Daniele Caligiore

Theories and computational models of affordance and mirror systems: An integrative review

Neuroscientific and psychological data suggest a close link between affordance and mirror systems in the brain. However, we still lack a full understanding of both the individual systems and their interactions. Here, we propose that the architecture and functioning of the two systems is best understood in terms of two challenges faced by complex organisms, namely: (a) the need to select among multiple affordances and possible actions dependent on context and high-level goals and (b) the exploitation of the advantages deriving from a hierarchical organisation of behaviour based on actions and action-goals. We first review and analyse the psychological and neuroscientific literature on the mechanisms and processes organisms use to deal with these challenges. We then analyse existing computational models thereof. Finally we present the design of a computational framework that integrates the reviewed knowledge. The framework can be used both as a theoretical guidance to interpret empirical data and design new experiments, and to design computational models addressing specific problems debated in the literature.

TRoPICALS: A Computational Embodied Neuroscience Model of Compatibility Effects

Perceiving objects activates the representation of their affordances. For example, experiments on compatibility effects showed that categorizing objects by producing certain handgrips (power or precision) is faster if the requested responses are compatible with the affordance elicited by the size of objects (e.g., small or large). The article presents a neural-network architecture that provides a general framework to account for compatibility effects. The model was designed with a methodological approach (computational embodied neuroscience) that aims to provide increasingly general accounts of brain and behavior (4 sources of constraints are used: neuroscientific data, behavioral data, embodied systems, reproduction of learning processes). The model is based on 4 principles of brain organization that we claim underlie most compatibility effects. First, visual perception and action are organized in the brain along a dorsal neural pathway encoding affordances and a ventral pathway encoding goals. Second, the prefrontal cortex within the ventral pathway gives a top-down bias to action selection by integrating information on stimuli, context, and goals. Third, reaction times depend on dynamic neural competitions for action selection that integrate bottom-up and top-down information. The congruence or incongruence between affordances and goals explains the different reaction times found in the experiments. Fourth, as words trigger internal simulations of their referents, they can cause compatibility effects as objects do. We validated the model by reproducing and explaining 3 types of compatibility effects and showed its heuristic power by producing 2 testable predictions. We also assessed the explicative power of the model by comparing it with related models and showed how it can be extended to account for other compatibility effects.

Consensus Paper: Towards a Systems-Level View of Cerebellar Function: the Interplay Between Cerebellum, Basal Ganglia, and Cortex

Despite increasing evidence suggesting the cerebellum works in concert with the cortex and basal ganglia, the nature of the reciprocal interactions between these three brain regions remains unclear. This consensus paper gathers diverse recent views on a variety of important roles played by the cerebellum within the cerebello-basal ganglia-thalamo-cortical system across a range of motor and cognitive functions. The paper includes theoretical and empirical contributions, which cover the following topics: recent evidence supporting the dynamical interplay between cerebellum, basal ganglia, and cortical areas in humans and other animals; theoretical neuroscience perspectives and empirical evidence on the reciprocal influences between cerebellum, basal ganglia, and cortex in learning and control processes; and data suggesting possible roles of the cerebellum in basal ganglia movement disorders. Although starting from different backgrounds and dealing with different topics, all the contributors agree that viewing the cerebellum, basal ganglia, and cortex as an integrated system enables us to understand the function of these areas in radically different ways. In addition, there is unanimous consensus between the authors that future experimental and computational work is needed to understand the function of cerebellar-basal ganglia circuitry in both motor and non-motor functions. The paper reports the most advanced perspectives on the role of the cerebellum within the cerebello-basal ganglia-thalamo-cortical system and illustrates other elements of consensus as well as disagreements and open questions in the field.

The contribution of brain sub-cortical loops in the expression and acquisition of action understanding abilities ☆

Highlights • Focusing on cortical areas is too restrictive to explain action understanding ability.• We propose that sub-cortical areas support action understanding ability.• Cortical and sub-cortical processes allow acquisition of action understanding ability.

The embodied mind extended: using words as social tools

The extended mind view and the embodied-grounded view of cognition and language are typically considered as rather independent perspectives. In this paper we propose a possible integration of the two views and support it proposing the idea of “Words As social Tools” (WAT). In this respect, we will propose that words, also due to their social and public character, can be conceived as quasi-external devices that extend our cognition. Moreover, words function like tools in that they enlarge the bodily space of action thus modifying our sense of body. To support our proposal, we review the relevant literature on tool-use and on words as tools and report recent evidence indicating that word use leads to an extension of space close to the body. In addition, we outline a model of the neural processes that may underpin bodily space extension via word use and may reflect possible effects on cognition of the use of words as external means. We also discuss how reconciling the two perspectives can help to overcome the limitations they encounter if considered independently.

How affordances associated with a distractor object affect compatibility effects: A study with the computational model TRoPICALS

Seeing an object activates both visual and action codes in the brain. Crucial evidence supporting this view is the observation of object to response compatibility effects: perception of an object can facilitate or interfere with the execution of an action (e.g., grasping) even when the viewer has no intention of interacting with the object. TRoPICALS is a computational model that proposes some general principles about the brain mechanisms underlying compatibility effects, in particular the idea that top-down bias from prefrontal cortex, and whether it conflicts or not with the actions afforded by an object, plays a key role in such phenomena. Experiments on compatibility effects using a target and a distractor object show the usual positive compatibility effect of the target, but also an interesting negative compatibility effect of the distractor: responding with a grip compatible with the distractor size produces slower reaction times than the incompatible case. Here, we present an enhanced version of TRoPICALS that reproduces and explains these new results. This explanation is based on the idea that the prefrontal cortex plays a double role in its top-down guidance of action selection producing: (a) a positive bias in favour of the action requested by the experimental task; (b) a negative bias directed to inhibiting the action evoked by the distractor. The model also provides testable predictions on the possible consequences of damage to volitional circuits such as in Parkinsonian patients.

Action observation and motor imagery for rehabilitation in Parkinson's disease: A systematic review and an integrative hypothesis

HIGHLIGHTSAction observation therapy can be used for rehabilitation of Parkinsons disease.Motor imagery practice can be used for rehabilitation of Parkinsons disease.Rehabilitation for Parkinsons disease might combine action observation and motor imagery.Action observation and motor imagery involve both cortical and sub‐cortical processes. ABSTRACT This article discusses recent evidence supporting the use of action observation therapy and motor imagery practice for rehabilitation of Parkinsons disease. A main question that emerges from the review regards the different effectiveness of these approaches and the possibility of integrating them into a single method to enhance motor behaviour in subjects with Parkinsons disease. In particular, the reviewed studies suggest that action observation therapy can have a positive effect on motor facilitation of patients and that a long‐term rehabilitation program based on action observation therapy or motor imagery practice can bring some benefit on their motor recovery. Moreover, the paper discusses how the research on the combined use of action observation and motor imagery for motor improvements in healthy subjects may encourage the combined use of action observation therapy and motor imagery practice for therapeutic aims in Parkinsons disease. To date, this hypothesis has never been experimented.

Parkinson's disease as a system-level disorder

Traditionally, the basal ganglia have been considered the main brain region implicated in Parkinson’s disease. This single area perspective gives a restricted clinical picture and limits therapeutic approaches because it ignores the influence of altered interactions between the basal ganglia and other cerebral components on Parkinsonian symptoms. In particular, the basal ganglia work closely in concert with cortex and cerebellum to support motor and cognitive functions. This article proposes a theoretical framework for understanding Parkinson’s disease as caused by the dysfunction of the entire basal ganglia–cortex–cerebellum system rather than by the basal ganglia in isolation. In particular, building on recent evidence, we propose that the three key symptoms of tremor, freezing, and impairments in action sequencing may be explained by considering partially overlapping neural circuits including basal ganglia, cortical and cerebellar areas. Studying the involvement of this system in Parkinson’s disease is a crucial step for devising innovative therapeutic approaches targeting it rather than only the basal ganglia. Possible future therapies based on this different view of the disease are discussed.

Integrating reinforcement learning, equilibrium points, and minimum variance to understand the development of reaching: a computational model.

Despite the huge literature on reaching behavior, a clear idea about the motor control processes underlying its development in infants is still lacking. This article contributes to overcoming this gap by proposing a computational model based on three key hypotheses: (a) trial-and-error learning processes drive the progressive development of reaching; (b) the control of the movements based on equilibrium points allows the model to quickly find the initial approximate solution to the problem of gaining contact with the target objects; (c) the request of precision of the end movement in the presence of muscular noise drives the progressive refinement of the reaching behavior. The tests of the model, based on a two degrees of freedom simulated dynamical arm, show that it is capable of reproducing a large number of empirical findings, most deriving from longitudinal studies with children: the developmental trajectory of several dynamical and kinematic variables of reaching movements, the time evolution of submovements composing reaching, the progressive development of a bell-shaped speed profile, and the evolution of the management of redundant degrees of freedom. The model also produces testable predictions on several of these phenomena. Most of these empirical data have never been investigated by previous computational models and, more important, have never been accounted for by a unique model. In this respect, the analysis of the model functioning reveals that all these results are ultimately explained, sometimes in unexpected ways, by the same developmental trajectory emerging from the interplay of the three mentioned hypotheses: The model first quickly learns to perform coarse movements that assure a contact of the hand with the target (an achievement with great adaptive value) and then slowly refines the detailed control of the dynamical aspects of movement to increase accuracy.

Vision, action and language unified through embodiment

Increasing evidence shows that vision, action and language should not be regarded as a set of disembodied processes. Instead, they form a closely integrated and highly dynamic system that is attuned to the constraints of its bodily implementation as well as to the constraints coming from the world with which this body interacts. One consequence of such embodiment of cognition is that seeing an object, even when there is no intention to handle it, activates plans for actions directed toward it (e.g., Tucker & Ellis, 1998, 2001; Fischer & Dahl, 2007). Using object names induces similar action planning effects as seeing the objects themselves (Tucker & Ellis, 2004; Borghi, Glenberg & Kaschak, 2004). Depending on linguistic context, different object features can be activated for action planning, as indicated by facilitated manual responses or ‘‘affordance effects’’ (e.g., Borghi, 2004; Glenberg & Robertson, 2000; Zwaan, 2004). Similarly, different action intentions direct attention differently to object features for processing (e.g., Bekkering & Neggers, 2002; Fischer & Hoellen, 2004; Symes, Tucker, Ellis, Vainio, & Ottoboni, 2008). Eye movements during visually guided actions shed further light on the close relationship between vision, action and language (Land & Furneaux, 1997; Johansson, Westling, Backstrom, & Flanagan, 2001). For example when humans interact with objects, their eyes move ahead of their hands to support the on-line control of grasping (e.g., Bekkering & Neggers, 2002). These behavioral results are supported by brain imaging studies of object affordances in humans (e.g., Grezes, Tucker, Armony, Ellis, & Passingham, 2003) and single cell recordings in monkeys (e.g., Sakata, Taira, Mine, & Murata, 1992; Fadiga, Fogassi, Gallese, & Rizzolatti, 2000). Together, these behavioral and neuroscientific studies have recently begun to inform computational models of embodied cognition. For example, Tsiotas, Borghi and Parisi (2005) devised an artificial life simulation to give an evolutionary account of some affordance effects, and Caligiore, Borghi, Parisi, and Baldassarre (2010) proposed a computational model to account for several affordance-related effects in grasping, reaching, and language. The neuroscientific constraints implemented in the design of the model allow its authors to investigate the neural mechanisms underlying affordance selection and control. The present special issue brings together recent developments at the intersection between behavioral, neuroscientific, and computational approaches to embodied cognition. Strong support for the close link between vision, action and language comes from studies which highlight how language processing and comprehension make use of neural systems ordinarily used for perception and action (Lakoff, 1987; Zwaan, 2004; Barsalou, 1999; Glenberg & Robertson, 1999; Gallese, 2008; Glenberg, 2010). For example, when humans process the word ‘‘cup’’ they seem to reenact (and therefore internally simulate) many of the perceptual, motor and affective representations related to a cup (Barsalou, 1999). In a similar way sentences and abstract words are understood by creating a simulation of the actions underlying them (Glenberg and Kaschak, 2002; D. Caligiore (&) Laboratory of Computational Embodied Neuroscience, Istituto di Scienze e Tecnologie della Cognizione, Consiglio Nazionale delle Ricerche (LOCEN-ISTC-CNR), Roma, Italy e-mail: daniele.caligiore@istc.cnr.it