scholarly journals Improved correspondence of fMRI visual field localizer data after macroanatomical alignment

2021 ◽  
Author(s):  
Mishal Qubad ◽  
Catherine Victoria Barnes-Scheufler ◽  
Michael Schaum ◽  
Eva Raspor ◽  
Lara Roesler ◽  
...  
Keyword(s):  
Visual Field ◽  
Visual System ◽  
Interindividual Variability ◽  
Human Cognition ◽  
Spatial Consistency ◽  
Visual Hemifield ◽  
Visual Areas ◽  
Homologous Part ◽  
Potential Benefits ◽  
Health And Disease

The study of the visual system and its role for human cognition in health and disease with fMRI often requires the use of localizer paradigms to define anatomical regions of interest (ROIs). However, the considerable degree of interindividual variability of the cerebral cortex represents an important confound, especially when analyzing visual localizer data on the group level. Cortex-based alignment (CBA) techniques lead to a reliable reduction of interindividual anatomical variability. Yet, the potential benefits of CBA has not been investigated for visual field localizer paradigms used to map specific parts of the visual field within retinotopically organized early visual areas. We evaluated CBA for an attention-enhanced visual field localizer mapping a homologous part of each visual quadrant in a cohort of 50 participants. After CBA, group ROIs showed markedly increased spatial consistency. CBA also led to an increase in the probability of activation overlap of up to forty percent. Furthermore, the size of group ROIs for the lower visual hemifield was larger than for the upper visual hemifield after CBA. This asymmetry, which mirrors previous findings from electrophysiological and fMRI studies, was not detectable before CBA. Our results confirm and extend the utility of CBA for the study of the visual system particularly in the context of group analyses. This method should be particularly important for the study of neuropsychiatric disorders with abnormally increased interindividual anatomical variability.

Blindsight Mediated by an S-Cone-independent Collicular Pathway: An fMRI Study in Hemispherectomized Subjects

2010 ◽  
Vol 22 (4) ◽  
pp. 670-682 ◽  
Author(s):  
Sandra E. Leh ◽  
Alain Ptito ◽  
Marc Schönwiesner ◽  
Mallar M. Chakravarty ◽  
Kathy T. Mullen
Keyword(s):  
Visual Field ◽  
Superior Colliculus ◽  
Control Subject ◽  
Short Wavelength ◽  
Visual Stimuli ◽  
Stimulus Presentation ◽  
Cortical Activation ◽  
Visual Hemifield ◽  
Visual Areas ◽  
The Subject

The purpose of our study was to investigate the ability to process achromatic and short-wavelength-sensitive cone (S-cone)-isolating (blue–yellow) stimuli in the blind visual field of hemispherectomized subjects and to demonstrate that blindsight is mediated by a collicular pathway that is independent of S-cone inputs. Blindsight has been described as the ability to respond to visual stimuli in the blind visual field without conscious awareness [Weiskrantz, L., Warrington, E. K., Sanders, M. D., & Marshall, J. Visual capacity in the hemianopic field following a restricted occipital ablation. Brain, 97, 709–728, 1974]. The roles of the subcortical neural structures in blindsight, such as the pulvinar and the superior colliculus, have been debated and an underlying neural correlate has yet to be confirmed. Using fMRI, we tested the ability to process visual stimuli that isolated the achromatic and short-wavelength-sensitive (S-)-cone pathways in three subjects: one control subject, one hemispherectomized subject with blindsight, and one hemispherectomized subject without blindsight. We demonstrated that (1) achromatic and S-cone-isolating stimuli presented to the normal visual hemifield of hemispherectomized subjects and to both visual hemifields of the control subject activated contralateral visual areas (V1/V2), as expected; (2) achromatic stimulus presentation but not S-cone-isolating stimulus presentation to the blind hemifield of the subject with blindsight activated visual areas FEF/V5; (3) whereas the cortical activation of the control subject was enhanced by an additional stimulus (achromatic and S-cone isolating) presented in the contralateral visual field, activation pattern of the subject with blindsight was enhanced by achromatic stimuli only. We conclude that the human superior colliculus is blind to the S-cone-isolating stimuli, and blindsight is mediated by an S-cone-independent collicular pathway.

scholarly journals Myelin densities in retinotopically defined dorsal visual areas of the macaque

2021 ◽  
Author(s):  
Xiaolian Li ◽  
Qi Zhu ◽  
Wim Vanduffel
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Cortical Thickness ◽  
New World Monkeys ◽  
Isotropic Resolution ◽  
Density Mapping ◽  
Area V2 ◽  
Visual Areas ◽  
Density Results

AbstractThe visuotopic organization of dorsal visual cortex rostral to area V2 in primates has been a longstanding source of controversy. Using sub-millimeter phase-encoded retinotopic fMRI mapping, we recently provided evidence for a surprisingly similar visuotopic organization in dorsal visual cortex of macaques compared to previously published maps in New world monkeys (Zhu and Vanduffel, Proc Natl Acad Sci USA 116:2306–2311, 2019). Although individual quadrant representations could be robustly delineated in that study, their grouping into hemifield representations remains a major challenge. Here, we combined in-vivo high-resolution myelin density mapping based on MR imaging (400 µm isotropic resolution) with fine-grained retinotopic fMRI to quantitatively compare myelin densities across retinotopically defined visual areas in macaques. Complementing previously documented differences in populational receptive-field (pRF) size and visual field signs, myelin densities of both quadrants of the dorsolateral posterior area (DLP) and area V3A are significantly different compared to dorsal and ventral area V3. Moreover, no differences in myelin density were observed between the two matching quadrants belonging to areas DLP, V3A, V1, V2 and V4, respectively. This was not the case, however, for the dorsal and ventral quadrants of area V3, which showed significant differences in MR-defined myelin densities, corroborating evidence of previous myelin staining studies. Interestingly, the pRF sizes and visual field signs of both quadrant representations in V3 are not different. Although myelin density correlates with curvature and anticorrelates with cortical thickness when measured across the entire cortex, exactly as in humans, the myelin density results in the visual areas cannot be explained by variability in cortical thickness and curvature between these areas. The present myelin density results largely support our previous model to group the two quadrants of DLP and V3A, rather than grouping DLP- with V3v into a single area VLP, or V3d with V3A+ into DM.

On Why Objects Appear Smaller in the Visual Periphery

2019 ◽  
Vol 31 (1) ◽  
pp. 88-96 ◽  
Author(s):  
Wladimir Kirsch ◽  
Roland Pfister ◽  
Wilfried Kunde
Keyword(s):  
Visual Field ◽  
Visual System ◽  
Structural Properties ◽  
Spatial Attention ◽  
Visuospatial Attention ◽  
Peripheral Target ◽  
Perceptual Distortion ◽  
Visual Periphery ◽  
Peripheral Location ◽  
Exogenous Cue

An object appears smaller in the periphery than in the center of the visual field. In two experiments ( N = 24), we demonstrated that visuospatial attention contributes substantially to this perceptual distortion. Participants judged the size of central and peripheral target objects after a transient, exogenous cue directed their attention to either the central or the peripheral location. Peripheral target objects were judged to be smaller following a central cue, whereas this effect disappeared completely when the peripheral target was cued. This outcome suggests that objects appear smaller in the visual periphery not only because of the structural properties of the visual system but also because of a lack of spatial attention.

An Evaluation of the Acceptability of Smart Eyewear for Plot Diagnosis Activity in Agriculture

2021 ◽  
pp. 106480462110185
Author(s):  
Jean Larbaigt ◽  
Céline Lemercier
Keyword(s):  
Visual Field ◽  
User Experience ◽  
Subjective Evaluations ◽  
Smart Glasses ◽  
Potential Benefits

Smart glasses could meet the plot diagnosis activity needs in agriculture. Therefore, their acceptability must be evaluated. We conducted user tests with agricultural advisors to assess perceived comfort and user experience. The participants reported comfort issues like and harm problems, and obstruction or disturbance of the visual field. Objective and subjective evaluations were poorer when the device was used in voice mode compared with buttons. Despite these limitations, the participants mentioned the potential benefits of the device for plot diagnosis. Although promising, smart glasses do not yet meet the advisors’ constraints. We propose hardware and software recommendations.

scholarly journals Vision as oculomotor reward: cognitive contributions to the dynamic control of saccadic eye movements

2021 ◽  
Author(s):  
Christian Wolf ◽  
Markus Lappe
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Visual System ◽  
Dynamic Control ◽  
Saccadic Eye Movements ◽  
Saccade Target ◽  
Cognitive Mechanisms ◽  
Foveal Vision ◽  
Subsequent Behavior ◽  
High Level

AbstractHumans and other primates are equipped with a foveated visual system. As a consequence, we reorient our fovea to objects and targets in the visual field that are conspicuous or that we consider relevant or worth looking at. These reorientations are achieved by means of saccadic eye movements. Where we saccade to depends on various low-level factors such as a targets’ luminance but also crucially on high-level factors like the expected reward or a targets’ relevance for perception and subsequent behavior. Here, we review recent findings how the control of saccadic eye movements is influenced by higher-level cognitive processes. We first describe the pathways by which cognitive contributions can influence the neural oculomotor circuit. Second, we summarize what saccade parameters reveal about cognitive mechanisms, particularly saccade latencies, saccade kinematics and changes in saccade gain. Finally, we review findings on what renders a saccade target valuable, as reflected in oculomotor behavior. We emphasize that foveal vision of the target after the saccade can constitute an internal reward for the visual system and that this is reflected in oculomotor dynamics that serve to quickly and accurately provide detailed foveal vision of relevant targets in the visual field.

The visual system of a Palaeognathous bird: Visual field, retinal topography and retino-central connections in the Chilean Tinamou (Nothoprocta perdicaria)

2014 ◽  
Vol 523 (2) ◽  
pp. 226-250 ◽  
Author(s):  
Quirin Krabichler ◽  
Tomas Vega-Zuniga ◽  
Cristian Morales ◽  
Harald Luksch ◽  
Gonzalo J. Marín
Keyword(s):  
Visual Field ◽  
Visual System ◽  
Retinal Topography ◽  
Nothoprocta Perdicaria

Equal Degrees of Object Selectivity for Upper and Lower Visual Field Stimuli

2010 ◽  
Vol 104 (4) ◽  
pp. 2075-2081 ◽  
Author(s):  
Lars Strother ◽  
Adrian Aldcroft ◽  
Cheryl Lavell ◽  
Tutis Vilis
Keyword(s):  
Visual Field ◽  
Occipital Cortex ◽  
Recognition System ◽  
Blood Oxygen Level Dependent ◽  
Lower Visual Field ◽  
Blood Oxygen Level ◽  
Visual Areas ◽  
Bold Responses ◽  
Cortical Regions ◽  
Lateral Occipital Cortex

Functional MRI (fMRI) studies of the human object recognition system commonly identify object-selective cortical regions by comparing blood oxygen level–dependent (BOLD) responses to objects versus those to scrambled objects. Object selectivity distinguishes human lateral occipital cortex (LO) from earlier visual areas. Recent studies suggest that, in addition to being object selective, LO is retinotopically organized; LO represents both object and location information. Although LO responses to objects have been shown to depend on location, it is not known whether responses to scrambled objects vary similarly. This is important because it would suggest that the degree of object selectivity in LO does not vary with retinal stimulus position. We used a conventional functional localizer to identify human visual area LO by comparing BOLD responses to objects versus scrambled objects presented to either the upper (UVF) or lower (LVF) visual field. In agreement with recent findings, we found evidence of position-dependent responses to objects. However, we observed the same degree of position dependence for scrambled objects and thus object selectivity did not differ for UVF and LVF stimuli. We conclude that, in terms of BOLD response, LO discriminates objects from non-objects equally well in either visual field location, despite stronger responses to objects in the LVF.

First order connections of the visual sector of the thalamic reticular nucleus in marmoset monkeys (Callithrix jacchus)

2007 ◽  
Vol 24 (6) ◽  
pp. 857-874 ◽  
Author(s):  
THOMAS FITZGIBBON ◽  
BRETT A. SZMAJDA ◽  
PAUL R. MARTIN
Keyword(s):  
Visual Field ◽  
Callithrix Jacchus ◽  
Higher Order ◽  
Dorsal Lateral Geniculate Nucleus ◽  
Thalamic Reticular Nucleus ◽  
Reticular Nucleus ◽  
Lower Visual Field ◽  
First Order ◽  
Cortical Areas ◽  
Visual Areas

The thalamic reticular nucleus (TRN) supplies an important inhibitory input to the dorsal thalamus. Previous studies in non-primate mammals have suggested that the visual sector of the TRN has a lateral division, which has connections with first-order (primary) sensory thalamic and cortical areas, and a medial division, which has connections with higher-order (association) thalamic and cortical areas. However, the question whether the primate TRN is segregated in the same manner is controversial. Here, we investigated the connections of the TRN in a New World primate, the marmoset (Callithrix jacchus). The topography of labeled cells and terminals was analyzed following iontophoretic injections of tracers into the primary visual cortex (V1) or the dorsal lateral geniculate nucleus (LGNd). The results show that rostroventral TRN, adjacent to the LGNd, is primarily connected with primary visual areas, while the most caudal parts of the TRN are associated with higher order visual thalamic areas. A small region of the TRN near the caudal pole of the LGNd (foveal representation) contains connections where first (lateral TRN) and higher order visual areas (medial TRN) overlap. Reciprocal connections between LGNd and TRN are topographically organized, so that a series of rostrocaudal injections within the LGNd labeled cells and terminals in the TRN in a pattern shaped like rostrocaudal overlapping “fish scales.” We propose that the dorsal areas of the TRN, adjacent to the top of the LGNd, represent the lower visual field (connected with medial LGNd), and the more ventral parts of the TRN contain a map representing the upper visual field (connected with lateral LGNd).

scholarly journals Unique spatial integration in mouse primary visual cortex and higher visual areas

2019 ◽  
Author(s):  
Kevin A. Murgas ◽  
Ashley M. Wilson ◽  
Valerie Michael ◽  
Lindsey L. Glickfeld
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Spatial Information ◽  
Spatial Scales ◽  
Spatial Integration ◽  
Global Features ◽  
Wide Range ◽  
Visual Areas ◽  
Higher Visual Areas

AbstractNeurons in the visual system integrate over a wide range of spatial scales. This diversity is thought to enable both local and global computations. To understand how spatial information is encoded across the mouse visual system, we use two-photon imaging to measure receptive fields in primary visual cortex (V1) and three downstream higher visual areas (HVAs): LM (lateromedial), AL (anterolateral) and PM (posteromedial). We find significantly larger receptive field sizes and less surround suppression in PM than in V1 or the other HVAs. Unlike other visual features studied in this system, specialization of spatial integration in PM cannot be explained by specific projections from V1 to the HVAs. Instead, our data suggests that distinct connectivity within PM may support the area’s unique ability to encode global features of the visual scene, whereas V1, LM and AL may be more specialized for processing local features.

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