CLPS0450 - Disorders of Attention

Attention is not a single ______.

entity

- attention is a set of processes that interact with other processes in the performance of different perceptual, cognitive, and motor tasks.

Why do we need attention?

- We have a limited capacity to process all information.

- We are selecting which to pay attention to based on current goals.

The selective filter allows us to only have certain responses enter _______.

consciousness

early selection

We filter information out very early in the attentional pathway (never processed anything you weren't attending to)

ex) censoring out any other sensory stimuli early on (words = gibberish)

late selection

all incoming information is processed up to the level of semantic meaning before being selected for further processing

- kind of listening and having words processed up to certain point and then having that affect your consciousness when it catches your attention

T/F: attention location might not necessarily be the same as where eyes are fixated.

True (Covert)

Describe 3 points on how the spotlight metaphor applies to spatial attention.

1. They can move from one location to another

2. Can zoom in and out/have a narrow or wide beam

3. attended location is not always where eyes are fixated.

Spatial attention is critical for...

binding different features into unified representations

Ventral route examples

- "what" an object is

- details that help us recognize the object such as shape, color, texture

Dorsal Route

- "where"

- spatial processing; direct movement/action

- more coarse structures > details

T/F: Pop-put search showed constant reaction time regardless of the set size.

True

Does pop out search or conjunction search require increasing reaction time? why?

Conjunction Search;

- you're looking for "blue T" because you have to bind two features, color (blue/red) vs. shape (T or L) instead of Pop-put search, which only requires you to sort out the color.

- we have to serially search (attention is limited)

What binds features?

attention

what does the saliency map show?

The parietal lobe's ability to allocate spatial attention to integrate/bind visual information. ex) binds "what" with "where" (multiple features)

what is re-entrant feedback?

Going backwards from dorsal -> ventral stream to conduct feature binding. (top-down)

Damage to _____ stream -> cant perform Object Discrimination

ventral

Damage to ______ stream -> can't perform Landmark Discrimination

Dorsal

Landmark discrimination

requires dorsal stream to come up with spatial relations. In this task you train monkeys to choose an object close to the cylinder rather than requiring them to discriminate between objects.

Agnosia is related to ______ discrimination.

object

- they can tell you where the objet is in the space, but not where it is.

Balint's syndrome is related to damage in ____ stream and ________ discrimination.

Dorsal; landmark

3 hallmark characteristics of Balint's Syndrome

Simultanagnosia, Optic Ataxia, Ocular Apraxia

simultanagnosia

inability to perceive multiple visual objects at once or their spatial relations

signs: the second object introduced will be ignored

cheat: can activate stored object representations in ventral stream to access within-object relations

T/F: accessing object representations code for within-object spatial relations is the reverse of re-entrant feedback supporting DORSAL feature binding

false; it's the reverse of ventral feature binding, since in this case, he's accessing ventral FIRST then going back to dorsal. (patient GK)

optic ataxia

inability to perform coordinated voluntary movements when reaching for an object

- difficulty using visual input when reaching for something

Optic ataxia and agnosia have double dissociation because

two separate pathways: perceptions vs. motion. Agnosia vs. optic ataxia patients have OPPOSITE defects.

- agnosia: dorsal pathway intact ; ventral pathway damaged (perfectly well at coordinating movements despite not knowing what they're looking at)

- Optic Ataxia: able to perceive the bar, but cannot coordinate movements.

The task is to 1) pick up the object and 2) mime its width. Balint's syndrome patients would show error in which step?

1 (motor coordination)

ocular apraxia

- can't move away from fixation of gaze

- can't move eyes voluntarily to points in visual field

- sticky fixation

sticky fixation

failure of disengagement from a fixated object

chaotic fixation (ocular apraxia symptom) shows not as selective to ______ _______ information.

semantically meaningful

- very unorganized, random movement of eyes around the object

- gaze is captured by irrelevant stimuli

what happens to feature binding with bilateral parietal damage and dorsal stream? (patient RM)

people perceive a stimulus that does not exist.

Patient RM experiment

There were 3 feature binding conditions (red x, green T (color + shape), x going up/down, T going left/right (motion + shape). He had damaged feature binding, so he kept borrowing feature from its neighbor. For instance, he would match wrong things like "I saw red T and green x" because he only saw one stimulus.

T/F: In Balinte's syndrom patients (damage to dorsal stream), we can still reorient their attention by shifting the ventral stream amd facilitate spatial localization.

False. The first part of this statement is true, but not the second one. Patient GK, despite the ability to shift spatial attention to the location of strong group, he was unable to localize the selected target.

Neglect syndrome is seen in patients with (right/left) parietal damage, and they neglect the (right/left) side of visual space.

(usually) right; left

T/F: when extreme, neglect patients may fail to recognize contralateral extremities as their own.

True (body parts)

T/F: neglect patients can't process anything in their bad field.

False! They can process whatever's on their bad field as long as nothing is in their good field. Once competition occurs, they forget about the object in bad field. This prioritization of "good" field is called extinction.

anosognosia

neglecting of any deficits; patients are not aware of their deficits

hemiakensia

tendency to not move one side of your body

motor extinction

you will move the bad arm, but once you move the good arm, you will stop moving the bad arm

allethesia

tendency to mislocate things in space

T/F: Hemineglect = hemianopia

False! Hemianopia refers to loss of vision in one visual field, not negelct.

hemifields of neglect are separated by _____ ____, not line of fixation.

body axis

- even if a neglect patient moves their eyes to the left, they will neglect the same left side as before. But if a hemianopic patient moves their eyes, the visual field they're able to see vs. not will shift accordingly.

what did Tactile maze experiment show?

neglect is not affected by sensory/motor loss. It's more of higher order processing issue.

T/F: In the tactile maze experiment, the neglect patients with lesion on right side were completely fine when using their right hands since neglect affects the contralateral side.

False. They showed typical neglect symptoms where they spent significantly more time on the neglected side despite which hand they were using. (ex. when lesion was on the right side, they spent more time searching for the marble on the left hemifield) IF this was a tactile issue, they shouldn't have any trouble finding the marble with their right hand unrelated to where the marble is located in.

T/F: objects in neglected space activate appropriate visual regions in occipital lobes.

True! Neglect patients have perfectly intact visual system.

examples of neglect not being sensory/tactile disorder (against primary sensory disorder theory)

- tactile maze

- objects in neglected space can active occipital lobes visual region.

- visual extinction & presence of competition

- burning house experiment

Burning House experiment showed _____ vs. ______ awareness of visual scene, and proved that neglect is a higher order disorder.

conscious vs. unconscious. Neglect patients were shown a normal house and a burning house. They were able to describe both houses as "a house" but did not see anything wrong with the burning house. However, they chose the normal house as the house they'd wanna live in despite not consciously knowing the difference. This showed that the ventral stream was able to identify the house, but they did not consciously see the burning house. (processed in brain, but not in the mind)

Theories of Neglect

1. Primary Sensory Disorder

2. Attentional Disorder

3.Representational Disorder

Riddoch & Humphreys showed that Neglect patients are good at _______ orienting, but not _______ orienting

Good at automatic (exogenous) but not deliberate (endogenous); they are bad at automatically shifting attention to the external cue.

In the Covert orienting of attention, where is the competition occurring? Why is neglect occurring?

Competition between hemispheres to control attention in its contralateral space. There's neglect in left side during invalid cues because of an imbalance in competition.

Explain the experimental set up of covert orienting of attention.

Black, thick rectangle is the "cue" that can automatically capture the attention. Black dot is the endogenous "target" that requires shift of attention to recognize. In the "valid cue" setting, square & dot are in the same side (left). This requires engage & shift of attention to cued location then responding to target. In "invalid cue", black squre is on the right and dot is on the left. This is an additional step for invalid cues, which is why invalid cue's reaction time is longer. This also showed that neglect patients lack automatic cues.

Those with right side damage were unable to disengage from invalidly cued _____ hemisphere.

right

neglect patients were not able to shift attention from ? This indicates what about the competition?

right invalid cue to left target

- indicates that for neglect patients it didn't matter if new cues show up on the other side because attention cannot switch. Their left will always lose to their right.

While both left and right hemispheres can cause neglect, only ____ hemisphere lesions cause severe deficits. Explain why.

right (left neglect is more frequent than right side neglect); right hemisphere is more dominant in allocating spatial attention.

Standard theory of neglect: how is left hemisphere damage compensated?

- right hemisphere controls shifts of attention to both left and right space.

- left hemisphere controls attention to only right space.

- left hemisphere damage can be recovered by right hemisphere, since it controls attention in both spaces (including the damaged right space)

T/F; From what we know about standard theory of neglect, brain network mediating spatial attention is asymmetrical and damaged in neglect.

False! no clear evidence for either. Instead, spatial neglect might be due to asymmetry of a nonspatial attention system.

nonspatial attention network is...

- automatic stimuli (salient/unexpected)

- interrupt what we're attending to

- more dominant in right hemisphere

- actually asymmetrical

T/F: spatial attention network is voluntary (conscious)

true

(voluntary/automatic) system gets damaged in neglect patients.

automatic

source of deficit (neglect) is in the _____ network, which is asymmetrically more represented in ______ hemisphere.

alerting; right

T/F: nonspatial (ventral) activation can help overcome spatial neglect.

True

The Piazza de Duomo study showed Neglect as a _______ disorder. How? What did the patients say?

- representational disorder

- they asked the patients to describe what they see from two perspectives. Second time, they couldn't describe what they had just described in the first trial. This showed that neglect can't be a memory deficit or an attentional deficit.

Piazza de Duomo: deficit is the construction of the ______ _________.

mental representation

T/F: neglect patients in Piazza de Duomo study were aware of their deficit, since they noticed that the side they couldn't describe was seen in the first trial.

False

If the neglect was an attentional disorder, presence of slit on the cloud image (will/will not) get rid of the neglect deficit.

will (bc left/right side doesnt matter with the slit)

- on the other hand, if neglect is representational deficit, their performance will still be bad (said 2 clouds look the same even though their left sides were different).

What did cloud study indicate?

Since the patients neglected left side with or without the slit, neglect had to be a representational deficit.

In the brain, numbers and number line are represented ___________.

pseudospatially

In the Mental Number Line test, they tested neglect patients by asking them to define the mindpoint number. What did they do?

They had displacement error WRT the midpoint, towards their "good" field (right field). This showed that we represent numbers pseudospatially and implicitly, and this number line can be skewed.

Mental number line is another example of neglect being a __________ deficit.

representational

__ is almost always observed in association with __. why?

RN; PN

- involvement of visuospatial memory

- RN is caused by a deficit in interaction btwn working memory and attention. PN is ONLY caused by deficit in attention. (higher likelihood of impaired PN, intact RN)

Define perceptual neglect & representational neglect

perceptual neglect (attentional): unable to attend to visual, auditory, olfactory stimuli in the contralesional side of the perceptual domain.

Representation Neglect: unable to represent or describe the contralesional side of their mental image.

T/F: neglect patinets can neglect the "left side" of time.

True! another evidence that neglect is representational. they recalled "future" more than "past" since they correlate future with the right (functioning) side.