Neural representations of the external world are constructed and updated in a manner that depends on behavioral context. For neocortical networks, this contextual information is relayed by a diverse range of neuromodulatory systems, which govern attention and signal the value of internal state variables such as arousal, motivation, and stress. Neuromodulators enable cortical circuits to differentially process specific stimuli and modify synaptic strengths in order to maintain short- or long-term memory traces of significant perceptual events and behavioral episodes. One of the most important subcortical neuromodulatory systems for attention and arousal is the noradrenergic locus coeruleus. Here we report that the noradrenergic system can enhance behavior in rats performing a self-initiated auditory recognition task, and optogenetic stimulation of noradrenergic locus coeruleus neurons accelerated the rate at which trained rats began correctly responding to a change in reward contingency. Animals successively progressed through distinct behavioral epochs, including periods of perseverance and exploration that occurred much more rapidly when animals received locus coeruleus stimulation. In parallel, we made recordings from primary auditory cortex and found that pairing tones with locus coeruleus stimulation led to a similar set of changes to cortical tuning profiles. Thus both behavioral and neural responses go through phases of adjustment for exploring and exploiting environmental reward contingencies. Furthermore, behavioral engagement does not necessarily recruit optimal locus coeruleus activity.

Cochlear implants are one of the most successful neuroprosthetic devices that have been developed to date. Profoundly deaf patients can achieve speech perception after complete loss of sensory input. Despite the improvements many patients experience, there is still a large degree of outcome variability. It has been proposed that central plasticity may be a major factor in the different levels of benefit that patients experience. However, the neural mechanisms of how plasticity impacts cochlear implant learning and the degree of plasticity's influence remain unknown. Here, we review the human and animal research on three of the main ways that central plasticity affects cochlear implant outcomes.

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Cochlear implants are neuroprosthetic devices that can provide hearing to deaf patients1. Despite signi cant bene ts offered by cochlear implants, there are highly variable outcomes in how quickly hearing is restored and perceptual accuracy after months or years of use2,3. Cochlear implant use is believed to require neuroplasticity within the central auditory system, and differential engagement of neuroplastic mechanisms might contribute to outcome variability4-7. Despite extensive studies on how cochlear implants activate the auditory system4,8-12, our understanding of cochlear implant-related neuroplasticity remains limited. One potent factor enabling plasticity is the neuromodulator norepinephrine from the brainstem locus coeruleus. Here we examined behavioral responses and neural activity in locus coeruleus and auditory cortex of deafened rats tted with multi-channel cochlear implants. Animals were trained on a reward-based auditory task, with considerable individual differences of learning rates and maximum performance. Photometry from locus coeruleus predicted when implanted subjects would begin responding to sounds and longer-term perceptual accuracy, which were augmented by optogenetic locus coeruleus stimulation. Auditory cortical responses to cochlear implant stimulation re ected behavioral performance, with enhanced responses to rewarded stimuli and decreased distinction between unrewarded stimuli. Adequate engagement of central neuromodulatory systems is thus a potential clinically-relevant target for optimizing neuroprosthetic device use. Main TextCochlear implants are major biomedical devices, and an exemplary success story of the application of foundational neuroscience research and use of brain-machine interface neuroprosthetics to treat a widespread neurological condition: hearing loss 1-5 . However, the auditory bene ts provided by a cochlear implant are not instantaneous, in contrast to the ampli cation of acoustic input provided by commercial hearing aids. Some patients acquire a degree of speech comprehension with the cochlear implant a few hours after activation, but many patients unfortunately require months or even years post-implantation to achieve optimum levels of speech perception 2,3 . There are many open questions about the behavioral characteristics of this adaptation process in human listeners and the underlying neurophysiological changes 13,14 . Measuring how cochlear implants activate the central auditory system or other brain areas is technically complicated due to signi cant limitations with imaging in patients with implanted metallic medical devices 15 . Historically there have also been considerable challenges with experimental animal models of cochlear implant use, especially with the aims of monitoring and manipulating neural activity in implanted freely-behaving subjects. Here we addressed these issues by utilizing our recently-developed system for studying behaviorally-and physiologically-validated cochlear implant use in rats 16 , and examined neuromodulation and plasti...

Currently, the accepted method for Q fever serodiagnosis is indirect immunofluorescent antibody assay (IFA) using the whole cell antigen. In this study, we prepared the recombinant antigen of the 27-kDa outer membrane protein (Com1) which has been shown to be recognized by Q fever patient sera. The performance of recombinant Com1 was evaluated in ELISA by IFA confirmed serum samples. Due to the low titers of IgG and IgM in Q fever patients, the standard ELISA signals were further amplified by using biotinylated anti-human IgG or IgM plus streptavidin-HRP polymer. The modified ELISA can detect 88% (29 out of 33) of Q fever patient sera collected from Marines deployed to Iraq. Less than 5% (5 out of 156) of the sera from patients with other febrile diseases reacted with the Com1. These results suggest that the modified ELISA using Com1 may have the potential to improve the detection of Q fever specific antibodies.