Attention II: Control of Attention Flashcards
What is top down attention?
endogenous attention
What is bottom up attention?
exogenous attention
Do we understand the cognitive aspects of attentional deficit disorders?
no only the behavioral moreso
Do exogenous and endogenous cuing to spatial location have different temporal dynamics?
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
In what regions of the brain does endogenous or top down focus of attention involve?
sustained activity in the fronto-parietal network including
-the frontal eye fields FEF
-regions dorsal to the intraparietal sulcus IPS
Endogenous attention is what stream?
the dorsal stream
Exogenous attention is what stream?
the ventral stream
What was the endogenous cuing task in the Woldorff et al study?
-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,
What was the purpose of the variable interstimulus time area between 900 or 1900?
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
What areas of the brain did woldorff and colleagues identjfy that are specifically engaged by cues requiring an endogenous shift of attention?
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
What can we think of the frontal regions as doing in regards to the parietal regions when it comes to shifts in endogenous attention?
the frontal regions are somehow instructing the parietal regions to shift attention
What did the eeg activity correlated to in the temporal dynamics of endogenous attention in the woldorff and colleagues study?
slow and sustained activity in the medial frontal and parietal regions are consistent with the temporal dynamics of endogenous attention
In the woldorff and colleagues study when does general cue processing take place and when does attention processing take place? How was this determined?
general cue processing - 0-300ms
attention processin 400-1800ms
-this was determined via the inter[rect cue condition which does not havhe attentional shifts
What did source analysis of the woldorff and colleagues study show?
-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 -
What could the parietal lobe be in contact with in regards to endogenous attentional shifts?
the visual cortex to increase response
What did the colby and goldberg study in endogenous attention in monkeys show?
-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)
What is the LIP representing in the colby and goldberg study in endogenous attention in monkeys?
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)
How did experiments by Moore et al test the casual role for the fef in endogenous attention?
- identifying fef neurons that when strongly stimulated evoke a saccade to a specific location in the visual field
- 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
What does stimulation of the fef cause for v4 neurons?
causes visual neurons to have enhanced sesnitivity as if the monkey were endogenously cued to attend to that location
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?
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
What are endogenous shifts of attention initiated by? and where do they engage sustained activity in?
initiated by frontal regions; engage in sustained activity in the parietal areas in the dorsal aspect of the IPS
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?
-the functional significance is a matter of debate
What is the interaction of bottom up and top down attentional processing in pop out salience?
-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
What does the behavioral phenomenon of pop out suggest? What happens when this fails?
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
In pop out does the number of items in the display matter?
-in pop out it does not matter or affect the search because in pop you scan the whole visual field in parallel
In conjunction search does the number of items in the display matter (looking for two criterion like a green T?
-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
What is the erp component that indexes pop out? What and when is it? What does this wave indicate?
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)
What does the n2pc seem to be driven by?
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
Is pop out task related?
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
What does a feature based model of attention focus on?
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
What is the feature based model of attention?
- incoming stimuli
- extraction of physical features
- integration of features for selected object
(our ability to direct attention to specific features of stimuli)
What is the filter model of attention?
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
What happens when you shift your attention to one location and the target occurs in another?
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)
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?
-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
What is the evidence for the two separate but interacting attention systems?
-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
How are the dorsal endogenous and ventral exogenous attentional systems related?
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
How was resting state functional connectivity used to distinguish between the dorsal and ventral streams of attention?
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
What does resting state connectivity provide?
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
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?
activity is observed in motor areas bilaterally and the thalamus and the cerebellum
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?
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
What is the point of contact between the dorsal and ventral attentional system?
the TPJ - aka the circuit breaker
Resting state fmri shows the coherent activity of the default mode network. What is the DMN?
-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
When clinicians are talking about eeg activity what are they talking about?
continuous activity
What was seen in the study where they took eeg data on awake and alert healthy participants at rest vs patients in vegetative state?
healthy - at rest they have alot of energy at 10Hz
vegetative - dominated by 1-4Hz and some higher frequency muscle artifact
What is a fourier transform?
converts a function of time or space into a function of frequency
What is connectivity in the default mode network correlated with?
gross level of consciousness
-coordinating this default mode network is what it means to be awake and alert and conscious versus unconscious
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?
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
What have studies of consciousness in healthy participants generally focused on?
awareness
-using bistable stimuli and asking participants to report when these flip
What are regions associated with flips in bistable stimuli associated with?
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
What is hemispatial neglect?
-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
What were the results of the copying task in hemispatial neglect?
patients have difficulty attending to the left side of a display or object
Why is left hemispatial neglect more common?
right hemisphere contralateral injuries are more common - this is analgous to less left visual attention
What were the results of test with navon figures in hemispatial neglect?
-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
What is the neuroanatomy of hemispatial neglect?
right superior temporal cortex and insula and subcortical putamen and caudate nucleus are neural structure affected in neglect
What attentional areas are neglect symptoms associated with?
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
What are the cortical right hemisphere brain areas associated with negelect?
cortical right hemisphere brain regions have been associated with neglect - angular and supramarginal gryi of the inferior paritel lobe and the tpj
Neglect is common in stroke patients from where can it arise from?
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)
What are the three key symptoms in Balint’s syndrome?
- optic ataxia - cannot reach for the object
- simultagnosia - cannot bring other objects into awareness if attention is captured by one object
- oculomotor apraxia - issue with focusing the eyes in voluntary way
When a Balint patient was asked to judge whether the height of two uprights was the same what was found?
-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
How did balint patients perform on Navon figures?
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
What were the initial lesions of a balint syndrome patient?
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
What is the double dissociation between hemispatial neglect patients and balint syndrome patients?
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
