Great nature’s second course: Introduction to the special issue on the behavioral neuroscience of sleep

Sleep is necessary for normal psychological functioning, and psychological function in turn affects sleep integrity. Recent investigations delineate the relation of sleep to a broad array of processes ranging from learning and memory to emotional reactivity and mood, and use a variety of methodological approaches (imaging, electrophysiological, behavioral) to reveal the complex relations between sleep and the functioning of the awake brain. The articles in this issue advance our fundamental knowledge of the relation of sleep to psychological function. In addition, several of the articles discuss how sleep is affected by or affects human clinical conditions, including insomnia, epilepsy, mild cognitive impairment, bipolar disorder, and cancer. Together, the articles of this special issue highlight recent progress in understanding the behavioral neuroscience of sleep and identify promising areas for future research, including the possibility of sleep-based interventions to improve psychological health.Accepted manuscrip

Emergence of nonmotor symptoms as the focus of research and treatment of Parkinson's disease: Introduction to the special section on nonmotor dysfunctions in Parkinson's disease

Parkinson's disease (PD) is traditionally characterized by the cardinal motor symptoms of tremor, rigidity, slowness of movement, and impairments of posture, gait, and balance. A relatively new focus of research and treatment is the nonmotor symptoms of the disease, following from recent understanding of the neuropathological stages. Disruptions of arousal, mood, sleep, and autonomic function before the first motor signs of PD implicate the lower brainstem, which is affected before the substantia nigra and dopaminergic system. In later stages of the disease, the pathology extends to the cortex, accompanied by impairments in cognition and perception. The articles in this special section advance our knowledge of the brain bases of the nonmotor symptoms of PD, including disrupted visual perception, impaired cognition across a range of domains, and psychiatric and artistic manifestations. Subtypes under investigation include those described by side of disease onset (left or right body side), predominant cognitive profile, and gender. Taken together, the articles in this special section reflect the field's growing focus on the nonmotor symptoms of PD, their brain bases, and the corresponding potential for their treatment.Published versio

Neurocognitive Correlates of Apathy and Anxiety in Parkinson's Disease

Parkinson's disease (PD) is associated with various nonmotor symptoms including neuropsychiatric and cognitive dysfunction. We examined the relation between apathy, anxiety, side of onset of motor symptoms, and cognition in PD. We hypothesized that PD patients would show different neuropsychiatric and neurocognitive profiles depending on the side of onset. 22 nondemented PD patients (11 right-side onset (RPD) with predominant left-hemisphere pathology, and 11 LPD) and 22 matched healthy controls (NC) were administered rating scales assessing apathy and anxiety, and a series of neuropsychological tests. PD patients showed a higher anxiety level than NC. There was a significant association between apathy, anxiety, and disease duration. In LPD, apathy but not anxiety was associated with performance on nonverbally mediated executive function and visuospatial measures, whereas, in RPD, anxiety but not apathy correlated with performance on verbally mediated tasks. Our findings demonstrated a differential association of apathy and anxiety to cognition in PD

Visual scanning patterns and executive function in relation to facial emotion recognition in aging

OBJECTIVE: The ability to perceive facial emotion varies with age. Relative to younger adults (YA), older adults (OA) are less accurate at identifying fear, anger, and sadness, and more accurate at identifying disgust. Because different emotions are conveyed by different parts of the face, changes in visual scanning patterns may account for age-related variability. We investigated the relation between scanning patterns and recognition of facial emotions. Additionally, as frontal-lobe changes with age may affect scanning patterns and emotion recognition, we examined correlations between scanning parameters and performance on executive function tests. METHODS: We recorded eye movements from 16 OA (mean age 68.9) and 16 YA (mean age 19.2) while they categorized facial expressions and non-face control images (landscapes), and administered standard tests of executive function. RESULTS: OA were less accurate than YA at identifying fear (p < .05, r = .44) and more accurate at identifying disgust (p < .05, r = .39). OA fixated less than YA on the top half of the face for disgust, fearful, happy, neutral, and sad faces (p values < .05, r values ≥ .38), whereas there was no group difference for landscapes. For OA, executive function was correlated with recognition of sad expressions and with scanning patterns for fearful, sad, and surprised expressions. CONCLUSION: We report significant age-related differences in visual scanning that are specific to faces. The observed relation between scanning patterns and executive function supports the hypothesis that frontal-lobe changes with age may underlie some changes in emotion recognition.Accepted manuscrip

Impaired perception of biological motion in Parkinson’s disease

OBJECTIVE: We examined biological motion perception in Parkinson’s disease (PD). Biological motion perception is related to one’s own motor function and depends on the integrity of brain areas affected in PD, including posterior superior temporal sulcus. If deficits in biological motion perception exist, they may be specific to perceiving natural/fast walking patterns that individuals with PD can no longer perform, and may correlate with disease-related motor dysfunction. METHOD: Twenty-six nondemented individuals with PD and 24 control participants viewed videos of point-light walkers and scrambled versions that served as foils, and indicated whether each video depicted a human walking. Point-light walkers varied by gait type (natural, parkinsonian) and speed (0.5, 1.0, 1.5 m/s). Participants also completed control tasks (object motion, coherent motion perception), a contrast sensitivity assessment, and a walking assessment. RESULTS: The PD group demonstrated significantly less sensitivity to biological motion than the control group (p < .001, Cohen’s d = 1.22), regardless of stimulus gait type or speed, with a less substantial deficit in object motion perception (p = .02, Cohen’s d = .68). There was no group difference in coherent motion perception. Although individuals with PD had slower walking speed and shorter stride length than control participants, gait parameters did not correlate with biological motion perception. Contrast sensitivity and coherent motion perception also did not correlate with biological motion perception. CONCLUSION: PD leads to a deficit in perceiving biological motion, which is independent of gait dysfunction and low-level vision changes, and may therefore arise from difficulty perceptually integrating form and motion cues in posterior superior temporal sulcus.Published versio

The relation of anxiety and cognition in Parkinson's disease

OBJECTIVE: Parkinson’s disease (PD) has long been conceptualized as a motor disorder, but nonmotor symptoms also manifest in the disease and significantly reduce quality of life. Anxiety and cognitive dysfunction are prevalent nonmotor symptoms, even in early disease stages, but the relation between these symptoms remains poorly understood. We examined self-reported anxiety and neurocognitive function, indexed by measures of executive function (set-shifting and phonemic fluency), categorical fluency, and attention/working memory. We hypothesized that anxiety would correlate with cognitive performance. METHOD: The Beck Anxiety Inventory and cognitive tests (Trail Making, Verbal Fluency, Digit Span) were administered to 77 nondemented adults with mild to moderate idiopathic PD (39 men, 38 women; Mage = 62.9 years). RESULTS: Higher anxiety was associated with more advanced disease stage and severity and with poorer set-shifting when using a derived metric to account for motoric slowing. Depression correlated with greater anxiety and disease severity, but not with cognitive performance. CONCLUSIONS: Our findings support the association of anxiety with a specific domain of executive function, set-shifting, in nondemented individuals with mild to moderate PD, raising the possibility that treatment of anxiety may alleviate aspects of executive dysfunction in this population.Accepted manuscrip

The impact of sleep quality on cognitive functioning in Parkinson's disease

In healthy individuals and those with insomnia, poor sleep quality is associated with decrements in performance on tests of cognition, especially executive function. Sleep disturbances and cognitive deficits are both prevalent in Parkinson's disease (PD). Sleep problems occur in over 75% of patients, with sleep fragmentation and decreased sleep efficiency being the most common sleep complaints, but their relation to cognition is unknown. We examined the association between sleep quality and cognition in PD. In 35 non-demented individuals with PD and 18 normal control adults (NC), sleep was measured using 24-hr wrist actigraphy over 7 days. Cognitive domains tested included attention and executive function, memory and psychomotor function. In both groups, poor sleep was associated with worse performance on tests of attention/executive function but not memory or psychomotor function. In the PD group, attention/executive function was predicted by sleep efficiency, whereas memory and psychomotor function were not predicted by sleep quality. Psychomotor and memory function were predicted by motor symptom severity. This study is the first to demonstrate that sleep quality in PD is significantly correlated with cognition and that it differentially impacts attention and executive function, thereby furthering our understanding of the link between sleep and cognition.Published versio

The impact of sleep quality on cognitive functioning in Parkinson's disease

In healthy individuals and those with insomnia, poor sleep quality is associated with decrements in performance on tests of cognition, especially executive function. Sleep disturbances and cognitive deficits are both prevalent in Parkinson's disease (PD). Sleep problems occur in over 75% of patients, with sleep fragmentation and decreased sleep efficiency being the most common sleep complaints, but their relation to cognition is unknown. We examined the association between sleep quality and cognition in PD. In 35 non-demented individuals with PD and 18 normal control adults (NC), sleep was measured using 24-hr wrist actigraphy over 7 days. Cognitive domains tested included attention and executive function, memory and psychomotor function. In both groups, poor sleep was associated with worse performance on tests of attention/executive function but not memory or psychomotor function. In the PD group, attention/executive function was predicted by sleep efficiency, whereas memory and psychomotor function were not predicted by sleep quality. Psychomotor and memory function were predicted by motor symptom severity. This study is the first to demonstrate that sleep quality in PD is significantly correlated with cognition and that it differentially impacts attention and executive function, thereby furthering our understanding of the link between sleep and cognition.Published versio

Normal discrimination of spatial frequency and contrast across visual hemifields in left-onset Parkinson’s disease: evidence against perceptual hemifield biases

Individuals with Parkinson's disease (PD) with symptom onset on the left side of the body (LPD) show a mild type of left-sided visuospatial neglect, whereas those with right-onset (RPD) generally do not. The functional mechanisms underlying these observations are unknown. Two hypotheses are that the representation of left-space in LPD is either compressed or reduced in salience. We tested these hypotheses psychophysically. Participants were 31 non-demented adults with PD (15 LPD, 16 RPD) and 17 normal control adults (NC). The spatial compression hypothesis was tested by showing two sinusoidal gratings, side by side. One grating's spatial frequency (SF) was varied across trials, following a staircase procedure, whereas the comparison grating was held at a constant SF. While fixating on a central target, participants estimated the point at which they perceived the two gratings to be equal in SF. The reduced salience hypothesis was tested in a similar way, but by manipulating the contrast of the test grating rather than its SF. There were no significant differences between groups in the degree of bias across hemifields for SF discrimination or for contrast discrimination. Results did not support either the spatial compression hypothesis or the reduced salience hypothesis. Instead, they suggest that at this perceptual level, LPD do not have a systematically biased way of representing space in the left hemifield that differs from healthy individuals, nor do they perceive stimuli on the left as less salient than stimuli on the right. Neglect-like syndrome in LPD instead presumably arises from dysfunction of higher-order attention.Published versio

Spatial judgment in Parkinson's disease: Contributions of attentional and executive dysfunction

Spatial judgment is impaired in Parkinson's disease (PD), with previous research suggesting that disruptions in attention and executive function are likely contributors. If judgment of center places demands on frontal systems, performance on tests of attention/executive function may correlate with extent of bias in PD, and attentional disturbance may predict inconsistency in spatial judgment. The relation of spatial judgment to attention/executive function may differ for those with left-side versus right-side motor onset (LPD, RPD), reflecting effects of attentional lateralization. We assessed 42 RPD, 37 LPD, and 67 healthy control participants with a Landmark task (LM) in which a cursor moved horizontally from the right (right-LM) or left (left-LM). The task was to judge the center of the line. Participants also performed neuropsychological tests of attention and executive function. LM group differences were found on left-LM only, with both PD subgroups biased leftward of the control group (RPD p < .05; LPD p < .01; no RPD-LPD difference). For left-LM trials, extent of bias significantly correlated with performance on the cognitive tasks for PD but not for the control group. PD showed greater variability in perceived center than the control group; this variability correlated with performance on the cognitive tasks. The correlations between performance on the test of spatial judgment and the tests of attention/executive function suggest that frontal-based attentional dysfunction affects dynamic spatial judgment, both in extent of spatial bias and in consistency of response as indexed by intertrial variability. (PsycINFO Database Record (c) 2019 APA, all rights reserved).R01 NS067128 - NINDS NIH HHS; R21 NS043730 - NINDS NIH HHS; National Institute of Neurological Disorders and Stroke; American Parkinson's Disease Association; Massachusetts ChapterAccepted manuscrip