Fondazione Mondino - Clinica Neurologica dell'Universita`, Pavia

(Direttore: prof. F. Savoldi) -Centro di Neuropsichiatria Biologica

VERBAL AND VISUAL-MOTOR DIGIT SPANS

IN DEMENTED INPATIENTS: A CONTROLLED STUDY

Renato Cocchi, Francesco Zerbi, and Faustino Savoldi

(Italian translation / traduzione in italiano) 

Summary

A visual-motor digit span can be investigated by having the subject indicate in the proper order the numbers he heard, by pointing with the non-dominant hand to the cards placed randomly in front of him and each card bearing a number from 1 t 9. Verbal and visual-motor digit spans? in normal subjects, have coincidental scores which agree the Miller's (1956) "magical" number 7, plus or minus two.

The two digit spans performed in the same subject seem exploring different brain areas. Compared to 3 control groups, the 1st matched for age, the 2nd homogeneous for diagnosis of affective illness, and the last group of miscellaneous non depressive inpatients, the digit spans' single or summed up verbal and visual-motor scores of 33 demented significantly decreased and lost the lower limit in one or both digit spans.

The coincidental scores of the experimental group has been also found significantly reduced, while the same did not result for the control groups. The age of onset of dementia appears influencing the scores, being in late-onset demented inpatients the verbal digit span better preserved, and vice-versa.

Key words: verbal digit span; visual-motor digit span; dementia.

Theoretical bases

Cases

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The Digit Span Test (DST) with direct number repetition, as outlined in WAIS, is a complex test which entails acoustic input and verbal output. In an individual without speech defects the DST with direct number repetition explores especially a component of acoustic memory.

The use of verbal language in this case is only one of the possible response modes, and it is surely the simplest one to employ. The neuro-anatomy of central acoustic pathways suggested us the possibility of a different mode of response, perhaps related to different brain areas explored.

While maintaining the acoustic input however it is possible to elicit a visual-motor response by having the subject indicate the number he heard by pointing to one of nine cards placed randomly in front of him (each card bearing a number from 1 to 9).

After originating from the cochlea nuclei, the central acoustic pathways partially decussates at the level of the bulbo-pontine junction. Direct fibres pass through the lateral lemniscus, the inferior quadrigeminal colliculus and the corpus geniculatum mediale to reach the primary auditory area of the cerebral cortex situated on the superior face of the first temporal gyrus (areas 41and 42 of the Heschel's transverse gyrus).

Considering this latter, we can suggest that a visual-motor DST response produced by non-dominant hand correlates easily to the exploration of acoustic areas, acoustic and visual-motor associative areas and motor areas of the non dominant hemisphere. On the basis of these premises a study was performed on the patients of a neuropsychiatric ward.

Subjects, materials and methods.

The experimental group consisted o 33 inpatients ranging from 55 to 7 years (mean: 62.42) affected with various forms of dementia as diagnosed by Hachinski Scale (Hachinski et al., 1975), WAIS and Hughes Dementia Rating Rating Scale (Hughes et al., 1982) (Table 1).

Control group 1, matched for age, consisted of 21 non-demented inpatients ranging from 55 to 79 years (mean: 63.24) and affected, for the most part, with various forms of depression (Table 2).

Control group 2 consisted of 20 subjects between 26 and 54 years (mean: 42.20) diagnosed as having various forms of mood disorders (Table 3).

Control group 3 consisted of 19 subjects between 16 and 53 years with various neurological and non-depressive psychiatric illnesses (Table 4). The test was performed by using the two digit series of the WAIS DST. The first digit series was used to elicit the verbal response, while the second one served to provoke the visual-motor response. Only direct repetition was performed.

The visual-motor response was obtained by having the subject indicate the acoustically perceived digit series, in the proper order, by pointing with the non dominant hand to one at a time of the 9 number cards placed in random order in front of him. The test was administered at the beginning of each patient hospital stay. Each subject gave both verbal and visual-motor responses.

The two digit spans were evaluated according to WAIS norms. Student "t" test and Chi Square test were used for statistical analysis of the results. The experimental group was compared to each of the control groups (Table 5).

Each one of the four subgroups obtained by dividing the experimental group according to dementia type was compared to control group 1 (Table 6).

The above comparison were performed for the sums of verbal and visual-motor digit spans as well as singly for each homologous response (i.e. verbal vs. verbal; etc). The incidence of coincidental verbal an visual-motor scores, higher verbal than visual-motor scores or higher visual-motor than verbal scores were quantified for all groups.

By means of Chi Square test, with Yates correction, if needed, the sums so obtained in the experimental group were compared to those of each control group (Table 7).

Results.

First of all it must be said that the test is very easy to perform an needs few minutes of time. Results are reported in Tables 1-4 and statistical analyses in Tables 5-7.

Table 1: experimental group's epidemiological and clinical data and DST's scores.

No. of S	Sex	Age (yrs)	Diagnoses	Digit span scores
				Verbal	Visual-motor	Verbal + visual-motor
1	f	60	SDAT	4	3	7
2	f	75	SDAT/brain atrophy	4	4	8
3	f	77	SDAT/senile tremor	4	4	8
4	f	72	SDAT	3	3	6
5	f	63	SDAT	4	4	8
6	f	62	SDAT	5	4	9
7	f	73	SDAT	4	6	10
8	f	63	SDAT	4	4	8
9	m	68	SDAT	4	5	9
10	f	67	SDAT	4	4	8
11	f	67	SDAT	4	4	8
12	f	66	SDAT	4	3	7
13	f	79	SDAT	4	6	10
14	f	55	Parkinson dementia	4	3	7
15	f	69	Parkinson dementia	4	4	8
16	f	63	Parkinson dementia	5	6	11
17	f	61	Parkinson dementia	4	6	10
18	f	63	Parkinson dementia	4	3	7
19	f	70	Parkinson dementia	4	4	8
20	f	68	Parkinson dementia	4	4	8
21	f	66	Parkinson dementia	3	3	6
22	m	69	Parkinson dementia	4	5	9
23	f	62	Parkinson dementia	5	6	11
24	f	59	Presenile dementia	3	2.5	5.5
25	f	62	Presenile dementia	5	4	9
26	f	59	Presenile dementia	3	2.5	5.5
27	f	64	Presenile dementia	6	7	13
28	m	56	Presenile dementia	3	4	7
29	f	55	Presenile dementia	3	2	5
30	f	68	MID	5	4	9
31	f	71	MID	3	3	6
32	f	60	MID	3	5	8
33	f	68	MID	5	4	9
Average		65.42 +/- 5.71		4	4.12	8.12

Table 2: Age matched control group 1.

No. of S	Sex	Age (yrs)	Diagnoses	Digit span scores
				Verbal	Visual-motor	Verbal + visual-motor
1	f	55	Depression	6	6	12
2	f	65	LAS	5	5	10
3	f	66	Senile depression	3	3	6
4	f	67	Depression	5	5	10
5	f	55	Anxious depression	6	6	12
6	m	63	Depression	6	6	12
7	f	57	Depression	5	5	10
8	f	64	Depression	6	6	12
9	f	58	Depres./ epilepsy	5	5	10
10	f	55	Atypical depression	5	5	10
11	f	60	Depression	6	4	10
12	f	58	Depression	6	6	12
13	f	70	Senile depression	5	5	10
14	f	67	Depression	5	6	11
15	f	79	Senile depression	6	6	12
16	f	70	Depression	4	4	8
17	f	62	Depression	5	4	9
18	f	70	Phob.Obs. neurosis	6	5	11
19	f	58	Depression	6	6	12
20	f	74	Depression	6	6	12
21	f	55	Depression	6	6	12
Average		63.24 +/- 6.88		5.38	5.24	10

Table 3: Control group 2, homogeneous for depressive mood.

No. of S	Sex	Age (yrs)	Diagnoses	Digit span scores
				Verbal	Visual-motor	Verbal + visual-motor
1	f	51	Bipolar depression	7	7	14
2	F	51	Bipolar depression	5	5	10
3	f	54	Depression	6	6	12
4	f	53	Depression	5	5	10
5	f	50	Depression	6	6	12
6	f	49	Depression	5	5	10
7	m	31	Depression	6	7	13
8	f	35	Depression	6	6	12
9	m	29	Anxious depression	7	7	14
10	f	26	Depression	3	3	6
11	f	45	Depression	5	5	10
12	f	43	Depression	6	6	12
13	f	29	Depression	6	6	12
14	f	40	Depression	6	6	12
15	f	39	Depression	6	6	12
16	f	45	Depression	4	4	8
17	f	40	Depression	4	4	8
18	f	37	Depression	5	5	10
19	f	48	Depression	4	5	9
20	f	49	Depression	5	5	10
Average		42.20 +/- 8.73		5.35	5.45	10.80

Table 4: Control group 3, with miscellaneous non depressive pathologies.

No. of S	Sex	Age (yrs)	Diagnoses	Digit span scores
				Verbal	Visual-motor	Verbal + visual-mot.
1	f	46	Transverse myelitis	6	6	12
2	m	16	Brain insult sequelae	6	6	12
3	m	29	Epilepsy	4	4	8
4	m	22	Borderline pers. dis.	4	4	8
5	f	26	Cephalalgia	5	5	10
6	f	33	Discopathy	6	6	12
7	m	20	Atypical psychosis	6	6	12
8	m	42	Cephallagia	5	5	10
9	f	41	Possible MS	5	5	10
10	f	36	Facial nerve pathol.	5	5	10
11	m	38	Schizophrenia	4	4	8
12	f	44	Cephalalgia	6	6	12
13	m	53	Peripher. neuropathy	7	7	14
14	m	19	Schizophrenia	5	5	10
15	f	18	Cephalalgia	6	6	12
16	f	24	Mental retardation	3	4	7
17	f	29	Episodic delusion	5	5	10
18	f	22	Alcohol abuse	4	5	9
19	f	46	Cerv.-arthr. myelopath.	4	4	8
Average		31.79 +/- 11.29		5.05	5.16	10.21

Table 5: Comparison of digit span scores between experimental group (EG)

and control groups (CGx) (one-tail test)

Vs. Control group 1	" t "	p
Verbal EG vs. verbal CG 1	- 6.41	< 0.0005
Visual-motor EG vs. visual-motor CG1	- 3.64	< 0.0005
Verbal + visual-motor EG vs. verbal + visual-motor CG1	- 5.27	< 0.0005
Vs. Control group 2
Verbal EG vs. verbal CG2	- 5.48	< 0.0005
Visual-motor EG vs. visual-motor CG2	- 4.00	< 0.0005
Verbal + visual-motor EG vs. verbal + visual-motor CG2	- 5.76	< 0.0005
Vs. Control group 3
Verbal EG vs. verbal CG3	- 4.25	< 0.0005
Visual-motor EG vs. visual-motor CG3	- 3.24	< 0.0025
Verbal + visual-motor EG vs. verbal + visual-motor CG3	- 3.09	< 0.0025

Table 6: Comparison of digit span scores: Experimental subgroups (ESG)

homogeneous for diagnosis vs. Control Group 1 (one-tail test)

SDAT subgroup (12 Ss)	" t "	p
Verbal ESG vs. verbal CG 1	- 6.27	< 0.0005
Visual-motor EG vs. visual-motor CG1	- 3.31	< 0.0005
Verbal + visual-motor EG vs. verbal + visual-motor CG1	- 4.84	< 0.0005
Parkinson dementia subgroup (10Ss)
Verbal ESG vs. verbal CG1	- 4.51	< 0.0005
Visual-motor ESG vs. visual-motor CG1	- 2.14	< 0.025
Verbal + visual-motor ESG vs. verbal + visual-motor CG1	- 3.37	< 0.0025
Senile dementia subgroup (6 Ss)
Verbal ESG vs. verbal CG1	- 3.58	< 0.0025
Visual-motor ESG vs. visual-motor CG1	- 2.97	< 0.005
Verbal + visual-motor ESG vs. verbal + visual-motor CG1	- 3.40	< 0.005
MID subgroup (4 Ss)
Verbal ESG vs. verbal CG1	- 2.95	< 0.005
Visual-motor ESG vs. visual-motor CG1	- 2.58	< 0.01
Verbal + visual-motor ESG vs. verbal + visual-motor CG1	- 3.05	< 0.005

Table 7: Direction of difference between verbal digit span and visual-motor digit span

in the same person. Keys: (=): no difference; (+) Verbal higher than visual-motor digit span;

(-) : Verbal lower than visual-motor digit span.

Group	Key	No. of Ss	%
Experimental Group	(=)	12	36.36
	(+)	11	33.33
	(-)	10	30.31
Control Group 1	(=)	17	80.89
	(+)	3	14.29
	(-)	1	4.76
Control Group 2	(=)	18	90.00
	(+)	0	0.00
	(-)	2	10.00
Control Group 3	(=)	17	89.47
	(+)	0	0.00
	(-)	2	10.53

EG vs. CG1: Chi Square = 10.66 with 2 df and p < .01

EG vs. CG2: Chi Square = 15.26 with 2 df and p < .001

EG vs. CG3: Chi Square = 14.48 with 2 df and p < .001

In the experimental group, the sums of the two digit spans as well as single digit spans were found, on an average, significantly lower than these obtained in all three control groups.

The experimental subgroups, homogeneous for diagnosis, had digit span sums and single digit span scores significantly lower than these obtained by the inpatients of the age matched control group 1.

There was a significant difference in the distribution of intra-subject coincidental scores, verbal higher than visual-motor scores, or verbal lower than visual-motor scores between the experimental group and  each control group.

Within the three control groups, intra-subject coincidental scores on the two digit spans were obtained in 80.89 to 90 % of Ss, but only in 36.35 % of demented inpatients.

Discussion.

It is difficult to discuss these results due to their excessive significance.

There is no doubt that digit span can also be evaluated using a non-verbal mode of response and thaô the two digit spans thus obtained tend to coincide in the same non-demented subject, and to be within the norm for healthy persons (7, plus or minus 2) established by Miller (1956).

The fact that visual-motor digit span may differ from the verbal one in the same individual tends credence to the idea that the former explores different cerebral structures. Our hypothesis for now, is that these structures are located in the non-dominant hemisphere when the non-dominant hand is used for the response.

This hypothesis is supported by the fact that visual-spatial acalculia is much more frequently associated with right hemisphere lesions (Benson and Weir, 1972; Troup, Bradshaw and Nettleton, 1983).

In our cases there could be a disturbance in visual-graphic number recognition or in identification of acoustic and visual-graphic inputs as referred to the same digit. Such a supposition could be confirmed only through studies employing PET.

There is scarce doubts that in both verbal and visual-motor digit spans the demented subject's performances were poorly than age-matched non-demented subjects and patients with depression or other neurological or psychiatric illnesses.

The presence of higher verbal than visual-motor digit span scores in the two older groups (demented subjects and control group 1) as opposed to the total absence of this phenomenon in the younger subjects of control groups 2 and 3, points to a possible correlation with age itself.

If so, there are two possible explanations which are not mutually exclusive. It can be seen as the result of facilitated echolalia in aged persons; indeed echolalia has been reported both in Alzheimer's and in Pick's dementias (Adams and Victor, 1985).

It could also be related to recent findings which confirmed earlier results (Seltzer and Sherwin, 1983)¬ and found that in late-onset post-senile Alzheimer's disease there is a better conservation of verbal capacity in the respect of visual-constructive capacity.

Thus there is a greater deterioration of the right cerebral hemisphere (Filley, Kelly and Heaton, 1986).

In the same investigation it was also found the exact opposite situation to be present in early-onset Alzheimer's disease: that is, there is better visual-constructive than verbal  performance corresponding to greater deterioration of the left brain hemisphere.

A similar phenomenon has been repeatedly reported in brain stroke aphasics and once more confirmed (Basso et al., 1987).

This differential vulnerability of the two hemispheres which varies according to the age of onset of dementia opens new problems of interpretation which for now surpass the intentions of this study.

After two preliminary studies (Cocchi, Sellerini and Pola, 1986; Cocchi, Pola, Rossetti and Pala, 1987), and this one too, we would like to note, in closing, that in 12 inpatients, part of them clinically diagnosed as demented and part as depressive pseudodemented, the scores of verbal and visual-motor digit spans did not confirm all the diagnoses, a fact fully supported by subsequent investigations (Cocchi,  Rossetti and Pola, 1988).

Of course, further cross studies, even in mentally retarded adults and children, are needed to confirm whether or not the results of this study can be a useful tool and what extent that may be employed.

References.

Adams R.D., Victor M.: Principles of neurology. 3rd edition. McGraw-Hill, New York 1985:231-242.

Basso A., Bracchi M., Capitani E., Laiacona M., Zanobio M.E.: Age and evolution of language area functions. A study on adult stroke patients. Cortex 1987, 23: 475-483.

Benson B., Weir W.: Acalculia: Acquired anarithmetria. Cortex 1972, 8: 465-472.

Cocchi R., Sellerini M., Pola A.: Ricerche sulla validita` del Digit Span nei test di memoria. In: Pavoné E., Saraceni F. (a cura di): Atti del I Congresso Nazionale SIPG. Vol. II. Idelson, Napoli 1986: 535-539.

Cocchi R., Pola A., Rossetti R., Pala P.: Digit Span verbale e visivo-motorio in dementi e in soggetti di controllo: tre sottogruppi di risposte. In: Pavoni E., Saraceni F. (a cura di): Atti del II Congresso Nazionale della SIPG. Vol. II. Idelson, Napoli 1987: 153-156.

Cocchi R., Rossetti R., Pola A.: Digit span verbale e visivo-motorio in 12 casi di incerta diagnosi tra demenza e pseudodemenza. In: Pavoni E., Saraceni F. (a cura di): Atti del III Congresso Nazionale della SIPG, Sorrento 1987 (in stampa).

Filley C.M., Kelly J., Heaton R.K.: Neuropsychologic features of early and late-onset Alzheimer's disease. Arch. Neurol. 1986, 43: 574-576.

Hachinski V.C., Iliff L., Dubolay G.H., McAllister V., Marshall J., Ross Russell R.W., Symon L.: Cerebral blood flow in dementia. Arch. Neurol. 1975, 32: 632-637.

Hughes C.P., Berg L., Coben L.A., Martin L.: A new clinical scale for the staging of dementia. Brit. J. Psychiat. 1982, 140: 566-572.

Miller G.A.: The "magical" number 7, plus or minus two: Some limits of our capacity for processing information. Psychol. Rev. 1956, 63: 81-97.

Seltzer B., Sherwin I.: A comparison of clinical features in early- and late-onset primary degenerative dementia. Arch. Neurol. 1983, 40: 143-146.

Troup R.D., Bradshaw J.L., Nettleton C.: The lateralisation of arithmetic and number processing: A review. Int. J. Neuroscience 1983, 19: 231-242.

First printed on It. J. Intellect. Impair. 1988, 1: 133-140.

Author's address: dr Renato Cocchi, via Rabbeno,3

42100 Reggio Emilia
renatococchi@libero.it

Italian translation / traduzione italiana

Theoretical bases

Cases

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