Topic 4 - Attention + Attention Disorders

What does illusory motion and objects activate?

Same parts of brain as real motion + objects (like obj recog, V4)

enigma illusion (motion in circles) → V5/MT

bistable stim (switching figures) → vision + nonvision areas, TMS of R parietal (suppressed; affects rate of switch)

Attention

The process by which certain info is selected for further processing + other info is discarded; A mechanism for the selection of info

May be req to bind together dif aspects of conscious perception (ex. shape + color, sound + vision)

Limited Capacity Purpose

To process all received info, so selection based on relevance or importance to current goals

Spotlight Metaphor 

Attention tends to be directed to locations in space (which is a common dimension of dif sensory systems + our motor system)

The spotlight can move location (ex. visual search) + zoom in/out

Location of attention NOT necessarily the same as location of eye fixation (ex. looking out corner of eye)

Can split attention between 2 nonadjacent locations

Inattentional Blindness

Failure to notice an unexpected object or event bc you are paying attention to something else

Ex. Ball pasess + gorilla

Change Blindness

Failure to notice an important change in a scene even if we are actively looking for it

Exogenous Orienting

Controls the spotlight; Attention is externally driven by stim

Stim outside body attracts attention 

Endogenous Orienting

Attention is guided by the goals of the perceiver

Directed from the inside by goals of perciever 

How does obj based attention work? 

Dif parts of the visual ventral stream light up depending on attention target 

Ex. Building —> Parahippocampal place area (PPA)

Ex. Man —> FFA

Attentional Blink

Time based attention; Refractory period after expected target reached before attention “restarts)

Neural Bases of Attention

1. Ventral Prefrontal (VFC)

2. Superior Prefrontal (FEF)

3. Posterior Parietal (LIP)

4. Temporal-Parietal Junction (TPJ)

5. Superior Colliculus

6. Pulvinar of Thalamus

right hemi

Parietal Lobe

Specialized for spatial processing (where); Dorsal stream 

Represents full visual field (unlike earlier regions) but in a graded fashion (right parietal → left visual field bias + etc)

Integrate dif spatial representations needed for action (eg. visual space with body space) → how 

Lateral Intra-Parietal Area (LIP)

Has

• Motor properties (generades saccades)

• Sensory properties (sound, vision; enables sound based coordinates to be remapped to eye centered coordinates)

• Resp to both endogenous + exogenous attention

May contribute to salience map (natural tendency to be drawn to left)

Motor Properties in LIP

Generates saccades

Sensory Properties in LIP

Sound, vision; Enables sound based coordinates to be remapped to eye centered coordinates 

Remapping of sound based (ear/head) to eye centered 

Proof that LIP is important in attention

1. Single cell data from monkeys (spareseness; doesnt resp equally to all sensory stim, resp more to unexpected stim; enables covert + overt orienting with/without eyes; codes a spatial salience map with the left + right hemis having dif biases

2. Human fMRI data (orienting cues like an arrow activate LIP + frontal eye field FEF involved in saccades even if no overt motor resp; similar network involved in obj based attention)

2 Dorsal (where) attention routes

1. Dorso-Dorsal Route

2. Ventro-Dorsal Route

Dorso-Dorsal Route (Dorsal Attentional Network; DAN)

Lateral intraparietal (LIP) + frontal eye fields (FEF); Dorsal attentional Network

Controlled goal directed attention (strategic + voluntary orienting attention to visual targets) WITH BILATERAL REP; Strategic + voluntary orienting of attention to visual targets

Orienting in a salience map (eg. from cues)

2 Dorsal (where) attention routes

Ventro-Dorsal Route (Ventral Attentional Network; VAN)

Temporal parietal junction (TPJ) + ventral prefrontal cortex (VFC)

Grabbed stimulus driven attention (unexpected and automatic orienting of attention to visual targets) + MORE RIGHT LATERALIZED; Unexpected + auto orienting of attention to visual targets

Acts as “circuit breakers” + redirects attention away from current focus of processing (ex. detecting targets; avoiding attention being drawn to incidental events)

2 Dorsal (where) attention routes

Right Parietal Visual Field Bias

Left visual field bias 

Left Parietal Visual Field Bias

Right visual field Bias

Damage to Right Parietal Lobe

More profound effects; greater neglect + attentional blink

Saliance Map + LIP

Natural tendency to be drawn to the left

Right TPJ

More important in attention than left

Right Posterior Parietal

Disrupts salient

Left Posterior Parietal 

Disrupts nonsalient 

Right LIP

Attend salient stim

Left LIP

Attend to nonsalient stim

Awareness

An outcome (a conscious state) thats linked to attention

Perception

The info thats selected + forms the content of awareness

3 Theories of Attention 

1. Feature Integration Theory (FIT)

2. Biased Competition Theory

3. Premotor Theory of Attention 

Feature Integration Theory (FIT)

Perceptual features (eg. color, line orientation) are encoded in parallel + prior to attention

Ex. Can detect a blue T if it has a unique perceptual feature without attention (pop out) BUT without a unique feature need to do a serial search

3 Theories of Attention 

Biased Competition Theory

Attention is an emergent property of many neural mechanisms working to resolve competition for visual processing + control of behav

Competition occurs at mult stages rather than a fixed spotlight (ventral stream feature lvl: like V4 resp to 2 colors less than sum; top down effects: more receptive field activation for consciously attended things)

Competition is both serial + parallel

• Parallel at most stages

• Serial at motor output stage (saccade)

3 Theories of Attention 

Premotor Theory of Attention

Attention is just prepping for an action

Covert attention 

Covert Attention

An action plan (eg. a saccade) thats prepped but not executed

When does shifting attention get easier?

When it just req modifying an existing saccade than when it req making a new saccade

Spotlight theory predicts equal difficulty since same difficulty

Hemi Spatial Neglect Def

Failure to notice or respond to stim on one side of the body of environment that is contralateral to brain lesion (contralateral)

Caused by acquired damage to parietal lobe 

Hemi Spatial Neglect Cause

Acquired damage to parietal lobe (esp right parietal)

Hemi Spatial Neglect Symptoms

On opposite side of lesion

• Ignoring obj, ppl, or events on affected side

• Failing to dress/groom affected side of body

• Eating from only 1 side of the plate

• Reading only from 1 side of the page

• Difficulty with spatial orientation + navigation

• Unilateral Anosognosia

Unilateral Anosognosia 

Lack of awareness of their own deficit 

Hemi Spatial Neglect Symptoms

What side is hemispatial neglect usually on?

Left side

What side are lesions associated with hemispatial neglect usually on?

Right parietal lobe

Lesion to right inferior parietal lobe (angular gyrus, TPJ) causes what? 

Cause more severe clinical neglect than equiv lesions on the left 

Why are hemispatial neglect lesions on the left more severe?

Right parietal more specialized for global processing + left parietal more specialized for local processing

Dif between hemineglect and heminopia 

Hemineglect → dont know they cant see half 

Heminopia → primary sensory deficit; cant see 1 side + they know it, so they turn their heads a lot 

Heminopia 

Primary sensory deficit, they cant see one side and they know it 

Try to turn head a lot to try and see

What parts of their brain do neglect patients still activate?

Visual regions in the occipital lobes that they claim not to be aware of

Proves that this is an attention prob and not vision

Can neglect patients often detect objects if cued to the neglected side?

Yes

What does neglect affect? 

Auditory + tactile awareness as well as vision

Ex. Sounds on left are mislocalized but still heard

What does visual extinction suggest for neglect?

That dif perceptual representations are competing for attention + visual awareness

Spaced Based (Egocentric) Neglect

Fail to attend to objects on the left side of space

Lesions are more DORSAL (higher)

Object Based (Allocentric) Neglect

Fail to attend to left half of the object, irrespective of obj’s position in space 

Lesions are more VENTRAL (lower)

Relationship between space based (egocentric) + object based (allocentric) neglect

Double dissociation

Where are the lesions for egocentric neglect?

More dorsal (higher)

Where are the lesions for allocentric neglect? 

More ventral (lower)

Personal Neglect

Neglecting left body parts

Also dif; a dif pattern

What happens to Neglected info?

Ventral route (VAN) may process the neglected objects up to the stage of obj recog + possible semantics

Degraded line drawings presented in neglected field showing priming effects when attended

Burning House Experiment 

2 houses that are identical on nonneglected side, but 1 house is in flames on the neglected side 

Patient says the 2 houses are identical but would consistently prefer the nonburning house so must process left side on some lvl 

Egocentric Tracing Task (tracing a picture)

Neglected whole left face + parts of the left side of right face

Allocentric Copying (copying an image)

Neglected left sides of the left face + right face

Are egocentric v allocentric task dependent? 

Yes

Relationship between Personal Space + Near Space Neglect

Double dissociation

Personal (Body) Neglect

Failure to groom left side of body or notice position of limbs

Patients with this can sometimes search near space

Near Space (Peripersonal) Neglect

Visual search of array of external objects

Near Space

Tested with line bisection using pen + paper

Far Space

Tested with line bisection using proj image + laser pointer

If a patient is given a long stick then the near deficit extends into far space

Extinction 

Some left neglect patients may not notice two objects together but will notice when they are alone; Object in 1 visual field suppresses awareness for objects in other visual fields

Suggests attention involves competition b/w stim

How to test Visual Fields

1. Test left hemifield by raising right fingers

2. Test right hemifield by raising left fingers

Patients with lesion will not see fingers contralateral to lesion

How to test for Extinction

1. Wiggle right fingers

2. Wiggle left fingers

3. Wiggle both

Patients with lesion will not see fingers contralateral to lesion

Testing for Simultagnosia

1. Hold up a single obj; Patient can say what it is

2. Hold up another single obj; Patient can say what it is

3. Hold up 2 obj simultaneously; Patient says they only see 1 obj

Simultangagnosia

Inability to see more than one object WITHIN a visual field; Can recog single obj but not multiple obj

They CAN group sev parts into wholes if they share color, shape, or are “connected”

Ex. Can see two circles if told they are eyes, but not if they are not told that (face like features)

Dorsal v Ventral Simultagnosia 

Dorsal → only 1 obj at a time 

Balint Syndrome Def

Bilateral occupital parietal damage centered in the angular gryus

Normal + basic vision but lack explicit spatial awareness

• Difficulty locating an item that they can percieve

• Difficulty telling when an item is moved towards or away from them

• Difficulty at localizing sounds

But CAN say which side of body + which body part is touched

Clinical Triad of Balint Syndrome

1. Simultanagnosia

2. Optic Axia

3. Optic Apraxia

Optic Ataxia 

Cant reach for an object under visual guidance 

Clinical Triad of Balint Syndrome

Optic Apraxia

Fixation of gaze without a primary deficit of eye movement

Clinical Triad of Balint Syndrome

Attention Process

Sensory Memory → Attention → STM/discard

Fast + mostly unconscious 

Saccade

Smooth pursuit

What side/part of the brain are lesions that caused neglect associated with?

Right inferior parietal lobe

What region has the highest overlap for neglect? 

Right angular gyrus + right tempoparietal junction (TPJ)

What is the most consistently damaged region for neglect? 

Right Ventral Attentional Network (VAN) (esp TPJ)

Temporal Parietal Junction (TPJ) has what in it?

Inferior parietal lobe (IPL) + superior temporal gyrus (STG)

Ventro-dorsal

Ventral Prefrontal Cortex (VPFC) has what in it?

Inferior frontal gyrus (IFG) + middle frontal gyus (MFG)

Ventro-dorsal