the spatial and attentive brain Flashcards
how does space in the brain exist?
locations on sensory surfaces
eg. retinocentric space
locations of objects relative to the body - egocentric space
location of objects relative to each other - allocentric space
in order to locate things in space…
use cross-modal perception
(integrating info)
what is attention?
process by which certain information is selected for further processing
and other information is discarded
limited capacity –> selection. based on relevance of goals
tends to be directed to locations in space - spotlight
needed to bind together different aspects of conscious perception
spotlight metaphor of attention
spotlight moves and can zoom in or out
location not necessarily same as eye fixation, but attention and eye fixation tend to go together
limited capacity - not everything illuminated
what controls the spotlight?
exogenous control (by stimulus)
IOR
Inhibition of Return: slowing of speed of processing when going back to previously
attended location
Endogenous control
Visual search: Scanning the environment to find something you are looking for
What is FIT?
Feature Integration Theory
Perceptual features (e.g. colour, line orientations) are encoded in parallel
and prior to attention
If an object has a unique perceptual feature, then it may be detected
without the need for attention – “pop-out” (left arrary)
If an object shares features with other objects (right array) then it cannot
be detected from a single perceptual feature and attention is needed to
search all candidates serially
“Pop-out” is not affected by number of
items to be searched
parietal lobes - “where”
specialised for spatial processing and have been called the “where” route”
parietal lobes - “how”
also bring together different types of spatial representation that are needed for action so also called “how route”
what are the two main attention related networks?
dorso-dorsal network
ventro-dorsal stream
what is the dorso-dorsal network?
involves lateral intraparietal area (LIP) and frontal eye fields (FEF)
what is the ventro-dorsal stream?
right tempo-parietal junction and ventral frontal cortex
interrupts any cognitive task in order to divert attention away from processing
hemispheric asymmetry of parietal lobes
Right parietal lobe contains richer representation of space (of left space and
some right space)
Left parietal lobe contains an impoverished representation of space (predominantly of right side only)
The greater spatial specialization of right parietal lobe means that we all
have a tendency to attend to left side of space (pseudoneglect)
neglect: how does a lesion affect attention?
Patients fail to attend to stimuli on the opposite side of space to their lesion
(a right sided lesion would affect the left side of the space)
Neglect is most prominent…
following stroke to the right hemisphere of the human brain
how could neglect arise?
- loss of neurons dedicated for representation of that space
- a failure to shift attention to that side
- some combination of the two
left parietal lesions…
can result in neglect which is less severe and faster recovery
clinical tests for neglect
line bisection and cancellation tasks
(only attend to/write/draw on one side of image)
Perceptual vs. Representational neglect
The brain contains different references for spatial and imagined events in external space.
Perception and imagery can dissociate at higher levels of visual processing ; in both cases
the information on the left side is compromised (RH damage)
what is representational neglect?
Neglect can affect memories of scene
Piazza del Duomo experiment: task
Two patients with large right parietal lesions were asked to
describe a familiar place according
to different perspectives:
1. imagine themselves
looking at the front of the cathedral
2. then reverse perspective
Piazza del Duomo experiment: results
Double dissociation between perceptual (line bisection) and representational neglect suggests
different spatial reference frames for external versus imagined (mind’s eye) space.
Also spatial knowledge not lost, but unavailable to report
Neglect for near vs. far space
Double dissociation between:
near space = line bisection using pen and paper – IMPAIRED
far space = SPARED when tested with a light pointer
Personal vs. peripersonal space
Double dissociation between personal (bodily) space and near space:
Body neglect = failure to groom left of body, notice
position of limbs, or feel pain in the left limb
Near space neglect = visual search of
array of external objects
Within objects vs. between objects
Some neglect patients attend to objects on the left side of space but omit to attend to one half of the object itself (object-based neglect)
Forms a double dissociation with space-based neglec
Spatial vs. Object based neglect
Axis-based neglect:
patient with object neglect cannot detect differences on left side of an object even when falling into right side of space
is neglect a disorder of attention or low-level perception?
attention bc:
Neglect patients still activate visual regions in occipital lobes for the information they claim not to be aware of
able to detect objects on the left if cued there
Affects auditory and tactile judgments as well as vision (e.g. sounds on left
are mislocalized but still heard)
Phenomenon of visual extinction suggests different perceptual
representations are competing for attention (and visual awareness)
Extinction
When two stimuli (targets) presented simultaneously to the left and right of the
patient’s midline – left target typically extinguished
What happens to neglected information?
Neglected information implicitly coded
- eg. Burning house
how to rehabilitate neglact?
prism adaption:
wear prism lens glasses that shift their view to the right
- so when they may miss the right, visual feedback allows them to compensate for errors and correct towards the left
- deviation to left persists when removed
Brain game
when searching for particular object, people who played video games regularly showed less activation in brain areas for attention
= brains performing the task more efficiently
what is TOVA?
Test of Variables of Attention:
assesses impulsivity and sustained attention
- press key as fast as possible in response to target
how to measure
sustained attention in TOVA?
- when targets are rare:
extent to which ps are able to stay on task and respond quickly to rare targets
how to measure impulsivity in TOVA?
- when targets are frequent:
extent to which ps are able to withhold responding to nontargets
NVGP vs VPG in TOVA
VGPs overall faster in both sustained attention and impulsivity condition
speed not at expense of accuracy, so overall enhanced attentional control
what is cognitive control?
set of neural processes that allow us to interact with our complex environment in a goal-direct manner
what is multi-tasking?
attempt to accomplish simultaneous goal
cost: % in accuracy decreases
NeuroRacer training results
60-85yr olds
EEG pattern resembled those of 20yrs.
The key change was in prefrontal cortex – suggesting
improvement in executive functions
Measures of coherence were much better – how well different
brain areas communicate with each other
