2014.3|4 - Attention and Consciousness

** l4 lecture notes and reading

what is attention?

a selective state necessary for conscious processing of sensory information

what is the unselective state alternative to atention?

arousal

why is attention necessary?

we don’t have memory capacity to process all information with high fidelity, therefore some information is selectively processed in expense

what revolves around assumption of attentional affects on sensory processing?

where/how attentional networks in relation to early/late selection processing

T/F: only higher order representations are under attentional control

FALSE, early selection does occur during attention (at least at cortical processing levels)

T/F: there is no evidence to support that attentional effects affect higher order cortical processes more than early stage ones

FALSE, attentional modulation of neuronal activity is more profound in higher areas

what brain measure is often employed to measure attentional processing?

ERPs

what does ERP evidence tell us about attentional processing?

attentional modulation of electrical brain activity occurs very early after stimulus presentation

what is the task measuring attentional processing via ERPs?

dichotic listening task

what were the findings from ERP dichotic listening task?

larger N1 amplitude for attended stimuli, occurring ≈90ms post onset; P20-50 components occurring even earlier (therefore early level processing is affected)

what are the limitations of ERP data for attentional processing?

no spatial resolution to detect the source of the difference signal between N1 and P20-50 ERPs

where was the difference signal of attentional processing detected by MEG scans?

auditory cortex

what did evidence from auditory brainstem challenge from the dichotic listening task results?

responses in brainstem were not affected by attention, therefore earliest selection occurs at a cortical level, however → OTOACOUSTIC EMISSION

how does triggered otoacoustic emission (sound within inner ear) dispute earliest selection at cortical levels?

otoacoustic emissions are still affected by attention, implying lower level of modulation

why is covert rather than overt attention often used to measure neural signatures associated with attending?

technical controls of experimental parameters

what are the differences between overt and covert attention?

overt: directing most sensitive parts of sense organs to attend voluntarily, covert: direct our mind to attend involuntarily

what is overt attention?

voluntary - endogenous, top-down, sustained

what is covert attention?

involuntary - exogenous, bottom-up, transient

what is top-down attention?

we have control over whether to attend a certain object, feature or location

what is bottom-up attention?

we have no control over what we attend; improves stimulus detection in short period of time ≈200/250ms however at an expense

what is the expense of bottom-up efficient detection of attended location?

inhibition of return, detrimental effect lasting ≈600ms

what had the ERP signatures found for top-down (covert) attention?

larger P1 in occipital scalp when contralateral field is attended; but only location affects change, no difference during feature or object based attention tasks

T/F: effect of attention occurs later in visual cortex than auditory cortex

TRUE, ≈70-100ms visual; ≈20-30ms auditory

what describes the different attention processing times between vision and auditory senses?

timings reflect differences in latencies between sensory systems

what had the ERP signatures found for bottom-up (reflexive) attention?

P1 was found larger in the hemisphere representing the attended location, however P1 was smaller if stimulus was delayed; neurophysiological correlate of inhibition of return

what is the time taken to find an item in visual search tasks dependant on?

how much an item pops-out; possession of distinctive features which can be processed pre-attentively

what is the visual search time dependant on in absence of pop-out search?

the number of items present in the display (more or less linearly); conjunction search, the presence of multiple features in items

What is Conjunction Search?

In a conjunction search, we’re looking for an item that combines multiple features, like a red circle in a set of red squares and green circles. This search is more complex because we need to identify items based on a combination of features rather than just one.

How Does Feature-Selective Attention Help?

Feature-selective attention allows us to focus on specific features, like color (e.g., red) or shape (e.g., circular). This helps guide our attention to areas where relevant items (items with the target features) might be located, ignoring others, like green or square items.

Why Does Conjunction Search Take Longer with More Distractors?

In conjunction search, when there are more distractors, it takes longer because we must move our "spotlight" of attention across more locations. Each shift takes time, which increases the search duration.

How Does Search Time Depend on Distractor Features?

Search time increases more when there are distractors that share one of the relevant features (e.g., other red items or other circles). It’s less affected by distractors that don’t share any relevant features. This suggests that feature similarity influences where we focus our attention.

Can We Measure Feature-Selective Attention in the Brain?

Yes, experiments show that we can find brain signals, or electrophysiological correlates, related to visual search and feature-guided spatial attention. For example, a brainwave component called "P1" is stronger when attention is on areas with relevant features.

What Happens During a Visual Probe Experiment?

after a brief display of the search items, a probe (a brief visual marker) appears where a previous item with a relevant feature was located. The P1 brain response is stronger when the probe is in an area that previously had a relevant item, showing our attention was drawn there.

How Does Feature-Selective Attention Work Over Time?

Feature-selective attention seems to "label" all relevant locations quickly. After about 30 milliseconds, spatial attention moves to these labelled areas. So, there’s a sequence: first, the brain marks relevant items based on features, then it directs focus.

What Are the Brain Regions Involved in feature-selective attention?

it’s first processed in the occipital cortex (posterior region of the brain) and then quickly activates the N2pc component in more anterior regions. The N2pc indicates the brain is now focusing spatially on relevant items for the task.

What is proactive interference?

When previously learned information interferes with learning of new information

What is retroactive interference?

When newly learned information interferes with recall of old information