NOTE
DISTURBANCES OF CROSS-LOCALIZATION OF
FINGERTIPS IN A CALLOSAL PATIENT
Kazuo Satomi l , Yosbitoshi Kinoshita2 and Senri Hirakawa l
CSecond Department of Internal Medicine and 2Department of Laboratory Medicine,
Clinical Psychology, Gifu University School of Medicine)

INTRODUCTION

A test of cross-localization of fingertips (CLF) is usually performed as follows: the patient with his eyes closed, hands extended and palms up is touched on a finger of one hand
and asked to touch the corresponding finger of the other hand with the thumb of that hand.
CLF disturbance, i.e., the inability to perform this task in both directions (right-to-Ieft and
vice versa), has been reported in patients with callosal lesions (Balaceanu et ai., 1970; Jeeves;
Simpson and Geffen, 1979; Leiguarda, Starkstein and Berthier, 1989; Sperry, Gazzaniga and
Bogen, 1969; Volpe et ai., 1982). The fact that the disorder is bi-directional, that the localization is normal when carried out with the same hand that is stimulated and that the test is
nonverbal (Bogen, 1979, 1985) suggests that the disturbance is due to callosal disconnection
between the somesthetic centers of the two hemispheres.
However, patients with callosal lesions often show left unilateral apraxia (Brion and Jedynak, 1972; Gazzaniga, Bogen and Sperry, 1967; Geschwind and Kaplan, 1962; Graff-Radford, Welsh and Godersky, 1987; Iwata et ai., 1980; Liepmann and Maas, 1907; Volpe et ai.,
1982; Watson and Heilman, 1983; Zaidel and Sperry, 1977) and/or left side tactile anomia of
body parts (Barbizet at ai., 1974; Degos et ai., 1987; Geschwind and Kaplan, 1962; Geschwind, 1965; Goldenberg et ai., 1985; Watson and Heilman, 1983). In such a case, it is possible
that CLF errors in left-to-right direction are due to left side tactile anomia, because the left hemisphere misnames the touched finger of the left hand and CLF errors in right-to-Ieft direction are due to left unilateral apraxia, which impairs the left hand ability to indicate the target
finger. If as predicted by the somesthetic transfer deficit hypothesis, the crucial information is
that concerning the stimulated hand, the CLF performance should be disturbed when the patient does not see this hand, but should be unaffected by excluding from vision the responding
hand. We now report a patient with CLF disturbance, left unilateral apraxia and left tactile
finger anomia caused by caUosallesions, in whom we tested the somesthetic transfer deficit
hyposthesis.

CASE REPORT

On November 19, 1982, a 64-year-old right-handed male, without any history of previous illness, suddenly developed a speech arrest followed by inability to stand and drowsiness. Four days after onset, he showed right hemiparesis, while spontaneous speech, repetition and comprehension of simple verbal commands were good. A computed tomography,
performed one month after onset, disclosed a low density area in the left medial frontal lobe
and the anterior two-thirds of the corpus callosum corresponding to the region irrigated by
the left anterior cerebral artery (Figure lA). Although his right hemiparesis recovered, he
consulted Gifu University Hospital on November 7, 1983, because his language was halting
and his right hand trembled when excited.
Neurological examination, carried out about one year after onset, revealed a patient who
was alert, co-operative and oriented in all spheres. There was no impairment of spontaneous
speech, comprehension and repetition. He has no limb or facial weakness. The right limbs
Cortex, (1991) 27,327-331

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K. Satomi, Y. Kinoshita and S. Hirakawa

were mildly spastic and the deep tendon reflexes of the right leg were brisk, although Babinski sign was not noted. He showed mild right hemiparetic gait. Grasping reflex was not
noted. There was no abnormality of cutaneous or deep sensation regarding touch, pain, temperature, vibration and position sense. His visual fields were apparently normal.
Neuropsychological examination failed to reveal aphasia, agnosia or other deficits except those due to the disconnection syndrome, i.e., left unilateral apraxia, left tactile finger
anomia, left unilateral agraphia, cross-replication deficit of hand postures, and cross-localization deficit of fingertips. Praxis of the left hand was tested on verbal command, imitation and object use. With eyes open, the patient could not carry out gestures on verbal command or on imitation. Object use with the left hand was mildly impaired with eyes open, and
much more impaired with eyes closed. The W.A.I.S. test, performed on February 2, 1984,
showed a verbal I.Q. of 97, a performance I.Q. of 70 and a total I.Q. of 87. M.R.I., performed on October 24, 1985, demonstrated a low signal area involving the anterior five-sixths
of the corpus callosum and the left medial frontal lobe (Figure lB).
MATERIALS AND METHODS

The patient was given the following set of finger identification tests.
(1) Tactile-manual test: a routine procedure for CLF with eyes closed has already been
mentioned. CLF with eyes open was performed in two ways; either the stimulated hand was
covered by a thick cloth and the patient was asked to look at his responding hand, or the responding hand was covered by the cloth and the patient was asked to look at his stimulated
hand. Ipsilateral localization of fingertips with eyes close requires the examiner to touch a
finger of one hand of the patient with eyes closed for him to indicate the stimulated finger
with the thumb of the same hand.
(2) Tactile-verbal test: the patient with eyes closed was requested to name the finger of
his hand touched by the examiner.
(3) Verbal-manual test: the patient with eyes closed indicated with the thumb of the same
hand the finger named by the examiner.

Fig. I - A: CT scan showing a low density area of the left medial frontal lobe. B: Magnetic resonance
imaging showing a low signal area of the anterior five-sixths of the corpus callosNm.

Cross-localization of fingertips

329

TABLEl

Test Results
Test items

Correct response rate
(percentage)

(1) Tactile-manual test
Ipsilateral localization
Eyes closed [ Cross-localization
[

E

yes open

Cross-localization with stimulated hand
invisible to the patient
[ Cross-localization with responding hand
invisible to the patient

(2) Tactile-verbal test
(3) Verbal-manual test
(4) Visual-manual test
(5) Verbal-visual test
(6) Visual-verbal test
with eyes open [Right hand ............... .
(7) Manipulation of objects
L~ft hand ................ .
[ with eyes closed [Right hand ............... .
Left hand ................ .
R-R (L-L): right-right (or left-left) hand stimulation and response.
L-R (R-L): left (right) hand stimulation and right (left) hand response.
V-R (V-L): verbal stimulation and right (left) hand response.
Vi-R (Vi-L): visual stimulation and right (left) hand response.
R-V (L-V): right (left) hand stimulation and verbal response.
NE: not examined.

R-R 83/84
L-L 77/68
L-R 611128
R-L 82/128
L-R 26/56
R-L 50/52
L-R 56/56
R-L 41156
R-V 52/55
L-V 44171
V-R 83/84
V-L 65/88
Vi-R 93/96
Vi-L 79/100
V-R 30/30
V-L 30/30

(100%)
(1ooOJo)

30/30

(100%)

NE

16/19
20120
19/35

(99%)
(88OJo)
(48OJo)
(64OJo)
(46OJo)
(96OJo)
(100OJo)
(73070)
(95%)
(62%)
(99%)
(74%)
(97%)
(79%)

(84%)
OOOOJo)
(54%)

(4) Visual-manual test: the examiner showed one of his finger to the patient for him to
point to the corresponding finger of his hand with the thumb of the same hand while this was
covered by a cloth.
(5) Verbal-visual test: the patient with eyes open pointed with his right or left index finger to the finger of the examiner's hand that had been named by the examiner.
(6) Visual-verbal test: the patient had his eyes open and named a finger displayed by the
examiner.
(7) Manipulation of objects: the patient manipulated familiar objects with his eyes closed or open.
Statistical calculation: a fourfold chi square test after Yates' correction or Fisher's exact
test (two-sided probability) was used when two tests were compared.

RESULTS

Table I shows the scores achieved by the patient on the various tests.
Ipsilateral localization of fingertips with eyes closed was almost perfect (right-to-right 99111,
correct, left-to-Ieft 881110 correct). eLF with eyes closed was impaired in both directions (left-toright 481110 correct, right-to-left 641110 correct), but the score in the left-to-right direction was significantly lower than that in the right-to-left direction (p < 0.05). With eyes open, the right-toleft performance was disturbed when the responding (left) hand was kept out of sight (eyes clo-

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K. Satomi, Y. Kinoshita and S. Hirakawa

sed vs. open: 64% and 73070 correct, respectively), whereas it improved when it could be viewed and it was the touched (right) hand to be kept out of sight (eyes closed vs. open: 64% and
96% correct, respectively, p<O.OI). The left-to-right performance with eyes open, contrariwise, ameliorated when the responding (right) hand was invisible to him (eyes closed vs. open:
48% and 100% correct, respectively), and it did not improve when the stimulated (left) hand
was invisible to him (eyes closed vs. open: 48% and 46% correct, respectively).
Tactile finger naming was impaired in the left hand (right hand 95% correct, left hand
62% correct, p<O.OI). Left hand response in verbal-manual and visual-manual tests was impaired (right hand vs. left hand: 99%,74% correct, p<O.OI, in the former test and 97%,
79% correct, p < 0.01, in the latter test). Verbal-visual and visual-verbal tests were perfect.
Left hand manipulation of objects was mildly impaired (84% correct) with eyes open, and
much more impaired with eyes closed (54% correct), p<0.05.
DISCUSSION

If cross-localization of fingertips (eLF) disturbance is caused by a deficit in the interhemispheric transfer of somesthetic information, the test scores should improve in both directions, when the test is performed with eyes open and the patient looks at his touched hand, since both hemispheres receive the visual information. On the other hand, no improvement is anticipated when the patient regards his responding hand as long as his touched hand is invisible
to him. Moreover, there should not exist a significant score difference between the right-to-Ieft
and left-to-right directions of eLF with eyes closed, because the disturbance is not dependent
on hemispheric dominance (Leiguarda et aI., 1989), but, rather, on a transfer deficit between
the two hemispheres. Yet with eyes closed, our patient showed significantly lower score in the
left-to-right direction than in the right-to-Ieft direction (p < 0.05). With eyes open, the right-toleft direction score did not improve when he regarded his touched hand, but it did improve
when he regarded his responding hand. On the contrary, the left-to-right direction score did not
improve when he regarded his responding hand, but it improved when he regarded his stimulated hand. Therefore, the eLF disturbance of our patient can not be explained by a deficit in
the interhemisperic transfer of somesthetic information, but can be explained by two independent mechanisms, one for the right-to-Ieft and the other for the left-to-right direction.
Disturbance of right-to-Ieft direction with eyes closed appeared to be due to a motor output deficit, because it improved when the test was performed with eyes open and the patient
regarded his left hand. This type of visually guided improvement in left hand movement has
also been reported in a test of object manipulation (Satomi and Goto, 1985).
Even when nonverbal stimulation and response modes were used in eLF (touching a finger and manual response), it is dubious to what extent the information processing was really
nonverbal, because each finger has its own name (Stone and Robinson, 1968). Left side tactile anomia of body parts has been repeatedly reported in patients with callosal lesions, and
left tactile finger anomia was indeed observed in our patient. Since the somesthetic transfer
deficit hypothesis could not adequately explain the left-to-right eLF disturbance with eyes
closed, we hypothesize that it was caused by left tactile finger anomia.
A possible explanation for the different performance in the two directions (Ieft-to-right
48% correct, right-to-Ieft 64% correct) was that his left tactile finger anomia was severer than
his left unilateral apraxia, as suggested by the lower percent correct in tactile finger naming
test (62%) than in verbal-manual test (74%) and visual-manual test (79%).
In conclusion, our patient's study suggests that when examining somesthetic transfer in
patients with callosal lesions, cross-localization of fingertips should always be performed with
eyes open and with eyes closed.
ABSTRACT

If defective cross-localization of fingertips (eLF) in callosal patients is due to a deficit in
the interhemispheric transfer of somesthetic information, when the patient's eyes are open,
eLF should be affected when the stimulated hand is excluded from vision, not when the
responding hand is excluded from vision. In order to investigate this hypothesis, a patient

Cross-localization of fingertips

331

with a callosal lesion was subjected to eLF with eyes closed and open. With eyes closed, the
eLF score in the left-to-right direction was significantly lower than that in the right-to-Ieft
direction. With eyes open, the eLF performance in the right-to-Ieft direction was impaired
when it was the responding hand to be excluded from vision, not when it was the stimulated
hand to be excluded from vision. It would, therefore, appear that the patient's eLF disturbance was not due to a somesthetic transfer deficit, but to left unilateral apraxia for the rightto-left direction errors and to left tactile finger anomia for the left-to-right direction errors.
Acknowledgments. We wish to thank Professor P. Rondot, MD, Paris, who provided us
with helpful comment and discussion.

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Kazuo Satomi, M.D. Second Department of Internal Medicine, Gifu University School of Medicine, 40, Tsukasa-machi, Gifu 500, Japan.