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•Cannabis is thought to modulate GABAergic interneuronal signaling in the cortex.•GABAergic networks support cortical gamma oscillations and functional connectivity.•MEG based visual entrainment tasks were used to probe gamma circuit integrity.•Gamma oscillations in early visual cortex remain intact with regular cannabis use.•Higher-order gamma functional connectivity was disrupted in those who use cannabis. Cannabis is a widely-used illicit substance in the United States, and heavy cannabis use has been linked to deficits across multiple cognitive domains. Mechanistically, cannabis affects endocannabinoid receptors densely distributed among GABAergic interneurons throughout the cortex and cerebellum. Such interneuronal networks are known to be crucial in the generation of fast neural gamma-band responses, which support perceptual and cognitive processing and have been frequently implicated in cannabis use. However, studies to date have tended to focus on higher-order processing supported by gamma oscillations, with limited work examining more fundamental aspects of gamma circuit integrity. Herein, 84 adults who regularly use cannabis and 90 demographically-matched nonusers underwent high-density magnetoencephalography during a visual entrainment task involving three gamma-band flicker frequencies (32, 40, and 48 Hz). The resulting data were imaged in the time-frequency domain and the dynamic neural time series were extracted and tested for effects of hemisphere, frequency, and group, and then used to compute whole-brain dynamic functional connectivity. Our results indicated strong gamma entrainment in the bilateral primary visual cortices (V1), with 32 Hz responses being the strongest across both groups (p < .001) and right V1 activity being stronger than left across groups and frequencies (p = .002). Additionally, there were group-by-condition interactions in connectivity maps (p < .005), with the cannabis group having elevated 32 Hz connectivity between V1 and higher-order visual regions relative to controls. These findings suggest that basic gamma circuitry remains intact despite heavy cannabis use, while gamma functional connectivity is preferentially affected and this may lead to the higher-order deficits.

Altered gamma activity is associated with epilepsy. Gamma entrainment using sensory stimuli (GENUS), a non-invasive, exogenous stimulation by rhythmic 40 Hz light flicker, strengthens gamma activity in the primary visual cortex (V1) and suppresses spike generation. Here, we assessed the effect of GENUS on epileptogenesis in male mice with status epilepticus induced by pilocarpine. We found that GENUS immediately increased gamma activity and reduced epileptiform spikes in epileptic mice. After six weeks of GENUS treatment in epileptic mice, significant reductions were observed in neuronal loss and gliosis, brain hyperexcitability was ameliorated, and epilepsy-related behavioral performance was improved. We determined that the increased 40 Hz oscillations and reduced seizure susceptibility induced by GENUS were dependent on the visual circuit associated with ON-OFF direction-selective retinal ganglion cells, glutamatergic neurons in the shell of the dorsal lateral geniculate nucleus, and parvalbumin-expressing fast-spiking interneurons in the superficial 2/3 layer of V1. Whether and how gamma entrainment using sensory stimuli (GENUS) has a role in antiepileptogenesis is not fully understood. Here authors show that GENUS reduces seizure susceptibility in male mice. These effects are mediated via specific visual neural pathway.

Fragile X syndrome (FX) is a leading inherited cause of autism spectrum disorder, characterized by sensory hypersensitivity and impaired visual learning. Visual experience induces synchronized theta oscillations in the primary visual cortex (V1) and lateromedial area (LM), supporting inter-areal sensory binding. Using the Fmr1 knockout (KO) mouse model of FX, we quantify experience-dependent c-Fos expression in V1 and LM via iDISCO whole-brain clearing. Simultaneous in vivo recordings and channelrhodopsin-2-assisted circuit mapping (CRACM) reveal synchronized V1–LM theta oscillations and strengthened feedforward V1 → LM connectivity in wild-type (WT) mice, but attenuated LM oscillations and impaired connectivity in FX mice. Using 4Pi single-molecule localization microscopy, we identify experience-driven dendritic spine remodeling in layer 5 pyramidal cells of V1 and LM in WT mice, which is absent in FX mice. FX mice also show elevated baseline spine density and length. Our findings demonstrate that visual experience drives inter-areal synchronization and synaptic plasticity, which are disrupted in FX. Visual experience synchronizes V1–LM theta oscillations, strengthens V1 → LM connectivity, and drives dendritic spine remodeling in WT mice, the processes disrupted in Fmr1 KO mice, revealing impaired inter-areal binding in Fragile X syndrome.

Background 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. Methods 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. Results 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. Conclusions 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. Graphical abstract

Glucocorticoids reduce phobic fear in patients with anxiety disorders. Previous studies have shown that fear-related activation of the amygdala can be mediated through the visual cortical pathway, which includes the fusiform gyrus, or through other pathways. However, it is not clear which of the pathways that activate the amygdala is responsible for the pathophysiology of a specific phobia and how glucocorticoid treatment alleviates fear processing in these neural networks. We recorded the brain activity with functional magnetic resonance imaging in patients with spider phobia, who received either 20 mg of cortisol or a placebo while viewing pictures of spiders. We also tested healthy participants who did not receive any medication during the same task. We performed dynamic causal modelling (DCM), a connectivity analysis, to examine the effects of cortisol on the networks involved in processing fear and to examine if there was an association between these networks and the symptoms of the phobia. Cortisol administration suppressed the phobic stimuli-related amygdala activity to levels comparable to the healthy participants and reduced subjective phobic fear. The DCM analysis revealed that cortisol administration suppressed the aberrant inputs into the amygdala that did not originate from the visual cortical pathway, but rather from a fast subcortical pathway mediated by the pulvinar nucleus, and suppressed the interactions between the amygdala and fusiform gyrus. This network changes were distinguishable from healthy participants and considered the residual changes under cortisol administration. We also found that the strengths of the aberrant inputs into the amygdala were positively correlated with the severity of spider phobia. This study demonstrates that patients with spider phobia show an aberrant functional connectivity of the amygdala when they are exposed to phobia-related stimuli and that cortisol administration can alleviate this fear-specific neural connectivity.

Amblyopia is a neurodevelopmental disorder of vision caused by abnormal visual experience during early childhood that is often considered to be untreatable in adulthood. Recently, it has been shown that a novel dichoptic videogame-based treatment for amblyopia can improve visual function in adult patients, at least in part, by reducing inhibition of inputs from the amblyopic eye to the visual cortex. Non-invasive anodal transcranial direct current stimulation has been shown to reduce the activity of inhibitory cortical interneurons when applied to the primary motor or visual cortex. In this double-blind, sham-controlled cross-over study we tested the hypothesis that anodal transcranial direct current stimulation of the visual cortex would enhance the therapeutic effects of dichoptic videogame-based treatment. A homogeneous group of 16 young adults (mean age 22.1 ± 1.1 years) with amblyopia were studied to compare the effect of dichoptic treatment alone and dichoptic treatment combined with visual cortex direct current stimulation on measures of binocular (stereopsis) and monocular (visual acuity) visual function. The combined treatment led to greater improvements in stereoacuity than dichoptic treatment alone, indicating that direct current stimulation of the visual cortex boosts the efficacy of dichoptic videogame-based treatment. This intervention warrants further evaluation as a novel therapeutic approach for adults with amblyopia.

As the main cause of visual function deficits in children and adolescents worldwide, amblyopia causes serious impairment of monocular visual acuity and stereopsis. The recovery of visual functions from amblyopia beyond the critical period is slow and incomplete due to the limited plasticity of the mature cortex; notably, visual stimulation training seems to be an effective therapeutic strategy in clinical practice. However, the precise neural basis and cellular mechanisms that underlie amblyopia and visual stimulation treatment remain to be elucidated. Using monocular deprivation in juvenile mice to model amblyopia, we employed two-photon calcium imaging and chemogenetic techniques to investigate the visual responses of individual excitatory neurons and parvalbumin (PV + ) interneurons in the primary visual cortex (V1) of amblyopic mice. We demonstrate that amblyopic mice exhibit an excitation/inhibition (E/I) imbalance. Moreover, visual stimulation decreases the response of PV + interneurons, reactivates the ocular dominance plasticity of excitatory neurons, and promotes vision recovery in adult amblyopic mice. Our results reveal a dynamic E/I balance between excitatory neurons and PV + interneurons that may underlie the neural mechanisms of amblyopia during cortical development and visual stimulation-mediated functional recovery from adult amblyopia, providing evidence for therapeutic applications that rely on reactivating adult cortical plasticity. A dynamic excitation and inhibition (E/I) balance between excitatory neurons and PV+ interneurons in the primary visual cortex underlying the neural mechanisms of amblyopia during cortical development and visual stimulation-mediated functional recovery from adult amblyopia.

Background Cerebral visual impairment (CVI), including perceptual visual dysfunction (PVD), is common in children with cerebral palsy (CP). Inventories of questions relating to practical aspects of visual perception in everyday life, in particular the closed-ended Insight Questions Inventory (IQI), can be used to assess CVI/PVD. Studies linking responses to the inventory with specific visual support strategies, aimed at modifying the child’s environment and/or behaviour to minimize the impact of the CVI/PVD, have been piloted. The IQI and tailored strategies have not been used in an African population, nor have they been tested in a controlled trial. This trial will compare the effectiveness of the IQI and linked visual support strategies versus general supportive treatments on the quality of life of children with CVI/PVD and CP through a randomized controlled trial. Methods/design This is a prospective, double-blind, parallel-arm, randomized controlled trial. The primary outcome is change in quality of life scores between the two arms of the trial at 6 weeks, assessed using the Paediatric Quality of Life Inventory (PedsQL) generic 4.0 and CP 3.0 module. All children will undergo baseline assessment including the Open Questions Inventory, IQI, PedsQL 3.0, PedsQL 4.0 generic, and the Strengths and Difficulties Questionnaire (SDQ). Eligible children with CP aged 4 years to < 16 years will be stratified and blocked by the age groups 4–9 and 10 to < 16 years and by Gross Motor Function Classification System (GMFCS) levels 1–3 and 4–5. Families in the intervention arm will receive tailored insight visual support strategies and telephone calls during the 6-week trial period. The control arm will receive standard treatment and the intervention after the 6-week trial period. Follow-up interviews will be performed in both arms at 6 weeks with a repeat administration of the PedsQL CP 4.0 and 3.0, the IQI and the SDQ. Secondary outcomes include a change in functional vision. Discussion This randomized controlled trial will provide evidence of the effectiveness of this intervention for children with CP in a resource-poor setting. Trial registration Pan African Clinical Trials Registration, PACTR201612001886396 . Registered on 3 December 2016.

Most prior studies on selective attention in the setting of total sleep deprivation (SD) have focused on behavior or activation within fronto-parietal cognitive control areas. Here, we evaluated the effects of SD on the top-down biasing of activation of ventral visual cortex and on functional connectivity between cognitive control and other brain regions. Twenty-three healthy young adult volunteers underwent fMRI after a normal night of sleep (RW) and after sleep deprivation in a counterbalanced manner while performing a selective attention task. During this task, pictures of houses or faces were randomly interleaved among scrambled images. Across different blocks, volunteers responded to house but not face pictures, face but not house pictures, or passively viewed pictures without responding. The appearance of task-relevant pictures was unpredictable in this paradigm. SD resulted in less accurate detection of target pictures without affecting the mean false alarm rate or response time. In addition to a reduction of fronto-parietal activation, attending to houses strongly modulated parahippocampal place area (PPA) activation during RW, but this attention-driven biasing of PPA activation was abolished following SD. Additionally, SD resulted in a significant decrement in functional connectivity between the PPA and two cognitive control areas, the left intraparietal sulcus and the left inferior frontal lobe. SD impairs selective attention as evidenced by reduced selectivity in PPA activation. Further, reduction in fronto-parietal and ventral visual task-related activation suggests that it also affects sustained attention. Reductions in functional connectivity may be an important additional imaging parameter to consider in characterizing the effects of sleep deprivation on cognition.

Deviation of the direction of two eyes (strabismus) or chronic optical blur (anisometropia) separately and together can disrupt the development of visual cortex. To shed new light on how these two forms of visual deprivation affect cortical development, we used event-related potentials coupled with a stimulation paradigm to study the temporal evolution of visual responses in patients who had experienced either strabismus or anisometropia early in life. Our results indicate that strabismus generates significant abnormalities at both early and later stages of cortical processing and, importantly, that these abnormalities are independent of visual-acuity deficits. The nonamblyopic eyes of anisometropic amblyopes, by contrast, are normal, suggesting that these two forms of visual deprivation are differentiated very early in visual cortex. Visual development depends on sensory input during an early developmental critical period. Deviation of the pointing direction of the two eyes (strabismus) or chronic optical blur (anisometropia) separately and together can disrupt the formation of normal binocular interactions and the development of spatial processing, leading to a loss of stereopsis and visual acuity known as amblyopia. To shed new light on how these two different forms of visual deprivation affect the development of visual cortex, we used event-related potentials (ERPs) to study the temporal evolution of visual responses in patients who had experienced either strabismus or anisometropia early in life. To make a specific statement about the locus of deprivation effects, we took advantage of a stimulation paradigm in which we could measure deprivation effects that arise either before or after a configuration-specific response to illusory contours (ICs). Extraction of ICs is known to first occur in extrastriate visual areas. Our ERP measurements indicate that deprivation via strabismus affects both the early part of the evoked response that occurs before ICs are formed as well as the later IC-selective response. Importantly, these effects are found in the normal-acuity nonamblyopic eyes of strabismic amblyopes and in both eyes of strabismic patients without amblyopia. The nonamblyopic eyes of anisometropic amblyopes, by contrast, are normal. Our results indicate that beyond the well-known effects of strabismus on the development of normal binocularity, it also affects the early stages of monocular feature processing in an acuity-independent fashion.