-
Vision Research Apr 2002In their pioneering studies of primary visual cortex, Hubel and Wiesel described the existence of two classes of cells, which they termed "simple" and "complex". The... (Review)
Review
In their pioneering studies of primary visual cortex, Hubel and Wiesel described the existence of two classes of cells, which they termed "simple" and "complex". The original classification scheme was based on a number of partly subjective tests of linear spatial summation. Later, investigators adopted an objective classification method based on the ratio between the amplitude of the first harmonic of the response and the mean spike rate (or the F(1)/F(0) ratio) when the neuron is stimulated with drifting sinusoidal gratings. This measure is bimodally distributed over the population and divides neurons into two classes that correspond closely to the classical definition by Hubel and Wiesel. Here we show that a simple rectification model can predict the observed bimodal distribution of F(1)/F(0) in primary visual cortex when the distributions of the intracellular response modulation and mean are unimodal. Thus, contrary to common belief, the bimodality of F(1)/F(0) does not necessarily imply the existence of two discrete cell classes. Furthermore, in reviewing the literature, we find no independent support for a simple/complex dichotomy. These results suggest that the existence of two distinct neural populations in primary visual cortex, and the associated hierarchical model of receptive field organization, need to be re-evaluated.
Topics: Electrophysiology; Humans; Models, Neurological; Neurons; Visual Cortex
PubMed: 11934453
DOI: 10.1016/s0042-6989(02)00025-1 -
Heliyon Jan 2021This article gives an overview of a normative theory of visual receptive fields. We describe how idealized functional models of early spatial, spatio-chromatic and...
This article gives an overview of a normative theory of visual receptive fields. We describe how idealized functional models of early spatial, spatio-chromatic and spatio-temporal receptive fields can be derived in a principled way, based on a set of axioms that reflect structural properties of the environment in combination with assumptions about the internal structure of a vision system to guarantee consistent handling of image representations over multiple spatial and temporal scales. Interestingly, this theory leads to predictions about visual receptive field shapes with qualitatively very good similarities to biological receptive fields measured in the retina, the LGN and the primary visual cortex (V1) of mammals.
PubMed: 33521348
DOI: 10.1016/j.heliyon.2021.e05897 -
PloS One 2023When multiple stimuli appear together in the receptive field of a visual cortical neuron, the response is typically close to the average of that neuron's response to...
When multiple stimuli appear together in the receptive field of a visual cortical neuron, the response is typically close to the average of that neuron's response to each individual stimulus. The departure from a linear sum of each individual response is referred to as normalization. In mammals, normalization has been best characterized in the visual cortex of macaques and cats. Here we study visually evoked normalization in the visual cortex of awake mice using imaging of calcium indicators in large populations of layer 2/3 (L2/3) V1 excitatory neurons and electrophysiological recordings across layers in V1. Regardless of recording method, mouse visual cortical neurons exhibit normalization to varying degrees. The distributions of normalization strength are similar to those described in cats and macaques, albeit slightly weaker on average.
Topics: Cats; Animals; Mice; Primary Visual Cortex; Photic Stimulation; Visual Cortex; Neurons; Macaca; Mammals
PubMed: 38109430
DOI: 10.1371/journal.pone.0295140 -
Annual Review of Vision Science Sep 2019Recent data have shown that sleep plays a beneficial role for cognitive functions such as declarative memory consolidation and perceptual learning. In this article, we... (Review)
Review
Recent data have shown that sleep plays a beneficial role for cognitive functions such as declarative memory consolidation and perceptual learning. In this article, we review recent findings on the role of sleep in promoting adaptive visual response changes in the lateral geniculate nucleus and primary visual cortex following novel visual experiences. We discuss these findings in the context of what is currently known about how sleep affects the activity and function of thalamocortical circuits and current hypotheses regarding how sleep facilitates synaptic plasticity.
Topics: Animals; Geniculate Bodies; Humans; Neuronal Plasticity; Sleep, REM; Thalamic Nuclei; Visual Cortex; Visual Pathways
PubMed: 31283451
DOI: 10.1146/annurev-vision-091718-014715 -
Proceedings of the National Academy of... Nov 2019Retinotopic specializations in the ventral visual stream, especially foveal adaptations, provide primates with high-acuity vision in the central visual field. However,...
Retinotopic specializations in the ventral visual stream, especially foveal adaptations, provide primates with high-acuity vision in the central visual field. However, visual field specializations have not been studied in the dorsal visual stream, dedicated to processing visual motion and visually guided behaviors. To investigate this, we injected retrograde neuronal tracers occupying the whole visuotopic representation of the middle temporal (MT) visual area in marmoset monkeys and studied the distribution and morphology of the afferent primary visual cortex (V1) projections. Contrary to previous reports, we found a heterogeneous population of V1-MT projecting neurons distributed in layers 3C and 6. In layer 3C, spiny stellate neurons were distributed mainly in foveal representations, while pyramidal morphologies were characteristic of peripheral eccentricities. This primate adaptation of the V1 to MT pathway is arranged in a way that we had not previously understood, with abundant stellate projection neurons in the high-resolution foveal portions, suggesting rapid relay of motion information to visual area MT. We also describe that the medial portion of the inferior pulvinar (PIm), which is the main thalamic input to area MT, shows a retinotopic organization, likely reflecting the importance of this pathway during development and the establishment of area MT topography.
Topics: Animals; Brain Mapping; Callithrix; Neuronal Tract-Tracers; Pulvinar; Visual Cortex
PubMed: 31659044
DOI: 10.1073/pnas.1909799116 -
Frontiers in Systems Neuroscience 2018The visual system is constantly bombarded with information originating from the outside world, but it is unable to process all the received information at any given... (Review)
Review
The visual system is constantly bombarded with information originating from the outside world, but it is unable to process all the received information at any given time. In fact, the most salient parts of the visual scene are chosen to be processed involuntarily and immediately after the first glance along with endogenous signals in the brain. Vision scientists have shown that the early visual system, from retina to lateral geniculate nucleus (LGN) and then primary visual cortex, selectively processes the low-level features of the visual scene. Everything we perceive from the visual scene is based on these feature properties and their subsequent combination in higher visual areas. Different experiments have been designed to investigate the impact of these features on saliency and understand the relative visual mechanisms. In this paper, we review the psychophysical experiments which have been published in the last decades to indicate how the low-level salient features are processed in the early visual cortex and extract the most important and basic information of the visual scene. Important and open questions are discussed in this review as well and one might pursue these questions to investigate the impact of higher level features on saliency in complex scenes or natural images.
PubMed: 30416433
DOI: 10.3389/fnsys.2018.00054 -
Neurobiology of Aging Mar 2022There is an urgent need for a better understanding of the pathophysiology of cognitive impairment in syndromes associated with frontotemporal lobar degeneration. Here,...
There is an urgent need for a better understanding of the pathophysiology of cognitive impairment in syndromes associated with frontotemporal lobar degeneration. Here, we used magnetic resonance spectroscopy to quantify metabolite deficits in sixty patients with a clinical syndrome associated with frontotemporal lobar degeneration (behavioral variant frontotemporal dementia n = 11, progressive supranuclear palsy n = 26, corticobasal syndrome n = 11, primary progressive aphasias n = 12), and 38 age- and sex-matched healthy controls. We measured nine metabolites in the right inferior frontal gyrus, superior temporal gyrus and right primary visual cortex. Metabolite concentrations were corrected for age, sex, and partial volume then compared with cognitive and behavioral measures using canonical correlation analysis. Metabolite concentrations varied significantly by brain region and diagnosis (region x metabolite x diagnosis interaction F = 1.73, p < 0.001, corrected for age, sex, and atrophy within the voxel). N-acetyl aspartate and glutamate concentrations were reduced in the right prefrontal cortex in behavioral variant frontotemporal dementia and progressive supranuclear palsy, even after partial volume correction. The reduction of these metabolites was associated with executive dysfunction and behavioral impairment (canonical correlation analysis R = 0.85, p < 0.001).
Topics: Aged; Aspartic Acid; Behavior; Cognition; Executive Function; Female; Frontotemporal Lobar Degeneration; Glutamates; Humans; Male; Middle Aged; Prefrontal Cortex; Primary Visual Cortex; Proton Magnetic Resonance Spectroscopy; Temporal Lobe
PubMed: 34971846
DOI: 10.1016/j.neurobiolaging.2021.10.012 -
Magnetic Resonance in Medical Sciences... 2016This article reviews our exploration of structures and functions of the human visual cortex using high resolution (submillimeter) functional magnetic resonance imaging... (Review)
Review
This article reviews our exploration of structures and functions of the human visual cortex using high resolution (submillimeter) functional magnetic resonance imaging (fMRI). It discusses factors that restrict the spatial resolution of blood oxygenation-level dependent (BOLD) fMRI-the point-spread function of the BOLD signal, limited by both imaging techniques to be used and neurovascular units to be studied, and the signal-to-noise ratio. I offer personal thoughts regarding optimal solutions for dealing with these issues, summarize techniques we have developed over the years for using high resolution fMRI to visualize functional architectures and explore physiological properties in the primary visual cortex of humans, including choices of imaging hardware and pulse sequences, experimental procedures, and stimulation paradigms, and finally offer my personal opinions regarding the future of high resolution fMRI.
Topics: Cerebrovascular Circulation; Humans; Image Enhancement; Magnetic Resonance Imaging; Oxygen; Oxygen Consumption; Signal-To-Noise Ratio; Visual Cortex
PubMed: 26104083
DOI: 10.2463/mrms.2015-0008 -
Neurobiology of Disease Nov 2022Experience-dependent neuronal changes and brain plasticity occur throughout life as animals adapt to their environment. Structural, morphological, and cellular...
Experience-dependent neuronal changes and brain plasticity occur throughout life as animals adapt to their environment. Structural, morphological, and cellular modifications promoted by exposure to environmental enrichment (EE) have been reported to improve neuronal functions, increase hippocampal neurogenesis, ameliorate memory tasks and cognitive performance, and have beneficial effects on several brain diseases, including cancer. We specifically addressed the role of the EE in counteracting neuronal dysfunction in mice bearing glioma in the primary visual cortex. By recording spontaneous and evoked currents with patch clamp techniques in acute slices obtained from standard and enriched-housed mice, we found that the presence of glioma globally reduced the excitatory and inhibitory transmissions in the peritumoral area. The exposure to an enriched environment counteracts the tumor-mediated depression of both excitatory and inhibitory neuronal activities, with a more pronounced impact on evoked transmission. The effect of EE on glioma was also associated with reduced tumor cell proliferation. These results elucidate the impact of EE on excitatory and inhibitory neurotransmission of the primary visual cortex in control and glioma-bearing mice.
Topics: Mice; Animals; Primary Visual Cortex; Environment; Neuronal Plasticity; Synaptic Transmission; Glioma
PubMed: 36240950
DOI: 10.1016/j.nbd.2022.105894 -
Learning & Memory (Cold Spring Harbor,... Oct 2014It has been more than 50 years since the first description of ocular dominance plasticity--the profound modification of primary visual cortex (V1) following temporary... (Review)
Review
It has been more than 50 years since the first description of ocular dominance plasticity--the profound modification of primary visual cortex (V1) following temporary monocular deprivation. This discovery immediately attracted the intense interest of neurobiologists focused on the general question of how experience and deprivation modify the brain as a potential substrate for learning and memory. The pace of discovery has quickened considerably in recent years as mice have become the preferred species to study visual cortical plasticity, and new studies have overturned the dogma that primary sensory cortex is immutable after a developmental critical period. Recent work has shown that, in addition to ocular dominance plasticity, adult visual cortex exhibits several forms of response modification previously considered the exclusive province of higher cortical areas. These "higher brain functions" include neural reports of stimulus familiarity, reward-timing prediction, and spatiotemporal sequence learning. Primary visual cortex can no longer be viewed as a simple visual feature detector with static properties determined during early development. Rodent V1 is a rich and dynamic cortical area in which functions normally associated only with "higher" brain regions can be studied at the mechanistic level.
Topics: Animals; Mice; Neuronal Plasticity; Pattern Recognition, Visual; Rats; Recognition, Psychology; Reward; Visual Cortex
PubMed: 25225298
DOI: 10.1101/lm.034355.114