Attending and Spatial Brain Flashcards
What is attention?
The ability to select the stimulus, focus on it, sustain that focus and shift that focus at will
What three different forms does space exist in in the brain?
- Locations on sensory surfaces (e.g. the retina; retinocentric space)
- Location of objects relative to the body (egocentric space)
- Location of objects relative to each other (allocentric space)
What do we use in order to locate things in space?
cross modal perception integrating information from sight, sound touch ect.
What is the selection of attention based on?
Relevance or importance to current goals
Where does attention tend to be directed towards?
Locations in soace
What is the spotlight metaphor for attention?
The spotlight may move from one location to another (e.g. in visual search). It may zoom in or out (e.g. if atending to words or attending to a central letter in a word). Limited capacity: not everything is illuminated
Do eye fixations and attention always go together?
Location of attention is not necessarily the same as eye fixation (e.g. looking out of the corner of your eyes) however, there is a natural tendency for attention and eye-fixations to go together
What is exogenous control of attention?
- Externally guided by a stimulus
- e.g. if you hear a cry for help your attention will move to the space where the sound cam from
What did Posner show about the relationship between reaction time and presentation of a cue?
- no cue: people initially very slow but get better through practice
- cue closely related in time: people were significantly faster at detecting target
- longer time between cue and target: people significantly slower at detecting the stimulus
What is inhibition of return?
- slowing of speed of processing when going back to previously attended location
- When we have been cued somewhere and nothing happens our attention goes somewhere else. It then takes longer to go back to the previous space as it requires more attentional load
What is endogenous control of attention (internal attention)
Visual search: scanning the environment to find something yu are looking for
When is visual search the quickest?
when finding an image that only differs on one feature (e.g. orientation)
Why does it take longer to find a target that differs in more than one feature to the other targets?
Because you have to scan through lots of different items
What is the feature integration theory (FIT)?
- 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’
- if an object shares features with other objects 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 the number of items to be searched
Where is the where (dorsal) pathway located and what is important in?
The dorsal pathway reaches up into the parietal lobes and is important in processing information about where items are located and how they might be acted on guiding movements such as grasping
Where is the what (ventral) pathway located and what is it important in?
The ventral pathway reaches down into the temporal lobes and processes information that leads to the recognition and identification of objects
Why are parietal lobes also called the now route?
Because they bring together different types of spatial representation that are needed for action
What did Corbetta and Sherman find when they looked at deployment of attention when people were scanned in an fMRI scanner?
- Found two different routes depending on whether attention is deployed internally or externally:
1. A dorso-dorsal network involving the lateral intraparietal area LIP and frontal eye fields (FEF) when looking for things actively (internally)
2. Ventro-dorsal stream involving right tempo-parietal junction and central frontal cortex that interrupts any cognitive task in order to divert attention away from processing (external attention)
What does it mean that in humans there may be hemispheric asymmetry of parietal lobes?
- Right parietal lobes contain richer representation of space (left space and some right space)
- left parietal lobe contains an impoverished representation of space (predominantly of right side only)
- the greater spatial specialisation of the right parietal lobe means that we all have a tendency to attend to the left side of space (pseudo neglect)
What is the most widely quoted definition of neglect?
‘Fails to report, respond to or orient to novel or meaningful stimuli presented to the side opposite a brain lesion’
Is neglect due to a sensory or motor impairment
no but they can often co-occur
What is neglect also known as?
unilateral neglect, spatial neglect or hemispatial neglect
Do patients fail to attend to information on the same side of space or the opposite side of space to their lesion
- the opposite side
- e.g. a right sided lesion would effect the left side of space
When is neglect most prominent?
Following stroke to the right hemisphere of the human brain
What are the different mechanisms neglect could arise from?
- loss of neurons dedicated from representation of that space
- a failure to shift attention to that side
- some combination of the two
What is the neuroanatomy of neglect?
- cortical areas damaged in spatial neglect are mainly in the parietal lobe (right parietal areas and also in some frontal area)
- the lesion is in the parietal association cortex which integrated multiple sensory signals and has extensive connections with frontal areas
What did Mort et al find when he took scans of many neglect patients?
- That neglect was due to a specific overlap of regions in the right angular gyrus
But this finding is disputed: generally lesions in the parietal lobe will lead to neglect
Can you get neglect following left parietal lesions?
Yes but not as common
What modality most commonly shows neglect?
Visual modality
Can you get multimodal neglect?
YEs
What are clinical tests of neglect?
- line bisection
- Albert’s lines: cross all the lines you can perceive
- star cancellation: cancel the stars you can see
- copy a drawing
- draw from memory
How are the different types of neglect usually defined by?
Double dissociations
What is perceptual versus representational neglect?
- Perceptual neglect: if participant cannot perceive one half of space
- representational neglect: neglect that affects memories of scenes
- the brain contains different references for spatial and imagined events in external space
What experiment provides evidence for the double dissociation between perceptual and representational neglect?
The Piazza del Duomo experiment
What is the neglect for near versus far space and what evidence is provided for this?
There is a double dissocation between near space (line using pen and paper and far space (which is spared) when tested with a light pointer
- PET in normal participants: Weiss et al., near space and far space represented differently in space
What is the difference between neglect for personal versus peri personal space?
- there is a double dissocation 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 limbs
- near space neglect: visual search of array of external objects: movements just attend to the right side of space
What is the difference between within object and between object neglect?
- Some patients attend to objects on the left side of space but omit to attend to one half of the object itself (object based neglect - STG - superior temporal gyrus)
- this forms a double dissociation with:
- space based neglect - angular gyrus: will only copy image from one half of the picture
How do we know neglect is a disorder of attention and not low-level perception?
- neglect patients still activate visual regions in occipital lobes for the information that they claim not to be aware of
- they are often able to detect objects on the lect if cued there
What does the phenomenon of visual extinction suggest?
Different perceptual representations are competing for attention (and visual awareness)
What is neglect and extinction?
When two stimuli are presented simultaneously to the left and right of the patients midline the left target typically extinguished
What is the burning house experiment
although participant claims not to be able to see the smoke coming out the window they answer that they would prefer to live in the house that isn’t on fire
What is egocentric neglect?
With respect to the observer. E.g. line bisection
What is allocentric neglect?
with respect to another extra personal event; e.g. Piazza del Duomo
What is object centred neglect?
With respect to a principal axis in the canonical representation of an object
What is Prism Adaptation Rosetti in the rehabilitation of neglect?
Patients wear prism lens glasses that shift their view to the right. When asked to point at objects they make errors by missing to the right. However, visual feedback allows them to compensate for the errors and correct towards the left
What are the different roles of the parietal lobes and the hippocampus?
- the parietal lobe is primarily concerned with linking sensory and egocentric maps of space to create representations of observable environment
- hippocampus stores long term representations of space that need not be presently observed or even viewpoint specific
- these may sometimes work together; e.g. in the Piazza del Duomo experiment the hippocampus may store the map of the square and the parietal lobes may superimpose a viewpoint onto this map
What did Green and Bavelier find about video games and attention?
- participants trained in action video game much better at detecting contrast sensitivity, better at visual search task and significantly better at mental rotation tasks
- people who play at least 5 hours of action video games per week have fewer activations with areas devoted to attention compared to people who rarely played video games
- this is a sign their brains were performing the task more efficiently
What is TOVA (the test of variables of attention?
- TOVA assess impulsivity and sustained attention. In this test participants are required to press a key as fast as possible in response to a target (black square in upper position) and to withhold responding to non target stimuli (black presented in lower position)
- in one condition the targets are rare and the nontargets appear frequently. The extent to which participants are able to withhold responding to non-targets is a measure of impulsivity
What did Dye et al find when they used TOVA to assess impulsivity and sustained attention in young adults who were either non-video game players or habitual video game players?
Found that habitual video game players were significantly higher in both sustained attention of impulsivity paradigm but their accuracy was the same as non-video game players. There was no speed-accuracy trade off.
- shows that video game players were overall faster than non video game players in both the sustained attention and impulsivity condition
What are cognitive controls?
Set of neural processes that allow us to interact with pour complex environment in a goal direct manner
What did Anguera find when e tested the effect of being engaged in game playing tasks in older individuals?
- the working memory is much higher on the group that played the NeuroRacer game
- TOVA is much higher in he group that played the NeuroRacer game
- they were as good as multitasking as people who did the task for the first time in their 20s
- after NeuroRacer training the EEG pattern resembled those of 20 year olds with the key change in the prefrontal cortex
- measures of coherence were much better: the different brain areas communicate well with each other
What has been proposed to play an important role in the neural processes that underlie multitasking performance?
The dorsolateral prefrontal cortex (FLPFC)
What was shown when anodal tDCS pr sham tDCS was applied over the left dorsolateral prefrontal cortex in healthy young adults immediately before they engaged in a 3D video game designed to assess multitasking performance?
- The anodal group showed enhanced multitasking perofrmance and decreased multitasking cost during the second session suggesting delayed cognitive benefits to tDCS
