Week 9 Lecture 2

Question 1

What is attention?

Answer 1

The process by which the mind selects a sensory stimuli to process at any given moment.

Question 2

What are the most important things we pay attention to as humans?

Answer 2

Eyes, facial expressions and what people say (voices) - all important for human communication.

Question 3

What is the functional significance of attention?

Answer 3

Attention allows only some info to enter consciousness - maintains an incomplete picture of the world.
Hoffman (2019) - it would be disadvantageous for the mind to represent the world as it is - used an AI model to show that such systems would quickly die out. Instead successful organisms process only a subset of stimuli and create representations of these which are important for survival and reproduction.

Question 4

Types of attention

Answer 4

Reflexive attention - stimulus driven - bottom-up process where a sensory stimulus captures our attention e.g. orientating reflex.
Selective attention (task driven) - top-down choosing of what to attend to - depends on task, context and emotional state.

Overt - orientating with body
Covert - no motor movements e.g. looking/listening
Divided attention - ability to pay attention to several things at the same time. Is this even possible?

Question 5

2 major ideas of attention

Answer 5

James (1890) - everybody knows what attention is.
Hommel (2019) - nobody knows what attention is. It is a complex process involving lots of factors e.g. sensory stimulation representing objects, tasks, needs, comes together to determine what we pay attention to

Question 6

Studying visual selective attention

Answer 6

Participant fixates the eyes on the central crosshairs while stimuli are flashed to the left and right fields. The participants covertly attend to the left, ignoring the right stimuli. Swap sides.
The responses to the same physical stimuli are compared when they are attended and ignored.

Question 7

Listening attention research methods

Answer 7

Dichotic listening tasks
Participant receives two different messages. Told to attend to one ear.
Participants can give information about the attended ear but only the gender (surface information) of the other speaker - not what was said.

Active vs passive method
Active - pay attention to sounds, passive - ignore the sounds/read a text/watch video with no sound.
Contrast active to passive.
However, may be changing general arousal and other physiological processes as well - dichotic is better as only focus of attention is changed.

Question 8

Attention enhances brain response

Answer 8

Attending to a stimulus leads to higher activation of those neurons responding.
This can be seen at all levels - in cortex, subcortical stations, non-invasive recordings (EEG, MEG, fMRI).

Attention changes the system, the way nerve cells are connected - it may only be temporary but the receptive fields (space the neurons respond to) change in shape and size.

Question 9

ERPs are enhanced by attention

Answer 9

N1 response
Hillyard et al - amplitude of N1 component enhanced when attending compared to ignoring the stimulus.

Question 10

The cocktail party effect

Answer 10

Selective attention example - you require the ability to follow one conversation in the presence of many. Attention filters out the background noise. For a long while it was unknown how we do this.

Question 11

Intracortical readings from the cortex and the cocktail party effect.

Answer 11

Mesgarani & Chang (2012)
Presented sentences to epilepsy patients while taking intracortical readings (within the brain) from the auditory cortex.
They present individual words and short sentences without a task.
A mathematical filter tells us how the system is responding to different kinds of words.
Can then turn the process upside down to present the sentence of words using filters to see what the stimulus was.
Can then recreate a sentence spoken by 2 people at the same time.

Reconstructed spectrograms
Stimulus spectrogram reconstruction…
In the mixed condition (multiple sentences being presented), the cortex is responding as if the sentence being attended to is being presented alone.
In a noisy environment with multiple speakers the auditory cortex responds as if there was only one speaker.
Solution to the cocktail party problem - some kind of filtering happening allowing only the salient message to come through.

Question 12

Attention and the visual cortex

Answer 12

Hopfinger et al (2000) - fMRI study showed that attending to the left or right visual hemifield leads to increased activation in the visual cortex of the contralateral hemisphere.
There is no effect in the primary visual cortex (V1), events start in the secondary areas. V1 guides selective attention.

Question 13

Cortex, midbrain and attention.

Answer 13

Complex behaviour requires selective attention controlled by the frontoparietal network.
Salient stimuli that have a spatial location require a midbrain network that directs spatial attention and gaze to stimuli location.
The midbrain and cortex then work together to assess risk and benefits of the stimulus.

Question 14

Attention network in the cortex

Answer 14

Sensory signals enter via the thalamus –> sensory cortices e.g. visual/auditory (primary then secondary areas).
Prefrontal cortex - meaning and salience.
PFC generates a signal for where to focus attention which targets either the attentional control network (sensory cortices) or thalamus.
The orbitofrontal cortex then figures out what sort of emotional response is needed in response to the salient signal.
Info sent to the limbic system to generate emotion.

Question 15

Attentional modulation of the thalamus

Answer 15

The thalamus is the subcortical ‘entry gate’ to the cortex.
A thin layer of neurons called the thalamic reticular nucleus (TRN) surrounds it.
The PFC can switch on individual cells in the TRN, active TRN cells suppress signals in the thalamus.
Therefore the PFC controls what sensory inputs make it to the cortex.
At the same time it is telling the emotional part of your brain how you should be responding - gets fed back into the cortex - all interconnected.

Question 16

Control of visual attention
Selective attention

Answer 16

Hopfinger et al., 2000.
Participants knew a stimulus was going to be shown in the left and right hemifield - told to focus on the left. Pause of 8 seconds.
Dorsal frontoparietal network is active when attention directed to a specific location in expectation (no stimulus). Before the target is delivered attention also activates the visual cortex.

Question 17

Control of visual attention
Reflexive attention

Answer 17

Corbetta et al., 2000
Ventral right network directs attention to stimuli with high salience e.g. surprise.
Suppressed during selective attention tasks.
Depending on the situation/context/type of attention being paid, different areas of the cortex are active. There is not one single attention area.

Question 18

Control of auditory selective attention

Answer 18

Hill & Miller (2010).
The left hemispheric network control attention during the cocktail party effect. Includes the left inferior frontal gyrus and left superior parietal lobe.

Frontal and parietal areas control attention, precise areas depends on sense involved i.e. vision, hearing and whether attention is task or stimulus driven.

Question 19

Attention and the limbic system

Answer 19

In adults attention leads to plastic changes in the cortex:
1. Stimulus in attentional focus
2. PFC activates the nucleus basalis (NB)
3. NB releases acetylcholine
4. Acetylcholine targets cortical neurons representing the stimulus.
5. The connections of these neurons are strengthened via LTP (long term potentiation - strengthening of synapses based on recent activity).

Question 20

What information does the superior colliculus receive?

Answer 20

All the sensory information - a relatively unprocessed version.

Question 21

Superior colliculus in humans and birds comparison

Answer 21

In birds he SC is called the optic tectum and is much bigger than in humans - a much greater ratio in comparison to the cortex.

Question 22

Use of the SC historically

Answer 22

It is a highly developed neural processor that does sensory discrimination and rapid decisions for motor actions necessary for survival and reproduction.

Processes sensory information and turns it into motor action.

Question 23

Layered structure of the superior colliculus.

Answer 23

Upper layers - receive input from the retina and visual cortex, respond to visual stimuli.
Intermediate and lower layers - input from all senses and most of the brain - includes salience and task relevance information.
Lower layers - motoneurons that direct eye saccades and other orienting movements. SC integrates information from the senses and cortex and transforms this into orienting responses.
Gaze and body can orient from the superior colliculus integrating all this information across the brain.

Each layer is a topographic map of space. Activation of motoneurons in a particular location will initiate a saccade shifting gaze and attention onto that location. Triggers a motor response.
Only one location can be active at once.

When the SC, thalamus and PFC all agree on what we need to focus on, the cells oscillate at the same frequency across the brain - 40Hz.