Transcript Spatial Neglect and Attention Networks

Spatial Neglect and
Attention Networks
Stephanie Regan
Antoinette Sellers
Alyssa Nolde
Hannah Stolarczyk
7. The Core Spatial Deficit and Our
Current Understanding
• Egocentric Bias
–Spatial neglect: represents a deficit
of spatial attention and stimulus
saliency that is mapped in the
egocentric reference frame
7. Continued
• Factor Analytic Studies
– Have isolated at least one factor associated with
impairments in attending, search, and/or
responding to targets in contralateral space
• Inconclusive in terms of other factors
• Classifying Patients
– Based on performance on different behavioral
tasks that are thought to isolate different subtypes
• Ex. Perceptual/ attention VS. motor/intention
– Not very consistent or relevant to recovery rates
What are measures of contrast sensitivity and
segmentation, are they impaired, and why
do the authors discuss them?
There is an abnormal early
visual mechanism, indicated by
normal measure of contrast
sensitivity and image
segmentation based on lowlevel features in the neglected
visual field and responses in
occipital cortex based on visually
evoked potentials and functional
magnetic resonance imaging.
What are measures of contrast sensitivity and
segmentation, are they impaired, and why do the
authors discuss them?
• The author discuss them
because…
– Almost all patients with spatial
neglect form a lateralized bias in
visual information processing.
– Sensitivity and responsiveness
to behaviorally relevant stimuli
generally improve as one moves
from the contralesional location
to the ipsilesional location along
the spatial gradient.
What are measures of contrast sensitivity and
segmentation, are they impaired, and why do the authors
discuss them?
– Contrasting the abnormal early visual mechanism,
the saliency of object in the neglected field is
impaired.
– Using task relevant or task irrelevant stimuli, a
study found that both stimuli produced an
increased probablity of eye movement along the
spatial gradient from contalesional to ipsilesional
locations.
– This suggest that automatic and goal driven
components of spatial attention are equally
affected.
Explain Figure 1 and the text that discusses it.
Panel A (Bays et al.)
• The 1st image shows the difference between ‘target’ and
‘probe’
conditions for letters in arrays.
• The 2nd image shows that targets (red) and probes (blue) produced more
saccades in the ipisilesional position than the contralesional position
• This provides evidence for the ipsilesional bias for automatic and goaldirected orienting in patients with spatial neglect
• The third image shows that lesions are localized or situated in the
temporoparietal junction
Explain Figure 1 and the text that discusses it.
Panel B (Fruhmann Berger et al.)
• The top graph shows that patients with neglect
show an ipsilesional gaze bias while target
searching (blue)
• Control patients show no gaze bias (blue)
Explain Figure 1 and the text that discusses it.
Panel C (Medina et al.)
• The first image displays ipsilesional bias
within an egocentric reference frame
(viewer’s point of view and midline)
What other functions besides attention or salience are
impacted in neglect? Tell us about the research into this
issue and what it’s shown.
• Proposed that neglect is a deficit in forming,
storing, or manipulating the left side of mental
images or information in VSTM, termed
representational neglect.
• Other aspects that could be included in
neglect are perceptual cognitive functions
such as, visuospatial short-term memory and
spatial cognition
11. Damage in which regions can contribute to neglect?
Is it necessary that lesions all happen in a specific
location, or not?
• Parietal Cortex
(specifically IPL)
– (TOP)
• Superior Temporal
Gyrus (STG), Inferior
Frontal Gyrus (IFG),
Anterior Insula, Middle
Frontal Gyrus (MFG)
– (BOTTOM)
11. Continued
• White matter fiber
damage can cause a
disconnect from the
frontal, temporal, and
parietal cortex
• Damage to the
subcortical nuclei:
– pulivinar, caudate,
putamen
– causes cortical
hypoactivation of regions
associated with neglect
11. Continued
• Some lesion sites are more likely than others
to produce neglect
• Lesions do not always have to be in a specific
location
• The big question:
– Why is it that neglect of the left field can be
caused by many different lesions in the right
hemisphere?
Figure 2
• Anatomical
regions associated
with neglect
• Shown by lesionsymptom mapping
• Lesion overlap in
patients diagnosed
with neglect
• Comparison of
patients with
severe neglect and
no neglect
These are quite similar and emphasize ventral regions in IPL
Figure 2
• Attention networks determined
by resting state functional
connectivity
• Yellow-Orange: regions with
strong positive temporal
correlation of activity at rest
• Anatomical distributions in
section “a” match distribution
of ventral but not dorsal
• Blue: regions negatively
correlated with dorsal
network, corresponds to
default network
Figure 2
• Blue and green: regions of
maximal damage in neglect
patients
• White matter tracts
corresponding to
arcuate fasciculus (AF)
and superior
longitudinal fasciculus
(SLF) II and III