Tests and Procedures

Two memory tests, each consisting of a verbal and a nonverbal portion, were employed.

Test 1A (verbal portion: story recall). A short paragraph was read to the subject (6). Patients with identical dysfunction of the left temporal lobe are known to perform more poorly on this test than patients with dysfunction of the frontal parietal or right temporal region (22). Immediately after hearing the story, and again the next day (16-19 hours later), subjects were asked to recall as much as they could remember of it. The paragraph was divided into 20 segments, and the score was the number of segments recalled. Eighteen patients receiving bilateral ECT and 13 receiving right unilateral ECT were tested before treatment and again, with an equivalent form of the test, 6-10 hours after the fifth treatment of the series.

Test 1B (nonverbal portion: memory for geometric figure). Subjects copied a complex geometrical design (the Rey-Osterrieth figure [23] or the Taylor figure [24] and were then asked to reproduce it from memory 16-19 hours later. Patients with right temporal lesions are known to be deficient on this task, whereas patients with left temporal lesions exhibit no impairment (25). The score for this test depended on the number of properly placed line segments (maximum score=36 points). The same patients given test 1A (above) were tested with one of these figures before ECT and with the other ones 6-10 hours after the fifth treatment.

Test 2A (verbal portion: short-term memory distractor test). Subjects were shown a consonant trigram, distracted for a variable interval (0, 3, 9 or 18 seconds), and then asked to recall the consonants (26). Patients with left temporal lesions are impaired on this task; patients with right temporal lesions are not (27). Subjects received 8 trials at each retention interval, and their score was the number of consonants correctly recalled without regard to order. The maximum score was 24. Fifteen patients receiving bilateral ECT were tested on two occasions with equivalent forms of this test. These sessions were scheduled 2-3 hours after the first treatment and 2-3 hours after the third treatment in the series. In addition, 8 patients receiving right unilateral ECT were tested 2-3 hours after their first and third treatments. Finally, 18 patients were tested on one occasion 1-2 days before their first treatment.

Test 2B (nonverbal portion: spatial memory). subjects attempted to remember the position of a small circle located along an 8-inch horizontal line. Patients with right temporal lesions are impaired on this task; patients with left temporal lesions are not (27). subjects inspected the circle on the line for 2 seconds and then were distracted for 6, 12 or 24 seconds by arranging strings of random digits into numerical order. Then subjects attempted to mark on a different 8-inch line the remembered position of the circle. Twenty-four trials were given, with 8 at each of the three retention intervals. The score on each trial was the distance (in millimeters) between the position of the originally presented circle and the position of the circle as marked by the subject. The score on the test at each retention interval was the total error (in millimeters) for all 8 trials. Test 2B was given on the same occasions and to the same patients as test 2A (above).

Results

Figure 1 shows the results with test 1 for patients who received bilateral or unilateral ECT. Before ECT these two groups of patients did not differ from each other on any of the measures of immediate or delayed recall (for the verbal test t.10; for the nonverbal test, t=0.7, p>.10). After ECT patients receiving bilateral treatment were able to remember verbal material immediately after hearing it as well as they could before ECT (before ECT versus after ECT, t=0.1, p>.10), and they were able to copy a complex figure as well as before ECT (t=0.1, p>.10). However, their performance was severely impaired on delayed tests of verbal and nonverbal memory (verbal test: before ECT versus after ECT, t=5.6, p<0,1; nonverbal test: before ECT versus after ECT, t=3.7, p<0.1).

Right unilateral ECT did not affect verbal memory, as measured by test 1A. That is, the delayed recall scores of patients receiving right unilateral treatment were about the same after ECT as before (t=0.6, p>.10). However, nonverbal memory was significantly impaired by right unilateral ECT (test 1B). Before unilateral ECT the score for reproducing the geometric figure after a delay was 11.9, and after unilateral ECT the corresponding score was 7.1 (t=2.7, p<.05). This impairment in nonverbal memory associated with unilateral ECT was not as great as the impairment in nonverbal memory associated with bilateral ECT (t=2.1, p<.05).

Figure 2 shows the results with test 2 for patients receiving bilateral ECT, patients receiving right unilateral ECT, and a control group of patients about to begin a course of bilateral or unilateral ECT. For the short-term memory distractor test, patients receiving bilateral ECT were impaired, but patients receiving right unilateral ECT performed normally. An analysis of variance with repeated measure on one factor (28) indicated that the scores of bilateral patients were significantly lower than those of both unilateral patients (F=10.8, p<.01) and control patients (F=5.7, p,10).

For the spatial memory test bilateral ECT also produced a marked impairment (bilateral group versus control group, F=22.4, p<.01). The scores of unilateral patients were also poorer than those of control patients, although this difference fell short of significance (F=2.64, p=.12). Finally, the effect on nonverbal memory associated with unilateral ECT was not as great as the effect associated with bilateral ECT (F=9.6, p<.01).