The mammalian hippocampal formation plays a critical role in efficient and flexible navigation. Hippocampal place cells exhibit spatial tuning, characterized by increased firing rates when an animal occupies specific locations in its environment. The mechanisms underlying the encoding of spatial information by hippocampal place cells remain not fully resolved. Evidence suggests that spatial preferences are shaped by multimodal sensory inputs. Yet, existing hippocampal-inspired models typically rely on a single sensory information source. Here, we developed a hippocampus-inspired model that combines motivational and spatial encoding and is based on the fundamental principle of biological autonomy that behavior serves a purpose. That is, in foraging tasks, an agent’s trajectories must be deployed considering the fact that the reward value of environmental stimuli is tied to the agent’s motivational state. In this paper, we introduce a "motivational hippocampal autoencoder" (MoHA) that integrates both interoceptive (motivational) and exteroceptive (visual) information. The MoHA model reproduces hippocampal firing correlates for different motivational states. We show that the representations of MoHA allow a synthetic agent to learn and deploy efficient trajectories in a foraging task, laying the foundation for self-regulated multipurpose reinforcement learning.

Although the primary function of excitatory-inhibitory (E-I) homeostasis is the maintenance of mean firing rates, the conjugation of multiple homeostatic mechanisms is thought to be pivotal to ensuring edge-of-bifurcation dynamics in cortical circuits. However, computational studies on E-I homeostasis have focused solely on the plasticity of inhibition, neglecting the impact of different modes of E-I homeostasis on cortical dynamics. Therefore, we investigate how the diverse mechanisms of E-I homeostasis employed by cortical networks shape oscillations and edge-of-bifurcation dynamics. Using the Wilson-Cowan model, we explore how distinct modes of E-I homeostasis maintain stable firing rates in models with varying levels of input and how it affects circuit dynamics. Our results confirm that E-I homeostasis can be leveraged to control edge-of-bifurcation dynamics and that some modes of homeostasis maintain mean firing rates under higher levels of input by modulating the distance to the bifurcation. Additionally, relying on multiple modes of homeostasis ensures stable activity while keeping oscillation frequencies within a physiological range. Our findings tie relevant features of cortical networks, such as E-I balance, the generation of gamma oscillations, and edge-of-bifurcation dynamics, under the framework of firing-rate homeostasis, providing a mechanistic explanation for the heterogeneity in the distance to the bifurcation found across cortical areas. In addition, we reveal the functional benefits of relying upon different homeostatic mechanisms, providing a robust method to regulate network dynamics with minimal perturbation to the generation of gamma rhythms and explaining the correlation between inhibition and gamma frequencies found in cortical networks.

Theta-band oscillations (3-8 Hz) in the mammalian hippocampus organize the temporal structure of cortical inputs, resulting in a phase code that enables rhythmic input sampling for episodic memory formation and spatial navigation. However, it remains unclear what evolutionary pressures might have driven the selection of theta over higher-frequency bands that could potentially provide increased input sampling resolution. Here, we address this question by introducing a theoretical framework that combines the efficient coding and neural oscillatory sampling hypotheses, focusing on the information rate (bits/s) of phase coding neurons. We demonstrate that physiologically realistic noise levels create a trade-off between the speed of input sampling, determined by oscillation frequency, and encoding precision in rodent hippocampal neurons. This speed-precision trade-off results in a maximum information rate of ∼1-2 bits/s within the theta frequency band, thus confining the optimal oscillation frequency to the low end of the spectrum. We also show that this framework accounts for key hippocampal features, such as the preservation of the theta band along the dorsoventral axis despite physiological gradients, and the modulation of theta frequency and amplitude by running speed. Extending the analysis beyond the hippocampus, we propose that theta oscillations could also support efficient stimulus encoding in the visual cortex and olfactory bulb. More broadly, our framework lays the foundation for studying how system features, such as noise, constrain the optimal sampling frequencies in both biological and artificial brains.

Stroke-related disruptions in functional connectivity (FC) often spread beyond lesioned areas and, given the localized nature of lesions, it is unclear how the recovery of FC is orchestrated on a global scale. Since recovery is accompanied by long-term changes in excitability, we propose excitatory-inhibitory (E-I) homeostasis as a driving mechanism. We present a large-scale model of the neocortex, with synaptic scaling of local inhibition, showing how E-I homeostasis can drive the post-lesion restoration of FC and linking it to changes in excitability. We show that functional networks could reorganize to recover disrupted modularity and small-worldness, but not network dynamics, suggesting the need to consider forms of plasticity beyond synaptic scaling of inhibition. On average, we observed widespread increases in excitability, with the emergence of complex lesion-dependent patterns related to biomarkers of relevant side effects of stroke, such as epilepsy, depression and chronic pain. In summary, our results show that the effects of E-I homeostasis extend beyond local E-I balance, driving the restoration of global properties of FC, and relating to post-stroke symptomatology. Therefore, we suggest the framework of E-I homeostasis as a relevant theoretical foundation for the study of stroke recovery and for understanding the emergence of meaningful features of FC from local dynamics.

Estimating the affective state of a user during a computer task traditionally relies on either subjective reports or analysis of physiological signals, facial expressions, and other measures. These methods have known limitations, can be intrusive and may require specialized equipment. An alternative would be employing a ubiquitous device of everyday use such as a standard keyboard. Here we investigate if we can infer the emotional state of a user by analyzing their typing patterns. To test this hypothesis, we asked 400 participants to caption a set of emotionally charged images taken from a standard database with known ratings of arousal and valence. We computed different keystroke pattern dynamics, including keystroke duration (dwell time) and latency (flight time). By computing the mean value of all of these features for each image, we found a statistically significant negative correlation between dwell times and valence, and between flight times and arousal. These results highlight the potential of using keystroke dynamics to estimate the affective state of a user in a non-obtrusive way and without the need for specialized devices.

Bacterial lipopolysaccharide (LPS) induces an acute inflammatory response across multiple organs, primarily via Toll-like receptor 4 (TLR4). We sought to define novel aspects of the complex spatiotemporal dynamics of LPS-induced inflammation using computational modeling, with a special focus on the timing of pathological systemic spillover. An analysis of principal drivers of LPS-induced inflammation in the heart, gut, lung, liver, spleen, and kidney to assess organ-specific dynamics, as well as in the plasma (as an assessment of systemic spillover), was carried out using data on 20 protein-level inflammatory mediators measured over 0-48h in both C57BL/6 and TLR4-null mice. Using a suite of computational techniques, including a time-interval variant of Principal Component Analysis, we confirm key roles for cytokines such as tumor necrosis factor-α and interleukin-17A, define a temporal hierarchy of organ-localized inflammation, and infer the point at which organ-localized inflammation spills over systemically. Thus, by employing a systems biology approach, we obtain a novel perspective on the time- and organ-specific components in the propagation of acute systemic inflammation.

How does our motor system solve the problem of anticipatory control in spite of a wide spectrum of response dynamics from different musculo-skeletal systems, transport delays as well as response latencies throughout the central nervous system? To a great extent, our highly-skilled motor responses are a result of a reactive feedback system, originating in the brain-stem and spinal cord, combined with a feed-forward anticipatory system, that is adaptively fine-tuned by sensory experience and originates in the cerebellum. Based on that interaction we design the counterfactual predictive control (CFPC) architecture, an anticipatory adaptive motor control scheme in which a feed-forward module, based on the cerebellum, steers an error feedback controller with counterfactual error signals. Those are signals that trigger reactions as actual errors would, but that do not code for any current of forthcoming errors. In order to determine the optimal learning strategy, we derive a novel learning rule for the feed-forward module that involves an eligibility trace and operates at the synaptic level. In particular, our eligibility trace provides a mechanism beyond co-incidence detection in that it convolves a history of prior synaptic inputs with error signals. In the context of cerebellar physiology, this solution implies that Purkinje cell synapses should generate eligibility traces using a forward model of the system being controlled. From an engineering perspective, CFPC provides a general-purpose anticipatory control architecture equipped with a learning rule that exploits the full dynamics of the closed-loop system.

The neocortex and thalamus provide a core substrate for perception, cognition, and action, and are interconnected through different direct and indirect pathways that maintain specific dynamics associated with functional states including wakefulness and sleep. It has been shown that a lack of excitation, or enhanced subcortical inhibition, can disrupt this system and drive thalamic nuclei into an attractor state of low-frequency bursting and further entrainment of thalamo-cortical circuits, also called thalamo-cortical dysrhythmia (TCD). The question remains however whether similar TCD-like phenomena can arise with a cortical origin. For instance, in stroke, a cortical lesion could disrupt thalamo-cortical interactions through an attenuation of the excitatory drive onto the thalamus, creating an imbalance between excitation and inhibition that can lead to a state of TCD. Here we tested this hypothesis by comparing the resting-state EEG recordings of acute ischaemic stroke patients (N = 21) with those of healthy, age-matched control-subjects (N = 17). We observed that these patients displayed the hallmarks of TCD: a characteristic downward shift of dominant α-peaks in the EEG power spectra, together with increased power over the lower frequencies (δ and θ-range). Contrary to general observations in TCD, the patients also displayed a broad reduction in β-band activity. In order to explain the genesis of this stroke-induced TCD, we developed a biologically constrained model of a general thalamo-cortical module, allowing us to identify the specific cellular and network mechanisms involved. Our model showed that a lesion in the cortical component leads to sustained cell membrane hyperpolarization in the corresponding thalamic relay neurons, that in turn leads to the de-inactivation of voltage-gated T-type Ca2+-channels, switching neurons from tonic spiking to a pathological bursting regime. This thalamic bursting synchronises activity on a population level through divergent intrathalamic circuits, and entrains thalamo-cortical pathways by means of propagating low-frequency oscillations beyond the restricted region of the lesion. Hence, pathological stroke-induced thalamo-cortical dynamics can be the source of diaschisis, and account for the dissociation between lesion location and non-specific symptoms of stroke such as neuropathic pain and hemispatial neglect.

In this video, we present the human robot interaction generated by applying the DAC cognitive architecture on the iCub robot. We demonstrate how the robot reacts and adapts to its environment within the context a continuous interactive scenario including different games. We emphasize as well that the artificial agent is maintaining a self-model in terms of emotions and drives and how those are expressed in order affect the social interaction.

The notion of attractor networks is the leading hypothesis for how associative memories are stored and recalled. A defining anatomical feature of such networks is excitatory recurrent connections. These "attract" the firing pattern of the network to a stored pattern, even when the external input is incomplete (pattern completion). The CA3 region of the hippocampus has been postulated to be such an attractor network; however, the experimental evidence has been ambiguous, leading to the suggestion that CA3 is not an attractor network. In order to resolve this controversy and to better understand how CA3 functions, we simulated CA3 and its input structures. In our simulation, we could reproduce critical experimental results and establish the criteria for identifying attractor properties. Notably, under conditions in which there is continuous input, the output should be "attracted" to a stored pattern. However, contrary to previous expectations, as a pattern is gradually "morphed" from one stored pattern to another, a sharp transition between output patterns is not expected. The observed firing patterns of CA3 meet these criteria and can be quantitatively accounted for by our model. Notably, as morphing proceeds, the activity pattern in the dentate gyrus changes; in contrast, the activity pattern in the downstream CA3 network is attracted to a stored pattern and thus undergoes little change. We furthermore show that other aspects of the observed firing patterns can be explained by learning that occurs during behavioral testing. The CA3 thus displays both the learning and recall signatures of an attractor network. These observations, taken together with existing anatomical and behavioral evidence, make the strong case that CA3 constructs associative memories based on attractor dynamics.

One of the key challenges of affective computing is to extend the expression of emotions to machines. Research in this field has focused mainly on embodied machines that can reproduce verbal or non-verbal cues such as facial movements and gestures. However, most machines we interact with in our daily life are non-anthropomorphic. For this reason, the question we are addressing in our study is whether it is possible to express emotions or affective states using non-anthropomorphic cues in non-humanoid artifacts. We generated animated motifs using a small set of parameters (color, motion and complexity) and we displayed them on the interactive floor of the experience Induction Machine (XIM), an immersive mixed reality space. We asked the participants to assess the emotions attributed to these abstract visual cues. Our findings suggest that it is not only possible to express affective states, but also to modulate human behavior through non-anthropomorphic and abstract stimuli.

The fusion of tactile and visual modalities is crucial for understanding objects and learning how to manipulate them. A common modus operandi in robotics is to deal with each of these modalities separately. We propose an integrated approach that associates to local visual features of an object, tactile feedback of the effector when touching that part of the object. Thus the agent learns to predict from a visual scene the shape/curvature properties of the object. The associated curvature properties are directly linked to grasp possibilities (as in approaches like [1] and [2]) but can also provide the agent with object categorization regarding the distribution of curvature classes.

How does one quantify dynamic complexity in large stochastic networks? While measures of integrated information serve as a good start to address these issues, all existing versions of the measure have been plagued with normalization ambiguities and combinatorial explosions which has hindered applications to large-scale networks. In this paper, we propose a new version of integrated information which resolves all these problems and brings us a step closer to addressing complexity in large biological networks. We also show that our measure is the only one which accounts for the total integrated information of a network. We apply this measure to prototypical networks and interestingly find the existence of complexity resonances in the solutions, which suggests a new way of looking at the informational spectrum of complex dynamical systems. Finally, as a proof of principle, we compute how much information is integrated by the anatomical connectivity network of the human cerebral cortex.

The cerebellum is a brain structure necessary for skilled motor behaviour and has a well understood and repetitive architecture. Such an architecture inspired the Marr-Albus-Ito theory of cerebellar learning, that provides an explanation for the acquisition of motor skills by the cerebellum. Numerous computational models inspired in such a theory have already been employed in robotic tasks. Here we look into one of the suggested roles of the cerebellum, the replacement of reflexes by anticipatory actions and we apply it to a robot navigation task. The acquisition of anticipatory actions has been thoroughly studied in the field of classical conditioning. Of particular interest is the so-called CS-intensity effect, an effect that links the rapidity of execution of an anticipatory protective action, the Conditioned Response (CR), to the intensity of a predictive signal, the Conditioning Stimulus (CS). We propose that the CS-intensity effect implements a built-in sensory-motor contingency that allows to carry over a skill learned in a safe and easy context, e.g., turning at slow velocity, to a more difficult one, e.g., a turning at a faster speed. We demonstrate this hypothesis in a series of experiments where a robot has to navigate a track that has a turn. We show that after being trained at a slow velocity, by means of the CS-intensity effect, the cerebellar controller modulates the turning such that its onset anticipates as the robot speed increases. Ultimately, through incremental learning, this generalization allows the robot to learn to navigate the track at its maximum speed.

Cooperation1is at the core of human social life. In this context, two major challenges face research on humanrobot interaction: the first is to understand the underlying structure of cooperation, and the second is to build, based on this understanding, artificial agents that can successfully and safely interact with humans. Here we take a psychologically grounded and human-centered approach that addresses these two challenges. We test the hypothesis that optimal cooperation between a naïve human and a robot requires that the robot can acquire and execute a joint plan, and that it communicates this joint plan through ecologically valid modalities including spoken language, gesture and gaze. We developed a cognitive system that comprises the human-like control of social actions, the ability to acquire and express shared plans and a spoken language stage. In order to test the psychological validity of our approach we tested 12 naïve subjects in a cooperative task with the robot. We experimentally manipulated the presence of a joint plan (vs. a solo plan), the use of task-oriented gaze and gestures, and the use of language accompanying the unfolding plan. The quality of cooperation was analyzed in terms of proper turn taking, collisions and cognitive errors. Results showed that while successful turn taking could take place in the absence of the explicit use of a joint plan, its presence yielded significantly greater success. One advantage of the solo plan was that the robot would always be ready to generate actions, and could thus adapt if the human intervened at the wrong time, whereas in the joint plan the robot expected the human to take his/her turn. Interestingly, when the robot represented the action as involving a joint plan, gaze provided a highly potent nonverbal cue that facilitated successful collaboration and reduced errors in the absence of verbal communication. These results support the cooperative stance in human social cognition, and suggest that cooperative robots should employ joint plans, fully communicate them in order to sustain effective collaboration while being ready to adapt if the human makes a midstream mistake.

Humans have the ability to use a complex code of non-verbal behavior to communicate their internal states to others. Conversely, the understanding of intentions and emotions of others is a fundamental aspect of human social interaction. In the study presented here we investigate how people perceive the expression of emotional states based on the observation of different styles of locomotion. Our goal is to find a small set of canonical parameters that allow to control a wide range of emotional expressions. We generated different classes of walking behavior by varying the head/torso inclination, the walking speed, and the viewing angle of an animation of a virtual character. 18 subjects rated the observed walking person using the two-dimensional circumplex model of arousal and valence. The results show that, independent of the viewing angle, participants perceived distinct states of arousal and valence. Moreover, we could show that parametrized body posture codes emotional states, irrespective of the contextual influence or facial expressions. These findings suggest that human locomotion transmits basic emotional cues that can be directly related to canonical parameters of different dimensions of the expressive behavior. These findings are important as they allow us to build virtual characters whose emotional expression is recognizable at large distance and during extended periods of time.

We introduce affordance gradients (AGs), continuous sensorimotor structures that allow to predict the consequences of the agent's actions on the state of the environment. AGs allow to generalize among never performed actions and compress all possible consequences of the action state space. AGs also provide a way of estimating the world state after several interactions of the agent with objects. We validate the notion of AGs using benchmarks designed for mobile robotics that we solve using E-puck robot simulations: learn the affordances of several objects, push an object along a predefined trajectory and place an object in at a target position and orientation. We are interested in the neurophysiological basis of affordances and how they can be inserted in a sensorimotor loop with memory structures like the one proposed by the DAC architecture. We show that AGs provide a generalization of the perception-action couplets stored in memory and learned by they adaptive layer of DAC.

By their very nature, virtual reality worlds are spatial. Hence, one of the key requirements for virtual reality applications is the possibility to navigate within the virtual world. Previous studies have shown that the characteristics of the device used for navigation, both in terms of the physical properties, and the interaction logic, has effects on the user's experience. The question we address is how does different navigation modes with the same physical interface affect the user's experience. We selected two modes which differed in the way the user's actions were mapped to movements in the virtual environment. To quantify the difference between the two interaction mappings, spatial memory and the subjective sense of presence were compared. The results of our study showed that interaction mapping affects both, spatial memory and presence. Hence, not only the specific physical device but also the way it is used is important for the user's experience and recollection of it. Additionally, we found a correlation between spatial memory and subjective sense of presence, which indicates that the subjective sense of presence can be estimated from the performance in a spatial memory task.

Navigation in unknown dynamic environments still remains a major challenge in robotics. Whereas insects like the desert ant with very limited computing and memory capacities solve this task with great efficiency. Thus, the understanding of the underlying neural mechanisms of insect navigation can inform us on how to build simpler yet robust autonomous robots. Based on recent developments in insect neuroethology and cognitive psychology, we propose a method for landmark navigation in dynamic environments. Our method enables the navigator to learn the reliability of landmarks using an expectation reinforcement method. For that end, we implemented a real-time neuronal model based on the Distributed Adaptive Control framework. The results demonstrate that our model is capable of learning the stability of landmarks by reinforcing its expectations. Also, the proposed mechanism allows the navigator to optimally restore its confidence when its expectations are violated. We also perform navigational experiments with real ants to compare with the results of our model. The behavior of the proposed autonomous navigator closely resembles real ant navigational behavior. Moreover, our model explains navigation in dynamic environments as a memory consolidation process, harnessing expectations and their violations.

Autonomous robotic odour source classification and localization in real world environments is an essential step for applications such as humanitarian demining, environmental monitoring or search and rescue operations. However, at the moment this problem has only been solved by nature (e.g.: moths, bees, rats, dogs). Biological systems are capable and efficient at odour source localization in spite of the difficulties present in the real world such as turbulent environments, obstacles, predators or interfering odours. Here we aim at exploiting our understanding of the moth to solve this problem and we propose a biologically based model of moth behaviour. We implement our model on a robot that uses chemical sensors and we test its performance in a controlled environment. Further, we extend the behavioural model with a sensor front end that supports classification in order to deal with odour distractors. We show that our system is able to locate an odour source and map the chemical environment in the presence of distractors.

According to Konorski's two phase theory of conditioning the associative processes underlying classical conditioning can be separated into a fast valence driven nonspecific learning systems (NLS) and a slow specific learning system (SLS). The theory states that the NLS elicits a non-specific state of arousal and that the SLS is responsible for the exact elicitation of a coordinated motor response. Based on biological evidence we propose the amygdala, the basal forebrain and the auditory cortex as an example of NLS and the cerebellum for the SLS. The performance of the model was tested applying the eye-blink paradigm of classical conditioning. The unconditioned stimulus induced amygdala stimulation of the nucleus basalis elicits plasticity in the NLS. This leads to an increased representation if the conditioned stimulus in the cortex. The plasticity of the cerebellar SLS is regulated by these increased cortical representation coding the behavioral importance of the conditioned stimulus. Here we provide a complete account of Konorskis proposal by integrating these two systems into a complete biologically-grounded computational model of the two-phase theory of classical conditioning.

Dealing with high-throughput information systems is becoming an everyday problem in many fields of science, as technological advances improve our ability to gather data. In particular, the information encoding problem in high-dimensional spaces is a crucial aspect to consider. In fact, biological systems are known to be very efficient at encoding and processing high-dimensional information. Here we propose a biologically-based solution that mimics the neural processing performed by the Antennal Lobe of insects. Based on our understanding of this system, our model exploits plausible neural mechanisms to transform the massive and high-dimensional spatial and temporal input of the olfactory receptor neurons into a neural population encoding based on synchrony and frequency, consistent with known physiology. We demonstrate the capabilities of our Antennal Lobe model in the context of a classification task of different olfactory stimuli of varying concentrations. We show that the generated neural representation conveys both the identity and the concentration of each stimuli.

Sequence learning tasks depend on the ability to acquire and control the order of actions and their proper timing. Several studies have shown that in sequence learning different areas of the brain are involved when recalling the order of actions and their proper interval. One hypothesis proposes that two separate areas of the brain interact with each other, one computes order while the other would compute the interval. A second hypothesis proposes that one area computes both, order and interval. To better understand how this computation of order and interval might be realized by the brain, we developed a robot based architecture and investigated the behavioral and architectural implications of these two hypothesis: one or two neuronal areas computing order and interval. Using a sequence learning foraging task we show that performance is enhanced in case of distributed processes. However, we show that as a drawback, explicit interval information can not be reconstructed.

Rodents are optimal real-world foragers that can smoothly regulate behaviors like homing and exploration combined with more elaborate abilities as food source localization. Here we investigate a robot based model that implements the self-regulatory processes that underly optimal foraging of rodents in unknown environments and is also able to combine it with goal directed behaviors. Behavior is decomposed into minimal homeostatic subsystems that regulate themselves through the local perception/detection of a gradient. On a higher level, the allostatic control orchestrates the interaction of the different homeostatic modules allowing it to dynamically manage the interactions between the desired values of each subsystem to achieve stability on a meta behavioral level. In this case, we show that overall behavioral stability can be achieved. We validate our model by comparing the behavior of both simulated and real robots with that of rodents. Our next step is then to justify gradients as a valid biological assumption by giving a biologically plausible process for generating them from a cognitive map, in this case, a set of approximated hippocampal place cells. We finally formulate path planning (used for goal reaching, e.g. food source localization) in the same context of a gradient map generation that can be then inserted as an additional subsystem of the higher meta level allostatic control.

In principle it appears advantageous for single neurons to perform non-linear operations. Indeed it has been reported that some neurons show signatures of such operations in their electrophysiological response. A particular case in point is the Lobula Giant Movement Detector (LGMD) neuron of the locust, which is reported to locally perform a functional multiplication. Given the wide ramifications of this suggestion with respect to our understanding of neuronal computations, it is essential that this interpretation of the LGMD as a local multiplication unit is thoroughly tested. Here we evaluate an alternative model that tests the hypothesis that the non-linear responses of the LGMD neuron emerge from the interactions of many neurons in the opto-motor processing structure of the locust. We show, by exposing our model to standard LGMD stimulation protocols, that the properties of the LGMD that were seen as a hallmark of local non-linear operations can be explained as emerging from the dynamics of the pre-synaptic network. Moreover, we demonstrate that these properties strongly depend on the details of the synaptic projections from the medulla to the LGMD. From these observations we deduce a number of testable predictions. To assess the real-time properties of our model we applied it to a high-speed robot. These robot results show that our model of the locust opto-motor system is able to reliably stabilize the movement trajectory of the robot and can robustly support collision avoidance. In addition, these behavioural experiments suggest that the emergent non-linear responses of the LGMD neuron enhance the system's collision detection acuity. We show how all reported properties of this neuron are consistently reproduced by this alternative model, and how they emerge from the overall opto-motor processing structure of the locust. Hence, our results propose an alternative view on neuronal computation that emphasizes the network properties as opposed to the local transformations that can be performed by single neurons.

We present a novel biomimetic approach to mapless autonomous navigation based on insect neuroethology. We implemented and tested a real-time neuronal model based on the Distributed Adaptive Control framework. The model unifies different aspects of insect navigation and foraging including landmark recognition, chemical search, path integration and optimal memory usage. Consistent with recent findings the model supports navigation using heading direction information, thus precluding the use of global information. We tested our model using a mobile robot performing a foraging task. While foraging for chemical sources in a wind tunnel, the robot memorizes the followed trajectories, using information from landmarks and heading direction accumulators. After foraging, landmark navigation is tested with the odor source turned off. Our results show stability against robot kidnapping and generalization of homing behavior to stable mapless landmark navigation. This demonstrates that allocentric and efficient goal-oriented navigation strategies can be generated by relying on purely local information.

This paper presents a new system that allows for intuitive control of an additive sound synthesis model from perceptually relevant high-level sonic features. We suggest a general framework for the extraction, abstraction, reproduction and transformation of timbral characteristics of a sound analyzed from recordings. We propose a method to train, tune and evaluate our system in an automatic, consistent and reproducible fashion, and show that this system yields various original audio and musical applications.

The grid cells of the rat medial entorhinal cortex (MEC) show an increased firing frequency when the position of the animal correlates with multiple regions of the environment that are arranged in regular triangular grids. Here, we describe an artificial neural network based on a twisted torus topology, which allows for the generation of regular triangular grids. The association of the activity of pre-defined hippocampal place cells with entorhinal grid cells allows for a highly robust-to-noise calibration mechanism, suggesting a role for the hippocampal back-projections to the entorhinal cortex.

Autonomous navigation in 2D and 3D environments has been studied for a long time. Navigating within a 3D environment is very challenging for both animals and robots and a variety of sensors are used to solve this task ranging from vision or a simple gyro or compass to GPS. The principal tasks for 3D autonomous navigation are course stabilization, altitude and drift control, and collision avoidance. Using this basis, some features can be easily added like aerial mapping, object recognition, homing strategies or takeoff and landing. Here we present a biologically based control layer for an Unmanned Aerial Vehicle (UAV) that provides course stabilization, altitude and drift control, and collision avoidance. The properties of this neuronal control system are evaluated using a flying robot.

We extend the study of human-robot interaction into the area of large-scale, multi-user, robotic interactive environments. Using our experimental infrastructure – the interactive space Ada, an exhibit at the Swiss national expo in 2002 that received 553,700 visitors – we show that human movement is predictive of key attitudes towards a space and other humans, and that subjects’ behavior and attitudes are influenced by subtle modifications of environmental parameters. We also found several demographic effects on visitors’ opinions of interactive spaces. These findings enhance our quantitative understanding of collective human behavior in interactive spaces and are a first step towards the construction of active environments that can automatically influence human motion and experience. This knowledge will be important in the design and construction of future interactive environments for enhancing the safety and enjoyment of shared areas for large numbers of people.

A key question in the design of intelligent environments is how a space can influence the actions of its users, and how such behavior can be learned. We present the results of experiments conducted as part of the Ada project, an interactive entertainment exhibit deployed at the Swiss national exhibition Expo.02. We used a learning model called distributed adaptive control (DAC) that is based on the animal learning paradigms of classical and operant conditioning. DAC has been developed using mobile robots in foraging tasks. Here, it was applied to the learning of effective cues for guiding visitors in a given direction. Our results show that, by using this learning mechanism, Ada was able to influence the behavior of visitors by learning to deploy particular types of cues. Many visitors could be induced to move toward a region of the space that they normally avoided visiting-an effect that can be seen as a spatial classification of visitors into interactive and noninteractive categories. In our analysis, we also introduce a measure of human activity that combines different types of data to capture key aspects of human behavior in interactive spaces.

In insects, we can find very complex and compact neural structures that are task specific. These neural structures allow them to perform complex tasks such as visual navigation, including obstacle avoidance, landing, self-stabilization, etc. Obstacle avoidance is fundamental for successful navigation, and it can be combined with more systems to make up more complex behaviors. In this paper, we present a model for collision avoidance based on the Lobula giant movement detector (LGMD) cell of the locust. This is a wide-field visual neuron that responds to looming stimuli and that can trigger avoidance reactions whenever a rapidly approaching object is detected. Here, we present result based on both an offline study of the model and its application to a flying robot.

We present a biophysically constrained cerebellar model of classical conditioning, implemented using a neuromorphic analog VLSI (aVLSI) chip. Like its biological counterpart, our cerebellar model is able to control adaptive behavior by predicting the precise timing of events. Here we describe the functionality of the chip and present its learning performance, as evaluated in simulated conditioning experiments at the circuit level and in behavioral experiments using a mobile robot. We show that this aVLSI model supports the acquisition and extinction of adaptively timed conditioned responses under real-world conditions with ultra-low power consumption.

Physiological experiments demonstrate the existence of weak pairwise correlations of neuronal activity in mammalian cortex (Singer, 1993). The functional implications of this correlated activity are hotly debated (Roskies et al., 1999). Nevertheless, it is generally considered a widespread feature of cortical dynamics. In recent years, another line of research has attracted great interest: the observation of a bimodal distribution of the membrane potential defining up states and down states at the single cell level (Wilson & Kawaguchi, 1996; Steriade, Contreras, & Amzica, 1994; Contreras & Steriade, 1995; Steriade, 2001). Here we use a theoretical approach to demonstrate that the latter phenomenon is a natural consequence of the former. In particular, we show that weak pairwise correlations of the inputs to a compartmental model of a layer V pyramidal cell can induce bimodality in its membrane potential. We show how this relationship can account for the observed increase of the power in the gamma-frequency band during up states, as well as the increase in the standard deviation and fraction of time spent in the depolarized state (Anderson, Lampl, Reichova, Carandini, & Ferster, 2000). In order to quantify the relationship between the correlation properties of a cortical network and the bistable dynamics of single neurons, we introduce a number of new indices. Subsequently, we demonstrate that a quantitative agreement with the experimental data can be achieved, introducing voltage-dependent mechanisms in our neuronal model such as Ca(2+)- and Ca(2+)-dependent K(+) channels. In addition, we show that the up states and down states of the membrane potential are dependent on the dendritic morphology of cortical neurons. Furthermore, bringing together network and single cell dynamics under a unified view allows the direct transfer of results obtained in one context to the other and suggests a new experimental paradigm: the use of specific intracellular analysis as a powerful tool to reveal the properties of the correlation structure present in the network dynamics.

Encoding of sensory events in internal states of the brain requires that this information can be decoded by other neural structures. The encoding of sensory events can involve both the spatial organization of neuronal activity and its temporal dynamics. Here we investigate the issue of decoding in the context of a recently proposed encoding scheme: the temporal population code. In this code, the geometric properties of visual stimuli become encoded into the temporal response characteristics of the summed activities of a population of cortical neurons. For its decoding, we evaluate a model based on the structure and dynamics of cortical microcircuits that is proposed for computations on continuous temporal streams: the liquid state machine. Employing the original proposal of the decoding network results in a moderate performance. Our analysis shows that the temporal mixing of subsequent stimuli results in a joint representation that compromises their classification. To overcome this problem, we investigate a number of initialization strategies. Whereas we observe that a deterministically initialized network results in the best performance, we find that in case the network is never reset, that is, it continuously processes the sequence of stimuli, the classification performance is greatly hampered by the mixing of information from past and present stimuli. We conclude that this problem of the mixing of temporally segregated information is not specific to this particular decoding model but relates to a general problem that any circuit that processes continuous streams of temporal information needs to solve. Furthermore, as both the encoding and decoding components of our network have been independently proposed as models of the cerebral cortex, our results suggest that the brain could solve the problem of temporal mixing by applying reset signals at stimulus onset, leading to a temporal segmentation of a continuous input stream.

Ada is an entertainment exhibit that is able to interact with many people simultaneously, using a language of light and sound. "She " received 553,700 visitors over 5 months during the Swiss Expo.02 in 2002. In this paper we present the broad motivations, design and technologies behind Ada, and a first overview of the outcomes of the exhibit.

One current explanation of the view independent representation of space by the place-cells of the hippocampus is that they arise out of the summation of view dependent Gaussians. This proposal as- sumes that visual representations show bounded invariance. Here we investigate whether a recently proposed visual encoding scheme called the temporal population code can provide such representa- tions. Our analysis is based on the behavior of a simulated robot in a virtual environment containing speci(cid:12)c visual cues. Our re- sults show that the temporal population code provides a represen- tational substrate that can naturally account for the formation of place (cid:12)elds.

Despite immense progress in neuroscience, we remain restricted in our ability to construct autonomous behaving robots that match the competence of even simple animals. The barriers to the realisation of this goal include: the lack of knowledge of system integration issues, engineering limitations and organisational constraints common to many research laboratories. In this paper we describe our approach to addressing these issues by constructing an artificial organism within the framework of the Ada project - a large-scale public exhibit for the Swiss Expo.02 national exhibition.

We present a real-time model of learning in the auditory cortex that is trained using real-world stimuli. The system consists of a peripheral and a central cortical network of spiking neurons. The synapses formed by peripheral neurons on the central ones are subject to synaptic plasticity. We implemented a biophysically realistic learning rule that depends on the precise temporal relation of pre- and postsynaptic action potentials. We demonstrate that this biologically realistic real-time neuronal system forms stable receptive fields that accurately reflect the spectral content of the input signals and that the size of these representations can be biased by global signals acting on the local learning mechanism. In addition, we show that this learning mechanism shows fast acquisition and is robust in the presence of large imbalances in the probability of occurrence of individual stimuli and noise.

Mechanisms influencing learning in neural networks are usually investigated on either a local or a global scale. The former relates to synaptic processes, the latter to unspecific modulatory systems. Here we study the interaction of a local learning rule that evaluates coincidences of pre- and postsynaptic action potentials and a global modulatory mechanism, such as the action of the basal forebrain onto cortical neurons. The simulations demonstrate that the interaction of these mechanisms leads to a learning rule supporting fast learning rates, stability, and flexibility. Furthermore, the simulations generate two experimentally testable predictions on the dependence of backpropagating action potential on basal forebrain activity and the relative timing of the activity of inhibitory and excitatory neurons in the neocortex.

The visual systems of insects perform complex processing using remarkably compact neural circuits, yet these circuits are often studied using simplified stimuli which fail to reveal their behaviour in more complex visual environments. We address this issue by testing models of these circuits in real-world visual environments using a mobile robot. In this paper we focus on the lobula giant movement detector (LGMD) system of the locust which responds selectively to objects which approach the animal on a collision course and is thought to trigger escape behaviours. We show that a neural network model of the LGMD system shares the preference for approaching objects and detects obstacles over a range of speeds. Our results highlight aspects of the basic response properties of the biological system which have important implications for the behavioural role of the LGMD.

Neuroscience is progressing vigorously, and knowledge at different levels of description is rapidly accumulating. To establish relationships between results found at these different levels is one of the central challenges. In this simulation study, we demonstrate how microscopic cellular properties, taking the example of the action of modulatory substances onto the membrane leakage current, can provide the basis for the perceptual functions reflected in the macroscopic behavior of a cortical network. In the first part, the action of the modulatory system on cortical dynamics is investigated. First, it is demonstrated that the inclusion of these biophysical properties in a model of the primary visual cortex leads to the dynamic formation of synchronously active neuronal assemblies reflecting a context-dependent binding and segmentation of image components. Second, it is shown that the differential regulation of the leakage current can be used to bias the interactions of multiple cortical modules. This allows the flexible use of different feature domains for scene segmentation. Third, we demonstrate how, within the proposed architecture, the mapping of a moving stimulus onto the spatial dimension of the network results in an increased speed of synchronization. In the second part, we demonstrate how the differential regulation of neuromodulatory activity can be achieved in a self-consistent system. Three different mechanisms are described and investigated. This study thus demonstrates how a modulatory system, affecting the biophysical properties of single cells, can be used to achieve context-dependent processing at the system level.