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Weakly electric fish are able to detect and localize prey based on microvolt-level perturbations in the fish's self-generated electric field. In natural environments, weak prey-related signals are embedded in much stronger electrosensory background noise. To better characterize the signal and background components associated with natural electrolocation(More)
This paper describes a six-legged robot based on the features of an agile insect, the American cockroach, Periplaneta americana. The robot is designed with insect-like leg structure and placement, and actuators that mimic muscles. A test leg is also described that shows how sensory feedback can serve as the basis of the control system for the robot in order(More)
Two functional types of nicotinic acetylcholine receptors (nAChRs) are expressed when human embryonic kidney cells are permanently transfected with equal amounts of human alpha4 and beta2 subunit cDNAs. Most (82%) of these nAChRs exhibit an EC(50) of 74 +/- 6 microM for ACh, a much lower sensitivity than the remaining fraction (EC(50) of 0.7 +/- 0.4 microM)(More)
We prepared concatamers of alpha4 and beta2 subunits for human nicotinic acetylcholine receptors (AChRs), in which the C terminus of alpha4 was linked to the N terminus of beta2, or vice versa, via a tripeptide sequence repeated 6 or 12 times, and expressed them in Xenopus oocytes. Linkage did not substantially alter channel amplitude or channel(More)
A simple model of spike generation is described that gives rise to negative correlations in the interspike interval (ISI) sequence and leads to long-term spike train regularization. This regularization can be seen by examining the variance of the kth-order interval distribution for large k (the times between spike i and spike i + k). The variance is much(More)
abstract We characterized the functional and molecular properties of nicotinic acetylcholine receptors (AChRs) expressed by IMR-32, a human neuroblastoma cell line, and compared them to human ␣ 3 AChRs expressed in stably transfected human embryonic kidney (HEK) cells. IMR-32 cells, like neurons of autonomic gan-glia, have been shown to express ␣ 3, ␣ 5, ␣(More)
Active sensing organisms, such as bats, dolphins, and weakly electric fish, generate a 3-D space for active sensation by emitting self-generated energy into the environment. For a weakly electric fish, we demonstrate that the electrosensory space for prey detection has an unusual, omnidirectional shape. We compare this sensory volume with the animal's motor(More)
Black ghost knifefish (Apteronotus albifrons) are nocturnal, weakly electric fish that feed on insect larvae and small crustaceans in the freshwater rivers of South America. In the absence of visual cues, prey detection and localization in this species is likely to rely on weak electrosensory and mechanosensory cues generated by the prey. In this paper, a(More)