Alberto Yorio

Expectancy modulates a late positive ERP in an artificial grammar task

A wide range of studies have found late positive ERP components in response to anomalies during processing of structured sequences. In language studies, this component is named Syntactic Positive Shift (SPS) or P600. It is characterized by an increase in potential peaking around 600 ms after the appearance of the syntactic anomaly and has a centroparietal topography. Similar late positive components were found more recently in non-linguistic contexts. These results have led to the hypothesis that these components index the detection of anomalies in rule-governed sequences, or the access to abstract rule representations, regardless of the nature of the stimuli. Additionally, there is evidence showing that the SPS/P600 is sensitive to probability manipulations, which affect the subjects expectancy of the stimuli. Our aim in the present work was to address the hypothesis that the late positive component is modulated by the subjects expectancy of the stimuli. To do so, we employed an artificial grammar learning task, and controlled the frequency of presentation to different kind of sequences during training. Results showed that certain sequence types elicited a late positive component which was modulated by different factors in two distinct time windows. In an earlier window, the component was higher for sequences which had a low or null probability of occurrence during training, while in a later window, the component was higher for incorrect than correct sequences. Furthermore, this late window effect was absent in those subjects whose performance was not significantly above chance. Two possible explanations for this effect are suggested.

On the learnability of frequent and infrequent word orders: An artificial language learning study

Most languages have a basic or “canonical” word order, which determines the relative positions of the subject (S), the verb (V), and the object (O) in a typical declarative sentence. The frequency of occurrence of the six possible word orders among world languages is not distributed uniformly. While SVO and SOV represent around 85% of world languages, orders like VSO (9%) or OSV (0.5%) are much less frequent or extremely rare. One possible explanation for this asymmetry is that biological and cognitive constraints for structured sequence processing make some word orders easier to be processed than others. Therefore, the high frequency of these word orders would be related to their higher learnability. The aim of the present study was to compare the learnability of different word orders between groups of adult subjects. Four artificial languages with different word orders were trained: two frequent (SVO, SOV) and two infrequent (VSO, OSV). In a test stage, subjects were asked to discriminate between new correct sentences and syntax or semantic violations. Higher performance rates and faster responses were observed for more frequent word orders. The results support the hypothesis that more frequent word orders are more easily learned.

ERP correlates of priming in language and stimulus equivalence: Evidence of similar N400 effects in absence of semantic content

Semantic priming has been widely observed at both behavioral and electrophysiological levels as reductions in response times and N400 magnitudes respectively. However, the possibility that stimulus relations derived from associative learning elicit N400 priming effects comparable to those found in language has not been properly addressed yet. Equivalence relations emerge after establishing a set of arbitrary and intra-experimentally defined relations through associative learning, thus allowing the study of derived stimulus relations in the absence of semantic content. The present study aimed to compare ERP correlates of priming in semantically related words and pseudowords related through equivalence. We found similar behavioral and N400 effects when comparing unrelated vs related prime-target pairs in language and stimulus equivalence tasks, suggesting that priming engages at least partially overlapping neural mechanisms in both contexts. In addition, we found a posteriorly distributed late positivity in the semantic priming task only, which may be reflecting language-specific processing.

P32-13 A P600 component in an artificial grammar without semantics: an EEG study of structural violation type

Objective: The anterior N2 is a component of the event-related brain potential (ERP) elicited by visual novel stimuli. Previous studies reported that the stimuli which were subsequently viewed for longer periods of time elicited a larger anterior N2 than the stimuli viewed for shorter periods of time. This study examines how the complexity of visual materials affects the anterior N2 and subsequent viewing duration. Methods: Sixteen student participants viewed a total of 120 novel polygons with three different levels of complexity (12, 24, and 48 sides). They were asked to look at the figures one by one for as long as they wished. ERPs time-locked to the stimulus onset were averaged separately for three levels of complexity (12, 24, and 48 sides). In addition, ERPs were averaged separately for the stimuli viewed longer or shorter than the median viewing time at each complexity level by individual participants. Results: The more complex the stimuli, the larger the anterior negativity (N2) between 200 and 300 ms after stimulus onset. Moreover, the more complex the stimuli, the longer the viewing duration. However, when the stimuli were classified into longerand shorter-viewed figures, no difference in the anterior N2 amplitude was found. Conclusions: Results suggest that the anterior N2 is elicited by complex visual stimuli that require further attentional processing. As suggested in previous studies, this initial brain response can correlate with subsequent viewing duration. However, this study shows that there is no causal relationship between the anterior N2 and visual exploration.

229. An ERP study of category learning

dren of the same age. A NFB treatment was applied to 6 MMR children (IQ between 50 and 69), 6–11 years old (two boys) with normal neurological exam and abnormally higher theta/alpha ratio for their age. Positive reinforcement (tone of 500 Hz) was given when theta/alpha ratio was below a previously specified threshold. NFB training consisted of 30 sessions of 30 min each one. Significant changes in behaviour (IQ, Task of Attention Variables, and academic achievement) and EEG (reduction of theta Absolute Power and delta Relative Power, and increase of alpha and beta Relative Power) were observed. These changes were more apparent two months after NFB treatment. This NFB protocol is useful for the treatment of MMR children. This is the first report in MMR children using NFB.