Decoding in the dark: extracting information from spontaneous activity in primary visual cortex

In studies of the developing mammalian visual system, it has been axiomatic that visual experience begins with eye-opening. Any role for neuronal activity earlier in development has been attributed to the patterned spontaneous activity found in retina and lateral geniculate nucleus (LGN). Here we show that, as early as 2 wk before eye-opening, visual stimuli presented through the closed eyelids can drive neuronal activity in LGN and striate cortex of the ferret. At this age, spontaneous activity in cortex is much lower than in LGN, and the visual responses of many cortical, but not geniculate, neurons depend on the orientation of a moving grating. Furthermore the selectivity of cortical neurons to the orientation of gratings presented through the closed eyelids improves with age. Thus neuronal activity patterned by visual experience, rather than by spontaneous retinal activity, is present in visual cortex much earlier than previously thought. This could have important implications for the self-organization of visual cortex.

In this study, the acute effect of 3-nitropropionic acid was investigated on open field and startle behavior of rats, and on their cortical electrical activity. Spontaneous locomotor activity, acoustic startle response, and pre-pulse inhibition of acoustic startle were measured in male Wistar rats (10 weeks old, 180-200 g body weight) after a single dose of 10 or 20 mg/kg i.p. 3-nitropropionic acid. After the behavioral tests, the rats were anaesthetized, and spontaneous cortical electrical activity was recorded. The vertical, horizontal and local open field performance showed dose-dependent deterioration in the rats treated with 3-nitropropionic acid. The number of "noise-positive" startle responses showed non-significant changes, but the inhibition by pre-pulse was significantly reduced in the high dose animals. High dose also increased the proportion of low-frequencies in the cortical activity. 3-nitropropionic acid, known primarily to act in repeated doses (e.g., in animal models of Huntington's disease) had also some clear-cut acute effects on behavioral and electrophysiological parameters of the treated rats.

Epipial application is one of the approaches for drug delivery into the cortex. However, passive diffusion of epipially applied drugs through the cortical depth may be slow, and different drug concentrations may be achieved at different rates across the cortical depth. Here, we explored the pharmacodynamics of the inhibitory effects of epipially applied ionotropic glutamate receptor antagonists CNQX and dAPV on sensory-evoked and spontaneous activity across layers of the cortical barrel column in urethane-anesthetized rats. The inhibitory effects of CNQX and dAPV were observed at concentrations that were an order higher than in slices in vitro, and they slowly developed from the cortical surface to depth after epipial application. The level of the inhibitory effects also followed the surface-to-depth gradient, with full inhibition of sensory evoked potentials (SEPs) in the supragranular layers and L4 and only partial inhibition in L5 and L6. During epipial CNQX and dAPV application, spontaneous activity and the late component of multiple unit activity (MUA) during sensory-evoked responses were suppressed faster than the short-latency MUA component. Despite complete suppression of SEPs in L4, sensory-evoked short-latency multiunit responses in L4 persisted, and they were suppressed by further addition of lidocaine suggesting that spikes in thalamocortical axons contribute ∼20% to early multiunit responses. Epipial CNQX and dAPV also completely suppressed sensory-evoked very fast (∼500 Hz) oscillations and spontaneous slow wave activity in L2/3 and L4. However, delta oscillations persisted in L5/6. Thus, CNQX and dAPV exert inhibitory actions on cortical activity during epipial application at much higher concentrations than in vitro, and the pharmacodynamics of their inhibitory effects is characterized by the surface-to-depth gradients in the rate of development and the level of inhibition of sensory-evoked and spontaneous cortical activity.

Cerebral palsy is the most common paediatric neurological disorder and results in extensive impairment to the sensorimotor system. However, these individuals also experience increased pain perception, resulting in decreased quality of life. In the present study, we utilized magnetoencephalographic brain imaging to examine whether alterations in spontaneous neural activity predict the level of pain experienced in a cohort of 38 individuals with spastic diplegic cerebral palsy and 67 neurotypical controls. Participants completed 5 min of an eyes closed resting-state paradigm while undergoing a magnetoencephalography recording. The magnetoencephalographic data were then source imaged, and the power within the delta (2–4 Hz), theta (5–7 Hz), alpha (8–12 Hz), beta (15–29 Hz), low gamma (30–59 Hz) and high gamma (60–90 Hz) frequency bands were computed. The resulting power spectral density maps were analysed vertex-wise to identify differences in spontaneous activity between groups. Our findings indicated that spontaneous cortical activity was altered in the participants with cerebral palsy in the delta, alpha, beta, low gamma and high gamma bands across the occipital, frontal and secondary somatosensory cortical areas (all pFWE < 0.05). Furthermore, we also found that the altered beta band spontaneous activity in the secondary somatosensory cortices predicted heightened pain perception in the individuals with cerebral palsy (P = 0.039). Overall, these results demonstrate that spontaneous cortical activity within individuals with cerebral palsy is altered in comparison to their neurotypical peers and may predict increased pain perception in this patient population. Potentially, changes in spontaneous resting-state activity may be utilized to measure the effectiveness of current treatment approaches that are directed at reducing the pain experienced by individuals with cerebral palsy.

Migraine attacks are believed to originate in the brain, but the exact mechanisms by which the brain generates peripheral nociceptive signals that drive migraine pain remain unclear. Sensory cortex hyperexcitability has been observed consistently across different migraine subtypes. Astrocytes detect aberrant increases in cortical activity via their Gq-coupled receptors and respond by releasing gliotransmitters and other factors with proinflammatory and nociceptive properties. In the present study, we used a rat model to investigate whether heightened cortical astrocyte Gq-coupled signaling is sufficient to drive peripheral trigeminal meningeal nociceptive responses linked to the generation of migraine headaches. We used an AAV-based chemogenetic approach that allows selective activation of cortical astrocyte Gq-GPCR signaling. We targeted astrocytes in the visual cortex as hyperexcitability in this region has been implicated in migraine. Furthermore, the meninges overlying the visual cortex are densely innervated by nociceptive fibers. We combined this chemogenetic approach with in vivo single-unit recording of meningeal nociceptors to assess changes in their ongoing activity and mechanosensitivity, along with testing of migraine-like behaviors. We further targeted calcitonin gene-related peptide (CGRP), using a monoclonal antibody (anti-CGRP mAb), to assess the relevance of cortical astrocyte activation to migraine. We discovered that heightened activation of Gq-coupled signaling in visual cortex astrocytes drives persistent discharge and increased mechanosensitivity of meningeal nociceptors. Cortical astrocytic activation also generated cephalic mechanical pain hypersensitivity, reduced exploratory behavior, and anxiety-like behaviors linked to migraine headaches. Blocking calcitonin gene-related peptide signaling suppressed astrocyte-mediated increases in meningeal nociceptor discharge and alleviated associated migraine-related behaviors. Our findings reveal a previously unappreciated role for augmented visual cortex astrocyte signaling as a triggering factor sufficient to generate meningeal nociception and migraine pain and greatly expand our understanding of migraine pathophysiology.

Similar to primates, visual cortex in rodents appears to be organized in two distinct hierarchical streams. However, there is still little known about how visual information is processed along those streams in rodents. In this study, we examined how repetition suppression and position and clutter tolerance of the neuronal representations evolve along the putative ventral visual stream in rats. To address this question, we recorded multiunit spiking activity in primary visual cortex (V1) and the more downstream visual laterointermediate (LI) area of head-restrained Long-Evans rats. We employed a paradigm reminiscent of the continuous carry-over design used in human neuroimaging. In both areas, stimulus repetition attenuated the early phase of the neuronal response to the repeated stimulus, with this response suppression being greater in area LI. Furthermore, stimulus preferences were more similar across positions (position tolerance) in area LI than in V1, even though the absolute responses in both areas were very sensitive to changes in position. In contrast, the neuronal representations in both areas were equally good at tolerating the presence of limited visual clutter, as modeled by the presentation of a single flank stimulus. When probing tolerance of the neuronal representations with stimulus-specific adaptation, we detected no position tolerance in either examined brain area, whereas, on the contrary, we revealed clutter tolerance in both areas. Overall, our data demonstrate similarities and discrepancies in processing of visual information along the ventral visual stream of rodents and primates. Moreover, our results stress caution in using neuronal adaptation to probe tolerance of the neuronal representations. NEW & NOTEWORTHY Rodents are emerging as a popular animal model that complement primates for studying higher level visual functions. Similar to findings in primates, we demonstrate a greater repetition suppression and position tolerance of the neuronal representations in the downstream laterointermediate area of Long-Evans rats compared with primary visual cortex. However, we report no difference in the degree of clutter tolerance between the areas. These findings provide additional evidence for hierarchical processing of visual stimuli in rodents.

A major topic of investigation in the field of developmental neuroscience is to understand how newly formed excitatory synapses receive and transmit information. It is now widely accepted that neural activity plays an important role in a number of developmental processes, including the refinement and establishment of orderly connections (Grubb and Thompson 2004). However, it remains unclear how many immature excitatory synapses (i.e., ones that utilize glutamate as a neurotransmitter) participate in the relay of activity. Contributing to this problem is the finding that immature glutamatergic synapses are comprised largely of N-methyl-D-aspartate (NMDA) receptors and lack AMPA receptors that mediate fast excitatory transmission. Such synapses are said to be “silent,” incapable of causing postsynaptic action potentials from resting levels because in addition to glutamate, the NMDA receptor requires membrane depolarization to relieve a voltage-dependent Mg 2 block. How then do silent synapses “speak” loudly enough to cause postsynaptic firing and thereby successfully relay information? In a recent article, Liu and Chen (2008) provide some answers to this question. They examine the synaptic responses and intrinsic properties of developing neurons by making use of an in vitro thalamic slice preparation that maintains the excitatory synaptic connections between retinal ganglion cells and relay cells of the dorsal lateral geniculate nucleus (LGN). In an elegant series of whole cell recording experiments, they show how a constellation of properties, including ligand-gated channel kinetics, receptor subunit composition, extended presence of neurotransmitter

Event Abstract Back to Event A single cell with active conductance's can learn timing and multi-stability Recent experimental studies have demonstrated that neural responses in primary sensory cortex can significantly outlast the duration of the sensory input. In particular, a recent study by Shuler and Bear (2006) has shown learned, reward timing dependent cortical activity in primary visual cortex, activity that represents the expected duration of a reward. We have shown how such activity can be represented and learned in a network of interacting neurons (paper submitted). However, recent experimental results and computational models (Egorov et al. 2002, Fransen et al. 2002, 2006) have shown that single neurons with active conductance-s can account for persistent activity, suggesting that they might also contribute to the prolonged decaying activity observed in primary sensory cortex. Here, we first develop a simple model of a neuron with active conductance-s which can in principle account for bi-stability, multi-stability and slowly decaying activity. This model is based on voltage dependent calcium channels, and on calcium dependent cationic channels, a model inspired by the previous experiments and computational studies. In contrast to previous computational model this is a reduced single compartment model, which makes it more amenable to analysis, while still maintaining a biophysical basis. Using simulations we show that this model, with parameters chosen correctly, can exhibit bi-stability critically slowed neuronal dynamics as well as multi-stability. Using an analytical pseudo steady-state approach we reduce this model to a single non-linear dynamical equation, and we show that the reduced model is in very close agreement with the full simulated model. Using the reduced model we develop single parameter bifurcation diagrams of the model, and we show that it is robustly bi-stable. The reduced model can account both for the phase transitions and for the detailed dynamics in the falling phase of the sub-threshold regime. The reduced model also makes it possible to intuitively understand the origin of bi-stability, multi-stability as well as critically slow dynamics. Next we introduce a reinforcement based plasticity rule for the internal conductance-s which critically control the neuronal dynamics. We demonstrate that this learning rule can learn appropriate reward times, and when these reward times are learned it produces neuronal dynamics that are similar to those observed experimentally. We also show that the same learning rule, when applied at a different parameter regime can learn a target firing rate for the “up” state in a bi-stable system. Unlike our previous stochastic spiking model, this single cell model is deterministic and produces periodic firing in the up state. This stand in contrast to in-vivo experimental results in which the CV is typically ?1 (Barbieri and Brunel, 2008). However, these active conductance-s, when combined with the cortical stochastic background activity might contribute to coding and learning of representations of time and of persistent activity levels. Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: (2009). A single cell with active conductance's can learn timing and multi-stability. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.254 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 03 Feb 2009; Published Online: 03 Feb 2009. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Migraine episodes are known to induce heightened photosensitivity. Neuroimaging investigations have revealed that the primary visual cortex exhibits abnormal activation patterns both during and between migraine attacks. Growing evidence suggests that altered cortical activity patterns may underlie the pathophysiology of neurological disorders. This study explored whether and how chronic migraine affects cortical activity patterns at single-cell resolution in the primary visual cortex during its progression. Longitudinal in vivo two-photon calcium imaging was performed in the primary visual cortex of a chronic migraine mouse model across multiple time points. Cortical circuit activity patterns and behavioral correlates were assessed through combined chemogenetic manipulation and pharmacological interventions, with a particular focus on primary visual cortex functional modulation. Following chronic migraine induction, spontaneous hyperactivation emerged in cortical activity patterns within the primary visual cortex. Layer II/III neurons appeared as major contributors to this neural dysregulation, with layer V neurons showing less pronounced involvement. Prophylactic topiramate treatment attenuated allodynia and light aversion behaviors while reducing pathological cortical hyperactivity. Chemogenetic inhibition of primary visual cortex layer II/III neurons ameliorated light aversion without attenuating pain sensitization, while modulating aberrant spontaneous cortical activity patterns. These findings provide preliminary evidence for dynamic alterations in spontaneous cortical neural signatures within the primary visual cortex throughout chronic migraine progression. Modulation of these neural adaptations appears to show the potential to alleviate associated light sensitivity, providing insight into potential pathophysiological mechanisms underlying light sensitivity in chronic migraine.

Whether or not activity in the primary visual cortex (V1) is directly related to the visibility of a stimulus is a long-standing debate. To investigate the basis of existing discrepancies in the literature, we measured the BOLD response, along with laminar electrophysiological signals, in area V1 of two behaving monkeys, and correlated responses there with the perceived visibility of a salient stimulus. We show that stimulus visibility can be reliably derived from the fMRI signal, but not from neuronal spiking activity. We further demonstrate by laminar sampling of V1 local field potentials (LFP) that there is an uneven distribution of percept-related current changes between the different cortical laminae. Thus, we show that fMRI and neurophysiological signals, while generally in good agreement, become uncoupled during perceptual suppression. Furthermore, our data reveals that if a visual stimulus goes unperceived, there is a drop in the membrane currents in the upper layers of V1.

Attention-dependent reduction in the tendency for neurons to fire bursts (burstiness) is widely observed in the visual cortex. However, the underlying mechanism and the functional role of this phenomenon remain unclear. We recorded well-isolated single-unit activities in primary visual cortex (V1) from two primates (Macaca mulatta) while they performed a detection task engaging spatial attention with two levels of difficulty (hard/easy). We found that attention modulated burstiness of V1 neurons in a cell-type specific manner. For neurons whose net response enhanced with the increase of task difficulty (difficulty-enhanced neuron), representing their involvement in boosting the signal of the attended stimulus, attention led to a reduction in burstiness during hard task but not during easy task. In contrast, regardless of the level of task difficulty, attention-dependent reduction in burstiness was not observed in neurons that showed a net suppression in firing rate with the increase of task difficulty (difficulty-suppressed neuron), indicating their commitment in filtering out the interference of distractor. This differentiation in the effects of attentional modulation on burstiness among the cells with distinct functional roles in attention suggests that the reduction in burstiness by attention is linked to target enhancement and is not associated with distractor suppression.

Movement-related slow cortical magnetic fields and changes of spontaneous MEG- and EEG-brain rhythms

Development of cortical neuronal activity in the neonatal cat

The ability to process visual stimuli rich with motion represents an essential skill for animal survival and is largely already present at the onset of vision. Although the exact mechanisms underlying its maturation remain elusive, spontaneous activity patterns in the retina, known as retinal waves, have been shown to contribute to this developmental process. Retinal waves exhibit complex spatio-temporal statistics and contribute to the establishment of circuit connectivity and function in the visual system, including the formation of retinotopic maps and the refinement of receptive fields in downstream areas such as the thalamus and visual cortex. Recent work in mice has shown that retinal waves have statistical features matching those of natural visual stimuli, such as optic flow, suggesting that they could prime the visual system for motion processing upon vision onset. Motivated by these findings, we examined whether artificial neural network (ANN) models trained on natural movies show improved performance if pre-trained with retinal waves. We employed the spatio-temporally complex task of next-frame prediction, in which the ANN was trained to predict the next frame based on preceding input frames of a movie. We found that pre-training ANNs with retinal waves enhances the processing of real-world visual stimuli and accelerates learning. Strikingly, when we merely replaced the initial training epochs on naturalistic stimuli with retinal waves, keeping the total training time the same, we still found that an ANN trained on retinal waves temporarily outperforms one trained solely on natural movies. Similar to observations made in biological systems, we also found that pre-training with spontaneous activity refines the receptive field of ANN neurons. Overall, our work sheds light on the functional role of spatio-temporally patterned spontaneous activity in the processing of motion in natural scenes, suggesting it acts as a training signal to prepare the developing visual system for adult visual processing.

It has been reported that histamine appears to act as a neurotransmitter in the mammalian brain (Schwartz, 1975). In 1954, Feldberg and Sherwood demonstrated that intracerebroventricular (i.c.v.) injection of histamine (200 μg) elicited a decrease in spontaneous activity and sleepiness in cats. In mice and rats, it was also found that high doses of histamine (i.c. v., 20–100 μg) produced sedation, ptosis and drowsy patterns in spontaneous EEGs characterized by high amplitude and low frequency EEG waves (Kamei et al., 1981). Moreover, i.c.v. injection of histamine (at doses of μg or more) elicited an inhibition of the pinna reflex (Kamei et al., 1984) as well as a prolongation of thiopental sleeping time in mice (Kamei et al., 1986). These findings seem to suggest that high doses of histamine exerts an inhibitory influence on the central nervous system (CNS). By contrast, Monnier et al. (1970, 1977) reported that intravenous (i.v.) and i.c.v. injection of histamine induced an EEG arousal response characterized by decreased delta activity in the cerebral cortex. It has also been shown that histamine (250 ng) induced a significant increase in spontaneous motor activity in the conscious rat, including increased grooming and exploratory behavior, indicating that histamine may be involved in modulating behavioral arousal (Kalivas, 1982). In accordance with this view, H1 antagonists have caused drowsy patterns in spontaneous EEGs and sedative effects in humans (Carruthers et al., 1978) and experimental animals (Heinrich, 1953; Tasaka et al., 1986)