Cognitive Neuroscience Lecture 15: Attention 1

L15: Attention 1

What is Attention?

William James:

-         Selection: Choosing 1 possibility out of many

-         Withdrawal: ignoring the rest

Many definitions

-         Filtering, Selecting, Binding, Focusing, Enhancing

Basic characteristics

-         '''Limited capacity'''

o Can only attend to a subset of visual input (some of space, a few objs)

o Multiple object tracking: we go bad after approx. 4-5 objs

o This requires selection: what/how to select, what results?

-         Selection

o Consequences of attentional selection

§ '''Inattentional blindness:''' Moonwalking bear

§ '''Selective reading:''' if you’re told to read only a certain type of text, you will unless something pops out at you like your name, special words like sex, physically different stim like caps/numbers, or stuff relating to the topic to main focus of attention (bold green example)

-         Modulation

o Once selected, attention can enhance visual perception and neural responses

o Attention alters the contrast sensitivity

§ If given a cue on a particular side, you notice more contrast on that side

-         Vigilance

o ability to sustain attention over time

o person seeks to detect appearance of a particular target stim of interest

o Long lasting tasks: e.g. airport scanner, where’s waldo

Our definition of attention:

-         Process by which one or a few among many competing representations are selected for prioritized representation

-         '''Mechanism '''that controls perception and information being perceived

-         Alters neural activity, giving stronger responses to attended info and weaker to unattended info

-         Occurs across many cortical regions (even subcortical), across all domains (sensory/motor/higher cognition)

When does attentional selection (aka filtering) happen?

-         In both early and late selection:

o Stimulusà

o Sensory registrationà

o Semantic processingà

o Response

-         '''Early selection: selection before semantic processing'''

o we have a limited capacity to process information and we only select a small subset of this information for extensive processing

o '''Bottleneck is BEFORE SEMANTIC PROCESSING'''

o You only process SOME inputs

o Evidence:

§ Dichotic listening task; only reported stream attended to

·       What breaks through? '''Sensory information. '''

o Switch to pure tone

o Switch gender

·       What doesn’t break through? Semantic information.

o Switch languages

o Played backwards

§ Differences in EEG brain waves based on attention as early as 100ms

o Problems with Early selection:

§ '''“Cocktail Party Effect”''': even if you’re not attending to a convo, you’ll hear if they say your name (and understanding your name is semantic info)

§ Some info can break through: your name and “fire”

§ '''Stroop Effect''': can’t filter out meaning of words

-         '''Late selection: selection after semantic processing'''

o both attended and ignored inputs are processed equivalently by the perceptual system, reaching stages of semantic encoding and analysis

o '''Bottleneck is AFTER SEMANTIC PROCESSING '''

o AFTER you process it, you only respond to some

-         Basically, there’s evidence for both.

-         '''The determining factor may be “attentional load”: how demanding is the task'''

o Low-load/easy: late selection

§ None of them is hard, so you have more resources to spread and don’t need to filter any out

o High-load/requiring lots of resources: early selection

§ You have less to focus on then

Irony of Load and Selection

-         Sometimes, under low-load you can be more distracted since information can ‘break through’

-         Easy task: bad performance, “easily distracted”

-         Hard task: good performance, “difficult to distract”

William James on Attention: “depends on…what the things are.”

What are the units of attention? What do we select?

-         Space

o '''Spatial orienting: Posner cuing task'''

§ Valid: cue pointed in direction of target

§ Invalid: cue pointed away from target

§ Neutral: cue pointed in both directions

o '''Covert attention''': attention without eye movements

o '''Overt attention''': attention through eye movements

o Results of Posner cuing task: RT is shorter when you shift your attention first

o 2 ways to selectively orient attention:

§ '''Endogenous attention '''(goal directed)

·       Voluntary

·       Top-down

§ '''Exogenous attention''' (stimulus driven)

·       Reflexive

·       Bottom-up

o Posner cuing ARROW is based on endogenous (look for the thing the arrow is pointing to…goal directed)

o Posner cuing BOLDING is based on exogenous (no one tells you to focus on the bolded square, but you do it)

o Deficit in attending to space: spatial neglect

§ Following damage to dorsal pathway (parietal, usually right)

§ Loss of attention or awareness to contralesional side (usually left side)

§ Neglect on the left visual space

§ '''Inferior parietal lobule & TPJ are important for space-centered, exogenous attention '''

§

o '''Neural Mechanisms: Parietal neurons and attention'''

§ Monkey fixating passively

§ Monkey not attendingànot much firing in parietal neurons

·       Monkey makes an eye movement, big response from parietal neurons (even before eye-movement occurs)

·       Overt attention: he’s moving his eyes

§ Covert attention

·       Monkey makes a hand movementà big response even though eyes never move

·       Covert attention: no saccades, just reaching

o What are these parietal activations doing?

§ Modulating activity in other visual areas: TPJ affecting other regions

§ '''Attention alters the contrast sensitivity'''

o '''Attention modulates the activity of V4 neurons'''

§ What will happen to V4 neuron response when both stimuli are presented within the receptive field of the cell?

§ Depends on which object the monkey is attending to

§ Monkey ignoring display, just paying attention to fixation

·       Cell responds strongly to blue-vertical alone but not white alone

·       '''Response of neuron “biased” towards attended stimulus (increased when effective stimulus, decreased when ineffective stimulus)'''

·       V4 responds more to effective 

o '''Cue period: endogenous attention '''

o '''Target period: exogenous attention'''

o Attention & Parietal lobe,

§ Parietal dissociation: different parts for exogenous vs endogenous

·       '''Intraparietal sulcus/superior parietal lobule: '''endogenous, cue-related orienting, goal-directed

·       '''Temporoparietal junction/inferior parietal lobule''': exogenous, target detection, stimulus-driven

o '''Dual Network Theory '''

§ Dorsal attention network helps orient attention in a goal-directed manner

§ Ventral attention network detects salient stimuli and triggers reorienting to them

o '''Dorsal attention network: domain general shifting '''(shows that any goal-oriented uses dorsal): GOAL DIRECTED; DORSAL

§ Shift task between magnitude and parity

§ Shift location between left and right

§ Same IPS/SPL regions mediate shifting spatial attention and task sets