Visual Interhemispheric and Striate-Extrastriate Cortical Connections in the Rabbit: A Multiple Tracer Study

Previous studies in rabbits identified an array of extrastriate cortical areas anatomically connected with V1 but did not describe their internal topography. To address this issue, we injected multiple anatomical tracers into different regions in V1 of the same animal and analyzed the topography of resulting extrastriate labeled fields with reference to the patterns of callosal connections and myeloarchitecture revealed in tangential sections of the flattened cortex. Our results extend previous studies and provide further evidence that rabbit extrastriate areas resemble the visual areas in rats and mice not only in their general location with respect to V1 but also in their internal topography. Moreover, extrastriate areas in the rabbit maintain a constant relationship with myeloarchitectonic borders and features of the callosal pattern. These findings highlight the rabbit as an alternative model to rats and mice for advancing our understanding of cortical visual processing in mammals, especially for projects benefiting from a larger brain.

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Mapping Short Association Fibers in the Early Cortical Visual Processing Stream Using In Vivo Diffusion Tractography

Cerebral Cortex ◽

10.1093/cercor/bhaa049 ◽

2020 ◽

Vol 30 (8) ◽

pp. 4496-4514 ◽

Cited By ~ 5

Author(s):

Fakhereh Movahedian Attar ◽

Evgeniya Kirilina ◽

Daniel Haenelt ◽

Kerrin J Pine ◽

Robert Trampel ◽

...

Keyword(s):

Human Brain ◽

Visual Processing ◽

Repeated Measurements ◽

Fiber Tractography ◽

Cortical Areas ◽

Brain Connectome ◽

Cortical Visual Processing ◽

Association Fibers ◽

Fiber Connectivity

Abstract Short association fibers (U-fibers) connect proximal cortical areas and constitute the majority of white matter connections in the human brain. U-fibers play an important role in brain development, function, and pathology but are underrepresented in current descriptions of the human brain connectome, primarily due to methodological challenges in diffusion magnetic resonance imaging (dMRI) of these fibers. High spatial resolution and dedicated fiber and tractography models are required to reliably map the U-fibers. Moreover, limited quantitative knowledge of their geometry and distribution makes validation of U-fiber tractography challenging. Submillimeter resolution diffusion MRI—facilitated by a cutting-edge MRI scanner with 300 mT/m maximum gradient amplitude—was used to map U-fiber connectivity between primary and secondary visual cortical areas (V1 and V2, respectively) in vivo. V1 and V2 retinotopic maps were obtained using functional MRI at 7T. The mapped V1–V2 connectivity was retinotopically organized, demonstrating higher connectivity for retinotopically corresponding areas in V1 and V2 as expected. The results were highly reproducible, as demonstrated by repeated measurements in the same participants and by an independent replication group study. This study demonstrates a robust U-fiber connectivity mapping in vivo and is an important step toward construction of a more complete human brain connectome.

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Visual Stimulus–Dependent Changes in Interhemispheric EEG Coherence in Ferrets

Journal of Neurophysiology ◽

10.1152/jn.1999.82.6.3082 ◽

1999 ◽

Vol 82 (6) ◽

pp. 3082-3094 ◽

Cited By ~ 42

Author(s):

D. C. Kiper ◽

M. G. Knyazeva ◽

L. Tettoni ◽

G. M. Innocenti

Keyword(s):

Visual Field ◽

Corpus Callosum ◽

Experimental Validation ◽

Visual Stimulation ◽

Eeg Coherence ◽

Vertical Meridian ◽

Callosal Connections ◽

Interhemispheric Coherence ◽

Cortical Connections ◽

Visual Areas

In recent years, the analysis of the coherence between signals recorded from the scalp [electroencephalographic (EEG) coherence] has been used to assess the functional properties of cortico-cortical connections, both in animal models and in humans. However, the experimental validation of this technique is still scarce. Therefore we applied it to the study of the callosal connections between the visual areas of the two hemispheres, because this particular set of cortico-cortical connections can be activated in a selective way by visual stimuli. Indeed, in primary and in low-order secondary visual areas, callosal axons interconnect selectively regions, which represent a narrow portion of the visual field straddling the vertical meridian and, within these regions, neurons that prefer the same stimulus orientation. Thus only isooriented stimuli located near the vertical meridian are expected to change interhemispheric coherence by activating callosal connections. Finally, if such changes are found and are indeed mediated by callosal connections, they should disappear after transection of the corpus callosum. We perfomed experiments on seven paralyzed and anesthetized ferrets, recording their cortical activity with epidural electrodes on areas 17/18, 19, and lateral suprasylvian, during different forms of visual stimulation. As expected, we found that bilateral iso-oriented stimuli near the vertical meridian, or extending across it, caused a significant increase in interhemispheric coherence in the EEG beta-gamma band. Stimuli with different orientations, stimuli located far from the vertical meridian, as well as unilateral stimuli failed to affect interhemispheric EEG coherence. The stimulus-induced increase in coherence disappeared after surgical transection of the corpus callosum. The results suggest that the activation of cortico-cortical connections can indeed be revealed as a change in EEG coherence. The latter can therefore be validly used to investigate the functionality of cortico-cortical connections.

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Hierarchical Organization of Corticothalamic Projections to the Pulvinar

Cerebral Cortex Communications ◽

10.1093/texcom/tgaa030 ◽

2020 ◽

Vol 1 (1) ◽

Cited By ~ 1

Author(s):

Reza Abbas Farishta ◽

Denis Boire ◽

Christian Casanova

Keyword(s):

Higher Order ◽

Hierarchical Organization ◽

Hierarchical Level ◽

Thalamic Nuclei ◽

Cortical Areas ◽

Visual Areas ◽

Cortical Hierarchy ◽

Area 21A ◽

Extrastriate Areas ◽

Corticothalamic Projections

Abstract Signals from lower cortical visual areas travel to higher-order areas for further processing through cortico-cortical projections, organized in a hierarchical manner. These signals can also be transferred between cortical areas via alternative cortical transthalamic routes involving higher-order thalamic nuclei like the pulvinar. It is unknown whether the organization of transthalamic pathways may reflect the cortical hierarchy. Two axon terminal types have been identified in corticothalamic (CT) pathways: the types I (modulators) and II (drivers) characterized by thin axons with small terminals and by thick axons and large terminals, respectively. In cats, projections from V1 to the pulvinar complex comprise mainly type II terminals, whereas those from extrastriate areas include a combination of both terminals suggesting that the nature of CT terminals varies with the hierarchical order of visual areas. To test this hypothesis, distribution of CT terminals from area 21a was charted and compared with 3 other visual areas located at different hierarchical levels. Results demonstrate that the proportion of modulatory CT inputs increases along the hierarchical level of cortical areas. This organization of transthalamic pathways reflecting cortical hierarchy provides new and fundamental insights for the establishment of more accurate models of cortical signal processing along transthalamic cortical pathways.

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Distinct recruitment of feed-forward and recurrent pathways across higher-order areas of mouse visual cortex

10.1101/2020.09.24.312140 ◽

2020 ◽

Author(s):

Jennifer Y. Li ◽

Charles A. Hass ◽

Ian Matthews ◽

Amy C. Kristl ◽

Lindsey L. Glickfeld

Keyword(s):

Visual Processing ◽

Higher Order ◽

Feed Forward ◽

Cortical Areas ◽

Physiological Properties ◽

Cortical Visual Processing ◽

Visual Cortical ◽

Mouse Visual Cortex ◽

Whole Cell Recordings

AbstractCortical visual processing transforms features of the external world into increasingly complex and specialized neuronal representations. These transformations arise in part through target-specific routing of information; however, within-area computations may also contribute to area-specific function. Here, we sought to determine whether higher-order visual cortical areas LM, AL, PM, and AM have specialized anatomical and physiological properties by using a combination of whole-cell recordings and optogenetic stimulation of V1 axons in vitro. We discovered area-specific differences in the strength of recruitment of interneurons through feed-forward and recurrent pathways, as well as differences in cell-intrinsic properties and interneuron densities. These differences were most striking when comparing across medial and lateral areas, suggesting that these areas have distinct profiles for net excitability and integration of V1 inputs. Thus, cortical areas are not defined simply by the information they receive, but also by area-specific circuit properties that enable specialized filtering of these inputs.

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Cortical visual processing

Electroencephalography and Clinical Neurophysiology ◽

10.1016/s0013-4694(97)87994-5 ◽

1997 ◽

Vol 103 (1) ◽

pp. 20

Author(s):

G Celesia

Keyword(s):

Visual Processing ◽

Cortical Visual Processing

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Visuopathy of prematurity: is retinopathy just the tip of the iceberg?

Pediatric Research ◽

10.1038/s41390-021-01625-0 ◽

2021 ◽

Author(s):

Sigrid Hegna Ingvaldsen ◽

Tora Sund Morken ◽

Dordi Austeng ◽

Olaf Dammann

Keyword(s):

Visual Processing ◽

Structural Changes ◽

Developmental Trajectories ◽

Visual Pathway ◽

Visual Stream ◽

Visual Deficits ◽

Cortical Areas ◽

Cellular Architecture ◽

Increased Risk ◽

Dorsal Visual Stream

AbstractResearch on retinopathy of prematurity (ROP) focuses mainly on the abnormal vascularization patterns that are directly visible for ophthalmologists. However, recent findings indicate that children born prematurely also exhibit changes in the retinal cellular architecture and along the dorsal visual stream, such as structural changes between and within cortical areas. Moreover, perinatal sustained systemic inflammation (SSI) is associated with an increased risk for ROP and the visual deficits that follow. In this paper, we propose that ROP might just be the tip of an iceberg we call visuopathy of prematurity (VOP). The VOP paradigm comprises abnormal vascularization of the retina, alterations in retinal cellular architecture, choroidal degeneration, and abnormalities in the visual pathway, including cortical areas. Furthermore, VOP itself might influence the developmental trajectories of cerebral structures and functions deemed responsible for visual processing, thereby explaining visual deficits among children born preterm.

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Sustained Splits of Attention within versus across Visual Hemifields Produce Distinct Spatial Gain Profiles

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_00883 ◽

2016 ◽

Vol 28 (1) ◽

pp. 111-124 ◽

Cited By ~ 4

Author(s):

Sabrina Walter ◽

Christian Keitel ◽

Matthias M. Müller

Keyword(s):

Visual Attention ◽

Visual Processing ◽

Behavioral Performance ◽

Lower Visual Field ◽

Light Emitting ◽

Visual Hemifield ◽

Attention Tasks ◽

Visual Cortices ◽

Cortical Visual Processing ◽

Visual Hemifields

Visual attention can be focused concurrently on two stimuli at noncontiguous locations while intermediate stimuli remain ignored. Nevertheless, behavioral performance in multifocal attention tasks falters when attended stimuli fall within one visual hemifield as opposed to when they are distributed across left and right hemifields. This “different-hemifield advantage” has been ascribed to largely independent processing capacities of each cerebral hemisphere in early visual cortices. Here, we investigated how this advantage influences the sustained division of spatial attention. We presented six isoeccentric light-emitting diodes (LEDs) in the lower visual field, each flickering at a different frequency. Participants attended to two LEDs that were spatially separated by an intermediate LED and responded to synchronous events at to-be-attended LEDs. Task-relevant pairs of LEDs were either located in the same hemifield (“within-hemifield” conditions) or separated by the vertical meridian (“across-hemifield” conditions). Flicker-driven brain oscillations, steady-state visual evoked potentials (SSVEPs), indexed the allocation of attention to individual LEDs. Both behavioral performance and SSVEPs indicated enhanced processing of attended LED pairs during “across-hemifield” relative to “within-hemifield” conditions. Moreover, SSVEPs demonstrated effective filtering of intermediate stimuli in “across-hemifield” condition only. Thus, despite identical physical distances between LEDs of attended pairs, the spatial profiles of gain effects differed profoundly between “across-hemifield” and “within-hemifield” conditions. These findings corroborate that early cortical visual processing stages rely on hemisphere-specific processing capacities and highlight their limiting role in the concurrent allocation of visual attention to multiple locations.

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

Visual Neuroscience ◽

10.1017/s0952523807070770 ◽

2007 ◽

Vol 24 (6) ◽

pp. 857-874 ◽

Cited By ~ 11

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).

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