Digit span in right and left hemiplegics

Abstract

PROBLEV A recent study(4) failed to report differences in digit span between braindamaged and non-brain-damaged cases. This may be due t o failure t o take into account side of lesion and intra-hemisphere differences related to difficulties in visual tasks. Although the digit span test is primarily auditory, a number of observations suggest the role of visual imagery, particularly with regard t o digits backward: (1) We have noticed that left hemiplegics with visual problems falter on the backward digits relative to the forward digits.(2) Phenomenologically, the reader is invited to introspect on his own imagery if asked to spell a long word backward, e.g., Washington. (3) One can observe the eye movement of a colleague when presented with forward and backward versions of the task. METHODThe digit span test was administered to 45 left hemiplegics (LIL), 33 right hemiplegics (RHs), and two control groups of normals of high education (CI) (N = 14) and low education (Cz) (N = 24). The groups of hemiplegics were similar in education to C1. The mean age of all groups was in the 60s. The hemiplegic groups were subdivided further on the basis of two or more errors on a visual confrontation task") into those with one or no errors (LHl and RH1) and those with 2 or more errors (LH2 and RHz). RESULTS On Digits Forward, there were no differences among LH1, LHz and GI. All are superior to C2, RHI, RH2 ( p < .05). On Digits Backward, C1 and LH1 are superior to LHZ and Cz, which are superior t o RHI, RHz ( p < .01). For those who scored 6 digits or more on DF, DF-DB yields an average difference score of 3 digits for LH2 and only 2 digits for LH1 and C1. These differences are significant by Mann-Whitney U Test ( p < .01). CONCLUSIONSRHs respond like less educated people on both forward and backward digits. The marked inability of the LH (errors on visual confrontation) to perform on Digits Backward even though they perform normally on Digits Forward is associated with difficulty in visual scanning and possibly eye movements. This view is in accord with that of Hebb(3) and Ewert(2) on the role of visual scanning and memory. I n neuropsychology, it commonly is suggested that verbal factors influence seemingly spatial tasks because of the role of inner language or self-rehearsal. Here we are suggesting a reverse effect. The role of visual scanning in verbal tasks also has clinical importance. It is common to evaluate short term memory by combining Digits Forward and Digits Backward into a composite score, but this practice might obscure important differences. REFERENCES 1. DENNY-BROWN, D. Handbook of Neurological Ezaminatia and Case Recording. Cambridge: 2.3. HEBB, D. 0. 6oncerning imagery. Psychol. Rev., 1968, 75, 466-477. 4. Harvard University Press, 1967 EWERT, H. E e movement during reading and recall. J . Ben. Psychol., 1933, 8, 65-84. STERNE, D. M. The Benton, Porteus and WAIS digit span tests with normals and brain injured subjects.

Clinical utility of considering Digits Forward and Digits Backward as separate components of the wechsler adult intelligence Scale-Revised

“…Ostensibly, repetition of digits backward and Progressive Matrices reasoning more complexly involves use of visual-spatial loaded codes than in forward digit span repetition. This contention is in agreement with Weinberg et al (1972) and , who indicate that Backward Digit Span employs usage of visual representations, and with Gardner (198 l), who indicated that repetition of digits forward to a much lesser degree involves cognitively manipulating components of digit span into visual engrams or codes.…”

Digits forward and digits backward as two separate tests: Normative data on 1567 school children

“…Those with predominantly left-sided neurological signs (indicative of right hemisphere dysfunction) characteristically did worse on Digits Backward. Weinberg et al (1972) came to similar conclusions after administering the two Digit Span sections to right and left sided adult hemisplegics. Thirty percent of Rudel and Denckla's subjects exhibited a difference of three or more between Digits Forward and Backward -giving support to the commonly held view that a differential of this magnitude is strongly suggestive of organic disease of the brain.…”

“…Sattler makes reference to the visualization of the digits (an issue that I will discuss subsequently) but does not differentiate between the two sections of the test with regard to this element. Weinberg, Diller, Gerstman, & Schulman (1972) and Lezak (1976) make specific reference to the internal visual scanning operation in the Digits Backward section of the subtest. Lezak describes, as well, the "feat of mental doubletracking" involved in the Digit Backward section, i.e., the subject must scan the sequence both forward and backward in order to perform the task.…”

Keeping an eye on serial order: Ocular movements bind space and time

“…Indeed, while previous studies have shown that covert spatial attention is engaged in accessing the serial representation, there is no direct proof of sensorimotor changes in overt orienting during serial processing. This is an important omission, since earlier reports already suggested a possible involvement of spontaneous oculomotor strategies in the processing of ordered verbal information (Robertson, 1990;Weinberg, Diller, Gerstman, & Schulman, 1972). In the present study, we therefore hypothesized that the scanning of a serial representation would be accompanied by spontaneous eye movements.…”

“…Indeed, visuospatial strategies can be often adopted to solve pure verbal tasks (Robertson, 1990;Weinberg et al, 1972). In particular, representing visually the memorized ordered sequence might be a helpful strategy to store and manipulate the ordered information.…”