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5 Janelia Publications

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    Pastalkova Lab
    09/28/16 | Synchronized excitability in a network enables generation of internal neuronal sequences.
    Yingxue W, Roth Z, Pastalkova E
    eLife. 2016 Sep 28;5:. doi: 10.7554/eLife.20697

    Hippocampal place field sequences are supported by sensory cues and network internal mechanisms. In contrast, sharp-wave (SPW) sequences, theta sequences and episode-field sequences are internally generated. The relationship of these sequences to memory is unclear. SPW sequences have been shown to support learning and have been assumed to also support episodic memory. Conversely, we demonstrate these SPW sequences were present even after episodic memory in trained rats was impaired and after other internal sequences - episode-field and theta sequences - were eliminated. SPW sequences did not support memory despite continuing to 'replay' all task-related sequences - place-field and episode-field sequences. Sequence replay occurred selectively during a synchronous increase of population excitability -- SPWs. Similarly, theta sequences depended on the presence of repeated synchronized waves of excitability - theta oscillations. Thus, we suggest that either intermittent or rhythmic synchronized changes of excitability trigger sequential firing of neurons, which in turn supports learning and/or memory.

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    Pastalkova Lab
    11/03/15 | Clique topology reveals intrinsic geometric structure in neural correlations.
    Giusti C, Pastalkova E, Curto C, Itskov V
    Proceedings of the National Academy of Sciences of the United States of America. 2015 Nov 3;112(44):13455-60. doi: 10.1073/pnas.1506407112

    Detecting meaningful structure in neural activity and connectivity data is challenging in the presence of hidden nonlinearities, where traditional eigenvalue-based methods may be misleading. We introduce a novel approach to matrix analysis, called clique topology, that extracts features of the data invariant under nonlinear monotone transformations. These features can be used to detect both random and geometric structure, and depend only on the relative ordering of matrix entries. We then analyzed the activity of pyramidal neurons in rat hippocampus, recorded while the animal was exploring a 2D environment, and confirmed that our method is able to detect geometric organization using only the intrinsic pattern of neural correlations. Remarkably, we found similar results during nonspatial behaviors such as wheel running and rapid eye movement (REM) sleep. This suggests that the geometric structure of correlations is shaped by the underlying hippocampal circuits and is not merely a consequence of position coding. We propose that clique topology is a powerful new tool for matrix analysis in biological settings, where the relationship of observed quantities to more meaningful variables is often nonlinear and unknown.

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    Pastalkova Lab
    07/18/15 | Oscillatory patterns in hippocampus under light and deep isoflurane anesthesia closely mirror prominent brain states in awake animals.
    Lustig B, Wang Y, Pastalkova E
    Hippocampus. 2015 Jul 18;26(1):102-9. doi: 10.1002/hipo.22494

    The hippocampus exhibits a variety of distinct states of activity under different conditions. For instance the rhythmic patterns of activity orchestrated by the theta oscillation during running and REM sleep are markedly different from the large irregular activity (LIA) observed during awake resting and slow wave sleep. We found that under different levels of isoflurane anesthesia activity in the hippocampus of rats displays two distinct states which have several qualities that mirror the theta and LIA states. These data provide further evidence that the two states are intrinsic modes of the hippocampus; while also characterizing a preparation that could be useful for studying the natural activity states in hippocampus. This article is protected by copyright. All rights reserved.

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    02/01/15 | Theta sequences are essential for internally generated hippocampal firing fields.
    Wang Y, Romani S, Lustig B, Leonardo A, Pastalkova E
    Nature Neuroscience. 2015 Feb;18(2):282-8. doi: 10.1038/nn.3904

    Sensory cue inputs and memory-related internal brain activities govern the firing of hippocampal neurons, but which specific firing patterns are induced by either of the two processes remains unclear. We found that sensory cues guided the firing of neurons in rats on a timescale of seconds and supported the formation of spatial firing fields. Independently of the sensory inputs, the memory-related network activity coordinated the firing of neurons not only on a second-long timescale, but also on a millisecond-long timescale, and was dependent on medial septum inputs. We propose a network mechanism that might coordinate this internally generated firing. Overall, we suggest that two independent mechanisms support the formation of spatial firing fields in hippocampus, but only the internally organized system supports short-timescale sequential firing and episodic memory.

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    Pastalkova Lab
    03/01/12 | Implantable blood pressure monitoring cuff for small laboratory animal.
    Pais R, Duttaroy A, Wolever J, Dobbs M, Pastalkova E
    Microsystems for Measurement and Instrumentation (MAMNA), 2012. 2012 Mar:. doi: 10.1109/MAMNA.2012.6195099

    Continuous monitoring of blood pressure in laboratory animals is necessary to understand the effect of treatments for cardiovascular related conditions, such as hypertension. Current methods to measure laboratory rat blood pressure require the animal to be constrained. Our proposed method is a small implantable device which fits around the carotid artery of the rat. Initial data from a mock rat artery setup, with equivalent artery pressure as found in the rat, show that the cuff design effectively detects the pressure change inside the mock artery.

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