12 research outputs found
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Functional Diversity of Corticothalamic Pathways Underlying Visual Processing
The cerebral cortex and the thalamus are in constant communication with one another, and their interactions are thought to underlie fundamental brain functions such as perception, attention, sleep, cognitive flexibility, and even consciousness. Still, a multitude of questions remains as to how corticothalamic interactions subserve these functions. This dissertation explores one major aspect of these interactions - how the cortex communicates with the thalamus, using the mouse visual system as model. This is an area in which considerable groundwork has been laid by decades of research into the underlying anatomy and physiology of these connections, which have led to influential hypotheses about how those attributes may relate to function. Yet, many of these hypotheses have been left untested, due to challenges and technical limitations in selectively perturbing different corticothalamic pathways and assessing their in vivo functions in an awake animal. In this dissertation, modern advances in mouse transgenics, extracellular electrophysiology, and circuit manipulation are harnessed to directly assess how distinct populations of corticothalamic neurons contribute to visual thalamic processing in vivo. Chapter 1 explores the role that a unique population of corticothalamic neurons in layer 6 of the mouse primary visual cortex play in the dorsolateral geniculate nucleus and the pulvinar, which represent two distinct classes of visual thalamic nuclei. By using optogenetics to selectively stimulate these neurons, we find that they act similarly upon both classes of thalamic nuclei, yet their influence in both is highly dynamic and dependent upon the context of their activation. In Chapter 2, the endogenous function of these layer 6 corticothalamic neurons is further examined with optogenetic inactivation and contrasted with that of an additional corticothalamic population in cortical layer 5 that exclusively projects to the pulvinar. We find novel evidence in support of longstanding hypotheses that layer 5 corticothalamic projections “drive” visual responses in the pulvinar, whereas the layer 6 projections play a fundamentally “modulatory” role. Altogether, this dissertation reveals how functionally distinct corticothalamic pathways influence the visual thalamus and suggests fundamental principles in how corticothalamic communication is organized for sensory processing in the awake, behaving animal
Recommended from our members
Functional Diversity of Corticothalamic Pathways Underlying Visual Processing
The cerebral cortex and the thalamus are in constant communication with one another, and their interactions are thought to underlie fundamental brain functions such as perception, attention, sleep, cognitive flexibility, and even consciousness. Still, a multitude of questions remains as to how corticothalamic interactions subserve these functions. This dissertation explores one major aspect of these interactions - how the cortex communicates with the thalamus, using the mouse visual system as model. This is an area in which considerable groundwork has been laid by decades of research into the underlying anatomy and physiology of these connections, which have led to influential hypotheses about how those attributes may relate to function. Yet, many of these hypotheses have been left untested, due to challenges and technical limitations in selectively perturbing different corticothalamic pathways and assessing their in vivo functions in an awake animal. In this dissertation, modern advances in mouse transgenics, extracellular electrophysiology, and circuit manipulation are harnessed to directly assess how distinct populations of corticothalamic neurons contribute to visual thalamic processing in vivo. Chapter 1 explores the role that a unique population of corticothalamic neurons in layer 6 of the mouse primary visual cortex play in the dorsolateral geniculate nucleus and the pulvinar, which represent two distinct classes of visual thalamic nuclei. By using optogenetics to selectively stimulate these neurons, we find that they act similarly upon both classes of thalamic nuclei, yet their influence in both is highly dynamic and dependent upon the context of their activation. In Chapter 2, the endogenous function of these layer 6 corticothalamic neurons is further examined with optogenetic inactivation and contrasted with that of an additional corticothalamic population in cortical layer 5 that exclusively projects to the pulvinar. We find novel evidence in support of longstanding hypotheses that layer 5 corticothalamic projections “drive” visual responses in the pulvinar, whereas the layer 6 projections play a fundamentally “modulatory” role. Altogether, this dissertation reveals how functionally distinct corticothalamic pathways influence the visual thalamus and suggests fundamental principles in how corticothalamic communication is organized for sensory processing in the awake, behaving animal
Plasmodium infection in African penguins (Sphenicus demersus)
Avian malaria, caused by Plasmodium spp. infection, is the most important cause of mortality of captive penguins in open-air colonies in the United States. Additionally, avian malaria poses an obstacle to successful rehabiliation of penguins in several wild populations. Infected Culex spp. mosquitoes transmit the disease and a single malarial sporozoite is sufficient to initiate infection. Avian malaria occurs worldwide due to extensive bird migration patterns and wide geographic host ranges. Birds that evolved in the absence of mosquitoes, such as African black-footed penguins (Sphenicus demersus) serve as aberrant hosts, with resultant high morbidity and mortality rates after exposure. While Plasmodium relictum and P. elongatum appear to be the Plasmodium spp. implicated in malarial infections in captive black-footed penguins in North American, P. juxtanucleare has been associated with mortality in free-ranging African penguins. Penguins commonly die without displaying clinical signs or parasitemia. Typical antemortem clinical signs of malaria infection include anorexia, depression, vomiting, dyspnea, seizing, and sudden death. Premonitory signs of infection are often subtle and frequently are lacking altogether. Classic pathological lesions have been described for avian malarial infections in black-footed penguins and include splenomegaly, edematous lungs, subcutaneous edema, and hydropericardium. An ELISA for detecting anti-Plasmodium spp. has been developed to assist in the diagnosis of avian malaria and an anticircumsporozoite DNA vaccine has been refined for experimental use in captive African penguins in North America. Plasmodium juxtacunleare-associated mortality in rehabilitated free-ranging black-footed penguins verus infection in non-rehabilitated wild penguins has also been examined. The objective of this paper is to present a comprehensive report on various aspects of Plasmodium spp. infections in captive African black-footed penguins in North America. A special section at the end of the report is devoted to a discussion of avian malaria in free-ranging black-footed penguins
Intact reflexive but deficient voluntary social orienting in autism spectrum disorder
Impairment in social interactions is a primary characteristic of people diagnosed with autism spectrum disorder (ASD). Although these individuals tend to orient less to naturalistic social cues than do typically developing (TD) individuals, laboratory experiments testing social orienting in ASD have been inconclusive, possibly because of a failure to fully isolate reflexive (stimulus-driven) and voluntary (goal-directed) social orienting processes. The purpose of the present study was to separately examine potential reflexive and/or voluntary social orienting differences in individuals with ASD relative to TD controls. Subjects (ages 7-14) with high-functioning ASD and a matched control group completed three gaze cueing tasks on an iPad in which individuals briefly saw a face with averted gaze followed by a target after a variable delay. Two tasks were 100% predictive with either all congruent (target appears in gaze direction) or all incongruent (target appears opposite from gaze direction) trials, respectively. Another task was non-predictive with these same trials (half congruent and half incongruent) intermixed randomly. Response times (RTs) to the target were used to calculate reflexive (incongruent condition RT – congruent condition RT) and voluntary (non-predictive condition RT – predictive condition RT) gaze cueing effects. Subjects also completed two additional non-social orienting tasks (ProPoint and AntiPoint). Subjects with ASD demonstrate intact reflexive but deficient voluntary gaze following. Similar results were found in a separate test of non-social orienting. This suggests problems with using social cues, but only in a goal-directed fashion, in our sample of high-functioning individuals with ASD. Such findings may not only explain inconclusive previous findings but more importantly be critical for understanding social dysfunctions in ASD and for developing future interventions
Effects of ultraviolet radiation on plasma 25-hydroxyvitamin D3 concentrations in corn snakes (Elaphe guttata)
OBJECTIVE: To determine whether corn snakes exposed to UVB radiation have increased plasma 25-hydroxyvitamin D3 concentrations, compared with control snakes. ANIMALS: 12 corn snakes (Elaphe guttata). PROCEDURES: After an acclimation period in individual enclosures, a blood sample was collected from each snake for assessment of plasma 25-hydroxyvitamin D3 concentration. Six snakes were provided with no supplemental lighting, and 6 snakes were exposed to light from 2 full-spectrum coil bulbs. By use of a radiometer-photometer, the UVA and UVB radiation generated by the bulbs were measured in each light-treated enclosure at 3 positions at the basking surface and at 2.54 cm (1 inch) below each bulb surface; the arithmetic mean values for the 3 positions at the basking surface and each individual bulb surface were calculated immediately after the start of the study and at weekly intervals thereafter. At the end of the study (day 28), another blood sample was collected from each snake to determine plasma 25-hydroxyvitamin D3 concentration. RESULTS: Mean +/- SD plasma concentration of 25-hydroxyvitamin D3 in snakes that were provided with supplemental lighting (196 +/- 16.73 nmol/L) differed significantly from the value in control snakes (57.17 +/- 15.28 nmol/L). Mean exposure to UVA or UVB did not alter during the 4-week study period, although the amount of UVA recorded near the bulb surfaces did change significantly. CLINICAL RELEVANCE: These findings have provided important insight into the appropriate UV radiation requirements for corn snakes. Further investigation will be needed before exact husbandry requirements can be determined
Lessons from the Stories of Women in Neuroscience.
Women have been contributing to the field of neuroscience since its inception, but their accomplishments are often overlooked. Lack of recognition, among other issues, has led to progressively fewer women at each academic stage; although half of neuroscience graduate students are women, women comprise less than one-third of neuroscience faculty, and even fewer full professors. Those who reach this level continue to struggle to get their work recognized. Women from historically excluded backgrounds are even more starkly underrepresented and face added challenges related to racial, ethnic, and other biases. To increase the visibility of women in neuroscience, promote their voices, and learn about their career journeys, we created Stories of Women in Neuroscience (Stories of WiN). Stories of WiN shares the scientific and personal stories of women neuroscientists with diverse backgrounds, identities, research interests, and at various career stages. From >70 women highlighted thus far, a major theme has emerged: there is not a single archetype of a woman neuroscientist, nor a single path to "success." Yet, through these diverse experiences run common threads, such as the importance of positive early research experiences, managing imposter syndrome, the necessity of work-life balance, and the challenges of fitting into-or resisting-the "scientist mold" within a patriarchal, racialized academic system. These commonalities reveal important considerations for supporting women neuroscientists. Through the lens of women highlighted by Stories of WiN, we explore the similarities among their journeys and detail specific actionable items to help encourage, support, and sustain women in neuroscience