Apathy, depression, and motor symptoms have distinct and separable resting activity patterns in idiopathic Parkinson disease

The anatomy of apathy: A neurocognitive framework for amotivated behaviour

Apathy is a debilitating syndrome associated with many neurological disorders, including several common neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, and focal lesion syndromes such as stroke. Here, we review neuroimaging studies to identify anatomical correlates of apathy, across brain disorders. Our analysis reveals that apathy is strongly associated with disruption particularly of dorsal anterior cingulate cortex (dACC), ventral striatum (VS) and connected brain regions. Remarkably, these changes are consistent across clinical disorders and imaging modalities. Review of the neuroimaging findings allows us to develop a neurocognitive framework to consider potential mechanisms underlying apathy. According to this perspective, an interconnected group of brain regions - with dACC and VS at its core - plays a crucial role in normal motivated behaviour. Specifically we argue that motivated behaviour requires a willingness to work, to keep working, and to learn what is worth working for. We propose that deficits in any one or more of these processes can lead to the clinical syndrome of apathy, and outline specific approaches to test this hypothesis. A richer neurobiological understanding of the mechanisms underlying apathy should ultimately facilitate development of effective therapies for this disabling condition.

Functional MRI in Idiopathic Parkinson's Disease

Functional MRI (fMRI) has been widely used to study abnormal patterns of brain connectivity at rest and activation during a variety of tasks in patients with idiopathic Parkinson's disease (PD). fMRI studies in PD have led to a better understanding of many aspects of the disease including both motor and non-motor symptoms. Although its translation into clinical practice is still at an early stage, fMRI measures hold promise for multiple clinical applications in PD, including the early detection, predicting future change in clinical status, and as a marker of alterations in brain physiology related to neurotherapeutic agents and neurorehabilitative strategies.

Apathy in corticobasal degeneration: possible parietal involvement

Corticobasal degeneration is a rare disorder, which usually consists of a combination of complex movement disorders, apraxia and cortical changes. Its definition is still evolving and in 2013 an international consortium tried to develop new criteria, based on a systematic literature review. Over a long period of time, we carefully selected 23 patients who fulfilled the criteria for a diagnosis of corticobasal degeneration; all had the so-called corticobasal syndrome phenotype, in accordance with Armstrong et al. (2013). Through a dedicated study, we set out to study behavioral alterations, specifically apathy, and to compare the results obtained with those deriving from a well-defined Parkinson's disease population. On the basis of our limited but specific results, we argue for a possible role of the parietal neural networks as a determinant of apathy, and provide an overview of emerging data in the imaging and pathology literature.

Apathy and brain alterations in Parkinson's disease: a multimodal imaging study

OBJECTIVE

Apathy is a common nonmotor symptom in Parkinson's disease (PD) affecting 40% of patients. The aim of the study was to investigate brain changes and correlates of frontal, striatal, and limbic pathways related to subclinical symptoms of apathy in PD patients.

METHODS

Thirty-two PD patients divided into low-subclinical symptoms of apathy (LSA) (n = 18) and high-subclinical symptoms of apathy (HSA) (n = 14) and 25 healthy controls (HC) underwent a T1-weighted, diffusion-weighted, and resting-state functional MRI. Apathy was evaluated with the Lille Apathy Rating Scale. Voxel-based morphometry, tract-based spatial statistics, and resting-state functional connectivity (FC) analyses were performed with a region-of-interest approach.

RESULTS

HSA-PD showed increased white matter axial and mean diffusivity compared with HC and increased white matter axial diffusivity compared with LSA-PD. HSA-PD showed decreased fronto-striatal and fronto-limbic FC compared with HC and decreased fronto-striatal FC compared with LSA-PD. LSA-PD showed decreased fronto-limbic but increased fronto-striatal FC (hyperconnectivity) compared with HC. No significant differences in grey matter were found. Fronto-striatal FC and white matter axial and mean diffusivity were associated with symptoms of apathy in HSA-PD. The fronto-striatal hyperconnectivity was associated with lower symptoms of apathy in LSA-PD.

INTERPRETATION

Findings suggest distinct brain alterations in PD groups with subclinical symptoms of apathy. The increased pattern of activation in LSA-PD, accompanied with lower apathetic symptomatology, might be the initial manifestation of compensatory mechanisms for dysfunctional limbic pathway. The same pattern of hyperconnectivity has been found in other pathologies and the implication of these abnormalities as a cross-disease model for initial apathy symptomatology is further discussed.

Microstructural Changes in Patients With Parkinson's Disease Comorbid With REM Sleep Behaviour Disorder and Depressive Symptoms

The diagnosis of Parkinson's disease (PD) is currently anchored on clinical motor symptoms, which appear more than 20 years after initiation of the neurotoxicity. Extra-nigral involvement in the onset of PD with probable nonmotor manifestations before the development of motor signs, lead us to the preclinical (asymptomatic) or prodromal stages of the disease (various nonmotor or subtle motor signs). REM sleep behavior disorder (RBD) and depression are established prodromal clinical markers of PD and predict worse motor and cognitive outcomes. Nevertheless, taken by themselves, these markers are not yet claimed to be practical in identifying high-risk individuals. Combining promising markers may be helpful in a reliable diagnosis of early PD. Therefore, we aimed to detect neural correlates of RBD and depression in 93 treatment-naïve and non-demented early PD by means of diffusion MRI connectometry. Comparing four groups of PD patients with or without comorbid RBD and/or depressive symptoms with each other and with 31 healthy controls, we found that these two non-motor symptoms are associated with lower connectivity in several white matter tracts including the cerebellar peduncles, corpus callosum and long association fibers such as cingulum, fornix, and inferior longitudinal fasciculus. For the first time, we were able to detect the involvement of short association fibers (U-fibers) in PD neurodegenerative process. Longitudinal studies on larger sample groups are needed to further investigate the reported associations.

Disrupted amplitude of low-frequency fluctuations and causal connectivity in Parkinson's disease with apathy

Apathy is a common non-motor symptom in Parkinson's disease (PD). We aimed to explore its associated neural substrates changes via amplitude of low-frequency fluctuations (ALFF) and granger causality analysis (GCA). Resting-state functional magnetic resonance imaging (rs-fMRI) scans were performed in 20 PD patients with apathy (PD-A), 22 PD patients without apathy (PD-NA) and 19 healthy volunteers. GCA, a new method exploring direction from one brain region to another, was based on brain regions showing alterations of neural activity as seeds, which were examined utilizing ALFF approach. The relationships between ALFF or GCA and apathetic symptoms were also assessed. Relative to PD-NA group, PD-A group indicated decreased ALFF in left orbital middle frontal gyrus and bilateral superior frontal gyrus (SFG). Only ALFF values in right SFG were negatively correlated with Apathy Scale (AS) scores. Then GCA with the seed of right SFG showed a positive feedback from right thalamus to ipsilateral SFG, which was positively correlated with AS scores. In conclusion, dysfunction in SFG and a positive feedback from thalamus to ipsilateral SFG contributed to presence of PD-related apathy, providing a new perspective for future studies on apathy in PD.

Resting-state connectivity in neurodegenerative disorders: Is there potential for an imaging biomarker?

Biomarkers in whichever modality are tremendously important in diagnosing of disease, tracking disease progression and clinical trials. This applies in particular for disorders with a long disease course including pre-symptomatic stages, in which only subtle signs of clinical progression can be observed. Magnetic resonance imaging (MRI) biomarkers hold particular promise due to their relative ease of use, cost-effectiveness and non-invasivity. Studies measuring resting-state functional MR connectivity have become increasingly common during recent years and are well established in neuroscience and related fields. Its increasing application does of course also include clinical settings and therein neurodegenerative diseases. In the present review, we critically summarise the state of the literature on resting-state functional connectivity as measured with functional MRI in neurodegenerative disorders. In addition to an overview of the results, we briefly outline the methods applied to the concept of resting-state functional connectivity. While there are many different neurodegenerative disorders cumulatively affecting a substantial number of patients, for most of them studies on resting-state fMRI are lacking. Plentiful amounts of papers are available for Alzheimer's disease (AD) and Parkinson's disease (PD), but only few works being available for the less common neurodegenerative diseases. This allows some conclusions on the potential of resting-state fMRI acting as a biomarker for the aforementioned two diseases, but only tentative statements for the others. For AD, the literature contains a relatively strong consensus regarding an impairment of the connectivity of the default mode network compared to healthy individuals. However, for AD there is no considerable documentation on how that alteration develops longitudinally with the progression of the disease. For PD, the available research points towards alterations of connectivity mainly in limbic and motor related regions and networks, but drawing conclusions for PD has to be done with caution due to a relative heterogeneity of the disease. For rare neurodegenerative diseases, no clear conclusions can be drawn due to the few published results. Nevertheless, summarising available data points towards characteristic connectivity alterations in Huntington's disease, frontotemporal dementia, dementia with Lewy bodies, multiple systems atrophy and the spinocerebellar ataxias. Overall at this point in time, the data on AD are most promising towards the eventual use of resting-state fMRI as an imaging biomarker, although there remain issues such as reproducibility of results and a lack of data demonstrating longitudinal changes. Improved methods providing more precise classifications as well as resting-state network changes that are sensitive to disease progression or therapeutic intervention are highly desirable, before routine clinical use could eventually become a reality.

The pathophysiological mechanisms of motivational deficits in Parkinson's disease

Parkinson's disease (PD) is a progressive degenerative disorder that leads to disabling motor symptoms and a wide variety of neuropsychiatric symptoms. Apathy is the most common psychiatric disorder in the early stages of untreated PD and can be defined as a hypodopaminergic syndrome, which also includes anxiety and depression. Apathy is also considered the core feature of the parkinsonian triad (apathy, anxiety and depression) of behavioural non-motor signs, including a motivational deficit. Moreover, apathy is recognised as a distinct chronic neuropsychiatric behavioural disorder based on specific diagnostic criteria. Given the prevalence of apathy in approximately 40% of the general Parkinson's disease population, this appears to be a contributing factor to dementia in PD; also, apathy symptoms are factors that potentially contribute to morbidity, leading to a major impairment of health-related quality of life, thus stressing the importance of understanding the pathophysiology of this disease. Several studies have clearly established a prominent role for DA-mediated signals in PD apathy. However, synergistic interaction between dopaminergic impairment resulting from the neurodegenerative process and deep brain stimulation of the subthalamic nucleus may cause or exacerbate apathy. Furthermore, serotoninergic mechanism signalling is also likely to be of importance in this pathophysiology.

Frequency specific brain networks in Parkinson's disease and comorbid depression

The topological organization underlying the human brain was extensively investigated using resting-state functional magnetic resonance imaging, focusing on a low frequency of signal oscillation from 0.01 to 0.1 Hz. However, the frequency specificities with regard to the topological properties of the brain networks have not been fully revealed. In this study, a novel complementary ensemble empirical mode decomposition (CEEMD) method was used to separate the fMRI time series into five characteristic oscillations with distinct frequencies. Then, the small world properties of brain networks were analyzed for each of these five oscillations in patients (n = 67) with depressed Parkinson’s disease (DPD, n = 20) , non-depressed Parkinson’s disease (NDPD, n = 47) and healthy controls (HC, n = 46). Compared with HC, the results showed decreased network efficiency in characteristic oscillations from 0.05 to 0.12 Hz and from 0.02 to 0.05 Hz for the DPD and NDPD patients, respectively. Furthermore, compared with HC, the most significant inter-group difference across five brain oscillations was found in the basal ganglia (0.01 to 0.05 Hz) and paralimbic-limbic network (0.02 to 0.22 Hz) for the DPD patients, and in the visual cortex (0.02 to 0.05 Hz) for the NDPD patients. Compared with NDPD, the DPD patients showed reduced efficiency of nodes in the basal ganglia network (0.01 to 0.05 Hz). Our results demonstrated that DPD is characterized by a disrupted topological organization in large-scale brain functional networks. Moreover, the CEEMD analysis suggested a prominent dissociation in the topological organization of brain networks between DPD and NDPD in both space and frequency domains. Our findings indicated that these characteristic oscillatory activities in different functional circuits may contribute to distinct motor and non-motor components of clinical impairments in Parkinson’s disease.

High-Intensity Exercise Acutely Increases Substantia Nigra and Prefrontal Brain Activity in Parkinson's Disease

Background

Pathologic alterations in resting-state brain activity patterns exist among individuals with Parkinson’s disease (PD). Since physical exercise alters resting-state brain activity in non-PD populations and improves PD symptoms, we assessed the acute effect of exercise on resting-state brain activity in exercise-trained individuals with PD.

Material/Methods

Resting-state functional magnetic resonance imaging (fMRI) was collected twice for 17 PD participants at the conclusion of an exercise intervention. The acute effect of exercise was examined for PD participants using the amplitude of low frequency fluctuation (ALFF) before and after a single bout of exercise. Correlations of clinical variables (i.e., PDQ-39 quality of life and MDS-UPDRS) with ALFF values were examined for the exercise-trained PD participants.

Results

An effect of acute exercise was observed as an increased ALFF signal within the right ventromedial prefrontal cortex (PFC), left ventrolateral PFC, and bilaterally within the substantia nigra (SN). Quality of life was positively correlated with ALFF values within the vmPFC and vlPFC.

Conclusions

Given the role of the SN and PFC in motor and non-motor symptoms in PD, the acute increases in brain activity within these regions, if repeated frequently over time (i.e., exercise training), may serve as a potential mechanism underlying exercise-induced PD-specific clinical benefits.

Depression, anxiety, and apathy in Parkinson's disease: insights from neuroimaging studies

Depression, anxiety and apathy are common mood disturbances in Parkinson's disease (PD) but their pathophysiology is unclear. Advanced neuroimaging has been increasingly used to unravel neural substrates linked to these disturbances. A systematic review is provided of neuroimaging findings in depression, anxiety and apathy in PD. A PubMed, MEDLINE and EMBASE search of peer‐reviewed original research articles on these mood disturbances in PD identified 38 studies on depression, eight on anxiety and 14 on apathy in PD. Most of the imaging studies used either position emission tomography or single‐photon emission computed tomography techniques. These studies generally suggest increased neural activity in the prefrontal regions and decreased functional connectivity between the prefrontal−limbic networks in depressed patients. Functional imaging studies revealed an inverse correlation between dopaminergic density in the caudate and putamen with the severity of anxiety in PD. There was no consistent correlation between dopaminergic density of thalamus and anxiety. Studies demonstrated both positive and inverse correlations between apathy and metabolism or activity in the striatum, amygdalar, prefrontal, temporal and parietal regions. The clinical variability of study subjects and differences in image pre‐processing and analytical strategies may contribute to discrepant findings in these studies. Both nigrostriatal and extra‐nigrostriatal pathways (in particular the frontal region and its connecting areas) are affected in mood disorders in PD. Identifying the relative contributions of these neural pathways in PD patients with overlapping motor and mood symptoms could provide new pathophysiological clues for the development of better therapeutic targets for affected patients.

Cognitive and behavioral disorders in Parkinson's disease: an update. II: behavioral disorders

Patients with Parkinson's disease (PD) can experience several behavioral symptoms, such as apathy, agitation, hypersexuality, stereotypic movements, pathological gambling, abuse of antiparkinsonian drugs, and REM sleep behavioral disorders. Psychoses and hallucinations, depression and anxiety disorders, and difficulties in recognizing and experiencing emotions also impair behavior and can cause severe psychosocial problems in patients with PD. Symptoms can be present since early stages of the disease, sometimes even before the appearance of classical motor symptoms, likely in relation to dopamine depletion in basal ganglia and/or to dysfunctions of other neurotrasmitter systems, and others can develop later, in some cases in relation to dopaminergic treatment. In this paper, we review recent literature, with particular attention to the last 5 years, on the main behavioral and emotional disturbances described in PD patients as well as the hypothesized neurofunctional substrate of such impairments. Finally, we provide some suggestions on the most suitable instruments to check and assess PD-associated behavioral defects over time.

Separate neural representations of depression, anxiety and apathy in Parkinson's disease

Depression, anxiety and apathy are distinct neuropsychiatric symptoms that highly overlap in Parkinson’s disease (PD). It remains unknown whether each symptom is uniquely associated with a functional network dysfunction. Here, we examined whether individual differences in each neuropsychiatric symptom predict functional connectivity patterns in PD patients while controlling for all other symptoms and motor function. Resting-state functional connectivity MRI were acquired from 27 PD patients and 29 healthy controls. Widespread reduced functional connectivity was identified in PD patients and explained by either the neuropsychiatric or motor symptoms. Depression in PD predicted increased functional connectivity between the orbitofrontal, hippocampal complex, cingulate, caudate and thalamus. Apathy in PD predicted decreased caudate-thalamus and orbitofrontal-parahippocampal connectivity. Anxiety in PD predicted three distinct types of functional connectivity not described before: (i) increased limbic-orbitofrontal cortex; (ii) decreased limbic-dorsolateral prefrontal cortex and orbitofrontal-dorsolateral prefrontal cortices and (iii) decreased sensorimotor-orbitofrontal cortices. The first two types of functional connectivity suggest less voluntary and more automatic emotion regulation. The last type is argued to be specific to PD and reflect an impaired ability of the orbitofrontal cortex to guide goal-directed motor actions in anxious PD patients.

Imaging the Etiology of Apathy, Anxiety, and Depression in Parkinson's Disease: Implication for Treatment

Apathy, depression, and anxiety are among the most important non-motor signs of Parkinson's disease (PD). This may be encountered at early stages of illness and represent a major source of burden. Understanding their pathophysiology is a major prerequisite for efficient therapeutic strategies. Anatomical and metabolic imaging studies have enabled a breakthrough by demonstrating that widespread abnormalities within the limbic circuits notably the orbitofrontal and anterior cingulate cortices, amygdala, thalamus, and ventral striatum are involved in the pathophysiology of depression, anxiety, and apathy in PD. Functional imaging has further shown that mesolimbic dopaminergic but also serotonergic lesions play a major role in the mechanisms of these three neuropsychiatric manifestations, which has direct therapeutic implications.

Brain Magnetic Resonance Imaging (MRI) as a Potential Biomarker for Parkinson's Disease (PD)

Magnetic resonance imaging (MRI) has the potential to serve as a biomarker for Parkinson's disease (PD). However, the type or types of biomarker it could provide remain to be determined. At this time there is not sufficient sensitivity or specificity for MRI to serve as an early diagnostic biomarker, i.e., it is unproven in its ability to determine if a single individual is normal, has mild PD, or has some other forms of degenerative parkinsonism. However there is accumulating evidence that MRI may be useful in staging and monitoring disease progression (staging biomarker), and also possibly as a means to monitor pathophysiological aspects of disease and associated response to treatments, i.e., theranostic marker. As there are increasing numbers of manuscripts that are dedicated to diffusion- and neuromelanin-based imaging methods, this review will focus on these topics cursorily and will delve into pharmacodynamic imaging as a means to get at theranostic aspects of PD.

Imaging the Nonmotor Symptoms in Parkinson's Disease

Parkinson's disease is acknowledged to be a multisystem syndrome, manifesting as a result of multineuropeptide dysfunction, including dopaminergic, cholinergic, serotonergic, and noradrenergic deficits. This multisystem disorder ultimately leads to the presentation of a range of nonmotor symptoms, now appreciated to be an integral part of the disease-specific spectrum of symptoms, often preceding the diagnosis of motor Parkinson's disease. In this chapter, we review the dopaminergic and nondopaminergic basis of these symptoms by exploring the neuroimaging evidence based on several techniques including positron emission tomography, single-photon emission computed tomography molecular imaging, magnetic resonance imaging, functional magnetic resonance imaging, and diffusion tensor imaging. We discuss the role of these neuroimaging techniques in elucidating the underlying pathophysiology of NMS in Parkinson's disease.

The role of high-field magnetic resonance imaging in parkinsonian disorders: Pushing the boundaries forward

Historically, magnetic resonance imaging (MRI) has contributed little to the study of Parkinson's disease (PD), but modern MRI approaches have unveiled several complementary markers that are useful for research and clinical applications. Iron- and neuromelanin-sensitive MRI detect qualitative changes in the substantia nigra. Quantitative MRI markers can be derived from diffusion weighted and iron-sensitive imaging or volumetry. Functional brain alterations at rest or during task performance have been captured with functional and arterial spin labeling perfusion MRI. These markers are useful for the diagnosis of PD and atypical parkinsonism, to track disease progression from the premotor stages of these diseases and to better understand the neurobiological basis of clinical deficits. A current research goal using MRI is to generate time-dependent models of the evolution of PD biomarkers that can help understand neurodegeneration and provide reliable markers for therapeutic trials. This article reviews recent advances in MRI biomarker research at high-field (3T) and ultra high field-imaging (7T) in PD and atypical parkinsonism. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Rivastigmine as a Symptomatic Treatment for Apathy in Parkinson's Dementia Complex: New Aspects for This Riddle

Over 90% of PDD patients show at least one neuropsychiatric symptom (NPS); in the 60-70% two or more NPS are present. Their incidence is important in terms of prognosis and severity of pathology. However, among all NPS, apathy is often the most disturbing, associated with greater caregiver's burden. Similar to other NPS, apathy may be due to a dysfunction of the nigrostriatal pathway, even though, not all the PD patients become apathetic, indicating that apathy should not entirely be considered a dopamine-dependent syndrome, and in fact it might also be related to acetylcholine defects. Apathy has been treated in many ways, without sure benefits; among these, Rivastigmine may present benefic properties. We present a series of 48 patients, suffering from PDD, treated with Rivastigmine, and followed-up for one year; they have been devotedly studied for apathy, even though all the other NPS disorders have been registered. Rivastigmine did not have a prolonged benefic effect on apathy, in our work, on the contrary of what had been observed in the literature, probably due to the longer follow-up of our patients.

Apathy is related to reduced activation in cognitive control regions during set-shifting

Apathy is a prominent and influential symptom in several neurological and psychiatric disorders, but it also occurs in the healthy population. It has considerable impact on daily life functioning, in clinical as well as healthy samples. Even though cognitive control is thought to be disrupted in people with apathy, the exact neural underpinnings of apathy remain unclear. Because flexible shifting between behaviors (set-shifting) is crucial for goal-directed behavior, disruptions in set-shifting may underlie apathy. In this study, the neural correlates of apathy during set-shifting were studied in 34 healthy participants with varying levels of apathy, measured by the Apathy Evaluation Scale. During functional MRI scanning participants performed a set-shifting task, distinguishing between behavioral switches (a change in response to different stimuli), cognitive switches (a change in response rule), and salience decoupling (detecting a change in relevant stimuli). Regression analysis was used to assess the relationship between apathy and brain activation. Results showed that higher apathy scores were related to reduced activation in the medial superior frontal gyrus and cerebellum (Crus I/II) during cognitive set-shifting, but not behavioral shifting and salience decoupling. No relationship between apathy and accuracy or response time was found. These results support the idea that alterations in the neural basis of cognitive control, especially cognitive set-shifting, may contribute to apathy. Hum Brain Mapp 38:2722-2733, 2017. © 2017 Wiley Periodicals, Inc.

Identifying the presence of Parkinson's disease using low-frequency fluctuations in BOLD signals

Parkinson's disease (PD) is a chronic, progressive, and degenerative neurological disorder that is characterized by the degeneration of dopamine neurons in the substantia nigra and the formation of intracellular Lewy inclusion bodies. Resting-state functional magnetic resonance imaging (RS-fMRI) has demonstrated evidence of changes in metabolic patterns in individuals with PD. The purpose of this study was to determine whether the presence of PD could be "predicted" based on resting fluctuations in the blood oxygenation level dependent signal. We utilized RS-fMRI to measure the amplitude of low-frequency fluctuation (ALFF) and the fractional ALFF (fALFF) in 51 patients with PD and 50 age- and sex-matched healthy controls. Compared with the healthy controls, the individuals with PD exhibited altered ALFFs in the bilateral lingual gyrus and left putamen and an altered fALFF in the right cerebellum posterior lobe. Support vector machines (SVMs), which comprise a supervised pattern recognition method that enables predictions at the individual level, were trained to separate individuals with PD from healthy controls based on the ALFF and fALFF. Using the leave-one-out cross-validation method to analyze our sample, we reliably distinguished the participants with PD from the controls with 92% sensitivity and 87% specificity. Overall, these findings suggest that the SVM-neuroimaging approach may be of particular clinical value because it enables the accurate identification of PD at the individual level. RS-fMRI should be considered for development as a biomarker and an analytical tool for the evaluation of PD.

Spontaneous brain activity in the sensorimotor cortex in amyotrophic lateral sclerosis can be negatively regulated by corticospinal fiber integrity

Previous studies failed to detect reduced value of the amplitude of low frequency fluctuation (ALFF) derived from resting state functional magnetic resonance imaging in the primary motor cortex in amyotrophic lateral sclerosis (ALS) though primary motor cortex was mainly affected with ALS. We aimed to investigate the cause of masking the abnormality in the primary motor cortex in ALS and usefulness of ALFF for differential diagnosis among diseases showing muscle weakness. We enrolled ten patients with ALS and eleven disease controls showing muscle weakness. Voxel-wise analysis revealed that significant reduction of ALFF value was present in the right sensorimotor cortex in ALS. There was a significant negative correlation between ALFF value in the right sensorimotor cortex and fractional anisotropy (FA) value in the posterior limbs of the internal capsule (PLIC). For a diagnostic tool, the area under receiver operating characteristic curve improved if the ALS patients with disease duration >1 year were excluded. The present findings raised the possibility of usefulness of ALFF value in the sensorimotor cortex for differential diagnosis of ALS, and supported the notion that adjustment for FA value in the PLIC could improve accuracy.

Abnormalities of regional brain function in Parkinson's disease: a meta-analysis of resting state functional magnetic resonance imaging studies

There is convincing evidence that abnormalities of regional brain function exist in Parkinson’s disease (PD). However, many resting-state functional magnetic resonance imaging (rs-fMRI) studies using amplitude of low-frequency fluctuations (ALFF) have reported inconsistent results about regional spontaneous neuronal activity in PD. Therefore, we conducted a comprehensive meta-analysis using the Seed-based d Mapping and several complementary analyses. We searched PubMed, Embase, and Web of Science databases for eligible whole-brain rs-fMRI studies that measured ALFF differences between patients with PD and healthy controls published from January 1st, 2000 until June 24, 2016. Eleven studies reporting 14 comparisons, comparing 421 patients and 381 healthy controls, were included. The most consistent and replicable findings in patients with PD compared with healthy controls were identified, including the decreased ALFFs in the bilateral supplementary motor areas, left putamen, left premotor cortex, and left inferior parietal gyrus, and increased ALFFs in the right inferior parietal gyrus. The altered ALFFs in these brain regions are related to motor deficits and compensation in PD, which contribute to understanding its neurobiological underpinnings and could serve as specific regions of interest for further studies.

Neural Correlates for Apathy: Frontal-Prefrontal and Parietal Cortical- Subcortical Circuits

Apathy is an uncertain nosographical entity, which includes reduced motivation, abulia, decreased empathy, and lack of emotional involvement; it is an important and heavy-burden clinical condition which strongly impacts in everyday life events, affects the common daily living abilities, reduced the inner goal directed behavior, and gives the heaviest burden on caregivers. Is a quite common comorbidity of many neurological disease, However, there is no definite consensus on the role of apathy in clinical practice, no definite data on anatomical circuits involved in its development, and no definite instrument to detect it at bedside. As a general observation, the occurrence of apathy is connected to damage of prefrontal cortex (PFC) and basal ganglia; “emotional affective” apathy may be related to the orbitomedial PFC and ventral striatum; “cognitive apathy” may be associated with dysfunction of lateral PFC and dorsal caudate nuclei; deficit of “autoactivation” may be due to bilateral lesions of the internal portion of globus pallidus, bilateral paramedian thalamic lesions, or the dorsomedial portion of PFC. On the other hand, apathy severity has been connected to neurofibrillary tangles density in the anterior cingulate gyrus and to gray matter atrophy in the anterior cingulate (ACC) and in the left medial frontal cortex, confirmed by functional imaging studies. These neural networks are linked to projects, judjing and planning, execution and selection common actions, and through the basolateral amygdala and nucleus accumbens projects to the frontostriatal and to the dorsolateral prefrontal cortex. Therefore, an alteration of these circuitry caused a lack of insight, a reduction of decision-making strategies, and a reduced speedness in action decision, major responsible for apathy. Emergent role concerns also the parietal cortex, with its direct action motivation control. We will discuss the importance of these circuits in different pathologies, degenerative or vascular, acute or chronic.

Resting-state functional MRI of abnormal baseline brain activity in young depressed patients with and without suicidal behavior

BACKGROUND

Suicide among youth is a major public health challenge, attracting increasing attention. However, the neurobiological mechanisms and the pathophysiology underlying suicidal behavior in depressed youths are still unclear. The fMRI enables a better understanding of functional changes in the brains of young suicide attempters with depressive disorder through detecting spontaneous neural activity. The purpose of this study was to identify the relationship between abnormalities involving local brain function and suicidal attempts in depressed youths using resting-state fMRI (RS-fMRI).

METHOD

Thirty-five depressed youths aged between 15 and 29 years with a history of suicidal attempts (SU group), 18 patients without suicidal attempts (NSU group) and 47 gender-, age- and education-matched healthy controls (HC) underwent psychological assessment and R-fMRI. The differences in fractional amplitude of low-frequency fluctuation (ALFF) among the three groups were compared. The clinical factors correlated with z-score ALFF in the regions displaying significant group differences were investigated. The ROC method was used to evaluate these clusters as markers to screen patients with suicidal behavior.

RESULTS

Compared with the NSU and HC groups, the SU group showed increased zALFF in the right superior temporal gyrus (r-STG), left middle temporal gyrus (L-MTG) and left middle occipital gyrus (L-MOG). Additionally, significantly decreased zALFF values in the L-SFG and L-MFG were found in the SU group compared with the NSU group, which were negatively correlated with BIS scores in the SU group. Further ROC analysis revealed that the mean zALFF values in these two regions (sensitivity=83.3% and specificity=71.4%) served as markers to differentiate the two patient subtypes.

CONCLUSION

The SU group had abnormal spontaneous neural activity during the resting state, and decreased activity in L-SFG and L-MFG was associated with increased impulsivity in SU group. Our results suggested that abnormal neural activity in these brain regions may represent a potential neurobiological diathesis or predisposition to suicidal behavior in youth depression.

Magnetic resonance imaging as a potential biomarker for Parkinson's disease

Although a magnetic resonance imaging (MRI) biomarker for Parkinson's disease (PD) remains an unfulfilled objective, there have been numerous developments in MRI methodology and some of these have shown promise for PD. With funding from the National Institutes of Health and the Michael J Fox Foundation there will be further validation of structural, diffusion-based, and iron-focused MRI methods as possible biomarkers for PD. In this review, these methods and other strategies such as neurochemical and metabolic MRI have been covered. One of the challenges in establishing a biomarker is in the selection of individuals as PD is a heterogeneous disease with varying clinical features, different etiologies, and a range of pathologic changes. Additionally, longitudinal studies are needed of individuals with clinically diagnosed PD and cohorts of individuals who are at great risk for developing PD to validate methods. Ultimately an MRI biomarker will be useful in the diagnosis of PD, predicting the course of PD, providing a means to track its course, and provide an approach to select and monitor treatments.

Parkinson's disease-related network topographies characterized with resting state functional MRI

Spatial covariance mapping can be used to identify and measure the activity of disease-related functional brain networks. While this approach has been widely used in the analysis of cerebral blood flow and metabolic PET scans, it is not clear whether it can be reliably applied to resting state functional MRI (rs-fMRI) data. In this study, we present a novel method based on independent component analysis (ICA) to characterize specific network topographies associated with Parkinson's disease (PD). Using rs-fMRI data from PD and healthy subjects, we used ICA with bootstrap resampling to identify a PD-related pattern that reliably discriminated the two groups. This topography, termed rs-MRI PD-related pattern (fPDRP), was similar to previously characterized disease-related patterns identified using metabolic PET imaging. Following pattern identification, we validated the fPDRP by computing its expression in rs-fMRI testing data on a prospective case basis. Indeed, significant increases in fPDRP expression were found in separate sets of PD and control subjects. In addition to providing a similar degree of group separation as PET, fPDRP values correlated with motor disability and declined toward normal with levodopa administration. Finally, we used this approach in conjunction with neuropsychological performance measures to identify a separate PD cognition-related pattern in the patients. This pattern, termed rs-fMRI PD cognition-related pattern (fPDCP), was topographically similar to its PET-derived counterpart. Subject scores for the fPDCP correlated with executive function in both training and testing data. These findings suggest that ICA can be used in conjunction with bootstrap resampling to identify and validate stable disease-related network topographies in rs-fMRI. Hum Brain Mapp 38:617-630, 2017. © 2016 Wiley Periodicals, Inc.

Perceived autonomy support, psychological needs satisfaction, depressive symptoms and apathy in French hospitalized older people

Based on the self-determination theory, the aim of the present study was (1) to provide a better understanding of older people's psychological needs satisfaction in geriatric care units, then to link this information with depressive symptoms and apathy; (2) to examine whether the perceived autonomy support from health care professionals differs between needs satisfaction profiles; and (3) to investigate for all participants how each need satisfaction was related to depressive symptoms and apathy. Participants (N=100; Mage=83.33years, SD=7.78, 61% female) completed the measures of psychological needs satisfaction, perceived autonomy support, geriatric depression and apathy. Sociodemographic data were also collected. Cluster analyses showed three distinct profiles: one profile with low-moderate need satisfaction, one profile with high-moderate need satisfaction and one profile with high need satisfaction. These profiles are distinct, and did not differ in terms of participants' characteristics, except gender. Multivariate analysis of covariance (MANCOVA) revealed that participants with low-moderate need satisfaction profile have significantly higher level of depressive symptoms and apathy, and lower levels of perceived autonomy support than participants of the two other profiles. Moreover, for all participants, regression analyses revealed that both competence and relatedness needs satisfaction significantly and negatively explained 28% of the variance in depressive symptoms score and 44% of the variance in apathy score. Our results highlight the interest to examine more thoroughly the variables fostering autonomy-supportive environment in geriatric care units, and to deepen the relationship between competence and relatedness needs satisfaction and depressive symptoms and apathy.

Psychiatric Conditions in Parkinson Disease: A Comparison With Classical Psychiatric Disorders

Psychiatric conditions often complicate the outcome of patients affected by Parkinson disease (PD), but they differ from classical psychiatric disorders in terms of underlying biological mechanisms, clinical presentation, and treatment response. The purpose of the present review is to illustrate the biological and clinical aspects of psychiatric conditions associated with PD, with particular reference to the differences with respect to classical psychiatric disorders. A careful search of articles on main databases was performed in order to obtain a comprehensive review about the main psychiatric conditions associated with PD. A manual selection of the articles was then performed in order to consider only those articles that concerned with the topic of the review. Psychiatric conditions in patients with PD present substantial differences with respect to classical psychiatric disorders. Their clinical presentation does not align with the symptom profiles represented by Diagnostic and Statistical Manual for Mental Disorders and International Classification of Diseases. Furthermore, psychiatry treatment guidelines are of poor help in managing psychiatric symptoms of patients with PD. Specific diagnostic tools and treatment guidelines are needed to allow early diagnosis and adequate treatment of psychiatric conditions in comorbidity with PD.

[Neuroimaging of functional abnormalities in apathy]

Apathy is a common comorbid condition in neurologic and somatic disorders (Alzheimer's disease, Parkinson's disease, multiple sclerosis, frontotemporal dementia, senile dementia, HIV) and a symptom of many psychiatric disorders. Neurophysiologic research in this area aims to examine the specific features to differentiate the apathy from main disorder. This paper reviews neuroimaging studies of functional abnormalities in apathy.

Baseline predictors of worsening apathy in Parkinson's disease: A prospective longitudinal study

INTRODUCTION

Apathy is one of the most common behavioural disorders in Parkinson's disease (PD) and contributes significantly to a reduced quality of life in PD patients.

METHODS

We conducted a prospective longitudinal study of 89 mild PD patients over 18 months, measuring apathy symptoms at 6-monthly intervals using the Starkstein Apathy Scale, as well as measures of motor and non-motor symptoms, cognitive function, and functional disability at baseline. Mixed-effects models were used to characterise the individual trajectories of apathy symptom severity, and linear regression with stepwise elimination procedure was used to select significant baseline predictors.

RESULTS

Clinically significant levels of apathy were present in 42.7% of our sample at baseline, with symptom severity remaining relatively stable on average over the course of 18 months. Male gender, lower educational attainment, higher depression symptom severity, more severe functional disability, and the presence of dyskinesias at study entry predicted increasing apathy over the subsequent 18 months.

CONCLUSIONS

Patients with these factors are at risk for progression of apathy, which may be prevented by treating depression and functional disability. Further studies are needed to address both the specific neurobiological pathways and psychosocial factors underpinning apathy in PD.

Depression and anxiety are co-morbid but dissociable in mild Parkinson's disease: A prospective longitudinal study of patterns and predictors

BACKGROUND

Depression and anxiety are common in Parkinson's disease (PD) and contribute significantly to a reduced quality of life in PD patients. Though they often co-exist, it is unclear whether depression and anxiety result from a shared pathological process. We studied the longitudinal course and determinants of depression and anxiety in PD in order to understand which factors contribute to the development of these symptoms.

METHODS

We conducted a prospective longitudinal study of 89 mild PD patients over 18 months, measuring depressive and anxiety symptoms at 6 monthly intervals using the Geriatric Depression Scale and Hospital Anxiety and Depression Scale--'Anxiety' subscale. Univariate and multivariate Generalised Estimating Equations were used to investigate the course of depression and anxiety and their association with demographic factors, motor measures, non-motor symptoms, and pharmacological factors.

RESULTS

Depression and anxiety were co-morbid in 13.5% of the sample. Depressive symptoms remained relatively stable while anxiety symptoms improved over the course of 18 months. Severity of depressive symptoms was associated with female gender, motor fluctuations, apathy, and anxiety, while severity of anxiety was associated with older age, higher educational attainment, shorter disease duration, younger age of disease onset, and excessive daytime sleepiness.

CONCLUSIONS

Although depression and anxiety are frequently co-morbid in PD, they were dissociable from each other. They had distinct trajectories and different longitudinal relationships with demographic, motor, and non-motor factors that were unique to each disorder.

Neuroimaging of Parkinson's disease: Expanding views

Advances in molecular and structural and functional neuroimaging are rapidly expanding the complexity of neurobiological understanding of Parkinson's disease (PD). This review article begins with an introduction to PD neurobiology as a foundation for interpreting neuroimaging findings that may further lead to more integrated and comprehensive understanding of PD. Diverse areas of PD neuroimaging are then reviewed and summarized, including positron emission tomography, single photon emission computed tomography, magnetic resonance spectroscopy and imaging, transcranial sonography, magnetoencephalography, and multimodal imaging, with focus on human studies published over the last five years. These included studies on differential diagnosis, co-morbidity, genetic and prodromal PD, and treatments from L-DOPA to brain stimulation approaches, transplantation and gene therapies. Overall, neuroimaging has shown that PD is a neurodegenerative disorder involving many neurotransmitters, brain regions, structural and functional connections, and neurocognitive systems. A broad neurobiological understanding of PD will be essential for translational efforts to develop better treatments and preventive strategies. Many questions remain and we conclude with some suggestions for future directions of neuroimaging of PD.

Association of specific frequency bands of functional MRI signal oscillations with motor symptoms and depression in Parkinson's disease

A novel empirical mode decomposition method was adopted to investigate the dissociative or interactive neural impact of depression and motor impairments in Parkinson’s disease (PD). Resting-state fMRI data of 59 PD subjects were first decomposed into characteristic frequency bands, and the main effects of motor severity and depression and their interaction on the energy of blood-oxygen-level-dependent signal oscillation in specific frequency bands were then evaluated. The results show that the severity of motor symptoms is negatively correlated with the energy in the frequency band of 0.10–0.25 Hz in the bilateral thalamus, but positively correlated with 0.01–0.027 Hz band energy in the bilateral postcentral gyrus. The severity of depression, on the other hand, is positively correlated with the energy of 0.10–0.25 Hz but negatively with 0.01–0.027 Hz in the bilateral subgenual gyrus. Notably, the interaction between motor and depressive symptoms is negatively correlated with the energy of 0.10–0.25 Hz in the substantia nigra, hippocampus, inferior orbitofrontal cortex, and temporoparietal junction, but positively correlated with 0.02–0.05 Hz in the same regions. These findings indicate unique associations of fMRI band signals with motor and depressive symptoms in PD in specific brain regions, which may underscore the neural impact of the comorbidity and the differentiation between the two PD-related disorders.

Parkinson's disease-related spatial covariance pattern identified with resting-state functional MRI

In this study, we sought to identify a disease-related spatial covariance pattern of spontaneous neural activity in Parkinson's disease using resting-state functional magnetic resonance imaging (MRI). Time-series data were acquired in 58 patients with early to moderate stage Parkinson's disease and 54 healthy controls, and analyzed by Scaled Subprofile Model Principal Component Analysis toolbox. A split-sample analysis was also performed in a derivation sample of 28 patients and 28 control subjects and validated in a prospective testing sample of 30 patients and 26 control subjects. The topographic pattern of neural activity in Parkinson's disease was characterized by decreased activity in the striatum, supplementary motor area, middle frontal gyrus, and occipital cortex, and increased activity in the thalamus, cerebellum, precuneus, superior parietal lobule, and temporal cortex. Pattern expression was elevated in the patients compared with the controls, with a high accuracy (90%) to discriminate the patients from the controls. The split-sample analysis produced a similar pattern but with a lower accuracy for group discrimination in both the derivation (80%) and the validation (73%) samples. Our results showed that resting-state functional MRI can be potentially useful for identification of Parkinson's disease-related spatial covariance patterns, and for differentiation of Parkinson's disease patients from healthy controls at an individual level.

Acute Modulation of Brain Connectivity in Parkinson Disease after Automatic Mechanical Peripheral Stimulation: A Pilot Study

OBJECTIVE

The present study shows the results of a double-blind sham-controlled pilot trial to test whether measurable stimulus-specific functional connectivity changes exist after Automatic Mechanical Peripheral Stimulation (AMPS) in patients with idiopathic Parkinson Disease.

METHODS

Eleven patients (6 women and 5 men) with idiopathic Parkinson Disease underwent brain fMRI immediately before and after sham or effective AMPS. Resting state Functional Connectivity (RSFC) was assessed using the seed-ROI based analysis. Seed ROIs were positioned on basal ganglia, on primary sensory-motor cortices, on the supplementary motor areas and on the cerebellum. Individual differences for pre- and post-effective AMPS and pre- and post-sham condition were obtained and first entered in respective one-sample t-test analyses, to evaluate the mean effect of condition.

RESULTS

Effective AMPS, but not sham stimulation, induced increase of RSFC of the sensory motor cortex, nucleus striatum and cerebellum. Secondly, individual differences for both conditions were entered into paired group t-test analysis to rule out sub-threshold effects of sham stimulation, which showed stronger connectivity of the striatum nucleus with the right lateral occipital cortex and the cuneal cortex (max Z score 3.12) and with the right anterior temporal lobe (max Z score 3.42) and of the cerebellum with the right lateral occipital cortex and the right cerebellar cortex (max Z score 3.79).

CONCLUSIONS

Our results suggest that effective AMPS acutely increases RSFC of brain regions involved in visuo-spatial and sensory-motor integration.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that automatic mechanical peripheral stimulation is effective in modulating brain functional connectivity of patients with Parkinson Disease at rest.

TRIAL REGISTRATION

Clinical Trials.gov NCT01815281.

Dissociative contributions of the anterior cingulate cortex to apathy and depression: Topological evidence from resting-state functional MRI

Apathy is defined as a mental state characterized by a lack of goal-directed behavior. However, the underlying mechanisms of apathy remain to be fully understood. Apathy shares certain symptoms with depression and both these affective disorders are known to be associated with dysfunctions of the frontal cortex-basal ganglia circuits. It is expected that clarifying differences in neural mechanisms between the two conditions would lead to an improved understanding of apathy. The present study was designed to investigate whether apathy and depression depend on different network properties of the frontal cortex-basal ganglia circuits, by using resting state fMRI. Resting-state fMRI measurement and neuropsychological testing were conducted on middle-aged and older adults (N=392). Based on graph theory, we estimated nodal efficiency (functional integration), local efficiency (functional segregation), and betweenness centrality. We conducted multiple regression analyses for the network parameters using age, sex, apathy, and depression as predictors. Interestingly, results indicated that the anterior cingulate cortex showed lower nodal efficiency, local efficiency, and betweenness centrality in apathy, whereas in depression, it showed higher nodal efficiency and betweenness centrality. The anterior cingulate cortex constitutes the so-called "salience network", which detects salient experiences. Our results indicate that apathy is characterized by decreased salience-related processing in the anterior cingulate cortex, whereas depression is characterized by increased salience-related processing.

Altered Resting-State Brain Activity and Connectivity in Depressed Parkinson's Disease

Depressive symptoms are common in Parkinson's disease (PD), but the neurophysiological mechanisms of depression in PD are poorly understood. The current study attempted to examine disrupted spontaneous local brain activities and functional connectivities that underlie the depression in PD. We recruited a total of 20 depressed PD patients (DPD), 40 non-depressed PD patients (NDPD) and 43 matched healthy controls (HC). All the subjects underwent neuropsychological tests and resting-state fMRI scanning. The between-group differences in the amplitude of low frequency fluctuations (ALFF) of BOLD signals were examined using post-hoc tests after the analysis of covariance. Compared with the NDPD and HC, the DPD group showed significantly increased ALFF in the left median cingulated cortex (MCC). The functional connectivity (FC) between left MCC and all the other voxels in the brain were then calculated. Compared with the HC and NDPD group, the DPD patients showed stronger FC between the left MCC and some of the major nodes of the default mode network (DMN), including the post cingulated cortex/precuneus, medial prefrontal cortex, inferior frontal gyrus, and cerebellum. Correlation analysis revealed that both the ALFF values in the left MCC and the FC between the left MCC and the nodes of DMN were significantly correlated with the Hamilton Depression Rating Scale score. Moreover, higher local activities in the left MCC were associated with increased functional connections between the MCC and the nodes of DMN in PD. These abnormal activities and connectivities of the limbic-cortical circuit may indicate impaired high-order cortical control or uncontrol of negative mood in DPD, which suggested a possible neural mechanism of the depression in PD.

Neuroimaging Analysis of the Dopamine Basis for Apathetic Behaviors in an MPTP-Lesioned Primate Model

Apathy commonly occurs in Parkinson disease (PD) patients; however, the role of dopamine in the pathophysiology of apathy remains elusive. We previously demonstrated that dopaminergic dysfunction within the ventral tegmental area (VTA)-nucleus accumbens (NAcc) pathway contributes to the manifestation of apathetic behaviors in monkeys treated with the selective dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We now extend these studies to identify dopaminergic dysfunction in cortical regions that correlate with development of apathetic behaviors. Specifically, we measured the effects of MPTP on monkeys' willingness to attempt goal directed behaviors, which is distinct from their ability to perform tasks. A total of 16 monkeys had baseline magnetic resonance imaging (MRI) and positron emission tomography (PET), using 6-[¹⁸F]fluorodopa (FD), [¹¹C]dihydrotetrabenazine (DTBZ), and 2β-[¹¹C]carbomethoxy-3β-(4-fluorophenyl)tropane (CFT). The monkeys received unilateral infusion of different doses of MPTP (0 – 0.31mg/kg) to produce a wide range of severity of motor parkinsonism. Eight weeks after MPTP, PET scans were repeated and animals were euthanized. Apathetic behavior and motor impairments were assessed blindly both pre- and post-MPTP infusion. Apathy scores were compared to in vitro and in vivo dopaminergic measures. Apathy scores increased following MPTP and correlated with PET measures of dopaminergic terminals (DTBZ or CFT) in dorsal lateral prefrontal cortex (DLPFC), ventromedial prefrontal cortex (VMPFC), and insular cortex (IC). Among all the cortical regions assessed, forward step-wise regression analyses indicated that only stereologic cell counts in VTA, and not counts in the substantia nigra (SN), predict dopamine transporter changes in IC. Our findings suggest that dopaminergic dysfunction within the VTA–IC pathway plays a role in the manifestation of apathetic behaviors in MPTP-lesioned primates.

Emotional dysfunctions in neurodegenerative diseases

Neurodegenerative diseases are characterized primarily by motor signs but are also accompanied by emotional disturbances. Because of the limited knowledge about these dysfunctions, this Review provides an overview of emotional competencies in Huntington's disease (HD), Parkinson's disease (PD), and multiple sclerosis (MS), with a focus on emotion recognition, emotion regulation, and depression. Most studies indicate facial emotion recognition deficits in HD and PD, whereas data for MS are inconsistent. On a neural level, dysfunctions of amygdala and striatum, among others, have been linked to these impairments. These dysfunctions also tap brain regions that are part of the emotion regulation network, suggesting problems in this competency, too. Research points to dysfunctional emotion regulation in MS, whereas findings for PD and HD are missing. The high prevalence of depression in all three disorders emphasizes the need for effective therapies. Research on emotional disturbances might improve treatment, thereby increasing patients' and caregivers' well-being.