attention Flashcards
what can selectivity of attention be demonstrated by?
- Inattentional blindness
- Change blindness
- Attentional blink
change blindness
Change blindness is a perceptual phenomenon that occurs when a change in a visual stimulus is introduced and the observer does not notice it
Inattentional blindness
occurs when an individual fails to perceive an unexpected stimulus in plain sight, purely as a result of a lack of attention rather than any vision defects or deficits.
Attentional blink
Attentional blink (AB) is a phenomenon that reflects temporal limitations in the ability to deploy visual attention. When people must identify two visual stimuli in quick succession, accuracy for the second stimulus is poor if it occurs within 200 to 500 ms of the first.
Types of attention
- Exogenous attention: bottom-up, (pre-attentive), feature search…
effortless .. leads to “pop-out” [For example. Spotting a red balloon
among a sea of blue balloons]. - Endogenous attention: Top-down….requires effort and takes time
and depends on task and clutter [E.g., finding Waldo; looking for a
face in crowd].
Types of endogenous attention
- Spatial attention: helps to confine processing to a particular
location/object (e.g., focussing on the road while driving) - Feature-based attention: helps to process all objects sharing a common
feature (e.g., all red cars in a car park)
what type of attention is looking for a face in a crowd?
Looking for a face in a crowd:
Endogenous attention (serial search)
Diff btw parallel and serial
In serial search, only one stimulus is attended at a time, whereas in parallel search, several stimuli are attended at the same time.
What is tresiman feature integration theory?
Postulates an attentional spotlight (‘covert attention’) acting on a visual area or areas early along the visual pathway that aids in
early selection of visual field location for further processing.
Difference between parallel search and serial search.
Parallel search: Pre-attentive (pop-out)
Serial search: Deploys attention (takes time)
IPL
inferior parietal lobe, possible source of attentional spotlight.
what do brain scans reveal about attentional spotlighting
Shows attentional spotlight as attention is swept across sectors of a visual scene. what is
maximal activation is where the person is paying attention to.
So it shows this kind of spotlight of attention can
be can be can be actually demonstrated, even at the
level of the primary visual cortex.
how are MT and LIP recieve signals ?
The signals from, uh, from the eye go to the
V 1 and primary visual cortex.
It, um it goes to a number of areas, but
to the L IP.
Here it goes via MT.
To L IP.
And there are feedback area feedbacks.
The reciprocal connections are there.
Which means there’s always feedback connections from the parallel cortex
to MT/ and from MT to V one.
describe the neural mechanism that underlie the attentional
modulation of one brain region by another
Neuronal oscillations and
synchrony may be the
mechanism the way attentional
modulation works.
normally the LIP cells, the higher area here are out of sync
firing away and you know, the MT cells are also
firing out of sync.
But once attention is captured by the first stimulus right after that, these L IP neurons are firing together
for a while, right?
And the firing together, the LIP neurons also project to the MT neurons and the corresponding location.
And they also cause these to sync .
it’s a kind of a neuro oscillation. if you look at membrane potential, will change right from hyper polarised to less hyper depolarizes so that it comes close to spike threshold that will also be changing, which means to get to reach spike threshold.
When you get a lot of action potentials, you don’t
have to raise the membrane potential all the way.
Whatever comes in here, the next stimulus can ride on the peak peak on the peaks of these right, and they come
and they come to threshold and fire nicely.
This is the response you see for the second stimulus.
- describe the role played by posterior parietal cortex in attention
Posterior parietal cortex prevents the binding problem. People with damage to the area have trouble combining features together. They haveillusory conjunctions.
*describe the limitations of multitasking
Often, so called multitasking is simply multiplexing, i.e., switching of
attention between two tasks
* When one does 2 demanding tasks at the same time with divided or
switching attention, performance is poorer in both tasks.
* Capacity is limited by: attentional blink, visual short-term memory
(VSTM) and psychological refractory period. [Marois & Ivanoff (2005)
Trend in Cogn Sci., 9: 296-305].
* VSTM itself is limited by attention, since attention needs to be
maintained at a location for encoding and also for integrating and unify
the information.
* Chronic ‘multitaskers’ are easily distracted and cannot easily
discriminate between what is relevant and what is not
How is attention and ventral stream and dorsal stream working together?
Attention actually works together with the with the with the
with the ventral stream to help you to focus attention
on a particular location and process the object in all
its details. It shapes it colour. and other attribute.
There is a neural substrate for dorsal areas to gate what goes into the ventral areas (attentional modulation of one brain region to another)
What is the bindign problem?
-Different stimulus attributes (form, colour, depth,
movement, etc.) are processed in different cortical areas.
* Most extra-striate receptive fields are large, so they
cannot code the locations of objects.
* How then do we correctly combine the features of one
object?
What are some conditions where visual attentional
mechanisms may be impaired:
- Hemispatial neglect
- Attentional Deficit Hyperactivity Disorder (ADHD)
- Schizophrenia
- Accidents - in traffic, using heavy machinery, etc.
- Sleep disorders.
- Developmental Dyslexia
- Acquired dyslexia.
What solutions are there to the binding problem?
2 solutions:
1. Treisman’s Feature Integration theory: The spotlight of attention acting on an early visual area aids in the selection of a visual field location for further processing. Thus, binding errors do happen in posterior parietal cortical lesions.
- Another solution is synchronisation between neurones that code for
features that belong to the same object
- Another solution is synchronisation between neurones that code for
Dyslexia
A huge amount of data has shown that eye movements are abnormal in dyslexia. Dyslexic individuals exhibit longer duration of fixations, shorter saccades and thus more fixations in reading than normally developing readers of the same chronological age.
An alternative suggestion has been gaining ground that the core deficit in dyslexia is in visual attentional mechanisms. If so, the visual aetiology may be at any of a number of sites along the afferent magnocellular pathway or in the dorsal cortical stream that are all essential for a visuo-spatial attentional feedback to the primary visual cortex.
Explain the role of attention in dyslexia?
It has been suggested that the same circuits and pathways of top-down attention used for serial visual search are used for reading. Top-down signals from the dorsal parietal areas to primary visual cortex serially highlight cortical locations representing successive letters in a text before they can be recognized and concatenated into a word.
How do top down mechanisms operate in visual attention?
We had shown in non-human primates that the mechanism of such a top-down feedback in a visual attention task uses synchronized neuronal oscillations at the lower end of the gamma frequency range
