Attention II: Control of Attention

Question 1

What is top down attention?

Answer 1

endogenous attention

Question 2

What is bottom up attention?

Answer 2

exogenous attention

Question 3

Do we understand the cognitive aspects of attentional deficit disorders?

Answer 3

no only the behavioral moreso

Question 4

Do exogenous and endogenous cuing to spatial location have different temporal dynamics?

Answer 4

yes in exogenous cuing the stimulus occurs unexpectadly or the cue occurs in a location which is where the target stimulus may or may not appear briefly attracts attention to that location and over 300ms that returns - fast and transient endogenous attention is sustained over a period of seconds minutes or hours

Question 5

In what regions of the brain does endogenous or top down focus of attention involve?

Answer 5

sustained activity in the fronto-parietal network including
-the frontal eye fields FEF
-regions dorsal to the intraparietal sulcus IPS

Question 6

Endogenous attention is what stream?

Answer 6

the dorsal stream

Question 7

Exogenous attention is what stream?

Answer 7

the ventral stream

Question 8

What was the endogenous cuing task in the Woldorff et al study?

Answer 8

-a letter cue indicates L R or P to indicate a possible target in the left or right lower visual field
-on p trials participants knew that no target would be presented this is the interpret cue condition in which mo shift of attention is required and this is the control,

Question 9

What was the purpose of the variable interstimulus time area between 900 or 1900?

Answer 9

cause of the stimulus is shown at the same interval can catch on and want to move attention in preparation for stimulus occurring so will discuss the eeg data where there is a data and shift attention in preparation for that earlier and maintain attention for an earlier trial

Question 10

What areas of the brain did woldorff and colleagues identjfy that are specifically engaged by cues requiring an endogenous shift of attention?

Answer 10

medial frontal and parietal areas
-eeg data is consistent with the frontal regions preceding the parietal regions
-there are bilateral activations in these regions but the medial portions are the ones with the shifts in attention

Question 11

What can we think of the frontal regions as doing in regards to the parietal regions when it comes to shifts in endogenous attention?

Answer 11

the frontal regions are somehow instructing the parietal regions to shift attention

Question 12

What did the eeg activity correlated to in the temporal dynamics of endogenous attention in the woldorff and colleagues study?

Answer 12

slow and sustained activity in the medial frontal and parietal regions are consistent with the temporal dynamics of endogenous attention

Question 13

In the woldorff and colleagues study when does general cue processing take place and when does attention processing take place? How was this determined?

Answer 13

general cue processing - 0-300ms
attention processin 400-1800ms
-this was determined via the inter[rect cue condition which does not havhe attentional shifts

Question 14

What did source analysis of the woldorff and colleagues study show?

Answer 14

-that there are two plausible sources - - two medial blobs and the gyrus they are and their orientation and location and same with the two parietal blobs and can make a forward models and say with these dipoles what is pattern of activity on scalp and what areas causes the shift in attention - medial frontal activity increases at 400ms and this is earlier than parietal activity which does not get going till just before the stimulus can occur - people engaging their attentiocresponseem based on previous trial timing is mitigated against due to the inter stimulus time variation and maintain represnetaiokn need to shift attention and 800ms in that propagts back to parietal cortex and will see how this encodes for both perceptual and for action and this is coming online through the parietal system - frontal lobe gets the parietal going to respond to a stimulus in space - the reponse to teh stimulus is not include din this graph just he attentional shift -

Question 15

What could the parietal lobe be in contact with in regards to endogenous attentional shifts?

Answer 15

the visual cortex to increase response

Question 16

What did the colby and goldberg study in endogenous attention in monkeys show?

Answer 16

-neurons in the lateral intraparietal LIP sulcus responds weakly to stimuli appearing in their receptive fields (fixation)
-the response is enhanced when there is an endogenous cue to attend to the relevant receptive field when the monkey must make a hand movement in the cued direction
-when a saccade must be planned based on a a peripeheral cue of activity in this area is enhanced
-when the signal to intiate a scaccade is given (the fixation point disappears) a new wave of activity is observed suggesting a role in motor planning (parietal cortex plays a role in preparing to receive something or to respond to a motor response)

Question 17

What is the LIP representing in the colby and goldberg study in endogenous attention in monkeys?

Answer 17

both stimulus and response related attention to the target location
-stimulus because there is a retinotopic map in the LIP which gets them to respond weakly and attention because it shows actviity when there is a saccade to the taregt location (the parietal cortex is involved in getting this attentional information to use for motor planning)

Question 18

How did experiments by Moore et al test the casual role for the fef in endogenous attention?

Answer 18

1. identifying fef neurons that when strongly stimulated evoke a saccade to a specific location in the visual field
2. v4 neurons that are selective for the same location in the visual field
   they then used subthreshold stimulation of fef to test for modulation of sensitivity in the visual cortex
   -injection of current into the fef can see that there is actviity even if people do not move their eyes so this modulates the movement of endogenous attention

RESULT: subthreshold stimulation of the fef can enhance the v4 response

Question 19

What does stimulation of the fef cause for v4 neurons?

Answer 19

causes visual neurons to have enhanced sesnitivity as if the monkey were endogenously cued to attend to that location

Question 20

What does the role of the fef in the allocation of attention in visual space suggest? What did fmri show that supports this? What is the phenomenon known as?

Answer 20

that covert orienting of attention in visual space may be intametly related with motor planning for eye movement
-in fmri general overlps of regions involved in endogenous shifitng of spatial attention and regions involved in controlling saccadic eye movement is observed
-outside of the psychology laboratory a primary use of covert attention is to plan where to look next - maybe covert attention exapts evolutionarily ealry circuits for eye movemnt control
-phenomemon - premotor view of attention

Question 21

What are endogenous shifts of attention initiated by? and where do they engage sustained activity in?

Answer 21

initiated by frontal regions; engage in sustained activity in the parietal areas in the dorsal aspect of the IPS

Question 22

There is substantial overlap between attentional areas and areas involved in planning eye movements (i.e. in monkeys have seen that frontal activity can directly modulate the kind of enhanced visual responses we discussed last week) but what is the functional significance of this overlap?

Answer 22

-the functional significance is a matter of debate

Question 23

What is the interaction of bottom up and top down attentional processing in pop out salience?

Answer 23

-there is a strong bottom up component to visual salience - things that contrast sharply in context with their environment in color brightness motion exogenously draw attention
-we can exercise top down influence on salience in many cases - attention to features provides a window into this

Question 24

What does the behavioral phenomenon of pop out suggest? What happens when this fails?

Answer 24

there is some bottom up process of feature analysis that can search the visual field in parallel = however when this fails participants switch to a serial strategy moving their attention around the field in search of hard to find stimuli

Question 25

In pop out does the number of items in the display matter?

Answer 25

-in pop out it does not matter or affect the search because in pop you scan the whole visual field in parallel

Question 26

In conjunction search does the number of items in the display matter (looking for two criterion like a green T?

Answer 26

-yes it does because you are going serially so it takes longer the more items in the display
-when the target is not present the slope is even steeper with it taking even more time to serially look at the visual field as the number of items in display increases

Question 27

What is the erp component that indexes pop out? What and when is it? What does this wave indicate?

Answer 27

N2pc - a negative component contralateral to the item that pops out 200-275 ms after the array is presented - indicates a reorienting of attention of that location - this is top down because if you have a different stimulus from the target that is salient then there is no n2pc wave - it is specifically goal related

(can also see the p300 later on in this which is a positive response which denotes that something is being encoded into working memory)

Question 28

What does the n2pc seem to be driven by?

Answer 28

a simple match of a salient feature in the array to the target
i.e. if participants are looking for a small blue horizontal bar a large blue horizontal bar will elicit an N2pc even through it is later identified as a non target
-this clarifies that n2pc is related to reorientation of attention not to target detection or response generation

Question 29

Is pop out task related?

Answer 29

yes because easy non target in the study refers to items that differ sharply from the background but are not similar to the target and there was no n2pc for that

Question 30

What does a feature based model of attention focus on?

Answer 30

in addition to be being able to move an attentional spotlight to a location in space we are also able to direct attention to specific physical features of stimuli

Question 31

What is the feature based model of attention?

Answer 31

1. incoming stimuli
2. extraction of physical features
3. integration of features for selected object

(our ability to direct attention to specific features of stimuli)

Question 32

What is the filter model of attention?

Answer 32

It is a later selection model
1. incoming stimuli
2. extract all of the physical properties
3. filter
4. extraction of abstract properties

-basically extract all physical properties on a basic sensory levels but then later on you can enhance some features and diminish others
-the attentional blink phenomenon where some part of the brain processes your stimuli

Question 33

What happens when you shift your attention to one location and the target occurs in another?

Answer 33

responses to targets occurring in the uncued location are associated with reorientation of attention from the cued location to the target location

(took the endogenous attention experiment trials and only looked at the trials where the stimulus occured in an unexpected location via an invalidly cued)

Question 34

What regions of the brain were activated when an unexpected stimuli occurred in a noncued location and you had to reorient you attention from the cued location to the new uncued location?

Answer 34

-responses driven in right lateralized network (TPJ - temporo parietal junction); (middle frontal gyrus (MFG) and inferior frontal gyrus (IFG)
-this was seen in both visual and auditory stimuli studies

Question 35

What is the evidence for the two separate but interacting attention systems?

Answer 35

-there is a dorsal system involved in the intentional focusing of attention that may have evolved from systems for eye movements (FEF)

-there is a ventral system that responds to salient novel and or unexpected stimuli

-we are able to ignore relevant stimuli in order to focus on things that are important but we also want to be aware of unexpected and potentially relevant stimuli that occur outside of attentional focus

Question 36

How are the dorsal endogenous and ventral exogenous attentional systems related?

Answer 36

endogenous dorsal system has this feedback connectivity - controls the posterior parts of the brain with more anterior parts of the brain starting with the frontal cortex and the TPJ is part of the ventral stream and is right lateralized and can function as a circuit breaker which can shift our endogenous attention if needed to salient stimuli in our environment

Question 37

How was resting state functional connectivity used to distinguish between the dorsal and ventral streams of attention?

Answer 37

used subtraction methodology compare response of the expected and unexpected stimulus and show the different dorsal regions of the brain activate for endogenous and ventral for exogenous and TPJ functioning as circuit breaker for salient stimuli

Question 38

What does resting state connectivity provide?

Answer 38

a way of identifying networks that naturally hang together
-aka put someone in a scanner and do not give them anything to do and collected data for six minutes and we can see that there are low frequency motor cortex fluctuations in the bold response even when lying still and we do not expect it - this can be due to biological brain dynamics with activity fluctuating up and down
-can take volume in the motor cortex and summarize the activity over time and get time series and get time series and query other voxel and correlate the time series for voxel versus time series for seed volume and the voxels are going to be changing and increasing or decreasing in activity over time and see which ones are in sync with one another and which are not to see the resting state connectivity

Question 39

If a time series form the left motor cortex is extracted and then the time series from every other voxel in the data set is tested for correlations with this region, what is observed?

Answer 39

activity is observed in motor areas bilaterally and the thalamus and the cerebellum

Question 40

What patterns of activity during rest do the dorsal (IPS-FEF) and the ventral (TPJ-VFC) networks have and what is their relative overlap? What can this be attributed to?

Answer 40

at rest they have distinct patterns of activity and small points of overlap
-this can be due to spontaneous low frequency activity or attentional shifts during mind wandering and it suggests that these networks have different time courses

Question 41

What is the point of contact between the dorsal and ventral attentional system?

Answer 41

the TPJ - aka the circuit breaker

Question 42

Resting state fmri shows the coherent activity of the default mode network. What is the DMN?

Answer 42

-it is strongly inversely correlated with the endogenous attention system (IPS/FEF) and supplementary motor areas involved in task performance
-PCC and MPF and these are associated with tasks that are used in interpersonal cognition or affective connections and narrative comprehension so things which have a continuous nature to them like integrating a narrative for a long period of time - activity in this dmn is assocoiated with consciousness

Question 43

When clinicians are talking about eeg activity what are they talking about?

Answer 43

continuous activity

Question 44

What was seen in the study where they took eeg data on awake and alert healthy participants at rest vs patients in vegetative state?

Answer 44

healthy - at rest they have alot of energy at 10Hz
vegetative - dominated by 1-4Hz and some higher frequency muscle artifact

Question 45

What is a fourier transform?

Answer 45

converts a function of time or space into a function of frequency

Question 46

What is connectivity in the default mode network correlated with?

Answer 46

gross level of consciousness
-coordinating this default mode network is what it means to be awake and alert and conscious versus unconscious

Question 47

What was done in the Monti et al study where they asked patients who gave no overt sign of consciousness instructions to imagine playing tennis or walking around in response to yes or no questions?

Answer 47

BOLD activity associated with motor or spatial navigation was observed in response to autobiographical questions
-this is an amazing finding but even in the initial reports there are clear limits on how strong the link is between this kind of voluntary brain activation and evidence of consciousness

Question 48

What have studies of consciousness in healthy participants generally focused on?

Answer 48

awareness
-using bistable stimuli and asking participants to report when these flip

Question 49

What are regions associated with flips in bistable stimuli associated with?

Answer 49

areas involved in visual attention - superior inferior parietal cortex and the tpj which are involved in endogenous and exogenous attention so it is not clear which one
-the relationship between visual attention and consciousness is philosophical so we will not try to resolve it

Question 50

What is hemispatial neglect?

Answer 50

-occurs after a stroke or in alzheimers - people ignore one side of space so in the finger extinction task cannot see left finger until brought to center but when both left and right finger available only sees the right finger
-this is different from hemianopia because they cannot see one side - patients can realize something is wrong unless you point it out to the

Question 51

What were the results of the copying task in hemispatial neglect?

Answer 51

patients have difficulty attending to the left side of a display or object

Question 52

Why is left hemispatial neglect more common?

Answer 52

right hemisphere contralateral injuries are more common - this is analgous to less left visual attention

Question 53

What were the results of test with navon figures in hemispatial neglect?

Answer 53

-patients typically are able to name both the global shape and the local features correctly
-when directed to cancel out off the items they can only cross out items on the right

Question 54

What is the neuroanatomy of hemispatial neglect?

Answer 54

right superior temporal cortex and insula and subcortical putamen and caudate nucleus are neural structure affected in neglect

Question 55

What attentional areas are neglect symptoms associated with?

Answer 55

ventral attentional areas - play a role in reorientation but negelcty is very common and is ssoaicted with many regions outside the tpj, mfg, ifg network

Question 56

What are the cortical right hemisphere brain areas associated with negelect?

Answer 56

cortical right hemisphere brain regions have been associated with neglect - angular and supramarginal gryi of the inferior paritel lobe and the tpj

Question 57

Neglect is common in stroke patients from where can it arise from?

Answer 57

damage to any number of regions in a broadly distributed network typically right hemisphere regions
-patients have little difficulty in recognizing objects
-but they neglect the left side of whatever they are attending to (i.e. pick out an object and draw it see the boat the parts if the bears with fire serum are the parts of the boat on the right an pick up van but draw parts of van on right so have a bias to right side of the image and the can pick up an object and only focus on the right side of the object so it is the relative coding of space which determines where they allocate awareness)

Question 58

What are the three key symptoms in Balint’s syndrome?

Answer 58

1. optic ataxia - cannot reach for the object
2. simultagnosia - cannot bring other objects into awareness if attention is captured by one object
3. oculomotor apraxia - issue with focusing the eyes in voluntary way

Question 59

When a Balint patient was asked to judge whether the height of two uprights was the same what was found?

Answer 59

-they could perform well when the objects had colinear edges like a J or U shape but they were at chance when the uprights appeared to be separated as objects
-this is a double dissociation between space attention and object attention

Question 60

How did balint patients perform on Navon figures?

Answer 60

have difficulty resolving the global pattern (but reducing the space between local elements helps)
-can cross out all local features thought unlike hemispatial neglect patients

Question 61

What were the initial lesions of a balint syndrome patient?

Answer 61

bilateral posterior parietal lesions - also some occipital cortex
-but because the syndrome is rare anatomical descriptions are sketchy

-overall takeaway can have lesions in the attentional system which can affect object attention or sptial attention

Question 62

What is the double dissociation between hemispatial neglect patients and balint syndrome patients?

Answer 62

hemispatial neglect - unaware of the left side of whatever they are attending to - spatial attentional deficits
balint syndrome - can only select a single object for awareness at a time - object attentional deficits

-this means that - attention is location or object based
-attention selects from whole objects that are somehow formed pre attentively
-the process of identifying objects is distinct from selecting objects for awareness