Prevalence of mild behavioural impairment and its association with cognitive and functional impairment in normal cognition, mild cognitive impairment, and mild Alzheimer's dementia

BACKGROUND

Mild behavioural impairment (MBI) is an emergent and persistent neuropsychiatric symptom (NPS) in subjects aged 50 and older who are at risk for cognitive decline. We examined the prevalence of MBI across the spectrum from cognitively normal (CN), mild cognitive impairment (MCI), to dementia, and further investigated the association between the MBI domain and cognitive and functional impairment.

METHOD

MBI was assessed in 2337 elderly patients in the Alzheimer's Disease Neuroimaging Initiative database (mean age, 73.04 years; 52.8% male). Among the subjects, 868 (37.1%) had normal cognition, 1066 (45.6%) had MCI, and 403 (17.2%) had mild Alzheimer's dementia (AD). MBI was evaluated in accordance with the Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment diagnostic criteria for MBI, utilising the Neuropsychiatric Inventory. We compared the prevalence of the MBI domain with CN using multinominal logistic regression analysis and further quantified the magnitude of the association between MCI/AD and the MBI domains by calculating the population attributable risk (PAR). We assessed the association between the MBI domains and cognitive and functional impairment using simultaneous linear regression analysis.

RESULTS

The most common MBI domains in each diagnostic group were affective dysregulation followed by impulse dyscontrol, decreased motivation, social inappropriateness, and abnormal perception or thought content. The PARs for MBI domains in subjects with MCI or AD were respectively: 16.60% and 24.34% for affective dysregulation; 3.72% and 18.06% for impulse dyscontrol; 4.78% and 14.13% for decreased motivation, 1.91% and 2.29% for social inappropriateness; and 0.68% and 3.85% for abnormal perception or thought content. All MBI domains except for social inappropriateness were significantly associated with a higher 11-item Alzheimer's Disease Assessment Scale-Cognitive Subscale total score. All MBI domains were significantly associated with a higher Functional Activities Questionnaire total score.

CONCLUSION

Our findings show that MBI is highly prevalent across subjects with CN, MCI, and AD and is associated with cognitive and functional decline. MBI could be a crucial clinical phenotype relevant to the risk of cognitive and functional impairment, and provides a useful dimension pertinent to diagnostic approaches.

A Unique Delusion with Depression in Early Stage of Neurocognitive Disorder Due to Vascular Disease: Considerations for Clinicians

As global aging becomes more prominent, neurocognitive disorders (NCD) incidence has increased. Patients with NCD usually have an impairment in one or more cognitive domains, such as attention, planning, inhibition, learning, memory, language, visual perception, and spatial or social skills. Studies indicate that 50-80% of these adults will develop neuropsychiatric symptoms (NPS), such as apathy, depression, anxiety, disinhibition, delusions, hallucinations, and aberrant motor behavior. The progression of NCD and subsequent NPS requires tremendous care from trained medical professionals and family members. The behavioral symptoms are often more distressing than cognitive changes, causing caregiver distress/depression, more emergency room visits and hospitalizations, and even earlier institutionalization. This signifies the need for early identification of individuals at higher risk of NPS, understanding the trajectory of their NCD, and exploring treatment modalities. In this case report and review, we present an 82-year-old male admitted to our facility for new-onset symptoms of depression, anxiety, and persecutory delusions. He has no significant past psychiatric history, and his medical history is significant for extensive ischemic vascular disease requiring multiple surgeries and two episodes of cerebrovascular accident (CVA). On further evaluation, the patient was diagnosed with major NCD, vascular subtype. We discuss differential diagnoses and development of NPS from NCD in order to explain the significance of more thorough evaluation by clinicians for early detection and understanding of NCD prognosis.

Eating problems in people with dementia with Lewy bodies: Associations with various symptoms and the physician's understanding

OBJECTIVES

Eating problems frequently occur in people with dementia with Lewy bodies (DLB), but few studies have investigated the clinical background of this phenomenon. This study examined the relationship between eating problems and various symptoms of DLB and the relation between the treatment needs for DLB people with eating problems and the understanding of their eating problems by caregivers and physicians.

DESIGN, MEASUREMENTS, AND PARTICIPANTS

This was a subanalysis of a cross-sectional, questionnaire-based survey study. Two hundred sixty-one subjects with DLB were divided into subjects with or without eating problems. Logistic or linear regression analysis was used to investigate the factors influencing eating problems. The treatment needs of DLB people for their eating problems and the understanding of these needs by caregivers and physicians were calculated as participant-caregiver and participant-physician kappa coefficient.

RESULTS

Of the 261 participants, 27% suffered from eating problems. The presence of eating problems in participants with DLB was related to depression (p = 0.01, OR : 2.19, 95% CI: 1.23-3.91) and apathy (p = 0.01, OR 2.15, 95% CI: 1.20-3.87), while the worsening of eating problems was related to dysphagia (β = 0.24, p = 0.03), apathy (β = 0.23, p = 0.05), and nighttime behavior (β = 0.24, p = 0.04). The participant-physician kappa coefficient for physician understanding of constipation, weight loss, dysphagia, weight gain, and increase in appetite was significantly lower than the corresponding participant-caregiver kappa coefficient (p-value of five symptoms < 0.01).

CONCLUSIONS

Physicians need to pay more attention to eating problems and their neuropsychiatric background in the long-term support and management of DLB subjects.

Cardiometabolic Effects of Antipsychotics in Challenging Behavior and Neuropsychiatric Symptoms in Patients With Intellectual Disability

Introduction Despite the well-established association between antipsychotics and metabolic adverse effects in psychiatric disorders, the variable influence of long-term and off-label antipsychotic medication on behavioral disorders has not been investigated in detail. Objective To clarify the impact of antipsychotic use on challenging behavior (CB) and neuropsychiatric symptoms (NPS), we evaluated the clinical findings and cardiometabolic effects in individuals with intellectual disability (ID) hospitalized in our residential facility for profoundly disabled patients. Patients and methods A total of 130 individuals hospitalized in our residential facility were retrospectively investigated and divided into two groups - individuals with and without CB and NPS. Antipsychotics (first- and second-generation antipsychotics) are prescribed to all individuals in the CB and NPS-positive ID group. Conversely, antipsychotics were not prescribed to any individuals in the CB- and NPS-negative ID groups. To investigate the cardiometabolic effects of antipsychotics, the following metabolic parameters were measured: body weight (BW), total calorie intake per day, body mass index (BMI), blood pressure, serum lipid levels (total cholesterol, high-density lipoprotein cholesterol, and triglyceride), and corrected QT interval (QTc) of electrocardiogram (ECG). The etiology of disabilities, level of ID, severity of motor disability, and presence or absence of epilepsy were also examined. Results Two main results were derived: (1) Autism spectrum disorder was the most predominant etiology in individuals with CB and NPS who were prescribed antipsychotics, and (2) the mean values of metabolic parameters were all normal in both medicated and nonmedicated individuals, but the total calorie intake was significantly higher in individuals who were prescribed antipsychotics. Conclusions Our investigation demonstrated that in individuals with an adequate energy intake, most metabolic parameters can be maintained within normal limits. We suggest that body weight control is the primary step in avoiding the cardiometabolic adverse effects of antipsychotics in intellectually disabled individuals with CB and NPS.

Analysis of positron emission tomography hypometabolic patterns and neuropsychiatric symptoms in patients with dementia syndromes

AIMS

To estimate the proportions of specific hypometabolic patterns and their association with neuropsychiatric symptoms (NPS) in patients with cognitive impairment (CI).

METHODS

This multicenter study with 1037 consecutive patients was conducted from December 2012 to December 2019. ¹⁸ F-FDG PET and clinical/demographic information, NPS assessments were recorded and analyzed to explore the associations between hypometabolic patterns and clinical features by correlation analysis and multivariable logistic regression models.

RESULTS

Patients with clinical Alzheimer's disease (AD, 81.6%, 605/741) and dementia with Lewy bodies (67.9%, 19/28) mostly had AD-pattern hypometabolism, and 76/137 (55.5%) of patients with frontotemporal lobar degeneration showed frontal and anterior temporal pattern (FT-P) hypometabolism. Besides corticobasal degeneration, patients with behavioral variant frontotemporal dementia (36/58), semantic dementia (7/10), progressive non-fluent aphasia (6/9), frontotemporal lobar degeneration and amyotrophic lateral sclerosis (3/5), and progressive supranuclear palsy (21/37) also mostly showed FT-P hypometabolism. The proportion of FT-P hypometabolism was associated with the presence of hallucinations (R = 0.171, p = 0.04), anxiety (R = 0.182, p = 0.03), and appetite and eating abnormalities (R = 0.200, p = 0.01) in AD.

CONCLUSION

Specific hypometabolic patterns in FDG-PET are associated with NPS and beneficial for the early identification and management of NPS in patients with CI.

A case of V180I genetic mutation Creutzfeldt Jakob disease (CJD) with delusional misidentification as an initial symptom

An 84-year-old woman who had been diagnosed as having dementia with Lewy body (DLB) upon initial examination exhibited cognitive impairments and person delusional misidentification (DMS): she transiently claimed that her spouse was a stranger. She was re-examined at the age of 89 years; her frequency of speech and activities of daily living had both decreased, leading to verbal communication difficulties complicated by sensory aphasia, and brain diffusion-weighted (DW) magnetic resonance imaging (MRI) showed cortical hyperintensities in some areas of both hemispheres. About 4 months later, the DW high-intensity areas were observed to have expanded into diffuse cortical areas. While the clinical features of Creutzfeldt Jakob disease (CJD) (myoclonus; ataxia; parkinsonism; rapidly progressive cognitive impairments; periodic sharp discharges on electroencephalograms) were not observed, a genetic analysis of the prion protein (PRNP) gene, which was performed because of a family history of dementia, revealed a V180I mutation (heterozygosis: valine/isoleucine) suggesting genetic CJD (g-CJD). Her activity progressively decreased, reaching akinetic mutism about 11 months after the re-examination. Finally, she suffered from severe bedsores and died from aspiration pneumonia at the age of 90 years. The present report describes the first case of person DMS as an initial neuropsychiatric symptom for V180I g-CJD; the typical long-term clinical symptoms of CJD were not observed in this patient. The inclusion of person DMS as an initial clinical symptom and the presence of expansive cortical hyperintensity areas may be useful for clinicians attempting to diagnosis V180I g-CJD in patients with elusive symptoms.

Association Between Caregivers' Burden and Neuropsychiatric Symptoms in Female Patients with Alzheimer's Disease with Varying Dementia Severity

Purpose

This study examined the attributes causing higher burdens for caregivers caring for female patients with Alzheimer’s disease by analyzing a combination of various variables, including demographic data, dementia severity, and neuropsychiatric symptoms.

Patients and Methods

This study included 99 female patients with Alzheimer’s disease who were cared for by the dementia collaborative care team at Changhua Christian Hospital, Taiwan. Neuropsychiatric symptoms used in this study included affections (9 types), behavior symptoms (9 symptoms), and psychological symptoms (3 symptoms). The Apriori algorithm was employed to identify association rules that reveal the relationships among demographic data, dementia severity, neuropsychiatric symptoms, and caregivers’ burden.

Results

A total of 185 rules were determined, including 51 rules with little or no burden, 108 rules with mild to moderate burden, and 26 rules with moderate to severe burden. The major findings are as follows. Neuropsychiatric symptoms were associated with varying degrees of caregivers’ burden among female patients aged 75 to 84 years with mild dementia. Crying spells and aggression were specifically associated with a moderate to severe burden. Delusion was associated with a mild to moderate and moderate to severe burden. Dysthymia and depression were associated with little or no burden to moderate to severe burden.

Conclusion

Clinicians can provide early interventions to reduce the burden of caregivers caring for female patients with Alzheimer’s disease and can refer caregivers for timely assistance to reduce their burden.

Female dominance of both spatial cognitive dysfunction and neuropsychiatric symptoms in a mouse model of Alzheimer's disease

Alzheimer’s disease (AD) is a prevalent neurological disorder affecting memory function in elderly persons. Indeed, AD exhibits abnormality in cognitive behaviors and higher susceptibility to neuropsychiatric symptoms (NPS). Various factors including aging, sex difference and NPS severity, are implicated during in development of AD. In this study, we evaluated behavioral abnormalities of AD model, PDAPP transgenic mice at young age using the Morris Water Maze test, which was established to assess hippocampal-dependent learning and memory. We found that female AD model mice exhibited spatial learning dysfunction and highly susceptible to NPS such as anxiety and depression, whereas spatial reference memory function was comparable in female PDAPP Tg mice to female wild type (WT) mice. Spatial learning function was comparable in male AD model mice to male WT mice. Multiple regression analysis showed that spatial learning dysfunction was associated with NPS severity such as anxiety and depression. Furthermore, the analysis showed that spatial reference memory function was associated with status of depression, but not anxiety. Thus, these results suggest female dominance of spatial learning dysfunction in the AD model mice accompanying increased NPS severity. The understandings of AD model may be useful for the development of therapeutic agents and methods in human AD.

Neuropsychiatric symptoms in limbic-predominant age-related TDP-43 encephalopathy and Alzheimer's disease

There is clinical overlap between presentations of dementia due to limbic-predominant age-related TDP-43 encephalopathy (LATE) and Alzheimer's disease. It has been suggested that the combination of Alzheimer's disease neuropathological change (ADNC) and LATE neuropathological changes (LATE-NC) is associated with greater neuropsychiatric symptom burden, compared to either pathology alone. Longitudinal Neuropsychiatric Inventory and psychotropic medication prescription data from neuropathologically diagnosed pure ADNC (n = 78), pure LATE-NC (n = 14) and mixed ADNC/LATE-NC (n = 39) brain bank donors were analysed using analysis of variance and linear mixed effects regression models to examine the relationship between diagnostic group and neuropsychiatric symptom burden. Nearly all donors had dementia; three (two pure LATE-NC and one pure ADNC) donors had mild cognitive impairment and another two donors with LATE-NC did not have dementia. The mixed ADNC/LATE-NC group was older than the pure ADNC group, had a higher proportion of females compared to the pure ADNC and LATE-NC groups, and had more severe dementia versus the pure LATE-NC group. After adjustment for length of follow-up, cognitive and demographic factors, mixed ADNC/LATE-NC was associated with lower total Neuropsychiatric Inventory and agitation factor scores than pure ADNC, and lower frontal factor scores than pure LATE-NC. Our findings indicate that concomitant LATE pathology in Alzheimer's disease is not associated with greater neuropsychiatric symptom burden. Future longitudinal studies are needed to further investigate whether mixed ADNC/LATE-NC may be protective against agitation and frontal symptoms in dementia caused by Alzheimer's disease or LATE pathology.

The Impact of the COVID-19 Pandemic on Alzheimer's Disease and Other Dementias

Introduction: Numerous countries went into lockdown to contain the COVID-19 outbreak, which has impeded follow-up of chronic diseases, such as cognitive impairment (CI). Cognitive and neuropsychiatric changes during the COVID-19 pandemic are neglected in China, which is the world's whistleblower. To investigate the cognitive and neuropsychologic changes in CI, as well as the proportions of rapid cognitive decline (RCD) before and during the COVID-19 pandemic to provide clinical evidence for CI intervention during a public health emergency. Methods: We performed a descriptive and retrospective study based on medical records from the memory clinic of Tianjin Dementia Institute collected through face-to-face evaluations. Information of 205 patients with CI, including patients with mild cognitive impairment and dementia, of whom 131 with Alzheimer's disease (AD) were analyzed and compared to a control group before the COVID-19 pandemic. Results: Among the 205 CI patients, the scores on the Chinese Mini Mental State Examination (C-MMSE), the Montreal Cognitive Assessment (MoCA), activities of daily living (ADLs), and the global Neuropsychiatric Inventory (NPI) were significantly different at the baseline and follow-up evaluations (p < 0.05) after 14.07 (±2.87) months. The same findings were recorded among AD patients, and they exhibited more sleep disturbances at the follow-up than at baseline (32.8 vs. 20.6%, p = 0.035). When compared to the control group, slightly worse performance of cognitive, -1.00 (-4.00, 1.00) from the C-MMSE, -1.00 (-2.00, 0.00) on the MoCA, 1.00 (0.00, 9.00) on ADLs and neuropsychological 0.00 (-1.00, 3.50) on the global NPI profile, at the follow-up were presented, particularly for delusion, agitation, irritability, and appetite disturbances (p < 0.05). Twenty-five (19.1%) AD patients and 48 (36.6%) controls suffered RCD during the COVID-19 pandemic. Moreover, AD patients during the COVID-19 pandemic were 0.408 times (95% confidence interval: 0.232-0.716) less likely to suffer RCD than the control. Conclusion: Confinement might ease the cognitive and neuropsychiatric deterioration of AD patients compared to those not in crisis and help prevent RCD in AD patients.

Sundown syndrome in patients with Alzheimer's disease dementia

The sundown syndrome is a complex neurobehavioral disorder in patients with dementia associated with high financial cost and significant caregiver burden. It is a multifactorial phenomenon with unclear pathophysiology, characterized by the presence of neuropsychiatric symptoms in the evening period.

Baseline Predictors of Antipsychotic Treatment Continuation and Response at Week 8 in Patients with Alzheimer's Disease with Psychosis or Aggressive Symptoms: An Analysis of the CATIE-AD Study

BACKGROUND/OBJECTIVE

The aim of the present study was to investigate predictors of atypical antipsychotic (AAP) treatment continuation and response by week 8 in patients with Alzheimer's disease (AD) who have psychotic/aggressive symptoms using the Clinical Antipsychotic Trials of Intervention Effectiveness-Alzheimer's Disease (CATIE-AD) dataset.

METHODS

Clinical data was utilized from 421 AD outpatients with psychotic/aggressive symptoms who needed interventional treatment. Logistic regression analyses were performed to examine which baseline sociodemographic and clinical characteristics contributed to treatment 'continuation' and 'response', the latter of which was evaluated by the Clinical Global Impression of Change (CGI-C), Neuropsychiatric Inventory (NPI), and Brief Psychiatric Scale (BPRS).

RESULTS

The treatment continuation rate was 48.7%, and CGI-C, NPI, and BPRS response rate by the last observation carried forward method were 42.7%, 48.6%, and 37.5%, respectively. No significant predictor was identified for treatment continuation in the Caucasian patients (n = 331), while better treatment response was predicted by a lower Mini-Mental State Examination score, treatment with risperidone (versus olanzapine and quetiapine), history of diabetes mellitus, healthier physical status, and more severe initial psychotic symptoms.

CONCLUSIONS

Comparatively high intolerability from AAPs in the short term was confirmed. We found that baseline clinical predictors to treatment response in Caucasian AD patients with psychotic/aggressive symptoms include treatment with risperidone (versus quetiapine and olanzapine), diabetes mellitus, global physical status, cognitive impairment, and psychotic symptoms. Going forward, these findings may help to determine treatment strategies or care plans.

Reliability and structural validity of the Chinese version of the Neuropsychiatric Inventory, Nursing Home version

BACKGROUND

With the increasing number of dementia patients in China, there is a pressing need for a reliable and valid Chinese instrument that can measure neuropsychiatric symptoms in institutionalized dementia patients. This study examined the reliability and structural validity of the Chinese version of the Neuropsychiatric Inventory, Nursing Home version (NPI-NH), in a sample of institutionalized dementia patients in China.

METHODS

A total of 112 residents with dementia (Clinical Dementia Rating = 1: 10.7%; Clinical Dementia Rating = 2: 39.3%; Clinical Dementia Rating = 3: 50.0%) and 30 informants participated in this cross-sectional study. Reliability was tested using Cronbach's α and intra-class correlation coefficient. Principal component analysis was used to evaluate the factor structure of the inventory.

RESULTS

Of the patients, 92.9% had at least one neuropsychiatric symptom. Apathy (57%) was the most common symptom. The Chinese version of the Neuropsychiatric Inventory, Nursing Home version, showed acceptable internal consistency (Cronbach's α for the total scale, frequency, severity, and disturbance subscales were 0.64, 0.70, 0.73, and 0.80, respectively) and test-retest reliability (intra-class correlation coefficient for the total scale, frequency, severity, and disturbance subscales were 0.93, 0.92, 0.89, and 0.91, respectively). Five factors-psychomotor behaviour, affective symptoms, psychosis, sleep disorders, and eating disorders-were identified for the total scale. The cluster symptoms aggression and irritability, depression and anxiety, and delusions and hallucinations were three of the optimally stable groups of symptoms.

CONCLUSIONS

This study demonstrated that the Chinese version of the Neuropsychiatric Inventory, Nursing Home version, is a valid and reliable instrument for evaluating neuropsychiatric symptoms in institutionalized dementia patients.

Effects of dopaminergic depletion and brain atrophy on neuropsychiatric symptoms in de novo Parkinson's disease

BACKGROUND

Neuropsychiatric symptoms impact the patients' quality of life and caregivers' burdens in Parkinson's disease (PD). We aimed to investigate the effects of striatal dopaminergic depletion and brain atrophy on the neuropsychiatric symptoms of patients with PD.

METHODS

Two hundred and seven patients with de novo drug-naïve PD underwent dopamine transporter (DAT) positron emission tomography and brain MRI scanning. In addition, the patients were assessed with caregiver-administered neuropsychiatric inventory (NPI) questionnaires. To evaluate the effects of DAT uptake, subcortical volume and cortical thinning on the patients' neuropsychiatric symptoms, we performed logistic regression and negative binomial regression analyses on the NPI data after controlling for possible confounders.

RESULTS

Frontal cortical thinning was associated with the presence of nighttime behaviour and irritability, and the thinning correlated with the severity of the nighttime behaviour. Temporal cortical thinning was associated with the presence of aggression/agitation, and it correlated with the severity of the aggression/agitation. Subcortical atrophy in the accumbens was associated with the presence of disinhibition and correlated with the severity of the disinhibition. Putamen atrophy and insular thinning were independently associated with the presence of apathy, but only insular thinning correlated with the severity of the apathy. Of the predictors, only frontal cortical thinning correlated with the total NPI score.

CONCLUSIONS

The results of this study suggested that accumbens atrophy and frontotemporal cortical thinning, especially frontal cortical thinning, independently contributed to neuropsychiatric symptoms in patients with PD, while DAT uptake did not affect the neuropsychiatric symptoms.

Developing the Person-Environment Apathy Rating for persons with dementia

OBJECTIVES

To develop the Person-Environment Apathy Rating (PEAR) scale that measures environmental stimulation and apathy in persons with dementia and to evaluate its psychometrics.

METHOD

The PEAR scale consists of the PEAR-Environment subscale and PEAR-Apathy subscales. The items were developed via literature review, field testing, expert review, and pilot testing. The construct validity and reliability were examined through video observation. The parent study enrolled 185 institutionalized residents with dementia. For this study, 96 videos were selected from 24 participants. The PEAR-Environment subscale was validated using the Ambiance Scale and the Crowding Index. The PEAR-Apathy subscale was validated using the Neuropsychiatric Inventory (NPI)-Apathy, Passivity in Dementia Scale (PDS), and NPI-Depression.

RESULTS

The PEAR-Environment subscale and PEAR-Apathy subscales each consists of six items rated on a 1-4 scale. For validity, the Crowding Index slightly, yet significantly, correlated with the PEAR-Environment subscale total score and three of the individual scores. Ambiance Scale scores, both engaging and soothing, did not correlate with the PEAR-Environment subscale. The PEAR-Apathy highly correlated with the PDS and NPI-Apathy and moderately correlated with the NPI-Depression, suggesting good convergent validity and moderate discriminant validity. For reliability, both environment and apathy subscales demonstrated excellent internal consistency. Although facial expression and eye contact showed moderate inter-rater reliability, all other items showed good to excellent inter-rater and intra-rater reliability.

CONCLUSION

This study has successfully developed the PEAR scale and established its psychometrics based on the compatible scales available. The PEAR scale is the first scale that concurrently assesses apathy and environmental stimulation, and is recommended for use in persons with dementia.

Multidisciplinary, Nurse-Led Psychiatric Consultation in Nursing Homes: A Pilot Study in Clinical Practice

PURPOSE

To determine the effects of multidisciplinary, nurse-led psychiatric consultation on behavioral problems of nursing home residents. Residents often suffer from psychiatric symptoms, while staff psychiatric expertise varies.

DESIGN AND METHODS

A pre-post study was conducted in seven homes using the Neuropsychiatric Inventory Nursing Home version (NPI-NH).

FINDINGS

In 71 consultations during 18 months, 56-75% of residents suffered from agitation/aggression, depression, anxiety, and disinhibition. Post-intervention (n = 54), frequency, and severity of psychiatric symptoms were significantly and clinically meaningfully reduced. Also, staff suffered from less work stress.

PRACTICE IMPLICATIONS

Nurse-led psychiatric consultation is valuable to both nursing home residents and staff.

Neuronal Heterotopias Affect the Activities of Distant Brain Areas and Lead to Behavioral Deficits

Neuronal heterotopia refers to brain malformations resulting from deficits of neuronal migration. Individuals with heterotopias show a high incidence of neurological deficits, such as epilepsy. More recently, it has come to be recognized that focal heterotopias may also show a range of psychiatric problems, including cognitive and behavioral impairments. However, because focal heterotopias are not always located in the brain areas responsible for the symptoms, the causal relationship between the symptoms and heterotopias remains elusive. In this study, we showed that mice with focal heterotopias in the somatosensory cortex generated by in utero electroporation exhibited spatial working memory deficit and low competitive dominance behavior, which have been shown to be closely associated with the activity of the medial prefrontal cortex (mPFC) in rodents. Analysis of the mPFC activity revealed that the immediate-early gene expression was decreased and the local field potentials of the mPFC were altered in the mice with heterotopias compared with the control mice. Moreover, activation of these ectopic and overlying sister neurons using the DREADD (designer receptor exclusively activated by designer drug) system improved the working memory deficits. These findings suggest that cortical regions containing focal heterotopias can affect distant brain regions and give rise to behavioral abnormalities. Significance statement: Recent studies reported that patients with heterotopias have a variety of clinical symptoms, such as cognitive disturbance, psychiatric symptoms, and autistic behavior. However, the causal relationship between the symptoms and heterotopias remains elusive. Here we showed that mice with focal heterotopias in the somatosensory cortex generated by in utero electroporation exhibited behavioral deficits that have been shown to be associated with the mPFC activity in rodents. The existence of heterotopias indeed altered the neural activities of the mPFC, and direct manipulation of the neural activity of the ectopic neurons and their sister neurons in the overlying cortex improved the behavioral deficit. Thus, our results indicate that focal heterotopias could affect the activities of distant brain areas and cause behavioral abnormalities.