The superior colliculus (SC) is a construction in the midbrain that is a portion of their brain circuit for the transformation of sensory input in movement output. Its major function is currently orienting the animal, particularly with eye movements, to items of interest from the world. This article first summarizes the simple operational structure of the superior colliculus, then considers how the actions of neurons in the SC direct to the creation of eye movements and ultimately addresses questions about the part of the superior colliculus in primates, including its role in supplying information about impending moves to the cerebral cortex.
Functional Structure of the superior colliculus
In mammals, it contains six layers and is the direct homolog of the optic tectum of amphibians, fish, reptiles, and birds. It is the significant center in the brain for the reception of the retina’s output. In mammals, and particularly in primates that we focus on here, the SC continues to receive retinal inputs but it receives massive inputs from the cerebral cortex and subcortical structures such as the basal ganglia.
The monkey superior colliculus includes six alternating grey and white layers with an additional small fiber layer on its surface (the stratum zonale). These layers have different characteristics and identifying them is critical to explaining and understanding the organization of this superior colliculus. The superficial layers include a gray and a deeper white layer (the superficial gray as well as the articular layers) followed with the intermediate grey and white layers along with the deep gray and white layers.
The input signal to the nerves in the dorsal component of the superficial layers is straight in the retina, but with increased thickness in the shallow layers of the visual feedback are increasingly more determined by the input from visual cortex: ablation of the principal visual cortex considerably lowers the visual feedback of these nerves. While the terms’ grey and layers indicate fiber and subcutaneous layers, as is true in the cerebral cortex, there are scattered from the layers since there are fibers of passage from the layers.
A significant output of the layers is that the one on the layers which has been shown in slice preparations of this superior colliculus. 1 possibility is that the layers of the SC lie on another pathway from retina to the cortex to the retina, visual cortex pathway, lateral geniculate. An alternate perspective is that the SC into pulvinar into cortex pathway provides a blend of sensory– engine data which supplies the cortex as opposed to an input with a modulator input.
The inputs into the intermediate layers of the SC are from areas of cortex past the visual areas like the frontal eye field of the cortex and the lateral region of cortex, in the shallow layers. Their signal is A significant input by the substantia nigra pars reticulata of the basal ganglia.
The crucial point is the pathway crosses the midline at the stage so that action in and over the superior colliculus is connected chiefly to saccades generated toward the visual field contralateral to the side of their mind of this neuron, whereas neuronal action beneath the superior colliculus is connected to saccades made into the ipsilateral side. An ascending output would be during the dorsal nucleus of the thalamus to the cortex. Neurons from the shallow grey and optic layers provide a brief latency (about 40 ms) responses into the beginning of visual stimulation.
The stimulation is a thing or a spot in 1 part of their visual field contralateral to the SC in. Neurons in the grey and coats reveal a burst of activity following the beginning of stimulation but increased action until the fighter makes eye movements beginning. Many neurons in the deeper layers of the superior colliculus (deep grey and white coats ) have properties very similar to those from the intermediate layers, and additionally, they often respond to sensory modalities aside from vision like auditory and somatosensory stimulation. The nature of the neurons suggests a movement originated by action at the superior colliculus may come from input aside from the visual or in conjunction.