Visual callosal connections: role in visual processing in health and disease

Bocci, Tommaso; Pietrasanta, Marta; Cerri, Chiara; Restani, Laura; Caleo, Matteo; Sartucci, Ferdinando

doi:10.1515/revneuro-2013-0025

Cited by 26 publications

(20 citation statements)

References 134 publications

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“…Callosal afferents are mostly excitatory (Bocci et al ., ) and therefore inhibitory interhemispheric interactions must occur via the recruitment of local GABAergic cells (Toyama et al ., ). The neurochemical phenotype of inhibitory cells mediating interhemispheric inhibition following MD remains to be established (see scheme in Fig.…”

Section: Discussionmentioning

confidence: 99%

A switch from inter‐ocular to inter‐hemispheric suppression following monocular deprivation in the rat visual cortex

Pietrasanta

Restani

Cerri

et al. 2014

Eur J of Neuroscience

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Binocularity is a key property of primary visual cortex (V1) neurons that is widely used to study synaptic integration in the brain and plastic mechanisms following an altered visual experience. However, it is not clear how the inputs from the two eyes converge onto binocular neurons, and how their interaction is modified by an unbalanced visual drive. Here, using visual evoked potentials recorded in the juvenile rat V1, we report evidence for a suppressive mechanism by which contralateral eye activity inhibits responses from the ipsilateral eye. Accordingly, we found a lack of additivity of the responses evoked independently by the two eyes in the V1, and acute silencing of the contralateral eye resulted in the enhancement of ipsilateral eye responses in cortical neurons. We reverted the relative cortical strength of the two eyes by suturing the contralateral eye shut [monocular deprivation (MD)]. After 7 days of MD, there was a loss of interocular suppression mediated by the contralateral, deprived eye, and weak inputs from the closed eye were functionally inhibited by interhemispheric callosal pathways. We conclude that interocular suppressive mechanisms play a crucial role in shaping normal binocularity in visual cortical neurons, and a switch from interocular to interhemispheric suppression represents a key step in the ocular dominance changes induced by MD. These data have important implications for a deeper understanding of the key mechanisms that underlie activity-dependent rearrangements of cortical circuits following alteration of sensory experience.

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Section: Discussionmentioning

confidence: 99%

A switch from inter‐ocular to inter‐hemispheric suppression following monocular deprivation in the rat visual cortex

Pietrasanta

Restani

Cerri

et al. 2014

Eur J of Neuroscience

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“…Callosal connections interlink homologous and non-homologous cortical areas situated in the two cerebral hemispheres (Lewis and Olavarria, 1995; Funnell et al, 2000; Houzel et al, 2002; Bocci et al, 2014). …”

Section: The Corpus Callosum: Anatomical and Physiological Frameworkmentioning

confidence: 99%

“…It is well established that the CC provides both excitatory and inhibitory input to visual cortex (Makarov et al, 2008; for specific reviews, see Bloom and Hynd, 2005; Bocci et al, 2014; see also Figure 1A). For example, cooling or GABA injections in one hemisphere decrease cell responsiveness in a subset of contralateral neurons, suggesting transcallosal excitatory drive to these neurons (Payne et al, 1991; Sun et al, 1994).…”

Section: The Corpus Callosum: Anatomical and Physiological Frameworkmentioning

confidence: 99%

Reorganization of Visual Callosal Connections Following Alterations of Retinal Input and Brain Damage

Restani

Caleo

2016

Front. Syst. Neurosci.

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Vision is a very important sensory modality in humans. Visual disorders are numerous and arising from diverse and complex causes. Deficits in visual function are highly disabling from a social point of view and in addition cause a considerable economic burden. For all these reasons there is an intense effort by the scientific community to gather knowledge on visual deficit mechanisms and to find possible new strategies for recovery and treatment. In this review, we focus on an important and sometimes neglected player of the visual function, the corpus callosum (CC). The CC is the major white matter structure in the brain and is involved in information processing between the two hemispheres. In particular, visual callosal connections interconnect homologous areas of visual cortices, binding together the two halves of the visual field. This interhemispheric communication plays a significant role in visual cortical output. Here, we will first review the essential literature on the physiology of the callosal connections in normal vision. The available data support the view that the callosum contributes to both excitation and inhibition to the target hemisphere, with a dynamic adaptation to the strength of the incoming visual input. Next, we will focus on data showing how callosal connections may sense visual alterations and respond to the classical paradigm for the study of visual plasticity, i.e., monocular deprivation (MD). This is a prototypical example of a model for the study of callosal plasticity in pathological conditions (e.g., strabismus and amblyopia) characterized by unbalanced input from the two eyes. We will also discuss the findings of callosal alterations in blind subjects. Noteworthy, we will discuss data showing that inter-hemispheric transfer mediates recovery of visual responsiveness following cortical damage. Finally, we will provide an overview of how callosal projections dysfunction could contribute to pathologies such as neglect and occipital epilepsy. A particular focus will be on reviewing noninvasive brain stimulation techniques and optogenetic approaches that allow to selectively manipulate callosal function and to probe its involvement in cortical processing and plasticity. Overall, the data indicate that experience can potently impact on transcallosal connectivity, and that the callosum itself is crucial for plasticity and recovery in various disorders of the visual pathway.

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“…Recent in-vivo studies in humans using diffusionweighted imaging techniques focused on the topography of callosal connections of different early visual areas within the splenium of the corpus callosum Putnam et al, 2009) or of different parts of area V1 (Saenz & Fine, 2010). Saenz and Fine (2010) were also able to show that the majority of transcallosal fibers of V1 (about ¾) did not reach the core of V1, but ended in zones around the border of V1 and adjacent cortex (Bocci et al, 2014). Placing the seed directly into the splenium of the corpus callosum, we were able to demonstrate that these splenial transcallosal fibers do not only cover the V1/V2 border.…”

Section: Transcallosal Fiber Organization In Human Brains and Their Cmentioning

confidence: 99%

Target sites for transcallosal fibers in human visual cortex – A combined diffusion and polarized light imaging study

Caspers

Axer

Caspers

et al. 2015

Cortex

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Visual callosal connections: role in visual processing in health and disease

Cited by 26 publications

References 134 publications

A switch from inter‐ocular to inter‐hemispheric suppression following monocular deprivation in the rat visual cortex

A switch from inter‐ocular to inter‐hemispheric suppression following monocular deprivation in the rat visual cortex

Reorganization of Visual Callosal Connections Following Alterations of Retinal Input and Brain Damage

Target sites for transcallosal fibers in human visual cortex – A combined diffusion and polarized light imaging study

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