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Visual information processing in hemispatial neglect
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Visual information processing in hemispatial neglect Regina
McGlinchey-Berroth
he&space.
Despite
a great deal of visual of patients
T
he disorder
of unilateral
the most striking an acquired
disorder
acknowledge,
report
formation
falling
the responsible
hemispatial
of all neuropsychological marked
in the visual
lesion.
make hemispace
This disorder
information
in certain
neglect
tasks.
inability
explicit
It is to
use of in-
contralateral
to
can be just as severe and
Copyright
0 1997, Elsevier
Science Trends
awareness,
processing The current
debilitating
is perhaps
syndromes.
by an individual’s
or otherwise
this lack of phenomenal
noted:
does occur and can review
will preseW
as disorders
‘the patient
universe
oflanguage
may behave
had abruptly to a number
intention
or peripersonaVpersona1).
Cognitive
reserved.
or memory. almost
disorder
according
in
t&k
As Mesulam’
as if one half of the
ceased to exist in any meaningful
It is a very heterogeneous
Ltd. All rights
recent
ofdifferent
schemes (such as attention/ It can be demonstrated
1364.6613/97/$17.00 Sciences
-
form’.
and patients can be classi&d
Vol
PII: 5136&6613(97)01016-4 1,
No.
3,
June
1997
McGlinchey-Berroth
- Visual
in the somesthetic,
auditory
the fact that the primary systems are often intact. as a deficit rather
than a deficit
following observed 2,3).
Thus,
hemisphere
Similarly,
of neglect
attend
bias to ignore instance, ductor
Critchley”
Unlike
many
extremely
the case of an orchestra
con-
visual
on one side of the
with
hemispatial
(such
ration
of the disorder
companying following
damage
and subcortical’,‘, permanent
‘A’)
arrayed
For example,
to a number
weeks to months
range
Jackson
attributed
speech.
He felt that visual
parietal
lobe and when
this patient’s
objects
imperception
ideation
damaged
to a loss of cortical
sensibilities’z,‘3.
neglect
arose from
in either
devastating
three-dimensional
for recove$.
areas effectively is
body
and du-
image.
spatial when
may be observed
‘amnesia’
both
cortical with
body wiped BrainI
the LH,
argued and
were
from
visual
cognitive
of hemispatial theorists
B
psychology
disorientation
that
and
Brain
than
who
Berti’”
derived
to understand
For example,
Bisiach
a representational
ac-
based on the finding only
account
a neural
and
represen-
centers which responsible
space awareness.
space using viewer-centered Damage
D
to these brain
to a deficit
ing.
Riddoch
impaired Examples of the performance of patients on clinical tests of hemirpatial neglect. (A) Symbol and (B) letter search performance reflects the inability to respond to targets to the left of midline. (C) Line shows the typical rightward bias of patients’transections, suggesting that they perceive the left end of as being shifted rightward. (D) A patient’s copy of a person showing the lack of detail for features to the the patient’s midline.
Cognitive
Sciences
- Vol.
lead to
stimuli; that
improved neglected
1, No.
3,
June
1997
and
orienting
finding
occurs
this theory
side
of
the
and colleagues”
have
because
of
to contra-
is based on the
bisection patients
ne-
process-
HumphreyslY of attention
line
when
attribute
in attentional
that neglect
lesional
Heilman
in
areas will
of theories
glect
suggested
Trends
code
coordinates.
neglect. A number
Fig. 1 search bisection the line left of
for
Furthermore,
they suggest that these brain centers
C
a the
that asserts that space is
in several brain and are jointly
conscious
from
side of space. Rizzolatti
represented interact
image
information
have advanced
tational
that pa-
are asked to visually
ipsilesional
L
in the
concepts
neglect.
postulated
scene report
B
an
felt that the
and neuroscience
tients 2
F ’ (3
suggested
neglect.
count’6,‘7
D
lobes mediated
and
role in these functions
hemispatial
n
of these
side of a person’s
use contemporary
has
A
of our
to either
resulted.
important
lobe
a representation
schema,
damaged,
believed
parietal
and was thus the first to note an asymmetry
Modern
One
Pick’*
that the parietal
body
to name attributed
the right
Damage
for half of the body
lateralization
several
image.
in
in the right
writers
out the contralateral
RH may play a more
any
(such as hemianopia from
they
early
he felt contained
perception
or absence of ac-
in duration
which
of
to a defect
led to an inability
Other
damage
feature
was located
neglect
neglect
and places.
to have left
clinical
(see
and can, in some cases, be permanent.
A
a RH
of the left half of space.
that
of structures,
or sensory dysfunction and it may
outstanding
suggesting
the severity
neglect
most
was her ‘imperception’
of the line
disorders,
to both
The
be diagnosed
persons,
it may or may not be associated
motor
or hemiplegia)
to de-
would
line
prognosis
as well as the presence
disorders.
the first person
was probably
today
oriented
can be a functionally
regard
on left to be
neglect”.
this patient
neglect
as the letter
of a horizontally
neuropsychological
of
focus
following
Jackson
portion
with
likewise
are intended
who
midpoint,
other
variable
will
developed
scribe a patient
a very unfavorable
and for
underpinnings
information
For
the left-most neglect
carrying
review
of investi-
accounts
or thalamus,
Hemispatial
focus
of neglect
multimodal.
Fig. 1). disorder,
they
for visual
Theoretical
of the actual
are neglecting
that
the constructs
John Hughlings
on rhe left side of a page of randomly
to be to the right they
neglect
although
and
the middle
the primary mechanisms
This
The
stimuli
completely
of the neuroanatomical
or sentences
tests, patients
and judge
lesion,
unand
the non-neglected
of words
all of the musicians target
has been
in humans.
hemispatial
may only
side of the body4.
only
neglect
on only one side of space’.
reported
clinical
that appear
in the every-
a patient
or even deny
into the underlying
neglect
are often
of the environment
(anosognosia)“‘.
the delineation
Refs
one side of space can be very pronounced.
fail to cross-out
letters
can be found
parts
gations
is that patients
representation
minimize
Visual
and severely (LH;
recovery
have any deficits
or moving.
damage
complicating
consequently
but it has been
the non-neglected
and events
who ignored
stage! On will
damage
he or she may eat from to people
feeling
For example,
read only
factor
aware of their limited
and searching,
with left hemisphere
shave, dress and groom
despite
and projection
touching
(RH)
of the patient.
side of a plate,
modalities,
occurs most commonly
Demonstration
day activities
neglect
neglect has been characterized
in seeing, hearing,
in patients
in
receiving
listening,
neglect
right
and visual sensory
in looking,
Hemispatial
processing
performance
were cued to the line.
Similarly,
suggested
that
McGlinchey-Berroth
:I
Th’ IS IS a cognitive
‘~j mantic :
paradigm
memory
that
assesses
by determining
has on behavior
without
what
requiting
the contents
effect
of se-
semantic
the subject
to make
-
the target
has already
context
activation
of the prime.
explicit
a related
target
process
the prime,
will
without
i
get stimulus
related
to the prime
;
stimulus
cation
in
:
sponses
are typically
related
to the priming
/, ,_
to which
is related
of time (‘facilitation’)
spread
,:
as a more
,.i
of the
4
activation
!
target
‘f*-:a’;:a:
the
strategic stimulus
to the prime,
response
times
controls
Given
processor
hemispatial
neglect.
neglect
orienting
to the ipsilesional this deficit,
posed
that
stimuli
presented for
there
cently.
:
in some way,
left
the lateral
with
simultaneous
hemi-
patients when
two stimuli
a are
(which
of a single stimuli)
pro-
sented
from
better
have
several
paradigms
processing
use an
patients
are
frame-
in each visual field.
the actual
fate of
until
visual patients
space,
using
three
of processing the neglected
errors.
‘mailman’
RH For
achieved hemispace
infor-
was spurred
often
example,
as ‘milkman’. cross-field
retain patients
may
residual
visual
semantic
a comparison Berti
Trends
in
task equated
Cognitive
later
in the left replicated
in
et al.
They even
concluded
matching
and two differ-
found
Farah
level.
may simply
This
naming. three
a forced-choice
Vol.
who To
patients
the
stimuli argued
ex-
on a cross-field
information
1,
examine with
discrimination
of visual
-
that
with
interpretation,
et aP’
performance
the amount
Sciences
objects
be an easier task and
than
et al. tested their
that patients’
in the condition
by Farah
analysis
task by identical,
that unattended
to a categorical
and
physically
viewpoint
chance
represen-
matching
of the two different
and compared
matching
stimuli:
was later challenged
this possibility,
which
whether
even though
the level of visual
a different
less perceptual
tinction
performed
presented
were
with
one pre-
patients
the cross-field
the same name.
was above
processed
require
and ex-
simultaneously,
the picture
of ‘same’
but from with
that cross-field
word
Since that time, matching,
were
however,
and WarringtonZ5
lesions
have been used to explore
in neglect including
for
neglect
were presented
the same or different,
to perform types
same object
in hemispatial
less severe
the presentation
between
Surprisingly,
et a1.30 manipulated
required
required
some clinicians
with
findings
side
to the ipsi-
clear signs of severe visual neglect’“,2”.
tation
and can influence
in which
they were asked to indicate
These
with
to double
of diagnosing
Patients
to name
(LVF).
with
Berti
re-
were
unable
field
may
patients
contralesional
they were in
method
of two pictures
than chance when pictures
patients
side of space. Although
controversial.
displays
four
‘Extinction
the relationship
remains
the two
impairments
processing
of Kinsbourne
the word
studies
simultaneously
may not be apparent
a valuable
to some degree
are presented
neglect
hemispace,
the
with
misread
limited-
on the contralesional
as a useful
to disengage
about
on by the observations reading
lexical
and
refers to a phenomenon
the stimulus
take extinction
this view
that even though in
information
in their
from
in the neglected
tested lesion.
lateral and contralateral
side of space.
who length
theory
i=
stimuli
RH damage,
and his colleagueP
attentional
of RH
stimulation’
ent objects
that patients
retrieval
in which
than the left-
neglect
noted
as
paradigm
fail to report
latetalized
in the neglected
within
activation
tasks. Most
and Gazzaniga”
as a result
exacer-
inability
matching
extinction
Perhaps
of information
falling
I), and flanker
Le Doux
side of space”-“.
was known
is processed
Cross-field
same name.
mation
if no
known
activation
_
to identify,
tinction
have shown
in the level(s)
than
Gen. 106. 226-254
;
of awareness’”
performance
Interest
(il,
criterion
strong
the
visual
J. Exp. Psycho/.
,(. ~.,,
and
spreading
(see Box
Volpe,
implicitly.
Implicit
priming
priming
overly
have provided
information
lo-
is actually
be longer
A spreading
objective
demonstrate
these theories
be unaware
to be
Rev. 82. 407428
Semantic
attention
,‘:::>
hemispace.
and produces
Consistent
Posner
falling
behavior
‘potent’
is unopposed
in the ipsilateral
Studies
L.
the
orienting
Following
characterizing
information
control
and
to the left and right
is more
patients
little
target
will
is not
to a specific
a phenomenon
E.F. (1975) Psycho/.
roles of inhibitionless
asked
are op-
that the rightward
is a selective
relatively
there
in the right
in the RH).
orienting
that
processors
in the LH)
that
neglect,
residing
He argues
findings
and Loftus. processing
J.H. (1977)
for
this line of argument
suggests
and action
(located
because
Neely, capacity
(i
to the
neglect
lesions
A.M.
memory:
both
to
orienting
time
to
to that space and, thus, cannot
These opponent
bating
b
if the
because
orienting
this lateralization,
systems
(located
While
are faster
controls
right-sided
attention
of attention
the LH’s
work
LH
following
attentional
marked
attentional the
Kinsbourne
processor
cause thus
attention
generated,
This
the target
an unrelated
response
that
time rhan when
alone”.
expects
directing
had been
of semantic
* “g --i (i ii ‘, ;
space, respectively. ward
a Collins,
presentation
in memory;
is grearer
activation
but
the subject’s
expectancy
sufftcient
References
as well
to automatically
for the RH loss. Taking
processor
The
(thus
memory)
by the spreading
of facilitation
if th e subject
neglect
is led to believe
or is given
spreading
in
‘inhibition’.
an automatic,
concepts
one step further, hemispheres.
such
from
however:
the
presented,
contexts
network
component”,“.
is presumed
whereas
orient
orienting
both
the semantic
I ,, ,:
left space occurs
was not
by related
from
re-
in the amount
to related
side of space only.
ponent
stimulus
decrease
preceded
to result
normally
compensate
words within
is related
LH cannot
The
If the target
it was presented,
if the target
is theorized
to spread
RH
than
context.
target
respond.
in which
of activation
priming
sides of space, right
faster
controlled
:5 &ji8f;7*
musr
to the context
to process
:_ passive
the subject
activated
if the subject
the degree
results cost,
procers~ng
partially
Also,
be presented
‘; d ec~ons ” or judgments about the context. In a semantic prim‘&b ing task, the subject is first presented with a semantic context r 5 (such as a word, a sentence or a picture) that is followed by a tar-
facilitation
been
Visual
No.
3.
task, required
June
1997
McGlinchey-Berroth
-
Visual
processing
in
neglect
LIi,.
Box 2. Picture The
semantic
picture
priming,
primes
prime
and
displays
lexical
were
composed figure fields.
displays,
with
together
probability
located
that
task
used
target
of one
the
short prime
Fixation
and
strings.
hne drawing
The
picture
would
neglected
Priming
for performance. group,
Under
performed
Although noted
discrimination
these conditions,
choice
discrimination severity
sponse
were of three
cross-field
similar
and dissimilar. patients
Trials
types:
Verfaellie better
matching
considered
was present
performance and
slowed
in comparison
et al. concluded crimination
Also, the fact that all patients that were
physically
in
Cognitive
that
some
-
re-
field
Vol.
whose
infor-
tency
matching
were
No.
gets preceded
of neglect.
related
stimuli
formation
that
June
in
1997
meaning
the
dissociation
influenced
responded in the two
(and
latencies
for
re-
lexical
detask
Moreover,
primes
(and did so in a in
cases reported
in
faster for tarcompared
to un-
access to semantic
based on information field
the la-
In particular,
were significantly
primes, visual
infor-
discrimination
participants).
picture
neglected
available
priming,
significantly
our patients
was as efficient
that
for meaning,
2. As can be seen in Fig. 2, the
by related
picture
is not
semantic
forced-choice
primes
cases
for identi-
in a series of
the possibility
itself
occurs
to implicitly
field may be processed
to control
Ref. 33), decision
and dis-
3,
which
similar
each of the four
Verfaellie
suggested
with
manner
suggests
it is not sufftcient
addressed
in Box
picture
studies processing
is sufficient
this
task and a yoked is described
lateralized
discrimi-
although
We used an implicit
cision the
that
investigated
the
matching
information
hemispace
that
though
that
cross-field
behavior,
port’“,“5.
semantically
judgments
1,
and semantic
stimuli.
of visual
in the neglected
even
on the cross-field however,
level
We
mation
physically
were slower at matching
Sciences
RVF, right
paradigm from
experimentP”
with
that, as a group,
similar
left-sided
in the neglected influence
on the severity
or semantically
who
fication.
judgements.
depends
- limited
and forced-
In addition,
cross-field
field;
have access to visual
priming
evidence
on the discrimination
‘different’
patients regarding
task. Conse-
similar,
chance
neglect mation Semantic
individually,
to unrelated
that whether
are dissociable
visual
were aligned
Unlimited
Ref. 34.) LVF, left visual
The
a ‘different’
for patients
similar
(From
er al.”
of patients
et al. found
than
only
physically
strings were
Unlimited
ms IS1
400
authors
and one patient
group
was at chance.
related
letter that
that extin-
et al. study
requiring
at chance
task and significantly dissociation
as a
The
Verfaellie
semantically
performed
task. When
the patients,
matching
in a larger
of neglect.
neglect
course.
on the discrimination
compared
varying
time
well.
persuasive,
to the stimuli
at chance
target
judgidentical
Target
perceived.
set, pm-exposure they
and
to suggest
is unconsciously
the results were
did perform
Trends
equally
in the Farah
quently,
nation
trial
several limitations
stimulus
the
alternatives
ms IS1
400
ms
200
the two tasks
information
that
The
displays
RVF
ms
that there was no evidence
concluded
guished
occur.
until a wordlnonword task was virtually
forced-choice
Stimuli
point
and
prime
trial:
500
priming
except
not
of the
Target
ms
200
LVF
Fig. Picture
task,
by the
would
offset
RVF
ms
Fixation
the
stimuli
LVF
Discrimination
movements
followed
and remained visible made. The discrimination
priming
replaced vertically.
eye
strings
trial:
point
500
compensatory
letter
to the
maximized be
that
by 200ms ment was
for 200 ms simultaneous
duration,
methodology
target
of an object
display
Semantic priming
lateralized
letter
presented simultaneously We felt that the double the
:
and discrimination
decision
centrally
and one nonsense to opposing visual the
priming
mi,,
as it was
for
in-
presented information
McGlincheymBerroth
presented
in the intact
activation
observed
ment
field.
as patients
(Fig.
the
neglected
3). Notably,
not observed
at chance in
task for items
in
with
due to a small right in the medial priming
carried
the extrastriatal also
information.
prime-target
pairs were either
highly
stimuli
belonged
to the same
and were
physically
identical),
congruent
(both
same category different suggesting
the
implicit
processing
in neglect
representations relatively
systemjs.
of neglected
enough
to
and
that themselves activation.
form
and
was provided
5 (hemianopic)
Controls
from
as
lexical
Related
in
the
the visual
rep-
Fig. 2 Mean patient and on lexical
decisions.
orthographic portion
of
on an individual
of neglect lexical
patients
to process
information
dyslexia”.
More
et al.“,
who
direct
reported
semantic of a single words
Ladavas
et al.
semantic
priming
study,
Related
basis.
RVF
Unrelated
Prime
In all cases of neglect
(From
that
processed
This
was accomplished
ing and discrimination
contained word
(and
in the control
data)
there
neglect
field;
RVF, right
patients,
compared
with
is an effect
showed significant priming the individual data better.
Ref. 34.) LVF, left visual
visual
of prime
only from Statistical
a hemianopic
unrelated
prime
that
word
is equivalent
right visual significance
field primes. was assessed
field.
primes
rather
conditions. word
depicted than
picture
In the semantic primes
within
75
50
were
LVF
RVF
the
specified
semantic
Neglect patients
prim-
in Box 2, except primes. priming
semantically
61
25
representations*“.
the identical
paradigms
8 Bg 6 c
examined
or to fully
orthographic using
we
F t a
was due to explicitly
information
implicitly
the critical
-
940
by
evidence
the priming
of the prime
two critical
960
ortho-
is implied
in the study
and
we used word
980
Unrelated
in the two visual fields. The hemianopic patient Note: the scales are different in order to represent
is specific
information
the
rightmost
1000
decision latency for the picture priming task for individual the control group. This figure displays the effect of the related
not read aloud
orthographic
perceived
6 2 5 ‘Z
1020
Prime
the effect.
Expanding
1040
‘G 6
pictures
formation
in neglect
could
3 52
(n=lO)
representations
by Ladavas
who
Unrelated
Prime
the basis of semantic
perhaps
effect
Related
Prime
used
raises
the lexical
The ability
the length
dition,
Unrelated
1600
dis-
This
stimuli
support
orthographic
were
Related
transformation
as to whether
resentation
whether
RVF
1400
Patient
objects
representations
memory
the question
produced
w
900,1
to a
studies
because
little
activating
semantic
priming
%
1800
intact
of common
pictorial
patient
LVF
have typi-
these earlier
require
graphic
-o1075
priming
preceding
demonstrating
In part,
P
appearing
studies
cally used pictures
‘1
2000
from
is processed
from
2400
2200
1250
conditions,
cussion,
before
*p ;% r” T$
level.
As is clear
stimuli.
Patient 4
1425
dissimi-
information field
Unrelated
Prime
1600
E r”
to the
Significant
in the neglected
con-
were
congruent
that
study,
belonged (stimuli
in both
categorical
In that
but were physically
categories).
was found
visual processing
stimuli
lar) or noncongruent
3 .s ,x 26
a prim-
used
of neglected (both
Related
Patient 3
to examine
category
Unrelated
Prime
(i.e., b1indsight)3”.
and Rizzo1ati5’
LVF RVF
infor-
ing paradigm
gruent
Related
in our neglect
mation Berti
LVF RVF
of the
by visual
system
60004
therefore,
was supported
visual
;
occipital
patients
through
8000,
was
portion
It is unlikely,
that spared semantic
neglect
Patient 2
a dense left
hemorrhage
fissure.
in
initially
priming
hemianopsia calcarine
z
hemispace
semantic
in a patient
processing
Patient 1
experi-
for identification,
performed
the discrimination presented
Visual
The semantic
in the priming
was not sufficient
however,
-
There con-
Hemianopic
patients
Controls
Fig. 3 Mean percenteg@ of correct discriminations task. The performance of neglect and hemianopic
patients
Performance
initially
was no better
but was significantly field. LVF, left visual
than
chance
for targets
better than chance for targets field; RVF, right visual field.
for
initially
the presented
presented
related
Trends
in
Cognitive
Sciences
-
Vol.
1,
No.
3.
June
picture
was dependent
1997
discrimination on visual
in the left visual in the
right
field. field visual
McGllnchey-Berroth
-
(PAW-DOG)
Visual
or unrelated
graphically
mediated
word
the semantic
from
cally similar
to a semantically
We reasoned
that if the word
prime
results from part
equally
in
mediated
conditions
because
completions
would
On the other the prime
hand,
word
the semantic the
related
(SAW-DOG).
information
of the
should the
patients
with
assumes
likely
prime
do implicitly
priming
should
negligible
mediated
condition,
unexpected
negative
priming
significant
primes
and normal
(RVF)
primes.
processing
-20 .3 .$ -2
:I:
that all
conditions,
the
words.
patients
if any,
in
data
are
Flanker
visual
field with within
account
and Barnhardt”‘.
discrimination
In both
performance
in the LVF
of
and above
on
based
neglect
chance in the
paradigm
Regardless
of the specificity detect
1500 -
in the
activation
and
Note
a primary
paradigm
paradigm,
a central
the right,
by another
facilitate
Unreiated
stimulus.
with
by
The
responses
patients
stimuli.
usually
In this
to the left or stimulus
can
the same response
to the central
stimulus
or it can
a response
the one required
to
have used the
flanking
activating
and
is the fact
of neglect
by activating
to respond
responses
competes
the ability is flanked,
responses
code required
overt
codes to contralesional stimulus
response semantic
hand,
investigators
to examine
response
lies
on the one hand, require
Several
to
stimuli
between
on the other
tasks do not
to activate
inhibit
matching,
stimuli.
are defined
step required
of appropriate
difference
discrimination,
former
objects final
to contralesional
selection
and cross-field
the
either 0
or respond
that
which
a critical
codes.
flanker
A
with
hemispace,
contralesional
R&d
LVF
RVF.
context
8
an
for
in
forced-choice
1000 -
effect
was interpreted
Carr
that
5 $3
and
of Dagenbach,
priming 3000 -
account
was at chance
fields.
we found
for right
the findings
3500 2 s> 2 2 m
priming
visual
of results is not consistent processing
adequately Semantic
semantic
This pattern
there was
in both
In the orthographically
in the neglected
A
condition,
effect
of an implicit
process
The
priming
the context
be found
priming,
condition.
semantic
a partial
be observed
orthographically
this account
mediated
a
with
be equally
greater
condition,
orthographically
word
and
to form
in Fig. 4. In the semantic
a significant
effect in patients
priming
if neglect
in total,
represented
was orthographi-
perceived
semantic
left-sided
that
priming
explicitly the
In the ortho-
was changed
word
of the prime,
both
neglect
the first letter of each prime
condition
unrelated
rightmost
in
to the target word.
condition,
semantically
neglect
processing
to respond
code
that
to the central
stimulus. Three
B
Orthographically
mediated
context
studies
activation
of
responding. patients
with
extinctiongz,“’ patients
normally. the activated
1000 1500 1
a
Q
0
500Releted
Fuentes
and Humphreys
evidence
of inhibition,
LVF
-+-
RVF
+
LVF
+
RVF
1 1
Neglect
Fig. 4 Mean decision periment. (A) There visual
fields
mediated
latency
ficient
We have recently possibility
Controls
for
the
word
priming
ex-
condition
visual
field
primes
visual
field.
(From
there and
is significant
significant
negative
semantic
Ref. 9.) LVF, left visual
priming
priming field;
for left
in the
RVF. right
right
in
Cognitive
Sciences
-
Vol.
1,
No.
3,
June
1997
relatively
directions of cognitive
a great
is processed
to levels suf-
begun
and response an analysis
that it may be due
tech-
indicating
information
semantic
research
deal of evidence
code information.
of neglect
based on the
at one or more
levels of process-
ing. For instance,
with
features
tations
of objects
specific
spatial
ability
Trends
were
grate pieces of information
may
field.
and Rafal did find
patients
to bind or inte-
if featural
visual
because it al. or
to an inability
integrate
IS significant semantic priming from both in the semantic condition. (B) In the orthographically
codes
signs of extinction. and future
visual
stimulus
the Audet
Cohen
their
the application
to activate
response
not be able to associate
either
studies. but
has uncovered
that neglected
patients
in
in
These data suggest
to activate
may
overt in three
in some conditions
neglect44.
code to a specific
remarks
To summarize, niques
and only with
found
and only showed
Concluding
Unrelated
+
response
from
effect has been found
patients
was not
task to examine
independent
may be able
However,
inhibition
mild
flanker
of two patients
that neglect
5 5
used the flanker codes
A reliable
the milder
8
have
response
patients into
coherent
(regardless
locations.
In addition,
and spatial
information to guide
may not be able to
objects
of their
not be sufficient to bind response
neglect
or bind
represen-
level of coherence) it is possible
were fully behavior
codes to a specified
specified
because spatial
to
that even they
of an inlocation.
McGllnchey-Berroth
That
is, patients
implicitly,
may
but
these processes portant
be able to activate
cannot
overrly
are, to some extent,
to note that deficits
feature-integration) other
not
impose
underlying
deficit(s)
features
provides
inro
l
ar anbur,
into this perplexing
l
those features
a novel way to examine neglect,
l
a patient
an object
localize
in hemispatial
vide new insighrs
deficits
the
and should
processing
in
Outstanding
it is im-
For example,
may be able to coarsely
in space. This approach
codes
at one level (such as
binding).
Visual
Alrhough
interdependent
do not necessarily
be able to integrate
nonetheless,
response
in kind.
in binding
(such as object-space
may
respond
-
pro-
disorder. l
neglect
questions
Which visual processes are impaired and which processes are preserved in hemispatial neglect? Is the fact that neglect can occur following damage to a number of different regions in the brain systematically related to the heterogeneity of the disorder? If impaired binding operations do, in fact, underlie hemispatial neglect, can we manipulate the extent to which this operation is necessary and thus reorient patients with neglect to ‘see’ information in the contralesional field? Would altering binding processes change the clinical manifestations of neglect? Is binding a unitary function or are there separate binding functions that are specific to certain levels of processing? Also, is binding a focally represented function in the brain or is it widely distributed?
Acknowledgements This work
is supported
and Stroke Older
Grant
Americans
William
Grande
work
presented
Mieke
Institute
of Neurological
and by Grant AGO8812
Independence
Milberg,
Laura
by the National
NS29342
Center.
Verfaellie,
and Patrick
The author
Michael
Kilduff
thanks
Alexander.
for all of their
Disease
to the Claud
D. Pepper
her colleagues
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26, 439-454 B. (1994)
Genes, environment,
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S.A. and Shankweiler,
A
D.P., eds).
33 Bryne, what
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we know
Foundations
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119, 143-157
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of Literacy
dyslexia Brain
to reading in Cognitive
(Blachman,
acquisition: and Linguistic
B., ed.),
Erlbaum
(in
press)
M. and Hulme,
phonological 23 Brown,
Psycho/:
29 Bruck,
31 Pennington.
Erlbaum
R.K.
G.C.,
Knowledge
C. (1994)
The development
34 Hatcher,
of phonological
reading
skills Trans. R. Sot. B 346, 21-28 22 Wagner,
Orden,
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syndrome?
phonological
Tribute
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C. (1992)
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and
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Very
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21 Snowling,
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271, 746-747
Dev. 61. 1728-1743
stage for phoneme pp. 97-117,
in auditory Nature
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H.S. (1990)
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Difficulties
backwardness
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The nonword
27, 29-53
in qua+irregular
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20 Fowler,
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27 Stothard,
28 Van Snowlmg,
D.M..
Reading
dyslexia
M.
Whurr C. and
15 Willows, 16 Brady,
Snowling,
Understanding
C. et a/. (1995)
in children:
56-115
(1996)
R.K. (1992)
Read. Res. Quart.
reading
15
Cognit
reading:
Psycho/.
and
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principles
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domains
Connectionism
a review
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0.
Computational 26 Hulme,
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-
in dyslexia:
25 Plaut, 56-l
Whurr
dyslexia
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Intervention,
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and
T . (1991)
of acquired
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orthographic
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M., eds) pp. 131-152.
11 Hinton, 12 Plaut,
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Learning
et
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The
abilities
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development
of
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85, l-20
phonology,
reading
young and
P.J., Hulme,
C. and
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integrating
phonological
readers’
by
Ellis,
A.W. the
skills: The phonological
(1994)
Ameliorating
teaching
linkage
of
early
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hypothesis
Child
and Dev. 65,
41 57 regularity
in
35 Snowling, teaching
and Lang. (in press)
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Annotation: J. Child
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approaches
Psychiatry
to the
37, 139-148
Visual information processing in hemispatial neglect Regina
McGlinchey-Berroth
he&space.
Despite
a great deal of visual of patients
T
he disorder
of unilateral
the most striking an acquired
disorder
acknowledge,
report
formation
falling
the responsible
hemispatial
of all neuropsychological marked
in the visual
lesion.
make hemispace
This disorder
information
in certain
neglect
tasks.
inability
explicit
It is to
use of in-
contralateral
to
can be just as severe and
Copyright
0 1997, Elsevier
Science Trends
awareness,
processing The current
debilitating
is perhaps
syndromes.
by an individual’s
or otherwise
this lack of phenomenal
noted:
does occur and can review
will preseW
as disorders
‘the patient
universe
oflanguage
may behave
had abruptly to a number
intention
or peripersonaVpersona1).
Cognitive
reserved.
or memory. almost
disorder
according
in
t&k
As Mesulam’
as if one half of the
ceased to exist in any meaningful
It is a very heterogeneous
Ltd. All rights
recent
ofdifferent
schemes (such as attention/ It can be demonstrated
1364.6613/97/$17.00 Sciences
-
form’.
and patients can be classi&d
Vol
PII: 5136&6613(97)01016-4 1,
No.
3,
June
1997
McGlinchey-Berroth
- Visual
in the somesthetic,
auditory
the fact that the primary systems are often intact. as a deficit rather
than a deficit
following observed 2,3).
Thus,
hemisphere
Similarly,
of neglect
attend
bias to ignore instance, ductor
Critchley”
Unlike
many
extremely
the case of an orchestra
con-
visual
on one side of the
with
hemispatial
(such
ration
of the disorder
companying following
damage
and subcortical’,‘, permanent
‘A’)
arrayed
For example,
to a number
weeks to months
range
Jackson
attributed
speech.
He felt that visual
parietal
lobe and when
this patient’s
objects
imperception
ideation
damaged
to a loss of cortical
sensibilities’z,‘3.
neglect
arose from
in either
devastating
three-dimensional
for recove$.
areas effectively is
body
and du-
image.
spatial when
may be observed
‘amnesia’
both
cortical with
body wiped BrainI
the LH,
argued and
were
from
visual
cognitive
of hemispatial theorists
B
psychology
disorientation
that
and
Brain
than
who
Berti’”
derived
to understand
For example,
Bisiach
a representational
ac-
based on the finding only
account
a neural
and
represen-
centers which responsible
space awareness.
space using viewer-centered Damage
D
to these brain
to a deficit
ing.
Riddoch
impaired Examples of the performance of patients on clinical tests of hemirpatial neglect. (A) Symbol and (B) letter search performance reflects the inability to respond to targets to the left of midline. (C) Line shows the typical rightward bias of patients’transections, suggesting that they perceive the left end of as being shifted rightward. (D) A patient’s copy of a person showing the lack of detail for features to the the patient’s midline.
Cognitive
Sciences
- Vol.
lead to
stimuli; that
improved neglected
1, No.
3,
June
1997
and
orienting
finding
occurs
this theory
side
of
the
and colleagues”
have
because
of
to contra-
is based on the
bisection patients
ne-
process-
HumphreyslY of attention
line
when
attribute
in attentional
that neglect
lesional
Heilman
in
areas will
of theories
glect
suggested
Trends
code
coordinates.
neglect. A number
Fig. 1 search bisection the line left of
for
Furthermore,
they suggest that these brain centers
C
a the
that asserts that space is
in several brain and are jointly
conscious
from
side of space. Rizzolatti
represented interact
image
information
have advanced
tational
that pa-
are asked to visually
ipsilesional
L
in the
concepts
neglect.
postulated
scene report
B
an
felt that the
and neuroscience
tients 2
F ’ (3
suggested
neglect.
count’6,‘7
D
lobes mediated
and
role in these functions
hemispatial
n
of these
side of a person’s
use contemporary
has
A
of our
to either
resulted.
important
lobe
a representation
schema,
damaged,
believed
parietal
and was thus the first to note an asymmetry
Modern
One
Pick’*
that the parietal
body
to name attributed
the right
Damage
for half of the body
lateralization
several
image.
in
in the right
writers
out the contralateral
RH may play a more
any
(such as hemianopia from
they
early
he felt contained
perception
or absence of ac-
in duration
which
of
to a defect
led to an inability
Other
damage
feature
was located
neglect
neglect
and places.
to have left
clinical
(see
and can, in some cases, be permanent.
A
a RH
of the left half of space.
that
of structures,
or sensory dysfunction and it may
outstanding
suggesting
the severity
neglect
most
was her ‘imperception’
of the line
disorders,
to both
The
be diagnosed
persons,
it may or may not be associated
motor
or hemiplegia)
to de-
would
line
prognosis
as well as the presence
disorders.
the first person
was probably
today
oriented
can be a functionally
regard
on left to be
neglect”.
this patient
neglect
as the letter
of a horizontally
neuropsychological
of
focus
following
Jackson
portion
with
likewise
are intended
who
midpoint,
other
variable
will
developed
scribe a patient
a very unfavorable
and for
underpinnings
information
For
the left-most neglect
carrying
review
of investi-
accounts
or thalamus,
Hemispatial
focus
of neglect
multimodal.
Fig. 1). disorder,
they
for visual
Theoretical
of the actual
are neglecting
that
the constructs
John Hughlings
on rhe left side of a page of randomly
to be to the right they
neglect
although
and
the middle
the primary mechanisms
This
The
stimuli
completely
of the neuroanatomical
or sentences
tests, patients
and judge
lesion,
unand
the non-neglected
of words
all of the musicians target
has been
in humans.
hemispatial
may only
side of the body4.
only
neglect
on only one side of space’.
reported
clinical
that appear
in the every-
a patient
or even deny
into the underlying
neglect
are often
of the environment
(anosognosia)“‘.
the delineation
Refs
one side of space can be very pronounced.
fail to cross-out
letters
can be found
parts
gations
is that patients
representation
minimize
Visual
and severely (LH;
recovery
have any deficits
or moving.
damage
complicating
consequently
but it has been
the non-neglected
and events
who ignored
stage! On will
damage
he or she may eat from to people
feeling
For example,
read only
factor
aware of their limited
and searching,
with left hemisphere
shave, dress and groom
despite
and projection
touching
(RH)
of the patient.
side of a plate,
modalities,
occurs most commonly
Demonstration
day activities
neglect
neglect has been characterized
in seeing, hearing,
in patients
in
receiving
listening,
neglect
right
and visual sensory
in looking,
Hemispatial
processing
performance
were cued to the line.
Similarly,
suggested
that
McGlinchey-Berroth
:I
Th’ IS IS a cognitive
‘~j mantic :
paradigm
memory
that
assesses
by determining
has on behavior
without
what
requiting
the contents
effect
of se-
semantic
the subject
to make
-
the target
has already
context
activation
of the prime.
explicit
a related
target
process
the prime,
will
without
i
get stimulus
related
to the prime
;
stimulus
cation
in
:
sponses
are typically
related
to the priming
/, ,_
to which
is related
of time (‘facilitation’)
spread
,:
as a more
,.i
of the
4
activation
!
target
‘f*-:a’;:a:
the
strategic stimulus
to the prime,
response
times
controls
Given
processor
hemispatial
neglect.
neglect
orienting
to the ipsilesional this deficit,
posed
that
stimuli
presented for
there
cently.
:
in some way,
left
the lateral
with
simultaneous
hemi-
patients when
two stimuli
a are
(which
of a single stimuli)
pro-
sented
from
better
have
several
paradigms
processing
use an
patients
are
frame-
in each visual field.
the actual
fate of
until
visual patients
space,
using
three
of processing the neglected
errors.
‘mailman’
RH For
achieved hemispace
infor-
was spurred
often
example,
as ‘milkman’. cross-field
retain patients
may
residual
visual
semantic
a comparison Berti
Trends
in
task equated
Cognitive
later
in the left replicated
in
et al.
They even
concluded
matching
and two differ-
found
Farah
level.
may simply
This
naming. three
a forced-choice
Vol.
who To
patients
the
stimuli argued
ex-
on a cross-field
information
1,
examine with
discrimination
of visual
-
that
with
interpretation,
et aP’
performance
the amount
Sciences
objects
be an easier task and
than
et al. tested their
that patients’
in the condition
by Farah
analysis
task by identical,
that unattended
to a categorical
and
physically
viewpoint
chance
represen-
matching
of the two different
and compared
matching
stimuli:
was later challenged
this possibility,
which
whether
even though
the level of visual
a different
less perceptual
tinction
performed
presented
were
with
one pre-
patients
the cross-field
the same name.
was above
processed
require
and ex-
simultaneously,
the picture
of ‘same’
but from with
that cross-field
word
Since that time, matching,
were
however,
and WarringtonZ5
lesions
have been used to explore
in neglect including
for
neglect
were presented
the same or different,
to perform types
same object
in hemispatial
less severe
the presentation
between
Surprisingly,
et a1.30 manipulated
required
required
some clinicians
with
findings
side
to the ipsi-
clear signs of severe visual neglect’“,2”.
tation
and can influence
in which
they were asked to indicate
These
with
to double
of diagnosing
Patients
to name
(LVF).
with
Berti
re-
were
unable
field
may
patients
contralesional
they were in
method
of two pictures
than chance when pictures
patients
side of space. Although
controversial.
displays
four
‘Extinction
the relationship
remains
the two
impairments
processing
of Kinsbourne
the word
studies
simultaneously
may not be apparent
a valuable
to some degree
are presented
neglect
hemispace,
the
with
misread
limited-
on the contralesional
as a useful
to disengage
about
on by the observations reading
lexical
and
refers to a phenomenon
the stimulus
take extinction
this view
that even though in
information
in their
from
in the neglected
tested lesion.
lateral and contralateral
side of space.
who length
theory
i=
stimuli
RH damage,
and his colleagueP
attentional
of RH
stimulation’
ent objects
that patients
retrieval
in which
than the left-
neglect
noted
as
paradigm
fail to report
latetalized
in the neglected
within
activation
tasks. Most
and Gazzaniga”
as a result
exacer-
inability
matching
extinction
Perhaps
of information
falling
I), and flanker
Le Doux
side of space”-“.
was known
is processed
Cross-field
same name.
mation
if no
known
activation
_
to identify,
tinction
have shown
in the level(s)
than
Gen. 106. 226-254
;
of awareness’”
performance
Interest
(il,
criterion
strong
the
visual
J. Exp. Psycho/.
,(. ~.,,
and
spreading
(see Box
Volpe,
implicitly.
Implicit
priming
priming
overly
have provided
information
lo-
is actually
be longer
A spreading
objective
demonstrate
these theories
be unaware
to be
Rev. 82. 407428
Semantic
attention
,‘:::>
hemispace.
and produces
Consistent
Posner
falling
behavior
‘potent’
is unopposed
in the ipsilateral
Studies
L.
the
orienting
Following
characterizing
information
control
and
to the left and right
is more
patients
little
target
will
is not
to a specific
a phenomenon
E.F. (1975) Psycho/.
roles of inhibitionless
asked
are op-
that the rightward
is a selective
relatively
there
in the right
in the RH).
orienting
that
processors
in the LH)
that
neglect,
residing
He argues
findings
and Loftus. processing
J.H. (1977)
for
this line of argument
suggests
and action
(located
because
Neely, capacity
(i
to the
neglect
lesions
A.M.
memory:
both
to
orienting
time
to
to that space and, thus, cannot
These opponent
bating
b
if the
because
orienting
this lateralization,
systems
(located
While
are faster
controls
right-sided
attention
of attention
the LH’s
work
LH
following
attentional
marked
attentional the
Kinsbourne
processor
cause thus
attention
generated,
This
the target
an unrelated
response
that
time rhan when
alone”.
expects
directing
had been
of semantic
* “g --i (i ii ‘, ;
space, respectively. ward
a Collins,
presentation
in memory;
is grearer
activation
but
the subject’s
expectancy
sufftcient
References
as well
to automatically
for the RH loss. Taking
processor
The
(thus
memory)
by the spreading
of facilitation
if th e subject
neglect
is led to believe
or is given
spreading
in
‘inhibition’.
an automatic,
concepts
one step further, hemispheres.
such
from
however:
the
presented,
contexts
network
component”,“.
is presumed
whereas
orient
orienting
both
the semantic
I ,, ,:
left space occurs
was not
by related
from
re-
in the amount
to related
side of space only.
ponent
stimulus
decrease
preceded
to result
normally
compensate
words within
is related
LH cannot
The
If the target
it was presented,
if the target
is theorized
to spread
RH
than
context.
target
respond.
in which
of activation
priming
sides of space, right
faster
controlled
:5 &ji8f;7*
musr
to the context
to process
:_ passive
the subject
activated
if the subject
the degree
results cost,
procers~ng
partially
Also,
be presented
‘; d ec~ons ” or judgments about the context. In a semantic prim‘&b ing task, the subject is first presented with a semantic context r 5 (such as a word, a sentence or a picture) that is followed by a tar-
facilitation
been
Visual
No.
3.
task, required
June
1997
McGlinchey-Berroth
-
Visual
processing
in
neglect
LIi,.
Box 2. Picture The
semantic
picture
priming,
primes
prime
and
displays
lexical
were
composed figure fields.
displays,
with
together
probability
located
that
task
used
target
of one
the
short prime
Fixation
and
strings.
hne drawing
The
picture
would
neglected
Priming
for performance. group,
Under
performed
Although noted
discrimination
these conditions,
choice
discrimination severity
sponse
were of three
cross-field
similar
and dissimilar. patients
Trials
types:
Verfaellie better
matching
considered
was present
performance and
slowed
in comparison
et al. concluded crimination
Also, the fact that all patients that were
physically
in
Cognitive
that
some
-
re-
field
Vol.
whose
infor-
tency
matching
were
No.
gets preceded
of neglect.
related
stimuli
formation
that
June
in
1997
meaning
the
dissociation
influenced
responded in the two
(and
latencies
for
re-
lexical
detask
Moreover,
primes
(and did so in a in
cases reported
in
faster for tarcompared
to un-
access to semantic
based on information field
the la-
In particular,
were significantly
primes, visual
infor-
discrimination
participants).
picture
neglected
available
priming,
significantly
our patients
was as efficient
that
for meaning,
2. As can be seen in Fig. 2, the
by related
picture
is not
semantic
forced-choice
primes
cases
for identi-
in a series of
the possibility
itself
occurs
to implicitly
field may be processed
to control
Ref. 33), decision
and dis-
3,
which
similar
each of the four
Verfaellie
suggested
with
manner
suggests
it is not sufftcient
addressed
in Box
picture
studies processing
is sufficient
this
task and a yoked is described
lateralized
discrimi-
although
We used an implicit
cision the
that
investigated
the
matching
information
hemispace
that
though
that
cross-field
behavior,
port’“,“5.
semantically
judgments
1,
and semantic
stimuli.
of visual
in the neglected
even
on the cross-field however,
level
We
mation
physically
were slower at matching
Sciences
RVF, right
paradigm from
experimentP”
with
that, as a group,
similar
left-sided
in the neglected influence
on the severity
or semantically
who
fication.
judgements.
depends
- limited
and forced-
In addition,
cross-field
field;
have access to visual
priming
evidence
on the discrimination
‘different’
patients regarding
task. Conse-
similar,
chance
neglect mation Semantic
individually,
to unrelated
that whether
are dissociable
visual
were aligned
Unlimited
Ref. 34.) LVF, left visual
The
a ‘different’
for patients
similar
(From
er al.”
of patients
et al. found
than
only
physically
strings were
Unlimited
ms IS1
400
authors
and one patient
group
was at chance.
related
letter that
that extin-
et al. study
requiring
at chance
task and significantly dissociation
as a
The
Verfaellie
semantically
performed
task. When
the patients,
matching
in a larger
of neglect.
neglect
course.
on the discrimination
compared
varying
time
well.
persuasive,
to the stimuli
at chance
target
judgidentical
Target
perceived.
set, pm-exposure they
and
to suggest
is unconsciously
the results were
did perform
Trends
equally
in the Farah
quently,
nation
trial
several limitations
stimulus
the
alternatives
ms IS1
400
ms
200
the two tasks
information
that
The
displays
RVF
ms
that there was no evidence
concluded
guished
occur.
until a wordlnonword task was virtually
forced-choice
Stimuli
point
and
prime
trial:
500
priming
except
not
of the
Target
ms
200
LVF
Fig. Picture
task,
by the
would
offset
RVF
ms
Fixation
the
stimuli
LVF
Discrimination
movements
followed
and remained visible made. The discrimination
priming
replaced vertically.
eye
strings
trial:
point
500
compensatory
letter
to the
maximized be
that
by 200ms ment was
for 200 ms simultaneous
duration,
methodology
target
of an object
display
Semantic priming
lateralized
letter
presented simultaneously We felt that the double the
:
and discrimination
decision
centrally
and one nonsense to opposing visual the
priming
mi,,
as it was
for
in-
presented information
McGlincheymBerroth
presented
in the intact
activation
observed
ment
field.
as patients
(Fig.
the
neglected
3). Notably,
not observed
at chance in
task for items
in
with
due to a small right in the medial priming
carried
the extrastriatal also
information.
prime-target
pairs were either
highly
stimuli
belonged
to the same
and were
physically
identical),
congruent
(both
same category different suggesting
the
implicit
processing
in neglect
representations relatively
systemjs.
of neglected
enough
to
and
that themselves activation.
form
and
was provided
5 (hemianopic)
Controls
from
as
lexical
Related
in
the
the visual
rep-
Fig. 2 Mean patient and on lexical
decisions.
orthographic portion
of
on an individual
of neglect lexical
patients
to process
information
dyslexia”.
More
et al.“,
who
direct
reported
semantic of a single words
Ladavas
et al.
semantic
priming
study,
Related
basis.
RVF
Unrelated
Prime
In all cases of neglect
(From
that
processed
This
was accomplished
ing and discrimination
contained word
(and
in the control
data)
there
neglect
field;
RVF, right
patients,
compared
with
is an effect
showed significant priming the individual data better.
Ref. 34.) LVF, left visual
visual
of prime
only from Statistical
a hemianopic
unrelated
prime
that
word
is equivalent
right visual significance
field primes. was assessed
field.
primes
rather
conditions. word
depicted than
picture
In the semantic primes
within
75
50
were
LVF
RVF
the
specified
semantic
Neglect patients
prim-
in Box 2, except primes. priming
semantically
61
25
representations*“.
the identical
paradigms
8 Bg 6 c
examined
or to fully
orthographic using
we
F t a
was due to explicitly
information
implicitly
the critical
-
940
by
evidence
the priming
of the prime
two critical
960
ortho-
is implied
in the study
and
we used word
980
Unrelated
in the two visual fields. The hemianopic patient Note: the scales are different in order to represent
is specific
information
the
rightmost
1000
decision latency for the picture priming task for individual the control group. This figure displays the effect of the related
not read aloud
orthographic
perceived
6 2 5 ‘Z
1020
Prime
the effect.
Expanding
1040
‘G 6
pictures
formation
in neglect
could
3 52
(n=lO)
representations
by Ladavas
who
Unrelated
Prime
the basis of semantic
perhaps
effect
Related
Prime
used
raises
the lexical
The ability
the length
dition,
Unrelated
1600
dis-
This
stimuli
support
orthographic
were
Related
transformation
as to whether
resentation
whether
RVF
1400
Patient
objects
representations
memory
the question
produced
w
900,1
to a
studies
because
little
activating
semantic
priming
%
1800
intact
of common
pictorial
patient
LVF
have typi-
these earlier
require
graphic
-o1075
priming
preceding
demonstrating
In part,
P
appearing
studies
cally used pictures
‘1
2000
from
is processed
from
2400
2200
1250
conditions,
cussion,
before
*p ;% r” T$
level.
As is clear
stimuli.
Patient 4
1425
dissimi-
information field
Unrelated
Prime
1600
E r”
to the
Significant
in the neglected
con-
were
congruent
that
study,
belonged (stimuli
in both
categorical
In that
but were physically
categories).
was found
visual processing
stimuli
lar) or noncongruent
3 .s ,x 26
a prim-
used
of neglected (both
Related
Patient 3
to examine
category
Unrelated
Prime
(i.e., b1indsight)3”.
and Rizzo1ati5’
LVF RVF
infor-
ing paradigm
gruent
Related
in our neglect
mation Berti
LVF RVF
of the
by visual
system
60004
therefore,
was supported
visual
;
occipital
patients
through
8000,
was
portion
It is unlikely,
that spared semantic
neglect
Patient 2
a dense left
hemorrhage
fissure.
in
initially
priming
hemianopsia calcarine
z
hemispace
semantic
in a patient
processing
Patient 1
experi-
for identification,
performed
the discrimination presented
Visual
The semantic
in the priming
was not sufficient
however,
-
There con-
Hemianopic
patients
Controls
Fig. 3 Mean percenteg@ of correct discriminations task. The performance of neglect and hemianopic
patients
Performance
initially
was no better
but was significantly field. LVF, left visual
than
chance
for targets
better than chance for targets field; RVF, right visual field.
for
initially
the presented
presented
related
Trends
in
Cognitive
Sciences
-
Vol.
1,
No.
3.
June
picture
was dependent
1997
discrimination on visual
in the left visual in the
right
field. field visual
McGllnchey-Berroth
-
(PAW-DOG)
Visual
or unrelated
graphically
mediated
word
the semantic
from
cally similar
to a semantically
We reasoned
that if the word
prime
results from part
equally
in
mediated
conditions
because
completions
would
On the other the prime
hand,
word
the semantic the
related
(SAW-DOG).
information
of the
should the
patients
with
assumes
likely
prime
do implicitly
priming
should
negligible
mediated
condition,
unexpected
negative
priming
significant
primes
and normal
(RVF)
primes.
processing
-20 .3 .$ -2
:I:
that all
conditions,
the
words.
patients
if any,
in
data
are
Flanker
visual
field with within
account
and Barnhardt”‘.
discrimination
In both
performance
in the LVF
of
and above
on
based
neglect
chance in the
paradigm
Regardless
of the specificity detect
1500 -
in the
activation
and
Note
a primary
paradigm
paradigm,
a central
the right,
by another
facilitate
Unreiated
stimulus.
with
by
The
responses
patients
stimuli.
usually
In this
to the left or stimulus
can
the same response
to the central
stimulus
or it can
a response
the one required
to
have used the
flanking
activating
and
is the fact
of neglect
by activating
to respond
responses
competes
the ability is flanked,
responses
code required
overt
codes to contralesional stimulus
response semantic
hand,
investigators
to examine
response
lies
on the one hand, require
Several
to
stimuli
between
on the other
tasks do not
to activate
inhibit
matching,
stimuli.
are defined
step required
of appropriate
difference
discrimination,
former
objects final
to contralesional
selection
and cross-field
the
either 0
or respond
that
which
a critical
codes.
flanker
A
with
hemispace,
contralesional
R&d
LVF
RVF.
context
8
an
for
in
forced-choice
1000 -
effect
was interpreted
Carr
that
5 $3
and
of Dagenbach,
priming 3000 -
account
was at chance
fields.
we found
for right
the findings
3500 2 s> 2 2 m
priming
visual
of results is not consistent processing
adequately Semantic
semantic
This pattern
there was
in both
In the orthographically
in the neglected
A
condition,
effect
of an implicit
process
The
priming
the context
be found
priming,
condition.
semantic
a partial
be observed
orthographically
this account
mediated
a
with
be equally
greater
condition,
orthographically
word
and
to form
in Fig. 4. In the semantic
a significant
effect in patients
priming
if neglect
in total,
represented
was orthographi-
perceived
semantic
left-sided
that
priming
explicitly the
In the ortho-
was changed
word
of the prime,
both
neglect
the first letter of each prime
condition
unrelated
rightmost
in
to the target word.
condition,
semantically
neglect
processing
to respond
code
that
to the central
stimulus. Three
B
Orthographically
mediated
context
studies
activation
of
responding. patients
with
extinctiongz,“’ patients
normally. the activated
1000 1500 1
a
Q
0
500Releted
Fuentes
and Humphreys
evidence
of inhibition,
LVF
-+-
RVF
+
LVF
+
RVF
1 1
Neglect
Fig. 4 Mean decision periment. (A) There visual
fields
mediated
latency
ficient
We have recently possibility
Controls
for
the
word
priming
ex-
condition
visual
field
primes
visual
field.
(From
there and
is significant
significant
negative
semantic
Ref. 9.) LVF, left visual
priming
priming field;
for left
in the
RVF. right
right
in
Cognitive
Sciences
-
Vol.
1,
No.
3,
June
1997
relatively
directions of cognitive
a great
is processed
to levels suf-
begun
and response an analysis
that it may be due
tech-
indicating
information
semantic
research
deal of evidence
code information.
of neglect
based on the
at one or more
levels of process-
ing. For instance,
with
features
tations
of objects
specific
spatial
ability
Trends
were
grate pieces of information
may
field.
and Rafal did find
patients
to bind or inte-
if featural
visual
because it al. or
to an inability
integrate
IS significant semantic priming from both in the semantic condition. (B) In the orthographically
codes
signs of extinction. and future
visual
stimulus
the Audet
Cohen
their
the application
to activate
response
not be able to associate
either
studies. but
has uncovered
that neglected
patients
in
in
These data suggest
to activate
may
overt in three
in some conditions
neglect44.
code to a specific
remarks
To summarize, niques
and only with
found
and only showed
Concluding
Unrelated
+
response
from
effect has been found
patients
was not
task to examine
independent
may be able
However,
inhibition
mild
flanker
of two patients
that neglect
5 5
used the flanker codes
A reliable
the milder
8
have
response
patients into
coherent
(regardless
locations.
In addition,
and spatial
information to guide
may not be able to
objects
of their
not be sufficient to bind response
neglect
or bind
represen-
level of coherence) it is possible
were fully behavior
codes to a specified
specified
because spatial
to
that even they
of an inlocation.
McGllnchey-Berroth
That
is, patients
implicitly,
may
but
these processes portant
be able to activate
cannot
overrly
are, to some extent,
to note that deficits
feature-integration) other
not
impose
underlying
deficit(s)
features
provides
inro
l
ar anbur,
into this perplexing
l
those features
a novel way to examine neglect,
l
a patient
an object
localize
in hemispatial
vide new insighrs
deficits
the
and should
processing
in
Outstanding
it is im-
For example,
may be able to coarsely
in space. This approach
codes
at one level (such as
binding).
Visual
Alrhough
interdependent
do not necessarily
be able to integrate
nonetheless,
response
in kind.
in binding
(such as object-space
may
respond
-
pro-
disorder. l
neglect
questions
Which visual processes are impaired and which processes are preserved in hemispatial neglect? Is the fact that neglect can occur following damage to a number of different regions in the brain systematically related to the heterogeneity of the disorder? If impaired binding operations do, in fact, underlie hemispatial neglect, can we manipulate the extent to which this operation is necessary and thus reorient patients with neglect to ‘see’ information in the contralesional field? Would altering binding processes change the clinical manifestations of neglect? Is binding a unitary function or are there separate binding functions that are specific to certain levels of processing? Also, is binding a focally represented function in the brain or is it widely distributed?
Acknowledgements This work
is supported
and Stroke Older
Grant
Americans
William
Grande
work
presented
Mieke
Institute
of Neurological
and by Grant AGO8812
Independence
Milberg,
Laura
by the National
NS29342
Center.
Verfaellie,
and Patrick
The author
Michael
Kilduff
thanks
Alexander.
for all of their
Disease
to the Claud
D. Pepper
her colleagues
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