Associative learning in peripersonal space: fear responses are acquired in hand-centered coordinates

Space coding affects perception of stimuli associated to negative valence: threatening stimuli presented within the peripersonal space (PPS) speed up behavioral responses compared to non-threatening events. However, it remains unclear whether the association between stimuli and their negative valence is acquired in a body-part centered reference system, a main feature of the PPS coding. Here we test the hypothesis that associative learning takes place in hand-centered coordinates and can therefore remap according to hand displacement. In two experiments, we used a Pavlovian fear-learning paradigm to associate a visual stimulus (light circle, the conditioned stimulus, CS) with an aversive stimulus (electrocutaneous shock) applied on the right hand only when the CS was displayed close (CS+), but not far from it (CS-). Measuring the skin conductance response (SCR), we observed successful fear conditioning, with increased anticipatory fear responses associated with CSs+. Crucially, Experiment I showed a remapping of these responses following hand displacement, with a generalization to both types of CS. Experiment II corroborated and further extended our findings by ruling out the novelty of the experimental context as driving factor of such modulations. Indeed, fear responses were present only for stimuli within the PPS, but not for new stimuli displayed outside the PPS. By revealing a hand-centred (re)mapping of the conditioning effect, these findings indicate that associative learning can arise in hand-centred coordinates. They further suggest that the threatening valence of an object also depends on its basic spatial relationship with our body.

Functional networks for peripersonal space coding and prediction of impact to the body

Peripersonal space is defined as the space surrounding the body, which we can interact with and act upon. It has been hypothesized to play a key functional role in body representation and in the definition of a safety boundary around the body. More recently, growing evidence suggests that this space is dynamically resized both as a function of internal states such as anxiety or as a function of external contingencies such as social interactions or goal-directed actions. In the following review, we will review seminal and recent work in both human and non-human primates, describing the functional cortical networks involved in the coding of body margin (the skin), peripersonal space (around the body) and far space (away from the body), and we will describe how these networks are recruited during the prediction of an impact to the body (near the skin). We will propose a functional perspective to recent evidence for multiple behaviourally dissociable peripersonal spaces, and discuss the putative neuronal and network mechanisms that could account for the observed dynamic resizing of peripersonal space.

Multiple Visual Feature Integration Based Automatic Aesthetics Evaluation of Robotic Dance Motions

Imitation of human behaviors is one of the effective ways to develop artificial intelligence. Human dancers, standing in front of a mirror, always achieve autonomous aesthetics evaluation on their own dance motions, which are observed from the mirror. Meanwhile, in the visual aesthetics cognition of human brains, space and shape are two important visual elements perceived from motions. Inspired by the above facts, this paper proposes a novel mechanism of automatic aesthetics evaluation of robotic dance motions based on multiple visual feature integration. In the mechanism, a video of robotic dance motion is firstly converted into several kinds of motion history images, and then a spatial feature (ripple space coding) and shape features (Zernike moment and curvature-based Fourier descriptors) are extracted from the optimized motion history images. Based on feature integration, a homogeneous ensemble classifier, which uses three different random forests, is deployed to build a machine aesthetics model, aiming to make the machine possess human aesthetic ability. The feasibility of the proposed mechanism has been verified by simulation experiments, and the experimental results show that our ensemble classifier can achieve a high correct ratio of aesthetics evaluation of 75%. The performance of our mechanism is superior to those of the existing approaches.

Dynamic representation of 3D auditory space in the midbrain of the free-flying echolocating bat

Essential to spatial orientation in the natural environment is a dynamic representation of direction and distance to objects. Despite the importance of 3D spatial localization to parse objects in the environment and to guide movement, most neurophysiological investigations of sensory mapping have been limited to studies of restrained subjects, tested with 2D, artificial stimuli. Here, we show for the first time that sensory neurons in the midbrain superior colliculus (SC) of the free-flying echolocating bat encode 3D egocentric space, and that the bat’s inspection of objects in the physical environment sharpens tuning of single neurons, and shifts peak responses to represent closer distances. These findings emerged from wireless neural recordings in free-flying bats, in combination with an echo model that computes the animal’s instantaneous stimulus space. Our research reveals dynamic 3D space coding in a freely moving mammal engaged in a real-world navigation task.

Dynamical modulation of theta-gamma coupling during REM sleep

Theta phase modulates gamma amplitude during spatial navigation and rapid eye movement sleep (REMs). Although the REMs theta rhythm has been linked to spatial memory consolidation, the underlying mechanism remains unclear. We investigate dynamics of theta-gamma interactions across multiple frequency and temporal scales in simultaneous recordings from hippocampal CA3, CA1, subiculum, and parietal cortex. We show that theta phase significantly modulates three distinct gamma bands during REMs, dynamically. Interestingly, we further show that theta-gamma coupling swings between different hippocampal and cortical structures during REMs and tends to increase over a single REMs episode. Comparing to active wake, theta-gamma coupling during REMs is significantly increased for subicular and cortical, but not for CA3 and CA1, recordings. Finally, optogenetic silencing of septohippocampal GABAergic projections significantly impedes both theta-gamma coupling and theta phase coherence, two neural mechanisms of working and long-term memory, respectively. Thus, we show that theta-gamma coupling and theta phase coherence are highly modulated during single REMs episode and propose that theta-gamma coupling provides a predominant mechanism for information processing within each brain region, while the orchestrated nature of coupling activity establishes a specific phase-space coding of information during sleep.