Hering Law Meaning
(2009). Hering`s “Law of Equal Innervation.” In: Binder, M.D., Hirokawa, N., Windhorst, U. (eds) Encyclopedia of Neuroscience. Springer, Berlin, Heidelberg. doi.org/10.1007/978-3-540-29678-2_2185. This theory contrasts with the theory of Hermann von Helmholtz,[9] who asserts that conjugation is a scholarly and coordinated reaction and that eye movements are individually controlled. Helmholtz`s view is now often caricatured as a chameleon and independent eye control, although Helmholtz never defended this theory. Their disagreements concerned the innate vs. learned aspect of coordinated binocular eye movements. Helmholtz`s arguments mainly concerned Listing`s law and can be simplified because there are eye positions in which muscles have different effects on the two eyes.
Therefore, Hering`s Law simply cannot be correct in its original formulation, as it would lead to situations where the eyes would move in different quantities, which both agree on never happens. Herring then changed his law to state that the eyes behave as if they were receiving the same innervation. eBook Packages: Biomedicine and Life SciencesBiomedicine and Life Sciences Reference Module The unique coding of the position and speed of eye movements is a serious challenge to the concept of a “conjugated” vision center and to Hering`s hypothesis. We have created a model based on uniocular eye movement signals and shown that it can correctly simulate the characteristic waveforms of disjunctive saccades (King and Zhou 2002). Busettini and Mays (2005) and Kumar (2006) used simulations to show that disjunctive jerky dynamics can still be explained by an interaction of conjugate commands and Vergence saccades. Van Horn et al. (2008) used careful quantitative analysis to show that the uniocular saccadic control generated by PPRF burst neurons is sufficient to produce disjunctive saccades with correct dynamics without additional contribution to vergence. The inability to find evidence of a midbrain convergence impulse in INO patients (Chen et al. 2010) supports Van Horn et al. and the concept of separate controllers of the right and left eye. Unfortunately, there are currently no shareable links available for this article.
Hering`s response describes the phenomenon in which the manual lift of an eyelid leads to the sinking of the contralateral eyelid (video). This can be attributed to yochin nervation of the palpebrae superioris levator muscles, so that a single signal controls both eyelids [1]. In unilateral ptosis, the increased innervation of the levator muscles compensates for a reduced field of vision on the affected side, but at the same time the unaffected eyelid is raised (panel A). When the ptotic cover is lifted – whether manually, pharmacologically or surgically – this compensatory innervation is reduced and the unaffected lid falls off (panel B). Therefore, unilateral repair of ptosis can cause secondary ptosis of the contralateral eyelid and significant asymmetry; Bilateral PTOSIS repair (simultaneous or delayed) may be necessary for optimal results. Anyone with whom you share the following link can read this content: Model of firing an abducens motor neuron axon during disjunctive smooth tracking. One. Left image: Mueller`s paradigm with his left eye aligned. The rate of fire of the motor neuron is modulated with the movement of the ipsilateral (right) eye. Right image: Mueller`s paradigm aligned with his right eye.
The rate of fire of the motor neuron is paradoxically modulated with the movement of the contralateral eye (left). B. Ocular selectivity of identified abducens motor neurons. According to Zhou and King, 1998. Hering`s answer from the University of Iowa Ophthalmology to Vimeo. DOI: doi.org/10.1007/978-3-540-29678-2_2185 motor neurons have traditionally been considered the “last common pathway,” regardless of how premotor commands are organized, one would expect an extraocular motor neuron to encode a signal related to the eye it innervates. The pattern of firing of extraocular motor neurons was first described in 1970 (Fuchs and Luschei, 1970b; Robinson, 1970; Schiller, 1970). Two general results emerged from these landmark studies: first, motor neuron firing speed is characterized by a linear sum of terms relating to eye position, eye velocity, and eye acceleration. Second, all motor neurons appeared to have the same pattern of firing (called “burst-tonic,” tonic discharge proportional to orbital position and an explosion of spines during saccades) and were thought to be involved in all sorts of eye movements: jerks, tracking, or fixation.
However, no images were taken during the vergence, so it was possible that a separate set of motor neurons could conduct the eye movements of the vergence. Keller and Robinson (1972) recorded the activity of abducent motor neurons during accommodative vergence and reported that changes in discharge rate during glazing in their recorded cell population were similar to changes in discharge rate generated during conjugated eye movements. Subject to the important caveat that they may not have sampled smaller motor neurons, Keller and Robinson concluded that their data supported the summation of independent vergences and conjugated commands, with the “net result appearing as activity in a common final common pathway” (Keller and Robinson, 1972). “It can be shown that the regularity of these associations [between the movements of the two eyes] is simply a matter of training.” Inspired by Bender`s groundbreaking study of clinical brain stem lesions in humans (Bender 1964), monkey studies have shown that lesions of the paramedian pontine reticular formation (PPRF) cause ipsilateral paralysis of the conjugated gaze (Goebel, Komatsuzaki, Bender and Cohen, 1971; Henn, Lang, Hepp & Reisine, 1984). Anecdotal studies have described neurons in the PPRF near the abducens nucleus that exhibit eye movement-related activity during saccades and ipsilateral fixations (“burst neurons”, Cohen & Henn, 1972; Hepp and Henn, 1983; Keller, 1974; Luschei & Fuchs, 1972) projecting abducens on the core (Hikosaka, Igusa, Nakao and Shimazu, 1978; Langer, Kaneko, Scudder & Fuchs, 1986). Based on the injury and physiological data, the PPRF is called the “conjugated vision center,” where a common motor command for conjugated horizontal eye movements is assembled and transmitted to motor neurons in both eyes.