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Behavioural Neurology 21 (2009) 187–192
DOI 10.3233/BEN-2009-0244
IOS Press

Clinical Note

Visual agnosia for line drawings and
silhouettes without apparent impairment of
real-object recognition: A case report
Kotaro Hiraokaa,∗ , Kyoko Suzuki a,b , Kazumi Hirayamaa and Etsuro Moria
a

Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of
Medicine, Aoba-ku, Sendai, Japan
b
Department of Clinical Neuroscience, Yamagata University Graduate School of Medicine, Yamagata, Japan

Abstract. We report on a patient with visual agnosia for line drawings and silhouette pictures following cerebral infarction in the
region of the right posterior cerebral artery. The patient retained the ability to recognize real objects and their photographs, and
could precisely copy line drawings of objects that she could not name. This case report highlights the importance of clinicians
and researchers paying special attention to avoid overlooking agnosia in such cases. The factors that lead to problems in the
identification of stimuli other than real objects in agnosic cases are discussed.
Keywords: Visual agnosia, real objects, photographs, line drawings, silhouettes, cerebral infarction, posterior cerebral artery

1. Introduction
Visual agnosia is a relatively rare clinical syndrome
characterized by impairment in the visual recognition
of objects. Typically, agnosic patients have no underlying neurosensorial deficits, and do not suffer from
global cognitive impairment. They are easily able to
identify by touch or literal definition objects that they
cannot recognize visually.
Here, we report on a patient with visual agnosia for
line drawings and silhouettes following an ischaemic
stroke in the region of the right posterior cerebral artery.
The patient retained the ability to recognize real objects
and their photographs, and could precisely copy line
drawings of objects that she could not name.

∗ Corresponding author: Kotaro Hiraoka, MD, Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University
Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai,
980-8575, Japan. Tel.: +81 22 717 7358; Fax: +81 22 717 7360;
E-mail: khiraoka@mail.tains.tohoku.ac.jp.

2. Case report
A 74-year-old, right-handed woman with 12 years of
education was admitted to hospital having experienced
topographical disorientation for three days. Her medical history included more than 30 years of treatment
for hypertension, and cataract operations in both eyes.
When she got up one morning, she could not recognize where she was, a situation that resolved within a
few hours. Later that day, she was unable to return to
her flat from the nearby bus stop via the shortest route.
On admission to hospital, neurological examinations
revealed no abnormalities except bilateral superior altitudinal hemianopia, which was confirmed by Goldman perimetery. The patient’s only problem on the
ward was topographical disorientation, i.e. an inability
to remember the locations of places she visited every
day, such as the lavatory and rehabilitation room. She
could identify faces and objects on the ward without
difficulty.
Diffusion-weighted magnetic resonance images on
admission showed an infarction in the region of the

ISSN 0953-4180/09/$17.00  2009 – IOS Press and the authors. All rights reserved

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K. Hiraoka et al. / Visual agnosia for line drawings and silhouettes without apparent impairment of real-object recognition

Fig. 1. FLAIR images of MRI. The lesion involved the subcortical white matter beneath the right fusiform and lingual gyri, and the right half
of the splenium of the corpus callosum extending forward to the pulvinar. Old ischaemic lesions were also revealed in the white matter of the
bilateral frontal lobes and right cerebellar hemisphere, and a subcortical lesion beneath the left lingual gyrus.

right posterior cerebral artery. The lesions involved the
right occipital lobe and the right half of the splenium
of the corpus callosum extending forward to the pulvinar. In addition to these acute lesions including the
subcortical white matter of the right fusiform and lingual gyri, fluid-attenuated inversion recovery images
revealed old ischaemic lesions affecting the white matter of the bilateral frontal lobes and the right cerebellar
hemisphere, and a subcortical lesion beneath the left
lingual gyrus (Fig. 1). Single photon emission computed tomography showed decreased accumulation in the
medial part of the right occipital lobe, an inferior part
of the right temporal lobe, the right cerebellar hemisphere, and the ventromedial part of the left occipital
lobe.
Table 1 shows the results of standard neuropsychological examinations. The patient performed within the
normal range in the Wechsler Adult Intelligent ScaleRevised [11,17], Western Aphasia Battery [6,13] and
verbal fluency tests [1]. However, her performance on
the Wechsler Memory Scale-Revised [14,18] and Rey
Complex Figure Test [7] was poor, indicating amnesia
predominantly for visual materials.

Table 1
Summary of neuropsychological test results
Test
Wechsler Adult Intelligent Scale-Revised
Verbal IQ
Performance IQ
Full-scale IQ
Wechsler Memory Scale-Revised
Verbal Memory Index
Visual Memory Index
Delayed Recall Index
Rey Complex Figure Test
Copy
Immediate Recall
Delayed Recall
Recognition
Western Aphasia Battery
Aphasia Quotient
Cortical Quotient
Verbal Fluency (Phoneme)
Verbal Fluency (Category)

Result
96
70
82
75
66
60
32/36
0/36
1/36
15/24
94.2
94.1
12 (/1 min)
12 (/1 min)

3. Experimental investigations
3.1. Basic visual function
Corrected visual acuity of the right and left eyes was
20/20 and 20/25, respectively. Although contrast sensi-

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189

Table 2
Number (and percentage) of correct answers given by the patient and by age-matched control
subjects in the visual recognition tasks
Stimuli
Real objects (n = 20)
Colour photographs of objects (n = 12)
Monochrome photographs of objects (n = 12)
Line drawings of objects (n = 100)
Silhouette pictures of objects (n = 50)

Patient
20 (100%)
12 (100%)
12 (100%)
81 (81.0%)
41 (82.0%)

Control subjects (n = 5)
mean
SD
20 (100%)
0.0
12 (100%)
0.0
11.8 (98.3%)
0.0
99.6 (99.6%)
0.6
48.8 (97.6%)
1.2

SD: standard deviation.

tivity measured by a previously described method [10]
was mildly impaired throughout the range of spacefrequency, this impairment was not severe enough to
disturb the patient’s visual recognition of objects and
drawings. In the City University Colour Vision Test [4],
3 out of 10 trials were incorrect, which suggested a
tritan defect. The patient also made 3 errors in 13 trials
of Ohkuma pseudoisochromatic plates [8], suggesting
a deficiency in distinguishing red from green.
3.2. Visual recognition
The patient’s visual recognition ability was examined using real objects, photographs, line drawings and
silhouette pictures. The real objects consisted of 20
items in the object-naming task of the Western Aphasia
Battery [6] such as a pencil, a key and a knife, which
were placed one at a time on a table in front of the
patient. The stimuli for the photographs were colour
and monochrome pictures of 12 familiar objects such
as a sunflower, a butterfly, an apple and an airplane.
The stimuli for line drawings were 100 line drawings
of familiar objects, which we previously developed for
the picture-naming task [15]. All drawings were in
high-contrast black against white background and contained some texture. The stimuli for the silhouette pictures were 50 common objects selected from the Snodgrass and Vanderwart norms [12], which were painted
over with black. The categories of objects depicted
in line drawings and silhouettes included fruit, clothing, animals, vehicles etc. The objects depicted in the
photographs, line drawings and silhouettes were shown
from usual viewpoints and were 12 cm high or wide at
their maximum point. The patient was asked to name
or describe these objects.
Table 2 shows the results of the visual recognition
tasks carried out by the patient and by 5 healthy controls matched for age and education. The patient could
provide the correct names of all objects shown as real objects or depicted in colour or monochrome photographs. In contrast, she had difficulty recognizing

the line drawings of objects, and was unable to identify
and name correctly 19% and 18% of objects depicted in
line drawings and silhouettes, respectively. The errors
in the test of line drawings and silhouettes, respectively,
were classified as semantic (53%, 67%) when they had
a semantic relationship with the stimulus; no response
(26%, 0%) when the patient did not give any response;
and visual (21%, 33%) when they had a visual but not
a semantic similarity with the stimulus.
The patient could precisely copy line drawings of
objects that she was unable to name. However, even
after successful copying, she was unable to recognize
the drawn objects (Fig. 2). With verbal descriptions of
the objects, she could correctly name all 19 objects that
she failed to recognize visually.
For the assessment of auditory recognition, the patient was asked to name the objects by listening to a
specific sound, such as the sound of a moving train or
the barking of dogs. She could recognize all 12 stimuli
correctly. For the assessment of tactile recognition of
objects, with her eyes closed, the patient touched objects with her hands and then named or described them,
and successfully recognized all 10 stimuli.

4. Discussion
The patient showed topographical disorientation at
onset, and visual agnosia, achromatopsia and memory
disorder on detailed neuropsychological examination.
An ischaemic lesion of the subcortical white matter of
the right fusiform and lingual gyri, coexisting with an
old subcortical lesion beneath the left lingual gyrus,
resulted in bilateral superior altitudinal hemianopia,
achromatopsia and visual agnosia.
The patient had difficulty recognizing line drawings
and silhouettes. Following investigation of various aspects of basic visual functions, mild impairment of contrast sensitivity was detected, but her ability to copy
pictures flawlessly indicated that this did not interfere
with picture recognition. Mild achromatopsia was al-

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K. Hiraoka et al. / Visual agnosia for line drawings and silhouettes without apparent impairment of real-object recognition

Fig. 2. The results of copying line drawings and oral responses before and after copying.

so detected. However, it did not impair the patient’s
ability to recognize line drawings and silhouettes, as
these were monochrome. In view of the fact that she
was able to recognize colour and monochrome photographs, which are visually much more complex than
line drawings and silhouettes, it is clear that her performance was not being affected by the complexity of
the pictures. These findings suggest that the patient’s
impaired recognition of line drawings and silhouettes
was not due to a disorder of low-level visual functions.
With verbal descriptions of objects, she could correctly
name all the objects that she failed to recognize visually, which indicated that access to semantics from verbal
input is spared. Based on these results and on the fact
that tactile recognition and auditory recognition were
preserved, the impaired recognition of line drawings
and silhouettes must have been due to visual agnosia.
In contrast to agnosia for line drawings and silhouettes, impairment of real-object recognition was not apparent in either the patient’s daily life or in our experimental investigations. In many reported cases of visual
agnosia, there is impaired visual recognition of objects,
which causes problems in daily life [2,9,16]. Although

there is no convincing evidence that our patient’s agnosia was restricted to line drawings and silhouettes,
as the stimuli of the different tasks (i.e. recognition of
real objects, colour and monochrome photographs, line
drawings and silhouettes) were not the same in terms of
numbers, familiarity, category etc., visual agnosia for
real objects in this case was so subtle, if present at all,
that it could not be observed in daily life and on routine
psychological testing. Special attention should be paid
so as not to overlook agnosia in similar cases.
For many patients with visual agnosia, recognition
of real objects is superior to recognition of line drawings [3,5,9,16]. Some previous case studies of visual agnosia have shed light on the mechanism of the
discrepancy between the recognition of real objects
and the recognition of the same objects shown in twodimensional formats. In a study by Humphrey et al. [5],
an agnosic patient was shown real objects under different conditions and the same objects depicted in colour
and monochrome photographs and in line drawings.
The real objects were presented under four different
viewing conditions: (i) full viewing, (ii) monocular
viewing, in which one eye was covered, (iii) monochro-

K. Hiraoka et al. / Visual agnosia for line drawings and silhouettes without apparent impairment of real-object recognition

matic viewing, in which the object was viewed through
a red-coloured filter, and (iv) monocular viewing combined with monochromatic viewing. The accuracy of
naming varied markedly over the different conditions
of presentation, ranging from 71% correct in full viewing to only 11% correct in the case of line drawings.
There was a regular decrease in the number of objects
recognized by the patient as more surface information
was removed. The study’s authors suggested that the
presence of surface properties, such as colour and texture, and depth information aided recognition.
In a single case study by Chainay et al. [2], an agnosic
patient was shown objects and asked to name them
in different conditions, i.e. coloured and monochrome
photographs, monochrome line drawings, and correctly and incongruently coloured line drawings. Correct
naming was worse with monochrome line drawings
(30% correct) relative to all other conditions, even including incongruently coloured drawings (43–47% correct). From this result, the study’s authors suggested that for their patient, who was achromatopsic, the
colours, whether appropriate for the objects or not, provided segmentation cues about the surfaces and parts
of the objects, since common surfaces and parts tend to
have similar colour and luminance values. Another experiment was conducted in the same study to evaluate
the contribution of three-dimensional cues to recognition. Real objects were presented within arm’s reach
(to enable binocular disparities) or at a greater distance
(to reduce the effectiveness of binocular cues). In addition, the patient viewed the objects with his head free
or in a fixed position (in the latter case, to remove motion parallax cues from head movements). Recognition
performance did not differ significantly in conditions
in which the objects were shown nearby with the patient’s head free or fixed and when they were shown at a
distance with the patient’s head free (73–80% correct).
Conversely, recognition performance was poorer when
the objects were shown at a distance with the patient’s
head fixed (49% correct). These results suggest that
depth information, obtained by both binocular disparity cues and head movements, facilitated object recognition. Overall, the authors concluded that information
about depth and surface shading can contribute to object recognition when edge-based object recognition is
impaired.
In the light of these studies, the discrepancy between
the recognition of real objects and the recognition of
the same objects shown in 2D formats in many cases of
visual agnosia may be due to the difference in the number of visual cues for recognition in each format of the

191

stimuli. Compared with real objects, photographs lack
information about size and 3D shape that is gained from
binocular disparity. Line drawings only have contour,
and insufficient cues of internal details, texture and 3D
shape. Compared to line drawings, silhouettes gain luminance, but lose cues of internal details, texture and
3D shape. In the condition in which the ventral visual
pathway that plays a key role in object recognition is
disordered, the paucity of visual cues may contribute
significantly to the failure of recognition.

Acknowledgment
This work was supported by Grant-in-Aid for Scientific Research on Priority Areas-System study on
higher-order brain functions-from the Ministry of Education, Culture, Sports, Science and Technology of
Japan (20020004).

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