Primary visual cortex

At eye-opening, layer 2/3 (L2/3) of ferret primary visual cortex (V1) exhibits orientation-selective responses, modular (~periodic) patterns of visually-evoked and spontaneous activity, and spatially periodic orientation maps. L4 activity has weaker orientation selectivity (OS) than, and is spatially uncorrelated with, L2/3 responses at eye-opening, suggesting L2/3 may generate modular activity patterns independently of L4 map or activity organization. Here we characterize L4 and L2/3 receptive fields (RFs) and the L4 orientation map at eye-opening. We then model the connectivity by which L4 i

Factorization of visual scenes refers to disentangling explanatory variables such that they are represented explicitly. For example, to act in the world, animals must continually distinguish between object form and motion. We propose a model of primary visual cortex (V1) consisting of complex cell-like units. Each unit has two sub-units and corresponding receptive fields (RFs), and factorizes its amplitude and phase response through a recurrent inference procedure. The model also learns localized, oriented, and band-pass RFs from natural images, and exhibits signature V1 complex cell phase inv

Within the broad theme of brain plasticity, this work explores a dimension that has not received as much research attention thus far - activity dependent changes in myelin. Myelin acts to speed up axonal conduction. Until recently, the dogma of the field was that myelination was part of a developmental program that set up the neural circuitry, after which it remained static; however, the past decade of research has begun to reveal that myelin plasticity continues well into adulthood, is modulated in an activity dependent manner, and contributes to skill learning. The first part of our study is

…test how neural activity in the mouse primary visual cortex (V1) is read out to detect visual stimuli. Both an unweighted mean readout or a weighted read out of visually sensitive neurons could support detection, but the weighted rea

The mammalian Prefrontal Cortex (PFC) has been suggested to modulate sensory information processing across multiple cortical regions via long-range axonal projections. These axonal projections arise from discrete PFC subregions with unique brain-wide connectivity and functional repertoires, which may provide the architecture for modular feedback intended to shape sensory processing. Here, we used axonal tracing, axonal and somatic 2-photon calcium imaging, and chemogenetic manipulations in mice to delineate how projections from the Anterior Cingulate Cortex (ACA) and ventrolateral Orbitofronta

…of population activity in the sensory cortex. And second, that this relation differs from the one between sensory activity and perceptual decisions. To this end, we studied neural population activity in the primary visual cortex of macaque monkeys performing a task that reveals the animal's subjective sense of perceptual confidence. Specifical

…efficient and precise processing of visual information, consisting of multiple features continuously in flux. Visual perception arises from signals propagating through parallel neuronal pathways wiring the retina to both cortical (primary visual cortex, V1; higher visual areas, HVAs) and subcortical structures (thalamus; superior colliculus, SC), each with distinct functional properties and cellular compositions. However, the precise distribution of behaviorally relevant visual signals across these pathways remains unclear, a

…Recent experiments in the mouse primary visual cortex (V1) have shown a remarkable finding: the magnitude of population responses follows a power law with respect to stimulus frequency. This power law is universal, with the same exponent observed across different statistical environments, enabling predictions of population responses to new environments and allowing the brai

The primary visual cortex (V1) directly projects to the superior colliculus (SC) and is believed to provide sensory drive for eye movements. Consistent with this, a majority of saccade-related SC neurons also exhibit short-latency, stimulus-driven visual responses, which are additionally feature-tuned. However, direct neurophysiological comparisons of the visual response properties of the two anatomically-connected brain areas are surprisingly lacking, especially with respect to active looking behaviors. I will describe a series of experiments characterizing visual response properties in prima

A fundamental property of neurons in the primary visual cortex is their preference for orientation of edges. It was shown that this orientation tuning is mostly invariant under contrast changes [1], a property that is not explained by a simple feed-forward scheme [2, 3]. We designed a synthetic hybrid neural circuit to study the emergence of orientation selectivity under different thalamo-cortical connections. To this end, a computational model of the retino-thalamic pathway was combined with an in-vitro model of cortical input layer 4. The latter was either a primary culture of cortical neur

The role of feedback in sensory systems remains a major puzzle in neuroscience. Classical computational theories such as hierarchical predictive coding[1] or hierarchical Bayesian inference[2] postulate abstract normative goals for the role of feedback connections. However, predictions derived from these theories are typically specified at the level of individual neurons. Whether feedback shapes collective properties of neural populations and how such changes may impact encoding of sensory signals remain unknown. Here we tackle these questions directly by studying the population coding of na

…In layer 2/3 of mouse primary visual cortex (V1) specifically, populations of pyramidal and vasoactive-intestinal-peptide-expressing (VIP) cells show pronounced responses to novel visual stimuli (novelty responses) and weaker responses to familiar ones. Although experimental and the

…In primary visual cortex (V1), spontaneous activity originates from two sources, from the retina relayed by thalamus and intrinsically generated in the cortex. Spontaneous events from these two sources have different spatiotemporal properties:

…State-dependent changes in the primary visual cortex (V1) are potentially induced by cortico-cortical signals, such as those from V4 to V1, known to mediate visual attention in macaques [5]. However, relationships between such top-down signals and the aforementioned state-dependent changes have not been demonstrated directly. To investig

…the mice were engaged in an implicit visual learning task. Following the Bayesian learning principles, wild-type mice showed contextual modulation of the visual responses in the superior colliculus and pupil dynamics, but not in the retinal signals. In contrast, Scn2a-haploinsufficient autism model mice exhibited anomalous modulati

Altered sensory experience is now considered a key feature of neurodevelopmental and autism spectrum disorders (ASD). This alteration results in, and often predicts, a range of cognitive, social, and behavioural affective impairments, strongly impacting the quality of life. However, the underlying neurophysiological mechanisms that disrupt sensory perception remain understudied. We investigated these mechanisms in a mouse model of SYNGAP1 haploinsufficiency (ΗΕΤ), SYNGAP1 being one of the most prevalent neurodevelopmental disorder genes. Using in vivo two-photon calcium imaging, we found that

For the long term aim to develop a visual cortical prosthesis, optogenetic stimulation of primary visual cortex (V1) provides a more specific alternative to electrical stimulation. However, adoption of optogenetic techniques from rodents to macaques as an intermediate step towards humans has proven to be challenging. Here we present prelimnary results, directly comparing effects obtained from optogenetic vs electrical stimulation of macaque V1.We injected AAV9-CamKIIa-ChrimsonR-mScarlet-KV2.1 into macaque V1 under electrophysiological guidance. We first investigated neural activity in response

Postsynaptic density protein 95 (PSD-95) is an important signalling scaffold of the PSD of excitatory synapses. We have previously shown that PSD-95 dependent silent synapse maturation closes the critical period (CP) for ocular dominance plasticity in mouse V1: PSD-95 KO mice display both functional & structural hallmarks of CP plasticity and synapses cannot properly stabilize. Since the development of binocularity happens during the CP, we hypothesized that PSD-95 KOs should display compromised binocular integration. To test this hypothesis, we performed both behavioural experiments and m

A fundamental property of neurons in the primary visual cortex is their preference for orientation of edges that is invariant under contrast changes. We designed a synthetic hybrid neural circuit to study the emergence of orientation selectivity under different thalamo-cortical connection schemes. To this end, a computational model of the retino-thalamic pathway was combined with an in-vitro model of cortical input layer 4. The latter was either a primary culture of cortical neurons or an acute horizontal brain slice of primary visual cortex. The two stages were interfaced optogenetically by e

…How neuronal activity encodes visual features in the primary visual cortex (V1) in lit environments and under various luminance levels has been well-studied in many mammalian species. However, how the functionally distinct superficial and deep cortical layers of the V1 encode abrupt and sustained changes in light conditions in freely exploring animals remains unclear. To address this question, we recorded neuro

…affecting neuronal responses in the primary visual cortex (V1). In order to elucidate the functional significance of OH signals for V1 experience-dependent plasticity, we tested orexin KO-mice in the classic ocular dominance plasticity (ODP) paradigm using intrinsic signal optical imaging (OI). Since ODP depends on age and housing conditions, we tested ODP during the critical period (CP) for ODP (P21-P35) and in adults (>P110) with standard cage (SC) housi

…events during different aspects of visual learning.We used 3D two-photon laser scanning microscopy with acousto-optic deflectors to simultaneously record jRGECO1a (calcium) and JEDI-2p (voltage) signals in the apical dendrites of layer 5 pyramidal cells in the primary visual cortex of mice during visual discrimination. We examined mice with controlled water access participating

Preclinical research into dementia with Lewy bodies (DLB) is challenging due to the lack of α-synucleinopathy animal models that do not also develop Parkinsonism. To address this issue, we have developed a new mouse model for investigating the impact of α-synuclein (α-Syn) overexpression and aggregation on driving cortical and hippocampal circuit dysfunction. Using bilateral stereotaxic injections of adeno-associated virus (AAVs) vectors, we transduced overexpression of human SNCA (encoding α-Syn) with mScarlet (red fluorophore), or an mScarlet-only control vector. We targeted either dorsal hi

Sensory neuroprostheses aim to restore sight or hearing through electrical microstimulation viaimplanted neural interfaces. Although there has been significant progress recently, there are stillgaps in our understanding of how to precisely target and activate specific neurons usingintracortical microstimulation. The application of advanced stimulation strategies such as currentsteering and dynamic stimulation might improve control over neuronal activity and keep thenumber of implanted electrodes reasonable. In this study, we developed flexible multi-shankprobes containing iridium-oxide microel