and shift attention
Alertness: Alertness: (Sustained Attention/ Arousal/ (Sustained Attention/ Arousal/ Vigilance)Vigilance)
maintaining focus over a period of timemaintaining focus over a period of time
Executive: Executive: Target Detection; Supervisory Target Detection; Supervisory ControlControl
AnatomyAnatomy
Orienting:Orienting: Posterior attentional systemPosterior attentional system
Alertness: Alertness: (Sustained Attention/ Arousal/ (Sustained Attention/ Arousal/ Vigilance)Vigilance) Right lateralized, frontal-parietal-Right lateralized, frontal-parietal-
thalamic networkthalamic network Executive:Executive:
Anterior attentional systemAnterior attentional system
Orienting: Posterior Orienting: Posterior Attention SystemAttention System
OrientingOrienting Visual locationsVisual locations OvertOvert CovertCovert
Three Cognitive Operations of Three Cognitive Operations of OrientingOrienting DisengagingDisengaging ShiftingShifting Re-engaging/ReadingRe-engaging/Reading
Anatomy of Posterior Anatomy of Posterior Attention SystemAttention System
Disengaging Disengaging posterior parietal posterior parietal lobelobe
Shifting Shifting superior colliculus superior colliculus
Re-engaging/Reading Re-engaging/Reading lateral lateral pulvinar nucleus of the pulvinar nucleus of the postereolateral thalamuspostereolateral thalamus
Lesion EffectsLesion Effects Damage to posterior parietalDamage to posterior parietal
inability toinability to disengage disengage from attentional focus to a target from attentional focus to a target located in a direction contralateral to lesion sitelocated in a direction contralateral to lesion site
Neglect/behavioural inattentionNeglect/behavioural inattention
Damage to superior colliculusDamage to superior colliculus inability to inability to shift attentionshift attention regardless of whether attention is regardless of whether attention is
directed elsewhere initiallydirected elsewhere initially Supranuclear palsySupranuclear palsy
Damage to pulvinarDamage to pulvinar slowed response to a valid or invalid cued target on side slowed response to a valid or invalid cued target on side
contralateral to lesioncontralateral to lesion LaBerge & Buchsbaum (1990)LaBerge & Buchsbaum (1990)
Pulvinar & Gating FunctionPulvinar & Gating Function
Right Visual Field Left Visual Field
LaBerge & Buchsbaum (1990)
N O Q W
M R A SO
Hemi-neglectHemi-neglect
Associated with right posterior Associated with right posterior parietal lesions.parietal lesions.
Patients tested on Posner’s orienting Patients tested on Posner’s orienting tasks have difficulty orienting tasks have difficulty orienting attention to the neglected side.attention to the neglected side.
Deficit in attentional processingDeficit in attentional processing
Hemi-neglectHemi-neglect
Problem in unilateral visual neglect Problem in unilateral visual neglect is in is in disengagingdisengaging from non- from non-neglected side to shift to neglected neglected side to shift to neglected side? side?
Simultanagnosia and visual Simultanagnosia and visual extinctionextinction
Often exhibited by individuals with Often exhibited by individuals with visual neglect.visual neglect.
Simultanagnosia, characterised by Simultanagnosia, characterised by inability to “see” more than one inability to “see” more than one object concurrently.object concurrently.
Neglect of other Neglect of other “spaces”“spaces”
Representational space (Bisiach Representational space (Bisiach and Luzzatti(1978).and Luzzatti(1978).
Sensory space (Bisiach 1988).Sensory space (Bisiach 1988). Object centred space.( e.g. Driver Object centred space.( e.g. Driver
and Halligan 1991).and Halligan 1991). Personal spacePersonal space Suggests a very complex variety of Suggests a very complex variety of
“spatial” systems within which “spatial” systems within which attention can operate.attention can operate.
Spatial vs. Object Based Spatial vs. Object Based AttentionAttention
Most of the evidence for the Most of the evidence for the posterior attentional system posterior attentional system derived from spatial tasksderived from spatial tasks
Space-based theories Space-based theories What about objects? Can attention What about objects? Can attention
be object-based? be object-based? Is the same posterior parietal Is the same posterior parietal
attentional network engaged in attentional network engaged in object-based bottom-up attentional object-based bottom-up attentional tasks?tasks?
Object-based Attentional Object-based Attentional ProcessingProcessing
Overlapping faces and houses (all in Overlapping faces and houses (all in same location), one stimulus movingsame location), one stimulus moving
Attend to: Faces, House, or direction of Attend to: Faces, House, or direction of Motion Motion
Activity greater when attending to Activity greater when attending to preferred stimulus (eg. Fusiform face preferred stimulus (eg. Fusiform face area greater during faces)--object-based area greater during faces)--object-based attentional modulation since all stimuli in attentional modulation since all stimuli in same location.same location.
O’Craven et al. (1999)O’Craven et al. (1999)
Posner & Petersen’s Posner & Petersen’s Model of AttentionModel of Attention
Orienting:Orienting: directed attention directed attention disengage and shift attentiondisengage and shift attention
Alertness: Alertness: (Sustained Attention/ Arousal/ (Sustained Attention/ Arousal/ Vigilance)Vigilance)
maintaining focus over a period of timemaintaining focus over a period of time
Executive: Executive: Target Detection; Supervisory Target Detection; Supervisory ControlControl
Alerting: Vigilance & Alerting: Vigilance & sustained attentionsustained attention
Vigilance requires constant monitoring Vigilance requires constant monitoring for signal occurrence.for signal occurrence.
Sustained attention is required once Sustained attention is required once selection has occurred and further selection has occurred and further processing is necessary to complete processing is necessary to complete task.task.
Both involve goal maintenance over Both involve goal maintenance over time. (More an issue of executive time. (More an issue of executive control.)control.)
Related to arousal levels.Related to arousal levels.
Neuroanatomy of Sustained Attention
•Evidence from lesion & neuroimaging studies (i.e. Sturm et al., 1999)
•R-lateralized network
•DLPFC, posterior parietal cortex, subcortical (thalamic)
RDLPFC
PPC
MD Thalamus
Impaired Sustained Impaired Sustained AttentionAttention
Sustained attention is sustained Sustained attention is sustained controlcontrol
Pathological “Time on Task” Pathological “Time on Task” effectseffects
Role of sustained Role of sustained attentionattention
Robertson and Manly (1999) suggest Robertson and Manly (1999) suggest unilateral neglect associated with unilateral neglect associated with nonnon--lateralised attentional deficits.lateralised attentional deficits.
Right hemisphere (particularly Right hemisphere (particularly dorsolateral prefrontal) is more important dorsolateral prefrontal) is more important for sustaining attention than shifting it.for sustaining attention than shifting it.
Contributions to neglect, extinction and Contributions to neglect, extinction and simultanagnosia may result from a more simultanagnosia may result from a more generalgeneral effect of reduced arousal, effect of reduced arousal, impaired spatial attention and reduced impaired spatial attention and reduced attentional capacity.attentional capacity.
Posner & Petersen’s Posner & Petersen’s Model of AttentionModel of Attention
Orienting:Orienting: directed attention directed attention disengage and shift attentiondisengage and shift attention
Alertness: Alertness: (Sustained Attention/ Arousal/ (Sustained Attention/ Arousal/ Vigilance)Vigilance)
maintaining focus over a period of timemaintaining focus over a period of time
Executive: Executive: Target Detection; Supervisory Target Detection; Supervisory ControlControl
Anterior Attentional Anterior Attentional SystemSystem
Executive control of directed Executive control of directed attentionattention
Top-down processingTop-down processing overtovert,, intentionally controlled intentionally controlled
orienting systemorienting system involves frontal areasinvolves frontal areas
E.g. divided attentionE.g. divided attention Allocation of attentional resourcesAllocation of attentional resources
Anterior Attentional Anterior Attentional SystemSystem
Executive control of directed attention: involved Executive control of directed attention: involved in both selective and sustained attentionin both selective and sustained attention
Top-down processingTop-down processing Components of the anterior Components of the anterior
attentional/supervisory system:attentional/supervisory system: concentration of attentionconcentration of attention sharing attention (divided attention)sharing attention (divided attention) suppressing attention suppressing attention shifting attentionshifting attention preparatory attentionpreparatory attention setting attentionsetting attention sustaining attentionsustaining attention
(Stuss et al., (Stuss et al., 1995)1995)
Another Model: Distributed Another Model: Distributed NetworkNetwork
ReticularSystem
AC
Parietal FrontalThalamus
(Mesulam, 1985)
Sensory Representation:Directed Attention
Executive Control ofAttentional Direction
Motivational Representation
Arousal
Impairments of AttentionCerebral Vascular Accident (stroke) - diverse impairments, dependent on site, hemi-neglect
Alzheimers- impairments in control over focused and divided attention, progressive
Brain Injury - slowness of information processing, in some individuals impaired control as well. Some recovery in slowness.
Complaints of subjects two years after severe brain injury, in percentages:
- forgetfulness 54
- mental slowness 33
- poor concentration 33
- mental fatigue 30
- unable to do 2 things 21
- intolerance of bustle 19
Leclercq and Azouvi (2002):
“Impairments in control processes may be demonstrated, apart from slowed processing,
- in more complex situations
- under time pressure
- under high working memory load
- in the more severely injured patients”.
Ponsford and Kinsella (1991), Attentional Rating Scale 0 - 4
mental slowness 2.78
inability 2 things 2.44
easily distracted 2.14
Attention Deficit and Attention Deficit and Hyperactivity Disorder Hyperactivity Disorder
Symptoms: distractibility, impulsivity Symptoms: distractibility, impulsivity and overactivity and overactivity
Poor at continuous performance tasksPoor at continuous performance tasks Problems with sustained attention Problems with sustained attention
and shifting attention and shifting attention (Brewer et al., 2001)(Brewer et al., 2001)
Poorer performance on sustained Poorer performance on sustained attention related to smaller volume of attention related to smaller volume of white matter in right hemisphere white matter in right hemisphere (Simrud-Clikeman et al., 2000)(Simrud-Clikeman et al., 2000)
ConclusionsConclusions “…“….attentional computations are .attentional computations are
carried out by a complex but carried out by a complex but specifiable anatomical network and ... specifiable anatomical network and ... each area of the network has its own each area of the network has its own computations. computations.
Farah and Ratcliff (1998).Farah and Ratcliff (1998). ..attention ... a widely distributed ..attention ... a widely distributed
state in which several brain systems state in which several brain systems work on the different properties and work on the different properties and action implications of the same action implications of the same selected object.”selected object.”
Duncan (1999).Duncan (1999).
ConclusionsConclusions
A major challenge for the future is to A major challenge for the future is to determine how these multiple determine how these multiple attentional mechanisms operate in a attentional mechanisms operate in a coordinated manner to maintain coordinated manner to maintain unity of behaviour. (Posner and unity of behaviour. (Posner and Petersen 1990).Petersen 1990).