Papers by B. Mitchinson
... raised (or addressed) by current biological data, and guiding us in the design of future ... ... more ... raised (or addressed) by current biological data, and guiding us in the design of future ... more complex WPG models in order to investigate the impact of different modula-tion strategies. ... We use, instead, an algorithm we call 'Snake', which takes a bio-inspired approach, causing ...
2013 IEEE International Conference on Robotics and Automation, 2013
Lecture Notes in Computer Science, 2011
A general problem in robotics is how to best utilize sensors to classify the robot’s environment.... more A general problem in robotics is how to best utilize sensors to classify the robot’s environment. The BIOTACT project (BIOmimetic Technology for vibrissal Active Touch) is a collaboration between biologists and engineers that has led to many distinctive robots with artificial whisker sensing capabilities. One problem is to construct classifiers that can recognize a wide range of whisker sensations rather than constructing different classifiers for specific features. In this article, we demonstrate that a stationary naive Bayes classifier can perform such a general classification by applying it to various robot experiments. This classifier could be a key component of a robot able to learn autonomously about novel environments, where classifier properties are not known in advance.
PLoS Computational Biology, 2013
Spatial attention is most often investigated in the visual modality through measurement of eye mo... more Spatial attention is most often investigated in the visual modality through measurement of eye movements, with primates, including humans, a widely-studied model. Its study in laboratory rodents, such as mice and rats, requires different techniques, owing to the lack of a visual fovea and the particular ethological relevance of orienting movements of the snout and the whiskers in these animals. In recent years, several reliable relationships have been observed between environmental and behavioural variables and movements of the whiskers, but the function of these responses, as well as how they integrate, remains unclear. Here, we propose a unifying abstract model of whisker movement control that has as its key variable the region of space that is the animal's current focus of attention, and demonstrate, using computer-simulated behavioral experiments, that the model is consistent with a broad range of experimental observations. A core hypothesis is that the rat explicitly decodes the location in space of whisker contacts and that this representation is used to regulate whisker drive signals. This proposition stands in contrast to earlier proposals that the modulation of whisker movement during exploration is mediated primarily by reflex loops. We go on to argue that the superior colliculus is a candidate neural substrate for the siting of a head-centred map guiding whisker movement, in analogy to current models of visual attention. The proposed model has the potential to offer a more complete understanding of whisker control as well as to highlight the potential of the rodent and its whiskers as a tool for the study of mammalian attention.
IEEE Transactions on Neural Networks, 2000
In this paper, we present two versions of a hardware processing architecture for modeling large n... more In this paper, we present two versions of a hardware processing architecture for modeling large networks of leaky-integrate-and-fire (LIF) neurons; the second version provides performance enhancing features relative to the first. Both versions of the architecture use fixed-point arithmetic and have been implemented using a single field-programmable gate array (FPGA). They have successfully simulated networks of over 1000 neurons configured using biologically plausible models of mammalian neural systems. The neuroprocessor has been designed to be employed primarily for use on mobile robotic vehicles, allowing bio-inspired neural processing models to be integrated directly into real-world control environments. When a neuroprocessor has been designed to act as part of the closed-loop system of a feedback controller, it is imperative to maintain strict real-time performance at all times, in order to maintain integrity of the control system. This resulted in the reevaluation of some of the architectural features of existing hardware for biologically plausible neural networks (NNs). In addition, we describe a development system for rapidly porting an underlying model (based on floating-point arithmetic) to the fixed-point representation of the FPGA-based neuroprocessor, thereby allowing validation of the hardware architecture. The developmental system environment facilitates the cooperation of computational neuroscientists and engineers working on embodied (robotic) systems with neural controllers, as demonstrated by our own experience on the Whiskerbot project, in which we developed models of the rodent whisker sensory system.
... [6] B. Mitchinson, T. Chan, J. Chambers, MJ Pearson, MD Humphries, CW Fox, K. Gurney and TJ P... more ... [6] B. Mitchinson, T. Chan, J. Chambers, MJ Pearson, MD Humphries, CW Fox, K. Gurney and TJ Prescott, (In press). BRAHMS: Novel middleware for integrated systems computation. ... Autonomous Robots, 26:223-239. [10] M. Evans, CW Fox, MJ Pearson and TJ Prescott. ...
... tasks: gap measurement (Krupa, Matell, Brisben, Oliveira, & Nicolelis, 2001), gap jum... more ... tasks: gap measurement (Krupa, Matell, Brisben, Oliveira, & Nicolelis, 2001), gap jumping (Hutson & Masterton, 1986; Jenkinson & Glickstein, 2000; Richardson, 1909), measuring angular position along the sweep of the whisker (Knutsen, Pietr, & Ahissar, 2006; Mehta, Whitmer ...
Natural Touch by B. Mitchinson
Scholarpedia, 2011
Tactile hair, or vibrissae, are a mammalian characteristic found on many mammals (Ahl, 1986). Vib... more Tactile hair, or vibrissae, are a mammalian characteristic found on many mammals (Ahl, 1986). Vibrissae differ from ordinary (pelagic) hair by being longer and thicker, having large follicles containing blood-filled sinus tissues, and by having an identifiable representation in the somatosensory cortex. Vibrissae are found on various parts of the body, but those most frequently studied are the facial or mystacial vibrissae, also called whiskers. Long facial whiskers, or macrovibrissae, are found in many mammalian species, projecting outwards and forwards from the snout of the animal to form a tactile sensory array that surrounds the head. For example, in rats, the macrovibrissae form a two-dimensional grid of five rows on each side of the snout, each row containing between five and nine whiskers ranging between ~15 and ~50 mm in length (see Figure 1 for illustration). The macrovibrissae of many rodents and some other species can move back and forth at high-speed thus explaining the term "vibrissa" which derives from the Latin "vibrio" meaning to vibrate.
Proceedings of the Royal Society B: Biological Sciences, 2007
Rats sweep their facial whiskers back and forth to generate tactile sensory information through c... more Rats sweep their facial whiskers back and forth to generate tactile sensory information through contact with environmental structure. The neural processes operating on the signals arising from these whisker contacts are widely studied as a model of sensing in general, even though detailed knowledge of the natural circumstances under which such signals are generated is lacking. We used digital video tracking and wireless recording of mystacial electromyogram signals to assess the effects of whisker–object contact on whisking in freely moving animals exploring simple environments. Our results show that contact leads to reduced protraction (forward whisker motion) on the side of the animal ipsilateral to an obstruction and increased protraction on the contralateral side. Reduced ipsilateral protraction occurs rapidly and in the same whisk cycle as the initial contact. We conclude that whisker movements are actively controlled so as to increase the likelihood of environmental contacts while constraining such interactions to involve a gentletouch. That whisking pattern generation is under strong feedback control has important implications forunderstanding the nature of the signals reaching upstream neural processes.
Journal of Neurophysiology, Feb 1, 2009
Animals actively regulate the position and movement of their sensory systems toboost the quality ... more Animals actively regulate the position and movement of their sensory systems toboost the quality and quantity of the sensory information they obtain.The rat vibrissal system is recognized to be an important model system in which to investigate such “active sensing” capabilities. The current study used high-speed video analysis to investigate whisker movements in untrained, freely moving rats encountering unexpected,vertical surfaces. A prominent feature of rat vibrissal movement is therepeated posterior–anterior sweep of the whiskers in which the mac-rovibrissae are seen to move largely in synchrony. Here we show thata second significant component of whisking behavior is the size of thearc, or “spread,” between the whiskers. Observed spread is shown tovary over the whisk cycle and to substantially decrease during explo-ration of an unexpected surface. We further show that the timing of whisker movements is affected by surface contact such that 1) thewhiskers rapidly cease forward protraction following an initial, unex-pected contact, and may do so even more rapidly following contactwith the same surface in the subsequent whisk cycle, and 2) retractionvelocity is reduced following this latter contact, leading to longersecond-contact durations. This evidence is taken to support two hy-potheses: 1) that the relative velocities of different whiskers may beactively controlled by the rat and 2) that control of whisker velocity and timing may serve to increase the number and duration of whisker–surface contacts while ensuring that such contacts are made with alight touch.
Developmental Psychobiology, 2012
Adult rats sweep their large facial whiskers (macrovibrissae) back and forth in a rhythmic patter... more Adult rats sweep their large facial whiskers (macrovibrissae) back and forth in a rhythmic pattern known as “whisking”. Here we examine how these whisker movements develop in relation to other aspects of exploratory behavior, particularly locomotion. We analyzed 963 high-speed video recordings of neonatal rats, from P1 (Post-natal day 1) to P21, and measured the emergence of whisker control and of head, body, and limb movements. Prior to P11, whisker movements were largely limited to unilateral retractions accompanying head turns. Between P11 and P13 bilateral whisking emerged alongside increased forward locomotion and improved control of the head. Contact-induced modulations of whisking symmetry, synchrony and whisker spread emerge shortly thereafter but continue until P18, coinciding with the emergence of adult-like locomotion patterns such as rearing. Overall, whisking develops alongside increasing locomotor competence indicating that active vibrissal sensing plays a important role in the exploratory behavior of the developing animal.
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Papers by B. Mitchinson
Natural Touch by B. Mitchinson