- Email: [email protected]
Procedural memory in schizophrenia assessed using a mirror reading task
Psychiatry Research 109 (2002) 303–307
Brief report
Procedural memory in schizophrenia assessed using a mirror reading task Kazuko Takanoa,b,*, Mitsuhiro Itoa,c, Koji Kobayashia, Natsumi Sonobea, Sadatoshi Kurosua, Yukiko Moria, Satoshi Takeuchia, Mitsuo Uchiyamaa, Masahiro Kannoa, Shin-Ichi Niwaa a
Department of Neuropsychiatry, School of Medicine, Fukushima Medical University, 1 Hikarigaoka, Fukushima-City, Fukushima 960-1295, Japan b Shounan Hospital, Sukagawa City, Fukushima 962-0403, Japan c Ichiyokai Hospital, 15-27 Yashima-Cho, Fukushima City, Fukushima 960-8136, Japan Received 24 November 1999; received in revised form 20 June 2001; accepted 16 August 2001
Abstract The preservation of procedural memory in individuals with schizophrenia has been confirmed by methods such as the Tower of Hanoi, pursuit rotor and mirror reading tests. However, the cognitive procedural memory of Japanese subjects with schizophrenia has never been assessed using mirror reading. To better determine the characteristics of cognitive procedural memory in schizophrenia, a Japanese version of the mirror reading task, consisting of cards with words written in Japanese katakana characters in mirror image, was administered to 18 Japanese patients with schizophrenia and 21 normal controls. The results indicated that the patients indeed learned the skill despite exhibiting lower overall performances in reading time than the controls, their scores displaying correlation with the severity of schizophrenic negative symptoms. This suggests that procedural memory for this task is retained in individuals with schizophrenia. It is important for them to use their preserved procedural memory for efficient rehabilitative efforts. 䊚 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Procedural memory; Skill learning; Rehabilitation; Negative symptoms
1. Introduction Memory disorders have been recognized in schizophrenia for some time (Manschreck et al., 1991; McClain, 1983). Out of several characteristic disorders already reported, numerous articles have examined impairment in declarative memory, which is retained by verbal means. Recent research *Corresponding author. Present address: Futaba-Kohsei Hospital, 100 Kubomae, Niyama, Futaba-Machi, Futaba-Gun, Fukushima 979-1472, Japan. Tel.: q81-240-332-151; fax: q 81-240-332-129. E-mail address: [email protected] (K. Takano).
in schizophrenia has also shown impairment in declarative memory, with a greater degree of disturbance in recall than in recognition (Goldberg et al., 1989). Furthermore, Corrigan et al. (1992) suggested some correlation between the degree of skill acquisition through social skill training (SST) and performance of declarative memory. Detailed study of this disturbance has revealed that memory plays an important part in acquisition of the social skills necessary for rehabilitation. By contrast, there has been a relatively small amount of research on non-declarative memory
0165-1781/02/$ - see front matter 䊚 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 1 6 5 - 1 7 8 1 Ž 0 2 . 0 0 0 2 1 - 5
304
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
skills. Non-declarative procedural memory appears to be preserved in individuals with schizophrenia as assessed by tests such as the Tower of Hanoi and pursuit rotor (Goldberg et al., 1990; Schwartz et al., 1996; Schmand et al., 1992). In addition, Clare et al. (1993) reported similar results using pursuit rotor, jigsaw puzzle assembly, and mirror reading tasks. In that report, however, only eight patients performed the mirror reading task, and no studies to date have confirmed preservation of procedural memory in subjects with schizophrenia using mirror reading of Japanese script. Also, no past reports have considered learning speed or symptoms. Wykes et al. (1999) compared conventional occupational therapy and alternative therapy involving repetitive practice of cognitive tasks by patients with the necessary strategy explained to them. In the Wisconsin Card Sorting Test (WCST), Digit Span, and Six Elements tasks, the cognitive task therapy group displayed marked improvement in the Rosenberg Self-Esteem Schedule. It was concluded from this result that cognitive task therapy possibly reduces the degree of cognitive impairment and time necessary for patients to return to society. SST is applied widely in rehabilitation of schizophrenic patients. In this program, the patients learn communication and daily skills through repetition. Procedural memory is thought to play a considerable role in such a program. For effective application of SST, it is important to consider how to evaluate the function of procedural memory of schizophrenic patients and how the learning speed and performance achieved relate to the symptoms. In this report, therefore, the following investigation was performed to better determine the characteristics of cognitive procedural memory. In the past, mirror reading tasks were carried out using English words consisting of the Roman alphabet. We employed katakana mirror reading to apply this task to native Japanese speakers. A Japanese version of the mirror reading task was administered to individuals with schizophrenia and normal controls in order to confirm the preservation of procedural memory. The first purpose was to determine the difference in the degree of learning between the patients and controls. The second
purpose was to determine how the patients’ learning speed and performance related to symptoms. 2. Subjects and methods 2.1. Subjects Subjects included 18 patients (8 males, 10 females; 14 inpatients, 4 outpatients) meeting the DSM-III-R (American Psychiatric Association, 1987) diagnostic criteria for schizophrenia and 21 (12 male, 9 female) normal controls. A clinical psychiatrist without any knowledge of the results of this study made diagnoses of schizophrenia by clinical interviews, reviews of medical and social histories, and psychiatric examinations. Patients with organic brain dysfunction, mental retardation, abnormalities on a neurological examination, or histories of drug dependence were excluded. Control subjects were physically and mentally healthy volunteers, recruited from relatives of the staff at the Shounan Hospital and the Fukushima Medical College Hospital. None of the subjects, including the patients, had prior experience with mirror reading tasks. They were all native Japanese speakers. The average ages of the patients and normal controls were 36.0 (S.D.s8.5) and 37.7 (S.D.s 15.1) years old, respectively. The average years of education of the patients and normal controls were 10.8 (S.D.s1.9) and 12.9 (S.D.s3.1). The subjects with schizophrenia were all chronic patients who had been diagnosed for over 6 months, the average duration of illness being 14.3 (S.D.s 10.8) years. All of the individuals with schizophrenia were also receiving antipsychotic medication; their mean neuroleptic dosage in haloperidol-equivalent dose was 16.6 (S.D.s8.6) mg per day. Additionally, 16 of the patients were on concomitant anticholinergic drugs and 11 patients were receiving benzodiazepines (diazepam 3.3–20 mgyday). To exclude subjects with dementia, the Mini Mental State Examination (MMSE, Folstein et al., 1975) was administered by the aforementioned psychiatrist. None of the subjects were diagnosed as having dementia, all of them scoring above 23 on the MMSE. At baseline, the psychiatric symptoms of those with schizophrenia were
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
305
ment rate was defined as reading time required for session 1 minus that for session 2, divided by the reading time for session 1, and then converted to percentage. The studies were done using SPSS for Macintosh. 3. Results 3.1. Reading time for schizophrenic and control subjects Fig. 1. Example of mirror reading card.
evaluated by the psychiatrist using the Positive and Negative Syndrome Scale (PANSS, Kay et al., 1991). The average positive and negative symptom scores were 14.5 (S.D.s6.5) and 16.8 (S.D.s 5.1), respectively, and the average global psychopathological symptom score was 32.3 (S.D.s 10.3). The purpose and methods of the study were explained to each subject who then gave written informed consent to participate. 2.2. Methods Three words were written in Japanese katakana characters with left-right reversal on a card (Fig. 1). We chose 240 words randomly out of the ‘rare’ section of a classified vocabulary table (National Language Research Institute, 1964) and listed them in a random order. Every word had a meaning and consisted of four to nine characters each. The subjects were then asked to read each word as quickly and accurately as possible. Each test session consisted of four blocks of 10 cards each. After two weeks, subjects participated in one more session consisting of different words. The reading time for each card for each subject was measured using a stopwatch, and it was added to provide total reading time for the session. In order to test the reliability of using a stopwatch for this kind of experiment, a reliability test was carried out. Rounding off the examiners’ respective times for the test to the nearest second yielded the same result. On the basis of this, we judged the use of a stopwatch as reliable. In the next step, to assess the retention of procedural memory, we examined the improvement rate of reading time. An improve-
The average reading time from sessions 1 and 2, respectively, were: 414 (S.D.s142) and 336 (S.D.s83) seconds for the control group; 554 (S.D.s225) and 460 (S.D.s174) seconds for the schizophrenic group (Fig. 2). To examine the effects of session and subject, we employed subject and session as independent variables and reading time as a dependant variable in repeated measures ANOVA (Table 1). As a result, the main effect of subject was significant (Fs6.44, d.f.s1, P0.02), and the reading time of schizophrenia patients was longer than that of normal controls. The main effect of session was also significant (Fs24.04, d.f.s1, P-0.001), as the reading time for session 2 was shorter than that for session 1. The interaction of session and subject, on the other hand, was not significant. From this result, we deduce that the learning effects seen in schizophrenic patients rank with those of normal controls. 3.2. Relationship between performance on mirror reading task and clinical symptoms of individuals with schizophrenia Correlation coefficients between the reading time and clinical symptom scores are displayed in Table 2. There was a marked correlation between the reading time in sessions 1 and 2 and the negative symptom scores on the PANSS. By contrast, no notable correlation could be detected between the reading time and positive symptom scores. We also examined relationships between the improvement rate of reading time and psychiatric symptoms. The average improvement rate of schizophrenics was 13.8 (S.D.s17.1)%. No signifi-
306
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
Fig. 2. Reading time of each session in mirror reading task.
rotor tests (Schwartz et al., 1996; Schmand et al., 1992; Goldberg et al., 1990). Also, Clare et al. reported that individuals with schizophrenia could indeed learn the mirror reading task despite exhibiting lower completion performance than healthy controls. In the present study using Japanese characters, the schizophrenic group likewise required longer reading time than the control group did, but the patients showed the same rate of improvement, indicating that the two groups had equal speeds of learning this task. This finding confirms the results of earlier studies that procedural memory is retained in schizophrenia. Schmand et al. reported no notable correlation between schizophrenic symptoms and Tower of Hanoi test results (Schmand et al., 1992). Clare et al. examined schizophrenia patients using a mirror reading task but did not investigate the relation
cant correlation was found between the improvement rate and scores of the PANSS (positive symptoms, rs0.186, P)0.05; negative symptoms, rsy0.115, Ps0.66; total symptoms, rsy0.09, Ps0.74). 4. Discussion This study demonstrates that: (1) although individuals with schizophrenia exhibit reading performances inferior to those of healthy controls on the Japanese mirror reading task, they do have the ability to learn procedural memory; (2) reading time for the mirror reading task is related to the severity of the each patient’s negative symptoms. In the past, procedural memory was shown to be preserved in individuals with schizophrenia by methods such as the Tower of Hanoi and pursuit Table 1 ANOVA table
Main effect Subject Repeated session Interaction effect Subject by session
Sums of squares
Degree of freedom
Mean square
F
337944.80 145004.34
1 1
337944.80 145004.34
6.44* 24.04**
1373.11
1
1373.11
Subjects are repeated as independent variables and reading time as a dependent variable in repeated measures ANOVA. * P-0.05. ** P-0.01.
0.23
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
307
Table 2 Correlation between mirror reading time and clinical symptoms scores for subjects with schizophrenia PANSS
Session 1 reading time
Session 2 reading time
Positive symptoms score Negative symptoms score Total score
0.27 0.53* 0.38
0.18 0.67** 0.48*
Values are Pearson product-moment correlation coefficients between reading time and clinical symptom scores. * P-0.05. ** P-0.01.
between symptoms and task performance (Clare et al., 1993). The present study indicates a strong correlation between the overall mirror reading task completion performance and negative symptoms, while showing no relationship between the performance improvement rates and negative symptoms. This suggests that negative symptoms in schizophrenia have a considerable influence on the level of mirror reading performance ultimately achieved, but not on the learning speed. This finding means that procedural memory can be used to acquire skills and promote the return of schizophrenic patients to society. These results provide a powerful rationale for rehabilitation training. SST is an approach to rehabilitation designed for schizophrenic patients to gain communication techniques required in daily life and social skills necessary for independence. In SST, patients practice social skills through behavior therapy such as role plays and feedback. Procedural memory is considered to contribute to the acquisition of skills through such training. Schizophrenic patients have been shown to acquire social skills through SST. Also, a report indicates some correlation between completion performance and verbal memory (Corrigan et al., 1992). However, there have been no indications of correlations between learning speed and verbal memory. In actuality, even patients with unsatisfactory verbal memory performance acquire skills through SST, indicating skill acquisition by procedural memory as well. We have not explored the relationship between the procedural memory and skill acquisition through SST by schizophrenic patients, but it is a topic for future study.
References Clare, L., McKenna, P.J., Mortimer, A.M., Baddeley, A.D., 1993. Memory in schizophrenia: what is impaired and what is preserved? Neuropsychologia 31, 1225–1241. Corrigan, P.W., Wallace, C.J., Green, M.F., 1992. Deficits in social schemata in schizophrenia. Schizophrenia Research 8, 129–135. Folstein, M.F., Folstein, S.E., McHugh, P.R., 1975. MiniMental State: a practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research 12, 189–198. Goldberg, T.E., Weinberger, D.R., Pliskin, N.H., Berman, K.F., Podd, M.H., 1989. Recall memory deficit in schizophrenia. A possible manifestation of prefrontal dysfunction. Schizophrenia Research 2, 251–257. Goldberg, T.E., Saint, C.J.A., Weinberger, D.R., 1990. Assessment of procedural learning and problem solving in schizophrenic patients by Tower of Hanoi type tasks. Journal of Neuropsychiatry and Clinical Neurosciences 2, 165–173. Kay, S.R., Opler, L.A., Spitzer, R.L., Williams, J.B., Fiszbein, A., Gorelick, A., 1991. SCID-PANSS: two-tier diagnostic system for psychotic disorders. Comprehensive Psychiatry 32, 355–361. Manschreck, T.C., Maher, B.A., Rosenthal, J.E., Berner, J., 1991. Reduced primacy and related features in schizophrenia. Schizophrenia Research 5, 35–41. McClain, L., 1983. Encoding and retrieval in schizophrenics’ free recall. Journal of Nervous and Mental Disease 171, 471–479. Schmand, B., Brand, N., Kuipers, T., 1992. Procedural learning of cognitive and motor skills in psychotic patients. Schizophrenia Research 8, 157–170. Schwartz, B.L., Rosse, R.B., Veazey, C., Deutsch, S.I., 1996. Impaired motor skill learning in schizophrenia: implications for corticostriatal dysfunction. Biological Psychiatry 39, 241–248. Wykes, T., Reeder, C., Corner, J., Williams, C., Everitt, B., 1999. The effects of neurocognitive remediation on executive processing in patients with schizophrenia. Schizophrenia Bulletin 25, 291–306.
Brief report
Procedural memory in schizophrenia assessed using a mirror reading task Kazuko Takanoa,b,*, Mitsuhiro Itoa,c, Koji Kobayashia, Natsumi Sonobea, Sadatoshi Kurosua, Yukiko Moria, Satoshi Takeuchia, Mitsuo Uchiyamaa, Masahiro Kannoa, Shin-Ichi Niwaa a
Department of Neuropsychiatry, School of Medicine, Fukushima Medical University, 1 Hikarigaoka, Fukushima-City, Fukushima 960-1295, Japan b Shounan Hospital, Sukagawa City, Fukushima 962-0403, Japan c Ichiyokai Hospital, 15-27 Yashima-Cho, Fukushima City, Fukushima 960-8136, Japan Received 24 November 1999; received in revised form 20 June 2001; accepted 16 August 2001
Abstract The preservation of procedural memory in individuals with schizophrenia has been confirmed by methods such as the Tower of Hanoi, pursuit rotor and mirror reading tests. However, the cognitive procedural memory of Japanese subjects with schizophrenia has never been assessed using mirror reading. To better determine the characteristics of cognitive procedural memory in schizophrenia, a Japanese version of the mirror reading task, consisting of cards with words written in Japanese katakana characters in mirror image, was administered to 18 Japanese patients with schizophrenia and 21 normal controls. The results indicated that the patients indeed learned the skill despite exhibiting lower overall performances in reading time than the controls, their scores displaying correlation with the severity of schizophrenic negative symptoms. This suggests that procedural memory for this task is retained in individuals with schizophrenia. It is important for them to use their preserved procedural memory for efficient rehabilitative efforts. 䊚 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Procedural memory; Skill learning; Rehabilitation; Negative symptoms
1. Introduction Memory disorders have been recognized in schizophrenia for some time (Manschreck et al., 1991; McClain, 1983). Out of several characteristic disorders already reported, numerous articles have examined impairment in declarative memory, which is retained by verbal means. Recent research *Corresponding author. Present address: Futaba-Kohsei Hospital, 100 Kubomae, Niyama, Futaba-Machi, Futaba-Gun, Fukushima 979-1472, Japan. Tel.: q81-240-332-151; fax: q 81-240-332-129. E-mail address: [email protected] (K. Takano).
in schizophrenia has also shown impairment in declarative memory, with a greater degree of disturbance in recall than in recognition (Goldberg et al., 1989). Furthermore, Corrigan et al. (1992) suggested some correlation between the degree of skill acquisition through social skill training (SST) and performance of declarative memory. Detailed study of this disturbance has revealed that memory plays an important part in acquisition of the social skills necessary for rehabilitation. By contrast, there has been a relatively small amount of research on non-declarative memory
0165-1781/02/$ - see front matter 䊚 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 1 6 5 - 1 7 8 1 Ž 0 2 . 0 0 0 2 1 - 5
304
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
skills. Non-declarative procedural memory appears to be preserved in individuals with schizophrenia as assessed by tests such as the Tower of Hanoi and pursuit rotor (Goldberg et al., 1990; Schwartz et al., 1996; Schmand et al., 1992). In addition, Clare et al. (1993) reported similar results using pursuit rotor, jigsaw puzzle assembly, and mirror reading tasks. In that report, however, only eight patients performed the mirror reading task, and no studies to date have confirmed preservation of procedural memory in subjects with schizophrenia using mirror reading of Japanese script. Also, no past reports have considered learning speed or symptoms. Wykes et al. (1999) compared conventional occupational therapy and alternative therapy involving repetitive practice of cognitive tasks by patients with the necessary strategy explained to them. In the Wisconsin Card Sorting Test (WCST), Digit Span, and Six Elements tasks, the cognitive task therapy group displayed marked improvement in the Rosenberg Self-Esteem Schedule. It was concluded from this result that cognitive task therapy possibly reduces the degree of cognitive impairment and time necessary for patients to return to society. SST is applied widely in rehabilitation of schizophrenic patients. In this program, the patients learn communication and daily skills through repetition. Procedural memory is thought to play a considerable role in such a program. For effective application of SST, it is important to consider how to evaluate the function of procedural memory of schizophrenic patients and how the learning speed and performance achieved relate to the symptoms. In this report, therefore, the following investigation was performed to better determine the characteristics of cognitive procedural memory. In the past, mirror reading tasks were carried out using English words consisting of the Roman alphabet. We employed katakana mirror reading to apply this task to native Japanese speakers. A Japanese version of the mirror reading task was administered to individuals with schizophrenia and normal controls in order to confirm the preservation of procedural memory. The first purpose was to determine the difference in the degree of learning between the patients and controls. The second
purpose was to determine how the patients’ learning speed and performance related to symptoms. 2. Subjects and methods 2.1. Subjects Subjects included 18 patients (8 males, 10 females; 14 inpatients, 4 outpatients) meeting the DSM-III-R (American Psychiatric Association, 1987) diagnostic criteria for schizophrenia and 21 (12 male, 9 female) normal controls. A clinical psychiatrist without any knowledge of the results of this study made diagnoses of schizophrenia by clinical interviews, reviews of medical and social histories, and psychiatric examinations. Patients with organic brain dysfunction, mental retardation, abnormalities on a neurological examination, or histories of drug dependence were excluded. Control subjects were physically and mentally healthy volunteers, recruited from relatives of the staff at the Shounan Hospital and the Fukushima Medical College Hospital. None of the subjects, including the patients, had prior experience with mirror reading tasks. They were all native Japanese speakers. The average ages of the patients and normal controls were 36.0 (S.D.s8.5) and 37.7 (S.D.s 15.1) years old, respectively. The average years of education of the patients and normal controls were 10.8 (S.D.s1.9) and 12.9 (S.D.s3.1). The subjects with schizophrenia were all chronic patients who had been diagnosed for over 6 months, the average duration of illness being 14.3 (S.D.s 10.8) years. All of the individuals with schizophrenia were also receiving antipsychotic medication; their mean neuroleptic dosage in haloperidol-equivalent dose was 16.6 (S.D.s8.6) mg per day. Additionally, 16 of the patients were on concomitant anticholinergic drugs and 11 patients were receiving benzodiazepines (diazepam 3.3–20 mgyday). To exclude subjects with dementia, the Mini Mental State Examination (MMSE, Folstein et al., 1975) was administered by the aforementioned psychiatrist. None of the subjects were diagnosed as having dementia, all of them scoring above 23 on the MMSE. At baseline, the psychiatric symptoms of those with schizophrenia were
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
305
ment rate was defined as reading time required for session 1 minus that for session 2, divided by the reading time for session 1, and then converted to percentage. The studies were done using SPSS for Macintosh. 3. Results 3.1. Reading time for schizophrenic and control subjects Fig. 1. Example of mirror reading card.
evaluated by the psychiatrist using the Positive and Negative Syndrome Scale (PANSS, Kay et al., 1991). The average positive and negative symptom scores were 14.5 (S.D.s6.5) and 16.8 (S.D.s 5.1), respectively, and the average global psychopathological symptom score was 32.3 (S.D.s 10.3). The purpose and methods of the study were explained to each subject who then gave written informed consent to participate. 2.2. Methods Three words were written in Japanese katakana characters with left-right reversal on a card (Fig. 1). We chose 240 words randomly out of the ‘rare’ section of a classified vocabulary table (National Language Research Institute, 1964) and listed them in a random order. Every word had a meaning and consisted of four to nine characters each. The subjects were then asked to read each word as quickly and accurately as possible. Each test session consisted of four blocks of 10 cards each. After two weeks, subjects participated in one more session consisting of different words. The reading time for each card for each subject was measured using a stopwatch, and it was added to provide total reading time for the session. In order to test the reliability of using a stopwatch for this kind of experiment, a reliability test was carried out. Rounding off the examiners’ respective times for the test to the nearest second yielded the same result. On the basis of this, we judged the use of a stopwatch as reliable. In the next step, to assess the retention of procedural memory, we examined the improvement rate of reading time. An improve-
The average reading time from sessions 1 and 2, respectively, were: 414 (S.D.s142) and 336 (S.D.s83) seconds for the control group; 554 (S.D.s225) and 460 (S.D.s174) seconds for the schizophrenic group (Fig. 2). To examine the effects of session and subject, we employed subject and session as independent variables and reading time as a dependant variable in repeated measures ANOVA (Table 1). As a result, the main effect of subject was significant (Fs6.44, d.f.s1, P0.02), and the reading time of schizophrenia patients was longer than that of normal controls. The main effect of session was also significant (Fs24.04, d.f.s1, P-0.001), as the reading time for session 2 was shorter than that for session 1. The interaction of session and subject, on the other hand, was not significant. From this result, we deduce that the learning effects seen in schizophrenic patients rank with those of normal controls. 3.2. Relationship between performance on mirror reading task and clinical symptoms of individuals with schizophrenia Correlation coefficients between the reading time and clinical symptom scores are displayed in Table 2. There was a marked correlation between the reading time in sessions 1 and 2 and the negative symptom scores on the PANSS. By contrast, no notable correlation could be detected between the reading time and positive symptom scores. We also examined relationships between the improvement rate of reading time and psychiatric symptoms. The average improvement rate of schizophrenics was 13.8 (S.D.s17.1)%. No signifi-
306
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
Fig. 2. Reading time of each session in mirror reading task.
rotor tests (Schwartz et al., 1996; Schmand et al., 1992; Goldberg et al., 1990). Also, Clare et al. reported that individuals with schizophrenia could indeed learn the mirror reading task despite exhibiting lower completion performance than healthy controls. In the present study using Japanese characters, the schizophrenic group likewise required longer reading time than the control group did, but the patients showed the same rate of improvement, indicating that the two groups had equal speeds of learning this task. This finding confirms the results of earlier studies that procedural memory is retained in schizophrenia. Schmand et al. reported no notable correlation between schizophrenic symptoms and Tower of Hanoi test results (Schmand et al., 1992). Clare et al. examined schizophrenia patients using a mirror reading task but did not investigate the relation
cant correlation was found between the improvement rate and scores of the PANSS (positive symptoms, rs0.186, P)0.05; negative symptoms, rsy0.115, Ps0.66; total symptoms, rsy0.09, Ps0.74). 4. Discussion This study demonstrates that: (1) although individuals with schizophrenia exhibit reading performances inferior to those of healthy controls on the Japanese mirror reading task, they do have the ability to learn procedural memory; (2) reading time for the mirror reading task is related to the severity of the each patient’s negative symptoms. In the past, procedural memory was shown to be preserved in individuals with schizophrenia by methods such as the Tower of Hanoi and pursuit Table 1 ANOVA table
Main effect Subject Repeated session Interaction effect Subject by session
Sums of squares
Degree of freedom
Mean square
F
337944.80 145004.34
1 1
337944.80 145004.34
6.44* 24.04**
1373.11
1
1373.11
Subjects are repeated as independent variables and reading time as a dependent variable in repeated measures ANOVA. * P-0.05. ** P-0.01.
0.23
K. Takano et al. / Psychiatry Research 109 (2002) 303–307
307
Table 2 Correlation between mirror reading time and clinical symptoms scores for subjects with schizophrenia PANSS
Session 1 reading time
Session 2 reading time
Positive symptoms score Negative symptoms score Total score
0.27 0.53* 0.38
0.18 0.67** 0.48*
Values are Pearson product-moment correlation coefficients between reading time and clinical symptom scores. * P-0.05. ** P-0.01.
between symptoms and task performance (Clare et al., 1993). The present study indicates a strong correlation between the overall mirror reading task completion performance and negative symptoms, while showing no relationship between the performance improvement rates and negative symptoms. This suggests that negative symptoms in schizophrenia have a considerable influence on the level of mirror reading performance ultimately achieved, but not on the learning speed. This finding means that procedural memory can be used to acquire skills and promote the return of schizophrenic patients to society. These results provide a powerful rationale for rehabilitation training. SST is an approach to rehabilitation designed for schizophrenic patients to gain communication techniques required in daily life and social skills necessary for independence. In SST, patients practice social skills through behavior therapy such as role plays and feedback. Procedural memory is considered to contribute to the acquisition of skills through such training. Schizophrenic patients have been shown to acquire social skills through SST. Also, a report indicates some correlation between completion performance and verbal memory (Corrigan et al., 1992). However, there have been no indications of correlations between learning speed and verbal memory. In actuality, even patients with unsatisfactory verbal memory performance acquire skills through SST, indicating skill acquisition by procedural memory as well. We have not explored the relationship between the procedural memory and skill acquisition through SST by schizophrenic patients, but it is a topic for future study.
References Clare, L., McKenna, P.J., Mortimer, A.M., Baddeley, A.D., 1993. Memory in schizophrenia: what is impaired and what is preserved? Neuropsychologia 31, 1225–1241. Corrigan, P.W., Wallace, C.J., Green, M.F., 1992. Deficits in social schemata in schizophrenia. Schizophrenia Research 8, 129–135. Folstein, M.F., Folstein, S.E., McHugh, P.R., 1975. MiniMental State: a practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research 12, 189–198. Goldberg, T.E., Weinberger, D.R., Pliskin, N.H., Berman, K.F., Podd, M.H., 1989. Recall memory deficit in schizophrenia. A possible manifestation of prefrontal dysfunction. Schizophrenia Research 2, 251–257. Goldberg, T.E., Saint, C.J.A., Weinberger, D.R., 1990. Assessment of procedural learning and problem solving in schizophrenic patients by Tower of Hanoi type tasks. Journal of Neuropsychiatry and Clinical Neurosciences 2, 165–173. Kay, S.R., Opler, L.A., Spitzer, R.L., Williams, J.B., Fiszbein, A., Gorelick, A., 1991. SCID-PANSS: two-tier diagnostic system for psychotic disorders. Comprehensive Psychiatry 32, 355–361. Manschreck, T.C., Maher, B.A., Rosenthal, J.E., Berner, J., 1991. Reduced primacy and related features in schizophrenia. Schizophrenia Research 5, 35–41. McClain, L., 1983. Encoding and retrieval in schizophrenics’ free recall. Journal of Nervous and Mental Disease 171, 471–479. Schmand, B., Brand, N., Kuipers, T., 1992. Procedural learning of cognitive and motor skills in psychotic patients. Schizophrenia Research 8, 157–170. Schwartz, B.L., Rosse, R.B., Veazey, C., Deutsch, S.I., 1996. Impaired motor skill learning in schizophrenia: implications for corticostriatal dysfunction. Biological Psychiatry 39, 241–248. Wykes, T., Reeder, C., Corner, J., Williams, C., Everitt, B., 1999. The effects of neurocognitive remediation on executive processing in patients with schizophrenia. Schizophrenia Bulletin 25, 291–306.