Week 8-Attention part 2 Flashcards

1
Q

What is the neuroscience of attention?

A

-Behavioural cognitive psychology is essential for the study of attention and has generated many testable hypotheses.

-Studies assessing Reaction Times and accuracy cannot fully describe the neural mechanisms of attention, as they depend on relatively independent measures of cognitive phenomena

-With the development of neuroscientific methods, we can understand what happens in the brain (i.e. at what time, at what intensity and at which level) when we direct the focus of our attention on certain stimuli (focus today is how attention affects sensory inputs in the brain?)

-Attention works by altering neural activity in sensory information/tasks (focus on target/suppress distracting stuff)

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2
Q

What is the Neural Representation Hypothesis?

A

-Representations are not created equally

-Neural representations of relevant sensory information are enhanced relative to representations of irrelevant sensory information (i.e., filters out distracting stuff)

Neural measures to assess indifferent ways the brain measures stimuli:
-Spike rate, local field potential
-Event-related potentials, spectral power
-BOLD signal (Blood)

-These all reflect neural representations of sensory information and thus can be used to assess attentional modulation

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3
Q

What is the Dual mechanism model?

A

Selective attention is accomplished through the interplay (i.e., working together) of two mechanisms (key to understanding attention):
1. Target Enhancement: enhancing (increase) neural activity associated with relevant information (makes sense as we want to pay attention to this)
2. Distractor Suppression: suppressing neural activity associated with irrelevant information (this is when we want to focus on something)

-Suppression may function as a compensatory mechanism to target enhancement

-Selective attention helps visual processing by enhancing the cortical representations of behaviourally relevant stimuli (targets) while suppressing the representations of irrelevant stimuli (distractors)

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4
Q

How does the brain control the modulation of brain activity to allow selective attention?

A

-There are specific sets of (higher level control) regions that control and coordinate attention modulation

-Involvement and interaction of such regions can be measured with neuroscientific techniques (fMRI, EEG, TMS..) and clinical observations (e.g. brain damaged individuals)

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5
Q

What occurs when the stimulus (target) is the focus of attention?

A

-There is an enhanced amplitude of sensory VEPs components, with very little change in waveform (latency) or scalp distribution. (Eason et al., 1969)

-First EEG study in this area (to see what happens in the brain in response to a specific event, averaging these points out)

-Wanted to see if there’s a difference in the peaks when someone is paying attention or not

-If the target is in an area where attention is not being paid to, it is still processed but there is a smaller peak (i.e., there is a difference in our brain amplitude waves in whether we pay attention or not)

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6
Q

What evidence is there for Target-related enhanced activity? (Hopfinger et al., 2000)

A

-fMRI evidence

-Spatial attention enhances activity in the visual cortex contralateral to the attended target

-Attention effects on target processing result from a gain-control mechanism that enhances the excitability of extrastriate neurons coding attended regions of visual space (shows that there’s increases in activity in the extrastriate cortex contralateral to the… CHECK RECORDING)

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7
Q

What evidence suggests Target-related enhanced activity is retinotopic? (Heinze et al., 1994)

A

-With bilateral stimuli in the upper visual field…

-Retinotopically enhanced activation not only contralateral to the target but also in the ventral part of the occipital cortex

-PET evidence

-Confirmed EEG - enhanced P1 amplitude contralateral to the target

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8
Q

What evidence suggests evidence for Multiple Spotlights of Attentional Selection? (McMains et al., 2004)

A

Hypothesis+predictions:
-Testing a single spotlight moving in a visual field but what if there are more than one?
-Zoom lens type of attention (a little to the side or both needed) OR you split it e.g., one spotlight on one thing and something for the other

Procedure:
-Attend 1 task P’s was asked to find the word or something different from the rest of stimuli. Attend 2 P’s asked to pair same stimulus on the screen (recording brain activity)

Findings:
-Evidence for enhanced activation of the multiple spotlights of attention (or split focal attention) model
-Found attention is split into multiple parts and where P was attending to saw the visual activation
-Shows attention works as a multiple spotlight otherwise you’d see activation everywhere rather than where the person is looking to

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9
Q

What evidence suggests there is attention activity in the Lateral Geniculate Nucleus (LGN)? (O’Connor et al., 2002)

A

-Spatial attention modulates activity as early as the
Lateral Geniculate Nucleus.

-The LGN, traditionally viewed as the gateway to
visual cortex, may also serve as a ‘gatekeeper’ in controlling attentional response gain.

-Found that at early stages of LGN (before info gets sent for higher processing) there is enhanced activation for the object you want to pay attention to AND for what you are trying to suppress (i.e., distract away from focus)

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10
Q

What evidence suggests attention modulation for nonspatial features? (Anllo-Vento et al., 1998)

A

-Stimulus always at the same location where the task is to attend to colour e.g., red or blue

-Found you get this peak of the EEG when you are attending to colour (i.e., other features) regardless of whether the object appears

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11
Q

What evidence suggests attention modulation for nonspatial features? (Craven et al., 1997)

A

-The medial superior temporal part of the brain are sensitive to coherent motions of dots (i.e., moving dots)

-P’s presented with stationary black dots and white motioned dots moving towards fixation cross and asked to look at just one to shift attention (recorded level of activity in V5)

-Every time they attended to moving dot there was enhanced activity whereas for stationary one there was evidence of suppression activity

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12
Q

What evidence suggests that there is evidence for attention modulation on object processing? (Wojciulik et al., 1998)

A

-Object-Based attention. Covert attention modulates face-specific activity in the human fusiform face area (FFA)

-Dependent on trial, they were asked to match the houses, bars or faces for similarity

-If attention was directed to faces, FFA was very responsive to this. If attention was directed to house the para (CHECK RECORDING FOR NAME)

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13
Q

What Evidence is there for Target Enhancement & Distractor Suppression in the FFA? (O’Craven et al., 1999)

A
  • FFA and PPA show greater signal when the area’s preferred stimulus was attended
  • FFA and PPA show greater response to preferred stimulus when it was the irrelevant attribute of the
    attended object
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14
Q

Two- Attention-Systems Model of Attention Control: What areas are involved in the Dorsal Attention System? (Maurizio et al., 2002; Vossel et al., 2014)

A
  1. FRONTO-PARIETAL NETWORK: (including Dorsal – Medial Prefrontal Cortex and intra-Parietal Sulcus-located in the parietal lobe)
  2. TOP-DOWN CONTROL: Attention is controlled by the individual’s expectations, knowledge and goals. aka ENDOGENOUS ATTENTION
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15
Q

Two- Attention-Systems Model of Attention Control: What areas are involved in the Ventral Attention System? (Maurizio et al., 2002; Vossel et al., 2014)

A
  1. TEMPORO-PARIETO-FRONTAL NETWORK:(including Temporo-Parietal Junction and Inferior Frontal Cortex, IFG IFJ)
  2. BOTTOM-UP CONTROL: Attention is driven and triggered by an unexpected, and potentially important, stimulus (e.g., a waiter smashing a glass) aka EXOGENOUS ATTENTION
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16
Q

What does the Two-Attention-Systems Model demonstrate?

A

-Demonstrated bilateral organization of the dorsal system (both hemispheres involved in attentional control mediated by pathways)

-Potential right lateralization of the ventral system (possibly evolutionary explanations)

-VFC (inc. inferior and middle frontal gyrus) play a key role in the flexible interplay between the two

Areas involved:
FEF = frontal eye fields = (part of Middle-Dorsal Prefrontal Cortex) (Dorsal)

IPS = intraparietal sulcus (Dorsal)

VFC = ventral frontal cortex (inc. inferior frontal gyrus/junction, insula) (Ventral)

TPJ = temporoparietal junction (Ventral)

V = visual cortex (Visual)

17
Q

How does the Two-Attention-Systems Model work from an anatomical point of view? (Maurizio et al., 2002; Vossel et al., 2014)

A

-Dorsal and ventral networks are anatomically segregated cortical systems (no overlap) with functionally specialized nodes promoting specific processes for attentional control.

-BUT they don’t control attention in isolation (i.e., don’t work in isolation)

-Flexible interaction between both systems enables the dynamic control of attention concerning top-down goals and bottom-up sensory stimulation.

18
Q

What is activated in the Two-Attention-Systems Model? (Maurizio Corbetta, 2002)

A

-Preparatory activation (in response to a spatial attention-directing endogenous cue) of sensory cortices during attention control.

-A Ventral Parieto-Frontal system is activated in response to sudden stimulus onset (a very exogenous orientation)

-Evidence from attention reorienting after rare invalid targets vs. frequent valid targets.

-Right Temporo-Parietal Junction is more strongly activated by invalidly than validly oriented cues – Indicates

19
Q

What is Unilateral neglect also called?

A

-Hemi-inattention
-Visual neglect
-Visual spatial neglect
-Unilateral spatial neglect

20
Q

Define Contralesional

A

The opposite side to brain damage

21
Q

Define Ipsilesional

A

Same side as brain damage

22
Q

Define Neglect

A

“Following right hemisphere brain damage a patient without impairment of intellectual functioning appears to ignore, forget or turn away from the left side of space- as if that half of the world has ceased to exist…” - Mesulam, (1985, as cited in Robertson and Marshall, 1993)

-Neglect typically occurs following damage to the right hemisphere, causing neglect in the left hemisphere/side

23
Q

Brain (1941): What was found in patients with right parieto-occipital damage

A

Case 5:
“When asked to describe how she would find her way from the tube station to her flat she described this in detail correctly and apparently visualising the landmarks, but she consistently said right instead of left for the turnings except on one occasion.”

-Example of how patients with neglect work in route-mapping tasks (always turn right)

24
Q

What did Paterson & Zangwill (1944) find with Cases with missile wound damaging the right parieto-occipital region? (including angular gyrus)

A

Case 1:
“The patient often collided with objects located on his left which he had clearly perceived a few moments before. He was liable to knock over dishes on his left-hand side and occasionally missed food on the left-side of his plate.” (i.e., left-hand side doesn’t exist in their world)

Case 2 (right parietal damage):
“It was noticed that the patient totally neglected his left upper extremity (of his own body) despite good preservation of motor power”

25
Q

What causes Neglect?

A

-It is most commonly caused by a stroke

Stroke – Affects ~ 150,000 people in UK each year

-Blood supply to part of brain is cut off resulting in damaged tissue (blood blockage usually occurs in middle cerebral artery)

26
Q

What is the nature of brain damage associated with neglect?

A

Areas involved in neglect:
-Posterior parietal cortex (Specifically Inferior parietal lobe)
~Brodman’s areas 39 and 40 (dorsal ‘where’ visual pathway)
~Left parietal damage rarely produces right sided neglect (and quickly recovers)

27
Q

What sub-cortical areas are responsible for neglect?

A

-Thalamus, basal ganglia, white matter

-The right parietal cortex appears to play a dominant role in spatial cognition in humans

-Most commonly the right inferior parietal lobe

-This is an attentional deficit, not a sensory deficit e.g., caused by lesions in the visual cortex - blindness

28
Q

How are the right hemisphere areas associated with neglect?

A

-Heterogeneous condition in which the brain areas involved vary considerably across patients.

-The main areas damaged are typically in the right hemisphere

-The attentional problems of neglect patients depend on brain networks (i.e. connected brain areas)

T-he region most commonly affected is in the right inferior parietal lobe – superior temporal gyrus, the inferior frontal gyrus, the insula, the supramarginal gyrus and the angular gyrus (Corbetta & Shulman, 2011).

29
Q

How did Vallar & Perani (1986) investigate neglect?

A

-Superimposed brain images of patients with brain damage

-Right inferior parietal lobe most associated with neglect

30
Q

What are the functions of the Posterior Parietal Cortex (PPC)?

A

-Responsible for Visuo-motor control of behaviour

Single cell recording shows these neurons involved in:
-Visually-guided reaching, Eye movements, Head (gaze) shifts

Effects of lesions to PPC in humans:
-Mis-reaching (optic ataxia)
-Eye movement problems (fixed gaze)
-Constructional apraxia (difficulty putting things together)
-Simultanagnosia (inability to perceive more than one object at a time)
-Neglect (ignoring the left side of space)

31
Q

What are some things patients with neglect may experience?

A
  1. Eat food on the right hand side of plate only
  2. Dress only the right side of own body
  3. Shave the right side of their own face
  4. Deviate to right and may even go around in a circle
32
Q

What is Spatial Neglect? (Karnath, 1994)

A

-Dissociation in eye movement behaviour

-Scenes chosen to guide (top-down) active search of left side

-Eye movement scan path rarely to the left hand side (i.e., don’t really look to the left)
~Failure to scan left side of scene (spatial neglect) DESPITE normal eyesight

33
Q

What is Subject-Centered (Egocentric) Neglect?

A

-When patients try to put a mark through a horizontal line at its centre (line bisection task: give someone different lengthened lines to mark the middle of the line), they typically put it to the right of the centre.

-Patients can see stimuli in the left visual field – they simply tend to ignore them, not to notice them

34
Q

What is Object-centred (Allocentric) Neglect? (Driver & Halligan, 1993; Marshall & Halligan, 1993)

A

-This involves a lack of awareness of the left side of objects rather than simply the left side of the visual field (asked to copy objects but only draw the right-hand side)

-Not clear whether object- and subject-centred neglect reflect similar or different underlying disturbances to the attentional system

35
Q

What is the outcome of drawing a clock for those with neglect?

A

Not only limited to visual stimuli, but also neglect of left side of visual imagery and memory (e.g., drawing a clock from memory)

36
Q

What’s extinction?

A

-The phenomenon involves a failure to detect a stimulus presented to the side opposite the brain damage (contro-lesional field) when a second stimulus is presented to the same side as the brain damage (ipsilesional field) simultaneously

-The competition elicited by the two stimulus inputs on both sides, is dominated by the right visual field, which “extinguishes” the input from the left

For example, someone taps them on either shoulder and asks which side, left side is acknowledge when separately done but not when both shoulders are tapped

37
Q

What’s Balint’s Syndrome?

A

Bilateral damage to the dorsal posterior parietal and lateral occipital cortex leads to an attentional deficit called Balint’s Syndrome.

38
Q

What are the 3 main symptoms of Balint’s syndrome?

A
  1. Simultagnosia: inability to attend and/or perceive more than one object at the same time
  2. Optic Ataxia: an impaired ability to reach for or point to an object in space under visual guidance
  3. Oculomotor Apraxia: a difficulty to voluntarily direct eye gaze towards
39
Q

What did Cooper & Humphreys, (2000); Humprheys & Riddoch, (1993) find with Simultagnosia in Balint’s Syndrome?

A

-Deficit lies in the inability to detect multiple objects rather than an inability to attend to multiple qualities (features)

-Similarly, participants are better than chance at comparing the length of two bars if these are connected as part of the same object