TIME AS A VARIABLE IN THE PERFORMANCE OF HEMISPHERE-DAMAGED PATIENTS

ON THE ELITHORN PERCEPTUAL MAZE TEST 1

Yvonne M. Archibald (Department of Clinical Neurosciences, Victoria Hospital, London, Ontario)

Evidence of selective impairment of hemisphere functioning following cerebral injury has been widely demonstrated. The left hemisphere (LH) has been shown to play a major role in processing language and speech (e.g. Broca, 1865; Penfield and Roberts, 1959; Milner, 1962) and skilled move­ments (Liepmann, 1908; Kimura and Archibald, 197 4 ), in right-handed adults, at least, while the right hemisphere (RH) has been shown to play a major role in processing visual-spatial information, particularly of a non-verbal nature (Kimura, 1963; Warrington and James, 1967; Newcombe, 1969).

There is also evidence that non-selective impairment, such as red3ced speed of performance, can follow cerebral injury. Slower reaction time (RT), for example, has been reported in brain-damaged as compared to normal groups by De Renzi and Faglioni (1965), Parsons and Bruhn (1973) and Howes and Boller (1975), among others. Newcombe (1969) observed that L and RH patients were slower in naming pictures of objects than normal controls. She further noted that R and LH groups were slower than normals in visual cube analysis and visual matching. This impairment in speed of reaction in L, as well as R, H groups, in both the RT studies and Newcombe's study, was observed over and above differentially selective impairment to the two hemisphere groups.

Apart from RT studies, time has not been used explicitly as a variable in research with brain-damaged patients. Accordingly, the Elithorn Perceptual Maze Test (EPMT, Elithorn, 1955; Benton, Elithorn, Fogel and Kerr, 1963) was selected to study the performance of brain-injured subjects under con­ditions of restricted and unrestricted time. The maze task is particularly amenable to such a study because it can be scored on both a timed (T) and an untimed (U) basis.

This study was supported in part by Grant No. M-10006 and Grant No. MH-01876 from the National Institutes of Health, U.S. Public Health Service, and by Grant No. 13-22-N90 from the Medical Research Council of Canada. The findings were reported at a meeting of the Academy of Aphasia, Victoria, B.C., 1975.

Cortex (1978) 14, 22-31.

1

23 The Elithorn perceptual maze test

MATERIAL AND METHOD

Subiects

L and RH patients and normal controls were compared on the EPMT under T and U conditions. The LH group consisted of 18 aphasic and 11 nonaphasic patients. There were 19 RH patients and 30 normal controls. All subjects in the study were under 71 years of age and English speaking by birth. There was no significant difference in age or education: (a) between normal and brain-da­maged groups, or (b) between the different brain-damaged groups. Damage was due to cerebro-vascular accident and all had suffered their impairment more than three months prior to the time of testing. Lateralization of the lesion was based on clinical neurological examination and electroencephalography. Patients with evidence of a bilateral lesion were excluded. There was no indication of a visual field defect in the patients studied and a suggestion of left-sided neglect in only 2 of the 19 RH patients. The normal controls had no history of brain damage or mental illness, but had sustained an injury to the back or leg. All subjects were right-handed before the lesion. Following the lesion, 16 of the 18 aphasic patients and 9 of the 11 LH non-aphasic patients were hemiplegic and were forced to use their non-preferred left hand. However, it was established in a pilot study that there was no significant difference in the maze performance of normal subjects using their preferred right, or their non-preferred left, hand. (For the U mazes, t = 1.11, d.£. = 38, p > .10, and for the T mazes, t = 70, d.£. = 38, p > .10).

Tests

Tests used were the Language Modalities Test for Aphasia (LMTA), devised by Wepman and Jones (1961), and the EPMT. The LMTA consists of stimulus response items and tell-a-story items. Stimulus response items, only, were used in this analysis. They were presented to the subject in the visual and auditory modalities. The stimulus material includes pictures, words, numbers and senten­ces; responses are speaking, writing and matching. Oral, matching and total errors were compiled for each subject in the study.

The EPMT is a visual test of scanning and planning ahead. It consists of eighteen inverted triangular lattices, represented by fine dotted lines with large black dots at some of the intersections (Figure 1). Following certain rules/ the subject must draw a line from the vertex to the top of the maze, passing through a specified number of large black dots. The usual method of scoring is the timed (T) one. The subject is allowed 1 minute per maze. If he completes the maze correctly within 30 seconds, he is given a score of 2. If he completes it within 30 to 60 seconds, he is given a score of 1. Thus, it is possible to obtain a maxi­mum score of 36. In the current study, two methods of scoring were used, the T method, described above, and an untimed (U) method, in which all subjects were allowed 4 minutes to complete each maze. A score of 1 was given for each of the 18 mazes correctly completed within that period, yielding a maximum U score of 18. A pilot study established that if a brain-damaged subject did not complete a maze within 4 minutes, he was unlikely to complete it at all.

(a) The subject must stay on the dotted lines and not cross a white space; (b) He must not go backwards, i.e. towards the vertex.

2

24 Y. M. Archibald

Fig. 1 - The EPMT.

Procedure

All subjects completed the LMTA first. The EPMT was discontinued after three successive failures.

RESULTS

Subjects were classified as aphasic or non-aphasic on the basis of their LMTA performance. Patients making more than the maximum number of total errors made by the control group of normals were classified as having language difficulties. On this basis, 18 of the 29 LH patients were judged aphasic and 6 of the 19 RH patients were judged to have mild language impairment. Table I shows the classification of patients according to their

TABLE I

Classification of Subjects as Aphasic or Nonaphasic, and With or Without Language Difficulty, on the Basis of LMTA S-R Items

Group Classification N

LH Nona phasic 11 LH Aphasic 18 RH Without language difficulty

(wold) 13 RH With language difficulty

(wid) 6 Normals 30

25 The Elithorn perceptual maze test

TABLE II

Means and Standard Deviations of EPMT Scores for T and U Conditions

Method of scoring RHwld RHwold ilL LHNA N

T vs. U Mean S.D. Mean S.D. Mean S.D. Mean S.D. Mean S.D.

Timed, max = 36 1.83 1.94 5.23 5.46 7.50 4.68 8.91 4.32 15.60 5.46

Untimed, max = 18 5.83 4.54 6.69 5.27 12.17 3.64 11.18 3.28 14.30 5.39

performance on the LMTA. Table II shows the means and standard devia­tions for the 5 groups for T and U EPMT data. T and U scores were analyzed independently by means of two separate 5 X 1 analyses of variance. The Newman Keuls test was then performed for the T and the U data, to determine differences between means for any 2 groups (viz T abies II and IV). It should be noted that T scores for the various groups were not ho~ mogeneous in variance, so that a log transformation of the T scores was made. The statistics reported for the T data are, thus, on the transformed scores.

TABLE III

Results of (a) The F Test and (b) The Newman-Keuls Analysis of EPMT T Scores (Log Transformation) for all 5 Groups

(a) F Analysis

Source of variation ss df MS F p

Treatments 5.38 4 1.35 19.79 < .01

Error 4.97 73 .07

Total 10.35 77

(b) Newman-Keuls Analysis

Treatments RHwld RHwold LH. LHNA N

Means .36 .62 .87 .94 1.20

RHwrd .36 .26* .51** .58** .84**

RHwold .62 .25* .32** .58**

LH, .87 .07 .32*

LHN. .94 .26*

N 1.20

* p < .05; ** p < .01.

26 Y. M. Archibald

TABLE IV

Results of (a) The F Test and (b) The Newman-Keuls Analysis of EPMT U Scores for all 5 Groups

(a) F Analysis

Source of variation ss df MS F p

Treatments 737.26 4 184.31 12.72 < .01

Error 1058.04 73 14.49

Total 1795.30 77

(b) Newman-Keuls Analysis

Treatments RHwld RHwold LIL IJINA N

Means 5.83 6.69 11.18 12.27 14.30

RHwld 5.83 .86 5.35** 6.34** 8.47**

RHwold 6.69 4.49** 5.48** 7.61**

IRA 11.18 .99 3.12

IJINA 12.17 2.13

N 14.30

** p < .01.

For the T data, all comparisons were significant, save one: (a) Normals were superior to both L and RH groups; (b) both LH groups were superior to both RiH groups; (c) the RH group without language difficulty was superior to the RH group with language difficulty. The non-significant comparison was between the two LH groups.

For the U data, normals were superior only to the two RH groups. They did not differ significantly from the two LH groups and, again, the LH groups did not differ from each other. Moreover, in this U condition, the two RH groups did not differ from each other. Again, the two LH groups were s:.I­perior to the two RH groups.

Thus, the major effect of increasing the time allowance for the mazes is to show that IR patients can perform as well as normals, given the extra time. Interestingly, the additional time also benefited the RH patients with language difficulty whose performance equalled that of RH patients without language difficulty in the U, but not the T, condition.

Correlations were also done between language errors and maze scores to determine whether or not language impairment affected maze perform­ance. The only significant result was a negative correlation ( =- .316, p < .05) between total language errors on the LMTA and percentage change on

27 The Elithorn perceptual maze test

the mazes. The percentage change score was derived by computing, for each subject, the percentage correct score for the T and the U maze condition, then subtracting the T from the U percentage. The significant negative cor­relation suggestes that patients with a greater degree of aphasia make more improvement on the mazes from the T to the U condition.

One feature of the mazes is that, in general, the more difficult the maze, the greater the number of dots which have to be processed for solution. Accordingly, a comparison was made between R and LH groups in terms of the maximum number of dots they were able to process for solution. The results, shown in Table V, demonstrate that whether or not time is limited, RH patients are able to process fewer dots than LH patients.

TABLE V

Mean Scores and "t" Values for the Difference between Means of L and RH Groups for the Maximum Number of Dots Processed

Condition Mean LH Mean RH d£ p

T 9.76 6.47 3.82 46 > .001

u 13.00 9.00 3.88 46 > .001

In summary, then, normals were superior to LH groups within the T but not the U condition. Normal and LH groups were superior to RH groups under both T and U conditions. The RH group without language difficulty was superior to the RH group with language difficulty in the T, but not the U, condition. The two LH groups did not differ from each other at all. There was a significant negative correlation only within the LH group be­tween the total number of errors on the language test and percentage change from T to U conditions on the maze test. Finally, RH patients were able to process significantly fewer dots for maze solution than LH patients.

DISCUSSION

Normal and left hemisphere groups

LH groups are inferior to normals in maze performance when the task is timed. There is, however, a striking lack of difference between LH and normal groups in the U condition. Thus, the maze data demonstrate that, while LH patients are slower than normals, the task itself can, nevertheless, be processed by them, albeit less efficiently.

In attempting to explain why LH patients are slower than normals on

28 Y. M. Archibald

the maze task, it is useful to look at functions which are dependent on the L hemisphere. Aside from language, which will be considered later, the most salient disturbance seen after LH damage is apraxia, i.e., impairment in the ability to execute everyday, well-practised motor acts. Kimura and Archi­bald ( 197 4) showed that LH patients were impaired, relative to RH patients, on a task in which they copied unfamiliar movement sequences of the hands, as well as on traditional tests of apraxia. This was true of the hand ipsilateral to the lesion, as well as the contralateral hand, when hemiplegia did not preclude testing. On the basis of this and other evidence, Kimura (1975) has suggested that the LH is specialized for the control of motor sequencing.

There is also evidence to suggest that the LH is specialized in processing visual-spatial material sequentially. Butters and Soeldner (1972), using the Money Road Map Test, which consists of a sequence of 32 left or right turns in a variety of orientations to the body, found that patients with left frontal impairment made the largest mean number of errors (11.9). Surpri­singly, they made about twice as many as patients with right parietal impairment.

While the Elithorn Maze Task is highly visual-spatial in nature, solution also involves sequential processing, both visual and motor. Search for the correct pathway entails selecting the correct sequence of turns, then drawing it with a pencil. The slower performance of LH patients, compared with normals, might be explained, in part at least, by impairment in sequential processing. By taking more time, they are able to compensate for such im­pairment. In addition, their presumably intact visual-spatial processes would contribute to their success.

A further consideration in explaining the slower performance of the LH group is speed of execution of the task. Wyke (1967) found decreased speed of movement in a simple reaction time task for both the ipsilateral and contralateral hands, in patients with lesions of the L, but not the R, H. While the maze task does not easily allow separation of execution time from total response time, and while it was demortstrated in a pilot study that there is no difference in maze scores for normals using their preferr~d or non­preferred hand, slower execution time for LH than normal and RH patients remains a possibility.

Since one of the LH groups in the maze study was aphasic, it is pertinent to determine whether their language impairment affected their maze per­formance. The fact that solution of the mazes involves counting dots, as many as 16 in the more complex ones, indicates that there is a verbal se­quential component to the maze task. It was observed that LH patients, especially aphasics, frequently miscounted the dots, resulting in increased time to solution. The significant correlation between total errors on the LMTA and percentage change in maze score from the T to U condition, within the LH group, suggests that language impairment reduces speed of perform­

29 The Elithorn perceptual maze test

ance. The effect of language impairment on the maze task is, however, fairly subtle, since it does not result in a difference between the LH aphasic and LH nonaphasic groups in either the T or U conditions. The inferior perform­ance of both LH aphasic and nonaphasic groups to N's in the T condition indicates that non-verbal sequential processes contribute more than verbal (sequential) processes to reduced speed of performance.

Comparison of normal and LH groups with RH groups

The finding that RH patients are inferior to LH patients on the maze task supports that of Colonna and Faglioni (1966 ), using the original, rec­tangular version of the test under the T condition. These authors sub­sequently adjusted their maze data for visual reaction times, which were slower in the RH group, nullifying the hemisphere difference. The present study, however, demonstrates the inferiority of the R to the LH group under an U, as well as aT, condition. This unequivocal deficit of the RH patients is consistent with a growing body of evidence for RH superiority in pro­cessing visual-spatial material (Dimond, 1972). More specifically, such deficit on the EMPT is comparable to that found by Milner (1965) and Newcombe (1969) on a visually guided maze learning task. In addition, Corkin's data ( 1965) suggest that the spatial deficit may not be confined to the visual modality. The Elithorn maze data are also consistent with data for RH supe­riority for fundamental visual processes, such as perception of line orientation (Kimura and Durnford, 1974) and dot enumeration (Kimura, 1963; Warring­ton and James, 1967). While the exposure time for dot enumerations is limited to milliseconds, in contrast to the maximum of 4 minutes allowed on the EPMT, the maze data suggest that the RH is more limited than the L in the number of dots it can process. Owing to the complexity of the mazes, the relative importance of sp.atial as opposed to visual components, and their interaction, cannot be assessed.

RH groups

While there is no difference between the RH groups with and without language difficulty in the U condition, the group with language difficulty is inferior to that without language difficulty in the T condition. It may well be that their mild language impairment contributes to reduced efficiency in the T condition. Even so, the performance of both RH groups in the U condition is still notably inferior to that of LH and normal groups.

Study of the mazes under T and U conditions shows the brain-damaged patients are slower than N's. The data suggest, however, that there are specific features of the task which dissociate R and LH damaged groups; on the one hand, the visual and spatial features and, on the other hand, the sequential feature of locating the sequence of turns and tracing the correct

30 Y. M. Archibald

pathway. The predominant visual and spatial features so impede the RH group that they are inferior to LH and N groups under both T and U con­ditions. The less dominant sequential feature appears to impede the LH group, but only when the maze task is T. In addition, the fact that aphasic patients make more improvement than nonaphasic patients on the mazes from the T to the U condition suggests that language impairment has a mildly adverse effect on maze performance. This observation gains further support from the finding that RH paitents with language difficulty are inferior on the mazes to RH patients without language difficulty. Normal subjects, on the other hand, without impairment in visual-spatial processing, sequencing or language, are able to perform more efficiently than the other groups. The maze data do not, then, support the notion of non-specific deficit in brain­injured patients. On the contrary, they provide additional evidence for asym­metry of hemisphere functioning.

SuMMARY

Eighteen LH aphasic patients, 11 LH nonaphasic patients, 19 RH patients and 30 normal controls were compared on the Elithorn Perceptual Maze Test (EPMT) under both timed (T) and untimed (U) conditions. Results show that (a) normals were superior to LH groups within the T, but not the U, condition; (b) normal and LH groups were superior to RH groups under both T and U conditions; (c) the 2 LH groups did not differ from each other and (d) the RH group without language difficulty was superior to the RH group with language difficulty in the T, but not the U, condition. Additional findings were that (a) RH patients were able to process significantly fewer dots for maze solution than LH patients, (b) the more aphasic the patient, the more he improved his score from the T to the U condition. The data were discussed in terms of differential processing in R and LH groups, the RH groups being more likely to be impeded by the visual and spatial features of the task, the LH groups by the language and sequencing features.

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Dr. Yvonne M. Archibald, Clinical Neurosciences, Victoria Hospital, 375 South Street, London, Ontario, N6A 4G5, Canada.