Retina inversion and visual fiber crossings are the principal neuroanatomical mechanisms providing the mirror transformations in the visual systemстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 29 мая 2015 г.
Аннотация:The visual fiber crossing in optic chiasma and the retina inversion in the vertebrates are well-known morphological phenomena. However, the generally accepted explanation of the purposes they serve is absent. In the invertebrates, the retina is not inverted as a rule, but they have the receptor axons crossing at the eye on the ipsilateral side. The biological role of this crossing also has no satisfactory explanation.
The known neuroanatomical data were analyzed and all the above phenomena as neuroanatomical mechanisms providing mirror transformations to the topographical projections of visual fields (VFs) were identified.
This shows the “ipsilateral” receptor axons crossing in the invertebrates (mollusk Octopus), which provides the transformation of the mirror receptor map (model) of VF to the non-mirror neuron map (here and below, the receiving, dendrite sides of the receptor and neuron models are compared with the VF “face”).
The work also shows the “ipsilateral” receptor axon crossing, which provides the transformation of the mirror receptor map (model) of VF to the non-mirror neuron map in the visual system of the insects with the faced eyes.
In the vertebrates, the “ipsilateral” crossing of outputs from photoreceptors is absent. This work shows that in the vertebrates, the non-mirror character of VF map is provided by the retina inversion. Due to the inversion already occurring, the first receptor VF map is the non-mirror map.
The work also identifies the visual fibers crossing in the vertebrates chiasma as a mechanism of mirror transformation, but in respect to the united vision field (UVF) formed from VFs of both eyes.
So, this research shows the mirror UVF projection to the brain before the crossing in the chiasma becomes non-mirror outside of the chiasma. Actually, this exists, as it is, in the animals with nonoverlapping VFs, with the full crossing in the chiasma (their retinas see only UVF ipsilateral half).
In the vertebrates (and humans) having broadly overlapping VFs, the retina sees both sides of UVF: the temporal retina half sees the contralateral side, and the nasal one—the ipsilateral side. In order for such events to form UVF non-mirror projection, theoretically, it is obviously necessary for the nasal half to be projected in the contralateral hemisphere, and for the temporal half—in the ipsilateral one. This theoretical kind of retina projection occurs, as is well known, in the vertebrates with the overlapping VFs really.
All above mirror transformation mechanisms are directed at formation of the neuron maps (models) which would be non-mirror to their originals—VFs and UVF.
The author considers the mirror transformations and their mechanisms as a new (earlier unidentified) type of operations and a new type of the neuroanatomical mechanisms (respectively) in the visual system and in the brain as a whole.