Upregulation of Barrel GABAergic Neurons Is Associated with Cross-Modal Plasticity in Olfactory Deficit

Background: Loss of a sensory function is often followed by the hypersensitivity of other modalities in mammals, which secures them well-awareness to environmental changes. Cellular and molecular mechanisms underlying cross-modal sensory plasticity remain to be documented. Methodology/Principal Findings: Multidisciplinary approaches, such as electrophysiology, behavioral task and immunohistochemistry, were used to examine the involvement of specific types of neurons in cross-modal plasticity. We have established a mouse model that olfactory deficit leads to a whisking upregulation, and studied how GABAergic neurons are involved in this cross-modal plasticity. In the meantime of inducing whisker tactile hypersensitivity, the olfactory injury recruits more GABAergic neurons and their fine processes in the barrel cortex, as well as upregulates their capacity of encoding action potentials. The hyperpolarization driven by inhibitory inputs strengthens the encoding ability of their target cells. Conclusion/Significance: The upregulation of GABAergic neurons and the functional enhancement of neuronal networks may play an important role in cross-modal sensory plasticity. This finding provides the clues for developing therapeuti

Defining parasite biodiversity at high latitudes of North America: new host and geographic records for <it>Onchocerca cervipedis</it> (Nematoda: Onchocercidae) in moose and caribou

<p>Abstract</p> <p>Background</p> <p><it>Onchocerca cervipedis</it> is a filarioid nematode of cervids reported from Central America to boreal regions of North America. It is found primarily in subcutaneous tissues of the legs, and is more commonly known as ‘legworm’. Blackflies are intermediate hosts and transmit larvae to ungulates when they blood-feed. In this article we report the first records of <it>O. cervipedis</it> from high latitudes of North America and its occurrence in previously unrecognized host subspecies including the Yukon-Alaska moose (<it>Alces americanus gigas)</it> and the Grant’s caribou (<it>Rangifer tarandus granti</it>).</p> <p>Methods</p> <p>We examined the subcutaneous connective tissues of the metacarpi and/or metatarsi of 34 moose and one caribou for parasitic lesions. Samples were collected from animals killed by subsistence hunters or animals found dead in the Northwest Territories (NT), Canada and Alaska (AK), USA from 2005 to 2012. Genomic DNA lysate was prepared from nematode fragments collected from two moose. The <it>nd5</it> region of the mitochondrial DNA was amplified by PCR and sequenced.</p> <p>Results</p> <p>Subcutaneous nodules were found in 12 moose from the NT and AK, and one caribou from AK. Nematodes dissected from the lesions were identified as <it>Onchocerca cervipedis</it> based on morphology of female and male specimens. Histopathological findings in moose included cavitating lesions with multifocal granulomatous cellulitis containing intralesional microfilariae and adults, often necrotic and partially mineralized. Lesions in the caribou included periosteitis with chronic cellulitis, eosinophilic and lymphoplasmacytic infiltrate, and abundant granulation associated with intralesional adult nematodes and larvae. Sequences of the <it>nd5</it> region (471bp), the first generated for this species, were deposited with Genbank (JN580791 and JN580792). Representative voucher specimens were deposited in the archives of the United States National Parasite Collection.</p> <p>Conclusions</p> <p>The geographic range of <it>O. cervipedis</it> is broader than previously thought, and extends into subarctic regions of western North America<it>,</it> at least to latitude 66°N. The host range is now recognized to include two additional subspecies: the Yukon-Alaska moose and Grant’s caribou. Accelerated climate change at high latitudes may affect vector dynamics, and consequently the abundance and distribution of <it>O. cervipedis</it> in moose and caribou. Disease outbreaks and mortality events associated with climatic perturbations have been reported for other filarioids, such as <it>Setaria tundra</it> in Fennoscandia, and may become an emerging issue for <it>O. cervipedis</it> in subarctic North America.</p

Engaging in an auditory task suppresses responses in auditory cortex

Although systems that are involved in attentional selection have been studied extensively, much less is known about nonselective systems. To study these preparatory mechanisms, we compared activity in auditory cortex that was elicited by sounds while rats performed an auditory task ('engaged') with activity that was elicited by identical stimuli while subjects were awake but not performing a task ('passive'). We found that engagement suppressed responses, an effect that was opposite in sign to that elicited by selective attention. In the auditory thalamus, however, engagement enhanced spontaneous firing rates but did not affect evoked responses. These results indicate that neural activity in auditory cortex cannot be viewed simply as a limited resource that is allocated in greater measure as the state of the animal passes from somnolent to passively listening to engaged and attentive. Instead, the engaged condition possesses a characteristic and distinct neural signature in which sound-evoked responses are paradoxically suppressed