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					An introduction to attention

        Peter König
                What is attention
Everyone knows what attention is. It is
the taking possession of the mind, in
clear and vivid form, of one out of what
seem several simultaneous possible
objects or trains of thought.
Focalization, concentration of
consciousness are of its essence. It
implies withdrawal from some things in
order to deal effectively with others,
and is a condition which has a real
opposite in the confused, dazed,
scatterbrain state….
          – William James (1890)
Overt attention

        • Movements of the
          eyes allow selective
          aquisition of visual
          signals.
        • Other sensory organs
          equally allow selective
          capturing of
          environmental signals.
Selection of signals by sensors
           sensory organ




        environmental signals
How are salient points selected?

                                      • The concept of a
                                        saliency map
                                      • “Where is the
                                        action?”
                                      • Bottom-up
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                                        approach
                                      • But … !
          Spotlight of attention

•      Helmholtz observed
that we can enhance
perception, if we focus our
attention on a location in the
visual field.
•      However, enhancing
perception in one part of the
visual field takes place at the
expense of other areas.
The shadowing task I




      Condition 1: 65% correct
      Condition 2: 20% correct
        Shadowing task II

Somewhere Among hidden the in most the
spectacular Rocky Mountains cognitive near
abilities Central City is Colorado the an ability
old to miner select hid one a message box
from of another. Gold. We Although do several
this hundred by people focusing have our
looked attention for on it, certain they cues
have such not as found type it style.
Covert attention
A physiological substrate I
Attentional systems
Plaza Milano
         Broadbend‘s filter theory
• Early selection.
• Selection is based on physical properties of the
  stimulus (e.g., pitch, loudness, etc...).
• Only one input channel can
  be processed at a time.             higher processing stage


• Semantic interpretation
  only after selection.
• Conscious control.
• It takes time to shift attention. sensory signals
                 Late selection



Attended Channel: THE GIRL WAS dogs, six, beach ...

Unattended Channel: world, eight, WAITING FOR HER ...

Reported: THE GIRL WAS WAITING FOR HER ...
                  Popout




• Popout as pre-attentive processing.
  The more popout, the later selection!?
• Can be trained!
          Stroop task

 red     yellow    blue    green

yellow   green     red      blue

 blue     red     green    yellow

green     blue    yellow    red
But!?
Effects in early visual cortex
Effects of attention
              Competing hypothesis
• early selection - Broadbent (1958) proposed that
physical characteristics of messages are used to select
one message for further processing and all others are lost
• attenuation - Treisman (1964) proposed higher processing stage
that physical characteristics are
used to select one message for
full processing and other mes-
sages are given partial processing
• late selection - Deutsch & Deutsch (1963) proposed that
                                             sensory signals


all messages get through, but that only one response can
be made (late selection).
The temporal domain




                V4
Applications?!
    What did we learn / the next time
• Overt/covert attention
• When: Early, middle, late …
• What: Spatial … Object oriented attention
• Where: Areas, -band … Single neurons,
  Clinical syndromes
• How: Saliency maps … Top-down models
• Suggested readings: Kastner, Annual Review
  neurosciences, 2000; JR Anderson, Chapter 3
        A definition by exclusion
              Awake               Asleep



Inattentiveness                    Different
                      Alert
(drowsy, relaxed)                  sleep stages




            Ignore       Attend
                  Popout


•   Popout as pre-attentive processing.
•   The more popout, the later selection.
•   T among I and Y vs. T among I and Z.
•   Can be trained!
Covert attention
Treisman’s attenuation theory
      higher processing stage




          sensory signals
          What did we learn?

• Types of attention
  – Overt attention, covert attention
• What can we attend to
  – Spatial attention, object based attention
  - Physical characteristics, semantic contents
• Properties of attention
• Mechanisms of attention
• Why attention
       What do we want to know?

•   Types of attention
•   What can we attend to
•   Properties of attention
•   Mechanisms of attention
•   Why attention
Selection by processing stages




                     higher processing stage




                         sensory signals
Parallel and serial search
Central peripheral cues
                Early or late?

Treisman and Geffen (1967) set about to test
whether the filter was early or late in the processing
stream. They had subjects shadow a message on one
ear, and tap whenever they heard a certain word in
either ear. When the key word appeared in the
attended ear, subjects tapped 87% of the time, but
when the key word appeared in the unattended ear,
subjects tapped 8% of the time. This indicates that
early selection is occurring.
Conjunction search
Lesions
Monkey cortex
What can we attend to?


    Spatially oriented attention
                 vs.
     Object oriented attention


Popout as a pre-attentive mechanism
Change blindness
         Divided attention
  Selective and divided attention

• Attention is studied by • In selective (focused)
  presenting participants    attention tasks, people
  with two or more           are instructed to respond
  stimuli at the same time. to one input only.
• This is called dual-task • In divided attention
  performance.               tasks, people are asked
                             to process and respond
                             to more than one input.
            Divided attention

• Tracking task. Can track several targets
  simultaneously.
     Dilation in space and time

• Expanding dot demo.
       Physiological mechanisms

• Partiel lobe lesions
• Balint‘s syndrome
• Attention is a gateway
  to consciousness.
Covert attention, cortex
Details of parallel search
Problems with spotlight
Spotlight or zoom-lens
Object centered attention
Scaling tuning curves
          Neuroscience <-> Psychology
what do these examples tell us about the relation between mental phenomena and physical
states of the brain?

*           unrelated ? complete independence -- too many corresponding phenomena
*           irrelevant ? somehow related, but without any serious implications -- unlikely,
because it is possible to influence percepts by affecting neurons (TMS)
*           correlated ? not independent, but possibly not more than common result from
unknown cause -- possible from the above, but perhaps not enough?
*           causal ? neuronal state determines mental state -- likely in some instances, but
applicable to all mental events? is consciousness emerging from neural activity?

if we would reach a complete understanding of all brain mechanisms, from the single
molecule to the function of extended neural networks, would we be able to comprehensively
predict mental states? A. Snyder (Centre for the Mind): Yes
                 Yet another definition
Attention - Attention is what enables us to process information about the world around us. We
can only be aware of things around us if we pay attention to them. We can think of attention as
a spotlight that we shine on things in the world around us to make them stand out. When
something "stands out," we notice it, bringing it into our awareness, and then process or
interpret it. Attention can change rapidly, switching from one thing to another. It can be
steered by our intentions ("top-down"), as when we look for a particular face in a crowd, or it
can be steered by features of objects in the world ("bottom-up"), as when our attention is
grabbed by a police car's flashing lights in our rearview mirror. Preattentive processes help us
decide what to pay attention to and what to filter out and ignore. Attention filters and feeds
information about the world around us into our minds

				
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posted:10/14/2012
language:English
pages:51