| 1. |
- Mogensen, Hannes, et al.
(författare)
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Absence of repetetive correlation patterns between pairs of adjacent neocortical neurons in vivo
- 2019
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Ingår i: Frontiers in Neural Circuits. - : Frontiers Media SA. - 1662-5110. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Neuroanatomy suggests that adjacent neocortical neurons share a similar set of afferent synaptic inputs, as opposed to neurons localized to different areas of the neocortex. In the present study, we made simultaneous single-electrode patch clamp recordings from two or three adjacent neurons in the primary somatosensory cortex (S1) of the ketamine-xylazine anesthetized rat in vivo to study the correlation patterns in their spike firing during both spontaneous and sensory-evoked activity. One difference with previous studies of pairwise neuronal spike firing correlations was that here we identified several different quantifiable parameters in the correlation patterns by which different pairs could be compared. The questions asked were if the correlation patterns between adjacent pairs were similar and if there was a relationship between the degree of similarity and the layer location of the pairs. In contrast, our results show that for putative pyramidal neurons within layer III and within layer V, each pair of neurons is to some extent unique in terms of their spiking correlation patterns. Interestingly, our results also indicated that these correlation patterns did not substantially alter between spontaneous and evoked activity. Our findings are compatible with the view that the synaptic input connectivity to each neocortical neuron is at least in some aspects unique. A possible interpretation is that plasticity mechanisms, which could either be initiating or be supported by transcriptomic differences, tend to differentiate rather than harmonize the synaptic weight distributions between adjacent neurons of the same type.
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| 2. |
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| 3. |
- Mogensen, Hannes, et al.
(författare)
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No Medium-Term Spinocerebellar Input Plasticity in Deep Cerebellar Nuclear Neurons In Vivo?
- 2017
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Ingår i: Cerebellum. - : Springer Science and Business Media LLC. - 1473-4222. ; 16:3, s. 638-647
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Tidskriftsartikel (refereegranskat)abstract
- The existence of input plasticity in the deep cerebellar nuclear (DCN) cells of the adult cerebellum could have profound implications for our understanding of cerebellar function. Whereas the existence of plastic changes in mossy fiber (mf) synaptic responses in DCN neurons has been demonstrated in juvenile slices, there has so far been no direct demonstration of this form of plasticity in the adult cerebellum in vivo. In the present paper, we recorded from neurons in the anterior interposed nucleus (AIN) and stimulated the spinocerebellar tracts (SCT) directly or via the skin to obtain mf activation and the inferior olive to activate climbing fibers (cfs) in the nonanesthetized, adult, decerebrated cat. We used three different types of protocols that theoretically could be expected to induce plasticity, each of which involved episodically intense afferent activation lasting for 10 min. These were conjunctive mf-cf activation, which effectively induces plasticity in cortical neurons; mf and cf activation in a pattern resembling the protocol for inducing classical conditioning; and conjunctive activation of two excitatory mf inputs. None of these protocols had any statistically significant effect on the evoked responses in the AIN neurons. We conclude that the input plasticity for excitatory mfs in the AIN cells of the adult cerebellum in vivo is likely to be less effective than that of parallel fiber synaptic inputs in cerebellar cortical cells, at least in the timespan of 1 h.
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| 4. |
- Mogensen, Hannes, et al.
(författare)
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Non-Invasive Ultrasonic Measurement of the Relative Volume Change of the Arterial Wall - First in vivo trial
- 2008
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Ingår i: 2008 IEEE Ultrasonics symposium, vols 1-4 and appendix. - 1051-0117. ; , s. 856-858
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Konferensbidrag (refereegranskat)abstract
- The objective of this study was to show a method that combine non-invasive measurements of the relative diameter change, the radial and the longitudinal strain of the intima-media complex of arterial walls, respectively, to obtain total change in arterial wall volume for a segment of the common carotid artery. The method was evaluated in a limited trial in vivo, comprising five normotensive subjects. Compared to the volume at end-diastole, the average maximum increase in arterial wall volume during each cardiac cycle was 3.2 % (SD 1.8). The aver-age maximum decrease of the arterial wall volume was -5.7 % (SD 3.5). This provides a new way of examining and quantifying the elastic properties of arterial walls.
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| 5. |
- Mogensen, Josefine, et al.
(författare)
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Indenofluorene-Extended Tetrathiafulvalene Scaffolds for Dye-Sensitized Solar Cells
- 2020
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 2020:38, s. 6127-6134
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Tidskriftsartikel (refereegranskat)abstract
- Indenofluorene‐extended tetrathiafulvalenes (IF‐TTFs) comprise a class of π‐conjugated sensitizers that exhibit strong absorptions in the visible region and two reversible one‐electron oxidations. Herein we present the synthesis and optical as well as redox properties of novel IF‐TTF donor‐acceptor scaffolds that were integrated in dye‐sensitized solar cells (DSCs) via anchoring of a carboxylic acid end‐group on the scaffolds to TiO2. Synthetically, the scaffolds were constructed by Sonogashira coupling reactions between an iodo‐functionalized IF‐TTF and an acceptor moeity containing a terminal alkyne. These very first IF‐TTF based candidates for DSCs exhibited high performances, in particular a dye incorporating a benzothiadiazole acceptor moiety, showing a conversion efficiency of 6.4 %. This result signals that IF‐TTF derivatives present a promising class of compounds for further structural modifications. Such modifications will benefit from the readiness of the iodo‐funcitonalized IF‐TTF building block to undergo Pd‐catalyzed coupling reactions.
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| 6. |
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| 7. |
- Norrlid, Johanna, et al.
(författare)
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Multi-structure Cortical States Deduced From Intracellular Representations of Fixed Tactile Input Patterns
- 2021
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Ingår i: Frontiers in Cellular Neuroscience. - : Frontiers Media SA. - 1662-5102.
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Tidskriftsartikel (refereegranskat)abstract
- The brain has a never-ending internal activity, whose spatiotemporal evolution interacts with external inputs to constrain their impact on brain activity and thereby how we perceive them. We used reproducible touch-related spatiotemporal sensory inputs and recorded intracellularly from rat (Sprague-Dawley, male) neocortical neurons to characterize this interaction. The synaptic responses, or the summed input of the networks connected to the neuron, varied greatly to repeated presentations of the same tactile input pattern delivered to the tip of digit 2. Surprisingly, however, these responses tended to sort into a set of specific time-evolving response types, unique for each neuron. Further, using a set of eight such tactile input patterns, we found each neuron to exhibit a set of specific response types for each input provided. Response types were not determined by the global cortical state, but instead likely depended on the time-varying state of the specific subnetworks connected to each neuron. The fact that some types of responses recurred indicates that the cortical network had a non-continuous landscape of solutions for these tactile inputs. Therefore, our data suggest that sensory inputs combine with the internal dynamics of the brain networks, thereby causing them to fall into one of the multiple possible perceptual attractor states. The neuron-specific instantiations of response types we observed suggest that the subnetworks connected to each neuron represent different components of those attractor states. Our results indicate that the impact of cortical internal states on external inputs is substantially more richly resolvable than previously shown.
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| 8. |
- Oddo, Calogero M., et al.
(författare)
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Artificial spatiotemporal touch inputs reveal complementary decoding in neocortical neurons
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Investigations of the mechanisms of touch perception and decoding has been hampered by difficulties in achieving invariant patterns of skin sensor activation. To obtain reproducible spatiotemporal patterns of activation of sensory afferents, we used an artificial fingertip equipped with an array of neuromorphic sensors. The artificial fingertip was used to transduce real-world haptic stimuli into spatiotemporal patterns of spikes. These spike patterns were delivered to the skin afferents of the second digit of rats via an array of stimulation electrodes. Combined with low-noise intra-and extracellular recordings from neocortical neurons in vivo, this approach provided a previously inaccessible high resolution analysis of the representation of tactile information in the neocortical neuronal circuitry. The results indicate high information content in individual neurons and reveal multiple novel neuronal tactile coding features such as heterogeneous and complementary spatiotemporal input selectivity also between neighboring neurons. Such neuronal heterogeneity and complementariness can potentially support a very high decoding capacity in a limited population of neurons. Our results also indicate a potential neuroprosthetic approach to communicate with the brain at a very high resolution and provide a potential novel solution for evaluating the degree or state of neurological disease in animal models.
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| 9. |
- Wahlbom, Anders, et al.
(författare)
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Widely Different Correlation Patterns Between Pairs of Adjacent Thalamic Neurons In vivo
- 2021
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Ingår i: Frontiers in Neural Circuits. - : Frontiers Media SA. - 1662-5110. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- We have previously reported different spike firing correlation patterns among pairs of adjacent pyramidal neurons within the same layer of S1 cortex in vivo, which was argued to suggest that acquired synaptic weight modifications would tend to differentiate adjacent cortical neurons despite them having access to near-identical afferent inputs. Here we made simultaneous single-electrode loose patch-clamp recordings from 14 pairs of adjacent neurons in the lateral thalamus of the ketamine-xylazine anesthetized rat in vivo to study the correlation patterns in their spike firing. As the synapses on thalamic neurons are dominated by a high number of low weight cortical inputs, which would be expected to be shared for two adjacent neurons, and as far as thalamic neurons have homogenous membrane physiology and spike generation, they would be expected to have overall similar spike firing and therefore also correlation patterns. However, we find that across a variety of thalamic nuclei the correlation patterns between pairs of adjacent thalamic neurons vary widely. The findings suggest that the connectivity and cellular physiology of the thalamocortical circuitry, in contrast to what would be expected from a straightforward interpretation of corticothalamic maps and uniform intrinsic cellular neurophysiology, has been shaped by learning to the extent that each pair of thalamic neuron has a unique relationship in their spike firing activity.
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