Neural correlates of unconventional verb extensions reveal preschoolers' analogical abilities.

In the current event-related potential (ERP) study, we assessed 4-year-olds' ability to extend verbs to new action events on the basis of abstract similarities. Participants were presented with images of actions (e.g., peeling an orange) while hearing sentences containing a conventional verb (e.g., peeling), a verb sharing an abstract relation (i.e., an analogical verb, e.g., undressing), a verb sharing an object type (i.e., an object-related verb, e.g., pressing) with the action, or a pseudoverb (e.g., kebraying). The amplitude of the N400 gradually increased as a function of verb type-from conventional verbs to analogical verbs to object-related verbs to pseudoverbs. These findings suggest that accessing the meaning of a verb is easier when it shares abstract relations with the expected verb. Our results illustrate that measuring brain signals in response to analogical word extensions provides a useful tool to investigate preschools' analogical abilities.

Electrophysiological Evidence for A Number-Action Mapping in Infancy.

In the last decades, a growing body of literature has focused on the link between number and action. Many studies conducted on adult participants have provided evidence for a bidirectional influence between numerosity processing and grasping or reaching actions. However, it is not yet clear whether this link is functional in early infancy. Here, we used the event-related potential (ERP) technique to record electrical activity of the brain in response to number-hand pairings. We implemented a cueing paradigm where 3- to 4-month-old infants observed images showing either congruency (e.g., a large numerosity primed by a large hand opening) or incongruency (e.g., a large numerosity primed by a small hand opening). Infants' brain activity was modulated by the congruency of the pairings: amplitudes recorded over frontal and parietal-occipital scalp positions differed for congruent versus incongruent pairings. These findings suggest that the association between number and hand action processing is already functional early in life.

Do Children With Developmental Language Disorder Activate Scene Knowledge to Guide Visual Attention? Effect of Object-Scene Inconsistencies on Gaze Allocation.

Our visual environment is highly predictable in terms of where and in which locations objects can be found. Based on visual experience, children extract rules about visual scene configurations, allowing them to generate scene knowledge. Similarly, children extract the linguistic rules from relatively predictable linguistic contexts. It has been proposed that the capacity of extracting rules from both domains might share some underlying cognitive mechanisms. In the present study, we investigated the link between language and scene knowledge development. To do so, we assessed whether preschool children (age range = 5;4-6;6) with Developmental Language Disorder (DLD), who present several difficulties in the linguistic domain, are equally attracted to object-scene inconsistencies in a visual free-viewing task in comparison with age-matched children with Typical Language Development (TLD). All children explored visual scenes containing semantic (e.g., soap on a breakfast table), syntactic (e.g., bread on the chair back), or both inconsistencies (e.g., soap on the chair back). Since scene knowledge interacts with image properties (i.e., saliency) to guide gaze allocation during visual exploration from the early stages of development, we also included the objects' saliency rank in the analysis. The results showed that children with DLD were less attracted to semantic and syntactic inconsistencies than children with TLD. In addition, saliency modulated syntactic effect only in the group of children with TLD. Our findings indicate that children with DLD do not activate scene knowledge to guide visual attention as efficiently as children with TLD, especially at the syntactic level, suggesting a link between scene knowledge and language development.

Effect of language experience on selective auditory attention: An event-related potential study.

Dual language experience has typically been shown to improve various executive control functions. We investigated with event-related brain potentials (ERPs) recorded from early (natively) bilingual speakers and control participants whether it also affects auditory selective attention. We delivered to our participants two tone streams, one to the left and one to the right ear. Both streams consisted of standard tones and two types of infrequent deviant tones which had either an enhanced duration or intensity. The participants were instructed to attend either to the right or left stream and to detect longer-duration deviants in the attended stream. The results showed that the early bilinguals did not outperform the controls in target detection accuracy or speed. However, the late portion of the attention-related ERP modulation (the negative difference, Nd) was larger over the left hemisphere in the early bilinguals than in the controls, suggesting that the maintenance of selective attention or further processing of selectively attended sounds is enhanced in the bilinguals. Moreover, the late reorienting negativity (RON) in response to intensity-deviant tones was larger in the bilinguals, suggesting more efficient disengagement of attention from distracting auditory events. Hence, our results demonstrate that brain responses associated with certain aspects of auditory attention are enhanced in the bilingual adults, indicating that early dual language exposure modulates the neuronal responsiveness of auditory modality.

Gaze distribution analysis and saliency prediction across age groups.

Knowledge of the human visual system helps to develop better computational models of visual attention. State-of-the-art models have been developed to mimic the visual attention system of young adults that, however, largely ignore the variations that occur with age. In this paper, we investigated how visual scene processing changes with age and we propose an age-adapted framework that helps to develop a computational model that can predict saliency across different age groups. Our analysis uncovers how the explorativeness of an observer varies with age, how well saliency maps of an age group agree with fixation points of observers from the same or different age groups, and how age influences the center bias tendency. We analyzed the eye movement behavior of 82 observers belonging to four age groups while they explored visual scenes. Explorative- ness was quantified in terms of the entropy of a saliency map, and area under the curve (AUC) metrics was used to quantify the agreement analysis and the center bias tendency. Analysis results were used to develop age adapted saliency models. Our results suggest that the proposed age-adapted saliency model outperforms existing saliency models in predicting the regions of interest across age groups.

Influence of semantic consistency and perceptual features on visual attention during scene viewing in toddlers.

Conceptual representations of everyday scenes are built in interaction with visual environment and these representations guide our visual attention. Perceptual features and object-scene semantic consistency have been found to attract our attention during scene exploration. The present study examined how visual attention in 24-month-old toddlers is attracted by semantic violations and how perceptual features (i. e. saliency, centre distance, clutter and object size) and linguistic properties (i. e. object label frequency and label length) affect gaze distribution. We compared eye movements of 24-month-old toddlers and adults while exploring everyday scenes which either contained an inconsistent (e.g., soap on a breakfast table) or consistent (e.g., soap in a bathroom) object. Perceptual features such as saliency, centre distance and clutter of the scene affected looking times in the toddler group during the whole viewing time whereas looking times in adults were affected only by centre distance during the early viewing time. Adults looked longer to inconsistent than consistent objects either if the objects had a high or a low saliency. In contrast, toddlers presented semantic consistency effect only when objects were highly salient. Additionally, toddlers with lower vocabulary skills looked longer to inconsistent objects while toddlers with higher vocabulary skills look equally long to both consistent and inconsistent objects. Our results indicate that 24-month-old children use scene context to guide visual attention when exploring the visual environment. However, perceptual features have a stronger influence in eye movement guidance in toddlers than in adults. Our results also indicate that language skills influence cognitive but not perceptual guidance of eye movements during scene perception in toddlers.

Visual Attention Saccadic Models Learn to Emulate Gaze Patterns From Childhood to Adulthood.

How people look at visual information reveals fundamental information about themselves, their interests and their state of mind. While previous visual attention models output static 2D saliency maps, saccadic models aim to predict not only where observers look at but also how they move their eyes to explore the scene. In this paper, we demonstrate that saccadic models are a flexible framework that can be tailored to emulate observer's viewing tendencies. More specifically, we use fixation data from 101 observers split into five age groups (adults, 8-10 y.o., 6-8 y.o., 4-6 y.o., and 2 y.o.) to train our saccadic model for different stages of the development of human visual system. We show that the joint distribution of saccade amplitude and orientation is a visual signature specific to each age group, and can be used to generate age-dependent scan paths. Our age-dependent saccadic model does not only output human-like, age-specific visual scan paths, but also significantly outperforms other state-of-the-art saliency models. We demonstrate that the computational modeling of visual attention, through the use of saccadic model, can be efficiently adapted to emulate the gaze behavior of a specific group of observers.

Eye movement patterns and visual attention during scene viewing in 3- to 12-month-olds.

Recently, two attentional modes have been associated with specific eye movement patterns during scene processing. Ambient mode, characterized by short fixations and long saccades during early scene inspection, is associated with localization of objects. Focal mode, characterized by longer fixations, is associated with more detailed object feature processing during later inspection phase. The aim of the present study was to investigate the development of these attentional modes. More specifically, we examined whether indications of ambient and focal attention modes are similar in infants and adults. Therefore, we measured eye movements in 3- to 12-months-old infants while exploring visual scenes. Our results show that both adults and 12-month-olds had shorter fixation durations within the first 1.5 s of scene viewing compared with later time phases (>2.5 s); indicating that there was a transition from ambient to focal processing during image inspection. In younger infants, fixation durations between two viewing phases did not differ. Our results suggest that at the end of the first year of life, infants have developed an adult-like scene viewing behavior. The evidence for the existence of distinct attentional processing mechanisms during early infancy furthermore underlines the importance of the concept of the two modes.

The maturation of eye movement behavior: scene viewing characteristics in children and adults.

While the close link between eye movements and visual attention has often been demonstrated, recently distinct attentional modes have been associated with specific eye movement patterns. The ambient mode-serving the localization of objects and dominating early scene inspection-is expressed by short fixations and large saccade amplitudes. The focal mode-associated with the identification of object details and dominating later stages of scene exploration-is indicated by longer fixations embedded in short saccades. The relationship between these processing modes and eye movement characteristics has so far only been examined in adults. While studies in children revealed a maturation of oculomotor behavior up to adolescence, developmental aspects of the processing modes are still unknown. Here we explored these mechanisms by comparing eye movements during the inspection of naturalistic scenes. Therefore, gaze behavior from adults and children in four different age groups (2, 4-6, 6-8, 8-10years old) was examined. We found a general effect of age, revealing that with age fixation durations decrease and saccade amplitudes increase. However, in all age groups fixations were shorter and saccades were longer at the beginning of scene inspection but fixations became longer and saccades became shorter over time. While saliency influenced eye guidance in the two youngest groups over the full inspection period, for the older groups this influence was found only at the beginning of scene inspection. The results reveal indications for ambient and focal processing strategies for as early as 2 years of age.

Effect of handedness on the occurrence of semantic N400 priming effect in 18- and 24-month-old children.

It is frequently stated that right-handedness reflects hemispheric dominance for language. Indeed, most right-handers process phonological aspects of language with the left hemisphere (and other aspects with the right hemisphere). However, given the overwhelming majority of right-handers and of individuals showing left-hemisphere language dominance, there is a high probability to be right-handed and at the same time process phonology within the left hemisphere even if there was no causal link between both. One way to understand the link between handedness and language lateralization is to observe how they co-develop. In this study, we investigated to what extent handedness is related to the occurrence of a right-hemisphere lateralized N400 event related potential in a semantic priming task in children. The N400 component in a semantic priming task is more negative for unrelated than for related word pairs. We have shown earlier that N400 effect occurred in 24-month-olds over the right parietal-occipital recording sites, whereas no significant effect was obtained over the left hemisphere sites. In 18-month-olds, this effect was observed only in those children with higher word production ability. Since handedness has also been associated with the vocabulary size at these ages, we investigated the relationship between the N400 and handedness in 18- and 24-months as a function of their vocabulary. The results showed that right-handers had significantly higher vocabulary size and more pronounced N400 effect over the right hemisphere than non-lateralized children, but only in the 18-month-old group. We propose that the emergences of right-handedness and right-distributed N400 effect are not causally related, but that both developmental processes reflect a general tendency to recruit the hemispheres in a lateralized manner. The lack of this relationship at 24 months further suggests that there is no direct causal relation between handedness and language lateralization.

Development of lexical-semantic language system: N400 priming effect for spoken words in 18- and 24-month old children.

Our aim was to investigate whether developing language system, as measured by a priming task for spoken words, is organized by semantic categories. Event-related potentials (ERPs) were recorded during a priming task for spoken words in 18- and 24-month-old monolingual French learning children. Spoken word pairs were either semantically related (e.g., train-bike) or unrelated (e.g., chicken-bike). The results showed that the N400-like priming effect occurred in 24-month-olds over the right parietal-occipital recording sites. In 18-month-olds the effect was observed similarly to 24-month-olds only in those children with higher word production ability. The results suggest that words are categorically organized in the mental lexicon of children at the age of 2 years and even earlier in children with a high vocabulary.

Attention and semantic processing during speech: an fMRI study.

This fMRI study was conducted to investigate whether language semantics is processed even when attention is not explicitly directed to word meanings. In the "unattended" condition, the subjects performed a visual detection task while hearing semantically related and unrelated word pairs. In the "phoneme" condition, the subjects made phoneme judgements between prime and target words, and in the "word" condition, they indicated whether the words in each word pair were semantically related or unrelated. In the word condition, stronger activity was obtained for unrelated than related words in the superior temporal gyrus/sulcus (STG/STS), lingual/fusiform gyri and cuneus, whereas in the phoneme condition no such effect was observed. However, during the unattended condition, stronger activity was found in the right STG. Our results suggest that both semantic judgement of word pairs and their passive hearing activate the same neural networks but this activation is more restricted in the passive hearing.

Eye fixation-related potentials (EFRPs) during object identification.

Eye fixation-related potential (EFRP) measures electrical brain activity in response to eye fixations. The aim of the current study was to investigate whether the EFRPs vary during consecutive eye fixations while subjects were performing an object identification task. Eye fixations evoked P1 and N1 components at the occipital and parietal recording sites. The latency of P1 component increased during consecutive fixations. The amplitude of P1 increased and the amplitude of N1 decreased during consecutive fixations. The results indicate that EFRPs are modulated during consecutive fixations, suggesting that the current technique may provide a useful tool to study temporal dynamics of visual perception and processes underlying object identification.

Semantic processing in comatose patients with intact temporal lobes as reflected by the N400 event-related potential.

The present study aimed at determining whether the N400 effect (an ERP index of semantic processing) for spoken words occurs in comatose patients. The patients, treated in an intensive care unit, scored less than 8 points in the glasgow coma score at the time of the recording. Semantically related and unrelated spoken word pairs were delivered to patients through headphones at a rate of 1/3s. Patients with an intact temporal lobe exhibited differential N400-like responses for semantically related and unrelated word pairs, which suggests that word semantics can be processed even in the comatose state. In contrast, patients with an injured temporal lobe showed no such effect.

N400 during recognition of voice identity and vocal affect.

This study explored whether neural processes underlying recognition of speaker's voice and vocal affect are dissociable by measuring event-related potentials. Individuals were asked to identify a target emotion, or a target (congruent) speaker among distracter (incongruent) emotions or speakers. The incongruent condition elicited more negative N400-like response during both tasks, but the distributions differed. Although the response in speaker task was more pronounced at frontal than posterior recording sites, in emotion task, the opposite was true. Furthermore, the response was more pronounced at the left recording sites for speaker task and more pronounced at the right recording sites for emotion task. The present results suggest that neural substrates involved in processing speaker identity are different from those responsible for processing vocal affect.

Word semantics is processed even without attentional effort.

We examined the attentional modulation of semantic priming and the N400 effect for spoken words. The aim was to find out how the semantics of spoken language is processed when attention is directed to another modality (passive task), to the phonetics of spoken words (phonological task), or to the semantics of spoken words (word task). Equally strong behavioral priming effects were obtained in the phonological and the word tasks. A significant N400 effect was found in all tasks. The effect was stronger in the word and the phonological tasks than in the passive task, but there was no difference in the magnitude of the effect between the phonological and the word tasks. The latency of the N400 effect did not differ between the tasks. Although the N400 effect had a centroparietal maximum in the phonological and the word tasks, it was largest at the parietal recording sites in the passive task. The effect was more pronounced at the left than right recording sites in the phonological task, but there was no laterality effect in the other tasks. The N400 effect in the passive task indicates that semantic priming occurs even when spoken words are not actively attended. However, stronger N400 effect in the phonological and the word tasks than in the passive task suggests that controlled processes modulate the N400 effect. The finding that there were no differences in the N400 effect between the phonological and the word tasks indicates that the semantics of attended spoken words is processed regardless of whether semantic processing is relevant for task performance.

Separate neural processes for retrieval of voice identity and word content in working memory.

Working memory for voice identity and words was studied to investigate whether the neural system underlying extralinguistic and linguistic information processing is dissociated and whether the possible differences in the distribution of activity are related to specific periods of working memory tasks. Separate analyses of task-related activations evoked during the encoding, maintenance, and recognition periods of the memory tasks were performed. During the voice task, the superior temporal, ventral prefrontal and medial frontal cortices were activated in comparison with the control task whereas the word task produced activation in the occipital, parietal, and dorsal prefrontal areas. Direct contrasts between different periods of the tasks indicated that the ventral prefrontal cortex and the right superior temporal sulcus/gyrus were more activated during recognition than encoding and maintenance periods in the voice compared with the word task. In contrast, the right supramarginal gyrus was more active during the recognition than encoding period in the word compared with the voice task. The results suggest that dissociable neural substrates are recruited for processing of linguistic and extralinguistic information during the recognition period of a working memory task.

Domain-dependent activation during spatial and nonspatial auditory working memory.

Visual system has been proposed to be divided into two, the ventral and dorsal, processing streams. The ventral pathway is thought to be involved in object identification whereas the dorsal pathway processes information regarding the spatial locations of objects and the spatial relationships among objects. Several studies on working memory (WM) processing have further suggested that there is a dissociable domain-dependent functional organization within the prefrontal cortex for processing of spatial and nonspatial visual information. Also the auditory system is proposed to be organized into two domain-specific processing streams, similar to that seen in the visual system. Recent studies on auditory WM have further suggested that maintenance of nonspatial and spatial auditory information activates a distributed neural network including temporal, parietal, and frontal regions but the magnitude of activation within these activated areas shows a different functional topography depending on the type of information being maintained. The dorsal prefrontal cortex, specifically an area of the superior frontal sulcus (SFS), has been shown to exhibit greater activity for spatial than for nonspatial auditory tasks. Conversely, ventral frontal regions have been shown to be more recruited by nonspatial than by spatial auditory tasks. It has also been shown that the magnitude of this dissociation is dependent on the cognitive operations required during WM processing. Moreover, there is evidence that within the nonspatial domain in the ventral prefrontal cortex, there is an across-modality dissociation during maintenance of visual and auditory information. Taken together, human neuroimaging results on both visual and auditory sensory systems support the idea that the prefrontal cortex is organized according to the type of information being maintained in WM.

Functional topography of working memory for face or voice identity.

We used functional magnetic resonance imaging (fMRI) to investigate whether the neural systems for nonspatial visual and auditory working memory exhibits a functional dissociation. The subjects performed a delayed recognition task for previously unfamiliar faces and voices and an audiovisual sensorimotor control task. During the initial sample and subsequent test stimulus presentations, activation was greater for the face than for the voice identity task bilaterally in the occipitotemporal cortex and, conversely, greater for voices than for faces bilaterally in the superior temporal sulcus/gyrus (STS/STG). Ventral prefrontal regions were activated by both memory delays in comparison with the control delays, and there was no significant difference in direct voxelwise comparisons between the tasks. However, further analyses showed that there was a subtle difference in the functional topography for two delay types within the ventral prefrontal cortex. Face delays preferentially activate the dorsal part of the ventral prefrontal cortex (BA 44/45) while voice delays preferentially activate the inferior part (BA 45/47), indicating a ventral/dorsal auditory/visual topography within the ventral prefrontal cortex. The results confirm that there is a modality-specific attentional modulation of activity in visual and auditory sensory areas during stimulus presentation. Moreover, within the nonspatial information-type domain, there is a subtle across-modality dissociation within the ventral prefrontal cortex during working memory maintenance of faces and voices.

A potential aphrodisiac for female macaques.

Earlier studies suggest that alpha2-adrenoceptor antagonists and dopamine receptor agonists may enhance sexual activity in human and nonhuman male primates. It is not known whether these compounds influence the sexual behavior of female primates. We determined whether the administration of a selective alpha2-adrenoceptor antagonist (atipamezole), a dopamine receptor agonist (apomorphine), or their combination to female Macaca arctoides (stumptail macaque) monkeys produces changes in sexual behavior of the female with a male. Following the administration of drugs to the female, the behavior of the female with a male stumptail was observed for 30 min. Atipamezole dose dependently (0.03-0.3 mg/kg im) increased short-time mounting behavior of the male and the total number of copulations. Apomorphine alone (0.125-0.25 mg/kg) or in combination with atipamezole had no significant effects on sexual behavior. The result indicates that a selective alpha2-adrenoceptor antagonist administered in the female stumptail increases sexual behavior of the male with the female. A plausible explanation for this finding is that a selective alpha2-adrenoceptor antagonist increases sexual arousal in female stumptails and this, possibly due to a change in psychosocial behavior of the female, triggers increased sexual activity in males.