Human hip–ankle coordination emerging from multisensory feedback control

Human sensorimotor control involves inter-segmental coordination to cope with the complexity of a multi-segment system. The combined activation of hip and ankle muscles during upright stance represents the hip–ankle coordination. This study postulates that the coordination emerges from interactions on the sensory levels in the feedback control. The hypothesis was tested in a model-based approach that compared human experimental data with model simulations. Seven subjects were standing with eyes closed on an anterior–posterior tilting motion platform. Postural responses in terms of angular excursions of trunk and legs with respect to vertical were measured and characterized using spectral analysis. The presented control model consists of separate feedback modules for the hip and ankle joints, which exchange sensory information with each other. The feedback modules utilize sensor-derived disturbance estimates rather than ‘raw’ sensory signals. The comparison of the human data with the simulation data revealed close correspondence, suggesting that the model captures important aspects of the human sensory feedback control. For verification, the model was re-embodied in a humanoid robot that was tested in the human laboratory. The findings show that the hip–ankle coordination can be explained by interactions between the feedback control modules of the hip and ankle joints.     

Brain-inspired distributed cognitive architecture

In this paper we present a brain-inspired cognitive architecture that incorporates sensory processing, classification, contextual prediction, and emotional tagging. The cognitive architecture is implemented as three modular web-servers, meaning that it can be deployed centrally or across a network for servers. The experiments reveal two distinct operations of behaviour, namely high- and low-salience modes of operations, which closely model attention in the brain. In addition to modelling the cortex, we have demonstrated that a bio-inspired architecture introduced processing efficiencies. The software has been published as an open source platform, and can be easily extended by future research teams. This research lays the foundations for bio-realistic attention direction and sensory selection, and we believe that it is a key step towards achieving a bio-realistic artificial intelligent system.     

Testosterone fails to reverse spatial memory decline in aged rats and impairs retention in young and middle-aged animals

Recently, the vasopressin (AVP) innervation in the rat brain was shown to be restored in senescent rats following long-term testosterone administration. In order to investigate whether this restoration is accompanied by an improvement in learning and memory, both sham- and testosterone-treated young (4.5 months), middle-aged (20 months), and aged (31 months) male Brown-Norway rats were tested in a Morris water maze. All animals learned to localize a cued platform equally well, indicating that the ability to learn this task was not affected by sensory, motoric, or motivational changes with aging or testosterone treatment. There were no significant differences in retention following cue training. Subsequent training with a hidden platform in the opposite quadrant of the pool (place training) revealed impaired spatial learning in middle-aged and aged animals. Retention following place training was significantly impaired in the sham-treated aged rats as compared with sham-treated young rats. Testosterone treatment did not improve spatial learning nor retention of spatial information, but, on the contrary, impaired retention in young and middle-aged animals. The present results confirm earlier reports on an impairment of spatial learning and memory in senescent rats but fail to support a role of decreased plasma testosterone levels and central AVP innervation in this respect.     

Robot studies on saccade-triggered visual prediction

Three robot studies on visual prediction are presented. In all of them, a visual forward model is used, which predicts the visual consequences of saccade-like camera movements. This forward model works by remapping visual information between the pre- and postsaccadic retinal images; at an abstract modeling level, this process is closely related to neurons whose visual receptive fields shift in anticipation of saccades. In the robot studies, predictive remapping is used (1) in the context of saccade adaptation, to reidentify target objects after saccades are carried out; (2) for a model of grasping, in which both fixated and non-fixated target objects are processed by the same foveal mechanism; and (3) in a computational architecture for mental imagery, which generates “gripper appearances” internally without real sensory inflow. The robotic experiments and their underlying computational models are discussed with regard to predictive remapping in the brain, transsaccadic memory, and attention. The results confirm that visual prediction is a mechanism that has to be considered in the design of artificial cognitive agents and the modeling of information processing in the human visual system.     

Influence of Destabilization on the Temporal Characteristics of lquot;Volitionalrquot; Stepping

Previous work suggests that there may be fundamental differences between compensatory stepping responses evoked by postural perturbation and visually cued "volitional" stepping (e.g., gait initiation). In contrast to visual cueing, postural destabilization evokes an array of sensory inputs that are intrinsically linked to the mobilization of rapid compensatory responses. The hypothesis examined in this study was that this fundamental difference would lead to distinct changes in the temporal characteristics of the stepping response. Six healthy young adults were instructed to step quickly in response to either visual cueing or anterioposterior platform motion. Both forward and backward stepping responses were characterized, using measures of vertical ground reaction force. A stereotypical temporal patterning of the stepping response occurred in both stimulus conditions and both directions of stepping, and anticipatory postural adjustments were evident in all trials. However, postural destabilization led to a more rapid initiation and execution of the temporal pattern, in comparison with visually cued responses. The most pronounced effect was seen in the duration of the response, which was reduced by a factor of two, with approximately proportional foreshortening of both the preparatory and swing phases. The results suggest that sensory information conveying a state of instability has a distinct influence on the characteristics of a subsequent stepping reaction. The persistence of the anticipatory postural adjustments suggests that the failure to see this element of the response in previous studies may reflect fundamental differences between volitional and unplanned compensatory stepping.     

Influence of Destabilization on the Temporal Characteristics of “Volitional” Stepping

Previous work suggests that there may be fundamental differences between compensatory stepping responses evoked by postural perturbation and visually cued “volitional” stepping (e.g., gait initiation). In contrast to visual cueing, postural destabilization evokes an array of sensory inputs that are intrinsically linked to the mobilization of rapid compensatory responses. The hypothesis examined in this study was that this fundamental difference would lead to distinct changes in the temporal characteristics of the stepping response. Six healthy young adults were instructed to step quickly in response to either visual cueing or anterioposterior platform motion. Both forward and backward stepping responses were characterized, using measures of vertical ground reaction force. A stereotypical temporal patterning of the stepping response occurred in both stimulus conditions and both directions of stepping, and anticipatory postural adjustments were evident in all trials. However, postural destabilization led to a more rapid initiation and execution of the temporal pattern, in comparison with visually cued responses. The most pronounced effect was seen in the duration of the response, which was reduced by a factor of two, with approximately proportional foreshortening of both the preparatory and swing phases. The results suggest that sensory information conveying a state of instability has a distinct influence on the characteristics of a subsequent stepping reaction. The persistence of the anticipatory postural adjustments suggests that the failure to see this element of the response in previous studies may reflect fundamental differences between volitional and unplanned compensatory stepping.     

The role of haptic versus visual volume cues in the size-weight illusion

Three experiments establish the size-weight illusion as a primarily haptic phenomenon, despite its having been more traditionally considered an example of vision influencing haptic processing. Experiment 1 documents, across a broad range of stimulus weights and volumes, the existence of a purely haptic size-weight illusion, equal in strength to the traditional illusion. Experiment 2 demonstrates that haptic volume cues are both sufficient and necessary-for a full-strength illusion. In contrast, visual volume cues are merely sufficient, and produce a relatively weaker effect. Experiment 3 establishes that congenitally blind subjects experience an effect as powerful as that Of blindfolded sighted observers, thus demonstrating that visual imagery is also unnecessary for a robust size-weight illusion. The results are discussed in terms of their implications for both sensory and cognitive theories of the size-weight illusion. Applications of this work to a human factors design and to sensor-based systems for robotic manipulation are also briefly considered.     

Out of sight,out of mind? Relations between visual acuity and cognition

Prior research has established significant relations between measures of sensory ability and cognitive function in adults of different ages, and several explanations for this relation have been proposed. One explanation is that sensory abilities restrict cognitive processing, a second is that cognitive abilities influence assessments of sensory ability, and a third is that both sensory function and cognition are affected by a common, potentially age-based, third factor. These explanations were investigated using mediation and moderation analyses, with near visual acuity as the sensory measure and scores on visual speed tests and auditory memory tests as the cognitive measures. Measures of visual acuity, speed, and memory were obtained from three moderately large samples, two cross-sectional (N?=?380, N?=?4,779) and one longitudinal (N?=?2,258), with participants ranging from 18 to 90 years of age. The visual acuity and cognitive measures had different age trajectories, and the visual acuity–cognition relations were similar in each 5-year age band. The results suggest that the age-related differences and changes in near visual acuity are unlikely to contribute to the age-related differences and changes in speed and memory measures.     

Commanding the direction of passive whole-body rotations facilitates egocentric spatial updating

In conditions of slow passive transport without vision, even tenuous inertial signals from semi-circular canals and the haptic-kinaesthetic system should provide information about changes relative to the environment provided that it is possible to command the direction of the body's movements voluntarily. Without such control, spatial updating should be impaired because incoming signals cannot be compared to the expected sensory consequences provided by voluntary command. Participants were seated in a rotative robot (Robuter) and learnt the positions of five objects in their surroundings. They were then blindfolded and assigned either to the active group (n=7) or to the passive group (n=7). Members of the active group used a joystick to control the direction of rotation of the robot. The acceleration (25 degrees /s2) and plateau velocity (9 degrees /s) were kept constant. The participants of the passive group experienced the same stimuli passively. After the rotations, the participants had to point to the objects whilst blindfolded. Participants in the active group significantly outperformed the participants in the passive group. Thus, even tenuous inertial cues are useful for spatial updating in the absence of vision, provided that such signals are integrated as feedback associated with intended motor command.     

The TROCA Project: An autonomous transportation robot controlled by a cognitive architecture

Autonomous mobile robots emerged as an important kind of transportation system in warehouses and factories. In this work, we present the use of MECA cognitive architecture in the development of an artificial mind for an autonomous robot responsible for multiple tasks, including transportation of packages along a factory floor, environment exploration, warehouse inventory, its internal energy management, self-monitoring and dealing with human operators and other robots. The present text provides a detailed specification for the architecture and its software implementation. Future work will present the simulation results under different configurations, together with a detailed analysis of the architecture performance and its generalization for autonomous robot control.     

SLOT: A research platform for investigating multimodal communication

In this article, we present the spatial logistics task (SLOT) platform for investigating multimodal communication between 2 human participants. Presented are the SLOT communication task and the software and hardware that has been developed to run SLOT experiments and record the participants’ multimodal behavior. SLOT offers a high level of flexibility in varying the context of the communication and is particularly useful in studies of the relationship between pen gestures and speech. We illustrate the use of the SLOT platform by discussing the results of some early experiments. The first is an experiment on negotiation with a one-way mirror between the participants, and the second is an exploratory study of automatic recognition of spontaneous pen gestures. The results of these studies demonstrate the usefulness of the SLOT platform for conducting multimodal communication research in both human-human and human-computer interactions.     

Depth perception in Mongolian gerbils (Meriones unguiculatus) and spiny mice (Acomys russatus and A. cahirinus)

Depth perception in gerbils and spiny mice was studied with a modified visual cliff which varied the height of a platform from 5.08 cm to 25.4 cm and presented animals with an apparent drop-off to a patterned or a white field. Time to descend from the platform and orienting response frequency were recorded. For gerbils neither measure varied significantly between the platforms. Both Acomys species increased descent time and orienting response frequency as platform height increased. The results suggest that both gerbils and spiny mice can perceive depth, though there appears to be a difference between the species' use of sensory cues in descending from a visual cliff. The spiny mice appear to rely more on visual cues than do the gerbils. The data also reveal subtle behavioral differences between the Acomys species that may relate to their successful sympatry. The results are discussed by alluding to ecological differences between these species in their natural habitats.     

Causal cognitive architecture 1: Integration of connectionist elements into a navigation-based framework

The brain-inspired Causal Cognitive Architecture 1 (CCA1) tightly integrates the sensory processing capabilities found in neural networks with many of the causal abilities found in human cognition. Causality emerges not from a central controlling stored program but directly from the architecture. Sensory input vectors are processed by robust association circuitry and then propagated to a navigational temporary map. Instinctive and learned objects and procedures are applied to the same temporary map, with a resultant navigation signal obtained. Navigation can similarly be for the physical world as well as for a landscape of higher cognitive concepts. There is good explainability for causal decisions. A simulation of the CCA1 controlling a search and rescue robot is presented with the goal of finding and rescuing a lost hiker within a grid world. A simulation of the CCA1 controlling a repair robot is presented that can predict the movement of a series of gears.     

The CORTEX cognitive robotics architecture: Use cases

CORTEX is a cognitive robotics architecture inspired by three key ideas: modularity, internal modelling and graph representations. CORTEX is also a computational framework designed to support early forms of intelligence in real world, human interacting robots, by selecting an a priori functional decomposition of the capabilities of the robot. This set of abilities was then translated to computational modules or agents, each one built as a network of software interconnected components. The nature of these agents can range from pure reactive modules connected to sensors and/or actuators, to pure deliberative ones, but they can only communicate with each other through a graph structure called Deep State Representation (DSR). DSR is a short-term dynamic representation of the space surrounding the robot, the objects and the humans in it, and the robot itself. All these entities are perceived and transformed into different levels of abstraction, ranging from geometric data to high-level symbolic relations such as “the person is talking and gazing at me”. The combination of symbolic and geometric information endows the architecture with the potential to simulate and anticipate the outcome of the actions executed by the robot. In this paper we present recent advances in the CORTEX architecture and several real-world human-robot interaction scenarios in which they have been tested. We describe our interpretation of the ideas inspiring the architecture and the reasons why this specific computational framework is a promising architecture for the social robots of tomorrow.     

A low‐cost platform for eye‐tracking research: Using Pupil© in behavior analysis

Tracking eye movements is being increasingly recognized as a valuable source of information about stimulus control. So far, however, eye‐tracking research has suffered from accessibility issues, with expensive hardware and closed‐source software. In this article we review Pupil©, an eye‐tracking platform developed by Pupil Labs and that combines open‐source software with low‐cost hardware components. We offer concrete recommendations about Pupil use in stimulus‐control research and we show how the software can be extended to automatize the analysis of gaze data. Finally, we present the results of a study of visual discrimination and conditioned reinforcement conducted with Pupil, establishing the usefulness of this platform as a research tool in behavior analysis.     

Sensing sociality in dogs: what may make an interactive robot social?

This study investigated whether dogs would engage in social interactions with an unfamiliar robot, utilize the communicative signals it provides and to examine whether the level of sociality shown by the robot affects the dogs’ performance. We hypothesized that dogs would react to the communicative signals of a robot more successfully if the robot showed interactive social behaviour in general (towards both humans and dogs) than if it behaved in a machinelike, asocial way. The experiment consisted of an interactive phase followed by a pointing session, both with a human and a robotic experimenter. In the interaction phase, dogs witnessed a 6-min interaction episode between the owner and a human experimenter and another 6-min interaction episode between the owner and the robot. Each interaction episode was followed by the pointing phase in which the human/robot experimenter indicated the location of hidden food by using pointing gestures (two-way choice test). The results showed that in the interaction phase, the dogs’ behaviour towards the robot was affected by the differential exposure. Dogs spent more time staying near the robot experimenter as compared to the human experimenter, with this difference being even more pronounced when the robot behaved socially. Similarly, dogs spent more time gazing at the head of the robot experimenter when the situation was social. Dogs achieved a significantly lower level of performance (finding the hidden food) with the pointing robot than with the pointing human; however, separate analysis of the robot sessions suggested that gestures of the socially behaving robot were easier for the dogs to comprehend than gestures of the asocially behaving robot. Thus, the level of sociality shown by the robot was not enough to elicit the same set of social behaviours from the dogs as was possible with humans, although sociality had a positive effect on dog–robot interactions.     

Characteristics of Unintentional Movements by a Multijoint Effector

The authors explored the phenomenon of unintentional changes in the equilibrium state of a multijoint effector produced by transient changes in the external force. The subjects performed a position-holding task against a constant force produced by a robot and were instructed not to intervene voluntarily with movements produced by changes in the robot force. The robot produced a smooth force increase leading to a hand movement, followed by a dwell time. Then, the force dropped to its initial value leading to hand movement toward the initial position, but the hand stopped short of the initial position. The undershoot magnitude increased linearly with the peak hand displacement and exponentially with dwell time (time constant of about 1 s). For long dwell times, the hand stopped at about half the total distance to the initial position. The authors interpret the results as consequences of a drift of the referent hand coordinate. Our results provide support for back-coupling between the referent and actual body configurations during multijoint actions and produce the first quantitative analysis of this phenomenon. This mechanism can also explain the phenomena of slacking and force drop after turning visual feedback off during accurate force production task.     

Sensori-motor integration during stance: Time adaptation of control mechanisms on adding or removing vision

Sudden addition or removal of visual information can be particularly critical to balance control. The promptness of adaptation of stance control mechanisms is quantified by the latency at which body oscillation and postural muscle activity vary after a shift in visual condition. In the present study, volunteers stood on a force platform with feet parallel or in tandem. Shifts in visual condition were produced by electronic spectacles. Ground reaction force (center of foot pressure, CoP) and EMG of leg postural muscles were acquired, and latency of CoP and EMG changes estimated by t-tests on the averaged traces. Time-to-reach steady-state was estimated by means of an exponential model. On allowing or occluding vision, decrements and increments in CoP position and oscillation occurred within about 2 s. These were preceded by changes in muscle activity, regardless of visual-shift direction, foot position or front or rear leg in tandem. These time intervals were longer than simple reaction-time responses. The time course of recovery to steady-state was about 3 s, shorter for oscillation than position. The capacity of modifying balance control at very short intervals both during quiet standing and under more critical balance conditions speaks in favor of a necessary coupling between vision, postural reference, and postural muscle activity, and of the swiftness of this sensory reweighing process.     

The basis for choice reaction time slowing in Alzheimer's disease

Slowed reaction time has been suggested as an early feature of Alzheimer's disease (AD), but the basis for this slowing has not been established. Patients with mild AD were compared with controls on a choice reaction time task, both cued (CCRT) and uncued (CRT). Initial and 1-year followup data were analyzed both as mean reaction times and as parameters of a fitted two-component quantitative model (the ex-Gaussian model). Slowing of CRT proved to be a sensitive test for AD. Slowing was due to changes in both the sensory/motor and the decisional components of the CRT model. However, these changes were found in both AD and slower, older controls. The modeling of CRT in AD is discussed.