Knowledge-based vision and simple visual machines

The vast majority of work in machine vision emphasizes the representation of perceived objects and events: it is these internal representations that incorporate the 'knowledge' in knowledge-based vision or form the 'models' in model-based vision. In this paper, we discuss simple machine vision systems developed by artificial evolution rather than traditional engineering design techniques, and note that the task of identifying internal representations within such systems is made difficult by the lack of an operational definition of representation at the causal mechanistic level. Consequently, we question the nature and indeed the existence of representations posited to be used within natural vision systems (i.e. animals). We conclude that representations argued for on a priori grounds by external observers of a particular vision system may well be illusory, and are at best place-holders for yet-to-be-identified causal mechanistic interactions. That is, applying the knowledge-based vision approach in the understanding of evolved systems (machines or animals) may well lead to theories and models that are internally consistent, computationally plausible, and entirely wrong

Behavioural and sensory aspects of predation in -mustelids: studies on the sensory capabilities of the weasel, Mustela nivalis L. And the polecat, Mustela putorlus L., with particular reference to predatory behaviour

The relative importance of vision, audition and olfaction to weasels and polecats was determined by training the predators to find a mouse located in a predator-proof container within a small arena. The diversity of sensory information available to the predators had an effect on the time taken to find the mouse with this being shorter when three senses could be used compared to when one sensory modality was available. Vision and olfaction (air-borne scent) were equivalent, with audition being less important. The mouse was found quicker using substrate-scent cues than with air-borne olfactory cues. There was no difference in the relative importance of the senses between the predators. The removal of movement cues had a significant effect on the behaviour of the weasels. The visual movement discrimination ability of both species was investigated using a horizontally-moving spot on a cathode-ray oscilloscope screen. Thresholds were determined for the discrimination of the direction of a fast-moving stimulus and were equivalent in the polecat and weasel. The mean threshold for polecats was 292cms(^-1) and for weasels was 267cms(^-1). The movement detection ability of the weasel was consistent over a range of stimulus radiant intensities (35.4-2.0x10(^5) µWsteradian(^-l)) and discrimination distances (10-50cm), although there was a slight decrease in threshold at the furthest distance used and when the distance traversed by the stimulus was short. A relative velocity discrimination task was devised in which polecats were trained to discriminate differences in speed between identical objects moving in opposite directions in the horizontal plane. They could detect velocity differences of 20% and showed a tendency to select the slower-moving of the two stimuli. Polecats and weasels do not specialize in the use of a particular distance sense to locate potential prey. In terms of their movement detection ability and the relative importance of vision they are intermediate between strictly nocturnal and diurnal species, which is probably attributable to their predominately crepuscular activity pattern

The Effects of Forebrain Ablations on Some Behaviors in \u3ci\u3eXenopus Laevis\u3c/i\u3e

In order to further elucidate the hypothesis that the telencephalon of ectothermic vertebrates functions primarily as a non-specific arousal mechanism, facilitating lower brain areas, (the Arousal Hypothesis) the South African clawed frog, Xenoous laevis, was studied in four behavioral situations before and after telencephalon ablation, olfactory bulb ablation or sham surgery. Particular attention was paid to measurements of the temporal aspects of the behaviors studied. The behaviors studied were: 1. Habituation to an acoustic-vibratory stimulus 2. The optomotor response 3. Escape from shallow water 4. Feeding behavior In the habituation experiment no changes were found in the number of responses oer session, the strength of the .responses or in the strength of the initial responses. Certain telencephalon-ablated individuals, however, showed a marked decrease in the number of responses to habituate which was not seen in any of the animals in the other groups. There were no changes in optomotor responses to moving vertical black and white stripes which were attributable to the operations. In an experiment involving escape from shallow water into deeper water, there was a significant increase in the length of time to escape in the telencenhalon ablated-group. In the feeding experiment, it was found that ablations of the telencephalon eliminated feeding behavior. It is concluded that \u27arousal,\u27 defined as that function regulating frequency and other temporal aspects of behavior (but not response strength) is the major function of the forebrain in Xenopus laevis. The telencephalon, however, does not play a major role in relatively simple behaviors

Direct extraction of tau information for use in ego-motion

Avoidance collisions with obstacles is a critical function of any autonomous vehicle. This thesis considers the problem of utilising information about time to contact available in the ambient optic array. Motion-from-smear (W.G. Chen, Nandhakumar, & Martin, 1994; Geisler, 1999) is used to aid judgment of global tau (Kaiser & Mowafy, 1993; D. N. Lee, 1974, 1976). A robotic system employing motion-from­ smear was tested in a task requiring judgment of global tau and found to provide adequate accuracy (mean error= -0.52s) but poor precision (SD= 1.52s). Motion­ from-smear is also discussed with respect to its application to a novel formulation for composite tau and a use of motion parallax in stair descent

Frog Spinal Motoneurons: Their Supraspinal Synaptic Input and Anatomical Localization

Techniques were developed for maintaining a bullfrog spinal cord in situ and for recording intracellularly from lumbar motoneurons in this preparation. Fibers in the contralateral and ipsilateral lateral funiculi of the spinal cord which originate at or above the calamus scriptorius were found to produce EPSPs in flexor and extensor motoneurons innervating the hindlimb. These EPSPs appeared to be generated monosynaptically on the somas and proximal dendrites of the motoneurons. Chromatolysis was used to map the location of motoneurons· innervating hindlimb muscles in the bullfrog, Rana catesbiana. These motoneurons were located in the dorsolateral cell column of the ventral horn, but not in the ventromedial column. A somatotopic organization was found, with motoneurons innervating proximal muscles located ventrally and rostrally to those innervating distal muscles. A functional organization was found, in which motoneurons controlling the flexor muscles around any joint were located rostrally to those controlling the extensors. Electrophysiological mapping gave results consistent with this arrangement

Does corticosterone regulate the onset of breeding in free-living birds?: The CORT-Flexibility Hypothesis and six potential mechanisms for priming corticosteroid function

© 2015 Published by Elsevier Inc. For many avian species, the decision to initiate breeding is based on information from a variety of environmental cues, including photoperiod, temperature, food availability, and social interactions. There is evidence that the hormone corticosterone may be involved in delaying the onset of breeding in cases where supplemental cues, such as low food availability and inclement weather, indicate that the environment is not suitable. However, not all studies have found the expected relationships between breeding delays and corticosterone titers. In this review, we present the hypothesis that corticosterone physiology mediates flexibility in breeding initiation (the CORT-Flexibility Hypothesis ), and propose six possible corticosterone-driven mechanisms in pre-breeding birds that may delay breeding initiation: altering hormone titers, negative feedback regulation, plasma binding globulin concentrations, intracellular receptor concentrations, enzyme activity and interacting hormone systems. Based on the length of the breeding season and species-specific natural history, we also predict variation in corticosterone-regulated pre-breeding flexibility. Although few studies thus far have examined mechanisms beyond plasma hormone titers, the CORT-Flexibility Hypothesis is grounded on a solid foundation of research showing seasonal variation in the physiological stress response and knowledge of physiological mechanisms modulating corticosteroid effects. We propose six possible mechanisms as testable and falsifiable predictions to help clarify the extent of HPA axis regulation of the initiation of breeding