Progress in brain research
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Review
Brain plasticity and functional losses in the aged: scientific bases for a novel intervention.
Aging is associated with progressive losses in function across multiple systems, including sensation, cognition, memory, motor control, and affect. The traditional view has been that functional decline in aging is unavoidable because it is a direct consequence of brain machinery wearing down over time. In recent years, an alternative perspective has emerged, which elaborates on this traditional view of age-related functional decline. ⋯ We found that older adults could learn the training program quickly, and could use it entirely unsupervised for the majority of the time required. Pre- and posttesting documented a significant improvement in memory within the training group (effect size 0.41, p<0.0005), with no significant within-group changes in a time-matched computer using active control group, or in a no-contact control group. Thus, a brain-plasticity-based intervention targeting normal age-related cognitive decline may potentially offer benefit to a broad population of older adults.
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Visual shape recognition--the ability to recognize a wide variety of shapes regardless of their size, position, view, clutter and ambient lighting--is a remarkable ability essential for complex behavior. In the primate brain, this depends on information processing in a multistage pathway running from primary visual cortex (V1), where cells encode local orientation and spatial frequency information, to the inferotemporal cortex (IT), where cells respond selectively to complex shapes. A fundamental question yet to be answered is how the local orientation signals (in V1) are transformed into selectivity for complex shapes (in IT). ⋯ Next, we found that responses to complex shapes were dictated by the curvature at a specific boundary location within the shape. Finally, using basis function decoding, we demonstrated that an ensemble of V4 neurons could successfully encode complete shapes as aggregates of boundary fragments. These findings identify curvature as a basis of shape representation in area V4 and provide insights into the neurophysiological basis for the salience of convex curves in shape perception.
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In order to study cerebral activity related to preparation and execution of movement, evoked and induced brain electrical activities were compared to each other and to fMRI results in voluntary self-paced movements. Also, the event-related desynchronization and synchronization (ERD/ERS) were studied in complex movements with various degrees of cognitive load. The Bereitschaftspotential (BP) and alpha (8-12 Hz) and beta (16-24 Hz) ERD/ERS rhythms in self-paced simple movements were analyzed in 14 epilepsy surgery candidates. ⋯ Some sites were only active in the task with the increased demand on executive functions. In the temporal neocortex only, the oscillatory, but not the evoked, activity was recorded in the self-paced movement. The temporal appearance of changes of oscillatory activities in the self-paced movement task as well as in the cued movement task with an increased load of executive functions raises the interesting question of the role of this region in cognitive-movement information processing.
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Spinal reflexes dominate cardiovascular control after spinal cord injury (SCI). These reflexes are no longer restrained by descending control and they can be impacted by degenerative and plastic changes within the injured cord. Autonomic dysreflexia is a condition of episodic hypertension that stems from spinal reflexes initiated by sensory input entering the spinal cord caudal to the site of injury. ⋯ One such treatment is an antibody to the integrin CD11d expressed by inflammatory leukocytes that enter the cord acutely after injury and cause significant secondary damage. This antibody blocks integrin-mediated leukocyte entry, resulting in greatly reduced white-matter damage and decreased autonomic dysreflexia after cord injury. Understanding the mechanisms for autonomic dysreflexia will provide us with strategies for treatments that, if given early after cord injury, can prevent this serious disorder from developing.
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Near-death experiences (NDEs) have become the focus of much interest in the last 30 years or so. Such experiences can occur both when individuals are objectively near to death and also when they simply believe themselves to be. The experience typically involves a number of different components including a feeling of peace and well-being, out-of-body experiences (OBEs), entering a region of darkness, seeing a brilliant light, and entering another realm. ⋯ Psychological theories include the proposal that the NDE is a dissociative defense mechanism that occurs in times of extreme danger or, less plausibly, that the NDE reflects memories of being born. Finally, a wide range of organic theories of the NDE has been put forward including those based upon cerebral hypoxia, anoxia, and hypercarbia; endorphins and other neurotransmitters; and abnormal activity in the temporal lobes. Finally, the results of studies of NDEs in cardiac arrest survivors are reviewed and the implications of these results for our understanding of mind-brain relationships are discussed.