Temporal Dynamics of the Default Mode Network Characterize Meditation-Induced Alterations in Consciousness.

Current research suggests that human consciousness is associated with complex, synchronous interactions between multiple cortical networks. In particular, the default mode network (DMN) of the resting brain is thought to be altered by changes in consciousness, including the meditative state. However, it remains unclear how meditation alters the fast and ever-changing dynamics of brain activity within this network. Here we addressed this question using simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to compare the spatial extents and temporal dynamics of the DMN during rest and meditation. Using fMRI, we identified key reductions in the posterior cingulate hub of the DMN, along with increases in right frontal and left temporal areas, in experienced meditators during rest and during meditation, in comparison to healthy controls (HCs). We employed the simultaneously recorded EEG data to identify the topographical microstate corresponding to activation of the DMN. Analysis of the temporal dynamics of this microstate revealed that the average duration and frequency of occurrence of DMN microstate was higher in meditators compared to HCs. Both these temporal parameters increased during meditation, reflecting the state effect of meditation. In particular, we found that the alteration in the duration of the DMN microstate when meditators entered the meditative state correlated negatively with their years of meditation experience. This reflected a trait effect of meditation, highlighting its role in producing durable changes in temporal dynamics of the DMN. Taken together, these findings shed new light on short and long-term consequences of meditation practice on this key brain network.

Standardization of Tests of Attention and Inhibition.

AIM: The aim of the study was to standardize tests of attention and inhibition for adults in the age range of 16-30 years, who had 1-10 years of formal education. The objectives were to develop normative data for the tests of attention and inhibition, to establish the reliability of the tests of attention and inhibition, and to establish the validity of the tests of attention and inhibition. MATERIALS AND METHODS: The tests studied were figural visual scanning test (FVST), auditory target detection test (ATDT), stop signal test, and go/no-go (GNG) test. The four tests were given to a normal sample of 60 subjects (30 males and 30 females). Reliability of the tests was determined by retesting 20 individuals, (10 subjects from each group) from the sample after an interval of 1 month. The tests were given to a matched clinical sample of patients with unilateral focal lesions, and the results were compared to test discriminant validity. Means, standard deviations, t-test, correlations, and percentiles were used to analyze the data. RESULTS AND CONCLUSION: Results indicated that FVST and ATDT were reliable and valid tests of attention and stop signal test and GNG test were reliable and valid measures of inhibition of motor processes.

Neural Correlates of Emotion: Acquisition versus Innate View Point.

BACKGROUND: Emotion entails cognitive processes that may either be conscious or unconscious. Emotions influence all aspects of cognition. AIM: The aim of the following study was to study the effect of education on neural correlates of emotions in healthy normal volunteers. MATERIALS AND METHODS: Sample consisted total of 61 healthy young educated adults in the age range of 18-40 years. The volunteers were asked to view neutral, pleasant and unpleasant pictures from international affective picture system in a magnetic resonance imaging (MRI) scanner. STATISTICS ANALYSIS: Rest-active block design paradigm, functional MRI results analyzed in statistical parametric mapping 8. RESULTS AND CONCLUSION: Activations associated with emotions were present in cerebral and cerebellar regions. Education influences emotion.

Unraveling Brain Functional Connectivity of encoding and retrieval in the context of education.

Human memory is an enigmatic component of cognition which many researchers have attempted to comprehend. Accumulating studies on functional connectivity see brain as a complex dynamic unit with positively and negatively correlated networks in perfect coherence during a task. We aimed to examine coherence of network connectivity during visual memory encoding and retrieval in the context of education. School Educated (SE) and College Educated (CE) healthy volunteers (n=60) were recruited and assessed for visual encoding and retrieval. Functional connectivity using seed to voxel based connectivity analysis of the posterior cingulate cortex (PCC) was evaluated. We noticed that there were reciprocal dynamic changes in both dorsolateral prefrontal cortex (DLPFC) region and PCC regions during working memory encoding and retrieval. In agreement with the previous studies, there were more positively correlated regions during retrieval compared to encoding. The default mode network (DMN) networks showed greater negative correlations during more attentive task of visual encoding. In tune with the recent studies on cognitive reserve we also found that number of years of education was a significant factor influencing working memory connectivity. SE had higher positive correlation to DLPFC region and lower negative correlation to DMN in comparison with CE during encoding and retrieval.

Cognitive deficits and its relation with psychopathology and global functioning in first episode schizophrenia.

AIM: The aim was to examine the cognitive deficits profile in first episode schizophrenia patients as well as examine the correlation between cognitive deficits, psychopathology and global functioning. Better understanding of these various facets of this debilitating illness is imperative in planning treatment, thereby limiting decline in global functioning. METHODS: Forty-nine schizophrenia patients with illness duration less than two years comprised the sample. A comprehensive battery of neuropsychological tests, the Positive and Negative Syndrome Scale and WHO Disability Assessment schedule were administered to assess cognitive functions, psychopathology and global functioning respectively. RESULTS: Cognitive deficit quotient for each patient was calculated. In this cohort 16.3% of patients had less than 25% of cognitive deficits, 38.8% had 25-50% of cognitive deficits, 36.7% had 50-75% of cognitive deficits and 8.2% of patients had more than 75% cognitive deficits. More than 50% of the patients in the present cohort showed deficits in the domains of attention, executive functions and learning and memory. Psychopathology significantly correlated with global functioning. Negative symptoms significantly correlated with cognitive functions of motor speed, attention and executive functions. Step wise linear regression analysis showed that duration of illness, attention (sustained attention), executive function (response inhibition), negative and positive psychopathology predicted level of global functioning at varied levels. CONCLUSIONS: Cognitive deficits in multiple domains were observed in the present cohort. Attention and executive functions predicted global functioning. There is a need for longitudinal studies with larger sample to examine the course of the cognitive deficits with progress in illness.

Reduced contribution of executive functions in impaired working memory performance in mild traumatic brain injury patients.

AIM: Mild traumatic brain injury (MTBI) is associated with often selective impairment of both working memory (WM) and the executive functions (EFs). Research indicates that one of the commonest deficits present in MTBI patients falls in the domain of WM. We aimed to investigate the role of EFs in WM impairment following MTBI. METHODS: Performance on the tests of EFs and the verbal and visuo-spatial WM of 30 consecutive MTBI patients were compared with age/education/IQ matched 30 normal healthy control participants. Correlation between EFs and WM was studied separately for the MTBI and the control group. RESULTS: The MTBI and control group were tested on a range of EF tests and WM. The MTBI group was demonstrated impairment on verbal and visuo-spatial WM and category fluency tests only. Furthermore, the MTBI group had fewer significant correlations between the WM and EFs (5 out of 54 possible correlations) than in the control group (13 out of 54 possible correlations). CONCLUSIONS: We suggest that MTBI may lead to WM deficits as the contribution of executive processes to support the WM is diminished following MTBI. Such an understanding of the poor WM performance in MTBI patients will be helpful when planning appropriate strategies for cognitive rehabilitation.

Addition of home-based cognitive retraining to treatment as usual in first episode schizophrenia patients: a randomized controlled study.

OBJECTIVE: We examined the effectiveness of a 2-month-long home-based cognitive retraining program together with treatment as usual (TAU; psychoeducation and drug therapy) on neuropsychological functions, psychopathology, and global functioning in patients with first episode schizophrenia (FES) as well as on psychological health and perception of level of family distress in their caregivers. MATERIALS AND METHODS: Forty-five FES patients were randomly assigned to either treatment group receiving home-based cognitive retraining along with TAU (n=22) or to control group receiving TAU alone (n=23). Patients and caregivers received psychoeducation. Patients and one of their caregivers were assessed for the above parameters at baseline, post-assessment (2 months) and at 6-months follow-up assessment. RESULTS: Of the 45 patients recruited, 12 in the treatment group and 11 in the control group completed post-intervention and follow-up assessments. Addition of home-based cognitive retraining along with TAU led to significant improvement in neuropsychological functions of divided attention, concept formation and set-shifting ability, and planning. Effect sizes were large, although the sample size was small. CONCLUSIONS: Home-based cognitive retraining program has shown promise. However, further studies examining this program on a larger cohort with rigorous design involving independent raters are suggested.

Growth patterns of neuropsychological functions in Indian children.

We investigated age-related differences in neuropsychological performance in 400 Indian school children (5-15 years of age). Functions of motor speed, attention, executive functions, visuospatial functions, comprehension, learning, and memory were examined. Growth curve analysis was performed. Different growth models fitted different cognitive functions. Neuropsychological task performance improved slowly between 5 and 7 years, moderately between 8 and 12 years and slowly between 13 and 15 years of age. The overall growth patterns of neuropsychological functions in Indian children have been discussed with the findings reported on American children. The present work describes non-linear, heterogeneous, and protracted age trends of neuropsychological functions in Indian children and adolescents.

Cognitive profile and structural findings in Wilson's disease: a neuropsychological and MRI-based study.

BACKGROUND: Systematic studies on neuropsychological profile in patients with Wilson's disease (WD) are far and few. AIM: To examine the profile of cognitive deficits and their magnetic resonance imaging (MRI) findings in patients with WD. PATIENTS AND METHODS: Twelve confirmed patients of WD (age at onset and evaluation, 13.7±11.2 and 21.7±5.3 years, respectively; M-F ratio, 7:5) on de-coppering therapy constituted the study sample. Battery of neuropsychological tests measuring mental speed, motor speed, sustained attention, focused attention, verbal category fluency, verbal working memory, response inhibition, planning, concept formation, set-shifting ability, verbal and visual learning and memory were administered. Phenotypic details and observations on MRI of brain carried out within six months of neuropsychological assessment were documented. RESULTS: Neuropsychological assessment elicited cognitive deficits in multiple domains in all but one patient, who had normal MRI. Percentage of patients in the deficit range in various domains included: motor speed: 73%; verbal working memory, sustained and focused attention: 50%; verbal learning: 42%; visuo-constructive ability, verbal memory, mental speed: 33%-34%; verbal fluency, set-shifting ability, visual memory, verbal memory: 25%-27%; and verbal recognition: 17%. MRI was normal in three patients, and revealed variable abnormalities in the remaining: cerebral atrophy in 3; brainstem atrophy in 2; signal changes in basal ganglia in 9; and brainstem signal changes in 5. None had subcortical white matter changes. Two patients with normal MRI showed cognitive deficits. CONCLUSION: This study provides insight into the complex cognitive and brain changes observed on MRI in WD. Use of advanced MRI techniques in a larger cohort may improve understanding regarding functional and structural brain changes observed in similar disorders.

Apolipoprotein E polymorphism and outcome after mild to moderate traumatic brain injury: a study of patient population in India.

BACKGROUND: The nature and extent of recovery after traumatic brain injury (TBI) is heterogeneous. Apolipoprotein E (APOE) plays a major role in repair of cell membrane and growth of neurites following injury to cells. Studies done on the western population have shown that the APOE e4 genotype is associated with poor survival following neurotrauma. AIM: To explore the association of APOE polymorphism and outcome following TBI in a patient population from a tertiary care hospital exclusive for neurological diseases in south India. PATIENTS AND METHODS: Ninety eight patients who sustained mild to moderate TBI (computed tomography (CT) scan brain showing traumatic parenchymal contusions) were the subjects of the study and the study period was from November 2003 to December 2008. APOE polymorphism status was determined by PCR technique using venous blood. Patients were assessed on follow-up with a battery of four neuropsychological tests as well as Glasgow outcome scale. RESULTS: Of the 98 patients, 20 (20%) patients had at least one APOE e4 allele. A follow-up of minimum six months was available for 73 patients. None of the 12 patients who had at least one APOE e4 allele had a poor outcome at six-month follow-up whereas 11(18%) patients without an APOE e4 allele had a poor outcome (Fisher's Exact test, P=0.192). On the neuropsychological tests, performance of patients with APOE e4 allele did not differ significantly from those without these alleles. CONCLUSION: This study does not support the current contention that the presence of APOE e4 allele should have a significant negative effect on the outcome after TBI.

Neuropsychological lateralization of brain dysfunction in children with mesial temporal sclerosis: a presurgical evaluation.

Presurgical evaluation of children with mesial temporal sclerosis has shown severe neurocognitive impairments. There is debate about lateralized material-specific deficits in memory in children with mesial temporal sclerosis. The authors examined lateralization of brain dysfunction and age appropriate development of cognitive functions in 17 children (7-15 years) with mesial temporal sclerosis who had histories of uncontrolled epilepsy. The National Institute of Mental Health and Neurosciences (NIMHANS) neuropsychological battery for children was employed and each participant's performance was compared with the norms. Results showed that the battery was sensitive to deficits in learning and memory associated with mesial temporal sclerosis. However, a lack of clearly lateralized material-specific memory deficits in children with left/right mesial temporal sclerosis was also observed. Performance on tests that assess learning, attention, working memory, and visuospatial functions was found to be below the age appropriate level. Children with mesial temporal sclerosis showed widely distributed neuropsychological deficits.

Reduction of functional brain connectivity in mild traumatic brain injury during working memory.

Working memory deficits are present in patients with mild traumatic brain injury (MTBI). Functional connectivity of different brain regions is required for adequate working memory. Brain injury is associated with disrupted connectivity due to microscopic axonal damage. In this investigation, we sought to investigate functional brain connectivity during working memory in MTBI patients. A sample of 30 MTBI patients and 30 age-, education-, and gender-matched normal controls were studied. Working memory was assessed with the Sternberg's verbal and visuo-spatial working memory tasks. Electro-encephalography (EEG) was recorded from 128 channels while subjects performed working memory tasks and during eyes closed resting condition. EEG coherence was computed in theta; lower and upper alpha; and lower and upper beta frequency bands during the encoding, retention, and retrieval stages of working memory as well as during eyes-closed rest. We found that the MTBI patients had impaired verbal and visuo-spatial working memory. The different stages of working memory were associated with poor intrahemispheric coherence in long-range (fronto-parietal) and mid-range (fronto-temporal and temporo-parietal) regions as well as poor interhemispheric coherence in the frontal and temporal regions in the MTBI patients. The deficit in coherence was present in theta, alpha, and beta frequency bands. However, the MTBI and the control group had comparable coherence values in intra- and inter-hemispheric regions during eyes closed rest. We suggest that the inter- and intra-hemispheric functional connectivity is impaired in MTBI during working memory performance.

Cognitive changes in asymptomatic drug-naïve human immunodeficiency virus type 1 clade C infection.

Asymptomatic human immunodeficiency virus (HIV) infection is associated with impaired cognitive functioning in both clade B and C infections. The nature of cognitive change longitudinally has not been studied in asymptomatic clade C infection. The present study evaluated changes in neuropsychological functioning over a 2(1/2)-year period in a cohort of HIV-1 clade C-infected asymptomatic individuals from South India. Participants with CD4 counts below 250 were started on highly active antiretroviral therapy (HAART) as per National AIDS Control Organisation NACO guidelines and hence excluded. The sample consisted of 68 patients (30 men and 38 women), with a mean age of 29.4 years (SD=5.6 years) and a mean education of 10.0 years (SD=2.7 years). A comprehensive neuropsychological assessment with 12 tests yielding 21 variables was used to examine cognitive functioning at baseline and subsequently at 6-monthly intervals for five follow-ups. Shift in CD4 and viral load categories measured by the McNemar's test indicated disease progression. Latent growth curve (LGC) modeling assessed the nature of change in cognition over the 2(1/2)-year study period. Ten variables representing attention, executive functions, and long-term memory fit the LGC model. Excepting visual working memory, the slope was nonsignificant for nine variables, indicating absence of deterioration in cognition over a 2(1/2)-year period. However, CD4 and viral load levels worsened, indicating disease progression. Asymptomatic individuals with HIV-1 clade C infection do not show any significant decline on individual neuropsychological functions over 2(1/2) years despite disease progression, as evidenced by immune suppression and viral loads.

Cognitive development in children with chronic protein energy malnutrition.

BACKGROUND: Malnutrition is associated with both structural and functional pathology of the brain. A wide range of cognitive deficits has been reported in malnourished children. Effect of chronic protein energy malnutrition (PEM) causing stunting and wasting in children could also affect the ongoing development of higher cognitive processes during childhood (>5 years of age). The present study examined the effect of stunted growth on the rate of development of cognitive processes using neuropsychological measures. METHODS: Twenty children identified as malnourished and twenty as adequately nourished in the age groups of 5-7 years and 8-10 years were examined. NIMHANS neuropsychological battery for children sensitive to the effects of brain dysfunction and age related improvement was employed. The battery consisted of tests of motor speed, attention, visuospatial ability, executive functions, comprehension and learning and memory RESULTS: Development of cognitive processes appeared to be governed by both age and nutritional status. Malnourished children performed poor on tests of attention, working memory, learning and memory and visuospatial ability except on the test of motor speed and coordination. Age related improvement was not observed on tests of design fluency, working memory, visual construction, learning and memory in malnourished children. However, age related improvement was observed on tests of attention, visual perception, and verbal comprehension in malnourished children even though the performance was deficient as compared to the performance level of adequately nourished children. CONCLUSION: Chronic protein energy malnutrition (stunting) affects the ongoing development of higher cognitive processes during childhood years rather than merely showing a generalized cognitive impairment. Stunting could result in slowing in the age related improvement in certain and not all higher order cognitive processes and may also result in long lasting cognitive impairments.

Widespread cognitive impairment in psychogenic anterograde amnesia.

A 34-year-old man without a past history of any psychiatric or neurological disorder developed severe anterograde amnesia following a psychological trauma. Initial assessment of neuropsychological functions 3 months after the psychological trauma indicated severe memory deficits for acquiring new information in both verbal and visual modalities with widespread cognitive deficits in attention, executive functions, and intellectual ability. Importantly, working and remote memory were intact. The case illustrates that psychogenic anterograde amnesia might be associated with a wider range of cognitive deficits. Possible neurobiological explanations are discussed to explain large cognitive impairments associated with anterograde psychogenic amnesia.

Sensory gating impairment in development of post-concussive symptoms in mild head injury.

Post-concussive symptoms reported by mild head injury (MHI) patients have been inadequately understood. Post-concussive symptoms reported by patients with MHI have so far been explained in terms of impairment in neurocognitive functions or deficits in modulation of flow of information. There are no studies that have looked into sensory gating impairment in MHI and its relation to post-concussive symptoms. The purpose of the present paper was to investigate the role of sensory gating impairment in post-concussive symptoms in mild head injury patients. Thirty MHI patients were evaluated for their neuropsychological functions, sensory gating deficits, and post-concussive symptoms. Neuropsychological functions were in the domain of attention, executive functions, and learning and memory. Sensory gating was assessed by Structured Interview for Assessing Perceptual Anomalies and post-concussive symptoms were assessed using the Neurobehavioral Rating Scale. Multiple regression method was used to identify predictors for post-concussive symptoms. Post-concussive symptoms were predicted by sensory gating deficits when sensory gating deficit was one of the predictors along with neuropsychological functions. Post-concussive symptoms were predicted by scores of Digit Vigilance and Digit Symbol Substitution Test, when predictors were restricted to neuropsychological functions. Sensory gating deficits were correlated with performance on Digit Symbol Substitution test. Post-concussive symptoms reported by MHI patients are the result of poor modulation of incoming sensory information.