Bonn, April 20, 2020. A new
study by caesar scientists, from the department “Behavior and Brain
Organization”, led by director Prof. Dr. Jason Kerr, sheds new light on
the visual callosal pathway (VCP) and its processing of visual stimuli.
The study has now been published by Nature Communications (https://doi.org/10.1038/s41467-020-15672-4).
The visual system is tasked with the processing of visual stimuli. It includes the eye with the retina, the optic nerve, parts of the thalamus and the brain stem, as well as the visual cortex. Each hemisphere of the brain has a visual thalamus and a visual cortex. These systems work in an interconnected fashion. Most of the information from the retina of the left eye is processed in the right hemisphere, and vice versa. The remainder of the information does not cross over to the other side of the brain, but is routed to the visual thalamus and visual cortex within the same hemisphere.
Among the tasks of the brain is combining the information from these pathways into a coherent representation of the environment surrounding an animal. The corpus callosum, or callosal commissure, connects both hemispheres for this purpose. In the right occipital lobe, the visual information from the left eye is processed, and vice versa. A part of the corpus callosum – the visual callosal pathway (VCP) – serves the exchange for visual information between hemispheres.
However, when caesar researcher studied the VCP in rats, a much more complex web of communication than previously assumed was unveiled. The new study demonstrates that the visual callosal pathway also transmits information from other routes: information from the left eye that does not initially crosses the midline, is sent via the left visual thalamus over the VCP to the right hemisphere. Also, though the ‘main’ visual callosal pathway from right eye does not involve the right visual thalamus, whenever the researchers blocked activity in the right visual thalamus, the ‘main’ visual callosal pathway was not capable of activating neurons in the right hemisphere. The last result is especially striking, as it could indicate that the right visual thalamus and right VCP could presumably act in a coordinated manner, perhaps fulfilling some gating function in visual processing.
The study by Prof. Dr. Kerr and his colleagues displays the visual callosal pathway in a new light, hinting that the structure is probably much more than just a simple relay station, and might play a more important role in visual processing.