scholarly journals Visual cortical entrainment to unheard acoustic speech reflects intelligibility of lip movements and is mediated by dorsal stream regions

2018 ◽  
Author(s):  
A. Hauswald ◽  
C. Lithari ◽  
O. Collignon ◽  
E. Leonardelli ◽  
N. Weisz
Keyword(s):  
Visual Cortex ◽  
Acoustic Signal ◽  
Temporal Cortex ◽  
Dorsal Stream ◽  
List Type ◽  
Top Down ◽  
Entrainment Effect ◽  
Speech Envelope ◽  
Cortical Entrainment ◽  
Visual Cortical

AbstractSuccessful lip reading requires a mapping from visual to phonological information [1]. Recently, visual and motor cortices have been implicated in tracking lip movements (e.g. [2]). It remains unclear, however, whether visuo-phonological mapping occurs already at the level of the visual cortex, that is, whether this structure tracks the acoustic signal in a functionally relevant manner. In order to elucidate this, we investigated how the cortex tracks (i.e. entrains) absent acoustic speech signals carried by silent lip movements. Crucially, we contrasted the entrainment to unheard forward (intelligible) and backward (unintelligible) acoustic speech. We observed that the visual cortex exhibited stronger entrainment to the unheard forward acoustic speech envelope compared to the unheard backward acoustic speech envelope. Supporting the notion of a visuo-phonological mapping process, this forward-backward difference of occipital entrainment was not present for actually observed lip movements. Importantly, the respective occipital region received more top-down input especially from left premotor, primary motor, somatosensory regions and, to a lesser extent, also from posterior temporal cortex. Strikingly, across participants, the extent of top-down modulation of visual cortex stemming from these regions partially correlates with the strength of entrainment to absent acoustic forward speech envelope but not to present forward lip movements. Our findings demonstrate that a distributed cortical network, including key dorsal stream auditory regions [3–5], influence how the visual cortex shows sensitivity to the intelligibility of speech while tracking silent lip movements.HighlightsVisual cortex tracks better forward than backward unheard acoustic speech envelopeEffects not “trivially” caused by correlation of visual with acoustic signalStronger top-down control of visual cortex during forward display of lip movementsTop-down influence correlates with visual cortical entrainment effectResults seem to reflect visuo-phonological mapping processes

scholarly journals Layer-dependent multiplicative effects of spatial attention on contrast responses in human early visual cortex

2020 ◽  
Author(s):  
Fanhua Guo ◽  
Chengwen Liu ◽  
Chencan Qian ◽  
Zihao Zhang ◽  
Kaibao Sun ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Spatial Attention ◽  
Middle Layer ◽  
Additive Effect ◽  
List Type ◽  
Strong Nonlinearity ◽  
Top Down ◽  
Contrast Gain ◽  
Early Visual Cortex ◽  
Deep Layers

AbstractAttention mechanisms at different cortical layers of human visual cortex remain poorly understood. Using submillimeter-resolution fMRI at 7T, we investigated the effects of top-down spatial attention on the contrast responses across different cortical depths in human early visual cortex. Gradient echo (GE) T2* weighted BOLD signal showed an additive effect of attention on contrast responses across cortical depths. Compared to the middle cortical depth, attention modulation was stronger in the superficial and deep depths of V1, and also stronger in the superficial depth of V2 and V3. Using ultra-high resolution (0.3mm in-plane) balanced steady-state free precession (bSSFP) fMRI, a multiplicative scaling effect of attention was found in the superficial and deep layers, but not in the middle layer of V1. Attention modulation of low contrast response was strongest in the middle cortical depths, indicating baseline enhancement or contrast gain of attention modulation on feedforward input. Finally, the additive effect of attention on T2* BOLD can be explained by strong nonlinearity of BOLD signals from large blood vessels, suggesting multiplicative effect of attention on neural activity. These findings support that top-down spatial attention mainly operates through feedback connections from higher order cortical areas, and a distinct mechanism of attention may also be associated with feedforward input through subcortical pathway.HighlightsResponse or activity gain of spatial attention in superficial and deep layersContrast gain or baseline shift of attention in V1 middle layerNonlinearity of large blood vessel causes additive effect of attention on T2* BOLD

scholarly journals Auditory features modelling demonstrates sound envelope representation in striate cortex

2020 ◽  
Author(s):  
Alice Martinelli ◽  
Giacomo Handjaras ◽  
Monica Betta ◽  
Andrea Leo ◽  
Luca Cecchetti ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Spectral Properties ◽  
Striate Cortex ◽  
Temporal Cortex ◽  
Semantic Content ◽  
Functional Magnetic Resonance ◽  
Retinal Input ◽  
Speech Envelope ◽  
Auditory Features ◽  
Multisensory Processes

SummaryPrimary visual cortex is no longer considered exclusively visual in its function. Proofs that its activity plays a role in multisensory processes have accrued. Here we provide evidence that, in absence of retinal input, V1 maps sound envelope information. We modeled amplitude changes occurring at typical speech envelope time-scales of four hierarchically-organized categories of natural (or synthetically derived) sounds. Using functional magnetic resonance, we assessed whether sound amplitude variations were represented in striate cortex and, as a control, in the temporal cortex. Sound amplitude mapping in V1 occurred regardless of the semantic content, was dissociated from the spectral properties of sounds and was not restricted to speech material. As in the temporal cortex, a spatially organized representation of amplitude modulation frequencies emerged in V1. Our results demonstrate that human striate cortex is a locus of representation of sound attributes.

scholarly journals Cortical tracking of speech reveals top-down reconstructive processes

2019 ◽  
Author(s):  
Sankar Mukherjee ◽  
Alice Tomassini ◽  
Leonardo Badino ◽  
Aldo Pastore ◽  
Luciano Fadiga ◽  
...  
Keyword(s):  
Predictive Model ◽  
Experimental Test ◽  
Speech Comprehension ◽  
Missing Information ◽  
Top Down ◽  
Sensory Signals ◽  
Analysis By Synthesis ◽  
Neural Entrainment ◽  
Speech Envelope ◽  
Cortical Entrainment

AbstractCortical entrainment to the (quasi-) rhythmic components of speech seems to play an important role in speech comprehension. It has been suggested that neural entrainment may reflect top-down temporal predictions of sensory signals. Key properties of a predictive model are its anticipatory nature and its ability to reconstruct missing information. Here we put both these two properties to experimental test. We acoustically presented sentences and measured cortical entrainment to both acoustic speech envelope and lips kinematics acquired from the speaker but not visible to the participants. We then analyzed speech-brain and lips-brain coherence at multiple negative and positive lags. Besides the well-known cortical entrainment to the acoustic speech envelope, we found significant entrainment in the delta range to the (latent) lips kinematics. Most interestingly, the two entrainment phenomena were temporally dissociated. While entrainment to the acoustic speech peaked around +0.3 s lag (i.e., when EEG followed speech by 0.3 s), entrainment to the lips was significantly anticipated and peaked around 0-0.1 s lag (i.e., when EEG was virtually synchronous to the putative lips movement). Our results demonstrate that neural entrainment during speech listening involves the anticipatory reconstruction of missing information related to lips movement production, indicating its fundamentally predictive nature and thus supporting analysis by synthesis models.

scholarly journals Characterization of Feedback Neurons in the High-Level Visual Cortical Areas That Project Directly to the Primary Visual Cortex in the Cat

2021 ◽  
Vol 14 ◽  
Author(s):  
Huijun Pan ◽  
Shen Zhang ◽  
Deng Pan ◽  
Zheng Ye ◽  
Hao Yu ◽  
...  
Keyword(s):  
Information Processing ◽  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Visual Information ◽  
Higher Order ◽  
Top Down ◽  
Cortical Areas ◽  
Area 21A ◽  
High Level ◽  
Visual Cortical

Previous studies indicate that top-down influence plays a critical role in visual information processing and perceptual detection. However, the substrate that carries top-down influence remains poorly understood. Using a combined technique of retrograde neuronal tracing and immunofluorescent double labeling, we characterized the distribution and cell type of feedback neurons in cat’s high-level visual cortical areas that send direct connections to the primary visual cortex (V1: area 17). Our results showed: (1) the high-level visual cortex of area 21a at the ventral stream and PMLS area at the dorsal stream have a similar proportion of feedback neurons back projecting to the V1 area, (2) the distribution of feedback neurons in the higher-order visual area 21a and PMLS was significantly denser than in the intermediate visual cortex of area 19 and 18, (3) feedback neurons in all observed high-level visual cortex were found in layer II–III, IV, V, and VI, with a higher proportion in layer II–III, V, and VI than in layer IV, and (4) most feedback neurons were CaMKII-positive excitatory neurons, and few of them were identified as inhibitory GABAergic neurons. These results may argue against the segregation of ventral and dorsal streams during visual information processing, and support “reverse hierarchy theory” or interactive model proposing that recurrent connections between V1 and higher-order visual areas constitute the functional circuits that mediate visual perception. Also, the corticocortical feedback neurons from high-level visual cortical areas to the V1 area are mostly excitatory in nature.

scholarly journals Perceptual Learning of Simple Stimuli Modifies Stimulus Representations in Posterior Inferior Temporal Cortex

2014 ◽  
Vol 26 (10) ◽  
pp. 2187-2200 ◽  
Author(s):  
Hamed Zivari Adab ◽  
Ivo D. Popivanov ◽  
Wim Vanduffel ◽  
Rufin Vogels
Keyword(s):  
Visual Cortex ◽  
Perceptual Learning ◽  
Single Unit ◽  
Brain Plasticity ◽  
Temporal Cortex ◽  
Adult Brain ◽  
Orientation Discrimination ◽  
Area V4 ◽  
Early Visual Cortex ◽  
Visual Cortical

Practicing simple visual detection and discrimination tasks improves performance, a signature of adult brain plasticity. The neural mechanisms that underlie these changes in performance are still unclear. Previously, we reported that practice in discriminating the orientation of noisy gratings (coarse orientation discrimination) increased the ability of single neurons in the early visual area V4 to discriminate the trained stimuli. Here, we ask whether practice in this task also changes the stimulus tuning properties of later visual cortical areas, despite the use of simple grating stimuli. To identify candidate areas, we used fMRI to map activations to noisy gratings in trained rhesus monkeys, revealing a region in the posterior inferior temporal (PIT) cortex. Subsequent single unit recordings in PIT showed that the degree of orientation selectivity was similar to that of area V4 and that the PIT neurons discriminated the trained orientations better than the untrained orientations. Unlike in previous single unit studies of perceptual learning in early visual cortex, more PIT neurons preferred trained compared with untrained orientations. The effects of training on the responses to the grating stimuli were also present when the animals were performing a difficult orthogonal task in which the grating stimuli were task-irrelevant, suggesting that the training effect does not need attention to be expressed. The PIT neurons could support orientation discrimination at low signal-to-noise levels. These findings suggest that extensive practice in discriminating simple grating stimuli not only affects early visual cortex but also changes the stimulus tuning of a late visual cortical area.

scholarly journals Tailored haemodynamic response function increases detection power of fMRI in awake dogs (Canis familiaris)

2020 ◽  
Author(s):  
Magdalena Boch ◽  
Sabrina Karl ◽  
Ronald Sladky ◽  
Ludwig Huber ◽  
Claus Lamm ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Response Function ◽  
Visual Stimulation ◽  
Canis Familiaris ◽  
Temporal Cortex ◽  
Model Fit ◽  
Haemodynamic Response ◽  
List Type ◽  
Bold Signal ◽  
Detection Power

AbstractFunctional magnetic resonance imaging (fMRI) of awake and unrestrained dogs (Canis familiaris) has been established as a novel opportunity for comparative neuroimaging, promising important insights into the evolutionary roots of human brain function and cognition. However, data processing and analysis pipelines are often derivatives of methodological standards developed for human neuroimaging, which may be problematic due to profound neurophysiological and anatomical differences between humans and dogs. Here, we explore whether dog fMRI studies would benefit from a tailored dog haemodynamic response function (HRF). In two independent experiments, dogs were presented with different visual stimuli. BOLD signal changes in the visual cortex during these experiments were used for (a) the identification and estimation of a tailored dog HRF, and (b) the independent validation of the resulting dog HRF estimate. Time course analyses revealed that the BOLD signal in the primary visual cortex peaks significantly earlier in dogs compared to humans, while being comparable in shape. Deriving a tailored dog HRF significantly improved the model fit in both experiments, compared to the canonical HRF used in human fMRI. Using the dog HRF yielded significantly increased activation during visual stimulation, extending from the occipital lobe, to the caudal parietal cortex, the bilateral temporal cortex, and into bilateral hippocampal and thalamic regions. In sum, our findings provide robust evidence for an earlier onset of the dog HRF in a visual stimulation paradigm, and suggest that using such an HRF will be important to increase fMRI detection power in canine neuroimaging. By providing the parameters of the tailored dog HRF and related code, we encourage and enable other researchers to validate whether our findings generalize to other sensory modalities and experimental paradigms.HighlightsDog fMRI typically uses human HRF, but underlying neurophysiology might differV1 BOLD signal peaked earlier in dogs than predicted by the human HRFTailored dog HRF improved model fit when tested with independent dataWhole-brain comparisons confirmed increased detection power for tailored dog HRFDog fMRI will benefit from increased detection power of tailored HRF

scholarly journals Distributed and Retinotopically Asymmetric Processing of Coherent Motion in Mouse Visual Cortex

2019 ◽  
Author(s):  
Kevin K. Sit ◽  
Michael J. Goard
Keyword(s):  
Visual Cortex ◽  
Visual Motion ◽  
Dorsal Stream ◽  
Coherent Motion ◽  
Motion Processing ◽  
Calcium Indicator ◽  
Mouse Cortex ◽  
Visual Areas ◽  
Cortical Regions ◽  
Visual Cortical

ABSTRACTPerception of visual motion is important for a range of ethological behaviors in mammals. In primates, specific higher visual cortical regions are specialized for processing of coherent visual motion. However, the distribution of motion processing among visual cortical areas in mice is unclear, despite the powerful genetic tools available for measuring population neural activity. Here, we used widefield and 2-photon calcium imaging of transgenic mice expressing a calcium indicator in excitatory neurons to measure mesoscale and cellular responses to coherent motion across the visual cortex. Imaging of primary visual cortex (V1) and several higher visual areas (HVAs) during presentation of natural movies and random dot kinematograms (RDKs) revealed heterogeneous responses to coherent motion. Although coherent motion responses were observed throughout visual cortex, particular HVAs in the putative dorsal stream (PM, AL, AM) exhibited stronger responses than ventral stream areas (LM and LI). Moreover, beyond the differences between visual areas, there was considerable heterogeneity within each visual area. Individual visual areas exhibited an asymmetry across the vertical retinotopic axis (visual elevation), such that neurons representing the inferior visual field exhibited greater responses to coherent motion. These results indicate that processing of visual motion in mouse cortex is distributed unevenly across visual areas and exhibits a spatial bias within areas, potentially to support processing of optic flow during spatial navigation.

scholarly journals Semiology, clustering, periodicity and natural history of seizures in an experimental visual cortical epilepsy model

2018 ◽  
Author(s):  
Bao-Luen Chang ◽  
Leite Marco ◽  
Albert Snowball ◽  
Elodie Chabrol ◽  
Andreas Lieb ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Tetanus Toxin ◽  
Circadian Variation ◽  
Unmet Need ◽  
List Type ◽  
Robust Model ◽  
Clonic Seizures ◽  
Neocortical Epilepsy ◽  
Novel Therapeutic Strategies ◽  
Visual Cortical

SummaryObjectiveTo characterize a rat model of focal neocortical epilepsy for use in developing novel therapeutic strategies in a type of epilepsy that represents a significant unmet need.MethodsIntracortical tetanus toxin (TeNT) injection was used to induce epilepsy in rats. Seizures and their behavioural manifestations were evaluated with continuous video-electrocorticography telemetry.ResultsTeNT injection into rat primary visual cortex induced focal neocortical epilepsy without preceding status epilepticus. The latency to first seizure ranged from 3 to 7 days. Seizure duration was bimodal, with both short (approximately 30s) and long-lasting (>100s) seizures occurring in the same animals. Seizures were accompanied by non-motor features such as behavioural arrest, or motor seizures with or without evolution to generalized tonic-clonic seizures. Seizures were commoner during the sleep phase of a light-dark cycle. Seizure occurrence was not random, and tended to cluster with significantly higher probability of recurrence within 24 hours of a previous seizure. Across animals, the number of seizures in the first week could be used to predict the number of seizures in the following 22 days.SignificanceThe TeNT model of visual cortical epilepsy is a robust model of acquired focal neocortical epilepsy, and is well suited for preclinical evaluation of novel anti-epileptic strategies. We provide here a detailed analysis of the epilepsy phenotype, seizure activity, electrographic features, and the semiology. In addition we provide a predictive framework that can be used to reduce variation and consequently animal use in pre-clinical studies of potential treatments.Key PointsTetanus toxin injection into rat visual cortex induces focal cortical epilepsy.Electrographic seizures were associated with non-motor and motor features with or without evolution to generalized tonic-clonic seizures.Seizures could not be provoked by intermittent photic stimulation.Seizures were clustered in time and exhibited a circadian variation in frequency.The number of seizures in first week after seizure onset could be used to predict the total number of seizures in the following 3 weeks.

scholarly journals Visual Cortical Area MT is Required for Development of the Dorsal Stream and Associated Visuomotor Behaviours

2021 ◽  
Author(s):  
William C. Kwan ◽  
Chia-Kang Chang ◽  
Hsin-Hao Yu ◽  
Inaki C. Mundinano ◽  
Dylan M. Fox ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Early Life ◽  
Dorsal Stream ◽  
Visually Guided ◽  
Area Mt ◽  
V1 Neurons ◽  
Visual Cortical Area ◽  
Direction Sensitivity ◽  
Visual Cortical ◽  
And Function

AbstractThe middle temporal (MT) area of the extrastriate visual cortex has long been studied in adulthood for its distinctive physiological properties and function as a part of the dorsal stream, yet interestingly possesses a similar maturation profile as the primary visual cortex (V1). Here we examined whether an early-life lesion of MT altered the dorsal stream development and the behavioural precision of reaching to grasp sequences. We observed permanent changes in the anatomy of cortices associated with both reaching (PE and MIP) and grasping (AIP), as well as in reaching and grasping behaviours. In addition, we observed a significant impact on the anatomy of V1 and the direction sensitivity of V1 neurons in the lesion projection zone. These findings indicate that area MT is a crucial node for the development of the primate vision, impacting both V1 and areas in the dorsal visual pathway known to mediate visually guided manual behaviours.TeaserThe early life loss of visual area MT leads to significant anatomical, physiological and behavioural changes.

scholarly journals When a Thought Equals a Look: Refreshing Enhances Perceptual Memory

2008 ◽  
Vol 20 (8) ◽  
pp. 1371-1380 ◽  
Author(s):  
Do-Joon Yi ◽  
Nicholas B. Turk-Browne ◽  
Marvin M. Chun ◽  
Marcia K. Johnson
Keyword(s):  
Visual Cortex ◽  
Temporal Cortex ◽  
Sensory Stimulation ◽  
Category Judgment ◽  
Inferior Temporal Cortex ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Top Down ◽  
Perceptual Representations ◽  
High Level

Cognition constantly involves retrieving and maintaining information that is not perceptually available in the current environment. Studies on visual imagery and working memory suggest that such high-level cognition might, in part, be mediated by the revival of perceptual representations in the inferior temporal cortex. Here, we provide new support for this hypothesis, showing that reflectively accessed information can have similar consequences for subsequent perception as actual perceptual input. Participants were presented with pairs of frames in which a scene could appear, and were required to make a category judgment on the second frame. In the critical condition, a scene was presented in the first frame, but the second frame was blank. Thus, it was necessary to refresh the scene from the first frame in order to make the category judgment. Scenes were then repeated in subsequent trials to measure the effect of refreshing on functional magnetic resonance imaging repetition attenuation—a neural index of memory—in a scene-selective region of the visual cortex. Surprisingly, the refreshed scenes produced equal attenuation as scenes that had been presented twice during encoding, and more attenuation than scenes that had been presented once during encoding, but that were not refreshed. Thus, the top-down revival of a percept had a similar effect on memory as actually seeing the stimulus again. These findings indicate that high-level cognition can activate stimulus-specific representations in the ventral visual cortex, and that such top-down activation, like that from sensory stimulation, produces memorial changes that affect perceptual processing during a later encounter with the stimulus.

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