Attention (3)

What is attention?

The ability to focus on one aspect of sensory input (ex. visual or auditory input)

Allows us to preferentially process some information and ignore the rest

What is an example of attention during an attention-demanding visual task?

Reading a book at a coffee shop, we are less sensitive to the sounds of people talking around us

Attention has significant effects on:

Perception

Corresponding changes in the sensitivity (increases) of neurons at many brain locations

What is consciousness?

Awareness of something

What occurs in our brain when we engage in a perceptual or behavioral task (in terms of activation)?

We have decreases in activity of some brain areas, whereas task-relevant areas become more active

Ex: if person is required to perform a difficult visual task and ignore irrelevant sounds, we would expect the visual cortex to be more active and auditory cortex to be less active

Why is resting brain activity fundamental and significant?

Areas showing decreased activity during behavioral tasks are always active at rest and become less active during any task

Patterns of brain activity changes from resting to tasks are _______ across human subjects

consistent

What brain areas are active in a resting state? (5)

- Medial prefrontal cortex

- Posterior cingulate cortex

- Posterior parietal cortex

- Hippocampus

- Lateral temporal cortex

The brain areas active in a resting state together form the ___________.

Default mode network

What is the default mode network?

Areas of the brain that are active in a resting state

Brain defaults to activity in this group of areas when it is not engaged in an overt task

PET imaging studies of the brain during nine different tasks involving vision, language and memory showed:

Certain brain areas decreased activity when switching from resting state to the task

Helps us realize which brain areas are most active in resting state

What are the two hypotheses for the function of the default mode network?

- The sentinel hypothesis

- The internal mentation hypothesis

What is the sentinel hypothesis for the function of the default mode network?

Even when we're at rest, we are broadly monitoring the environment --> "always on the lookout"

What is the internal mentation hypothesis for the function of the default mode network?

Default mode network supports thinking and remembering, like daydreaming

What is evidence to support the internal mentation hypothesis for the function of the default mode network?

Autobiographical memory tasks (ex: recalling a past event or envisioning a future event) --> increases DMN activity

Simple use of facts in control tasks do not activate the brain in a similar manner

fMRI imaging of the brain during autobiographical memory tasks showed:

Activation of the posterior cingulate and medial prefrontal components of the default network

(more activation than in control tasks)

What happens when the situation requires us to become actively involved in a perceptual or motor task?

we switch modes from sentinel and internal mentation activities to focused processing of sensory input

aka from high default network activity to low default network activity (and increased sensory-motor activity)

What is selective attention?

Directed attention, filters out input

What does limited capacity of attention lead to?

Attention-deficit hyperactivity disorder (ADHD)

What is exogenous attention?

Bottom-up attention

Stimulus attracts our attention without any cognitive input (ex: animal detecting predator by its distinct color to evade them)

What is endogenous attention?

Top-down attention

Attention is deliberately directed by the brain to serve a behavioral goal (ex: looking for a friend in a crowd)

What does attention enhance?

Visual sensitivity

Describe the experiment that determined the effect of cueing on target detection and attention.

1. Observer fixed on a central point. They were tasked with saying if a target stimulus was flashed to the right/left or not at all.

2. Each trial begins with presentation of a cue stimulus (plus sign or left/right arrow). The cue serves to direct the observer's attention

3. If the observer was flashed a plus sign, the target stimulus was equally likely to be on the right or left side.

4. If the observer was flashed with a left arrow, the target stimulus was more likely to be on the left --> observer diverted their attention to the left more, faster reaction time

5. If the observer was flashed with a right arrow, the target stimulus was more likely to be on the right --> observer diverted their attention to the right more, faster reaction time

How do invalid, neutral, and valid cues affect target detection?

- invalid (cue misdirects you): decreased accuracy of target detection

- neutral (plus sign, gives no info): baseline accuracy

- valid (cue correctly directs you): more accurate target detection

How do invalid, neutral, and valid cues affect reaction times?

- invalid (cue misdirects you): longer reaction times

- neutral (plus sign, gives no info): baseline reaction time

- valid (cue correctly directs you): faster reaction times

What are the effects of attention on neural activity?

Attention increases firing rate, sensitivity, and specificity of neurons

The effects of attention are observed in which brain areas?

high-level cognitive and numerous sensory areas

What is the "spotlight of attention"?

- Attention “illuminates” stimuli of particular interest/significance and processes them, while leaving other parts less processed (similar to how a spotlight highlights part of a stage) 

- Evidence: functional MRI imaging of human attention to the location

Numerous brain areas appear to be affected by attention and the particular areas affected depend on _______________.

the nature of the behavioral task performed

aka different aspects of a stimulus activate different brain areas

In the selective attention experiment, the parietal cortex was influenced by:

Attention to the motion task

Selective attention was associated with enhanced activity in different brain areas when attention was directed to which different attributes of a stimulus?

speed (green), color (blue), or shape (orange)

Does attention change based on eye movement?

Attention changes location prior to eye movement

Eye movement will enhance brain activity in the posterior parietal cortex --> may speed visual processing and reaction times

Neuron activity is enhanced if the attention is followed by a _________.

saccade

When is the response of a neuron in the posterior parietal cortex enhanced?

when attention shifts to the target (like by a saccade) in order to accurately perform the task

Describe the experiment that determined the significance of the posterior parietal cortex on attention in monkeys.

1. Monkeys fixated on a spot on a computer display

2. Stimulus was flashed on peripheral retina at a location of the receptive field under study

3. Monkey was cued to either hold fixation on the initial spot or saccade to the flashed stimulus (bring it to attention)

4. In either case, the parietal neuron was excited by the stimulus flashing in its receptive field

5. The parietal neuron's excitation was significantly enhanced when the animal made a saccade to foveate compared to when they maintained fixation at the initial location

How is the enhancement effect spatially selective?

it is not seen if a saccade is made to a stimulus not in the receptive field

When is enhancement also seen in the experiment with the monkey?

when the task requires the animal to release a hand lever when the peripheral spot dims (performs a manual task)

What are cortical and subcortical areas of the brain responsible for?

guiding attention + saccadic eye movements

What is the pulvinar nucleus and what does it do?

- Projects and sends widespread efferents to many areas of cortex

- Regulates visual information flow

Which areas of the cortex does the pulvinar nucleus project to?

- visual cortical area (V1 and V2)

- parietal cortex

- medial temporal cortex

- inferior temporal (IT) cortex

Where is the pulvinar nucleus located?

Posterior thalamus

How are humans with pulvinar lesions affected?

Respond abnormally slowly to stimuli on the contralateral side, particularly when there are competing stimuli on the ipsilateral side

This deficit reflects a reduced ability to focus attention on objects in the contralateral visual field

Injection of Muscimol in the unilateral pulvinar nucleus would produce:

Difficulty in shifting attention to contralateral stimuli

Muscimol = GABA agonist

Injection of Bicuculline in the unilateral pulvinar nucleus would produce:

Facilitation of shifting attention to the contralateral side

Bicuculline = GABA antagonist

What are salience maps?

Shows locations of conspicuous features (very noticeable)

Hypothesis to explain how certain visual features grab our attention

The visual cortex is organized on the basis of which features?

a variety of stimulus attributes/features, such as orientation, color, and motion

Salience maps are an example of bottom-up or top-down attention?

Bottom-up

What is a priority map?

- Shows locations where attention should be directed

- Based on stimulus salience (ex: red hat sticks out in a crowd) and cognitive input (ex: I am looking for a friend wearing a red hat)

Priority map = salience map + top-down effects

Generally paying attention to an image and then drawing it after is an example of bottom-up attention or top-down attention?

bottom-up attention

Focusing specifically on the left side of the picture is an example of bottom-up attention or top-down attention?

top-down attention

What area of the brain appears to construct a priority map based on bottom-up and top-down inputs?

Lateral intraparietal cortex (area LIP)

Plays a role in guiding eye movements and attention

Where is the lateral intraparietal cortex (area LIP) located?

Buried in the intraparietal sulcus of the macaque brain

Lesions in the parietal cortex are associated with __________.

Neglect syndrome

What is hemispatial neglect syndrome?

Inability to attend to half of the environment (disruption in ability to shift attention)

Person will ignore objects, people, and their own body to one side of the center of gaze

What is hemispatial neglect syndrome associated with and what happens?

Right-sided lesions of the posterior parietal cortex

Person can see stuff, but ignores the stuff on the left side (bc they can't shift their attention to the left side)

What is the hypothesis of which sides of the cortex attend to which sides of the visual field?

Left hemisphere attends to right hemifield

Right hemisphere attends to BOTH right and left hemifields

What are the 6 regions of the macaque brain?

- Prefrontal cortex

- Frontal eye fields (FEF)

- LIP

- Pulvinar nucleus

- Superior colliculus

- Visual Cortex

What is the pathway of bottom-up attention in the frontoparietal attention network?

visual input → occipital lobe → lateral intraparietal cortex (LIP) → construction of salience map

What are the effects of bottom-up attention in the frontoparietal attention network?

visual processing is enhanced, eyes may move (automatically)

What is the pathway of top-down attention in the frontoparietal attention network?

frontal lobe (prefrontal cortex + FEF) → LIP and FEF → creates priority map

In top-down attention, modulation of _________ enhances perception of selected objects.

visual cortical areas

What are the effects of top-down attention in the frontoparietal attention network?

(intentional) saccadic eye movements

What is the materialist perspective of consciousness?

Consciousness arises from physical processes in the brain

Based on the structure and function of the nervous system

What is the dualism perspective of consciousness?

Mind and body are different things --> one cannot be fully explained by the other

Consciousness cannot be fully explained by physical processes/neural activity

What are the easy problems of consciousness?

Phenomena that are answerable by scientific methodology

Ex: Sleep-awake difference (we can see this through EEGs and other methodology)

What are the hard problems of consciousness?

The experience itself + why the experience is the way it is

What are the neural correlates of consciousness?

The minimal neuronal events sufficient for a specific conscious percept

What are bistable visual images and how can they tell us about neural correlates of consciousness?

Images presented to the eyes that can be seen in two different ways

We can learn about NCC by seeing how brain activity changes when we switch from one perception of the image to another

What happens in binocular rivalry?

Visual effect where different images are seen by the two eyes --> perceptual awareness alternates between the two images

Neural recordings in monkey __________ show changes correlated with perceptions.

inferotemporal cortex (IT area)

What was the experiment regarding monkeys and binocular rivalry?

1) Monkeys were trained to pull a left lever if it saw a starburst pattern, and a right lever if it saw a monkey face

2) Was then shown a starburst to the left eye and monkey face to the right eye

3) Monkey alternated between pulling R and L lever --> shows they were alternately perceiving the starburst or monkey face (instead of seeing both at the same time)

What is the neural correlate of awareness during binocular rivalry?

neural activity in the IT (fluctuated btwn low and high activity when the monkey switched perceptions!)

Can attention be confounded with awareness?

Yes, but attention can also be independent of awareness