Visual and tactile size distortion in a patient with right neglect.
ABSTRACT One typical feature of the neglect syndrome in patients with right hemisphere damage is that they bisect horizontal lines to the right of centre. It has been argued that to a large extent these bisection errors can be attributed to a perceptual change whereby the patient experiences the left half of a line as shorter than the right half, causing them to set the midpoint of the line towards the right. We describe here a patient with a left hemisphere lesion and rightward neglect, who consequently makes bisection errors in a leftward direction. We carried out a series of tests which confirmed that he shows a subjective visual distortion in the converse direction, i.e. a perception of horizontal extents on the right as shorter than extents on the left. We also found that he shows a similar distortion in his tactile perception. The association of visual and tactile distortions in this patient is compatible with the view that the distortion effects have a rather high-level origin. Multiple single-case studies will, however, be required to establish whether this association of deficits is typical, or whether visual and tactile size distortions are separable symptoms associated with neglect.
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ABSTRACT: For more than 50 years, the right hemisphere is no longer considered the minor partner of the brain. Several syndromes that preferentially emerge after right hemisphere damage (such as unilateral spatial neglect, anosognosia, topographical disorientation and dysprosody) have shown its dominant role on the left hemisphere. Such contexts confirm that, in physiological conditions, the right hemisphere has a central role in those attention and polymodal sensorial integration processes that are necessary for self- and environment appraisal. The pathogenesis of the right hemisphere specific syndromes is an active domain of neurosciences research. The confabulatory phenomena that characterize the anosognosia, misidentification syndromes, or other neuropsychiatric conditions due to right brain damage, give further relevance to the role of right polymodal associative brain areas in the neural process that elaborates self and environment awareness. Another field of interest is the role of the right brain in emotional processes. Although lexical and linguistic abilities depend on the left hemisphere, the right hemisphere plays a central role in the affective aspects of communication such as prosody and comprehension of facial expressions, and in the understanding of abstractions and figurative aspects of language. The individual with extensive right brain damage almost always seems to adequately communicate in superficial conversations, without evident phonological impairment, but with a more detailed analysis he may appear less communicative, distracted or abrupt, verbose but less perspicacious and emotionally flat. Unlike aphasic syndromes due to left hemisphere damage, right brain communicative deficits may not be integrated in any cognitive or anatomo-functional model but they are the subject of very active neuropsychological and neurophysiological research.EMC - Neurologie 11/2005; 2(4):475-504.
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ABSTRACT: A patient with right sided brain damage suffered contralesional neglect, inferior quadrantanopia (with 0 degrees sparing in the left eye and 13 degrees sparing in the right), and a visual field restriction (to 15 degrees ) in the upper contralesional quadrant of the left eye. In binocular vision, the patient showed underestimation of the horizontal size of contralesional line segments unless cued to localise their end points. When asked to reproduce, in monocular vision, 10 degrees and 20 degrees distances between two attentionally cued end points lying on the frontal vertical plane, the patient showed relative contralesional overextension and ipselesional underextension along the directions falling within the blind sectors of the neglected space. No asymmetry was present along the directions falling within the seeing sectors of the same space. These findings suggest precise retinotopic modulation of space misrepresentation in unilateral neglect.Journal of Neurology Neurosurgery & Psychiatry 02/2003; 74(1):116-9. · 5.58 Impact Factor
- International Conference on Bioinformatics & Computational Biology, BIOCOMP 2009, July 13-16, 2009, Las Vegas Nevada, USA, 2 Volumes; 01/2009
Neurocase (2001) Vol. 7, pp. 391–396© Oxford University Press 2001
Visual and Tactile Size Distortion in a Patient with Right
Catrin L. Pritchard, H. Chris Dijkerman1, Robert D. McIntosh2and A. David Milner2
School of Psychology, University of St Andrews, St Andrews, UK
Present addresses:1Psychological Laboratory, University of Utrecht, Utrecht, The Netherlands and2Department of Psychology,
University of Durham, Durham, UK
One typical feature of the neglect syndrome in patients with right hemisphere damage is that they bisect horizontal
lines to the right of centre. It has been argued that to a large extent these bisection errors can be attributed to a
perceptual change whereby the patient experiences the left half of a line as shorter than the right half, causing them to
set the midpoint of the line towards the right. We describe here a patient with a left hemisphere lesion and rightward
neglect, who consequently makes bisection errors in a leftward direction. We carried out a series of tests which
confirmed that he shows a subjective visual distortion in the converse direction, i.e. a perception of horizontal extents
on the right as shorter than extents on the left. We also found that he shows a similar distortion in his tactile
perception. The association of visual and tactile distortions in this patient is compatible with the view that the distortion
effects have a rather high-level origin. Multiple single-case studies will, however, be required to establish whether this
association of deficits is typical, or whether visual and tactile size distortions are separable symptoms associated with
It has been proposed in previous papers that many right
hemisphere-damaged patients with neglect, mark lines to the
right of centre in the standard bisection task due to a
misperception of the lines (Milner, 1987; Harvey et al.,
1995). This was demonstrated directly by presenting patients
with a series of already transected lines, many of which were
transected at the precise midpoint. It was found that when
asked to point to the end of the line nearer to the transection
predominantly to the left, in some cases even when the line
was actually pre-transected 1 or 2 cm to the right of centre
(Milner et al., 1993; Harvey et al., 1995; see also Bisiach
et al., 1998a). In a similar vein, when patients were asked
to extend a line on paper to twice its length, they tended to
over-extend it when drawing leftwards, but under-extend
rightwards (Bisiach et al., 1996, 1998b; Chokron et al.,
1997). In both tasks, such leftward responding requires
patients to go against any neglect-induced pre-motor bias to
respond rightwards (‘directional hypokinesia’; Heilman et al.,
1985). Indeed, there are comparatively few patients who
respond predominantly rightwards in the landmark task, so
this factor appears to play a relatively minor role in determin-
ing the bisection errors of typical neglect patients.
Correspondence to: A. D. Milner, Department of Psychology, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK.
Tel: ?44 (0)191 374 2611; Fax: ?44 (0)191 374 7474; e-mail: firstname.lastname@example.org
The perceptual errors observed in the landmark task can
also be seen in tasks where the patient is asked to compare
two separate lines or rectangles presented side by side on a
television screen (Milner and Harvey, 1995; Irving-Bell et al.,
1999; Kerkhoff, 2000), or on paper (Milner et al., 1998).
Typically a neglect patient will perceive two horizontal lines
or rectangles as of equal length only when the leftward of
the two is actually some 10–15% longer than the one on the
right. Recent research indicates that the biases seen in both
this size-matching task (Ferber and Karnath, 2001) and in
the line-extension task (Doricchi and Angelelli, 1999) are
strongly associated with posterior lesions and with the pres-
ence of visual field defects.
A small number of patients with left hemisphere lesions
exhibit right visuospatial neglect. Right neglect following
left hemisphere damage is less common, and typically less
(e.g. Halligan and Marshall, 1995). However, we describe
here a patient who suffered from severe right visuospatial
neglect for several months after a left hemisphere stroke. We
report evidence for consistent perceptual size underestimation
of stimuli presented on the right and further demonstrate
that this effect can be observed for tactile as well as for
392C. L. Pritchard et al.
Table 1. DL’s performance on six subtests of the WAIS-R. Scaled scores, with age-adjusted scores in parentheses
Verbal subtestsPerformance subtests
InformationDigit span VocabularyPicture completionBlock design Object assembly
6 (7)5 (6) 9 (10)6 (9)4 (6)5 (8)
WAIS-R, Wechsler Adult Intelligence Scale-Revised.
Table 2. DL’s performance on the six conventional subtests of the Behavioural Inattention Test (*right neglect)
Line crossing Letter cancellation Star cancellationFigure and shape copyingLine bisectionRepresentational drawing
17/36*4/40*13/54* 1/4*0/9* 2/3*
DL, a 64-year-old man, sustained an ischaemic stroke of the
left hemisphere in May 1998 resulting in right hemiplegia and
right homonymous hemianopia to confrontation. A computed
tomography (CT) examination performed 9 days later
revealed a massive infarct in the territory of the left middle
cerebral artery, affecting the frontal lobe and most of the
parietal lobe and associated deep structures. The occipital
lobe was entirely spared, and the temporal cortex largely
(although not entirely) spared. Formal assessment of DL’s
visual fields was performed by Humphrey perimetry in June
1999. This confirmed that his right hemianopia was complete
and homonymous. The tests reported here were conducted
during the second month post-stroke, with DL’s informed
DL was left-handed by self-report and expressed a left
hand preference for 10 of 12 items on the Annett Handedness
Questionnaire. He was dysarthric but exhibited no signs of
aphasia in his spontaneous speech or in formal testing (only
two misspelling errors on the Short Minnesota Aphasia Test).
DL performed within normal limits on three verbal and three
performance subtests of the Wechsler Adult Intelligence
Scale-Revised (WAIS-R; Table 1). On the Benton Visual
Form Discrimination Test, he scored 26 (a score of 25 or
below indicates defective performance). His pre-morbid full-
scale IQ was estimated at 100 [National Adult Reading Test
Administration of the six conventional subtests of the
Behavioural Inattention Test confirmed the presence of severe
right visual neglect (total score ? 37/146; cut-off ? 129),
with neglect identified on every subtest (see Table 2). A
number of additional tests were carried out to characterize
further the nature of DL’s neglect impairment.
Materials and methods
Bisection. Following the method of Milner et al. (1993),
DL bisected 36 black 20 cm horizontal lines presented
horizontally and centrally on white sheets of A4 paper, with
12 lines per sheet. One sheet was presented at each of three
locations with respect to the body midline: with the sheet
symmetrically straddling the body midline or with its centre
displaced 30 cm into left or right hemispace. On each sheet,
three lines were presented in each of four cueing conditions:
no cue, with a capital letter adjacent to the left end of the
line, with a capital letter adjacent to the right end of the line
or with capital letters adjacent to both line ends. For each
letter that was present, DL was required to report its identity
prior to placing his transection mark. DL was instructed to
bisect each line centrally, using his left hand, proceeding line
by line down the sheet. After each transection, that line was
covered with a white card in order to prevent comparison of
the present response with previous responses. The order of
presentation for the spatial location condition was right, left,
centre. On each sheet of 12 lines, the order of cueing
condition was pseudo-randomized.
Landmark task. Following the method of Milner et al.
(1993), DL was presented with three series of 22 black 20 cm
horizontal lines presented individually on white sheets of A4
paper. Each line had been pre-transected at right angles with
a ‘landmark’ line 10 mm in length. Of the 22 lines, 10 were
asymmetrically transected (1, 2, 3, 4 or 5 mm to the right or
left of centre). These asymmetrical stimuli were uncued, and
served as ‘fillers’ to encourage the impression that all 22
lines might be asymmetrically transected. The remaining 12
lines were pre-transected at the objective midpoint, and three
werepresented ineachof thefourcueingconditions described
for the bisection task. In each trial, DL was required to make
a forced-choice discrimination, pointing to the end of the
Visual and tactile distortion in right neglect393
line that he judged to be closer to the transection mark. The
total set of 22 lines was presented once in each of three
spatial locations (as described for the bisection task). Spatial
location was blocked (centre, left, right) and the stimulus
order was randomized within each block.
Visual size matching (line drawings). In this task, DL
made relative size judgements regarding lateralized pairs of
horizontal lines, unfilled horizontal rectangles, circles and
radial (‘vertical’) lines. Stimulus pairs were printed in black
on white sheets of A4 paper presented at the body midline
so that one stimulus lay to either side of the midline. Sixteen
trials were presented for each stimulus type with stimulus
type blocked (vertical lines, horizontal rectangles, circles,
horizontal lines). In every trial a standard stimulus (8 cm in
length or diameter) appeared in at least one of the two
positions. Within each block of 16 trials, the standard stimulus
was paired with a smaller stimulus on the left (7.8, 7.6, 7.4,
7.2 or 7.0 cm) on five occasions and with a smaller stimulus
on the right on five occasions. In the remaining six trials,
standard stimuli were presented on both sides of the sheet.
The stimulus order was randomized within each block of 16
trials. In every trial, DL was required to make a forced-
choice discrimination, indicating verbally which stimulus he
considered to be the smaller of the two.
Visual and tactile size matching (solid objects). In this
task, DL made relative size judgements about the horizontal
extent of solid rectangular objects which were either visually
inspected, or haptically explored whilst blindfolded. Four
rectangular objects made of grey plastic were used. All
objects were 1.0 cm high and 1.0 cm wide, and were fitted
with pins to fix them in position on a 30 cm square board of
the same grey plastic. The board was placed directly in front
of the subject’s body midline. In each trial, two objects were
presented centred 15 cm from the edge of the board on the
subject’s side and displaced 7.5 cm to the left and right of
the midline. For visual discriminations, DL was allowed
unlimited viewing time. For tactile judgements, he was
blindfolded and had his left index finger placed on a starting
position equidistant from the two objects. The objects had to
be explored using the index finger only, but they could be
explored in any order and as many times as desired. In both
conditions, DL indicated his response by pointing to the
object that he believed to be smaller (or larger, see later).
In every trial, a standard stimulus (4.0 cm in horizontal
length) was placed in at least one of the two positions. Four
trial blocks were performed with 24 trials in each block
following eight initial practice trials. Within each block of
24 trials the standard stimulus was paired with a smaller
stimulus on the left (3.5, 3.0, 2.5 cm long) on six occasions,
and with a smaller stimulus on the right on six occasions. In
the remaining 12 trials, standard stimuli were presented on
both sides of the board. The stimulus order was randomized
within each block of trials. In every trial, DL was required
to make a forced-choice size discrimination, which was
Fig. 1. DL’s mean leftward line bisection errors as a function of spatial
location and cueing condition (negative is left).
indicated verbally. Stimulus modality was blocked in an
ABBA design beginning with visual presentation. The precise
discrimination required (‘which is longer’ or ‘which is
shorter’) was blocked in an AABB design beginning with
Line bisection task
As shown in Fig. 1, DL made large leftward bisection errors
(mean error ? –19.6 mm, SE ? 1.9). A two-way ANOVA
by spatial location and cueing condition revealed significant
main effects for both factors (cue: F(3, 24)? 4.1, P ? 0.05;
space: F(2, 24) ? 23.3, P ? 0.001) and no significant
interaction. Bonferroni post-hoc analysis of the cueing effect
revealed that a right-sided cue reduced the extent of DL’s
leftward errors compared with a left-sided cue (P ? 0.05);
none of the other cueing conditions differed from one another.
Bonferroni post-hoc analysis of the spatial location effect
found that DL made reliably larger leftward errors for lines
presented in right hemispace than for lines at central or
leftward locations (P ? 0.0005 in both cases).
When presented with centrally pre-transected lines, DL indi-
cated that the right half of the line appeared to be shorter in
every single trial (precluding analysis of the effects of
spatial location and cueing condition). Indeed, even when
the landmark was situated to the left of the midline, he
indicated that the rightward portion was shorter in 13/15
trials. Amongst 12 age-matched controls tested on the same
task, none judged the right half of the centrally transected
lines to be shorter in more than 64% of trials. It should also
be noted that DL pointed accurately to the right-hand end of
each line when indicating that this lay closer to the transection
394C. L. Pritchard et al.
Fig. 2. The number of ‘right is smaller’ responses (from 16) made by DL
when judging the relative size of horizontal lines, (unfilled) horizontal
rectangles, circles and ‘vertical’ lines printed on paper.
mark. His rightward underestimation cannot therefore have
been due to a failure to explore the whole of the line.
Visual size matching (line drawings)
As shown in Fig. 2, DL judged horizontal lines, horizontal
rectangles and circles presented to the right to be smaller
than those presented to the left (P ? 0.05, binomial test for
each of the three stimulus types). This was not the case for
vertical lines (P ? 0.05, binomial test, in the opposite
In order to check that DL’s underestimation of rightward
horizontal extents was not due simply to a failure to fixate
far enough rightwards, the horizontal line trials were repeated
with the instruction that DL should place a pencil mark at
both ends of each line (this was done after he had indicated
which of the lines appeared shorter). DL judged the right
line to be shorter in all of 16 trials. He was also able to mark
both ends of each line accurately and without any help,
indicating that he could indeed explore visually the whole of
each line. Occasionally, after DL had placed his pencil marks,
he was again asked to say which stimulus appeared shorter.
In no such trial did DL reverse his original judgement that
the right stimulus was the shorter.
Visual and tactile size matching (solid objects)
The total number of trials in which the right object was
judged to be smaller (or the left object to be larger) was 35/
48 and 36/48 for visual and tactile presentations, respectively
(binomial test, P ? 0.001 in both cases). DL thus perceived
the rightmost object to be smaller than the left significantly
more often than vice versa, irrespective of the modality of
This study reports a case of right neglect following left
hemisphere damage in a left-handed man. Patient DL is
unusual in exhibiting severe and persistent neglect following
a left hemisphere lesion (Halligan and Marshall, 1995).
He is also remarkable for having developed no detectable
language impairments despite an extensive left hemisphere
infarct that affected most of the parietal lobe. This latter fact
suggests that the normal left hemisphere dominance for
speech and language may have been reversed in this patient,
a pattern that is estimated to be present in about 15% of the
left-handed population (Rasmussen and Milner, 1976). If this
is the case, then it is possible that DL’s impaired spatial
awareness does not represent a specifically left hemisphere
variety of neglect, but a relatively typical right hemisphere
pattern expressed in mirror image form due to reversed
The notion that DL might represent a ‘mirror image’ of a
left neglect patient is consistent with the typicality of his
impairments across a range of tasks. DL demonstrated neglect
on each of the conventional subtests of the Behavioural
Inattention Test and his line bisection errors were influenced
by overt cueing and by manipulations of spatial location
(cf. Riddoch and Humphreys, 1983). Moreover, the data from
five tasks (line bisection, landmark, pictorial size matching,
tactile and visual object size matching) indicate a pronounced
rightward size underestimation in DL. The magnitude of this
effect is comparable with the leftward size underestimation
previously reported in right brain-damaged patients with left
neglect, using identical tasks (Milner et al., 1993, 1998;
Harvey et al., 1995; Milner and Harvey, 1995).
These findings are consistent with the idea that underes-
timation of the size of objects on the neglected side is an
integral part of the neglect syndrome. At the same time, it is
important to note that DL suffered from a right field hemian-
opia, so that our data are consistent with those reported more
recently by Doricchi and Angelelli (1999) and Ferber and
Karnath (2001). That is, we may suppose that DL’s lesion
placed him in a category of neglect patients particularly
prone to experiencing a distorted perception of visual size.
But is the visual field defect typically seen in neglect patients
who show size distortion the cause of that distortion, or just
a correlate of it, both symptoms being due to the posterior
location of the brain damage? That is, is the size distortion
in neglect a simple consequence of a rather low-level visual
loss? That such distortion certainly can occur as a result of
damage that causes hemianopia but not neglect, seems clear
from the results of Ferber and Karnath (2001). This does
not, however, imply that the distortion is caused by the
hemianopia. Even without neglect, there may be damage to
higher visual areas as well as to early visual cortex (V1 and/
or V2/V3), and it could be the former damage rather than
the latter that causes the distortion.
Our data showing DL’s distorted perception of tactile as
well as visual size offer a new perspective on the causes of
this relationship between visual field defects and perceptual
abnormality. In particular, they offer support for the view of
Bisiach et al. (1996), who suggested that in neglect patients
‘the left–right dimension of space representation is settled,
Visual and tactile distortion in right neglect395
as it were, on a logarithmic scale, with compression on the
ipsilesional side and expansion on the contralesional’. That
is, the present data are consistent with the notion that
incoming sensory stimulation is projected on to a supramodal
cerebral substrate for space representation that has been
distorted due to posterior brain damage. In contrast, if
incoming visual information was itself distorted and inter-
preted as such by an unbiased spatial processor [as implicitly
assumed by Milner (1987)], then tactile distortion would not
necessarily be expected to be present.
Of course, the spatial processor that has been damaged by
the lesion need not be truly supramodal. The objects we used
in the tactile matching task, had, after all, been observed
during visual size matching by the patient before he was
blindfolded. Presumably, therefore, he would have had little
trouble in forming a visual image of the apparatus and of
the rectangular blocks used, even when only receiving tactile
information about them. It is quite possible, in other words,
that the typical strategy used (by healthy as well as brain-
damaged people) in our tactile matching task is to transform
the input from each object into a visual image, and to
would then operate on the visual representation, just as
neglect itself can operate imaginally in many patients (Bisiach
and Luzzatti, 1978; Bisiach et al., 1979), causing the apparent
‘tactile’ size distortion.
On the other hand, we must be mindful of the fact that
the co-occurrence of visual and tactile size distortion in a
single patient does not necessitate shared functional causality
between the two deficits. It is possible that they represent
separable impairments that, in this patient, happen to co-
occur. The relationship between visual and tactile size under-
estimation might thus be similar to that found between visual
and tactile neglect for search tasks. An early group study
observed an association between left-sided omissions in
visual and tactile search and hypothesized a supramodal
disorder of spatial awareness to explain this association
(De Renzi et al., 1970). However, subsequent multiple single-
case studies have demonstrated that the two symptoms are
in fact doubly dissociable (Barbieri and De Renzi, 1989;
Cubelli et al., 1991). Similar multiple single-case analyses
will be required to determine the nature of the relationship
between visual and tactile size distortion. The present study
provides a starting point for these investigations by estab-
lishing the existence of tactile size distortion in neglect,
comparable in nature to the visual distortions that many
We conclude from this single-case study that right-sided
neglect caused by a left hemisphere lesion can cause visual
size distortions equal and opposite to those often seen in
patients with left-sided neglect. Furthermore, the visual size
misperception seen in our patient was mirrored by a similar
degree of tactile size misperception. We conclude that the
patient was unlikely to have been experiencing merely the
Our data demonstrate the existence of tactile size distortion
in neglect and highlight the possibility that this may result
from a disordered supramodal spatial representation, or from
a rather high-level visuospatial disorder affecting visual
The object size-matching task was developed in collaboration
with Professor E. Bisiach. We thank Dr R. C. Roberts for
his interpretation of DL’s CT scan, and DL for his patience
and co-operation during the testing. We also thank two
anonymous referees for their constructive contributions. This
study was supported by an MRC studentship to CLP and a
Wellcome Trust project grant (#048060) to ADM.
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Received on 6February, 2001; resubmitted on 15May, 2001; accepted
on 15 June, 2001
Visual and tactile size distortion in a
patient with right neglect
C. L. Pritchard, H. C. Dijkerman,
R. D. McIntosh and A. D. Milner
One typical feature of the neglect syndrome in patients with right hemisphere
damage is that they bisect horizontal lines to the right of centre. It has been
argued that to a large extent these bisection errors can be attributed to a
perceptual change whereby the patient experiences the left half of a line as
shorter than the right half, causing them to set the midpoint of the line towards
the right. We describe here a patient with a left hemisphere lesion and
rightward neglect, who consequently makes bisection errors in a leftward
direction. We carried out a series of tests which confirmed that he shows a
subjective visual distortion in the converse direction, i.e. a perception of
horizontal extents on the right as shorter than extents on the left. We also
found that he shows a similar distortion in his tactile perception. The
association of visual and tactile distortions in this patient is compatible with
the view that the distortion effects have a rather high-level origin. Multiple
single-case studies will, however, be required to establish whether this
association of deficits is typical, or whether visual and tactile size distortions
are separable symptoms associated with neglect.
Neurocase 2001; 7: 391–6
Neurocase Reference Number:
Primary diagnosis of interest
Right-sided unilateral neglect
Author’s designation of case
Key theoretical issue
d Contralesional size underestimation is observed for horizontal extents
presented in both visual and tactile modalities. This report provides a novel
existence proof of tactile size underestimation. The observed association of
deficits further suggests the possibility of a high-level supramodal disorder of
Key words: perception; distortion; neglect; size; tactile; visual
Scan, EEG and related measures
Annett Handedness Questionnaire, Benton Visual Form Discrimination,
Behavioural Inattention Test (six conventional subtests), Humphrey Perimetry,
National Adult Reading Test (NART), Short Minnesota Aphasia Test, Wechsler
Adult Intelligence Scale-Revised (WAIS-R; three verbal and three per-
Landmark task, line bisection, tactile size matching, visual size matching
d Left middle cerebral artery territory: frontal, temporal, parietal