(Wednesday, July 4, 9am)
VIDEO OF PRESENTATION
VIDEO OF PRESENTATION
Since Thomas Nagel wrote in 1974 about echolocating bats for their alien sense of the world, the question of animal awareness has surged in biology and psychology. This is due to several factors: the reemergence of the cognitive realm of inquiry in psychology following the implosion of behaviorism, the increased appreciation of awareness as a wellspring of adaptive behavior, neuroscience seizing upon potential underlying mechanisms, and computational exploration of what awareness might mean.
The content of a bat’s percepts depends on the process of sonar, which stands apart from visual definition of our surroundings. Indeed, man-made sonar systems rely primarily upon converting acoustically-acquired information about scenes into visual displays of these same scenes so that the operator can locate objects and determine their characteristics. The “otherness” of the bat’s world derives from the absence of such a visual sonar display. Instead, there is an intrinsically auditory definition of “objects” and “scenes” that generates sharp spatial percepts from very neural representations that are very dispersed both in brain location and in time.
Bats emit a wide band of high frequencies in echolocation sounds and perceive images that portray details of objects in proportion to the bandwidth of the echoes. Wide bandwidth means sharp registration of echo delay for object distance, including the distance to different parts of the object. When the bat aims its head, ears, and broadcast beam at an object, all frequencies in broadcasts impinge on the object and then return in echoes. The bat’s resulting percepts are in focus. The object is attended to and registered as its constituent reflecting points in depth. Regular, discrete loss of frequencies in echoes caused by overlapping reflections from different parts of the object contributes to reconstruction of object shape.
Wider swathes of frequencies removed from echoes occur when the object is located off the axis of the broadcast beam, which is the region of space not momentarily the target of the bat’s attention. It defocuses the resulting percepts and by this means removes them from attention. In spite of information about individual objects being widely dispersed across auditory frequency representations and neural response latencies, the object itself is perceived as having a discrete location in distance through sharp registration of echo delay.
Continuity of the behavior of bats in surroundings that range from simple (chasing a flying insect or avoiding an obstacle in an open space) to increasingly complex (flying through a cluttered scene with branches and leaves of vegetation) to exceptionally complex and, crucially, dynamic action (flying in close quarters in company with other bats, all emitting similar sonar sounds) is part of the evidence for some kind of awareness in bats, as is the apportioning of attention to parts of scenes and the auditory mechanisms for imposing inattention on background elements of scenes. How the dispersed time and space representation comes to be compressed into the percept is the essence of the problem of how awareness is distinct from its neural underpinnings.
Simmons, J. A. (2017). Theories About Target Ranging in Bat Sonar. Acoustics Today 13(4)
Nagel, T. (1974). What is it like to be a bat?. Philosophical Review, 83(4), 435-450.
Warnecke, M., and Simmons, J. A. (2016). Target shape perception and clutter rejection use the same mechanism in bat sonar. J. Comp. Physiol. A 202, 371-379.
About the neurophysiology of the echolocation, I can guess that the ear of the bats are really important for the well-working for the echolocation. However, I was wondering if there was any other “body-parts” that were important also? Perhaps an auditory area in the brain? Since they don’t really see and are orienting themselves with echolocation, maybe the auditory area is taking all the place of the vision? In brief, what is the neurophysiology of the echolocation and are there any pathways or changes in the brain of the bat that allow the echolocation?
ReplyDeleteYou just said that the colliculus, among others I guess, is involved.
DeleteDo the bats can receive the echo of the echo of themselves? I mean, do you think that they can perceive the sound that they emit, that reverberate on a surface, then reverberate on themselves and then reverberate on a surface before coming back to their ears? If it is the case, it would be like they always have a mirror to "see" themselves in and I would suspect that they should have a high sense of themselves in space. Is there non-visual self-recognition test for bats?
ReplyDeleteFascinating presentation!
ReplyDeleteI am sorry if some of those questions were answered; the video stopped at some point, came back a few minutes later.
Has there been research on the very few humans that can echolocate (blind people using clicks or their cane sound to navigate and see their environment) to compare the processes from the bat echolocating on the neurological level? Is that completely different?
Could we devise a way to see if bats can discriminate between species of insects and obstacles – can they have preference for some pray more than for some others? I’m wondering if this echolocation system can tell us if there is multimodal representations in bats. The presentation showed how sophisticated this system was (frequency, time, amplitude, harmonics, double-clicks…) and this leads me to think that the information produced with this system must be rich and diverse – is it : «there’s something there» or «that’s there»?
In addition, I’m not sure I understand what you meant by : they process the sound of a sound...
1. I think I’ve heard of some kind of “habituation” in blind humans, them using more their auditory cues to get around (though it’s still not as efficient as the bats’. I think it’s like when people are stuck in a cave for so long then are exposed to light, they can’t see well (they are likeblinded), maybe when people can’t see, they focus on hearing and this is how they can get around easier than when we try doing it immediately.
Delete2. I think it is “that’s there”, because the bat can actually make the different between moving and still objetcs, as well as have a mental image of the thing, it gives some sort of shape that they can associate with the insect for instance. This is IF I understood correctly.
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ReplyDeleteLes chauves-souris utilisent leur écholocation pour différentes tâches. Elles envoient des ultrasons et reçoivent ensuite un feedback qu’elles traitent. Elles peuvent utiliser leur écholocation pour se déplacer dans leur environnement et l’utiliser pour se former une «image» d’un objet. Elles ajustent leurs fréquences dépendant de la tâche à réaliser et peuvent traiter une quantité phénoménale de signaux sonores. Leur utilisation des différentes fréquences selon les tâches suggèrent fortement qu’elles sont conscientes de leur environnement et s’adaptent à celui-ci. Elles semblent aussi utiliser des ultrasons pour communiquer entre elles.
ReplyDeleteAussi, ces recherches montrent que, dans certains cas, on peut bien étudier le comportement d’un animal en laboratoire et l’appliquer aux animaux en milieu naturel, les chauves-souris utilisant leur écholocation dans les deux milieux.
J’ai été étonné par le fait que les chauves-souris soient capables de se retrouver dans le noir avec l’écholocalisation entre les branches d’un arbre en se pourchassant les unes les autres. Elles doivent naviguer dans leur environnement où il y a beaucoup d’obstacles. Elles doivent réagir rapidement. Elles sont capables, avec les échos, de savoir quels objets sont où dans l’environnement. Elles “voient” et reconstruisent l’environnement dans des conditions parfois extrêmement complexes et difficiles. Tout ceci nous donne beaucoup de signes de “l’awereness” des chauves-souris.
ReplyDeleteThanks for the talk. I was wondering if you had any ideas about what bats experience when they hear the echo-location sounds, based on looking at the mechanisms in the brain. Do you think that they hear things in the same sort of way we do but only more fine grained, or is it something closer to what we would think of as sight?
ReplyDeleteIt is a complete other way to live in an environment that is spatially represented by auditory cues. I think that it makes the other mind problem even more hard for us; it is impossible for us to know what it feels like to echolocate. On that point, I was really impressed to learn that some blind people learned to echolocate by using clicks sounds, it was the first time I heard of it. I knew that, due to the plasticity of the brain, the auditory cortex was more developed among blind people, but I didn’t know about echolocation. Maybe the study of bats, as they echolocate in the same way as humans (making mouth sounds and perceiving it with their ears) in contrary to dolphins which use a different anatomical structure (the melon), will tell us more about the way to echolocate and will help blind people on how to use it.
ReplyDeleteJe crois que la complexité du système utilisé par les chauve-souris pour se retrouver, soit l'"echolocation". Ce processus est vraiment intéressant et prouve que nous ne sommes pas la seule espèce qui est dotée de caractéristiques unique et propre à l'espèce (humains = langage). En écoutant les conférences, je me rendais de plus en plus à l'évidence que la supériorité que nous nous attribuons est basée sur l'ignorance des autres espèces. Les chauve-souris nous surpassent dans le noir, tout comme chacune des espèces a des particularités en fonction de leur être, de leur milieu social et de leur environnement.
ReplyDeleteTo make the link with the social bonding mentioned in previous conferences, do bats use specific sounds or cries to be able to form pairs and reproduce? Thank you.
ReplyDeleteI would like to know more about Dr Simmons' opinion or position about the question of the echolocation in big fruit bats. Here is some articles I've found about it:
ReplyDeletehttps://www.washington.edu/news/2018/02/07/fruit-bats-echolocation-may-work-like-sophisticated-surveillance-sonar/
http://www.sciencemag.org/news/2017/01/bats-without-sonar-shed-light-evolution-echolocation
https://www.nature.com/articles/s41467-017-02532-x
Was Dr Simmons involved in some research with big/flying fox bats?
My first question is that the bat is aware or "sees" how far up? what distance?
ReplyDeleteAnd my second question is does it verify or check behind it regularly?
Do a bat’s echolocation signal interfere with another one close by, or do they have some king of “signature” to the sound wave in order to discriminate their own?
ReplyDeleteThank you very much for the talk. I wonder, if bats use sound to create auditory pictures, do they communicate with conspecific? And if so how? Are the sounds made for echolocation used as well to find a mate in the same way as nutcrakers?
ReplyDeleteIl semble que les chauves-souris n'ont pas la nécessité de la lumière pour vivre dans ce monde puisqu'elles peuvent se nourrir, se déplacer et même communiquer entre elles grâce à leur capacité d'écholocation. Pourraient-elle vivre dans une noirceur totale? La lumière est-elle une condition nécessaire à la vie? (je parle bien de lumière, et non de chaleur).
ReplyDeleteCar au contraire, la plante à nécessairement besoin de lumière pour vivre puisqu'elle y tire son énergie. La plupart des espèces ont besoin de lumière pour pouvoir s'orienter et identifier les objets, mais aussi pour produire de la vitamine D par exemple.
La question me mène à me questionner sur les êtres marins qui peuplent les profondeurs des océans. Ont-elle accès à une petite quantité de lumière ou pas du tout?
Finalement, ma question est la suivante: la lumière est-elle nécessaire à la survie des chauves-souris? Y tire-t-elle quelque chose?