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Russell Powell Biography

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“In order to avoid the deafening of conspecifics, some bats employ a jamming avoidance response, rapidly shifting frequencies or flying silent when foraging near conspecifics. Because jamming is a problem facing any active emission sensory system, it is perhaps not surprising (though no less amazing) that similar jamming avoidance responses are deployed by weakly electric fish. The speed of sound is so fast in water that it makes it difficult for echolocating whales to exploit similar Doppler effects. However, the fact that acoustic emissions propagate much farther and faster in the water medium means that there is less attenuation of ultrasound in water, and thus that echolocation can be used for broader-scale 'visual' sweeping of the undersea environment. These constraints and trade-offs must be resolved by all acoustic ISMs, on Earth and beyond. There are equally universal anatomical and metabolic constraints on the evolvability of echolocation that explain why it is 'harder' to evolve than vision. First, as noted earlier, a powerful sound-production capacity, such as the lungs of tetrapods, is required to produce high-frequency emissions capable of supporting high-resolution acoustic imaging. Second, the costs of echolocation are high, which may limit acoustic imaging to organisms with high-metabolisms, such as mammals and birds. The metabolic rates of bats during echolocation, for instance, are up to five times greater than they are at rest. These costs have been offset in bats through the evolutionarily ingenious coupling of sound emission to wing-beat cycle, which functions as a single unit of biomechanical and metabolic efficiency. Sound emission is coupled with the upstroke phase of the wing-beat cycle, coinciding with contraction of abdominal muscles and pressure on the diaphragm. This significantly reduces the price of high-intensity pulse emission, making it nearly costless. It is also why, as any careful crepuscular observer may have noticed, bats spend hardly any time gliding (which is otherwise a more efficient means of flight).”

BatsMetabolismEcholocationWing Beat Cycle
Book:Contingency and Convergence: Toward a Cosmic Biology of Body and Mind
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“As with cross-modal task transfer in echolocating dolphins, spontaneous cross-modal recognition in weakly electric fish strongly suggests that electrolocated objects are being perceived holistically in three dimensions with a representational format and/or phenomenological quality that is analogous in fundamental ways to vision. Object recognition across ISMs is thus a robustly replicable phenomenon and is indicative of both the common representational formats of ISM percepts and their global access. Further, as von der Emde and colleagues point out, cross-modal recognition is not a quirk of experimental artifice. Rather, it is a crucial adaptive functionality that ensures reliable perception in complex environments in which information flowing in from different senses must be weighted and adjusted in accordance with fluctuating conditions, such as changes in turbidity, lighting conditions, and so forth.”

VisionEcholocationElectrolocationCross Modality
Book:Contingency and Convergence: Toward a Cosmic Biology of Body and Mind
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“The relation between binding and consciousness is less clear. Neurocognitive binding surely affects the character of Umweltian consciousness and may be a necessary condition for it. Whether binding provides sufficient conditions for subjectivity in Umweltian or even more basic forms is not evident. In theory, neurocognitive binding and phenomenological binding could come apart - this would be implied, for example, by evidence that bound representations are sometimes formed outside of subjective experience. One possibility is that binding may not be sufficient for phenomenal consciousness unless it also includes affective content that projects meaning onto objects and events, then bound representations that lack affective content would fail to generate conscious experience. It could be, for instance, that bound representations are formed by the synchronous firing of distributed neural systems that specialize in different features of the scene, but that this bound representation must then be made accessible to the wider system for memory, categorization, and affective response if it is to become part of the stream of consciousness. And if this is so, then information integration would not be sufficient to generate subjectivity. Although much of this picture remains opaque, work on binding is providing the first glimpse of how the Umwelt was made.”

ConsciousnessBindingUmwelt
Book:Contingency and Convergence: Toward a Cosmic Biology of Body and Mind
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“It is true that neural tissue imposes significant metabolic demands on organisms that natural selection will tend to shed if doing so is beneficial. It is also true that brain size has been reduced in many animal lineages for whom the metabolic costs of cognitive substrate outweigh the benefits of enhanced cognition. This is poignantly illustrated by secondarily herbivorous vertebrates (like panda's) whose calorie-frugal diet can no longer sustain their carnivorous clade's historical brain tissue expenditures. It is the case as well for lineages whose ecology calls for the reduction of neurologically demanding somato-sensory functions, such as 'cavefish' - several groups of freshwater fish adapted to lightless underground habitats that have repeatedly lost portions of the cortex dedicated to visual processing. The loss of a complex head is thus not totally inconceivable.”

BrainDietCaloriesCalorie Counting
Book:Contingency and Convergence: Toward a Cosmic Biology of Body and Mind
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“How does electrolocation work, and what can we say about its representational and phenomenological qualities? Constant electric organ discharges emanating from the caudal region maintain a stable spatial voltage pattern over the skin surface. This voltage pattern changes when objects that have a resistance different from the surrounding water come within range of the signal and distort the field, resulting in changes of local electric voltages at particular skin loci. Objects can alter the stable electric discharge field in waveform and/or in amplitude, and weakly electric fish can detect both types of disruptions. These changes in local transepidermal electric current flow are recorded by the skin electroreceptors, which act as a 'retina' upon which an electric image of the object is projected. This image is then transduced, and the information is fed to regions of the brain that process higher-order features of objects. Whereas in humans the processing of higher-order features of objects take place in the cerebral cortex, in electrolocating fish these cognitive tasks are carried out in their hypertrophied cerebellum. The 'mormyrocerebellum' is so oversized that it accounts for the vast majority of the organism's total oxygen consumption, with metabolic expenditures exceeding that of any vertebrate. This, in turn, speaks to the great functional utility of electrolocation: all that brain stuff must be doing something computationally demanding and ecologically important.”

ElectrolocationMormyrocerebellum
Book:Contingency and Convergence: Toward a Cosmic Biology of Body and Mind
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