Publications by authors named "Leopold D"

The macaque cerebral cortex contains concentrations of neurons that prefer faces over inanimate objects. Although these so-called face patches are thought to be specialized for the analysis of facial signals, their exact tuning properties remain unclear. For example, what happens when an object by chance resembles a face? Everyday objects can sometimes, through the accidental positioning of their internal components, appear as faces.

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  • The conservation community is focusing on recovering species at risk of extinction, particularly in Maui, by implementing climate-resilient recovery plans for 36 native plant species.
  • A tailored spatial conservation prioritization (SCP) approach was developed, emphasizing transparency, flexibility, and expert engagement, consisting of generating multiple prioritization solutions and selecting the best based on expert-agreed criteria.
  • This method reduced the necessary conservation area by 36% while still ensuring high-quality habitats for species, proving more effective than existing tools like prioritizr by enhancing local recovery planning efforts.
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The brain helps us survive by forming internal representations of the external world. Excitatory cortical neurons are often precisely tuned to specific external stimuli. However, inhibitory neurons, such as parvalbumin-positive (PV) interneurons, are generally less selective.

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Importance: In 2022, the US House of Representatives passed a bipartisan resolution (House of Representatives Resolution 1118 at the 117th Congress [2021-2022]) calling for meaningful nutrition education for medical trainees. This was prompted by increasing health care spending attributed to the growing prevalence of nutrition-related diseases and the substantial federal funding via Medicare that supports graduate medical education. In March 2023, medical education professional organizations agreed to identify nutrition competencies for medical education.

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  • Recent research has created normative growth charts for the brain structure of rhesus macaques, filling a gap in understanding nonhuman primate neurodevelopment.
  • The study analyzed 1,522 MRI scans from 1,024 macaques to identify developmental patterns in brain volume, cortical thickness, and surface area throughout their lifespan.
  • These findings not only highlight key milestones in macaque brain development but also allow for meaningful comparisons to human brain maturation, providing a valuable resource for future neuroscience studies.
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The primate brain has evolved specialized visual capacities to navigate complex physical and social environments. Researchers studying cortical circuits underlying these capacities have traditionally favored the use of simplified tasks and brief stimulus presentations in order to isolate cognitive variables with tight experimental control. As a result, operational theories about visual brain function have come to emphasize feature detection, hierarchical stimulus encoding, top-down task modulation, and functional segregation in distinct cortical areas.

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Vision in humans and other primates enlists parallel processing streams in the dorsal and ventral visual cortex, known to support spatial and object processing, respectively. These streams are bridged, however, by a prominent white matter tract, the vertical occipital fasciculus (VOF), identified in both classical neuroanatomy and recent diffusion-weighted magnetic resonance imaging (dMRI) studies. Understanding the evolution of the VOF may shed light on its origin, function, and role in visually guided behaviors.

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Complex behavior entails a balance between taking in sensory information from the environment and utilizing previously learned internal information. Experiments in behaving mice have demonstrated that the brain continually alternates between outward and inward modes of cognition, switching its mode of operation every few seconds. Further, each state transition is marked by a stereotyped cascade of neuronal spiking that pervades most forebrain structures.

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At the International Gynecologic Cancer Society (IGCS) Global Meeting in 2023 held in Seoul, South Korea, we held a Presidential Plenary Session focusing on palliative care (https://www.youtube.com/watch?v=TBDIoQ50xgI).

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There is substantial evidence that neuromodulatory systems critically influence brain state dynamics; however, most work has been purely descriptive. Here, we quantify, using data combining local inactivation of the basal forebrain with simultaneous measurement of resting-state fMRI activity in the macaque, the causal role of long-range cholinergic input to the stabilization of brain states in the cerebral cortex. Local inactivation of the nucleus basalis of Meynert (nbM) leads to a decrease in the energy barriers required for an fMRI state transition in cortical ongoing activity.

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This fMRI study of 126 youth explored whether the neural mechanisms underlying the N-back task, commonly used to examine executive control over the contents of working memory, are associated with individual differences in academic achievement in reading and math. Moreover, the study explored whether these relationships occur regardless of the nature of the stimulus being manipulated in working memory (letters, numbers, nonsense shapes) or whether these relationships are specific to achievement domain and stimulus type (i.e.

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Neurons in the hippocampus exhibit spontaneous spiking activity during rest that appears to recapitulate previously experienced events. While this replay activity is frequently linked to memory consolidation and learning, the underlying mechanisms are not well understood. Recent large-scale neural recordings in mice have demonstrated that resting-state spontaneous activity is expressed as quasi-periodic cascades of spiking activity that pervade the forebrain, with each cascade engaging a high proportion of recorded neurons.

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Genetic diseases affecting the retina can result in partial or complete loss of visual function. Leber's congenital amaurosis (LCA) is a rare blinding disease, usually inherited in an autosomally recessive manner, with no cure. Retinal gene therapy has been shown to improve vision in LCA patients caused by mutations in the RPE65 gene (LCA2).

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Diffusion magnetic resonance imaging (dMRI) has been widely employed to model the trajectory of myelinated fiber bundles in white matter. Increasingly, dMRI is also used to assess local tissue properties throughout the brain. In the cerebral cortex, myelin content is a critical indicator of the maturation, regional variation, and disease related degeneration of gray matter tissue.

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  • The brain's internal dynamics significantly influence how sensory information, like visual stimuli, is encoded, showing that activity patterns occur over several seconds.
  • During passive viewing, visual encoding fluctuates with quasi-periodic spiking cycles, peaking during high arousal states but slowing down during low arousal moments marked by hippocampal ripples.
  • When moving actively, these arousal dynamics change, leading to consistently high visual encoding efficiency without hippocampal activity, suggesting a cycle between external perception and internal memory functions.
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Callous-unemotional (CU) traits are a youth antisocial phenotype hypothesized to be a result of differences in the integration of multiple brain systems. However, mechanistic insights into these brain systems are a continued challenge. Where prior work describes activation and connectivity, new mechanistic insights into the brain's functional connectome can be derived by removing nodes and quantifying changes in network properties (hereafter referred to as computational lesioning) to characterize connectome resilience and vulnerability.

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The primate brain is equipped to learn and remember newly encountered visual stimuli such as faces and objects. In the macaque inferior temporal (IT) cortex, neurons mark the familiarity of a visual stimulus through response modification, often involving a decrease in spiking rate. Here, we investigate the emergence of this neural plasticity by longitudinally tracking IT neurons during several weeks of familiarization with face images.

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Callous-Unemotional (CU) traits are often associated with impairments in perspective taking and cognitive control (regulating goal directed behavior); and adolescents with CU traits demonstrate aberrant brain activation/connectivity in areas underlying these processes. Together cognitive control and perspective taking are thought to link mechanistically to explain CU traits. Because increased cognitive control demands modulate perspective taking ability among both typically developing samples and individuals with elevated CU traits, understanding the neurophysiological substrates of these constructs could inform efforts to alleviate societal costs of antisocial behavior.

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Objective: Self-determination theory suggests that the satisfaction and frustration of basic psychological needs-autonomy, competence, relatedness-are uniquely associated with overall well-being. Undergraduates with attention-deficit/hyperactivity disorder (ADHD) experience more academic-related impairment and are less likely to graduate. Thus, well-being is important to understand and aim to improve in these students.

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The primary aim of this study was to characterize Cognitive Disengagement Syndrome (CDS) symptomatology in youth with spina bifida (SB). One hundred and sixty-nine patients aged 5-19 years old were drawn from clinical cases seen through a multidisciplinary outpatient SB clinic at a children's hospital between 2017 and 2019. Parent-reported CDS and inattention were measured using Penny's Sluggish Cognitive Tempo Scale and the Vanderbilt ADHD Rating Scale.

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Neurons throughout the primate inferior temporal (IT) cortex respond selectively to visual images of faces and other complex objects. The response magnitude of neurons to a given image often depends on the size at which the image is presented, usually on a flat display at a fixed distance. While such size sensitivity might simply reflect the angular subtense of retinal image stimulation in degrees, one unexplored possibility is that it tracks the real-world geometry of physical objects, such as their size and distance to the observer in centimeters.

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Macaque inferior temporal cortex neurons respond selectively to complex visual images, with recent work showing that they are also entrained reliably by the evolving content of natural movies. To what extent does temporal continuity itself shape the responses of high-level visual neurons? We addressed this question by measuring how cells in face-selective regions of the macaque visual cortex were affected by the manipulation of a movie's temporal structure. Sampling a 5-min movie at 1 s intervals, we measured neural responses to randomized, brief stimuli of different lengths, ranging from 800 ms dynamic movie snippets to 100 ms static frames.

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Diffusion magnetic resonance imaging (dMRI) is commonly used to assess the tissue and cellular substructure of the human brain. In the white matter, myelinated axons are the principal neural elements that shape dMRI through the restriction of water diffusion; however, in the gray matter the relative contributions of myelinated axons and other tissue features to dMRI are poorly understood. Here we investigate the determinants of diffusion in the cerebral cortex.

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