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

Plane-wave theory of nondegenerate oscillation in the linear photorefractive passive phase-conjugate mirror

We present a plane-wave theory of nondegenerate oscillation in the linear passive (self-pumped) phase-conjugate mirror (PPCM). The circumstances under which the plane-wave theory permits spontaneous nondegenerate oscillation in this and other PPCM's are discussed

Alexithymia and apathy in Parkinson's disease: neurocognitive correlates

Non-motor symptoms such as neuropsychiatric and cognitive dysfunction have been found to be common in Parkinson’s disease (PD) but the relation between such symptoms is poorly understood. We focused on alexithymia, an impairment of affective and cognitive emotional processing, as there is evidence for its interaction with cognition in other disorders. Twenty-two non-demented PD patients and 22 matched normal control adults (NC) were administered rating scales assessing neuropsychiatric status, including alexithymia, apathy, and depression, and a series of neuropsychological tests. As expected, PD patients showed more alexithymia than NC, and there was a significant association between alexithymia and disease stage. Alexithymia was associated with performance on non-verbally mediated measures of executive and visuospatial function, but not on verbally mediated tasks. By contrast, there was no correlation between cognition and ratings of either depression or apathy. Our findings demonstrate a distinct association of alexithymia with non-verbal cognition in PD, implicating right hemisphere processes, and differentiate between alexithymia and other neuropsychiatric symptoms in regard to PD cognition.Published versio

Self-induced frequency scanning and distributed Bragg reflection in semiconductor lasers with phase-conjugate feedback

A GaAlAs semiconductor laser with feedback from a barium titanate photorefractive ring passive phase-conjugate mirror can be made to perform repeating or nonrepeating frequency scans over a 10-nm range toward either the blue or the red. The direction of scanning and whether the scans repeat may be controlled by adjusting the overlap of the interaction beams in the crystal. This overlap region may be adjusted so that the diode frequency spectrum, originally occupying about 10 longitudinal modes, scans and narrows as the conjugate signal builds up, coming to rest often in one, but sometimes two or three, longitudinal modes as a result of self-generated distributed-feedback effects. We also report similar effects caused by feedback from the total-internal-reflection passive phase-conjugate mirror. The alignment-control mechanism of the ring mirror is, however, not available in this case

Semi-self-pumped phase-conjugate mirrors

We describe semi-self-pumped photorefractive phase-conjugate mirrors based on the unidirectional ring resonator and the double phase-conjugate mirror. Their applicability to thresholding phase conjugation and one-way imaging through distortions is discussed

Vibration resistance, short coherence length operation, and mode-locked pumping in passive phase conjugate mirrors

Because the ring and semilinear passive phase conjugate mirrors use dynamic transmission holograms, they are insensitive to vibration and may be pumped with light of short coherence length or with picosecond mode‐locked laser light. Experimental demonstrations of these modes of operation are described

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

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