Survivors of preterm birth are at high risk of pervasive cognitive and learning impairments, suggesting disrupted early brain development. The limits of viability for preterm birth encompass the third trimester of pregnancy, a "precritical period" of activity-dependent development characterized by the onset of spontaneous and evoked patterned electrical activity that drives neuronal maturation and formation of cortical circuits. Reduced background activity on electroencephalogram (EEG) is a sensitive marker of brain injury in human preterm infants that predicts poor neurodevelopmental outcome. We studied a rodent model of very early hypoxic-ischemic brain injury to investigate effects of injury on both general background and specific patterns of cortical activity measured with EEG. EEG background activity is depressed transiently after moderate hypoxia-ischemia with associated loss of spindle bursts. Depressed activity, in turn, is associated with delayed expression of glutamate receptor subunits and transporters. Cortical pyramidal neurons show reduced dendrite development and spine formation. Complementing previous observations in this model of impaired visual cortical plasticity, we find reduced somatosensory whisker barrel plasticity. Finally, EEG recordings from human premature newborns with brain injury demonstrate similar depressed background activity and loss of bursts in the spindle frequency band. Together, these findings suggest that abnormal development after early brain injury may result in part from disruption of specific forms of brain activity necessary for activity-dependent circuit development.

Paralysis due to spinal cord injury can severely limit motor function and independence. This review summarizes different approaches to electrical stimulation of the spinal cord designed to restore motor function, with a brief discussion of their origins and the current understanding of their mechanisms of action. Spinal stimulation leads to impressive improvements in motor function along with some benefits to autonomic functions such as bladder control. Nonetheless, the precise mechanisms underlying these improvements and the optimal spinal stimulation approaches for restoration of motor function are largely unknown. Finally, spinal stimulation may augment other therapies that address the molecular and cellular environment of the injured spinal cord. The fact that several stimulation approaches are now leading to substantial and durable improvements in function following spinal cord injury provides a new perspectives on the previously "incurable" condition of paralysis.

The overlap hypothesis of mixture perception is based on the observation that mixtures of perceptually similar odorants tend to smell different from their components (configural), whereas mixtures of dissimilar odorants smell like their components (elemental). Because input patterns of perceptually similar odorants tend to overlap more than dissimilar ones, it has been hypothesized that component pattern overlap can predict a mixture's perceptual quality, with high overlap predicting a configural response and low overlap an elemental response. The authors used 7 pairs of odorants chosen for different degrees of overlap in their monomolecular 2-deoxyglucose activation patterns to test the theory in a go/no-go behavioral assay that measured generalization from binary mixtures to components. The authors show that individual component odorant input patterns are not sufficient to predict mixture quality, falsifying the overlap hypothesis. An important finding is that different odorant pairs with similar glomerular overlap showed opposite behavioral-perceptual responses, suggesting nonlinear effects at the receptor or glomerular level or the critical involvement of higher order areas. Thus, the authors posit that imaging the mixtures themselves may provide additional information needed to reliably predict mixture quality.

No abstract

A neural prosthesis is a device that aims to restore or replace the functions of the nervous system that are lost to disease or injury. Examples include devices to improve hearing, vision, motor and cognitive functions. Neural prostheses artificially stimulate the nervous system to convey sensory information, activate paralysed muscles or modulate the excitability of neural circuits to improve conditions such as chronic pain, epilepsy or tremor. Some neuroprostheses also record activity from the nervous system, which can be useful for patients who have difficulty moving or communicating. These devices can decipher the intention of the user or detect ongoing brain events such as seizures by recording neural signals directly from the brain. Emerging neuroprostheses aim to ‘close the loop’ using recorded neural activity to control stimulation delivered elsewhere in the nervous system with the goal of improving function. Key Concepts Neural prostheses aim to replace lost function or control activity within the nervous system following injury or disease. Sensory neural prostheses transduce external events (e.g. sound, light) into artificial stimulation delivered to the nervous system. Motor neural prostheses aim to restore functional movement to weak or paralysed muscles. Neuromodulatory devices utilise electrical stimulation to modulate the excitability of neural circuits to improve symptoms of neurological diseases such as pain, tremor and the occurrence of seizures. Recording neuroprostheses aim to detect the user's intention or brain state in order to enable communication or control of external devices. Closed‐loop neuroprostheses utilise neural recording to control functional or symptom‐relieving stimulation. Methods are emerging for optical and magnetic stimulation of the nervous system to supplement the electrical stimulation techniques currently in use.