Robust inference of causality in high-dimensional dynamical processes from the Information Imbalance of distance ranks.

We introduce an approach which allows detecting causal relationships between variables for which the time evolution is available. Causality is assessed by a variational scheme based on the Information Imbalance of distance ranks, a statistical test capable of inferring the relative information content of different distance measures. We test whether the predictability of a putative driven system Y can be improved by incorporating information from a potential driver system X, without explicitly modeling the underlying dynamics and without the need to compute probability densities of the dynamic variables. This framework makes causality detection possible even between high-dimensional systems where only few of the variables are known or measured. Benchmark tests on coupled chaotic dynamical systems demonstrate that our approach outperforms other model-free causality detection methods, successfully handling both unidirectional and bidirectional couplings. We also show that the method can be used to robustly detect causality in human electroencephalography data.

The more numerous the longer: how the integration between numerosity and time leads to a common neural response.

If you are stuck in a traffic jam, the more numerous the queuing cars are, the longer you expect to wait. Time and numerosity are stimulus dimensions often associated in the same percept and whose interaction can lead to misjudgements. At brain level it is unclear to which extent time and numerosity recruit same/different neural populations and how their perceptual integration leads to changes in these populations' responses. Here we used high-spatial-resolution functional magnetic resonance imaging with neural model-based analyses to investigate how the topographic representations of numerosity and time change when these dimensions are varied together on the same visual stimulus in a congruent (the more numerous the items, the longer the display time) or incongruent manner. Compared to baseline conditions, where only one dimension was changed at a time, the variation of both stimulus dimensions led to changes in neural population responses that became more sensitive either to the two features or to one of them. Magnitude integration led also to degradation of topographies and shifts in response preferences. These changes were more pronounced in the comparison between parietal and frontal maps. Our results while pointing to partially distinct representations of time and numerosity show a common neural response to magnitude integration.

Pupil dilation during orienting of attention and conscious detection of visual targets in patients with left spatial neglect.

Right Brain-Damaged patients (RBD) with left spatial neglect (N+), are characterised by deficits in orienting and re-orienting attention to stimuli in the contralesional left side of space. In a recent ERPs study with visual stimuli (Lasaponara et al., 2018) we have pointed out that the pathological attentional bias of N+ is matched with exaggerated novelty reaction and contextual updating of targets in the right ipsilesional space and reduced novelty reaction and contextual updating of targets in the left contralesional space. To characterise further the attentional performance of N+, here we measured Pupil Dilation (PDil), which is a reliable marker of noradrenergic-locus coeruleus activity and response to unexpected events/rewards. Compared to Neutral and Valid targets, N+ patients displayed a pathological reduction of PDil in response to infrequent Invalid targets in the left side of space, while in Healthy Controls (HC) and RBD without neglect (N-) the same targets enhanced PDil with respect to Neutral and frequent Valid targets. Invalid targets in the right side of space enhanced PDil in all experimental groups. Interestingly, both N- and N+ showed a consistent number of target omissions both in the left and right side of space. With respect to seen targets, N- showed reduced PDil in response to unseen targets both in the left and right side of space. In contrast, N+ had reduced PDil in response to unseen targets in the left side of space though not in the right side, where seen and unseen targets evoked comparable levels of PDil. These results disclose, for the first time, the PDil correlates of spatial attention in left spatial neglect and suggest that the pathological attentional bias suffered by N+ might enhance the autonomic responses reflected in PDil to unseen ipsilesional stimuli. This enhancement can contribute to biasing contextual updating and predictive coding of stimuli in the ipsilesional space, thus worsening the pathological attentional bias of N+.

Expectancy modulates pupil size both during endogenous orienting and during re-orienting of spatial attention: A study with isoluminant stimuli.

We have recently demonstrated that when endogenous orienting of spatial attention is guided by central directional cues that reliably predict the position of lateral targets. Pupil Dilation (PDil) is higher as compared with directional cues that do not predict target position. These findings were interpreted as reflecting different levels of Locus Coeruleus-Noradrenergic activity during endogenous orienting. In contrast to this, we were not able to highlight reliable differences between PDil responses to infrequent invalid targets that are associated with predictive cues and frequent invalid targets that are associated with non-predictive ones. These null findings might have been due to the spurious influence of transitory changes in luminance at the moment of target presentation or to the short time window used for the analysis of target-related changes in PDil. Here, we re-explored cue- and target-related changes in PDil using cue and target stimuli that were kept isoluminant to their background and long lasting cue and target periods for data recording and analysis. We fully replicate our previous cue-related results and, in addition, we demonstrate that infrequent invalid targets in the predictive experimental condition evoke larger PDil as compared with frequent ones. Analyses with Linear Mixed Models highlighted that both during the cue and target period, higher levels of PDil were associated with slower reaction times. These findings confirm that PDil is a reliable marker of the expectancy components of endogenous cue-related and exogenous target-related orienting of spatial attention.

Visualising numerals: An ERPs study with the attentional SNARC task.

Inspecting or transforming the position of Arabic numbers in mental space helps everyday mathematical calculations. Nonetheless the neural and functional bases of this ability are poorly understood. Here we show that imagining the position of Arabic numbers on a horizontal mental number line speeds up the detection of targets appearing at corresponding positions in visual space. No similar advantage is found when numbers are merely perceived or classified according to their magnitude. Imagery enhanced electrophysiological activity in the extrastriate cortex contralateral to the imagined number position. Speeded detection of targets that were spatially congruent with the imagined number position was matched with enhanced C1 responses in primary visual cortex. In contrast, imagery had no effect on later target-related responses that are usually modulated by spatial attention. These results shed new light on the mechanisms that evoke sensory-like spatial representations of Arabic numbers in everyday mental computations.

Can you change my preferences? Effect of social influence on intertemporal choice behavior.

The present study presents a novel social observation paradigm to examine whether temporal discounting (TD) can be modulated in a specific direction. In particular, after estimating a baseline discount rate, we exposed subjects to a pattern of choice that was opposite to their baseline preferences, i.e., subjects preferring immediate over delayed rewards were exposed to a farsighted pattern of behavior and vice-versa. The results showed a significant decrease of the discount rate in the discounter group and an increase in the farsighted group. The effect was mainly guided by a modification of the subjective values at short time delays and was stronger in subjects with extreme, compared to mild, baseline preferences. Importantly, the magnitude and direction of the effect predicted the baseline preferences. These findings have potentially very relevant implications for the prevention and treatment of clinical conditions, such as addition-related disorders, characterized by severe impairments of decision-making mechanisms.