Barbara Penolazzi

Differences in the perception and time course of syntactic and semantic violations.

A reading time and an ERP experiment conducted in Italian investigated the parsers responses to a syntactic violation (subject-verb number agreement) and to a semantic violation (subject-verb selectional restriction), examining the time course of comprehension processes until sentence end. The reading-time data showed that the syntactic violation was detected earlier than the semantic one and that the two violations differed in the time-course. The ERP data fully supported the reading time data: Syntactic anomalies elicited a left anterior negativity (LAN) and a P600. Semantic anomalies elicited a N400 centred on the parietal sites which started 90 ms later (latency 430 ms) than the LAN. Furthermore, the N400 evoked by the words that followed the target word continued and increased until sentence end. The results are discussed with respect to the hypotheses that the parser constructs distinct syntactic and semantic analyses of a sentence and that this characteristic holds cross-linguistically. The appropriateness of different methodologies to the study of sentence processing is also evaluated.

Effects of Transcranial Direct Current Stimulation on episodic memory related to emotional visual stimuli.

The present study investigated emotional memory following bilateral transcranial electrical stimulation (direct current of 1 mA, for 20 minutes) over fronto-temporal cortical areas of healthy participants during the encoding of images that differed in affective arousal and valence. The main result was a significant interaction between the side of anodal stimulation and image emotional valence. Specifically, right anodal/left cathodal stimulation selectively facilitated the recall of pleasant images with respect to both unpleasant and neutral images whereas left anodal/right cathodal stimulation selectively facilitated the recall of unpleasant images with respect to both pleasant and neutral images. From a theoretical perspective, this double dissociation between the side of anodal stimulation and the advantage in the memory performance for a specific type of stimulus depending on its pleasantness supported the specific-valence hypothesis of emotional processes, which assumes a specialization of the right hemisphere in processing unpleasant stimuli and a specialization of the left hemisphere in processing pleasant stimuli. From a methodological point of view, first we found tDCS effects strictly dependent on the stimulus category, and second a pattern of results in line with an interfering and inhibitory account of anodal stimulation on memory performance. These findings need to be carefully considered in applied contexts, such as the rehabilitation of altered emotional processing or eye-witness memory, and deserve to be further investigated in order to understand their underlying mechanisms of action.

Cortical brain responses to semantic incongruity and syntactic violation in Italian language: an event-related potential study

The present experiment investigated cortical responses of native Italian subjects during reading of short sentences including semantic or morphosyntactic violations. Given the specificity of the Italian language in which the sequencing of words is relatively more free than in English or other languages, we investigated whether syntactic and semantic violations were able to elicit event-related potential (ERP) components similar to those found in other languages. Cortical potentials evoked by the anomalous target word were recorded at frontal, central and parietal electrodes. Results showed that, in Italian, semantic anomaly elicited a negative wave (N400) in the 400-500 ms time-window and syntactic error evoked a slower positive wave (P600) in the 500-700 ms time-window. Syntactic error also evoked a significant left anterior negativity in the 350-450 ms time-window, supporting the view that syntactic processes precedes semantic analysis. Thus, Italian language, notwithstanding its specificity, shows ERPs responses to semantic and syntactic violations, with effects, scalp distribution and latency similar to those found in German, Dutch and English. Results point to a cross-linguistic consistency of the semantic and syntactic ERP components associated with the detection of linguistic anomalies.

Delta EEG activity as a marker of dysfunctional linguistic processing in developmental dyslexia

The present study used delta EEG band to test the hypothesis of a cerebral maturational delay and a functional altered cerebral asymmetry for phonological processing in dyslexic children. A group of 14 children with dyslexia and 28 matched controls participated in a linguistic paradigm in which the same words were processed in three tasks: phonological, semantic, and orthographic. Delta amplitude was computed as an index of cortical inhibition in four different phases of word processing. In anterior sites, controls showed left activation (reduced delta) during the phonological task and bilateral activation in the other two tasks. Conversely, children with dyslexia showed greater overall delta amplitude, indexing a cerebral maturation delay and an altered language laterality pattern. In the phonological task they had larger left anterior delta (inhibition of left frontal linguistic locations) and smaller left posterior delta amplitude (activation of left posterior sites silent in controls). Results support the phonological deficit hypothesis of developmental dyslexia and the validity of EEG delta band as functional and clinical measure of language laterality.

Electrode montage dependent effects of transcranial direct current stimulation on semantic fluency

Transcranial direct current stimulation (tDCS) has proved to be valuable in improving many language processes. However, its influence on verbal fluency still needs to be fully proved. In the present study, we explored the effects of different electrode montages on a semantic fluency task, aimed at comparing their effectiveness in affecting language production. Ninety healthy, right-handed volunteers were randomly assigned to receive one of the following stimulation protocols: (1) anode over the left frontal cortex/cathode over the right supraorbital (rSO) area, (2) anode over the left fronto-temporal (lFT) cortex/cathode over the rSO area, (3) anode over the lFT cortex/cathode over the right FT cortex, (4) anode over the lFT cortex/big-size cathode over the rSO area, (5) sham. In the active stimulation conditions, 2 mA current was delivered for 20 min. Participants performed the semantic fluency task before the stimulation, immediately after it, and 15 min after the first post-stimulation task. Although none of the different protocols improved language production immediately after the stimulation, anodal stimulation over the left frontal cortex (standard-size cathode over the rSO area) improved fluency at the second post-stimulation task. This proved that small differences in either active electrode positioning, or reference positioning/size can impact tDCS behavioral effects also in the cognitive domain. These findings, which can be sometimes missed when tested immediately after the stimulation only, add new information on tDCS spatial and temporal features, thus providing new indications to increase the effectiveness of stimulation protocols.

Event-related brain potentials uncover activation dynamics in the lexicon of multiplication facts

The present study was designed to ascertain whether the cortical dynamics underlying multiplication fact retrieval can be modulated as a function of arithmetic relatedness. To this end, event-related brain potentials (ERPs) were recorded from 22 participants engaged in a number-matching task. The task was to decide whether a single probe number had been shown as part of a previously presented pair of cue numbers. Probes in the non-matching condition (50% of total trials) were either the product of the cue numbers (strong cue-probe association), the multiple of either cue numbers (weak cue-probe association), or an arithmetically neutral number with respect to the cue numbers (no cue-probe association). Behavioral data showed a clear interference effect (LeFevre interference), in that performance in the non-matching condition was significantly better when the probe number was arithmetically neutral compared to when it was arithmetically related to the cue digits either strongly (i.e., through the product) or weakly (i.e., through its neighbor in the multiplication table). LeFevre interference was not statistically different in magnitude for the two arithmetically related conditions. In contrast, ERPs allowed us to dissociate cortical processing dynamics for these latter conditions: whereas initially (250-350 ms) both product and neighbor probes evoked a relatively more pronounced positivity compared to neutral probes, in a later interval (350-450 ms, N400-like component), neighbors critically diverged from products, showing relatively more negative values, similar to those of neutral probes. The observed dissociation in ERP measures is interpreted as evidence of activation spreading in the network of multiplication facts, with the short-lasting response elicited by neighbors likely reflecting activation dissipating over time because of a weaker association to the cue digits.

Brain plasticity in developmental dyslexia after phonological treatment: A beta EEG band study

Linguistic EEG hemispheric reorganization was investigated in 14 dyslexic children after a 6-month phonological training (10 min/day through PC software). Error rates from three linguistic tasks significantly decreased and reading speed improved after the training. A significant positive correlation (r(12)=0.536) was found at posterior sites for the phonological task only, showing that those children who had the greatest reading speed enhancement showed the largest left posterior EEG beta power increase.

Human Memory Retrieval and Inhibitory Control in the Brain: Beyond Correlational Evidence

Retrieving information from long-term memory can result in the episodic forgetting of related material. One influential account states that this retrieval-induced forgetting (RIF) phenomenon reflects inhibitory mechanisms called into play to decrease retrieval competition. Recent neuroimaging studies suggested that the prefrontal cortex, which is critically engaged in inhibitory processing, is also involved in retrieval competition situations. Here, we used transcranial direct current stimulation (tDCS) to address whether inhibitory processes could be causally linked to RIF. tDCS was administered over the right dorsolateral prefrontal cortex during the retrieval-practice phase in a standard retrieval-practice paradigm. Sixty human participants were randomly assigned to anodal, cathodal, or sham-control groups. The groups showed comparable benefits for practiced items. In contrast, unlike both the sham and anodal groups, the cathodal group exhibited no RIF. This pattern is interpreted as evidence for a causal role of inhibitory mechanisms in episodic retrieval and forgetting.

Inverted EEG theta lateralization in dyslexic children during phonological processing.

The phonological deficit hypothesis of dyslexia has been investigated in the present research by analysing language-related lateralization of the EEG theta band in a sample of dyslexic children. To this aim, a paradigm based on word-pair visual presentation was used in which the same words were processed in Semantic and Phonological tasks. Theta band amplitude, a cortical index that has been related to working memory processing, was analysed during four different phases of word elaboration, thus allowing to measure also the temporal dynamics of word reading/encoding in the verbal working memory. Control subjects showed a specific (and therefore efficient) task-related and time-dependent cortical activation: a peak of theta activity during word reading was found that decayed during the next inter stimulus interval. Furthermore, during word presentation in the Phonological task, theta amplitude was greater on the left hemisphere. Dyslexics evidenced an altered pattern of theta activation both in the temporal dimension and in the cortical space: their peak of activity was delayed to the first inter stimulus interval after word offset and was shifted to the right hemisphere throughout the whole epoch of Phonological task and in two phases of the Semantic task. Analysis of alpha band failed to replicate the complex pattern of lateralization found for theta band in the two groups, a result that suggests a specific functional role of theta band, which cannot be interpreted as a simple marker of cortical inhibition. Results point to a deficit, in dyslexic children, to recruit left hemisphere structures for the elaboration of the phonological component of the verbal working memory. This deficit was marked by a different, unspecific and dysfunctional hemispherical asymmetry of theta activation to language, a deficit that involved also the time course of phonological linguistic elaboration.

Individual differences affecting caffeine intake. Analysis of consumption behaviours for different times of day and caffeine sources.

The main purpose of the present study was to investigate the individual variables contributing to determine the high variability in the consumption behaviours of caffeine, a psychoactive substance which is still poorly investigated in comparison with other drugs. The effects of a large set of specific personality traits (i.e., Impulsivity, Sensation Seeking, Anxiety, Reward Sensitivity and Circadian Preference) were compared along with some relevant socio-demographic variables (i.e., gender and age) and cigarette smoking behaviour. Analyses revealed that daily caffeine intake was significantly higher for males, older people, participants smoking more cigarettes and showing higher scores on Impulsivity, Sensation Seeking and a facet of Reward Sensitivity. However, more detailed analyses showed that different patterns of individual variables predicted caffeine consumption when the times of day and the caffeine sources were considered. The present results suggest that such detailed analyses are required to detect the critical predictive variables that could be obscured when only total caffeine intake during the entire day is considered.