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"space perception."
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Coupling of functional connectivity and regional cerebral blood flow reveals a physiological basis for network hubs of the human brain
Human brain functional networks contain a few densely connected hubs that play a vital role in transferring information across regions during resting and task states. However, the relationship of these functional hubs to measures of brain physiology, such as regional cerebral blood flow (rCBF), remains incompletely understood. Here, we used functional MRI data of blood-oxygenation-level–dependent and arterial-spin–labeling perfusion contrasts to investigate the relationship between functional connectivity strength (FCS) and rCBF during resting and an N -back working-memory task. During resting state, functional brain hubs with higher FCS were identified, primarily in the default-mode, insula, and visual regions. The FCS showed a striking spatial correlation with rCBF, and the correlation was stronger in the default-mode network (DMN; including medial frontal-parietal cortices) and executive control network (ECN; including lateral frontal-parietal cortices) compared with visual and sensorimotor networks. Moreover, the relationship was connection–distance dependent; i.e., rCBF correlated stronger with long-range hubs than short-range ones. It is notable that several DMN and ECN regions exhibited higher rCBF per unit connectivity strength (rCBF/FCS ratio); whereas, this index was lower in posterior visual areas. During the working-memory experiment, both FCS–rCBF coupling and rCBF/FCS ratio were modulated by task load in the ECN and/or DMN regions. Finally, task-induced changes of FCS and rCBF in the lateral-parietal lobe positively correlated with behavioral performance. Together, our results indicate a tight coupling between blood supply and brain functional topology during rest and its modulation in response to task demands, which may shed light on the physiological basis of human brain functional connectome.
Journal Article
Serial dependence in visual perception
Visual input is often noisy and discontinuous, even though the physical environment is generally stable. The authors show that the visual system trades off change sensitivity to capitalize on physical continuity via serial dependence: present perception is biased toward past visual input. This bias is modulated by attention and governed by a spatiotemporally-tuned operator, a continuity field.
Visual input often arrives in a noisy and discontinuous stream, owing to head and eye movements, occlusion, lighting changes, and many other factors. Yet the physical world is generally stable; objects and physical characteristics rarely change spontaneously. How then does the human visual system capitalize on continuity in the physical environment over time? We found that visual perception in humans is serially dependent, using both prior and present input to inform perception at the present moment. Using an orientation judgment task, we found that, even when visual input changed randomly over time, perceived orientation was strongly and systematically biased toward recently seen stimuli. Furthermore, the strength of this bias was modulated by attention and tuned to the spatial and temporal proximity of successive stimuli. These results reveal a serial dependence in perception characterized by a spatiotemporally tuned, orientation-selective operator—which we call a continuity field—that may promote visual stability over time.
Journal Article
Dark and magical places : the neuroscience of navigation
\"An illuminating examination of how the brain helps us to understand and navigate space-and why, sometimes, it doesn't work the way it should. Navigation is one of the most complex tasks our brains perform. And we do it countless times a day-as we drive across town to the airport, or traverse the maze of a supermarket, or walk within our own homes. But why is it that some people are lost on their own street and others can seamlessly navigate a new city after visiting it once? Fueled by his own spatial shortcomings, Christopher Kemp describes the brain regions that orient us in space and the specialized neurons-place cells and grid cells-that do it. He explains how the brain plans routes, recognizes landmarks, and makes sure we leave a room through a door instead of a painting. Along the way, he meets the scientists trying to understand the mental maps of modern humans, and Neanderthals, and lost people everywhere. Dark and Magical Places is an informed and entertaining journey into the mysteries of the mind\"-- Provided by publisher.
Book
Exercise training increases size of hippocampus and improves memory
The hippocampus shrinks in late adulthood, leading to impaired memory and increased risk for dementia. Hippocampal and medial temporal lobe volumes are larger in higher-fit adults, and physical activity training increases hippocampal perfusion, but the extent to which aerobic exercise training can modify hippocampal volume in late adulthood remains unknown. Here we show, in a randomized controlled trial with 120 older adults, that aerobic exercise training increases the size of the anterior hippocampus, leading to improvements in spatial memory. Exercise training increased hippocampal volume by 2%, effectively reversing age-related loss in volume by 1 to 2 y. We also demonstrate that increased hippocampal volume is associated with greater serum levels of BDNF, a mediator of neurogenesis in the dentate gyrus. Hippocampal volume declined in the control group, but higher preintervention fitness partially attenuated the decline, suggesting that fitness protects against volume loss. Caudate nucleus and thalamus volumes were unaffected by the intervention. These theoretically important findings indicate that aerobic exercise training is effective at reversing hippocampal volume loss in late adulthood, which is accompanied by improved memory function.
Journal Article
Bilateral vestibulopathy affects spatial and temporal perception
This study assessed impairments in spatial and temporal perception in individuals with bilateral vestibulopathy (BVP). A total of 30 BVP subjects and 35 healthy controls (CTL) participated in a series of tests to assess their perception of distance (1–6 meters), angle (90–360 degrees), duration (2–10 seconds), and a combination of distance and angle during a triangle completion task (TCT). When performing distance and angle perception tasks separately, the BVP subjects showed larger errors than the CTL subjects. During the TCT, the BVP subjects walked longer paths and exhibited greater angle deviations compared to the CTL subjects. The angle deviations of the BVP subjects during the TCT were larger than when the angle perception task was performed separately. Moreover, the BVP subjects demonstrated accurate time interval perception, whereas the CTL subjects did not. Although the vestibular system is crucial for balance and spatial awareness, the proprioceptive system, in combination with visual and cognitive strategies, as well as motor efference copies, can help individuals with labyrinthine defects in separately perceiving distances and angles. However, this compensatory approach becomes less effective when these tasks are combined. These findings are relevant for space (planetary) exploration because exposure to microgravity mimics loss of vestibular otolith function.
Journal Article
Spatial cognition, spatial perception : mapping the self and space
How does knowledge of the body in space relate to an understanding of space itself? Spatial cognition is discussed from two closely related perspectives: the internal mapping of external stimuli (e.g., landmarks and sensory perception of environmental information) and the internal mapping of internally perceived stimuli (e.g., kinesthetic and visual imagery), and their subsequent effects on behaviour. Clarification of what spatial information is present in most perceptual processes and how this is used cognitively in relation to the self in space is then established. Major points and controversies of the various models are discussed, along with evolutionary perspectives of spatial perception and object recognition and comparisons between human and non-human spatial cognitive abilities and behaviours. Written for postgraduate students and researchers, the authors present theoretical and experimental accounts at multiple levels of analysis - perceptual, behavioural and cognitive - providing a thorough review of the mechanisms of spatial cognition.
Book
Spatial representation in the hippocampal formation: a history
Moser, Moser and McNaughton provide a historical overview describing how ideas about integration of self-motion cues have shaped our understanding of spatial representation in hippocampal–entorhinal systems, from the discovery of place cells in the 1970s to contemporary studies of spatial coding in intermingled and interacting cell types within complex circuits.
Since the first place cell was recorded and the cognitive-map theory was subsequently formulated, investigation of spatial representation in the hippocampal formation has evolved in stages. Early studies sought to verify the spatial nature of place cell activity and determine its sensory origin. A new epoch started with the discovery of head direction cells and the realization of the importance of angular and linear movement-integration in generating spatial maps. A third epoch began when investigators turned their attention to the entorhinal cortex, which led to the discovery of grid cells and border cells. This review will show how ideas about integration of self-motion cues have shaped our understanding of spatial representation in hippocampal–entorhinal systems from the 1970s until today. It is now possible to investigate how specialized cell types of these systems work together, and spatial mapping may become one of the first cognitive functions to be understood in mechanistic detail.
Journal Article