Removal or component reversal of local geomagnetic field affects foraging orientation preference in migratory insect brown planthopper Nilaparvata lugens

Background Migratory brown planthopper Nilaparvata lugens (N. lugens) annually migrates to Northeast Asia in spring and returns to Southeast Asia in autumn. However, mechanisms for orientation and navigation during their flight remain largely unknown. The geomagnetic field (GMF) is an important source of directional information for animals (including N. lugens), yet the magnetic compass involved has not been fully identified. Methods Here we assessed the influences of GMF on the foraging orientation preference of N. lugens by removing or component reversal of local GMF. At the same time, we examined the role of iron-sulfur cluster assembly1 (IscA1), a putative component of magnetoreceptor, in the foraging orientation preference of N. lugens under the controlled magnetic fields by RNA silencing (RNAi). Results We found that the near-zero magnetic field (NZMF) or vertical reversal of GMF could lead to N. lugens losing the foraging orientation preference, suggesting that a normal level of GMF, in the way of either intensity or inclination, was essential for the foraging orientation of N. lugens. Moreover, the gene knockdown of IscA1, also affected the foraging orientation preference of N. lugens, pointing out a potential role of IscA1 in the insects’ sensing of variation in the GMF. Discussion These results suggested a foraging orientation preference is associated with the GMF and revealed new insights into the relationship between the IscA1 and magnetosensitivity mechanism in N. lugens.

Horizontal connectivity in V1 : Prediction of coherence in contour and motion integration

This study demonstrates the functional importance of the Surround context relayed laterally in V1 by the horizontal connectivity, in controlling the latency and the gain of the cortical response to the feedforward visual drive. We report here four main findings : 1) a centripetal apparent motion sequence results in a shortening of the spiking latency of V1 cells, when the orientation of the local inducer and the global motion axis are both co-aligned with the RF orientation preference; 2) this contextual effects grows with visual flow speed, peaking at 150-250 degrees per second until matching the propagation speed of horizontal connectivity (0.15-0.25 mm/ms); 3) For this speed range, axial sensitivity of V1 cells is tilted by 90 degrees to become co-aligned with the orientation preference axis; 4) the modulation strength by the surround context correlates with the spatiotemporal coherence of the apparent motion flow. Our results suggest an internally-generated binding process, linking local (orientation /position) and global (motion/direction) features as early as V1. This long-range diffusion process constitutes a plausible substrate in V1 of the human psychophysical bias in speed estimate for collinear motion. Since demonstrated in the anesthetized cat, this novel form of contextual control of the cortical transfer function is a built-in property in V1, whose expression does not require behavioral attention and top-down control from higher cortical areas. We propose that horizontal connectivity participates to the propagation of an internal prediction wave, linking contour co-alignment and global axial motion at an apparent speed in the range of saccadic-like eye-movements.

Modeling the role of gap junctions between excitatory neurons in the developing visual cortex

Recent experiments in the developing mammalian visual cortex have revealed that gap junctions couple excitatory cells and potentially influence the formation of chemical synapses. In particular, cells that were coupled by a gap junction during development tend to share an orientation preference and are preferentially coupled by a chemical synapse in the adult cortex, a property that is diminished when gap junctions are blocked. In this work, we construct a simplified model of the developing mouse visual cortex including spike-timing-dependent plasticity of both the feedforward synaptic inputs and recurrent cortical synapses. We use this model to show that synchrony among gap-junction-coupled cells underlies their preference to form strong recurrent synapses and develop similar orientation preference; this effect decreases with an increase in coupling density. Additionally, we demonstrate that gap-junction coupling works, together with the relative timing of synaptic development of the feedforward and recurrent synapses, to determine the resulting cortical map of orientation preference.

Long-range neural coherence encodes stimulus information in primate visual cortex

In the primary visual cortex, neurons with similar receptive field properties are bound together through widespread networks of horizontal connections that span orientation columns. How connectivity across the cortical surface relates to stimulus information is not fully understood. We recorded spiking activity and the local field potential (LFP) from the primary visual cortex of marmoset monkeys and examined how connectivity between distant orientation columns affect the encoding of visual orientation.Regardless of their spatial separation, recording sites with similar orientation preferences have higher coherence between spiking activity and the local field potential than sites with different preferred orientation. Using information theoretic methods, we measured the amount of stimulus information that is shared between pairs of sites. More stimulus information can be decoded from pairs with the same preferred stimulus orientation than the pairs with a different preferred orientation, and the amount of information is significantly correlated with the magnitude of beta-band spike-LFP coherence. These effects remained after controlling for firing rate differences.Our results thus show that spike-LFP synchronization in the beta-band is associated with the encoding of stimulus information within the primary visual cortex of marmoset monkeys.Significance StatementA fundamental step in processing images in the visual cortex is coordinating the neural activity across distributed populations of neurons. Here, we demonstrate that populations of neurons in the primary visual cortex of marmoset monkeys with the same stimulus orientation preference temporally coordinate their activity patterns when presented with a visual stimulus. We find maximum synchronization in the beta range depends on the similarity of orientation preference at each pair of the neural population.

Idealized model of the developing visual cortex

Recent experiments in the developing mammalian visual cortex have revealed that gap junctions couple excitatory cells and potentially influence the formation of chemical synapses. Though gap junctions between inhibitory cells are ubiquitous in the adult cortex, and their presence has been shown to promote synchronous network firing, their function among excitatory, pyramidal cells remains poorly understood. During development, pyramidal cells that were derived from the same progenitor cell, called sister cells, are preferentially connected by a gap junction during the first postnatal week, while chemical synapses are still being formed. Additionally, these sister cells tend to share an orientation preference and a chemical synapse in the adult cortex, a property that is diminished when gap junctions are blocked. In this work, we construct an idealized model of the mouse visual cortex during the first two postnatal weeks of development to analyze the response properties of gap-junction-coupled cells and their effect on synaptic plasticity. Further, as an application of this model, we investigate the interplay of gap-junction coupling and synaptic plasticity on the order, or organization, of the resulting cortical map of orientation preference.Author summaryGap junctions, or sites of direct electrical connections between neurons, have a significant presence in the cortex, both during development and in adulthood. Their primary function during either of these periods, however, is still poorly understood. In the adult cortex, gap junctions between local, inhibitory neurons have been shown to promote synchronous firing, a network characteristic thought to be important for learning, attention, and memory. During development, gap junctions between excitatory, pyramidal cells, have been conjectured to play a role in synaptic plasticity and the formation of cortical circuits. In the visual cortex, where neurons exhibit tuned responses to properties of visual input such as orientation and direction, recent experiments show that excitatory cells are coupled by gap junctions during the first postnatal week and are replaced by chemical synapses during the second week. In this work, we explore the possible contribution of gap-junction coupling during development to the formation of chemical synapses both into the visual cortex from the thalamus and within the visual cortex between cortical cells. Specifically, within a mathematical model of the visual cortex during development, we identify the response properties of gap-junction-coupled cells and their influence on the formation of the cortical map of orientation preference.

Tightly Compacted Perovskite Laminates on Flexible Substrates via Hot-Pressing

Pressure and temperature are powerful tools applied to perovskites to achieve recrystallization. Lamination, based on recrystallization of perovskites, avoids the limitations and improves the compatibility of materials and solvents in perovskite device architectures. In this work, we demonstrate tightly compacted perovskite laminates on flexible substrates via hot-pressing and investigate the effect of hot-pressing conditions on the lamination qualities and optical properties of perovskite laminates. The optimized laminates achieved at a temperature of 90 °C and a pressure of 10 MPa could sustain a horizontal pulling pressure of 636 kPa and a vertical pulling pressure of 71 kPa. Perovskite laminates exhibit increased crystallinity and a crystallization orientation preference to the (100) direction. The optical properties of laminated perovskites are almost identical to those of pristine perovskites, and the photoluminescence quantum yield (PLQY) survives the negative impact of thermal degradation. This work demonstrates a promising approach to physically laminating perovskite films, which may accelerate the development of roll-to-roll printed perovskite devices and perovskite tandem architectures in the future.

Relation between gamma oscillations and neuronal plasticity in the visual cortex

Use-dependent long-term changes of neuronal response properties must be gated to prevent irrelevant activity from inducing inappropriate modifications. Here we test the hypothesis that local network dynamics contribute to such gating. As synaptic modifications depend on temporal contiguity between presynaptic and postsynaptic activity, we examined the effect of synchronized gamma (ɣ) oscillations on stimulation-dependent modifications of orientation selectivity in adult cat visual cortex. Changes of orientation maps were induced by pairing visual stimulation with electrical activation of the mesencephalic reticular formation. Changes in orientation selectivity were assessed with optical recording of intrinsic signals and multiunit recordings. When conditioning stimuli were associated with strong ɣ-oscillations, orientation domains matching the orientation of the conditioning grating stimulus became more responsive and expanded, because neurons with preferences differing by less than 30° from the orientation of the conditioning grating shifted their orientation preference toward the conditioned orientation. When conditioning stimuli induced no or only weak ɣ-oscillations, responsiveness of neurons driven by the conditioning stimulus decreased. These differential effects depended on the power of oscillations in the low ɣ-band (20 Hz to 48 Hz) and not on differences in discharge rate of cortical neurons, because there was no correlation between the discharge rates during conditioning and the occurrence of changes in orientation preference. Thus, occurrence and polarity of use-dependent long-term changes of cortical response properties appear to depend on the occurrence of ɣ-oscillations during induction and hence on the degree of temporal coherence of the change-inducing network activity.