Variational mode decomposition-based EEG analysis for the classification of disorders of consciousness.

Aberrant alterations in any of the two dimensions of consciousness, namely awareness and arousal, can lead to the emergence of disorders of consciousness (DOC). The development of DOC may arise from more severe or targeted lesions in the brain, resulting in widespread functional abnormalities. However, when it comes to classifying patients with disorders of consciousness, particularly utilizing resting-state electroencephalogram (EEG) signals through machine learning methods, several challenges surface. The non-stationarity and intricacy of EEG data present obstacles in understanding neuronal activities and achieving precise classification. To address these challenges, this study proposes variational mode decomposition (VMD) of EEG before feature extraction along with machine learning models. By decomposing preprocessed EEG signals into specified modes using VMD, features such as sample entropy, spectral entropy, kurtosis, and skewness are extracted across these modes. The study compares the performance of the features extracted from VMD-based approach with the frequency band-based approach and also the approach with features extracted from raw-EEG. The classification process involves binary classification between unresponsive wakefulness syndrome (UWS) and the minimally conscious state (MCS), as well as multi-class classification (coma vs. UWS vs. MCS). Kruskal-Wallis test was applied to determine the statistical significance of the features and features with a significance of p < 0.05 were chosen for a second round of classification experiments. Results indicate that the VMD-based features outperform the features of other two approaches, with the ensemble bagged tree (EBT) achieving the highest accuracy of 80.5% for multi-class classification (the best in the literature) and 86.7% for binary classification. This approach underscores the potential of integrating advanced signal processing techniques and machine learning in improving the classification of patients with disorders of consciousness, thereby enhancing patient care and facilitating informed treatment decision-making.

Developmental competencies, temperament, parenting practices and psychosocial adversities in children with internalising disorders - A pilot study.

Research on the aetiology of internalising disorders has focussed on biological and environmental factors, however, the role of developmental competencies that a child acquires has not been explored much. The current report aimed to understand the association among the developmental competencies, temperament, parenting practices and psychosocial adversities in internalising disorders. The sample consisted of 30 children and adolescents with internalising disorders belonging to the age group of six to 18, and one of their parents. All the participants were assessed for functional impairment, temperament, interpersonal competence, emotion regulation, executive function, self-concept, adaptive behaviour, parenting practices, life events and family environment using standardised tools. The findings revealed that positive parenting shares a negative relationship with functional impairment(ρ=-0.62; p <.001). On comparison with non-clinical samples in previous studies, interpersonal competence and self-concept were found to be at lower levels in the current sample. In conclusion, the current study indicates that children with internalising disorders differ from control groups in specific developmental competences. These findings have specific implications for intervention and research in the area of internalising disorders in children and adolescents.

Stress and coping among police personnel in South India.

Background: Police personnel experience the highest levels of stress due to the nature and demands of work. Though many researchers have studied these variables quantitatively, there is a lack of qualitative study, particularly in India. Methods: A qualitative study has been carried out to explore the stress and coping strategies of police personnel. This study conducted in-depth interviews with ten police personnel and three focus group discussions with 22 police personnel. Results: Thematic analysis revealed five themes: family stressor, personal stressor, work stressor, and adaptive and maladaptive coping. Inability to take leave, multi-tasking, unscheduled excessive working hours, inability to spend time with the family members, and lack of basic amenities to meet personal hygiene were significant factors for their high level of stress. Conclusion: The results reinforce the need for mitigating the impact of stress by using positive coping strategies and social support resources, which could be achieved through capacity building and mental health programs.

Development and validation of a Smartphone Impact Scale among healthcare professionals.

OBJECTIVES: Smartphone overuse is prevalent among healthcare professionals. There is no standard scale that can measure the impact of smartphone usage on healthcare professionals. This study aimed to develop and validate a tool, the Smartphone Impact Scale (SIS), that can effectively measure the use of smartphone among healthcare professionals. METHODS: We developed a generic instrument to study the impact of smartphone usage among healthcare professionals. A total of 1436 healthcare professionals from various regions of KSA participated in this study through an online questionnaire-based survey. The psychometric properties of the SIS were developed using content validity index (CVI), factor analysis, internal consistency, and test-retest reliability analysis. RESULTS: A 23-item scale was selected for reliability and validity analysis. The average CVI was found to be 0.824. The internal consistency with Cronbach's alpha value was 0.91, and test-retest reliability was 0.85. The Cronbach's alpha values for Factors 1 and 2 were 0.875 and 0.803, respectively. The confirmatory factor analysis indices were as follows: root mean square of approximation = 0.0710, comparative fit index = 0.861, Tucker-Lewis index = 0.845, and the coefficient of determination = 0.969. The correlation between two factors was 0.66. After factor analysis, we developed a final questionnaire with 23 items. CONCLUSIONS: Our SIS showed a three-factor structure and appropriate psychometric characteristics. Due to its adequate reliability and validity, SIS can be conveniently used to evaluate the impact of smartphone usage on healthcare professionals.

Ganglioside complex antibodies in an Indian cohort of Guillain-Barré syndrome.

BACKGROUND: Antibodies against ganglioside complexes (GSCs) are associated with various clinical features and subtypes of Guillain-Barré syndrome (GBS). METHODS: One-hundred patients were evaluated for antibodies to GSCs formed by combination of GM1, GM2, GD1a, GD1b, GT1b, and GQ1b using manual enzyme linked immuno-sorbent assay (ELISA). RESULTS: Twenty-six patients were GSC antibody-positive, most frequent being against GM1-containing GSC (76.9%). Gender distribution, mean age, symptom-duration, antecedent events, electrophysiological subtypes, requirement for mechanical ventilation, and median duration of hospital stay were comparable between the GSC antibody-positive and negative groups. There was no association between specific GSC antibody and electrophysiological subtypes or clinical variants. After controlling for false discovery rate (FDR) using the Benjamini-Hochberg method, the number of subjects who improved in overall disability sum score, modified Erasmus GBS outcome score, and neuropathy symptom score at discharge was significantly higher in the GSC antibody-positive group. Improvements in Medical Research Council sum scores and Hughes Disability Scale during the hospital stay between the GSC antibody-positive and negative groups were not significantly different after controlling for FDR. CONCLUSIONS: The GSC antibody-positive group had better outcome at hospital discharge in some of the disability scores. Pathophysiological pathways among patients without GSC antibodies may be different and this requires further evaluation.

Maternal Immune Activation Causes Schizophrenia-like Behaviors in the Offspring through Activation of Immune-Inflammatory, Oxidative and Apoptotic Pathways, and Lowered Antioxidant Defenses and Neuroprotection.

Schizophrenia is a complex neuropsychiatric disorder, influenced by a combined action of genes and environmental factors. The neurodevelopmental origin is one of the most widely recognized etiological models of this heterogeneous disorder. Environmental factors, especially infections during gestation, appear to be a major risk determinant of neurodevelopmental basis of schizophrenia. Prenatal infection may cause maternal immune activation (MIA) and enhance risk of schizophrenia in the offspring. However, the precise mechanistic basis through which MIA causes long-lasting schizophrenia-like behavioral deficits in offspring remains inadequately understood. Herein, we aimed to delineate whether prenatal infection-induced MIA causes schizophrenia-like behaviors through its long-lasting effects on immune-inflammatory and apoptotic pathways, oxidative stress toxicity, and antioxidant defenses in the brain of offspring. Sprague-Dawley rats were divided into three groups (n = 15/group) and were injected with poly (I:C), LPS, and saline at gestational day (GD)-12. Except IL-1ß, plasma levels of IL-6, TNF-α, and IL-17A assessed after 24 h were significantly elevated in both the poly (I:C)- and LPS-treated pregnant rats, indicating MIA. The rats born to dams treated with poly (I:C) and LPS displayed increased anxiety-like behaviors and significant deficits in social behaviors. Furthermore, the hippocampus of the offspring rats of both the poly (I:C)- and LPS-treated groups showed increased signs of lipid peroxidation, diminished total antioxidant content, and differentially upregulated expression of inflammatory (TNFα, IL6, and IL1ß), and apoptotic (Bax, Cas3, and Cas9) genes but decreased expression of neuroprotective (BDNF and Bcl2) genes. The results suggest long-standing effects of prenatal infections on schizophrenia-like behavioral deficits, which are mediated by immune-inflammatory and apoptotic pathways, increased oxidative stress toxicity, and lowered antioxidant and neuroprotective defenses. The findings suggest that prenatal infections may underpin neurodevelopmental aberrations and neuroprogression and subsequently schizophrenia-like symptoms.

Phenotypic Variability of Essential Tremor Based on the Age at Onset.

BACKGROUND: Essential tremor (ET) is reported to have a bimodal distribution of age at onset (AAO) with phenotypic variability based on the AAO. This study aims to explore the distribution of AAO based on mathematical modeling and ascertain the differences, if any, in the clinical features of groups. METHODS: A chart review was conducted for 252 patients with ET diagnosed based on the Consensus statement of the Movement Disorder Society on Tremor. Finite mixture modeling was performed to identify groups of the cohort based on the AAO. RESULTS: Three groups were defined: early onset (EO): AAO ≤ 22 years, n = 63, intermediate onset (IO): 23 ≤ AAO ≤ 35 years, n = 43, and late onset (LO): AAO ≥ 36 years, n = 146. There were no significant differences related to family history or responsiveness to alcohol. The EO group had significantly higher prevalence of upper limb and lower limb tremor. Head tremor and voice tremor was more prevalent in the IO and LO groups. Cerebellar signs showed a significant increase with an increase in AAO. CONCLUSIONS: ET shows significant phenotypic variability based on the AAO. Patients with an early AAO are more likely to develop an appendicular tremor, whereas the probability of axial tremor and cerebellar signs increases with increasing AAO.

Determinants of antenatal care utilization in India: a spatial evaluation of evidence for public health reforms.

OBJECTIVE: The objective is to examine the spatial variations and to identify the determinants of antenatal care (ANC) utilization while controlling for the spatial dependence in the data. STUDY DESIGN: This is an ecological study on ANC utilization data from District Level Household Survey-4 (2012-2013) in India. METHODS: A secondary data analysis was performed on the derived data. The unit of analysis in this ecological study was 275 districts from 20 states of India. The study comprises ever married women of reproductive age. Determinants of ANC utilization were obtained using ordinary least square (OLS), spatial lag, and spatial error models. Model adequacy check was performed using the Akaike information criterion, R-squared, log likelihood, and Schwarz criterion. The software used is GeoDa and Quantum Geographic Information System. RESULTS: The presence of spatial autocorrelation (Moron's I = 0.6210) enforces the usage of geographic properties while modeling. The geographic clustering of low-rate districts was observed in states in Northeast India. In the present study, the model adequacy check reveals that the spatial error model performs better than the spatial lag and OLS models. The spatial pattern of the percentage of pregnant women with full ANC was observed to be associated with literacy (P = 0.04), birth order (P < 0.001), Janani Suraksha Yojana beneficiaries (P = 0.048), and availability of health infrastructure, staff, and services (P = 0.023). CONCLUSIONS: The present study findings provide valuable insights into factors affecting ANC utilization. In addition to available ANC services, customized safe motherhood interventions and region-specific awareness programs would enhance the utilization, ensuring better maternal and child health.

Factors Associated With Social Isolation Among the Older People in India.

OBJECTIVE: To explore the factors associated with social isolation among older people using the data from Building Knowledge Base on Population Ageing in India (BKPAI) survey. METHODS: Multiple logistic regression and classification and regression tree (CART) analysis were used to identify the factors associated with social isolation using data from BKPAI survey. An individual was regarded as socially isolated if the response was "never" to all 4 activities in the last 12 months: (1) attending public meeting, (2) attending any group/club/organizational meeting, (3) attending any religious program, and (4) visiting friends or relatives. RESULTS: Among 9836 older people, 19.7% were observed to be socially isolated. From multiple logistic regression, age (odds ratio [OR] = 1.85 for age 80 to 89 years and OR = 2.67 for age ≥90), religion (OR = 0.54 for Christians compared to Hindus), duration of stay in current home (OR = 0.64 for 6-10 years compared to >10 years of stay), number of activities of daily living (ADLs) for which the assistance was needed (OR = 2.09 for 1 or 2, OR = 3.14 for 3 or 4, and OR = 12.05 for 5 or 6), and Alzheimer's disease (OR = 1.65) were identified as factors associated with social isolation. Number of ADL for which the assistance was needed and self-reported health status were the factors identified through CART analysis. DISCUSSION: Requiring help in performing ADL, advancing age, and Alzheimer's disease were the likely factors for socially isolation among elderly patients in this surveyed population.

Sociocultural Determinants of Infertility Stress in Patients Undergoing Fertility Treatments.

INTRODUCTION: Involuntary childlessness is a distressing condition that has considerable social implications in developing nations. AIM: The present study aims to investigate the less known sociocultural determinants of infertility stress in patients undergoing assisted conception and reproductive treatments. METHODS: This cross-sectional research was conducted on 300 men and women with primary infertility. The profile of sociodemographic variables, clinical variables, and sociocultural variables was collected using a locally devised questionnaire. Infertility stress was assessed using the psychological evaluation test. STATISTICAL ANALYSIS: Research data were analyzed using SPSS 15. Chi-square test is used for univariate analysis. Multiple logistic regression with enter method is used to examine the association between infertility stress and sociocultural variables. RESULTS: The findings suggest that in both men and women, low spousal support, financial constraints, and social coercion in early years of marriage predicts infertility distress. Peer-support neither predicts nor protects against distress. DISCUSSION: Family acceptance and social security for infertility is low. Stigma, concealment, and discrimination among men are reported to be high. Distress is three times greater in women with overinvolved family members who had unrealistic expectations from treatments. Taking continuous cycles of fertility treatments seems unaffordable for most patients. Subfertile individuals were socially perceived to be deprived, blemished, incomplete, and sexually incompetent. CONCLUSION: Data from this investigation, provides a glimpse into sociocultural aspects of infertility. The findings may be useful for identifying targets for individual and family-focused psychological interventions for distress reduction in infertility.

Illness Cognitions, Anxiety, and Depression in Men and Women Undergoing Fertility Treatments: A Dyadic Approach.

BACKGROUND: Emotional response to infertility is mediated by numerous interrelated psychological variables such as personality, health perceptions, cognitive appraisals, coping, and social support. While men and women respond to infertility differently, illness cognitions are a vital component of their emotional adjustment. The aim of this study is to compare the infertile men and women undergoing fertility treatments on perceived distress, helplessness, acceptance, benefits, anxiety, and depression. MATERIALS AND METHODS: Eighty-one infertile couples, undergoing intrauterine insemination participated in the study. They were assessed on the presence of infertility distress using the fertility problem inventory, for psychiatric morbidity using the Mini International Neuropsychiatric Interview, for affective disturbances using the Hamilton Anxiety and Depression scales, and for illness cognitions using the Illness Cognition Questionnaire. STATISTICAL ANALYSIS: Data are analyzed using SPSS version 15. The paired sample t-test is performed for assessing differences on normally distributed data. The Wilcoxon Signed-Rank test is performed for assessing differences in medians obtained on data that was skewed. RESULTS AND DISCUSSION: Infertile women (wives) were more emotionally distressed, anxious, and depressed than men (husbands). Gender-wise differences were found for perceptions of helplessness and acceptance of infertility. Infertility was perceived to be a nonbeneficial event for both partners investigated. CONCLUSION: Negative cognitions and affective disturbances may contribute to higher treatment burden in couples seeking-assisted conception. The present study suggests that psychosocial intervention for couples plays a central role and should be integrated within the conventional treatments for infertility.

Outcomes of Structured Psychotherapy for Emotional Adjustment in a Childless Couple diagnosed with Recurrent Pregnancy Loss: A Unique Investigation.

Losing a much-awaited pregnancy and an unborn child, time and again is known to be a painful experience in recurrent miscarriage or pregnancy loss (RPL). Literature on psychological consequences of RPL is abundant. Nonetheless, application of psychological intervention in RPL remains to be an overlooked area. Using a repeated measures design and standardized psychological measures, this case study assessed the outcomes of mindfulness-based therapy administered with routine fertility treatment in a couple with the history of recurrent miscarriages and secondary infertility. Data analysis was done using clinically significant change and analysis of graphic trends. Psychotherapy helped the couple initiate a meaningful discourse with the stress following miscarriage, uncertainty of pregnancy, and fertility-related emotional struggles by mindfully transforming stressors into less painful experiences. Control studies on applications of such therapies are needed to provide definitive answers to "what works, for whom, when, and how," with distressed patients experiencing RPL.

What Factors Influence Union and Refracture of Congenital Pseudarthrosis of the Tibia? A Multicenter Long-term Study.

OBJECTIVE: To identify factors influencing union of congenital pseudarthrosis of the tibia (CPT), refractures, and integrity of the tibia at maturity. METHODS: Data of 119 children operated for Crawford-type IV CPT and followed-up till skeletal maturity were analyzed. Logistic regression and recursive partitioning analyses were used to test associations between several variables and the outcome. RESULTS: Primary union occurred in 86% of children. At maturity, 69% remained soundly united. The odds ratio for failure of primary union was 3.89 (95% confidence interval, 1.05-14.40; P=0.042) when bone morphogenetic protein was used, and children who had a combination of the Ilizarov technique and intramedullary nailing were at risk for unsound union at maturity (odds ratio, 6.19; 95% confidence interval, 1.24-30.83; P=0.026). No other association reached statistical significance. On recursive partitioning, use of the Ilizarov technique, transfixing the ankle and subtalar joints, use of cortical graft and not operating on the fibula were associated with a better outcome; use of bone morphogenetic protein and combining intramedullary nailing with the Ilizarov technique were associated with poor results. CONCLUSIONS: A larger sample is needed to confirm which factors truly influence the outcome of CPT. This may be feasible if data are collected prospectively through a multicenter registry.

Spatio-temporal assessment of infant mortality rate in India.

BACKGROUND: Infant mortality rate (IMR) is globally identified by the policymakers as the marker of health of a population. OBJECTIVES: This study aimed to detect the change in hotspots of IMR in Indian states from the year 2000 to 2012, identify hotspots of IMR at district level in selected states from each of the six regions of India and determine the potential predictors of IMR after accounting for spatial autocorrelation. METHODS: Ecological study design was used to analyze state and district level data on IMR of India. For the first objective, the data were obtained from Sample Registration System. For the second objective, we classified India into six regions and selected a state in each region that had the highest IMR. The district level data on IMR and potential predictors were obtained from surveys, namely, Annual Health Survey, District Level Household and Facility Survey and Census. Spatio-temporal hotspots of IMR were examined using local indicators of spatial association statistic. Spatial regression was used to identify the potential predictors of IMR after accounting for spatial autocorrelation. RESULTS: Temporal hotspots of IMR were found in the central part of India. Spatial hotspots were identified in districts of Uttar Pradesh. A negative association of IMR existed with female literacy rate, mothers receiving antenatal checkup (%), and people living in urban areas (%). CONCLUSION: IMR continues to be a problem in the states that have previously shown to be poor performing. Certain districts within these states need emphasis for focused activities.

Treatment of Acute Promyelocytic Leukemia with Single Agent Arsenic Trioxide: Experience from a Tertiary Care Center in India.

APML is a highly curable hematological malignancy which is treated with differentiation agents and chemotherapy. The morbidity caused by chemotherapy in the treatment of APML is a great cause of concern. We treated 12 patients with newly diagnosed APML with single agent arsenic trioxide between 2010 and 2014 irrespective of risk stratification. Out of 12 patient 2 patients died during induction. All the ten patients who completed induction, completed their consolidation and maintenance without any delays. One out of these ten patients relapsed 10 months after treatment. The remaining nine patients (80 %) are in molecular remission and are under regular follow up. The toxicity with arsenic was negligible and was very well tolerated. Hence arsenic trioxide as single agent can be offered as a standard alternative regimen to ATRA based chemotherapy in patients with economic constraints.

A Randomized controlled trial to evaluate the impact of a Nurse Navigator Programme on outcomes of people with breast cancer: study protocol.

AIM: To evaluate the effectiveness of a Nurse Navigator Programme on anxiety, psychological distress and quality of life in people with breast cancer. BACKGROUND: Breast cancer is the most frequently detected malignancy and a major cause of cancer death among women around the world. The lengthy course of illness from initial diagnosis to treatment and subsequent follow-up causes deterioration in physical, psychological and social status among patients. Nurses have a major role in cancer care. As women with breast cancer have to undergo various treatment modalities, continued care by a pivot nurse is thought to enhance treatment adherence. Limited studies have been reported from developing countries on Nurse Navigation Programmes. DESIGN: A Stratified Randomized controlled trial with repeated measures. METHODS: One hundred and twenty newly diagnosed women with breast cancer admitted to surgery wards of a tertiary care hospital in South India will be recruited. (Project funded in Octo"ber 2014). Women are randomly allocated to a control and intervention group. The outcome variables are anxiety, psychological distress and quality of life. Data on outcome measures will be collected at five different time points: before surgery, at discharge, beginning of adjuvant therapy, middle of adjuvant therapy and at the end of adjuvant therapy. DISCUSSION: This study may give evidence on the effectiveness of a Nurse Navigator Programme for women with breast cancer. If significant effects were detected, the programme could be integrated into hospital services to improve the patient care.

Postpartum related morbidities among women visiting government health facilities in Udupi Taluk, Karnataka, India.

BACKGROUND: Maternal morbidities are considered a leading contributor to the burden of disease among women. Especially, if postpartum morbidities are left untreated, this can cause a negative impact on the quality of life. The study was conducted to determine the proportion and types of postpartum morbidities among women visiting government health facilities in Udupi Taluk, Karnataka and to find out the association between the morbidities and various factors. SUBJECTS AND METHODS: A cross-sectional study was conducted in various government hospitals in Udupi Taluk, consisted of 229 postpartum women. These subjects were selected from mothers who accompanied their children for immunization from February 2013 to July 2013 using purposive sampling technique. Multiple logistic regression analysis was used to find out the association between the morbidities and various factors using SPSS version 15. RESULTS: Among 112 (48.9%) women who experienced postpartum morbidities, back pain (23.6%), and perineal pain (15.7%) were most commonly reported physical morbidities. Similarly, anxiety (10%) and irritability (7.9%) were the most common psychological problems. Demographic factors such as religion 2.4 (95% confidence interval [CI] 1.1, 5.4) and occupation 2.5 (95% CI 1.1, 5.9) were associated with the morbidities. Likewise, obstetric factors such as place of delivery 1.5 (95% CI 0.8, 2.9) and type of delivery 1.9 (95% CI 1.0, 3.6) were also associated with various morbidities. CONCLUSIONS: The findings showed a high proportion of postpartum morbidities being reported in our study settings. These observation priorities a need of health program for early recognition, treatment and improving awareness of postpartum morbidities among near mothers.

Prevalence and predictors of infertility-specific stress in women diagnosed with primary infertility: A clinic-based study.

BACKGROUND: According to the existing literature on infertility, stress appears to be inevitably associated with infertility diagnosis and treatment in sub-fertile individuals. The epidemiological data on the prevalence and predictors of infertility-specific stress in cultural specific scenario are scarce. The objective of the present study was to estimate the prevalence of infertility-specific stress and identify predictors of infertility-specific stress in women diagnosed with primary infertility. MATERIALS AND METHODS: This cross-sectional study was conducted on 300 infertile married women, diagnosed with primary infertility. The tools used for the assessment were "semi-structured questionnaire" compiled by the authors, "ICD-10 Classification of Mental and Behavioral Disorders (Clinical Descriptions and Diagnostic Guidelines)," and "Psychological Evaluation Test for infertility." STATISTICAL ANALYSIS: Data were analyzed using SPSS (version 15). Chi-square test was used for univariate analysis followed by multiple logistic regressions between stress and the predictor variables. RESULTS AND DISCUSSION: The prevalence of stress among women was 80%. Univariate analysis revealed that predictors of stress were years of marital life, duration of infertility, infertility type, history of gynecological surgery, cycles of ovulation induction with timed intercourse and intra-uterine inseminations, present and past psychiatric morbidity, coping difficulties, gynecological diagnosis, and severity of premenstrual dysphoria. Multivariate analysis showed leading associations of stress with infertility type and coping difficulties.

Impact of pixel intensity correlations on statistical inferences of expression levels in cDNA microarray experiments.

In a cDNA microarray experiment, the final measurement is intensity ratio at a spot in the microarray chip. The objective of the present study is to estimate the uncertainty associated with the final intensity ratio at each spot in cDNA microarray chips and also to explore the role of pixel intensity correlations in statistical inferences of gene expression levels. We estimate uncertainty at each spot using the theory of error propagation under two different situations: (1) when there is no correlation between pixel intensities and (2) when the pixel intensities are positively correlated. The inverses of these estimated uncertainties are used as weights in downstream analysis to test the significance of each gene. The analysis was verified on a data downloaded from the GEO database. Our study shows that the uncertainty and statistical inference of gene expression levels depend on correlation between pixel intensities within a spot.