Perseverative Responses Research Articles

Lesions of the thalamic reuniens cause impulsive but not compulsive responses

On account of its strong efferent projections to the hippocampus, recent animal studies have emphasized an important role for the nucleus reuniens (NRe) of the midline thalamus in spatial memory. However, by virtue of its reciprocal connections with the orbital and ventromedial prefrontal cortex, the NRe may also be involved in aspects of executive inhibition. To date, there has been no systematic attempt to examine the role of the NRe in inhibitory mechanisms of response control. Accordingly, we compared rats with neurotoxic lesions of the NRe with sham surgery controls on performance of the 5-choice reaction time task, a test of visuospatial attention and inhibitory control. When tested post-operatively, rats with NRe lesions were unable to actively inhibit premature responses when the intertrial interval was varied. However, the same rats with NRe lesions showed normal inhibition of perseverative responses, and under some conditions were less perseverative than shams. The NRe lesion was also associated with a reduction in omissions and fast reward collection latencies, which persisted 2months following surgery. The NRe lesion did not affect response accuracy or latency to respond correctly throughout the course of experimental testing. Together, these results signify the important role of the NRe in impulse inhibition, especially when slight changes are made to the temporal demands of the environment, and reveal the potential contribution of the NRe in motivational processes.

Impaired executive functions in paediatric obsessive-compulsive disorder patients.

Isık Taner Y, Erdogan Bakar E, Oner O. Impaired executive functions in paediatric obsessive-compulsive disorder patients.Objective: There are only few studies which investigated the neuropsychological performances of paediatric patients with obsessive-compulsive disorder (OCD). Previous studies show that most of adult OCD patients had an onset of their first symptoms before the age of 15. Our objective was to evaluate the neuropsychological functions in paediatric patients with OCD.Methods: We compared the executive functions and general intelligence of child and adolescent OCD patients (n = 20) with age- and gender-matched healthy controls (n = 20). To compare mentioned skills, a neuropsychological test battery including Wechsler Intelligence Scale for Children-Revised (WISC-R), Wisconsin Card Sorting Test (WCST), Stroop Test and Verbal Fluency Test was performed.Result: Performances of the OCD and control subjects on neuropsychological tests were statistically analysed by using multivariate analysis of covariance (MANCOVA), in which Full Scale Intelligence Quotient (FSIQ) results were taken into consideration as a covariate to observe FSIQ's effect on test scores. Our results showed that the differences in WISC-R Picture Arrangement and Coding scores remained significant when co-analysed with FSIQ scores. In a similar manner, the OCD group exhibited worse performances on STR1-duration, STR3-duration, STR3-error, STR4-duration, STR4-error, STR5-correct response, and STR5-error as compared with the control group when FSIQ scores were taken into calculation. Some variables of the WCST (perseverative responses, percent errors, abstraction-flexibility and categories completed) also yield lower test scores in the OCD group. There was no significant difference between the groups regarding Verbal Fluency Test scores.Conclusion: Our results suggested that paediatric OCD patients had worse abstraction-flexibility, mental set-shifting, verbal comprehension and visuospatial/construction abilities.

Reducing Aphasic Perseverations: A Case Study

The purpose of this study was to measure outcomes resulting from a treatment designed to reduce aphasic perseverations by decreasing activation of the perseverative response and increasing activation of the target response. A single-subject design was used. A Spanish-speaking male with moderate-to-severe receptive-expressive aphasia participated in this study. Treatment involved the use of systematic reduction of interstimulus interval paired with semantic feature analysis. The treatment resulted in a decrease in perseveration, but only minor increases in naming accuracy on trained and untrained stimuli. In addition, an increase in overall verbal output was observed. Decreased perseveration was maintained during follow-up. Outcomes suggest the treatment successfully reduces perseveration and increases verbal output. Additional research is needed to evaluate the effectiveness of this treatment.

Poor inhibitory control and neurochemical differences in high compulsive drinker rats selected by schedule-induced polydipsia

Schedule-induced polydipsia (SIP), characterized by the development of excessive drinking under intermittent food reinforcement schedules, has been proposed as a model for obsessive-compulsive disorder, schizophrenia and drug abuse. The purpose of this study is to investigate if individual differences in SIP reflect psychopathological behavioural traits related to lack of inhibitory control and reactivity to novelty, and if these differences have neurochemical correlates. Outbred Wistar rats were selected for being either high (HD) or low (LD) drinkers according to their SIP behaviour. We tested locomotor reactivity to a novel environment and inhibitory control on the five-choice serial reaction time task (5-CSRTT), under baseline vs. extinction conditions and following challenge with D: -amphetamine (saline, 0.5 or 1 mg/kg). Post-mortem analyses of the monoaminergic levels in different brain regions were also analysed. Compared to LD animals, HD rats exhibiting SIP acquisition showed no differences in spontaneous locomotor reactivity to novelty. On the 5-CSRTT, HD rats showed a greater increase in perseverative responses under extinction, a trend towards elevated premature responses on baseline, and a significantly greater elevation of premature responses to D: -amphetamine 0.5 mg/kg. The HD animals also exhibited increased serotonin activity in the amygdala, and correlational analyses between the rate of drinking on SIP and monoamine levels also revealed altered dopaminergic mesolimbic function. These findings show that HD rats selected by SIP exhibit compulsive and impulsive behaviour based on measures of performance on the five-choice serial reaction time task and associated with changes in monoaminergic systems in limbic-striatal circuitry.

The effects of the D2 dopamine receptor antagonist, eticlopride, on attention following bilateral vestibular deafferentation in the rat

Loss of vestibular function has been associated with cognitive impairment, including attentional problems. The aim of this study was to investigate the effects of the D2 dopamine receptor antagonist, eticlopride (0.02, 0.04 and 0.06mg/kg; s.c.), on attention and impulsivity in rats at 2 months following bilateral vestibular deafferentation (BVD), using a 5 choice serial reaction time task (5CSRTT). The levels of the D2 receptor protein in the frontal cortex were measured at 1 and 6 months post-BVD using western blotting. Eticlopride caused a dose-dependent decrease in response in the 5CSRTT, which was greater for sham than for BVD rats in terms of the percentage of correct responses and the number of perseverative responses. There were no changes in the amount of the D2 receptor in the frontal cortex at 1 or 6 months post-BVD; however, D2 receptor levels were significantly higher on the right side than the left in both sham and BVD animals. These results suggest that BVD causes an increase in perseverative behaviour that D2 receptor blockade does not eliminate, but that D2 receptors in the frontal cortex are unchanged.

Response Perseveration in Stimulant Dependence Is Associated with Striatal Dysfunction and Can Be Ameliorated by a D2/3 Receptor Agonist

Compulsivity is a hallmark of drug addiction and in animal models is measured by consecutive incorrect responses to a previously rewarded stimulus during reversal learning. The aim of this study was to measure behavioral and neural markers of compulsivity in stimulant-dependent individuals and to test whether these markers could be modulated by treatment with drugs targeting the dopamine system. In a randomized, double-blind, placebo-controlled, crossover design, stimulant-dependent individuals (SDIs; n = 18) and healthy volunteers (n = 18) received single doses of dopamine D(2/3) receptor antagonist (amisulpride, 400 mg) and agonist (pramipexole, 0.5 mg) drugs. To examine compulsivity and its dopaminergic modulation more generally, patients with obsessive-compulsive disorder (OCD; n = 18) were also included in the study. SDIs made significantly more perseverative responses to the previously correct stimulus immediately following reversal, compared with both healthy volunteers and patients with OCD. Across all participants, the number of perseverative errors was negatively correlated with functional activation in right fronto-striato-parietal networks-in particular, the right caudate nucleus. In SDIs, perseveration-related caudate activation was abnormally reduced in the placebo condition, but the dopamine D(2/3) agonist pramipexole normalized both perseverative responding and related activation of the right caudate. Perseveration during reversal learning was associated specifically with stimulant dependence rather than with compulsive behaviors more generally. The beneficial effects of a dopamine agonist drug challenge on both behavior and associated brain activation in SDIs may indicate new avenues for pharmacologic treatment in stimulant dependence.

Executive functioning and alcohol binge drinking in university students

Background Binge drinking (BD) is prevalent among college students. Studies on alcoholism have shown that the prefrontal cortex is vulnerable to the neurotoxic effects of alcohol. The prefrontal cortex undergoes both structural and functional changes during adolescence and young adulthood. Sex differences have been observed in brain maturation and in alcohol-induced damage. The objective of the present study was to analyze the relationship between BD and cognitive functions subserved by the prefrontal cortex in male and female university students. Methods The sample comprised 122 undergraduates (aged 18 to 20 years): 62 BD (30 females) and 60 non-BD (29 females). Executive functions were assessed by WMS-III (Backward Digit Span and Backward Spatial Span), SOPT (abstract designs), Letter Fluency (PMR), BADS (Zoo Map and Key Search) and WCST-3. Results BD students scored lower in the Backward Digit Span Subtest and generated more perseverative responses in the SOPT In relation to interaction BD by sex, BD males scored lower in the Backward Digit Span test than BD females and non-BD males. Conclusions BD is associated with poorer performance of executive functions subserved by the dorsolateral prefrontal cortex. The results do not support enhanced vulnerability of women to alcohol neurotoxic effects. These difficulties may reflect developmental delay or frontal lobe dysfunction.

Neuropsychological profiling of impulsivity and compulsivity in cocaine dependent individuals

Research on the relative impact of trait impulsivity vs. drug exposure on neuropsychological probes of response inhibition vs. response perseveration has been posited as a valid pathway to explore the transition between impulsivity and compulsivity on psychostimulant dependence. The objectives of this study are to examine performance differences between cocaine-dependent individuals (CDI) and healthy comparison individuals (HCI) on neuropsychological probes of inhibition and perseveration and to examine the predictive impact of trait impulsivity-a proxy of premorbid vulnerability, and severity of cocaine use-a proxy of drug exposure, on CDI's performance. Forty-two CDI and 65 HCI were assessed using the UPPS-P Scale (trait impulsivity), the Stroop and go/no-go (inhibition) and revised-strategy application and probabilistic reversal tests (perseveration). CDI, compared to HCI, have elevated scores on trait impulsivity and perform significantly poorer on inhibition and perseveration, with specific detrimental effects of duration of cocaine use on perseveration. CDI have both inhibition and perseveration deficits; both patterns were broadly indicative of orbitofrontal dysfunction in the context of reinforcement learning. Impulsive personality and cocaine exposure jointly contribute to deficits in response perseveration or compulsivity.

Impaired Frontal Executive Function and Predialytic Chronic Kidney Disease

To investigate the nature of frontal dysfunction associated with chronic kidney disease (CKD) in people without stroke or depressive disorders. Cross-sectional. Community based. Five hundred twenty-nine community-dwelling participants. Participants with CKD were classified into one of three diagnostic groups based on their estimated glomerular filtration rate (eGFR): normal (≥ 60.0 mL/min per 1.73 m(2)), mild CKD (45.0-59.9 mL/min per 1.73 m(2)), or moderate to severe CKD (<45.0 mL/min per 1.73 m(2)). Cognitive function was assessed using the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological Assessment Battery, lexical fluency, digit span test, and the 64-card Wisconsin Card Sorting Test. Perseverative responses and perseverative errors were significantly more prevalent in the group with moderate to severe CKD than in those without CKD and those with mild CKD. The mean number of perseverative responses was 28.6 ± 16.9 in participants with moderate to severe CKD, 19.0 ± 11.4 in those with mild CKD, and 17.1 ± 10.6 in those without CKD (P < .001, ANCOVA). The mean number of perseverative errors was 23.1 ± 12.3 in participants with moderate to severe CKD, 16.2 ± 8.3 in those with mild CKD, and 14.8 ± 7.8 in those without CKD (P < .001, analysis of covariance). The odds ratios in the fully adjusted model for the presence of moderate to severe CKD for perseverative responses and perseverative errors were 4.82 (95% confidence interval (CI) = 2.14-10.85, P < .001) and 5.01 (95% CI = 2.22-11.28, P<.001), respectively. Frontal dysfunction, particularly perseverative errors and responses, was associated with moderate to severe CKD in the population studied.

Social Deficits and Perseverative Behaviors, but not Overt Aggression, in MAO-A Hypomorphic Mice

Monoamine oxidase (MAO)-A is a key enzyme for the degradation of brain serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine (NE). In humans and mice, total MAO-A deficiency results in high 5-HT and NE levels, as well as elevated reactive aggression. Here we report the generation of MAO-A(Neo) mice, a novel line of hypomorphic MAO-A mutants featuring the insertion of a floxed neomycin-resistance cassette in intron-12 of the Maoa gene. This construct resulted in a chimeric, non-functional variant of the Maoa-Neo transcript, with a truncated C-terminus, likely due to aberrant splicing; these deficits notwithstanding, small amounts of functional Maoa transcript were found in the brain of MAO-A(Neo) mice. In the prefrontal cortex and amygdala, MAO-A(Neo) mice showed low, yet detectable, MAO-A catalytic activity, as well as 5-HT levels equivalent to WT littermates; conversely, the hippocampus and midbrain of MAO-A(Neo) mice featured a neurochemical profile akin to MAO-A-knockout (KO) mice, with undetectable MAO-A activity and high 5-HT concentrations. MAO-A(Neo) mice showed significant increases in dendritic length in the pyramidal neurons of orbitofrontal cortex, but not basolateral amygdala, in comparison with WT littermates; by contrast, the orbitofrontal cortex of MAO-A KO mice showed significant reductions in basilar dendritic length, as well as a profound increase in apical dendritic length. MAO-A(Neo) mice showed a unique set of behavioral abnormalities, encompassing reduced open-field locomotion, perseverative responses, such as marble burying and water mist-induced grooming, and a lack of anxiety-like behaviors in the elevated plus-maze and light-dark box paradigms. Notably, whereas MAO-A(Neo) and KO mice showed significant reductions in social interaction, only the latter genotype showed increases in resident-intruder aggression. Taken together, our findings indicate that MAO A hypomorphism results in behavioral and morphological alterations distinct from those featured by MAO-A KO mice.

Abnormally persistent fMRI activation during antisaccades in schizophrenia: A neural correlate of perseveration?

ObjectiveImpaired antisaccade performance is a consistent cognitive finding in schizophrenia. Antisaccades require both response inhibition and volitional motor programming, functions that are essential to flexible responding. We investigated whether abnormal timing of hemodynamic responses (HDRs) to antisaccades might contribute to perseveration of ocular motor responses in schizophrenia. We focused on the frontal eye field (FEF), which has been implicated in the persistent effects of antisaccades on subsequent responses in healthy individuals. MethodEighteen chronic, medicated schizophrenia outpatients and 15 healthy controls performed antisaccades and prosaccades during functional MRI. Finite impulse response models provided unbiased estimates of event-related HDRs. We compared groups on the peak amplitude, time-to-peak, and full-width half-max of the HDRs. ResultsIn patients, HDRs in bilateral FEF were delayed and prolonged but ultimately of similar amplitude to that of controls. These abnormalities were present for antisaccades, but not prosaccades, and were not seen in a control region. More prolonged HDRs predicted slower responses in trials that followed an antisaccade. This suggests that persistent FEF activity following an antisaccade contributes to inter-trial effects on latency. ConclusionsDelayed and prolonged HDRs for antisaccades in schizophrenia suggest that the functions necessary for successful antisaccade performance take longer to implement and are more persistent. If abnormally persistent neural responses on cognitively demanding tasks are a more general feature of schizophrenia, they may contribute to response perseveration, a classic behavioral abnormality. These findings also underscore the importance of evaluating the temporal dynamics of neural activity to understand cognitive dysfunction in schizophrenia.

Performance on the Wisconsin Card Sorting Test in families of schizophrenia patients with different familial loadings.

Despite the consistent presence of performance deficits on the Wisconsin Card Sorting Test (WCST) in schizophrenia patients, whether poorer performance is also present in their nonpsychotic relatives is not certain. This study aimed to estimate both the recurrence risk ratio (λs) and the heritability of WCST scores in simplex and multiplex families, respectively, and to examine the influence of familial loading on these estimates. Participants were patients with schizophrenia and their nonpsychotic first-degree relatives from 168 simplex families and 653 multiplex families as well as 440 normal comparisons. On the basis of adjusted z scores, both the λs at a series of cutoff points and heritability estimates based on variance component modeling in the nonpsychotic relatives of schizophrenia patients were estimated. The WCST deficits in schizophrenia patients were more prominent in multiplex families than in simplex ones. Among relatives, WCST deficits were limited to parents of multiplex families for most WCST scores and siblings from multiplex families for total errors, perseverative responses, and perseverative errors. Pertaining to λs, the estimates for multiplex families (highest estimates ranging from 7.9 to 11.0) were greater than those for simplex ones (<2.5). Nevertheless, the heritability estimates were very similar between simplex (ranging from 0% to 17%) and multiplex (ranging from 0% to 21%) families, with the latter having slightly greater values than the former. There is only a small-to-modest familial aggregation on part of WCST scores in families of schizophrenia patients, and this may limit its use as endophenotypic markers to schizophrenia susceptibility.

Impaired Attention in the 3xTgAD Mouse Model of Alzheimer's Disease: Rescue by Donepezil (Aricept)

Several mouse models of Alzheimer's disease (AD) with abundant β-amyloid and/or aberrantly phosphorylated tau develop memory impairments. However, multiple non-mnemonic cognitive domains such as attention and executive control are also compromised early in AD individuals. Currently, it is unclear whether mutations in the β-amyloid precursor protein (APP) and tau are sufficient to cause similar, AD-like attention deficits in mouse models of the disease. To address this question, we tested 3xTgAD mice (which express APPswe, PS1M146V, and tauP301L mutations) and wild-type control mice on a newly developed touchscreen-based 5-choice serial reaction time test of attention and response control. The 3xTgAD mice attended less accurately to short, spatially unpredictable stimuli when the attentional demand of the task was high, and also showed a general tendency to make more perseverative responses than wild-type mice. The attentional impairment of 3xTgAD mice was comparable to that of AD patients in two aspects: first, although 3xTgAD mice initially responded as accurately as wild-type mice, they subsequently failed to sustain their attention over the duration of the task; second, the ability to sustain attention was enhanced by the cholinesterase inhibitor donepezil (Aricept). These findings demonstrate that familial AD mutations not only affect memory, but also cause significant impairments in attention, a cognitive domain supported by the prefrontal cortex and its afferents. Because attention deficits are likely to affect memory encoding and other cognitive abilities, our findings have important consequences for the assessment of disease mechanisms and therapeutics in animal models of AD.

Abnormal Structural Correlates of Response Perseveration in Individuals With Psychopathy

Structural deficits in the frontotemporal network have been shown in individuals with psychopathy and are posited to contribute to neuropsychological impairments such as response perseveration. However, no study to date has examined structural correlates of response perseveration in individuals with psychopathy. In this structural MRI study, the authors found higher correlations between increased response perseveration and reduced cortical thickness in the orbitofrontal and anterior temporal regions in individuals with psychopathy than in healthy-comparison subjects. The findings provide preliminary evidence suggesting potential contributions of frontotemporal structural deficits in neurocognitive impairment with perseveration in individuals with psychopathy.

Abnormal Structural Correlates of Response Perseveration in Individuals With Psychopathy

Structural deficits in the frontotemporal network have been shown in individuals with psychopathy and are posited to contribute to neuropsychological impairments such as response perseveration. However, no study to date has examined structural correlates of response perseveration in individuals with psychopathy. In this structural MRI study, the authors found higher correlations between increased response perseveration and reduced cortical thickness in the orbitofrontal and anterior temporal regions in individuals with psychopathy than in healthy-comparison subjects. The findings provide preliminary evidence suggesting potential contributions of frontotemporal structural deficits in neurocognitive impairment with perseveration in individuals with psychopathy.

Attention deficit induced by blockade of N-methyl d-aspartate receptors in the prefrontal cortex is associated with enhanced glutamate release and cAMP response element binding protein phosphorylation: role of metabotropic glutamate receptors 2/3

The hypothesis that attention deficits induced by the hypofunction of N-methyl d-aspartate (NMDA) receptors in the prefrontal cortex (PFC) might be associated with increased glutamate release and changes in the phosphorylation of the cyclic adenosine monophosphate response element-binding protein on serine 133 (p-S133CREB) was investigated in this study. Infusion of 50 ng/side 3-(R)-2-carboxypiperazin-4-propyl-1-phosphonic acid ((R)-CPP), a competitive glutamate NMDA receptor antagonist, into the medial prefrontal cortex (mPFC) of rats performing the five-choice serial reaction time (5-CSRT) task, reduced accuracy of visual discrimination (measured by % correct responses) and enhanced impulsivity (measured by the number of premature responses) and compulsivity (measured by the number of perseverative responses). The mGluR2/3 receptor agonist, LY379268, injected s.c. at 0.1 mg/kg, reduced (R)-CPP-induced impairment in attentional functioning (accuracy) and impulsivity but not compulsive perseveration. In parallel studies using microdialysis technique and Western blot analysis we found that (R)-CPP (100 μM) infused in the medial prefrontal cortex increased glutamate efflux whereas injected in the medial prefrontal cortex at a dose causing impairments in attentional performance (50 ng/side) increased p-S133CREB in the frontal cortex (FC), decreased it in the caudate-putamen (CPu) and was without effect in the nucleus accumbens (NAC). LY379268 at the dose effective in reducing (R)-CPP-induced behavioral deficit reduced both the (R)-CPP-induced rise in glutamate efflux in the prefrontal cortex and the increase in p-S133CREB in the frontal cortex but was without effect on the decrease in p-S133CREB in the caudate-putamen. The data provide evidence that enhanced glutamate release and phosphorylation of cAMP response element binding protein (CREB) on serine 133 may be associated to attention deficit and loss of impulse control. Furthermore they suggest that mGluR2/3 agonists have a therapeutic potential for cognitive deficits.

Errors on the WCST Correlate with Language Proficiency Scores in Spanish-English Bilingual Children

This study examined the relationship between the degree of balance in bilinguals (i.e., degree to which an individual shows equivalence in their level of mastery of two languages) and performance on executive function tests. Twenty-four "more balanced" and 16 "less balanced" Spanish-English bilingual, third- and fourth-grade children completed the Wechsler Abbreviated Scale of Intelligence, the English and Spanish Bilingual Verbal Ability Test (BVAT) (an objective measure of English and Spanish language proficiency), and executive function tests (Wisconsin Card Sorting Test [WCST] and Stroop Test). Significant correlations were found between the degree of balance and error scores on the WCST, such that participants with more similar scores on both English and Spanish BVAT (i.e., the more-balanced group) scored lower on perseveration measures of the WCST than the less-balanced group. Between-group comparisons showed significantly fewer perseverative errors and perseverative responses on the WCST in the more-balanced group compared with the less-balanced group. Stroop Test scores did not reveal group differences. These findings support previous results documenting a "bilingual advantage" on executive function tests and provide support for the hypothesis that the degree of balance moderates the relationship between bilingualism and executive functions.

Impaired ability to organize information in individuals with autism spectrum disorders and their siblings

Despite rigorous research on disturbances of executive function and social cognition in autism spectrum disorders (ASD), little information has been available concerning higher cognitive functions, such as the ability to focus and associate relevant features to form categories, or ‘organizing of information’. The purpose of this study was to investigate this issue by using the Wisconsin Card Sorting Test (WCST) and the Verbal Learning Task (VLT). Cognitive assessments were conducted in 22 individuals with ASD, 14 non-affected siblings, and 15 age-matched control subjects. Overall, individuals with ASD performed significantly worse on the WCST and VLT compared to their siblings and normal control subjects. Although siblings performed generally well on both tasks, they exhibited similar degree of perseverative responses in the WCST compared to the probands. A linear increase of the memory organization score in the VLT was also absent in siblings as well as the ASD group. These results suggest an impaired ability to organize information is one of the cognitive endophenotypes for ASD.

Instinctual impulses in obsessive compulsive disorder: A neuropsychological and psychoanalytic interface

Psychopathology of obsessive compulsive disorder (OCD) that has been characterized by a conflict between the ego and superego on one hand, and aggressive and sexual impulses emerging from the id on the other, and employment of characteristic defenses to combat intense conflicts being connected with ones’ biological disposition from the psychoanalytic school of thought now gets empirical foundation from neuroimaging research. The findings disregard the psychological construct, exclusively establishing the neurobiology of the disorder. With the objective to study the impact of sexual and aggressive impulses on the executive functions and processing speed in the patient group, 20 OCD patients (11 males, 9 females) and 20 normal control subjects, matched for all relevant variables including age, sex, educational level and handedness were studied. Sexual impulse and guilt was assessed on the Sex Guilt Rating Scale (SGRS), aggressive impulses were tested using State-Trait Anger Expression Inventory (STAXI), the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was used to assess symptom severity, executive functions were assessed through Wisconsin Card Sorting Test (WCST), and processing speed was assessed by employing the Processing Speed Index (PSI) – from WAIS III. It was found that the OCD group differed significantly from the controls, attaining significantly lower percentiles on Processing Speed Index and for all variables of WCST under consideration, namely, perseverative response, perseverative error, non-perseverative error, conceptual level response and number of categories completed. They reported higher scores on subscales of STAXI, specifically related to trait anger and lower scores on anger expression. On the items of SGRS, the OCD group significantly differed with the controls, expressing greater sexual inhibition. In conclusion, we propose an explanation of psychopathology of OCD, which addresses instinctual impulses, executive functions and neural substrates. Our findings contribute to understanding instinctual impulses from the neuropsychological perspective. The findings have implications for better eclectic understanding of the pathogenesis of OCD.

A diffusion tensor imaging study of the anterior limb of the internal capsule in schizophrenia

Frontal-subcortical cognitive and limbic feedback loops modulate higher cognitive functioning. The final step in these feedback loops is the thalamo-cortical projection through the anterior limb of the internal capsule (AL-IC). Using diffusion tensor imaging (DTI), we evaluated abnormalities in the AL-IC fiber tract in schizophrenia. Participants comprised 16 chronic schizophrenia patients and 19 male, normal controls, who were group matched for handedness, age, and parental socioeconomic status, and underwent DTI on a 1.5 Tesla GE system. We measured the diffusion indices, fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), and manually segmented, based on FA maps, AL-IC volume, normalized for intracranial contents (ICC). The results showed a significant reduction in the ICC-corrected volume of the AL-IC in schizophrenia, but did not show diffusion measure group differences in the AL-IC in FA, MD, RD or AD. In addition, in the schizophrenia patients, AL-IC FA correlated positively with performance on measures of spatial and verbal declarative/episodic memory, and right AL-IC ICC-corrected volume correlated positively with more perseverative responses on the Wisconsin Card Sort Test (WCST). We found a reduction in AL-IC ICC-corrected volume in schizophrenia, without FA, MD, RD or AD group differences, implicating the presence of a structural abnormality in schizophrenia in this subcortical white matter region which contains important cognitive, and limbic feedback pathways that modulate prefrontal cortical function. Despite not demonstrating a group difference in FA, we found that AL-IC FA was a good predictor of spatial and verbal declarative/episodic memory performance in schizophrenia.