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What is attention?
We have limited capacity to process competing options and our attention selects, modulates an sustains focus on information most relevant for behaviour.
why is attention important?
we need to prioritize information so we dont waste time and energy on irrelevant efforts
exogenous source
in the environment, reflexive, automatic,
"bottom-up"
eg. a clap, sharp pain, or bright flash.
endogenous source of attention
in the mind, voluntary, intentional, "top- down"
eg a goal desire or instruction.
external target of attention
sensory information, in the environment
- a sensory modality, spatial location, feature, or object.
internal target of attention
metal representations, in the mind
- a memory imagery or plan
What are the types of attention
● Overt vs. covert
● Transient vs. sustained
● Selective vs. divided
What is the source of attention?
the cause for directing ones attention
Overt attention
Involves actual movement of the sensory surface,
e.g.: moving the eyes, directing the ear
Covert attention
does not involve actual movement
-- looking at the corner of ur eye
Transient attention
momentary focus on something
Sustained attention
prolonged focus on something
selective attention
focus on one thing to the exclusion of others
divided attention
focusing on multiple things simultaneously
At the zoo, after reading a sign that says "Squirrel monkeys like to rest on tree limbs," you look up at the top of a tree in the monkey house for several minutes.
What is the (i) source and (ii) target of your attention?
The source of the attention is endogenous, and the target of your attention is external.
because of the sign you read you chose to direct your attention to the tree tops because you wanted to see a monkey.
At the zoo, after reading a sign that says "Squirrel monkeys like to rest on tree limbs," you look up at the top of a tree in the monkey house for several minutes.
What types of attention are you exhibiting?
Overt and sustained - you are moving your eyes looking for a monkey and keeping your attention on the trees.
hierarchy of attention
What is dichotic listening
A subject wearing headphones is presented different sounds to each year. They are given instructions to attend to one ear but not the other.
What is the source of attention in dichotic listening?
endogenous - they are attending to the left ear
What is the target for dichotic listening
sounds entering the left ear
What types of attention are occurring during dichotic listening ?
covert - still have both sounds entering both ears
sustained - continue to attend to one ear
selective
What was found in the 1953 study of dichotic listening by cherry?
subjects could report existent of message in unattended ear
could report the gender of the speaker
could not report the content
Based on the study byCherry 1953 what does this tell us about where attention occurs?
suggests a early all-or-none filtering model of attention also known as the Broadbent's filter model.
Explain this early all-or-none filtering model of attention or broadbent bilter model
the filtering of attention happens early, before the brain processes meaning. It is all or none because only the attended message is making it thought to higher level processing.
What was found in the 1959 study by Moray on dichotic listening ?
the subject could
report change in the gender of the speaker
could report change in pitch of tone
could not report a word repeated many times
could not report hearing their own name.
of the unattended message
What do these results mean?
they are inconsistent with the all or none filtering theory. So this suggests there is a different explanation about where attention occurs.
What was done in the 1960 study by Gray and Webbeburn on dichotic listening ?
the subject was told to attend to the left ear, but in the middle they would switch the message to the right ear and then back.
What was found in the 1960 study by Gray and Webbeburn on dichotic listening ?
- the subjects were able to put the message together even though they werent fully attending.
What does this suggest about when attentional selection occurs?
suggests that attentional filtering may still occur early on in processing but it isnt an all or none process like the eariler model suggested. The filter is leaky.
What is the name of the model that suggests early attentional selection but with a leaky filter?
Early attenuation (treisman's attenuation theory)
Describe the experiment performed by McKay in 1973 on dichotic listening?
attended ear is given ambiguous sentences
"they were throwing stones at the bank"
unattended ear participants heard related words. "river" or "money"
subjects were then tested, and had to chose a sentence that was closest to the meaning of the message.
What were the reslts of the 1973 study by Mckay?
The meaning of the word in the unattended ear affected the participants choice in the test phase.
participants were unaware of the presentation of the biasing words.
What does the Mckay study suggest about the location of attentional selection?
attentional selection occurs later on closer to the motor response.
this is known as the late selection model proposed by mkay.
Which model for attentional selection is correct?
- it is more of a mix. "strategic control of attention"
● Early versus late selection can be chosen based on situation and approach
● Attention is applied by top- down modulation
EEG
Electroencephalography
Event Related Potentials (ERPs)
● Non-invasive technique
● Measures surface electric fields generated by post- synaptic potentials in dendrites of neurons
temporal resolution of ERP's
High temporal resolution: signal sampled >1000/sec
spatial resolution of ERP's
Low spatial resolution: up to 256 electrodes
ERP's are critically dependent on
how the neurons are organized
-this makes it difficult to know where the signal is coming from
How are the event related potentials created?
When a stimulus is percieved the subject pushes a button, signals from the EEG are averaged for only the points where the stimulus is present.
Event-related potentials ERPs are plotted
with the negative up
Event-related potentials ERPs are
time locked to an event of interest and are an average of EEG signals
Event-related potentials ERPs can be used to form a
surface distribution of ERP wave form through time
ERP's to auditory tone stimuli within the brain stem
Midlatency Reponse (primary auditory cortex ERP's to auditory tone stimuli
Late waves (secondary/tertiary auditory cotex) ERPS to auditory tone stimuli
What is the neural hierarchy of attention
ears
brainstem/thalamus
primary auditory complex
secondary/tertiary cortex
multimodal association cortex
Attentional stream paradigm
a random sequence of pips given to subject through headphones and an occasional deviant occurs or different pitch of volume. The subject is told to only attend to one ear.
What was the effect of attention on auditory ERP's in the brain stem with the attentional stream paradigm?
there was no affect.
What was the effect of attention on auditory ERP's on midlatency potentials with the attentional stream paradigm?
difference in the attended and unattended signals was observed - showing there was an effect
What was the effect of attention on auditory ERP's with the late waves with the attentional stream paradigm?
there is a large difference between the attended and unattended
large attentional effects - the attended sounds are causing a larger response in the brain.
What about the oddballs?
person will say they did not remember the odd balls but the ERP's show that there is still a significant difference between the deviant and standard signals in the unattended ear.
Are there affects of neural attention in the brain stem?
no - attentional affects were shown through ERP's to begin in the primary auditory complex and the secondary and tertiary auditory complex
Describe the Posner Orientating task
you maintain focus on a central fixation, and cues occur telling you to pay attention to either side (sometimes valid and invalid)
and soemtimes no cue.
In the posner task how many cues are valid
80%
In the posner task how many cues are invalid?
20%
What is the source of attention in the posner task?
endogenous
explain why the posner task involves a endogenous source of attention
the arrow occurs centrally and you to respond symbolically. Your brain tells you to attend to one side because of knowledge you have taken in .
What is the target type in the posner task?
external
you are looking to something in the outside world not your own mind
Does the posner task use overt or covert attention?
covert
eye movements arent associated with this task because you are focused on a central fixation.
does the posner task involve transient or sustained attention?
transient
Does the posner task involve selective or divided attention?
selective
What are the results of the posners task with endogenous cueing?
the cue to target interval is >300 ms
-there is a benefit from a valid cue
-there is a cost from an invalid cue .
How would a posner task with an exogenous source function?
the task is changed slightly from the original to affect a different type of attention.
there is a flash that occurs at either the right or left side capturing your attention. Cue is no longer in the middle.
Still the cue is either valid or invalid.
What are the results of the posner task with exogenous source.
at short cue to target intervals:
● Valid cue facilitation
At long cue-to-target intervals (>= 300 ms)
● Valid cue Inhibition of return
Why does this inhibition of return occur? (flip over)
when something exogenously capture attention - you cant help but have it pull your attention over, but if you wait there for alittle bit, then your brain shifts back to what you were looking at initially (the center) your brain says there isnt anything there so lets not pay attention to that it tricked me , your brain inhibits the attention in that place after a certain time period.
the effects of endogenous and exogenous attention are
different.
describe the posner orienting task with objects
● Participants saw two side-by-side rectangles
● A cue was then presented
● Followed by a target
● Participants indicated when they saw the target
In this experiment the cue could be:
● Valid
● Invalid, but on same object
● Invalid, but on other object
What are the results of the posner task with objects?
The mean response times as a function of target location were recorded.
the cost having an invalid cue on the wrong object is higher than having an cue on the wrong location on the same object.
In a ERP what do the P1 and N1 stand for
the first neural responses that are observed after a visual stimulus.
What is the visual attentional stream paradigm
similar to spatial cueing (like the posner task) but with sustained attention, to one side more than the other.
What are the results of this when looking at the ERP's
there are larger peaks for the attended location compared to the unattended location.
Attention affects
reentrant activity
What does this mean?
attention affects the initial activity in the cortex, but also affects the brain activity during the initial processing but also through the reentering processing
The location of visual attentional effect: V1, V2, V3, V4, can be seen in the brain during MRI, what is shown with this?
increased activation due to attention occurs in all the visual areas. This means that attention has wide spread affects throughout the visual pathway and increases the firing of neurons
In the functional MRI study of spatial attention effects in the lateral geniculate nucleus, what type of study was performed?
a flash pattern was shown on a screen and subject was asked to either attend to the right or the left. The activity in the brain was monitored using MRI.
What were the results of the study on spatial attention effects in the LGN?
there was increased activation in the area representing the attended and decreased activation in the unattended.
In the MRI there was also activation shown in the thalamus. Why?
effects of attention start early in time but they are also pervasive though out the brain,
Describe the experiment by Moran and Desimone (1985) on the visual attention of V4 neurons
animal is presented with a central fixation to the left of the receptive field of V4. THere are two stimulus bars within the receptive field. One is preferred (red bar) and unpreferred (green bar).
animal attending to effective stimulus there is stronger firing of the neuron, than attending to the ineffective. however the neuron fires in both cases.
The orientation tuning curve
attention causes GAIN (mulitlicative scaling), but no change in feature selectivity.
-- neuron firs more in response to attended stimulus, but fired about the same when the stimulus isnt there. The difference between the non-preferred and preferred is greater when there is attention than to when that stimulus is unattended.
Attention enhances
signal-to-noise contrast
if the signal is low contrast, what is the result
small response
small change
ie if the stimulus is so small that it is hardly there (ie too dim) then the neuron wont respond if it is attending or not.
if the signal is medium contrast then the result is
medium response
big change ( or difference between attended and unattended)
if the signal is high contrast (ie really bright), what are the results?
there is a big response
small change
if stimulus is really bright then less attention is needed so the difference between attended and unattended isnt as big as medium contrast.
What is an example of higher level visual attention
A study was done by Gazzaley et al. in 2005 on visual attention to objects, In the fusiform face area the activity was greatest when the subjects were attending to faces. They were also attending to scenes. And were told to attend to one or the other and ignore the other.
What does this tell us about attention?
Attention occurs in low level visual areas all the way up to high visual processing like the fusiform facial area.
Where is this area located?
dorsal (back) of head right hemishpere as in diagram.
What does attention effect?
reaction time
accuracy
awareness of sensory stimuli
attention can have effects less than _______________ after stimulus onset
less than 100 ms after stimulus onset
- attention has fast affects on processing
Attention modulates what?
neural activity
Where does attention modulate neural activity?
in brain areas for locations and objects
Attention enhances what
neural response to attended stimuli
(eg enhanced signal to noise ratio in contrast study)
Attention increases neural ____________________________ between brain areas.
synchronization.
What does attention synchronization between brain areas mean?
attending to a stimulus is associated with increased synchronization between all areas of the brain that are processing the stimulus together.
Describe the experiment by Bosman(2005) on synchronization.
Areas V1a (A) and V1b (B) and V4(C) studied. Subjects given 2 stimulus 1 and 2.
Stimulus 1 - activates area A and C
Stimulus 2 -activates area B and C.
the LPF's for each site were recorded in waves.
Why did the V4 (C) respond to both stimuli
has a larger receptive field
What was found in sites A and C when there was no attention to stimulus 1 (A and C are activated by stimulus 1)?
brain areas A and C were firing - the same amount as when there is attention to stimulus 1. But the waves are not synchronized.
What was found when animal is attending to stimulus 1?
LFP's for sites A and C are synchronized.
unilateral (hemispatial) neglect
A deficit in perceiving & responding to stimulation contralateral to damaged hemisphere
