Dominant Glint Based Prey Localization in Horseshoe Bats: A Possible Strategy for Noise Rejection

Rhinolophidae or Horseshoe bats emit long and narrowband calls. Fluttering insect prey generates echoes in which amplitude and frequency shifts are present, i.e. glints. These glints are reliable cues about the presence of prey and also encode certain properties of the prey. In this paper, we propose that these glints, i.e. the dominant glints, are also reliable signals upon which to base prey localization. In contrast to the spectral cues used by many other bats, the localization cues in Rhinolophidae are most likely provided by self-induced amplitude modulations generated by pinnae movement. Amplitude variations in the echo not introduced by the moving pinnae can be considered as noise interfering with the localization process. The amplitude of the dominant glints is very stable. Therefore, these parts of the echoes contain very little noise. However, using only the dominant glints potentially comes at a cost. Depending on the flutter rate of the insect, a limited number of dominant glints will be present in each echo giving the bat a limited number of sample points on which to base localization. We evaluate the feasibility of a strategy under which Rhinolophidae use only dominant glints. We use a computational model of the echolocation task faced by Rhinolophidae. Our model includes the spatial filtering of the echoes by the morphology of the sonar apparatus of Rhinolophus rouxii as well as the amplitude modulations introduced by pinnae movements. Using this model, we evaluate whether the dominant glints provide Rhinolophidae with enough information to perform localization. Our simulations show that Rhinolophidae can use dominant glints in the echoes as carriers for self-induced amplitude modulations serving as localization cues. In particular, it is shown that the reduction in noise achieved by using only the dominant glints outweighs the information loss that occurs by sampling the echo

Training-Induced Plasticity of Auditory Localization in Adult Mammals

Accurate auditory localization relies on neural computations based on spatial cues present in the sound waves at each ear. The values of these cues depend on the size, shape, and separation of the two ears and can therefore vary from one individual to another. As with other perceptual skills, the neural circuits involved in spatial hearing are shaped by experience during development and retain some capacity for plasticity in later life. However, the factors that enable and promote plasticity of auditory localization in the adult brain are unknown. Here we show that mature ferrets can rapidly relearn to localize sounds after having their spatial cues altered by reversibly occluding one ear, but only if they are trained to use these cues in a behaviorally relevant task, with greater and more rapid improvement occurring with more frequent training. We also found that auditory adaptation is possible in the absence of vision or error feedback. Finally, we show that this process involves a shift in sensitivity away from the abnormal auditory spatial cues to other cues that are less affected by the earplug. The mature auditory system is therefore capable of adapting to abnormal spatial information by reweighting different localization cues. These results suggest that training should facilitate acclimatization to hearing aids in the hearing impaired

Hydrodynamic stimuli and the fish lateral line.

Bleckmann H, Engelmann J, Hanke W, Mogdans J. Hydrodynamic stimuli and the fish lateral line. Nature. 2002;408(6808):51-52

Participación Política, Medios de Comunicación y Redes Sociales en los Adolescentes Catalanes

El grado de implicación política de los adolescentes es una cuestión abierta que atraviesa el debate académico generación tras generación. Actualmente, esta cuestión se ve salpicada por la irrupción de las redes sociales y los nuevos medios. El presente artículo estudia la vinculación entre el uso de medios, redes sociales y el interés por la política de una amplia muestra de estudiantes catalanes del último curso de Educación Secundaria Obligatoria. La investigación concluye que las dinámicas de participación política y las plataformas de debate de los adolescentes no difieren en exceso de las generaciones mayores y que, por tanto, las redes sociales no parecen haber afectado al grado de implicación política de los adolescentes

Design and fabrication process for artificial lateral line flow sensors

In fish the lateral line is a sensory organ used to perceive water movement in the surrounding environment to localize prey or predators, to avoid obstacles, for schooling and more. The lateral line consists of many mechanoreceptors called neuromast which consist of groups of hair cells covered by a jelly-like cupula. There are two types of neuromasts: superficial neuromasts which are situated on the skin, and canal neuromasts which are located canals that are connected to the water outside of the fish through a series of pores. We review design aspects for MEMS fabrication of capacitive hair based flow sensor arrays opera¬ting in aquatic environments, biomimicking neuromasts. Exploiting information gained from nature building a system that allows the study of hydrodynamic mechanical interactions in complex noisy environments may help to uncover more about nature and how to make reliable artificial systems

Ermittlung von Verfahrens- und Prozessparametern beim Innenhochdruckumformen von Hohlprofilen mit Nebenformelementen aus ebenen Zuschnitten Abschlussbericht

SIGLEAvailable from TIB Hannover: RO 146(87) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekArbeitsgemeinschaft Industrieller Forschungsvereinigungen 'Otto von Guericke' e.V. (AIF), Koeln (Germany); Bundesministerium fuer Wirtschaft, Bonn (Germany)DEGerman

One tone, two ears, three dimensions: A robotic investigation of pinnae movements used by rhinolophid and hipposiderid bats

Bats, which echolocate using broadband calls, are believed to employ the passive acoustic filtering properties of the head and pinnae to provide spectral cues which encode 3-D target angle. Microchiropteran species whose calls consist of a single, constant frequency harmonic (i.e., some species in the families Rhinolophidae and Hipposideridae) may create additional acoustic localization cues via vigorous pinna movements. In this work, two types of echolocation cues generated by moving a pair of receivers aboard a model sensor head are investigated. In the first case, it is supposed that a common 3-D echolocation principle employed by all bats is the creation of alternative viewing perspectives, and that constant frequency (CF) echolocators use pinna movement rather than morphology to alter the acoustic axes of their perceptual systems. Alternatively, it is possible rhinolophids and hipposiderids move their ears to create dynamic cues—in the form of frequency and amplitude modulations—which vary systematically with target elevation. Here the use of binaural and monaural timing cues derived from amplitude modulated echo envelopes are investigated. In this case, pinna mobility provides an echolocator with a mechanism for creating dramatic temporal cues for directional sensing which, unlike interaural timing differences, do not degrade with head size