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| Laterality of cognitive dysfunction in schizophrenia: A cross-sectional study |
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Kanchan Pant1, Shobit Garg2, Sai Krishna Tikka3, Preeti Mishra4, Priya Tyagi5
1 Research Scholar, Department of Psychiatry, Shri Guru Ram Rai Institute of Medical and Health Sciences, 248001, Uttarakhand, India
2 Professor & Head, Department of Psychiatry, Shri Guru Ram Rai Institute of Medical and Health Sciences, 248001, Uttarakhand, India
3 Associate Professor, Department of Psychiatry, All India Institute of Medical Sciences (AIIMS), Bibinagar, Hyderabad, India
4 Associate professor, Department of Psychiatry, Shri Guru Ram Rai Institute of Medical and Health Sciences, 248001, Uttarakhand, India
5 Junior Resident, Department of Psychiatry, Shri Guru Ram Rai Institute of Medical and Health Sciences, 248001, Uttarakhand, India
Click here for correspondence address and email
| Date of Submission | 28-Apr-2022 |
| Date of Acceptance | 06-Jun-2022 |
| Date of Web Publication | 14-Jul-2022 |
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Background: Clear localization (or) related deficits would make gateways for forming rehabilitation strategies much needed to enhance functionality in schizophrenia. We aimed to study the neuropsychological dysfunction including laterality in schizophrenia patients by using the native All India Institute of Medical Sciences Comprehensive Neuropsychological Battery (AIIMS CNB) in Hindi Adult form.
Materials and Methods: In a cross-sectional study design, 40 right-handed schizophrenia patients in the age range of 18–59 years with primary education who can read and write were purposively recruited. Neuropsychological assessment and psychopathology were assessed by AIIMS CNB and Positive and Negative Syndrome Scale (PANSS), respectively. Raw scores and T-scores were recorded, and lateralization scores were calculated. The localization was estimated by commuting eight lobe scales. Statistical analyses of the quantitative scores were done using IBM SPSS 28.
Results: The mean PANSS total scores and dose of chlorpromazine equivalents of the sample were 88.900 ± 9.940 and 497.500 ± 100.607 mg. 62.5% of the participants reportedly had the presence of brain dysfunction based on T-scores. Right hemispheric lateralization of cognitive deficits was present markedly in 95% of schizophrenia subjects. As per lobe scale scores, the right sensory-motor lobe (60%) and the right frontal lobe (27.5%) were found to be most dysfunctional.
Conclusion: Majority of schizophrenia patients are dysfunctional as per AIIMS CNB and have hemispheric lateralization (right) of deficits. Our findings challenge the loss of asymmetry verdicts in schizophrenia.
Keywords: Neurocognition, neuropsychology, psychopathology
How to cite this URL:
Pant K, Garg S, Tikka SK, Mishra P, Tyagi P. Laterality of cognitive dysfunction in schizophrenia: A cross-sectional study. Arch Ment Health [Epub ahead of print] [cited 2023 Mar 26]. Available from: https://www.amhonline.org/preprintarticle.asp?id=351033 |
| Introduction | |  |
Schizophrenia is essentially a neurobiological disorder and is usually associated with neurocognitive deficits.[1] Neurocognitive deficits are mentioned to have an impact on overall treatment outcome and functionality in schizophrenia.[2] The profile of deficits is extensive, severe, and present in almost all patients.[2] The impairment is greatest in the domains of attention, memory (working), processing speed, problem-solving, and social cognition.[2] Indian studies have found that most of these deficits have not only been implicated as schizophrenia disease markers but also have been postulated to be endophenotypes as well.[3],[4],[5]
Neuropsychological assessment provides a coherent description of brain dysfunction and its effect on a person's emotions, personality, interpersonal relationships, and functioning.[2] A comprehensive neuropsychological assessment is deemed necessary because of the extent of neuropsychological deficits and their impact on rehabilitation and overall treatment outcome.[6] The All India Institute of Medical Sciences Comprehensive Neuropsychological Battery (AIIMS CNB)[7] is a fixed approach neuropsychological battery. Its readiness in Hindi makes it more suitable to administer to the Indian population. However, even after a decade of its development, there is a relative dearth of the studies that utilize the battery to assess neuropsychological dysfunctions in schizophrenia patients.
Studies regarding laterality or asymmetry reductions of the brain in schizophrenia, both structural and functional, have shown inconsistent findings.[8],[9],[10],[11] Clear localization (or) related deficits would make gateways for forming rehabilitation strategies much needed to enhance functionality in schizophrenia subjects.[12] In view of the above, the present study was conducted to assess neuropsychological dysfunctions including laterality in schizophrenia patients by the native neuropsychological tool.
| Materials and Methods | | |
This study was conducted using a cross-sectional design at a tertiary care medical institute in northern India. The type of sampling technique employed was purposive.
Participants
Only right-handed patients aged 18–59 years, meeting the diagnostic criteria for schizophrenia as per the ICD-10 DCR,[13] with primary education who can read and write were recruited. Exclusion criteria consisted of subjects with a seizure disorder, a history of organicity and substance dependence except for nicotine and caffeine, and a physical disability affecting the performance on neuropsychological assessment. A sample of 40 patients with schizophrenia was purposively assigned for the neuropsychological assessment. Written and signed informed consent was taken from the patients and caregivers before enrolment. This study was registered in the Clinical Trials Registry India (CTRI Number: CTRI/2020/09/036922). The study protocol was approved by the institute ethics committee (SGRR/IEC/23/21; IEC Registration No. ECR/710/Institute/UK/2015/RR-18). Baseline neuropsychological data of the recruited subjects registered in the trial have been presented in this study.
Clinical measures
Psychopathology was measured via the Positive and Negative Syndrome Scale (PANSS). The scale is one among the best-validated and standardized instruments for assessing positive, negative, and general psychopathology (GP) associated with schizophrenia. Of the 30 items, seven are positive symptoms, seven are negative symptoms, and 16 are GP symptoms. In addition to these measures, a composite scale is scored by subtracting the negative score from the positive score.[14] The neuropsychological profile and handedness preference were assessed the AIIMS CNB in Hindi Adult form.[7]
The AIIMS CNB provides a research instrument allowing refined statistical analysis of brain behavior relationships for both clinical use and theoretical investigation. It requires a short administration time of not more than 3 h. It is easily portable and administered at the bedside. It is a useful tool that can be used in the identification, lateralization, and localization of brain dysfunction in subjects from 15 to 80 years of age. In AIIMS CNB, there are 160 items in the Hindi language distributed over 10 basic scales: motor scale, tactile scale, visual scale, receptive speech scale, expressive speech scale, reading scale, writing scale, arithmetic scale, memory scale, and intellectual processes scale. Subsequent three scales were derived from these 10 basic scales, i.e., right hemisphere scale, left hemisphere scale, and pathognomonic scale. Receptive speech is not included in the total score scale. Therefore, for the calculation of the total score 12 out of the 13 subscales and a total of 200 items is considered. A five-point scale for each item is given for evaluating the performance to enhance the precision of the battery. Zero credit is awarded for passing out the items successfully and four credits for a complete failure. Credits 2 or 3 are given to the intermediate performance depending upon its level. The items retained were allotted credits along the dimensions, i.e., accuracy, frequency, time, rate, speed, quality, and appropriateness.[7]
Procedure
The AIIMS CNB has been administered individually to each subject using the consistent administration procedure. Assessments were performed in a fixed order in a quiet room. Ratings on items of individual clinical scales were summed up; for neuropsychological assessment, raw score for each scale was generated. Raw scores were converted into T-scores for each clinical scale as per the manual of the battery to have better discrimination of the degree of impairment on a particular scale.[7]
To assess the presence of brain dysfunction, the raw scores on 200 items in the “total” score scales were summed up. The total of raw scores on this scale was then converted into a T-score, and an expected T-score is also calculated. If the T-score is higher than the expected T-score (in the “total” score scale), the subject is indicated to be having an organic brain dysfunction.[6]
To assess the lateralization of brain dysfunction, sum up the raw scores on both right/left hemisphere scales. Raw scores on both scales are then converted into T-scores. The direction of difference in the T-scores on the right/left hemisphere scale is determined. If the direction of T-scores remains in + (plus), the right hemisphere dysfunction is inferred; and if − (minus), the left hemisphere brain dysfunction is inferred.[7]
To localize brain dysfunction, a raw score on each of the eight lobe scales (left frontal, left sensory-motor, left parietal-occipital, left temporal, right frontal, right sensory-motor, right parietal-occipital, and right temporal) is summed up. The total raw scores on each of the eight lobes are then converted into T-scores. All the eight raw and T-scores on lobe scales are assigned ranks. The highest raw and T-score were assigned Rank 1.[7]
Statistical analysis
Data of this study were evaluated using the IBM SPSS Statistics, version 28.0 (International Business Machines (IBM) Corporation, Armonk, New York).[15] Descriptive statistics were used in the analysis of frequencies, mean, and standard deviation (SD). Pearson correlation was assessed between PANSS scores (positive, negative, GP, and composite scores: anergia, thought, activation, paranoia, and depression) with Rank 1 lobe scales as per raw scores.
| Results | | |
[Table 1] shows a description of sociodemographic variables and clinical variables; sample selected is predominantly unmarried (62.5%) and is of male gender (60%). Majority of the subjects belonged to urban communities (82.5%), fitted to upper-middle socioeconomic status (72.5%), and had not been employed (75%). Majority of the subjects belonged to nuclear families (82.5%) living with both parents (45%). Most of the subjects did not have any significant history, suggestive of substance dependence (72.5%) and family psychiatric morbidity (57.5%). Interestingly, majority of participants were born in the winter season (45%) and were the youngest of all the siblings (62.5%). The mean age of the study sample is 29.92 ± 9.625 years. The mean PANSS total scores and dose of chlorpromazine equivalents[16] of the sample were 88.900 ± 9.940 and 497.500 ± 100.607 mg, respectively. | Table 1: Distribution of sociodemographic and clinical variables in schizophrenia patients (n=40)
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62.5% of the participants reportedly had the presence of brain dysfunction based on T-scores. Right hemispheric lateralization of cognitive deficits was present markedly in 95% of schizophrenia subjects. As per lobe scale scores, the right sensory-motor lobe (60%) and right frontal lobe (27.5) were found to be most dysfunctional [Table 1].
[Table 2] shows the mean values of the raw scores and T-scores on all the scales including subdomains (motor, tactile, etc.), lobe scales (left frontal, left sensory-motor, left parietal-occipital, left temporal, right frontal, right sensory-motor, right parietal-occipital right temporal), and total AIIMS CNB scores (mean ± standard deviation T-scores = 73.3000 ± 9.28799). | Table 2: Distribution of each All India Institute of Medical Science Comprehensive Neuropsychological Battery in Hindi Adult form neuropsychological scores and Lobe Scale Scores
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[Table 3] shows a correlation between PANSS (positive [P], negative [N], GP, and composite scores: anergy, thought, activation, paranoia, depression) with Rank 1 lobe scales scores (based on raw scores). There is negative correlation found between respective activation (r (40) = −0.329, P = 0.044) and depression scores (r (40) = −0.367, P = 0.020) with left sensory-motor. Activation scores also have had a negative correlation with left parietal-occipital scores (r (40) = −0.349, P = 0.027). The left temporal region has been found to have a negative correlation with PANSS-P scores (r (40) = −0.382, P = 0.039). On the other hand, right temporal scores had a positive correlation of PANSS-GP (r (40) = 0.347, P = 0.028) scores. | Table 3: Correlation between Positive and Negative Syndrome Scale (positive, negative, general psychopathology, and composite scores) with the lobe scale with the highest raw score in localization of brain dysfunction as per All India Institute of Medical Science Comprehensive Neuropsychological battery in Hindi Adult form
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| Discussion | | |
Neuropsychological dysfunction is significantly common and severe in schizophrenia patients. Neuropsychological dysfunction is directly related to the presence and severity of psychotic symptoms, particularly negative symptoms in schizophrenia, which deteriorate daily life functioning. Moreover, very recently, it has been shown that impaired real-time cognitive performance and psychotic symptom expression in daily life are closely linked.[17] Our study results, too, conform to the previous findings and have similar implications.
More important to the specific context of our study, schizophrenia has been postulated to underlie a failure of the normal lateralization process during development of the brain, and schizophrenia patients are found to have increased global brain asymmetry.[9] Few studies are available that worked in the identification, lateralization, and localization of brain dysfunction in schizophrenia, specifically using Hindi-based comprehensive neuropsychological battery.
Our study showed that the occurrence of brain dysfunction was found in most of the participants. It was significant in the right-hemisphere which supports the findings of previously done studies.[18],[19] Lobe scale scores in our study imply that mainstream brain dysfunction is targeted in the right sensory-motor lobe and right frontal lobe. Cerebral asymmetry with greater structural impairments in the right frontal lobe that correlated with worse performance on verbal memory tasks has been recently shown in a white matter tractographic study.[20] Moreover, various structural and functional neural impairments in the motor system, some circumscribed to the right motor cortex, have been shown in patients with schizophrenia.[21] The predominant involvement of the right sensory-motor cortex conforms to and supports the postulated role of parietal lobes, specifically the right parietal areas, in the emergence of schizophrenia symptoms[22] and the emerging role of impaired sensorimotor control in schizophrenia.[23] Our study findings show that while most psychopathology scores, i.e., positive symptoms, activation, and depression, correlated with left hemispheric impairments, only GP correlated with right temporal dysfunction. This finding is supported by a recent structural magnetic resonance imaging study by Mennigen et al.,[24] who showed that GP and positive symptoms are associated with specific grey matter reductions in the bilateral inferior temporal regions. Assumedly, on the background of existing literature on the role of left temporal regions in positive symptoms of schizophrenia, specifically, the left temporal impairments may have been related to the GP; this specific hemispheric correlation however was not conducted by the researchers. Our study results therefore imply this association, if confirmed in future studies.
Limitations and future directions
The sample size of this study was moderately small and consisted of right-handed participants only. Moreover, our study findings are not validated by neurophysiological or neuroimaging data that could validate the implication of brain dysfunction and laterality. These limit the generalizability and validity of the findings. For future studies, AIIMS CNB can also be used to evaluate the changes in neuropsychological functions in longitudinal studies. The results of the AIIMS CNB can also be correlated simultaneously with the various structural or functional neuroimaging techniques.
| Conclusion | | |
We conclude that a majority of schizophrenia patients have brain dysfunction as per AIIMS CNB and predominantly have right hemispheric lateralization of deficits. Our findings support the “increased brain asymmetry” verdicts in schizophrenia.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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Correspondence Address:
Shobit Garg,
Department of Psychiatry, Shri Guru Ram Rai Institute of Medical and Health Sciences, Dehradun - 248 001,
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/amh.amh_66_22
[Table 1], [Table 2], [Table 3] |
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