Stefano Lasaponara

Learning about time: plastic changes and interindividual brain differences.

Learning the timing of rapidly changing sensory events is crucial to construct a reliable representation of the environment and to efficiently control behavior. The neurophysiological mechanisms underlying the learning of time are unknown. We used functional and structural magnetic resonance imaging to investigate neurophysiological changes and individual brain differences underlying the learning of time in the millisecond range. We found that the representation of a trained visual temporal interval was associated with functional and structural changes in a sensory-motor network including occipital, parietal, and insular cortices, plus the cerebellum. We show that both types of neurophysiological changes correlated with changes of performance accuracy and that activity and gray-matter volume of sensorimotor cortices predicted individual learning abilities. These findings represent neurophysiological evidence of functional and structural plasticity associated with the learning of time in humans and highlight the role of sensory-motor circuits in the perceptual representation of time in the millisecond range.

Spatial attention and conscious perception: the role of endogenous and exogenous orienting

Attention has often been considered to be a gateway to consciousness (Posner, Proceedings of the National Academy of Sciences of the United States of America, 91(16), 7398–7403, 1994). However, its relationship with conscious perception (CP) remains highly controversial. While theoretical models and experimental data support the role of attention in CP (Chica, Lasaponara, Lupiáñez, Doricchi, & Bartolomeo, NeuroImage, 51, 1205–1212, 2010; Dehaene, Changeux, Naccache, Sackur, & Sergent, Trends in Cognitive Sciences, 10, 204–211, 2006; Mack & Rock, Inattentional blindness,1998), recent studies have claimed that at least some forms of attention—endogenous or top-down spatial attention—are neither sufficient nor necessary for CP (Koch & Tsuchiya, Trends in Cognitive Sciences, 11, 16–22, 2007). In the present experiments, we demonstrate the importance of exogenously triggered attention for the modulation of CP. Weak or null effects were instead observed when attention was triggered endogenously. Our data are discussed in the framework of recent neuropsychological models (Dehaene et al., Trends in Cognitive Sciences, 10, 204–211, 2006), postulating that activity within reverberating frontoparietal networks, as colocalized with spatial--orienting systems, is the brain correlate of consciously processed information.

Exogenous attention can capture perceptual consciousness: ERP and behavioural evidence

Attention has often been conceived as the gateway to consciousness. However, recent research points to the independence of top-down or endogenous attention and conscious perception, while the role of bottom-up or exogenous attention in conscious perception remains largely unexplored. Here, we present behavioural and electrophysiological evidence exploring the role of exogenous attention in conscious perception. Using peripheral non-informative cues, exogenous attention was oriented either to the same location of a near-threshold target (valid cues), or to the opposite location (invalid cues). Confirming previous research, consciously perceived targets elicited a larger P300 than unseen targets. Importantly, analysis of cue-locked potentials revealed the novel finding that there was a systematic relationship between the amplitude of a P100 component elicited by the cues and the conscious perception of the targets. Valid cues led to the conscious perception of the subsequent targets when they captured attention to their location, as indexed by the P100 component distributed over occipito-parietal areas. On the other hand, invalid cues led to the conscious perception of the subsequent targets only when they failed to capture attention at their location (opposite to the target location). These results suggest that exogenous orienting plays a crucial role in conscious perception.

Changes in predictive cuing modulate the hemispheric distribution of the P1 inhibitory response to attentional targets

ABSTRACT Brain activity related to orienting of attention with spatial cues and brain responses to attentional targets are influenced the probabilistic contingency between cues and targets. Compared to predictive cues, cues predicting at chance the location of targets reduce the filtering out of uncued locations and the costs in reorienting attention to targets presented at these locations. Slagter et al. (2016) have recently suggested that the larger target related P1 component that is found in the hemisphere ipsilateral to validly cued targets reflects stimulus‐driven inhibition in the processing of the unstimulated side of space contralateral to the same hemisphere. Here we verified whether the strength of this inhibition and the amplitude of the corresponding P1 wave are modulated by the probabilistic link between cues and targets. Healthy participants performed a task of endogenous orienting once with predictive and once with non‐predictive directional cues. In the non‐predictive condition we observed a drop in the amplitude of the P1 ipsilateral to the target and in the costs of reorienting. No change in the inter‐hemispheric latencies of the P1 was found between the two predictive conditions. The N1 facilitatory component was unaffected by predictive cuing. These results show that the predictive context modulates the strength of the inhibitory P1 response and that this modulation is not matched with changes in the inter‐hemispheric interaction between the P1 generators of the two hemispheres. HIGHLIGHTSNon‐predictive directional cues reduce the filtering out of uncued target locations.The P1 ipsilateral to target side reflects inhibition of contralateral no‐target side.We tested whether cue predictiveness modulates the amplitude of the ipsilateral P1.Non‐predictive cues reduced the ipsilateral P1 with no effect on its latency or on N1.The strength of P1‐related inhibition depends on the probabilistic cue‐target link.

Selective reorienting response of the left hemisphere to invalid visual targets in the right side of space: relevance for the spatial neglect syndrome.

Selective reorienting response of the left hemisphere to invalid visual targets in theright side of space: relevance for the spatial neglect syndromeAlessio Dragone, Stefano Lasaponara, Massimo Silvetti, Emiliano Macaluso, FabrizioDoricchi, PhDPII: S0010-9452(14)00412-2DOI: 10.1016/j.cortex.2014.12.009Reference: CORTEX 1356To appear in: CortexReceived Date: 14 August 2014Revised Date: 27 October 2014Accepted Date: 11 December 2014Please cite this article as: Dragone A, Lasaponara S, Silvetti M, Macaluso E, Doricchi F, Selectivereorienting response of the left hemisphere to invalid visual targets in the right side of space: relevancefor the spatial neglect syndrome, CORTEX (2015), doi: 10.1016/j.cortex.2014.12.009.This is a PDF file of an unedited manuscript that has been accepted for publication. As a service toour customers we are providing this early version of the manuscript. The manuscript will undergocopyediting, typesetting, and review of the resulting proof before it is published in its final form. Pleasenote that during the production process errors may be discovered which could affect the content, and alllegal disclaimers that apply to the journal pertain.

EEG correlates of preparatory orienting, contextual updating and inhibition of sensory processing in left spatial neglect.

Studies with event-related potentials have highlighted deficits in the early phases of orienting to left visual targets in right-brain-damaged patients with left spatial neglect (N+). However, brain responses associated with preparatory orienting of attention, with target novelty and with the detection of a match/mismatch between expected and actual targets (contextual updating), have not been explored in N+. Here in a study in healthy humans and brain-damaged patients of both sexes we demonstrate that frontal activity that reflects supramodal mechanisms of attentional orienting (Anterior Directing Attention Negativity, ADAN) is entirely spared in N+. In contrast, posterior responses that mark the early phases of cued orienting (Early Directing Attention Negativity, EDAN) and the setting up of sensory facilitation over the visual cortex (Late Directing Attention Positivity, LDAP) are suppressed in N+. This uncoupling is associated with damage of parietal-frontal white matter. N+ also exhibit exaggerated novelty reaction to targets in the right side of space and reduced novelty reaction for those in the left side (P3a) together with impaired contextual updating (P3b) in the left space. Finally, we highlight a drop in the amplitude and latency of the P1 that over the left hemisphere signals the early blocking of sensory processing in the right space when targets occur in the left one: this identifies a new electrophysiological marker of the rightward attentional bias in N+. The heterogeneous effects and spatial biases produced by localized brain damage on the different phases of attentional processing indicate relevant functional independence among their underlying neural mechanisms and improve the understanding of the spatial neglect syndrome. SIGNIFICANCE STATEMENT Our investigation answers important questions: are the different components of preparatory orienting (EDAN, ADAN, LDAP) functionally independent in the healthy brain? Is preparatory orienting of attention spared in left spatial neglect? Does the sparing of preparatory orienting have an impact on deficits in reflexive orienting and in the assignment of behavioral relevance to the left space? We show that supramodal preparatory orienting in frontal areas is entirely spared in neglect patients though this does not counterbalance deficits in preparatory parietal-occipital activity, reflexive orienting, and contextual updating. This points at relevant functional dissociations among different components of attention and suggests that improving voluntary attention in N+ might be behaviorally ineffective unless associated with stimulations boosting the response of posterior parietal-occipital areas.

The influence of visual and phonological features on the hemispheric processing of hierarchical Navon letters

&NA; The possibility of allocating attentional resources to the “global” shape or to the “local” details of pictorial stimuli helps visual processing. Investigations with hierarchical Navon letters, that are large “global” letters made up of small “local” ones, consistently demonstrate a right hemisphere advantage for global processing and a left hemisphere advantage for local processing. Here we investigated how the visual and phonological features of the global and local components of Navon letters influence these hemispheric advantages. In a first study in healthy participants, we contrasted the hemispheric processing of hierarchical letters with global and local items competing for response selection, to the processing of hierarchical letters in which a letter, a false‐letter conveying no phonological information or a geometrical shape presented at the unattended level did not compete for response selection. In a second study, we investigated the hemispheric processing of hierarchical stimuli in which global and local letters were both visually and phonologically congruent (e.g. large uppercase G made of smaller uppercase G), visually incongruent and phonologically congruent (e.g. large uppercase G made of small lowercase g) or visually incongruent and phonologically incongruent (e.g. large uppercase G made of small lowercase or uppercase M). In a third study, we administered the same tasks to a right brain damaged patient with a lesion involving pre‐striate areas engaged by global processing. The results of the first two experiments showed that the global abilities of the left hemisphere are limited because of its strong susceptibility to interference from local letters even when these are irrelevant to the task. Phonological features played a crucial role in this interference because the interference was entirely maintained also when letters at the global and local level were presented in different uppercase vs. lowercase formats. In contrast, when local features conveyed no phonological information, the left hemisphere showed preserved global processing abilities. These findings were supported by the study of the right brain damaged patient. These results offer a new look at the hemispheric dominance in the attentional processing of the global and local levels of hierarchical stimuli. HighlightsWe investigated how features of Navon letters influence hemispheric advantages.RH and LH are able to process global aspects of Navon letters.LH demonstrates a strong susceptibility to interference due to phonological features.

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.