Divergence is a circuit of the central nervous system that is relevant to the acuity of perceptions. Each receptor is divergently connected to neurons at higher levels and at the same time is convergently attached to neurons at lower levels. Disturbances of the divergence-covergence principle can occur after nerve damage.
What is divergence?
Each neuronal cell is connected to multiple neurons from higher layers. This principle corresponds to divergence. The individual levels of information processing in the human central nervous system are subject to different circuit principles. The most important of these principles are convergence and divergence. The two circuits result in the formation of contrast by lateral inhibition. Human sensory organs are equipped with sensory cells, also known as receptors. Each of these receptors corresponds to an information line that leads to the thalamus via several levels of neurons. The thalamus has a connection to the cerebrum, where sensory input is finally processed. There is a divergent connection between the levels of neurons instead of a one-to-one connection. For example, each neuronal cell is connected to several neurons of the higher layers. This principle corresponds to divergence. Signal reception for receptors and neurons of lower layers is called convergence. The convergence-divergence principle leads to lateral inhibition, in which the downstream neurons each cause a signal reduction in neighboring cells. The resulting arousal pattern maps the intensity pattern of incoming stimuli in a differentiated manner, as the individual transitions are thus amplified and contrasted in conscious perception.
Function and task
In mammals, the principle of convergence and divergence shapes both the processing of primary sensory data from the retina, cochlea, and skin senses, and the connection between the thalamus, cerebrum, and cerebellum. Through divergence and convergence, all diffuse stimuli from the environment are immediately given a delineated differentiated form. In this way, the stimulus data are immediately structured holistically and coherently. The nervous system carries out this structuring automatically. For example, thanks to divergence and convergence, the visual system automatically delivers images with sharp contours. Based on convergence and divergence, the human cerebrum already receives structured information from the receptors of the individual sensory systems and their receptors. Already the forwarded perceptual information thus deviates strongly from reality. From an evolutionary point of view, divergence and the perceptual information structured in this way is important because it makes it easier for the organism to make vital reactions to the environment. Due to the distortion caused by convergence-divergence principles, humans can, for example, recognize individual pitches from an auditory input or recognize instruments even though they sound together. The visual system, thanks to lateral inhibition as a result of divergence and convergence, can identify shapes in motion, for example, and the gustatory system can thus recognize different types of food from a single bite or sip. Lateral inhibition due to divergence and convergence is a subconscious process that is not perceived in most cases. However, optical illusions, for example, make use of the divergence-convergence principle and in this way confront people directly with the phenomenon of lateral inhibition. Thus, he consciously notices how much the basic principles of perception alienate the reality around him.
Diseases and ailments
When there is damage to neuronal structures, the divergence principle of perception may be disturbed. Neuronal damage may be due to a variety of contexts. For example, various neurologic diseases may be the cause of lesions in the central nervous system. In diseases such as multiple sclerosis, for example, the patient’s immune system causes inflammation in the nerve tissue of the central nervous system and can thus permanently damage the central nerve structures. Neuronal cells are then no longer connected to several neurons of the higher layers when the higher-lying neurons are damaged. Such a phenomenon is tantamount to a disruption of the divergence principle.If, in turn, the divergence principle is disturbed, lateral inhibition by divergence and convergence is also disturbed. In the visual system, lateral inhibition plays a role especially for the quality of sensory impressions at dusk. For example, damage to retinal transverse neurons can complicate difficulties in summing individual stimuli of a receptive field during dark adaptation and lateral inhibition during light adaptation. The result is discomfort in twilight vision. Also in extreme brightness, the patient’s visual perception is impaired. Such complaints may be present, for example, in the context of diabetic retinopathy or may be due to X-linked night blindness. The divergence principle also plays a decisive role for the skin sense. Disorders of the divergence due to nerve damage can therefore also affect this area of perception and thus reduce tactile acuity in the haptic and tactile areas. In any disorders of lateral inhibition, the propagation of excitation in the central nervous system is no longer spatially limited, which can result in overexcitability of the nervous system. The brain no longer receives clearly structured information from the sensory systems from an overexcited nervous system with reduced lateral inhibition. In all complaints related to divergence of the nervous system, contrast of perceptions is diminished or even abolished, making it difficult for the person to recognize and interpret sensory input.
