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Embodied and grounded cognition theories state that cognitive processing is built upon sensorimotor systems. In the context of numerical cognition, support to this framework comes from the interactions between numerical processing and the hand actions of reaching and grasping documented in skilled adults. Accordingly, mechanisms for the processing of object size and location during reach and grasp actions might scaffold the development of mental representations of numerical magnitude. The present study exploited motor adaptation to test the hypothesis of a functional overlap between neurocognitive mechanisms of hand action and numerical processing. Participants performed repetitive grasping of an object, repetitive pointing, repetitive tapping, or passive viewing. Subsequently, they performed a symbolic number comparison task. Importantly, hand action and number comparison were functionally and temporally dissociated, thereby minimizing context-based effects. Results showed that executing the action of pointing slowed down the responses in number comparison. Moreover, the typical distance effect (faster responses for numbers far from the reference as compared to close ones) was not observed for small numbers after pointing, while it was enhanced by grasping. These findings confirm the functional link between hand action and numerical processing, and suggest new hypotheses on the role of pointing as a meaningful gesture in the development and embodiment of numerical skills.

•We explore the neural correlates of grasping and number comparison with fNIRS.•We describe common active clusters during both number comparison and grasping.•Activity in the left parietal cluster correlates with accuracy in calculation.•Mathematical proficiency might be linked to functional specificity.•The use of fNIRS is promising for the study of embodied number processing. Interactions between number processing and hand grasping have been extensively studied; however, the specific neural mechanisms underlying these interactions remain elusive. In this study, healthy adults (N = 30) performed number magnitude comparison and hand grasping, both paired with stringent control conditions (color naming and squeezing, respectively). Hemodynamic activity in the cortical networks associated with number processing and hand action was recorded using functional near-infrared spectroscopy (fNIRS). Significant hemodynamic activity was observed during both number comparison and hand grasping within the left superior posterior parietal lobule and precuneus, as well as along the border between the right precentral and postcentral gyri. These areas were not active during the control conditions. Importantly, hemodynamic activity in a sub-area of the left parietal cluster correlated with the participants’ proficiency in calculation, suggesting that a larger degree of functional specificity within this region may be associated with better math skills. Calculation performance was also linked to activity in a small region within the right inferior frontal gyrus. Overall, the right parietal activity revealed differential activation in number comparison and grasping. These findings confirm both shared and task-specific neural areas involved in numerical and motor processing, and ultimately highlight the role of individual differences in shaping the tight link between numerical cognition and the sensorimotor system.

•Leftward PA improved reaching with contralesional hand in ipsilesional space.•Post-treatment reorganization showed LH asymmetry in parietal and motor areas.•LH network segregation and intra-hemispheric dispersion increased post-treatment.•Inter-hemispheric connectivity decreased, suggesting rehab-related improvements.•Dynamic entropy linked to direct, static changes tied to indirect disconnections. Prismatic adaptation (PA) is a visuomotor procedure using prismatic lenses to induce a temporary shift of visuomotor coordinates. It relies on a brain network which includes the anterior and posterior cerebellum and parietal regions, such as the intraparietal sulcus and the posterior parietal cortex. Lesions in these parietal areas are often associated with the presence of Optic Ataxia (OA), a disorder of visually guided reaching movements. Studies report contrasting results concerning the effects of PA in OA patients, whereby some fail in adapting to prisms and others show preserved adaptation. Here, we describe behavioural and neurofunctional changes in a left hemisphere stroke patient with OA who completed ten sessions of leftward PA as part of her cognitive rehabilitation. After the treatment, reaching improved with the contralesional hand in the ipsilesional hemifield. Moreover, resting-state fMRI measures of network dispersion applied to low-dimensional functional gradients revealed marked hemispheric asymmetry, with greater reorganization in the left hemisphere involving an increase in network segregation in left attentional and somatosensory networks, alongside higher intra-hemispheric network dispersion. Conversely, inter-hemispheric dispersion decreased, particularly between attentive and somatosensory-motor networks. Dynamic edge-centric analysis showed reduced entropy in the visual network and increased entropy in the dorsal attention and control networks. These entropy shifts, reflective of nodal diversity in functional co-fluctuations, correlated with direct structural disconnections. Conversely, static gradient-based reorganization was significantly associated with indirect structural disconnection profiles. To our knowledge, this is the first study exploring changes at the behavioural and neurofunctional level in an OA patient following repetitive sessions of PA, highlighting complementary contributions of static and dynamic functional neuroimaging features in capturing possible mechanisms of functional reorganization. [Display omitted]

This study investigates the bi-directionality of synaestesic experience by means of a flanked bisection paradigm in TT, a number-colour synaesthete. Previous studies have shown that bisection is shifted towards the larger digit flanker (e.g., Ranzini & Girelli, 2012 ). TT and controls performed line bisections with lines flanked by black digits (experiment 1), by TT’s photism colours (experiment 2), and by congruently (experiment 3), or incongruently coloured digits (experiment 4). While the results of the control group mainly replicated previous findings, only the colour-digit congruence elicited in TT the larger-digit bias. TT’s absence of effects in the other conditions was not due to reduced sensitivity to luminance effects (experiment 5), or to mathematical expertise (experiment 6). We suggest that grapheme-colour synaesthesia might be characterised by a rigid access to semantic representation when the inducer is task-irrelevant.

Growing evidence suggests that orienting visual attention in space can influence the processing of numerical magnitude, with leftward orienting speeding up the processing of small numbers relative to larger ones and the converse for rightward orienting. The manipulation of eye movements is a convenient way to direct visuospatial attention, but several aspects of the complex relationship between eye movements, attention orienting and number processing remain unexplored. In a previous study, we observed that inducing involuntary, reflexive eye movements by means of optokinetic stimulation affected number processing only when numerical magnitude was task relevant (i.e., during magnitude comparison, but not during parity judgment; Ranzini et al., in J Cogn Psychol 27, 459–470, (2015). Here, we investigated whether processing of task-irrelevant numerical magnitude can be modulated by voluntary eye movements, and whether the type of eye movements (smooth pursuit vs. saccades) would influence this interaction. Participants tracked with their gaze a dot while listening to a digit. The numerical task was to indicate whether the digit was odd or even through non-spatial, verbal responses. The dot could move leftward or rightward either continuously, allowing tracking by smooth pursuit eye movements, or in discrete steps across a series of adjacent locations, triggering a sequence of saccades. Both smooth pursuit and saccadic eye movements similarly affected number processing and modulated response times for large numbers as a function of direction of motion. These findings suggest that voluntary eye movements redirect attention in mental number space and highlight that eye movements should play a key factor in the investigation of number–space interactions.

Recent studies have suggested that numerical and physical magnitudes are similarly processed by a generalized magnitude system. The present study investigates the number–luminance interaction, taking advantage of illusory effects in a cued line bisection task with numerical or nonnumerical flankers and varying levels of luminance. The results showed that both dimensions influenced bisection performance. Whereas numbers ( Experiment 1 ) induced a systematic shift of the subjective midpoint toward the larger digit, luminance ( Experiment 2 ) modulated the bisection performance toward the darker flanker. By combining these two illusions ( Experiments 3 and 4 ), the two dimensions interfered with each other. This pattern of results suggests overlapping representations for physical and numerical magnitudes and highlights the value of illusory effects in cognitive research.

Embodied and grounded cognition theories state that cognitive processing is built upon sensorimotor systems. In the context of numerical cognition, support to this framework comes from the interactions between numerical processing and the hand actions of reaching and grasping documented in skilled adults. Accordingly, mechanisms for the processing of object size and location during reach and grasp actions might scaffold the development of mental representations of numerical magnitude. The present study exploited motor adaptation to test the hypothesis of a functional overlap between neurocognitive mechanisms of hand action and numerical processing. Participants performed repetitive grasping of an object, repetitive pointing, repetitive tapping, or passive viewing. Subsequently, they performed a symbolic number comparison task. Importantly, hand action and number comparison were functionally and temporally dissociated, thereby minimizing context-based effects. Results showed that executing the action of pointing slowed down the responses in number comparison. Moreover, the typical distance effect (faster responses for numbers far from the reference as compared to close ones) was not observed for small numbers after pointing, while it was enhanced by grasping. These findings confirm the functional link between hand action and numerical processing, and suggest new hypotheses on the role of pointing as a meaningful gesture in the development and embodiment of numerical skills.

A variety of studies showed that participants are facilitated when responding to graspable objects, while it has not been fully investigated what happens during interactions with graspable objects that are potentially dangerous. The present study focuses on the mechanisms underlying the processing of dangerous objects. In two experiments, we adopted a paradigm that has never been employed in this context, a bisection task. The line was flanked by objects belonging to different categories. We explored the sensitivity to the distinction between neutral and dangerous objects, by measuring whether the performance was biased toward a specific object category. In Experiment 1 both teenagers and adults bisected lines flanked by dangerous and neutral graspable objects, and they misperceived the line midpoint toward the neutral graspable object or, stated differently, on the opposite side of the dangerous graspable object. In Experiment 2 adults bisected lines flanked by dangerous and neutral objects matched on graspability (both graspable and ungraspable, Experiment 2a), or by graspable and ungraspable objects matched on dangerousness (both neutral and dangerous, Experiment 2b). Results confirmed the finding of Experiment 1, but also indicated that participants misperceived the line midpoint toward the ungraspable object when it was presented, being it dangerous or not. This evidence demonstrated sensitivity to object dangerousness maintained across lifespan. The emergence of aversive affordances evoked by dangerous graspable objects strenghtens the importance to consider graspability in the investigation of dangerous objects. Possible neural mechanisms involved in the processing of dangerous graspable objects are discussed.

The field of numerical cognition represents an interesting case for action-based theories of cognition, since number is a special kind of abstract concept. Several studies have shown that within the parietal lobes adjacent neural regions code numerical magnitude and grasping-related information. This anatomical proximity between brain areas involved in number and sensorimotor processes may account for interactions between numerical magnitude and action. In particular, recent studies have demonstrated a causal role of action perception on numerical magnitude processing. If objects are represented in terms of actions (affordances), the causal role of action on number processing should extend to the case of objects affordances. This study investigates the relationship between numbers and objects affordances in two experiments, without (Experiment 1) or with (Experiment 2) the requirement of an action (i.e., participants were asked to hold an object in their hands during the task). The task consisted in repeating aloud the odd or even digit within a pair depending on the type of the preceding or following object. Order of presentation (object-number vs. number-object), Object type (graspable vs. ungraspable), Object size (small vs. large), and Numerical magnitude (small vs. large) were manipulated for each experiment. Experiment 1 showed a facilitation - in terms of quicker responses - for graspable over ungraspable objects preceded by numbers, and an effect of numerical magnitude after the presentation of graspable objects. Experiment 2 demonstrated that the action execution enhanced overall the sensitivity to numerical magnitude, and that at the same time it interfered with the effects of objects affordances on number processing. Overall, these findings demonstrate that numbers and graspable objects are strongly interrelated, supporting the view that abstract concepts may be grounded in the motor experience.

The functional specialization of the ventral stream in Perception and the dorsal stream in Action is the cornerstone of the leading model proposed by Goodale and Milner in 1982. This model is based on neuropsychological evidence and has been a matter of debate for almost three decades, during which the dual-visual stream hypothesis has received much attention, including support and criticisms. The advent of functional magnetic resonance imaging (fMRI) has allowed investigating the brain areas involved in Perception and Action and provided useful data on the functional specialization of the two streams. Research on this topic has been quite prolific, yet very little attempt has been made so far to identify consistent neuroimaging results across the available literature. In particular, no meta-analysis has explored the spatial convergence in the involvement of the two streams in Action. The present meta-analysis (N=53) was designed to reveal the specific neural activations associated with Action (i.e., grasping and reaching movements), and the extent to which visual information affects the involvement of the two streams during motor control. Our results provide a comprehensive view of the consistent and spatially convergent neural correlates of Action based on neuroimaging studies conducted over the past two decades. We discuss our results in light of the well-established dual-visual stream model and frame these findings in the context of recent discoveries obtained with advanced fMRI methods, such as multivoxel pattern analysis.