scholarly journals Population receptive field and connectivity properties of the early visual cortex in human albinism

2019 ◽  
Author(s):  
Khazar Ahmadi ◽  
Anne Herbik ◽  
Markus Wagner ◽  
Martin Kanowski ◽  
Hagen Thieme ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Optic Chiasm ◽  
List Type ◽  
Cortical Connectivity ◽  
Cortical Connections ◽  
Visual Hemifield ◽  
Early Visual Cortex ◽  
Visual Hemifields ◽  
Retinal Afferents

AbstractIn albinism, the pathological decussation of the temporal retinal afferents at the optic chiasm leads to superimposed representations of opposing hemifields in the visual cortex. Here, we assessed the equivalence of the two representations and the cortico-cortical connectivity of the early visual areas. Applying fMRI-based population receptive field (pRF)-mapping (both hemifield and bilateral mapping) and connective field (CF)-modeling, we investigated the early visual cortex in 6 albinotic participants and 4 controls. In albinism, superimposed retinotopic representations of the contra- and ipsilateral visual hemifield were observed on the hemisphere contralateral to the stimulated eye. This was confirmed by the observation of bilateral pRFs during bilateral mapping. Hemifield mapping revealed similar pRF-sizes for both hemifield representations throughout V1 to V3. The typical increase of V1-sampling extent for V3 compared to V2 was not found for the albinotic participants. The similarity of the pRF-sizes for opposing visual hemifield representations highlights the equivalence of the two maps in the early visual cortex. The altered V1-sampling extent in V3 indicates the adaptation of cortico-cortical connections to the abnormal input of the visual cortex. These findings thus suggest that conservative developmental mechanisms are complemented by alterations of the extrastriate cortico-cortical connectivity.HighlightspRF mapping confirms cortical overlay of opposing visual hemifields in albinism.Equivalent information processing of both hemifields is indicated by similar pRF sizes.CF modeling indicates changes to the cortico-cortical connections at the level of V3.

scholarly journals Triple visual hemifield maps in optic chiasm hypoplasia

2019 ◽  
Author(s):  
Khazar Ahmadi ◽  
Alessio Fracasso ◽  
Robert J. Puzniak ◽  
Andre D. Gouws ◽  
Renat Yakupov ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Receptive Field ◽  
Diffusion Weighted Imaging ◽  
Developmental Plasticity ◽  
Daily Life ◽  
Optic Chiasm ◽  
Integrative Approach ◽  
Cortical Connections ◽  
Visual Hemifield

AbstractIn humans, each hemisphere comprises an overlay of two visuotopic maps of the contralateral visual field, one from each eye. Is the capacity of the visual cortex limited to these two maps or are plastic mechanisms available to host more maps? Using an integrative approach of submillimeter fMRI, diffusion-weighted imaging and population receptive field mapping, we found three hemiretinal inputs to converge onto the left hemisphere in a rare individual with chiasma hypoplasia. This generates extremely atypical responses in striate and extrastriate cortices, specifically an overlay of three hemifield representations. Unexpectedly, the effects of this large abnormality on visual function in daily life are not easily detected. We conclude that developmental plasticity including the re-wiring of local intra- and cortico-cortical connections is pivotal to support the coexistence and functioning of three hemifield maps within one hemisphere.

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 Depth-resolved ultra-high field fMRI reveals feedback contributions to surface motion perception

2019 ◽  
Author(s):  
Ingo Marquardt ◽  
Peter De Weerd ◽  
Marian Schneider ◽  
Omer Faruk Gulban ◽  
Dimo Ivanov ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Motion Perception ◽  
High Field ◽  
Depth Distribution ◽  
Middle Layer ◽  
Bold Response ◽  
Ultra High Field ◽  
Surface Motion ◽  
Visual Hemifield ◽  
Early Visual Cortex

AbstractHuman visual surface perception has neural correlates in early visual cortex, but the extent to which feedback contributes to this activity is not well known. Feedback projections preferentially enter superficial and deep anatomical layers, while avoiding the middle layer, which provides a hypothesis for the cortical depth distribution of fMRI activity related to feedback in early visual cortex. Here, we presented human participants uniform surfaces on a dark, textured background. The grey surface in the left hemifield was either perceived as static or moving based on a manipulation in the right hemifield. Physically, the surface was identical in the left visual hemifield, so any difference in percept likely was related to feedback. Using ultra-high field fMRI, we report the first evidence for a depth distribution of activation in line with feedback during the (illusory) perception of surface motion. Our results fit with a signal re-entering in superficial depths of V1, followed by a feedforward sweep of the re-entered information through V2 and V3, as suggested by activity centred in the middle-depth levels of the latter areas. This positive modulation of the BOLD signal due to illusory surface motion was on top of a strong negative BOLD response in the cortical representation of the surface stimuli, which depended on the presence of texture in the background. Hence, the magnitude and sign of the BOLD response to the surface strongly depended on background properties, and was additionally modulated by the presence or absence of illusory motion perception in a manner compatible with feedback. In summary, the present study demonstrates the potential of depth resolved fMRI in tackling biomechanical questions on perception that so far were only within reach of invasive animal experimentation.

Neuropeptide Y-Containing Neurons are Situated Predominantly Outside Cytochrome Oxidase Puffs in Macaque Visual Cortex

1989 ◽  
Vol 2 (1) ◽  
pp. 57-62 ◽  
Author(s):  
Rodrigo O. Kuljis ◽  
Pasko Rakic
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Neuropeptide Y ◽  
Cytochrome Oxidase ◽  
Primary Visual Cortex ◽  
Spatial Relationship ◽  
Regular Pattern ◽  
Cortical Connectivity ◽  
Local Circuit ◽  
Immunocytochemical Method

AbstractLayers II/III of the primary visual cortex contain a regular pattern of histochemically detectable cytochrome oxidase (CO)-rich “puffs,” which differ from the interpuff regions in their thalamo-cortical and cortico-cortical connectivity, receptive-field properties, and the density of inhibitory GABA-containing synaptic terminals. We used an immunocytochemical method, in combination with cytochrome oxidase histochemistry, to analyze the spatial relationship between neurons that contain neuropeptide Y (NPY) and the CO puffs. Of a total of 606 neurons, only 2.6% of the NPY-containing cells are located in the puffs, whereas the rest are situated in the interpuffs, or at the interface between puffs and interpuffs. The number of NPY-containing neurons in the puffs is substantially less than that expected in an equal volume of the interpuffs (X2 = 13.86; df = 1; P < 0.001).These observations indicate that columns containing the puffs may differ also from those in the interpuff regions in that they contain a unique array of chemically and morphologically distinct local circuit neurons.

Competitive Interactions of Attentional Resources in Early Visual Cortex during Sustained Visuospatial Attention within or between Visual Hemifields: Evidence for the Different-hemifield Advantage

2014 ◽  
Vol 26 (5) ◽  
pp. 938-954 ◽  
Author(s):  
Sabrina Walter ◽  
Cliodhna Quigley ◽  
Matthias M. Mueller
Keyword(s):  
Visual Cortex ◽  
Visuospatial Attention ◽  
Competitive Interactions ◽  
Attentional Processing ◽  
Light Emitting ◽  
Attentional Resources ◽  
Early Visual Cortex ◽  
Processing Resources ◽  
Left And Right ◽  
Visual Hemifields

Performing a task across the left and right visual hemifields results in better performance than in a within-hemifield version of the task, termed the different-hemifield advantage. Although recent studies used transient stimuli that were presented with long ISIs, here we used a continuous objective electrophysiological (EEG) measure of competitive interactions for attentional processing resources in early visual cortex, the steady-state visual evoked potential (SSVEP). We frequency-tagged locations in each visual quadrant and at central fixation by flickering light-emitting diodes (LEDs) at different frequencies to elicit distinguishable SSVEPs. Stimuli were presented for several seconds, and participants were cued to attend to two LEDs either in one (Within) or distributed across left and right visual hemifields (Across). In addition, we introduced two reference measures: one for suppressive interactions between the peripheral LEDs by using a task at fixation where attention was withdrawn from the periphery and another estimating the upper bound of SSVEP amplitude by cueing participants to attend to only one of the peripheral LEDs. We found significantly greater SSVEP amplitude modulations in Across compared with Within hemifield conditions. No differences were found between SSVEP amplitudes elicited by the peripheral LEDs when participants attended to the centrally located LEDs compared with when peripheral LEDs had to be ignored in Across and Within trials. Attending to only one LED elicited the same SSVEP amplitude as Across conditions. Although behavioral data displayed a more complex pattern, SSVEP amplitudes were well in line with the predictions of the different-hemifield advantage account during sustained visuospatial attention.

scholarly journals Simultaneous development and periodic clustering of simple and complex cells in visual cortex

2019 ◽  
Author(s):  
Gwangsu Kim ◽  
Jaeson Jang ◽  
Se-Bum Paik
Keyword(s):  
Visual Cortex ◽  
Periodic Variation ◽  
Orientation Tuning ◽  
List Type ◽  
Simple Complex ◽  
Single Class ◽  
Complex Cells ◽  
Orientation Maps ◽  
Simple And Complex Cells ◽  
Retinal Afferents

AbstractNeurons in the primary visual cortex (V1) are often classified as simple or complex cells, but it is debated whether they are discrete hierarchical classes of neurons developing sequentially, or if they represent a continuum of variation within a single class of cells developing simultaneously. Herein, we show that simple and complex cells may arise simultaneously from the universal process of retinal development. From analysis of the cortical receptive fields in cats, we show evidence that simple and complex cells originate from the periodic variation of ON-OFF segregation in the feedforward projection of retinal mosaics, by which they organize into periodic clusters in V1. Our key prediction that clusters of simple and complex cells correlate topographically with orientation maps was confirmed by data in cats. Our results suggest that simple and complex cells are not two distinct neural populations but arise from common retinal afferents, simultaneous with orientation tuning.HighlightsSimple and complex cells arise simultaneously from retinal afferents.Simple/complex cells are organized into periodic clusters across visual cortex.Simple/complex clusters are topographically correlated with orientation maps.Development of clustered cells in V1 is explained by the Paik-Ringach model.

scholarly journals Radial asymmetries in population receptive field size and cortical magnification factor in early visual cortex

2017 ◽  
Vol 17 (10) ◽  
pp. 587
Author(s):  
Ben Harvey ◽  
Jan Brascamp ◽  
Sónia Ferreira ◽  
Miguel Castelo-Branco ◽  
Serge Dumoulin ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Field Size ◽  
Magnification Factor ◽  
Receptive Field Size ◽  
Early Visual Cortex ◽  
Cortical Magnification ◽  
Cortical Magnification Factor

scholarly journals Visual working memory representations in visual and parietal cortex do not remap after eye movements

2019 ◽  
Author(s):  
Tao He ◽  
Matthias Ekman ◽  
Annelinde R.E. Vandenbroucke ◽  
Floris P. de Lange
Keyword(s):  
Working Memory ◽  
Visual Cortex ◽  
Eye Movements ◽  
Visual Field ◽  
Visual System ◽  
Visual Working Memory ◽  
Parietal Cortex ◽  
List Type ◽  
Early Visual Cortex

ABSTRACTIt has been suggested that our visual system does not only process stimuli that are directly available to our eyes, but also has a role in maintaining information in VWM over a period of seconds. It remains unclear however what happens to VWM representations in the visual system when we make saccades. Here, we tested the hypothesis that VWM representations are remapped within the visual system after making saccades. We directly compared the content of VWM for saccade and no-saccade conditions using MVPA of delay-related activity measured with fMRI. We found that when participants did not make a saccade, VWM representations were robustly present in contralateral early visual cortex. When making a saccade, VWM representations degraded in contralateral V1-V3 after the saccade shifted the location of the remembered grating to the opposite visual field. However, contrary to our hypothesis we found no evidence for the representations of the remembered grating at the saccadic target location in the opposite visual field, suggesting that there is no evidence for remapping of VWM in early visual cortex. Interestingly, IPS showed persistent VWM representations in both the saccade and no-saccade condition. Together, our results indicate that VWM representations in early visual cortex are not remapped across eye movements, potentially limiting the role of early visual cortex in VWM storage.HighlightsVisual working memory (VWM) representations do not remap after making saccadesEye movement degrade VWM representations in early visual cortex, limiting the role of early visual cortex in VWM storageParietal cortex shows persistent VWM representations across saccades

scholarly journals Population receptive field and connectivity properties of the early visual cortex in human albinism

NeuroImage ◽  
2019 ◽  
Vol 202 ◽  
pp. 116105 ◽  
Author(s):  
Khazar Ahmadi ◽  
Anne Herbik ◽  
Markus Wagner ◽  
Martin Kanowski ◽  
Hagen Thieme ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Early Visual Cortex
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