Attention

Everyone knows what attention is. It is the taking possession of the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of though. Focalization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others.

William James (1890)

Attention

Cognitive brain mechanism that facilitates processing

Taxonomy for Attention• Modality

– Visual– Auditory

• Control– Voluntary: intentional, endogenous, "top-down"– Reflexive: automatic, exogenous, "bottom-up"

• Duration– Sustained– Momentary

Taxonomy for Attention

• Modality

• Control

• Duration

• Intensity– Focused– Selective– Divided

Attention Properties

• Covert• Limited-capacity metaphors

– Bottleneck• Early selection: prior to complete perceptual

analysis of elementary features• Late selection: after to complete perceptual

analysis of elementary features

– Searchlight, spotlight, flashlight– Resources

• One capacity or many?

Attention Theory

• Cherry– Cocktail party effect

• Auditory selective attention

– Dichotic listening paradigm

Attention Theory

• Broadbent's (1958) information-processing model– Limited-capacity– Early-selection– Top-down– But, can't explain intrusion of unattended input

Attention Theory

• Late-selection theories– Deutsch & Deutsch– Treisman

• Unattended sensory input attenuated at early stage, but not filtered out

• High priority unattended input can reach semantic analysis stage

Cognitive Psychologyof Visual-spatial Selective Attention

• Eriksen Flanker Task

• Posner Cueing Task

• Treisman Visual Search Task

• Wolfe Visual Search Task

Eriksen Flanker Task

CongruentAAA

IncongruentEAE

NeutralXAX

Eriksen Flanker Task

IncongruentE A E

E A E

E A E

Eriksen Flanker Task

• Searchlight of spatial attention about 1 degree of visual angle

400

450

500

550

0.06 0.5 1

Degree of Visual Angle

CongruentNeutralIncongruent

Posner Cueing Task

• Voluntary orienting of selective attention– Costs and benefits of intended covert attention

shifts

Other Cueing Tasks

• Reflexive orienting of selective attention– Abrupt onset visual stimulus at target location– Attentional "capture"– Time-dependent costs and benefits of

unintended covert attention shift• Inhibition of return (>300 ms)

Treisman Visual Search Task

• Preattentive– Pop-out search

• Flat search function

• Attentive– Conjunctive search

• Serial search function• Moving spotlight

• Guided– Conjunctive search of items that share a feature with the

target

Wolfe Visual Search Task

• Costs of voluntary control of attentional spotlight

Neurophysiology of Spatial Selective Attention

Cortical or subcortical?

• Need good temporal resolution to answer this question

Neurophysiology of Spatial Selective Attention

• ERP and MRF Evidence– Voluntary auditory attention

• Hillyard's N1 effect• Woldorff and Hillyard’s P20-50 and M20-50 effects

Neurophysiology of Spatial Selective Attention

• ERP and MRF Evidence – Voluntary visual attention

Neurophysiology of Spatial Selective Attention

• ERP and MRF Evidence – Voluntary visual attention

• P1 effect for sustained covert attention

Neurophysiology of Spatial Selective Attention

• ERP and MRF Evidence – Voluntary visual attention

• P1 effect for cued covert attention

Neurophysiology of Spatial Selective Attention

• ERP and MRF Evidence – Reflexive visual attention

• P1 effect for cued automatic attention– Enhancement at short ISI– Inhibition at long ISI: Inhibition of return

Neurophysiology of Spatial Selective Attention

• ERP and MRF Evidence – Voluntary visual attention

• P1 effect for visual conjunction search

Neurophysiology of Spatial Selective Attention

• ERP and MRF Evidence – Voluntary visual attention

• N2pc (posterior contralateral) effect for visual conjunction search

Neurophysiology of Spatial Selective Attention

• Summary of ERP and MRF Evidence – Supports early-selection models

• Sensory information enhanced/attenuated by attention to spatial location

– Selection occurs at least as early as secondary sensory cortex

– Similar effects for both voluntary and reflexive attention

Neurophysiology of Spatial Selective Attention

• Functional Neuroimaging Evidence – Summary of PET studies of visual selective

attention

Neurophysiology of Spatial Selective Attention

• Functional Neuroimaging Evidence

• Attention control – Posner and Petersen's (1990) anterior and

posterior attention systems• Anterior - executive control• Posterior - spatial attention

Neurophysiology of Spatial Selective Attention

• Functional Neuroimaging Evidence – Jovicich et al. (2001) attentional load during

motion tracking• Parametric fMRI

– Additive factors type methodology that fits polynomial functions to the experimental manipulation levels (L)

– Brain Activity = L1 L

2 L3 + ...

Neurophysiology of Spatial Selective Attention

• Functional Neuroimaging Evidence – Hopfinger et al. (2000) spatial cueing study

• Event-related fMRI• Top-down attentional control

Neurophysiology of Spatial Selective Attention

• Animal Single-Unit Evidence

• Cortical activity and voluntary orienting– Moran and Desimone (1985)

• V4 neurons

– Wurtz et al. (1982)• Parietal neurons

Neurophysiology of Spatial Selective Attention

• Animal Single-Unit Evidence

• Subcortical activity and reflexive orienting

– Wurtz et al. (1982)• Superior colliculus neurons

Hemineglect

And Extinction

Neglect

Failure to acknowledge objects in the field

contralateral to the lesion, without perceptual deficit.

Extinction

• Failure to respond to stimuli in the contralesional field when presented simultaneously with an ipsilesional stimulus.

Patients with neglect may: • fail to dress the left side of their body• disclaim “ownership” of left limbs• not recognize familiar people presented

on the left side• scan only the right side of a dream• deny the illness  

Some studies observed that:

•Shifting visual field by 10o to the right eases the symptoms for some minutes

•Between 38% and 69% of patients recover within 3 months

•Extinction tends to persist longer

•Neglect deficit can be improved by increasing activation of the sustained attention system

Explanatory Hypotheses

• LOSS OF ABILITY TO ANALYSE SPATIAL PATTERNS– Neglect occurs only with lesion on the

right hemisphere.

• ATTENTIONAL DEFICIT– Single cell recordings in monkeys

indicate firing in posterior parietal cortex during attention tasks.

Explanatory Hypotheses

• Arousal– Each side of the brain has separate

activation mechanisms.

• Representational– Neglect results from inability to

form a representation of the whole space.

Explanatory Hypotheses

•Orienting –Each hemisphere operates attention shifting to the opposite direction in both hemispaces. Hemineglect results from damage in one hemisphere.

Posner et al. (1984)Interpretation:

Attention happens in 3 stages: 

disengagement

shifting

re-engagement

Posner et al. (1984)Conclusions:

1.Temporal-parietal lobe is involved in contralesional disengagement

2.Engagement to the new target may rely on frontal sites

Raffal and Posner (1987)

•Temporal-parietal junction e disengagement

•Midbrain e shift

•Thalamus e engagemant

EVENT TIME (msec) LOCATION

Eyes detect stimulus < 80 Primary visual cortex - occipital lobe

Preparation for focusing attention to target in the lateral visual field 80 - 100 Parietal-occipital cortex junction (P1)

Preparation for precluding attention to contralateral field

Preparation for saccadic movement to lock foveal vision into target 100 Meso-parietal + fronto-central

Attention to spatial frequency 120 (pick) Extrastriate occipital cortex (Nd2)

Selection + attention to frequency + orientation to new image 120 (pick) Posterior dorsal-medial cortex (Anterior P)

Attention to spatial frequency 130 (pick) Dorsal extrastriate occipital cortex (Pd)

RH - low visual frequency, LH - high frequency 150 (pick) Ventral extrastriate visual cortex (Broad selection N)

Preparation for focusing attention to target in the lateral visual field 160 - 180 Parietal-occipital cortex junction (N1)

Preparation for precluding attention to contralateral field

Discrimination of color and directional patterns 180 - 200 Parietal cortex (N2)

Discrimination of color and directional patterns + attention focus Occipital extrastriate + inferior temporal cortices (N2)

Selection + attention to frequency + orientation to new image 200 (pick) Posterior dorsal-medial cortex (N2)

Preparation for focusing attention to target in the lateral visual field 200 - 250 Parietal-occipital cortex junction (P2)

Preparation for precluding attention to contralateral field

Allocation of attentional resources to global features ~240 Right parietal temporal cortex

Allocation of attentional resources to local features of visual field Left posterior temporal cortex

Covert intention without saccadic movement to acknowledge 250 Lateral parietal cortex

object in contralateral visual field

Selection + attention to frequency + orientation to new image 265 (pick) Posterior dorsal-medial cortex (Anterior-medial N)

Maintenance of attention to stimulus in contralateral field 330 - 480 Lateral parietal wide region

+ saccade, gaze, and maintenance of focus

Resetting of system preparing for next shift of attention ~400 Parietal cortex

<80

80 - 100

100

120

130

150

160 - 180

180 - 200

200

200 - 250

~240

250

265

330 - 480

~400

Eglin et al. (1989)

Neglect victims perform poorly at

target detection on contralesional side, and performance

worsens with presentation of

stimuli to the ipsilesional side.

Neglect victims perform poorly at

target detection on contralesional side, and performance

worsens with presentation of

stimuli to the ipsilesional side.

Volpe et al. (1979)Neglect patients

can make ‘accurate’ same-

different judgments between stimuli in the intact versus neglected visual field, even when

they cannot identify the neglected item.

Neglect patients can make

‘accurate’ same-different judgments between stimuli in the intact versus neglected visual field, even when

they cannot identify the neglected item.

Grabowecky et al. (1993)

Target detection in the neglected field is enhanced by increasing stimuli in the same field.

Target detection in the neglected field is enhanced by increasing stimuli in the same field.

Neglect victims seem to process color, shape, and even meaning in the damaged hemifield, without ever

being aware of the stimuli.

Bisiach & Luzzatti (1978)

Conclusion:

Attention to material in visual-spatial memory is affected by damage in the parietal and posterior temporal lobes.

Behrmann & Tipper (1994)

Neglect can be locked to an object configuration and rotate with it.

Neglect can be locked to an object configuration and rotate with it.

Balint’s SyndromeInability to attend to two objects at the same time.

Difficulty establishing relationship between separate objects.

Inability to attend to two objects at the same time.

Difficulty establishing relationship between separate objects.