i find the concept of a god, soul , afterlife very implausible . what is there a large primate somewhere hiding but has the power and interest to read every human's thoughts every second at the same time all 8 billion at the same time (wtaf? why? ). why does any thing matter or is anything important? nothing matters. but they would have us believe some hidden god or some hidden super intelligent programmer created earth a giant torture chamber where for 500 million years animals and humans were tortured for what reason? why is torturing animals important or necessary ? most animals died by being eaten alive by other animals parasites or bacteria.
why are the souls and god hiding? why?
to explain it. there is a brain and eyes on an animal . the eyes send patterns of light to the brain for example of a banana . the brain "shapes" the neural networks to form a model of that banana . evolution programmed that and the hunger and desire to eat the banana into an ape brain . so that's why the banana and eating is important cause it was programmed into the brain by evolution. evolution just wants to replicate the genes . but it has no intelliegence nor real purpose just an accident of chemistry chemical reactions.
nothing really matters . the only thing that matters is avoiding unending constant unbearable pain.
life is a scam.
other meaningless crap addictions were programmed by evolution and also culture society other people media .
and i find the concept of a devil even more ridiculous. there's supposedely an invisible animal with horns that has so much power to cause humans to do all the evil and can also monitor 8 billion humans at the same time.
this is just part of an article of which there are millions . shows they've been doing research for 100 years on just the fly vision brain . and they say this in all the books a human is just another animal like a fly or mouse as they do it in this article . they don't say it's opinion but proven and it's in all the brain, cell , evolution books. they also say fly neuron which is a fly brain cell . and an individual brain cell in a human is the same as in a fly
Nervous systems evolved to allow animals to perceive, interact with, and move through the environment. In many animals, including humans and flies, vision is the dominant sensory modality. Vision is arguably best suited to perception at a distance, and its operation over short timescales enables dynamic guidance of ongoing behavior. In
Drosophila melanogaster, each compound eye transmits information about the visual scene to over 100,000 neurons in each
optic lobe, with both optic lobes together accounting for more than half of the neurons in the adult brain (
Raji and Potter 2021). This dramatic allotment of biological resources to
visual processing suggests both that vision plays a central role in fly behavior and that a significant amount of computing power is required to extract behaviorally relevant features from visual environments.
This review will discuss nearly a century of work examining visual processing and visually guided behavior in the fruit fly. These studies have taught us a great deal about the circuits and computational mechanisms that support vision. Despite vast anatomical differences, insect and mammalian visual systems perform many of the same
computations, from the detection of motion to calculations of animal position and heading direction (reviewed in
Clark and Demb 2016;
Green and Maimon 2018). Further, the stereotyped and well-described anatomy and synaptic connectivity of the fly visual system have facilitated cellular (and sometimes subcellular)-resolution dissections of visual computation. These mechanistic insights have generated concise models of computation that can be tested at the circuit and cellular level in other model systems. In this way, studies of physiology and behavior in flies have revealed fundamental principles of visual processing that can be found across the animal kingdom. Here we have focused on a broad review of the literature, with the goal of introducing those new to the field to the many contributions that have been made. However, current work accounts for less than a quarter of the visually responsive neurons—even with everything we have learned, the fly visual system has many mysteries left to explore.
Given the scale of neural processing power devoted to vision, it is not surprising that this sense guides, evokes, or otherwise supports a variety of ethologically relevant behaviors. Perhaps the simplest visual behavior is
phototaxis—an innate drive to fly or walk toward (or away from) light (
Carpenter 1905;
Heisenberg and Buchner 1977;
Miller et al. 1981). In flies, phototactic behavior has been used extensively to dissect phototransduction and the neural mechanisms underlying
spectral preferences (
Hadler 1964;
Benzer 1967;
Pak et al. 1969). Given the choice between colored and white light of the same intensity or between 2 lights of different colors, flies show preferences for green (∼485 nm) and near-UV (∼365 nm) wavelengths (
Bertholf 1932;
Schümperli 1973;
Hu and Stark 1977;
Fischbach 1979;
Gao et al. 2008;
Yamaguchi et al. 2010;
Karuppudurai et al. 2014;
Otsuna et al. 2014). Overall, UV light attracts flies most strongly, but becomes aversive at high intensity. Importantly, phototactic preference is also under circadian control, with UV light eliciting the strongest attraction during subjective daytime hours (
Hu and Stark 1977;
Lazopulo et al. 2019).
Flies use
optic flow, the pattern of motion generated by a visual scene moving over the eye, to guide ongoing locomotion. The "optomotor response" describes the tendency for a fly to turn in the direction of visual motion, a behavior that has been a focus of intense study for decades (
Kalmus 1943;
Götz 1964;
Reichardt and Wenking 1969;
Götz and Wenking 1973;
Heisenberg and Götz 1975;
Reichardt and Poggio 1976;
Heisenberg and Wolf 1979;
Götz 1987;
Wolf and Heisenberg 1990;
Tammero et al. 2004;
Maimon et al. 2008;
Mronz and Lehmann 2008;
Theobald et al. 2010;
Schnell et al. 2014). This optomotor response is most often studied with a tethered preparation, where a fly orients itself relative to a visual panorama. During forward movement, optic flow moves from front to back across both eyes, while side-slip or turning causes optic flow patterns that differ between the eyes. As a result, differences in optic flow signals across the eyes can indicate that the fly has been displaced off course and cause the fly to make a compensatory turn in the direction of visual motion. Similarly, flies can control their forward flight or walking speed using front-to-back visual motion signals (
Budick et al. 2007;
Katsov and Clandinin 2008;
Fry et al. 2009;
Rohrseitz and Fry 2011;
Reiser and Dickinson 2013;
Silies et al. 2013;
Fuller et al. 2014;
Creamer et al. 2018). Together, these reflexive maneuvers allow a fly to maintain straight, stable movement trajectories while walking or flying. Importantly, in addition to these stabilizing reflexes, flies can also voluntarily initiate course-changing turns that increase optic flow and are separately controlled (
Ferris et al. 2018;
Fenk et al. 2021).
Flies also respond to
looming stimuli: objects with retinal coverage that expands in all directions, such as approaching predators, obstacles, or landing sites. Visual loom in the dorsal visual field causes walking flies to freeze in place or, if the loom is very large or very fast, causes them to initiate take-off escape maneuvers (
von Reyn et al. 2014;
Wu et al. 2016;
von Reyn et al. 2017;
Ache et al. 2019a). In flight, visual expansion, particularly in the ventral visual field, evokes rapid evasive reorientations or landing responses (
Tammero et al. 2004;
Bender and Dickinson 2006,
Reiser and Dickinson 2013;
Muijres et al. 2014;
Ache et al. 2019b). Flies will also sometimes walk backwards in response to looming objects that approach slowly (
Bidaye et al. 2014;
Sen et al. 2017). Collectively, loom responses illustrate the importance of vision-driven behaviors for survival, as they allow flies to escape predation and avoid detection or collision.
Flies can also associate a variety of visual cues with reward or punishment. Environmental features such as brightness and color can provide contextual information that a fly can pair with positive or negative feedback (
Quinn et al. 1974;
Liu et al. 1999;
Aso et al. 2014b;
Vogt et al. 2014,
2016). In flight simulator experiments, oriented visual patterns and objects with different sizes, shapes, colors, or brightnesses can be associated with aversive stimuli (
Dill et al. 1995;
Wolf et al. 1998;
Tang and Guo 2001;
Liu et al. 2006;
Zhang et al. 2007;
Wang et al. 2008;
Pan et al. 2009;
Solanki et al. 2015;
Koenig et al. 2016). Flies also use visual features of the environment to triangulate specific locations, demonstrating visual place learning (
Ofstad et al. 2011;
Haberkern et al. 2019). Perhaps more impressively, flies can remember the location of specific visual objects without prior training (
Neuser et al. 2008;
Kuntz et al. 2017;
Sun et al. 2017). These observations jointly illustrate the utility of a wide range of visual features in supporting learned behavior.
Visual features such as landmarks or locomotor guidance cues also form the basis of long-range navigational behaviors. The sun is a prominent visual feature in natural settings and, as such, plays an outsized role in directing behavior. As noted above, solar UV light is highly attractive to flies. Flies can also sense the
polarization of sunlight and use it as an orienting cue, often aligning their locomotion with the angle of polarization (
Wolf et al. 1980;
Wernet et al. 2012;
Weir and Dickinson 2012;
Velez et al. 2014;
Mathejczyk and Wernet 2020). Sunlight polarization is common in natural settings, providing a reference frame for determining travel direction (
Warren et al. 2018). This role of the sun as a landmark can be seen in
menotactic locomotion, defined as straight-line travel over long distances in which a visual landmark is kept at a constant, arbitrary angle. The orientation of the sun, as well the distribution of its polarization angles, can guide this behavior (
Giraldo et al. 2018;
Warren et al. 2018;
Green et al. 2019).
Beyond the prominent spatial cues provided by the sun, individual visual objects can also direct locomotion. High-contrast, vertically oriented objects—potentially representing a distant tree or other desirable perch—can attract flying and walking
Drosophila (
Reichardt and Poggio 1976;
Strauss and Heisenberg 1993;
Maimon et al. 2008,
Robie et al. 2010;
Ache et al. 2019b;
Linneweber et al. 2020). The specific shape of such objects modulates their attractiveness, with taller objects being most attractive and shorter objects eliciting aversive responses (
Maimon et al. 2008). However, flies will investigate dark spots when they are paired with attractive olfactory stimuli or during courtship (
van Breugel and Dickinson 2014;
Kohatsu and Yamamoto 2015;
Ribeiro et al. 2018;
Hindmarsh Sten et al. 2021). Flies are even capable of estimating the size and distance of terrain features or moving objects based solely on visual cues (
Cook 1980;
Pick and Strauss 2005;
Agrawal et al. 2014;
Kohatsu and Yamamoto 2015;
Coen et al. 2016;
Triphan et al. 2016;
Ribeiro et al. 2018). This ability supports a diverse set of behaviors, including the pursuit of conspecifics during courtship and the crossing of terrain gaps during terrestrial navigation.
Collectively, this suite of visual behaviors is diverse, and there are undoubtedly additional visual behaviors that have not yet been discovered. Nonetheless, visual processing circuits must be sufficiently complex to extract many salient visual features and to flexibly couple these cues to a wide range of behavioral outputs.
The wealth of publicly available anatomical and genetic resources makes the fly an excellent model for studying visual processing. For
anatomy, nearly comprehensive atlases of optic lobe cell types exist, alongside well-annotated connectome studies (
Fischbach and Dittrich 1989;
Morante and Desplan 2008;
Takemura et al. 2013;
Nern et al. 2015;
Morimoto et al. 2020;
Kind et al. 2021;
Shinomiya et al. 2022). These resources have facilitated an unambiguous assignment of functional properties to particular cell types and revealed how synaptic connectivity can support fundamental visual computations. Single-cell RNA sequencing data are also available for many visual system cell types, providing genetic insights into the function of each neuron (
Kurmangaliyev et al. 2020;
Özel et al. 2021;
Davis et al. 2020;
Konstantinides et al. 2022). Together, these resources create a fertile ground for understanding the diverse functions of neurons involved in visual processing.
