Transcript No Slide Title

Psych 216:
Movement
Attention
What is attention?
Covert and overt selection appear to recruit the
same areas of the brain.
Imaging studies of attention
• Functional imaging studies have been conducted in which
blood flow or oxygen consumption in the brain was measured
while visual attention tasks were performed by to determine
what parts of the brain control covert attentional selection.
• These studies show parietal lobe activation during visual
search and cueing tasks. This activity is consistent with
several existing hypotheses.
– 1) That parietal cortex controls the voluntary orienting of
attention to a location of interest.
– 2) That parietal cortex controls the reorienting of attention to new
locations once one object or location has been attended.
Corbetta et al. (2000)
Measured blood flow while subjects performed a cueing task.
Frontal-parietal network
QuickTime™ and a
decompressor
are needed to see this picture.
Is attention just movementrelated activity?
• Because similar brain areas are active when people
shift gave and shift attention, researchers have
proposed that shifts of attention are simply due to
subthreshold activity in the neurons that control gaze.
• This is known as the premotor theory of attention.
– “There are no such things as selective attention circuits
defined as anatomical entities separted from the spatial
maps [that perform goal-directed, spatially coded
movements].” Rizzolati, Riggio, & Sheliga
Premotor Evidence
• Shifting attention to more eccentric locations takes
more time and horizontal shifts are slower than
vertical. This pattern is similar to what is found when
people make eye movements.
Rizzolatti et al. 1987
• A shift of attention appears to precede a shift of gaze
to a location.
Kowler et al. 1995
– Difficult to attend to one location and make a saccade to a
different location
Stimulating a oculomotor area
and covertly attending
QuickTime™ and a
decompressor
are needed to see this picture.
Visual-response discriminability of V4 neurons
Armstrong K M, Moore T PNAS 2007;104:9499-9504
©2007 by National Academy of Sciences
Subthreshold FEF microstimulation enhances V4 response discriminability
Armstrong K M, Moore T PNAS 2007;104:9499-9504
©2007 by National Academy of Sciences
However, …
• The areas that are active during shifts of attention
and control shifts of gaze have a diversity of cell
types.
• Microstimulation in a brain area can effect all of they
different cell types.
• Showing that attention and eye movements have
similar spatial characteristics and may interact does
not mean they are the same thing.
– Remember the differences in timing we talked about last
class.
Let’s consider some evidence for
which the premotor theory has
difficulty accounting
• The oculomotor structures (like FEF, LIP, & SC) have
a diversity of cell types within them.
Let’s consider some evidence for
which the premotor theory has
difficulty accounting
• Movement related cells in oculomotor structures (like
FEF or SC) are not wired to visual cortex in the back
of the brain (V4, etc.) where attention effects are
observed.
Green = connected to
visual cortex
Red = connected to
SC
Other attention effects
• Object-based attention
– These are attention effects in which attention is deployed to
one of two spatially overlapping objects which are both
fixated.
• Negative priming
– Attending to one of two spatially overlapping objects causes
long-lasting suppression of the distractor.
Conclusions
• The structural (connectivity of different types of
neurons), physiological (responses of different types
of neurons within an area), and psychological
(evidence for attention effects that are not spatial)
evidence does not support the proposal that attention
is just movement-related activity.
• So, what is it. Mechanisms of selection (I.e.,
attention) appear to exist throughout the brain to
resolve competition.
– To recognize objects one at a time, make one
response at a time, store some information in
memory and not everything.