scholarly journals Unidirectional monosynaptic connections from auditory areas to the primary visual cortex in the marmoset monkey

2018 ◽  
Author(s):  
Piotr Majka ◽  
Marcello G. P. Rosa ◽  
Shi Bai ◽  
Jonathan M. Chan ◽  
Bing-Xing Huo ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Auditory Cortex ◽  
Primary Visual Cortex ◽  
Peripheral Vision ◽  
Early Stage ◽  
World Monkey ◽  
Primary Auditory Cortex ◽  
Audiovisual Integration ◽  
Primate Species ◽  
Retrograde Tracer

AbstractUntil the late 20th Century, it was believed that different sensory modalities were processed by largely independent pathways in the primate cortex, with cross-modal integration only occurring in specialized polysensory areas. This model was challenged by the finding that the peripheral representation of the primary visual cortex (V1) receives monosynaptic connections from areas of the auditory cortex in the macaque. However, auditory projections to V1 have not been reported in other primates. We investigated the existence of direct interconnections between V1 and auditory areas in the marmoset, a New World monkey. Labelled neurons in auditory cortex were observed following 4 out of 10 retrograde tracer injections involving V1. These projections to V1 originated in the caudal subdivisions of auditory cortex (primary auditory cortex, caudal belt and parabelt areas), and targeted parts of V1 that represent parafoveal and peripheral vision. Injections near the representation of the vertical meridian of the visual field labelled few or no cells in auditory cortex. We also placed 8 retrograde tracer injections involving core, belt and parabelt auditory areas, none of which revealed direct projections from V1. These results confirm the existence of a direct, nonreciprocal projection from auditory areas to V1 in a different primate species, which has evolved separately from the macaque for over 30 million years. The essential similarity of these observations between marmoset and macaque indicate that early-stage audiovisual integration is a shared characteristic of primate sensory processing.

scholarly journals The Retinal Inner Plexiform Synaptic Layer Mirrors Grey Matter Thickness of Primary Visual Cortex with Increased Amyloid β Load in Early Alzheimer’s Disease

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Lília Jorge ◽  
Nádia Canário ◽  
Ricardo Martins ◽  
Beatriz Santiago ◽  
Isabel Santana ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Early Stage ◽  
Amyloid Β ◽  
Synaptic Function ◽  
Binding Potential ◽  
Inner Plexiform Layer ◽  
Pet Tracer

The retina may serve as putative window into neuropathology of synaptic loss in Alzheimer’s disease (AD). Here, we investigated synapse-rich layers versus layers composed by nuclei/cell bodies in an early stage of AD. In addition, we examined the associations between retinal changes and molecular and structural markers of cortical damage. We recruited 20 AD patients and 17 healthy controls (HC). Combining optical coherence tomography (OCT), magnetic resonance (MR), and positron emission tomography (PET) imaging, we measured retinal and primary visual cortex (V1) thicknesses, along with V1 amyloid β (Aβ) retention ([11C]-PiB PET tracer) and neuroinflammation ([11C]-PK11195 PET tracer). We found that V1 showed increased amyloid-binding potential, in the absence of neuroinflammation. Although thickness changes were still absent, we identified a positive association between the synapse-rich inner plexiform layer (IPL) and V1 in AD. This retinocortical interplay might reflect changes in synaptic function resulting from Aβ deposition, contributing to early visual loss.

Audiovisual integration in the primary auditory cortex of an awake rodent

2013 ◽  
Vol 534 ◽  
pp. 24-29 ◽  
Author(s):  
Kohta I. Kobayasi ◽  
Yoichi suwa ◽  
Hiroshi Riquimaroux
Keyword(s):  
Auditory Cortex ◽  
Primary Auditory Cortex ◽  
Audiovisual Integration

scholarly journals Local Homogeneity of Tonotopic Organization in the Primary Auditory Cortex of Marmosets

2018 ◽  
Author(s):  
Huan-huan Zeng ◽  
Jun-feng Huang ◽  
Ming Chen ◽  
Yun-qing Wen ◽  
Zhi-ming Shen ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Large Scale ◽  
Frequency Tuning ◽  
Primary Auditory Cortex ◽  
Primate Species ◽  
Tonotopic Organization ◽  
Brain Structure And Function ◽  
A1 Neurons ◽  
Cortical Regions

AbstractMarmoset has emerged as a useful non-human primate species for studying the brain structure and function. Previous studies on the mouse primary auditory cortex (A1) showed that neurons with preferential frequency tuning responses are mixed within local cortical regions, despite a large-scale tonotopic organization. Here we found that frequency tuning properties of marmoset A1 neurons are highly uniform within local cortical regions. We first defined tonotopic map of A1 using intrinsic optical imaging, and then used in vivo two-photon calcium imaging of large neuronal populations to examine the tonotopic preference at the single-cell level. We found that tuning preferences of layer 2/3 neurons were highly homogeneous over hundreds of micrometers in both horizontal and vertical directions. Thus, marmoset A1 neurons are distributed in a tonotopic manner at both macro- and microscopic levels. Such organization is likely to be important for the organization of auditory circuits in the primate brain.

scholarly journals Ecological trait differences are associated with gene expression in the primary visual cortex of primates

2020 ◽  
Author(s):  
Trisha Marie Zintel ◽  
John J. Ely ◽  
Mary Ann Raghanti ◽  
William D. Hopkins ◽  
Patrick R. Hof ◽  
...  
Keyword(s):  
Gene Expression ◽  
Visual Cortex ◽  
Visual System ◽  
Color Vision ◽  
Primary Visual Cortex ◽  
Brain Regions ◽  
Primate Species ◽  
Tissue Samples ◽  
Synaptic Signaling ◽  
Species Specific

Abstract Background : Primate species differ drastically from most other mammals in how they visually perceive their environments, which is important for foraging, predator avoidance, and detection of social cues. Although it is well established that primates display diversity in color vision and various ecological specializations, it is not understood how visual system characteristics and ecological adaptations may be associated with gene expression levels within the primary visual cortex (V1). Results : We performed RNA-Seq on V1 tissue samples from 28 individuals, representing 13 species of anthropoid primates, including hominoids, cercopithecoids, and platyrrhines. We explored trait-dependent differential expression (DE) by contrasting species with different visual system phenotypes and ecological traits. Between 4-25% of genes were determined to be differentially expressed in primates that varied in type of color vision (trichromatic or polymorphic di/trichromatic), habitat use (arboreal or terrestrial), group size (large or small), and primary diet (frugivorous, folivorous, or omnivorous). DE analyses revealed that humans and chimpanzees showed the most marked differences between any two species, despite the fact that they are only separated by 6-8 million years of independent evolution. Pathway enrichment analyses of DE genes demonstrated that changes in cellular metabolic pathways (e.g. glycolysis) contribute to altered gene expression in primate V1 more than neuron-specific processes (e.g. synaptic signaling). The exception to this trend is between human and chimpanzee, which exhibited DE for a number of processes related to cholinergic and GABAergic synaptic signaling. Conclusions : Our data significantly expand the number of primate species for which V1 expression data exists. These results show a combination of species-specific and trait-dependent differences in the evolution of gene expression in primate V1. We also show that human-specific changes in brain gene expression extend to the primary visual cortex in a manner similar to that reported of other brain regions.

scholarly journals Auditory detection is modulated by theta phase of silent lip movements

2020 ◽  
Author(s):  
Emmanuel Biau ◽  
Danying Wang ◽  
Hyojin Park ◽  
Ole Jensen ◽  
Simon Hanslmayr
Keyword(s):  
Visual Cortex ◽  
Speech Perception ◽  
Auditory Cortex ◽  
Primary Auditory Cortex ◽  
Theta Oscillations ◽  
Neural Oscillations ◽  
Audiovisual Speech Perception ◽  
Auditory Detection ◽  
Theta Phase ◽  
Silent Speech

ABSTRACTAudiovisual speech perception relies, among other things, on our expertise to map a speaker’s lip movements with speech sounds. This multimodal matching is facilitated by salient syllable features that align lip movements and acoustic envelope signals in the 4 - 8 Hz theta band. Although non-exclusive, the predominance of theta rhythms in speech processing has been firmly established by studies showing that neural oscillations track the acoustic envelope in the primary auditory cortex. Equivalently, theta oscillations in the visual cortex entrain to lip movements, and the auditory cortex is recruited during silent speech perception. These findings suggest that neuronal theta oscillations may play a functional role in organising information flow across visual and auditory sensory areas. We presented silent speech movies while participants performed a pure tone detection task to test whether entrainment to lip movements directs the auditory system and drives behavioural outcomes. We showed that auditory detection varied depending on the ongoing theta phase conveyed by lip movements in the movies. In a complementary experiment presenting the same movies while recording participants’ electro-encephalogram (EEG), we found that silent lip movements entrained neural oscillations in the visual and auditory cortices with the visual phase leading the auditory phase. These results support the idea that the visual cortex entrained by lip movements filtered the sensitivity of the auditory cortex via theta phase synchronisation.

scholarly journals The neural signature of numerosity: Separating numerical and continuous magnitude extraction in early visual cortex with frequency-tagged EEG

2019 ◽  
Author(s):  
Amandine Van Rinsveld ◽  
Mathieu Guillaume ◽  
Peter J. Kohler ◽  
Christine Schiltz ◽  
Wim Gevers ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Convex Hull ◽  
Primary Visual Cortex ◽  
Early Stage ◽  
Visual Scene ◽  
Model Output ◽  
Mathematical Skills ◽  
Early Visual Cortex ◽  
Numerical Magnitudes ◽  
Neural Signature

AbstractThe ability to handle approximate quantities, or number sense, has been recurrently linked to mathematical skills, though the nature of the mechanism allowing to extract numerical information (i.e., numerosity) from environmental stimuli is still debated. A set of objects is indeed not only characterized by its numerosity but also by other features, such as the summed area occupied by the elements, which often covary with numerosity. These intrinsic relations between numerosity and non-numerical magnitudes led some authors to argue that numerosity is not independently processed but extracted through a weighting of continuous magnitudes. This view cannot be properly tested through classic behavioral and neuroimaging approaches due to these intrinsic correlations. The current study used a frequency-tagging EEG approach to separately measure responses to numerosity as well as to continuous magnitudes. We recorded occipital responses to numerosity, total area, and convex hull changes but not to density and dot size. We additionally applied a model predicting primary visual cortex responses to the set of stimuli. The model output was closely aligned with our electrophysiological data, since it predicted discrimination only for numerosity, total area, and convex hull. Our findings thus demonstrate that numerosity can be independently processed at an early stage in the visual cortex, even when completely isolated from other magnitude changes. The similar implicit discrimination for numerosity as for some continuous magnitudes, which correspond to basic visual percepts, shows that both can be extracted independently, hence substantiating the nature of numerosity as a primary feature of the visual scene.

Frequency-Modulation Encoding in the Primary Auditory Cortex of the Awake Owl Monkey

2007 ◽  
Vol 98 (4) ◽  
pp. 2182-2195 ◽  
Author(s):  
Craig A. Atencio ◽  
David T. Blake ◽  
Fabrizio Strata ◽  
Steven W. Cheung ◽  
Michael M. Merzenich ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
World Monkey ◽  
Receptive Fields ◽  
Primary Auditory Cortex ◽  
Direction Selectivity ◽  
Neural Responses ◽  
Population Distributions ◽  
Spectrotemporal Receptive Fields ◽  
Owl Monkey ◽  
Highly Correlated

Many communication sounds, such as New World monkey twitter calls, contain frequency-modulated (FM) sweeps. To determine how this prominent vocalization element is represented in the auditory cortex we examined neural responses to logarithmic FM sweep stimuli in the primary auditory cortex (AI) of two awake owl monkeys. Using an implanted array of microelectrodes we quantitatively characterized neuronal responses to FM sweeps and to random tone-pip stimuli. Tone-pip responses were used to construct spectrotemporal receptive fields (STRFs). Classification of FM sweep responses revealed few neurons with high direction and speed selectivity. Most neurons responded to sweeps in both directions and over a broad range of sweep speeds. Characteristic frequency estimates from FM responses were highly correlated with estimates from STRFs, although spectral receptive field bandwidth was consistently underestimated by FM stimuli. Predictions of FM direction selectivity and best speed from STRFs were significantly correlated with observed FM responses, although some systematic discrepancies existed. Last, the population distributions of FM responses in the awake owl monkey were similar to, although of longer temporal duration than, those in the anesthetized squirrel monkeys.

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