ing away from the specific coding of the spinal fields, the examples from neurobiology provide the framework for a motor control system based on a small number of additive primitives (or basis behaviors) sufficient for a rich output movement repertoire. Our previous work (Matari'c 1995, Matari'c 1997), inspired by the same biological results, has successfully applied the idea of basis behaviors to control of mobile robots 6 by fitting it directly into the modular behavior-based control paradigm. Applictions of schema theory (Arbib 1992) to behavior-based mobile robots (Arkin 1987) have employed a similar notion of composable behaviors, stemming from foundations in neuroscience (Arbib 1981, Arbib 1989). The idea of using such primitives for articulator control has been recently studied in robotics. Williamson (1996) and Marjanovi'c, Scassellati & Williamson (1996) developed a 6 DOF (degrees of freedom) robot arm controller. While in the biological and mobile robotics work primitives c...

Neurophysiological evidence is described, showing that some neurons in the macaque temporal cortical visual areas have responses that are invariant with respect to the position, size and view of faces and objects, and that these neurons show rapid processing and rapid learning. A theory is then described of how such invariant representations may be produced in a hierarchically organized set of visual cortical areas with convergent connectivity. The theory proposes that neurons in these visual areas use a modified Hebb synaptic modification rule with a short-term memory trace to capture whatever can be captured at each stage that is invariant about objects as the object changes in retinal position, size, rotation and view. Simulations are then described which explore the operation of the architecture. The simulations show that such a processing system can build invariant representations of objects.

This paper describes experiments performed with forty subjects wearing an eye-tracker and watching and imitating videos of finger, hand, and arm movements. For all types of stimuli, the subjects tended to fixate on the hand, regardless of whether they were imitating or just watching. The results lend insight into the connection between visual perception and motor control, suggesting that: 1) people analyze human arm movements largely by tracking the hand or the end-point, even if the movement is performed with the entire arm, and 2) when imitating, people use internal innate and learned models of movement, possibly in the form of motor primitives, to recreate the details of whole-arm posture and movement from end-point trajectories. Keywords: Perceptual-motor interaction; Eye-tracking; Movement imitation Theme: Motor Systems and Sensorimotor Integration Topic: Control of Posture and Movement 1 Introduction Imitation is one of the most ubiquitous forms of human learning. What appea...

A variety of cell types exist in the temporal cortex providing high-level visual descriptions of bodies and their movements. We have investigated the sensitivity of such cells to different viewing conditions to determine the frame(s) of reference utilized in processing. The responses of the majority of cells in the upper bank of the superior temporal sulcus (areas TPO and PGa) found to be sensitive to static and dynamic information about the body were selective for one perspective view (e.g. right profile, reaching right or walking left). These cells can be considered to provide viewer-centred descriptions because they depend on the observer's vantage point. Viewer-centred descriptions could be used in guiding behaviour. They could also be used as an intermediate step for establishing view-independent responses of other cell types which responded to many or all perspective views selectively of the same object (e.g. head) or movement. These cells have the properties of object-centred descriptions, where the object viewed provides the frame of reference for describing the disposition of object parts and movements (e.g. head on top of shoulders, reaching across the body, walking forward 'following the nose'). For some cells in the lower bank of the superior temporal sulcus (area TEa) the responses to body movements were related to the object or goal of the movements (e.g. reaching for or walking towards a specific place). This goal-centred sensitivity to interaction allowed the cells to be selectively activated in situations where human subjects would attribute causal and intentional relationships.

Neurophysiological and psychophysical research has provided convincing evidence that the shape of complex stationary objects is neurally encoded in representations that are based on learned two-dimensional prototypical views. A number of neural models have been proposed that account for this fact, and which also model correctly the invariance properties of neurons in the ventral pathway with respect to spatial position and scaling of the recognized objects. We have developed a model for the recognition of biological motion that exploits similar neural principles. The proposed model is compatible with a number of well-known neurophysiological facts and reproduces a variety of psychophysical results. A number of predictions is derived from the model that can be tested psychophysically, neurophysiologically, and in FMRI experiments. 1 Introduction Experimental research has provided insights in the neural basis of the recognition of complex stationary objects, like faces. A cent...

Humans can perceive the motion of living beings from very impoverished stimuli like point-light displays. How the visual system achieves the robust generalization from normal to point-light stimuli remains an unresolved question. We present evidence on multiple levels demonstrating that this generalization might be accomplished by an extraction of simple midlevel optic flow features within coarse spatial arrangement, potentially exploiting relatively simple neural circuits: (1) A statistical analysis of the most informative mid-level features reveals that normal and point-light walkers share very similar dominant local optic flow features. (2) We devise a novel point-light stimulus (critical features stimulus) that contains these features, and which is perceived as a human walker even though it is inconsistent with the skeleton of the human body. (3) A neural model that extracts only these critical features accounts for substantial recognition rates for strongly degraded stimuli. We conclude that recognition of biological motion might be accomplished by detecting mid-level optic flow features with relatively coarse spatial localization. The computationally challenging reconstruction of precise position information from degraded stimuli might not be required.

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It has been proposed that actions are intrinsically linked to perception [James, W. (1890). Principles of psychology. New York, NY, USA: Holt; Jeannerod M. (1994). The representing brain – neural correlates of motor intention and imagery. Behavioural Brain Sciences, 17, 187–202; Prinz, W. (1997). Perception and action planning. European Journal of Cognitive Psychology, 9, 129–154]. The idea behind these theories is that observing, imagining or in any way representing an action excites the motor programs used to execute that same action. There is neurophysiological evidence that neurons in premotor cortex of monkeys respond both during movement execution and during the observation of goal-directed action (‘mirror neurons’). In humans, a proportion of the brain regions involved in executing actions are activated by the mere observation of action (the ‘mirror system’). In this paper, we briefly review recent empirical studies of the mirror system, and discuss studies demonstrating interference effects between observed and executed movements. This interference, which might be a form of ‘motor contagion’, seems to arise specifically from the observation of biological movements, whether or not these movements are goal-directed. We suggest that this crude motor contagion is the first step in a more sophisticated predictive system that allows us to infer goals from the observation of actions.

The paper provides a summary of our recent research on preverbal infants (using violation-of-expectation and observational learning paradigms) demonstrating that one-year-olds interpret and draw systematic inferences about other's goal-directed actions, and can rely on such inferences when imitating other's actions or emulating their goals. To account for these findings it is proposed that oneyear -olds apply a non-mentalistic action interpretational system, the 'teleological stance' that represents actions by relating relevant aspects of reality (action, goal-state, and situational constraints) through the principle of rational action, which assumes that actions function to realize goal-states by the most efficient means available in the actor's situation. The

The inferior temporal cortex (IT) of monkeys is thoughttoplay an essential role in visual object recognition.