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Attention Everyone knows what attention is. It is the taking ...
Transcript of Attention Everyone knows what attention is. It is the taking ...
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.