Browsing by Subject "Neurophysiology"
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Item Behavioral and molecular mechanisms of pheromone transmission in the honey bee (Apis mellifera)(2017-08) Ma, Rong, Ph. D.; Mueller, Ulrich G.; Hofmann, Johann; Gilbert, Lawrence E; Jha, Shalene; Grozinger, Christina MThe European honey bee (Apis mellifera) has a sophisticated system of pheromonal signals that mediate a wide range of behaviors important for their fitness, including reproductive dominance, nest defense, and cooperative brood care. In honey bees, there are two distinct pheromones emitted by larvae, brood pheromone and (E)-beta-ocimene. By integrating behavior, chemical ecology, and transcriptomics, this dissertation analyzes several key stages in signal transmission in a systematic effort to understand how these two pheromones affect behavior, and in the process, generates a synthetic understanding of a highly complex system of communication. Previous studies have explored behavioral and gene expression patterns related to honey bee pheromones; however, none have compared the roles that two divergent pheromones from a common source play in rapid regulation of foraging behavior. Furthermore, while previous studies have investigated the mechanisms of pheromone detection and the factors involved in regulation of foraging behavior, it remains unclear how individual responses to pheromone exposure scales to colony-level changes in behavior. By investigating the behavioral, physiological, and genomic influences of honey bee chemical communication, this dissertation links phenotypic plasticity in behavior to gene expression profiles in the brain and provides insights into the evolution of a sophisticated chemical language.Item Delineating abnormal coordination patterns in post-stroke gait : a multidisciplinary approach(2019-01-23) Akbas, Tunc; Sulzer, James S.; Neptune, Richard R.; Deshpande, Ashish; Jones, Theresa; Djurdjanovic, DraganStroke is the largest cause of long-term disability in U.S. where majority of the survivors experience impairments such as muscle weakness, spasticity and abnormal coordination. Stiff-Knee gait (SKG) is an incessant disability defined by the reduced knee flexion during swing. The abnormal neuromuscular mechanisms governing the interactions between impairments during SKG is still not clear. This work attempts to reveal the causal relationship between the specific influences of different impairments on post-stroke gait. Specifically, it delineates the underlying neuromuscular mechanisms behind observed increased hip abduction in SKG. The results indicate that hip abduction is part of an abnormal coordination pattern, instead of a presumed compensation for reduced knee flexion. This result is supported by previous work observing coupled knee flexion and hip abduction motions during SKG following pre-swing knee flexion torque perturbations. I hypothesized the underlying mechanism behind excessive hip abduction is due to an involuntary mechanism between quadriceps and abductor muscles which is initiated by quadriceps hyperreflexia. The results obtained from neuromusculoskeletal modeling and simulation suggest an involuntary coupled response between estimated rectus femoris (RF) and gluteus medius (GMed) activations following simulated peak RF fiber stretch velocity, suggesting an abnormal cross-planar reflex coupling initiated by excessive RF stretch reflex response. We have elicited RF reflex responses in SKG to identify the association between RF hyperreflexia and severity of the SKG excluding the influence of increased voluntary RF activity. Our results indicate a strong negative correlation between RF H-reflex response and reduced peak knee flexion angle in SKG, revealing the distinctive influence of spasticity in SKG. This novel framework delineates the abnormal neuromuscular mechanisms behind the excessive hip abduction in post-stroke gait using biomechanics, neuromusculoskeletal simulations and neurophysiological perturbations. The results obtained from this dissertation could improve lower-limb interventions for gait rehabilitation following stroke by introducing quantified measures of abnormal coordination in SKG and improve the development of subject-specific assistive technology targeting impairments to restore healthy gait.Item Effects of experience and novelty on sexual behavior and associated neuronal activity in male Japanese quail(2008-08) Can, Adem, 1977-; Domjan, Michael, 1947-; Delville, YvonIn many behavioral paradigms, repeated exposures to a particular stimulus or event results in lower immediate early gene (IEG) expression. First, it was investigated if a similar reduction in IEG expression in the brain areas controlling male sexual behaviors would be observed after repeated copulation experiences in male Japanese quail. The results showed that IEG expression, as assessed by egr-1 immunoreactivity, did not increase in the POM, the BST, or the PAG after a copulation episode in highly sexually experienced subjects. One possibility was that the pattern of initial elevation of neuronal activity during the early trials of sexual interactions and the lack of increase in IEG expression later was associated with the novelty of sexual stimuli. While early exposures to certain stimuli constitute a new learning experience, the significance of such exposures would be lower as the level of experience increases. It was hypothesized that the introduction of a novel stimulus would increase the IEG expression in the POM, the BST and the PAG of experienced subjects. To evaluate this prediction, subjects were tested to see if they learn to respond to females decorated with distinct novel artificial cues after repeated exposures. The results showed that control subjects that did not have sexual experiences with decorated females discriminate against such females and directed their responses to normal females. Trained subjects did not show such preferences and responded to both types of females. In the next experiment, contrary to the prediction, no increase in IEG expression was observed after the introduction of the novel stimulus. This might be due to lower sexual motivation in subjects exposed to novel females. Effects of sexual experience were also tested in the catecholaminergic system. It was hypothesized that TH innervation in the POM and the BST would increase as a result of sexual experience. IEG expression in the catecholaminergic areas was predicted to be lower after repeated sexual experiences. The results showed no effect of experience in either tyrosine hydroxylase (TH) innervation, nor TH-egr-1 colocalization. These findings suggest that experience-related changes in male sexual behavior may be mediated by a different neurotransmitter system.Item Predictive Feedback Can Account for Biphasic Responses in the Lateral Geniculate Nucleus(Public Library of Science, 2009-05-01) Jehee, Janneke F. M.; Ballard, Dana H.Biphasic neural response properties, where the optimal stimulus for driving a neural response changes from one stimulus pattern to the opposite stimulus pattern over short periods of time, have been described in several visual areas, including lateral geniculate nucleus (LGN), primary visual cortex (V1), and middle temporal area (MT). We describe a hierarchical model of predictive coding and simulations that capture these temporal variations in neuronal response properties. We focus on the LGN-V1 circuit and find that after training on natural images the model exhibits the brain's LGN-V1 connectivity structure, in which the structure of V1 receptive fields is linked to the spatial alignment and properties of center-surround cells in the LGN. In addition, the spatio-temporal response profile of LGN model neurons is biphasic in structure, resembling the biphasic response structure of neurons in cat LGN. Moreover, the model displays a specific pattern of influence of feedback, where LGN receptive fields that are aligned over a simple cell receptive field zone of the same polarity decrease their responses while neurons of opposite polarity increase their responses with feedback. This phase-reversed pattern of influence was recently observed in neurophysiology. These results corroborate the idea that predictive feedback is a general coding strategy in the brain.Item Temporal dynamics of motion and choice signals in area MT(2020-05-06) Levi, Aaron Joseph; Huk, Alexander C.; Colgin, Laura; Geisler, Wilson; Priebe, Nicholas; Seidemann, EyalSensory encoding is the fundamental front-end to our perceptual experience that ultimately guides our thoughts and actions. In neuroscience, vision has been the primary model system of study for how information about our external environment is represented in the brain. In particular, the study of sensory decision-making has often combined psychophysics and electrophysiology in nonhuman primates to elucidate the neural underpinnings of perception and action. The middle temporal (MT) area has been essential to this process by establishing a causal link between neural encoding of visual motion and behavior. In turn, such work has enabled us to further ask how higher-level brain areas interpret information from early sensory stages to inform decisions. This dissertation builds on that rich history by incorporating a reverse correlation motion stimulus with explicitly controlled temporal statistics, and taking a decoding approach to groups of simultaneously recorded MT neurons to ask the following questions: (1) Can temporal weighting behavior be flexibly adapted to match stimulus statistics? (2) To what extent is temporal weighting behavior a consequence of dynamic sensory encoding? (3) Can we use manipulations of temporal weighting strategy to demonstrate a causal role of choice-correlated activity in MT? (4) How can decoding groups of MT neurons to predict direction of motion vs. decisions elucidate a relationship between sensory noise and choice-correlated activity? First, I will demonstrate that temporal weighting strategies can be flexibly adapted to match stimulus statistics. Second, I will show that changes in temporal weighting behavior do not manifest as strategy-dependent sensory reweighting of the response in MT. Next, by comparing the output of population decoders trained to predict direction and choice, I will show a fundamental lack of overlap between the two signals that suggests a feedback origin for choice probability (CP). Finally, I will show a consistently late-biased time course of CP despite clear changes in temporal weighting strategy that solidify it is not a signature of a feedforward role for sensory noise.