TB7 Flashcards
(42 cards)
What does the Cocktail party effect tell us?
Subjects report attended stream well but little of unattended stream TF attention is limited, unattended info filtered out early and it varies across individuals
Overt vs covert attention
Overt- direct senses to location of interest
Covert- attend to location of interest WITHOUT DIRECTING SENSES (fixation point and stimulus in different places)
What is early vs late selection?
Which stage the info is filtered depends on the task. Where we see modulation suggests early/late selection, early areas like V1 suggest early and higher areas suggest late
What functions does the parietal cortex have?
Wide variety of functions in parietal lobe so deficits vary wildly too, more than ventral steam . Eg space based attention, object based attention, reaching and grasping, magnitude processing (how many objects), feature based attention (attending to parts of an object)
Hemispatial neglect symptoms
Patients ignore the left side of space and only attend to the right, due to RIGHT PARIETAL DAMAGE.
-some can attend when it’s pointed out to them
-eye tracking supports
-due to fact right hemisphere represents both sides of space but left is less dominant for visuospatial attention.
-TMS experiment of parietal cortex disrupted spatial attention but no effect on trained task. So parietal cortex important for NOVEL spatial attention
Issue in EXOGENOUS network
Balint’s syndrome symptoms
Bilateral parietal and occipital lobe damage
1.simultanagnosia - object based attention (see 1 at a time)
- optic ataxia- issue reaching and grasping eg patient RV. Postbox task shows lesions in inferior parietal lobe cause issues.
- oculomotor apraxia- problem with eye movements due to deficit in FEF and parietal lobe circuit
Balints patients have lesions in ENDOGENOUS network
Dyscalculia
Developmental problem with Understanding and manipulating numbers. May be localised in right inferior parietal lobe.
Price- loss of right intraparietal sulcus on the numerical distance effect task
They also have issues reading analogue clocks, time tables, conceptualising time and doing dance steps etc
ATOM- Walsh (a theory of magnitude)
Parietal lobe represents magnitude which includes time space and number! All share rIPS
What do blindsight patients suggest?
They’re better at chance t detecting things so suggests another route than V1, eg patient DB can do tasks when ‘guessing’. Perhaps uses frontoparietal network of attention (unconsciously).
Also better with detecting fearful stimuli and activation in amygdala and FFA increased despite no consciousness of the stimuli
Endogenous vs exogenous attention
Endogenous is consciously directing attention and exogenous when externally occurring events draw our attention automatically
When does consciousness begin?
Some argue begins at the later stage of selection/ attended stage, when we can make decisions so at 100ms when the parietal cortex becomes aware and can do top down control: rather than the preconscious stage at 40ms.
Lamme.
What’s the difference between using ERPs and fMRI when studying attention?
ERPs are precise time wise but not space - can only tell you the hemisphere it’s in
FMRI is slow but spatially precise.
When using ERP use time to tell if early or late selection but with fMRI by area eg early selection if V1-4 and late for parietal and frontal cortex
Crossmodal evidence of higher areas affecting lower visual areas
When sound looming towards subjects, their phosphene detection rates increased
And can use touch to prime vision as using fMRI found greater activity when touched same hand as side of visual stimulus, and enhanced parietal connections seen
What do fooling effects of V5 in macaques show?
Reduced neural activity spikes in V1/2/3 when cooled V5 (mostly V2) therefore V5 can modulate lower visual areas
Evidence of re-entrant activity in human experiments
In ERP experiments top down control seen when told to attend to one of 2 stimuli (left or right both on at once) as til down feedback switches visual system on 100ms after stimulus. (Know from TMS)
2 peaks- P1 to attended stimuli and P2 to second, so till aware something is there
Effect of attentional load on brain activity with fMRI?
Higher load means less V5 activity (same as cooking experiment shows visual attention can be modulated)
And for faces when ignoring faces there’s less FFA activity than passive viewing
Where do the streams project to?
Dorsal stream (parietal lobe) projects to motor system Ventral stream (temporal lobe) projects to semantic memory area
Continual interaction between the 2 and visual info spreads across brain
Brain areas for top down control
IPS- neglect - spatial attention
Superior parietal lobule
FEF
SEF- supplementary eye fields
Can be found with fMRI if subtract interpret areas from attending areas get just medial areas in frontal and parietal lobes
(Frontal is 200-300ms before parietal!)
Auditory attention
A1 is in superior temporal gurus and Herschl’s gyrus
Attended ear elicits greater ERP and evidence for early and late selection found with N1 in attended ear and P300 for deviant tones, and P20-50 component is much earlier than vision and modulated by attention
Stages are brain stem activity, them mid latency responses, then late waves
How can audition affect vision??
TMS study Beachamp audition
TMS over STS disrupted the McGurk effect so audition can also affect vision
Monkey study on FEFs and saccades- shows FEF involved in attention
FEF stimulated subthreshold and it produced enhanced V4 activity despite no saccade, so FEF plans shifts in spatial attention and part of control network!
Ideas for what the default mode network may be??
- shows more activity when at rest
- areas involved are posterior Cingulate cortex, mPFC, ventral anterior Cingulate cortex.
- anti correlated with FP network and any task
Less connected to hippocampus in Alzheimer’s, disrupted pattern in chronic pain (controls have more Ips than mPFC activity when doing task but patients don’t)
Resting state fMRI used and areas lit up seem functionally connected.
- seen in monkeys too
- can find brain hubs which lesions within cause more severe cognitive damage as integrate regions
- disrupted in autistic and schizophrenics too
Rest and it’s benefits
Resting state fMRI shows rest and sleep(stage 2) improve learning. Sleep may remove unwanted info and activity
-sleep stages have different EEG states with 2 and 3 being deepest (higher amplitudes and lower frequencies)
ERP studies in attention and how they can be combined
Space based attention- covert task flashing light in unattended or attended location. Greater ERP in attended location
ERP and PET- covert attention with symbols in left and right Vf, greater activity when in contralateral hemisphere to what they’re attending to. (Pet has poor spatial resolution though)
FMRI- can show organisation (upper goes to lower, left to right, retinotopically)
Combine with ERP- Martinez - covert attention task showed more activity in right hemisphere if attend to left VF. ERP can create heat maps showing attention P1 effect at 100ms and unattended ERPs pre attention (50-80ms)
Brain areas of the frontoparietal attention network-
Right IPS- spatial attention
FEF (both endogenous)
TPJ and VFC for unexpected events (exogenous)
And connection between IPS and TPJ can break into system if a salient stimulus
