Lecture 31: Neurobiology of Attention and its Disorders

What are the different forms of attention?

• vigilance

• selective attention

• spatial attention

What is the most simple form of attention?

vigilance

What is vigilance?

heightened arousal to all incoming stimuli

What is selective attention?

dedicating neural resources to an incoming stream of information

What are the two examples of selective attention discussed in lecture?

• basketball

  • students are passing around the ball, and some people are so focused on counting how many passes that they miss the gorilla walking across the screen

• cocktail party affect

  • when someone hears their name, they listen intently to the conversation where they were referenced

Which test is utilized for spatial attention?

the Posner task

Regarding the Posner task, what changes and what doesn’t?

unchanged:

• visual transduction

• motor coding

• muscle activation

changed:

• visual processing is faster

What type of process is attention?

a top-down process

True or False: Different neural systems mediate different types of mediation. Attending to one type of stimulus necessarily limits our ability to attend to others.

true

True or False: Our sensory systems are highly sensitive to differences—causing a pop-out effect.

true

How is non-spatial attention assessed?

continuous performance tests for vigilance and selective attention:

• simple vigilance

  • “press the button when you see an X”

  • speed of letters going by varies

• working memory

  • “press a button when you see any letter immediately repeat itself”

• inhibition (impulse control)

  • “press the button to every letter except X”

What is the Stroop test assessing?

response inhibition (hypervigilance)

What is poor performance on the Stroop test associated with?

with poor selective attention

Which disorder is the Stroop test impaired in?

ADHD

What is the Stroop test?

a classic experiment that measures how conflicting information affects attention and cognitive control; it asks people to name the color of the ink a word is printed in, rather than reading the word itself

What is egocentric neglect?

a type of spatial attention disorder where a person fails to notice or respond to stimuli on one side of space, relative to their own body

What is allocentric neglect?

a type of spatial attention disorder where patients ignore one side of individual objects, regardless of where those objects are located in space

Which anatomical arousal systems is simple vigilance associated with?

• ascending reticular activating system

• midline thalamus

• mesial PFC (though all of the cortex may be modulated by arousal)

What are the most common disorders associated with simple vigilance?

• midline glioma

• midline meningioma

• delirium

What does a lesion to the medial PFC cause?

“lights are on but nobody’s home”

What are the biochemical markers of arousal?

• acetylcholine

• norepinephrine

• dopamine

Describe the functional imaging of attention.

• task: fixate at the center point while attending to a particular sector

• attentional effects are observable in V1 (and some higher cortical areas)

• location of “hot spots” in V1 shifts accordingly when attention does

What is the main controller of selective attention?

the dorsolateral prefrontal cortex (DLPFC)

What is the main executive of the brain?

the DLPFC

Where does the DLPFC project?

multiple brain regions

True or False: Neurons in the DLPFC remain active during “delay times”.

true

What do lesions in the DLPFC imapir?

• selective attention

• impulse control

• working memory

Describe the test for attention to specific stimulus features.

• task: same-different discrimination

  • fixate center point, compare two brief movie clips, push a button if they differ

• selective attention experiment:

  • attend to one specific feature, push a button if that feature changes, ignore other changes

• nonspecific attention experiment:

  • attend to all features simultaneously, push a button if anything changes

• subtract B from A to look for attentional enhancement associated with one specific stimulus feature

Which stimulus features change in the attention to specific stimulus features task?

• color

• shape

• speed

Where are attentional effects of color and shape observed?

• areas V4

• inferotemporal cortex (what pathway/ventral cortical system)

Where are attentional effects of motion speed observed?

middle temporal area (where pathway/dorsal cortical system)

Other than the DLPFC, which other brain region is associated with spatial attention?

the posterior parietal cortex (lateral intraparietal area)

The posterior parietal cortex (PPC) shows strong connectivity to which areas?

areas of the brain that control eye movements:

• frontal eye fields

• superior colliculus

How do the frontal eye fields move eyes to the opposite direction?

via connections to the superior colliculus

True or False: Holding fixation on a single spot is not normal; the eyes naturally move to whatever “grabs” our attention.

true

What is important to know about area LIP (lateral intraparietal)?

• a salience map is built here

• neurons in the LIP show enhanced neural activity just prior to making an eye movement to a visual target

• electrical stimulation of area LIP evokes saccades (quick movements) of the eyes

Delirium is which type of attention disorder?

disorder of vigilance

What else is delirium called?

metabolic encephalopathy

True or False: Delirium is very common in hospitals. 20-25% of patients over 65 years old in general hospital wards will develop delirium.

true

What is hemispatial neglect seen after?

a right parietal lobe stroke

What is anosognosia?

lack of awareness of deficits

What is anosognosia associated with?

hemispatial neglect

Review the summary chart on the last slide again!

alrighty :)

Which brain structures are associated with the different types of attention?

• vigilance:

  • ARAS

  • thalamus

  • mesial frontal cortex

• selective attention:

  • DLPFC

• spatial attention:

  • posterior parietal cortex (PPC)

Which psychological tests are associated with the different types of attention?

• vigilance:

  • simple continuous performance tasks

  • preservations

• selective attention:

  • complex continuous performance tasks

  • Stroop test

• spatial attention:

  • clockface

  • line bisection

Which disorders are associated with the different types of attention?

• vigilance:

  • delirium

• selective attention:

  • ADHD

  • schizophrenia

  • Parkinson’s

• spatial attention:

  • hemispatial neglect