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

Reticular Activating Reticular Activating SystemSystem

Superior ColliculusSuperior Colliculus

ThalamusThalamus

Parietal LobeParietal Lobe

Anterior Cingulate Anterior Cingulate CortexCortex

Frontal LobesFrontal Lobes

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

Posner’s Cued Attentional TaskPosner’s Cued Attentional Task

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

Movie: Neglect

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)

Major Neuro-anatomical Structures:

Frontal lobes

&

Anterior Cingulate

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).