How do children with developmental language disorder extend novel nouns?

In this study, we investigated the ability of children with developmental language disorder (DLD) to extend nouns referring to different categories of novel objects. In a word extension task, we used several types of object entities (solid, animate, nonsolid, functional, and spatial relations) for which children needed to attend to diverse properties (shape, texture, role, or spatial relation) to decide category membership. We compared 15 school-aged children with DLD with typically developing (TD) children matched on either age or vocabulary. Our results indicate that children with DLD were impaired in extending novel words for nonsolid substances and relational objects, whereas age-matched TD children performed well for all object classes. Similar to children with DLD, TD children matched on language had difficulty in extending spatial relation categories. We also show that children with DLD needed more learning exemplars and relied more on shape-based information than TD children, especially for spatial configuration objects. Overall, our findings suggest that children are able to learn regularities between object properties and category organization and to focus on diverse features according to the object presented when extending novel nouns. They also provide clear evidence linking DLD to deficits in novel name generalization and word learning.

The Role of Low-frequency Neural Oscillations in Speech Processing: Revisiting Delta Entrainment.

Studies that use measures of cerebro-acoustic coherence have shown that theta oscillations (3-10 Hz) entrain to syllable-size modulations in the energy envelope of speech. This entrainment creates sensory windows in processing acoustic cues. Recent reports submit that delta oscillations (<3 Hz) can be entrained by nonsensory content units like phrases and serve to process meaning-though such views face fundamental problems. Other studies suggest that delta underlies a sensory chunking linked to the processing of sequential attributes of speech sounds. This chunking associated with the "focus of attention" is commonly manifested by the temporal grouping of items in sequence recall. Similar grouping in speech may entrain delta. We investigate this view by examining how low-frequency oscillations entrain to three types of stimuli (tones, nonsense syllables, and utterances) having similar timing, pitch, and energy contours. Entrainment was indexed by "intertrial phase coherence" in the EEGs of 18 listeners. The results show that theta oscillations at central sites entrain to syllable-size elements in speech and tones. However, delta oscillations at frontotemporal sites specifically entrain to temporal groups in both meaningful utterances and meaningless syllables, which indicates that delta may support but does not directly bear on a processing of content. The findings overall suggest that, although theta entrainment relates to a processing of acoustic attributes, delta entrainment links to a sensory chunking that relates to a processing of properties of articulated sounds. The results also show that measures of intertrial phase coherence can be better suited than cerebro-acoustic coherence in revealing delta entrainment.

Analogical reasoning in children with specific language impairment: Evidence from a scene analogy task.

Analogical reasoning is a human ability that maps systems of relations. It develops along with relational knowledge, working memory and executive functions such as inhibition. It also maintains a mutual influence on language development. Some authors have taken a greater interest in the analogical reasoning ability of children with language disorders, specifically those with specific language impairment (SLI). These children apparently have weaker analogical reasoning abilities than their aged-matched peers without language disorders. Following cognitive theories of language acquisition, this deficit could be one of the causes of language disorders in SLI, especially those concerning productivity. To confirm this deficit and its link to language disorders, we use a scene analogy task to evaluate the analogical performance of SLI children and compare them to controls of the same age and linguistic abilities. Results show that children with SLI perform worse than age-matched peers, but similar to language-matched peers. They are more influenced by increased task difficulty. The association between language disorders and analogical reasoning in SLI can be confirmed. The hypothesis of limited processing capacity in SLI is also being considered.

The processing of intimately familiar and unfamiliar voices: Specific neural responses of speaker recognition and identification.

Research has repeatedly shown that familiar and unfamiliar voices elicit different neural responses. But it has also been suggested that different neural correlates associate with the feeling of having heard a voice and knowing who the voice represents. The terminology used to designate these varying responses remains vague, creating a degree of confusion in the literature. Additionally, terms serving to designate tasks of voice discrimination, voice recognition, and speaker identification are often inconsistent creating further ambiguities. The present study used event-related potentials (ERPs) to clarify the difference between responses to 1) unknown voices, 2) trained-to-familiar voices as speech stimuli are repeatedly presented, and 3) intimately familiar voices. In an experiment, 13 participants listened to repeated utterances recorded from 12 speakers. Only one of the 12 voices was intimately familiar to a participant, whereas the remaining 11 voices were unfamiliar. The frequency of presentation of these 11 unfamiliar voices varied with only one being frequently presented (the trained-to-familiar voice). ERP analyses revealed different responses for intimately familiar and unfamiliar voices in two distinct time windows (P2 between 200-250 ms and a late positive component, LPC, between 450-850 ms post-onset) with late responses occurring only for intimately familiar voices. The LPC present sustained shifts, and short-time ERP components appear to reflect an early recognition stage. The trained voice equally elicited distinct responses, compared to rarely heard voices, but these occurred in a third time window (N250 between 300-350 ms post-onset). Overall, the timing of responses suggests that the processing of intimately familiar voices operates in two distinct steps of voice recognition, marked by a P2 on right centro-frontal sites, and speaker identification marked by an LPC component. The recognition of frequently heard voices entails an independent recognition process marked by a differential N250. Based on the present results and previous observations, it is proposed that there is a need to distinguish between processes of voice "recognition" and "identification". The present study also specifies test conditions serving to reveal this distinction in neural responses, one of which bears on the length of speech stimuli given the late responses associated with voice identification.

Characterizing the spatio-temporal dynamics of the neural events occurring prior to and up to overt recognition of famous faces.

Although it is generally acknowledged that familiar face recognition is fast, mandatory, and proceeds outside conscious control, it is still unclear whether processes leading to familiar face recognition occur in a linear (i.e., gradual) or a nonlinear (i.e., all-or-none) manner. To test these two alternative accounts, we recorded scalp ERPs while participants indicated whether they recognize as familiar the faces of famous and unfamiliar persons gradually revealed in a descending sequence of frames, from the noisier to the least noisy. This presentation procedure allowed us to characterize the changes in scalp ERP responses occurring prior to and up to overt recognition. Our main finding is that gradual and all-or-none processes are possibly involved during overt recognition of familiar faces. Although the N170 and the N250 face-sensitive responses displayed an abrupt activity change at the moment of overt recognition of famous faces, later ERPs encompassing the N400 and late positive component exhibited an incremental increase in amplitude as the point of recognition approached. In addition, famous faces that were not overtly recognized at one trial before recognition elicited larger ERP potentials than unfamiliar faces, probably reflecting a covert recognition process. Overall, these findings present evidence that recognition of familiar faces implicates spatio-temporally complex neural processes exhibiting differential pattern activity changes as a function of recognition state.

VEP contrast sensitivity responses reveal reduced functional segregation of mid and high filters of visual channels in autism.

Despite the vast amount of behavioral data showing a pronounced tendency in individuals with autism spectrum disorder (ASD) to process fine visual details, much less is known about the neurophysiological characteristics of spatial vision in ASD. Here, we address this issue by assessing the contrast sensitivity response properties of the early visual-evoked potentials (VEPs) to sine-wave gratings of low, medium and high spatial frequencies in adults with ASD and in an age- and IQ-matched control group. Our results show that while VEP contrast responses to low and high spatial frequency gratings did not differ between ASD and controls, early VEPs to mid spatial frequency gratings exhibited similar response characteristics as those to high spatial frequency gratings in ASD. Our findings show evidence for an altered functional segregation of early visual channels, especially those responsible for processing mid- and high-frequency spatial scales.

From upright to upside-down presentation: a spatio-temporal ERP study of the parametric effect of rotation on face and house processing.

BACKGROUND: While there is a general agreement that picture-plane inversion is more detrimental to face processing than to other seemingly complex visual objects, the origin of this effect is still largely debatable. Here, we address the question of whether face inversion reflects a quantitative or a qualitative change in processing mode by investigating the pattern of event-related potential (ERP) response changes with picture plane rotation of face and house pictures. Thorough analyses of topographical (Scalp Current Density maps, SCD) and dipole source modeling were also conducted. RESULTS: We find that whilst stimulus orientation affected in a similar fashion participants' response latencies to make face and house decisions, only the ERPs in the N170 latency range were modulated by picture plane rotation of faces. The pattern of N170 amplitude and latency enhancement to misrotated faces displayed a curvilinear shape with an almost linear increase for rotations from 0 degrees to 90 degrees and a dip at 112.5 degrees up to 180 degrees rotations. A similar discontinuity function was also described for SCD occipito-temporal and temporal current foci with no topographic distribution changes, suggesting that upright and misrotated faces activated similar brain sources. This was confirmed by dipole source analyses showing the involvement of bilateral sources in the fusiform and middle occipital gyri, the activity of which was differentially affected by face rotation. CONCLUSION: Our N170 findings provide support for both the quantitative and qualitative accounts for face rotation effects. Although the qualitative explanation predicted the curvilinear shape of N170 modulations by face misrotations, topographical and source modeling findings suggest that the same brain regions, and thus the same mechanisms, are probably at work when processing upright and rotated faces. Taken collectively, our results indicate that the same processing mechanisms may be involved across the whole range of face orientations, but would operate in a non-linear fashion. Finally, the response tuning of the N170 to rotated faces extends previous reports and further demonstrates that face inversion affects perceptual analyses of faces, which is reflected within the time range of the N170 component.

Impaired face processing in autism: fact or artifact?

Within the last 10 years, there has been an upsurge of interest in face processing abilities in autism which has generated a proliferation of new empirical demonstrations employing a variety of measuring techniques. Observably atypical social behaviors early in the development of children with autism have led to the contention that autism is a condition where the processing of social information, particularly faces, is impaired. While several empirical sources of evidence lend support to this hypothesis, others suggest that there are conditions under which autistic individuals do not differ from typically developing persons. The present paper reviews this bulk of empirical evidence, and concludes that the versatility and abilities of face processing in persons with autism have been underestimated.

Can spectro-temporal complexity explain the autistic pattern of performance on auditory tasks?

To test the hypothesis that level of neural complexity explain the relative level of performance and brain activity in autistic individuals, available behavioural, ERP and imaging findings related to the perception of increasingly complex auditory material under various processing tasks in autism were reviewed. Tasks involving simple material (pure tones) and/or low-level operations (detection, labelling, chord disembedding, detection of pitch changes) show a superior level of performance and shorter ERP latencies. In contrast, tasks involving spectrally- and temporally-dynamic material and/or complex operations (evaluation, attention) are poorly performed by autistics, or generate inferior ERP activity or brain activation. Neural complexity required to perform auditory tasks may therefore explain pattern of performance and activation of autistic individuals during auditory tasks.

Verbal memory and verbal fluency tasks used for language localization and lateralization during magnetoencephalography.

OBJECTIVE: The aim of this study was to develop a presurgical magnetoencephalography (MEG) protocol to localize and lateralize expressive and receptive language function as well as verbal memory in patients with epilepsy. Two simple language tasks and a different analytical procedure were developed. METHODS: Ten healthy participants and 13 epileptic patients completed two language tasks during MEG recording: a verbal memory task and a verbal fluency task. As a first step, principal component analyses (PCA) were performed on source data from the group of healthy participants to identify spatiotemporal factors that were relevant to these paradigms. Averaged source data were used to localize areas activated during each task and a laterality index (LI) was computed on an individual basis for both groups, healthy participants and patients, using sensor data. RESULTS: PCA revealed activation in the left temporal lobe (300 ms) during the verbal memory task, and from the frontal lobe (210 ms) to the temporal lobe (500 ms) during the verbal fluency task in healthy participants. Averaged source data showed activity in the left hemisphere (250-750 ms), in Wernicke's area, for all participants. Left hemisphere dominance was demonstrated better using the verbal memory task than the verbal fluency task (F1,19=4.41, p=0.049). Cohen's kappa statistic revealed 93% agreement (k=0.67, p=0.002) between LIs obtained from MEG sensor data and fMRI, the IAT, electrical cortical stimulation or handedness with the verbal memory task for all participants. At 74%, agreement results for the verbal fluency task did not reach statistical significance. SIGNIFICANCE: Analysis procedures yielded interesting findings with both tasks and localized language-related activation. However, based on source localization and laterality indices, the verbal memory task yielded better results in the context of the presurgical evaluation of epileptic patients. The verbal fluency task did not add any further information to the verbal memory task as regards language localization and lateralization for most patients and healthy participants that would facilitate decision making prior to surgery.

Exploring the functional architecture of person recognition system with event-related potentials in a within- and cross-domain self-priming of faces.

In this paper, we explored the functional properties of person recognition system by investigating the onset, magnitude, and scalp distribution of within- and cross-domain self-priming effects on event-related potentials (ERPs). Recognition of degraded pictures of famous people was enhanced by a prior exposure to the same person's face (within-domain self-priming) or name (cross-domain self-priming) as compared to those preceded by neutral or unrelated primes. The ERP results showed first that the amplitude of the N170 component to famous face targets was modulated by within- and cross-domain self-priming, suggesting not only that the N170 component can be affected by top-down influences but also that this top-down effect crosses domains. Second, similar to our behavioral data, later ERPs to famous faces showed larger ERP self-priming effects in the within-domain than in the cross-domain condition. In addition, the present data dissociated between two topographically and temporally overlapping priming-sensitive ERP components: the first one, with a strongly posterior distribution arising at an early onset, was modulated more by within-domain priming irrespective whether the repeated face was familiar or not. The second component, with a relatively uniform scalp distribution, was modulated by within- and cross-domain priming of familiar faces. Moreover, there was no evidence for ERP-induced modulations for unfamiliar face targets in the cross-domain condition. Together, our findings suggest that multiple neurocognitive events that are possibly mediated by distinct brain loci contribute to face priming effects.

Electrophysiological correlates of facial decision: insights from upright and upside-down Mooney-face perception.

We investigated the ERP correlates of the subjective perception of upright and upside-down ambiguous pictures as faces using two-tone Mooney stimuli in an explicit facial decision task (deciding whether a face is perceived or not in the display). The difficulty in perceiving upside-down Mooneys as faces was reflected by both lower rates of "Face" responses and delayed "Face" reaction times for upside-down relative to upright stimuli. The N170 was larger for the stimuli reported as "faces". It was also larger for the upright than the upside-down stimuli only when they were reported as faces. Furthermore, facial decision as well as stimulus orientation effects spread from 140-190 ms to 390-440 ms. The behavioural delay in 'Face' responses to upside-down stimuli was reflected in ERPs by later effect of facial decision for upside-down relative to upright Mooneys over occipito-temporal electrodes. Moreover, an orientation effect was observed only for the stimuli reported as faces; it yielded a marked hemispheric asymmetry, lasting from 140-190 ms to 390-440 ms post-stimulus onset in the left hemisphere and from 340-390 to 390-440 ms only in the right hemisphere. Taken together, the results supported a preferential involvement of the right hemisphere in the detection of faces, whatever their orientation. By contrast, the early orientation effect in the left hemisphere suggested that upside-down Mooney stimuli were processed as non face objects until facial decision was reached in this hemisphere. The present data show that face perception involves not only spatially but also temporally distributed activities in occipito-temporal regions.

The perceptual chunking of speech: a demonstration using ERPs.

In tasks involving the learning of verbal or non-verbal sequences, groupings are spontaneously produced. These groupings are generally marked by a lengthening of final elements and have been attributed to a domain-general perceptual chunking linked to working memory. Yet, no study has shown how this domain-general chunking applies to speech processing, partly because of the traditional view that chunking involves a conceptual recoding of meaningful verbal items like words (Miller, 1956). The present study provides a demonstration of the perceptual chunking of speech by way of two experiments using evoked Positive Shifts (PSs), which capture on-line neural responses to marks of various groups. We observed listeners׳ response to utterances (Experiment 1) and meaningless series of syllables (Experiment 2) containing changing intonation and temporal marks, while also examining how these marks affect the recognition of heard items. The results show that, across conditions - and irrespective of the presence of meaningful items - PSs are specifically evoked by groups marked by lengthening. Moreover, this on-line detection of marks corresponds to characteristic grouping effects on listeners' immediate recognition of heard items, which suggests chunking effects linked to working memory. These findings bear out a perceptual chunking of speech input in terms of groups marked by lengthening, which constitute the defining marks of a domain-general chunking.

REM sleep and emotional face memory in typically-developing children and children with autism.

Relationship between REM sleep and memory was assessed in 13 neurotypical and 13 children with Autistic Spectrum Disorder (ASD). A neutral/positive/negative face recognition task was administered the evening before (learning and immediate recognition) and the morning after (delayed recognition) sleep. The number of rapid eye movements (REMs), beta and theta EEG activity over the visual areas were measured during REM sleep. Compared to neurotypical children, children with ASD showed more theta activity and longer reaction time (RT) for correct responses in delayed recognition of neutral faces. Both groups showed a positive correlation between sleep and performance but different patterns emerged: in neurotypical children, accuracy for recalling neutral faces and overall RT improvement overnight was correlated with EEG activity and REMs; in children with ASD, overnight RT improvement for positive and negative faces correlated with theta and beta activity, respectively. These results suggest that neurotypical and children with ASD use different sleep-related brain networks to process faces.

Electrophysiological evidence for differential processing of numerical quantity and order in humans.

It is yet unclear whether the processing of number magnitude and order rely on common or different functional processes and neural substrates. On the one hand, recent neuroimaging studies show that quantity and order coding activate the same areas in the parietal and prefrontal cortices. On the other hand, evidence from developmental and neuropsychological studies suggest dissociated mechanisms for processing quantity and order information. To clarify this issue, the present study investigated the spatio-temporal course of quantity and order coding operations using event-related potentials (ERPs). Twenty-four subjects performed a quantity task (classifying numbers as smaller or larger than 15) and an order task on the same material (classifying numbers as coming before or after 15), as well as a control order task on letters (classifying letters as coming before or after M). Behavioral results showed a classical distance effect (decreasing reaction times [RTs] with increasing distance from the standard) for all tasks. In agreement with previous electrophysiological evidence, this effect was significant on a P2 parietal component for numerical material. However, the difference between processing numbers close or far from the target appeared earlier and was larger on the left hemisphere for quantity processing, while it was delayed and bilateral for order processing. There was also a significant distance effect in all tasks on parietal sites for the following P3 component elicited by numbers, but this effect was larger on prefrontal areas for the order judgment. In conclusion, both quantity and order show similar behavioral effects, but they are associated with different spatio-temporal courses in parietal and prefrontal cortices.

Is the N170 for faces cognitively penetrable? Evidence from repetition priming of Mooney faces of familiar and unfamiliar persons.

Impoverished images of faces, two-tone Mooney faces, severely impair the ability to recognize to whom the face pertains. However, previously seeing the corresponding face in a clear format helps fame-judgments to Mooney faces. In the present experiment, we sought to demonstrate that enhancement in the perceptual encoding of Mooney faces results from top-down effects, due to previous activation of familiar face representation. Event-related potentials (ERPs) were obtained for target Mooney images of familiar and unfamiliar faces preceded by clear pictures portraying either the same photo (same photo prime), or a different photo of the same person (different photo prime) or a new unfamiliar face (no-prime). In agreement with previous findings the use of primes was effective in enhancing the recognition of familiar faces in Mooney images; this priming effect was larger in the same than in different photo priming condition. ERP data revealed that the amplitude of the N170 face-sensitive component was smaller when elicited by familiar than by unfamiliar face targets, and for familiar face targets primed by the same than by different photos (a graded priming effect). Because the priming effect was restricted to familiar faces and occurred at the peak of the N170, we suggest that the early perceptual stage of face processing is likely to be penetrable by the top-down effect due to the activation of face representations within the face recognition system.

Differential involvement of episodic and face representations in ERP repetition effects.

The purpose of this study was to disentangle the contribution of episodic-perceptual from pre-existing memory representations of faces to repetition effects. ERPs were recorded to first and second presentations of same and different photos of famous and unfamiliar faces, in an incidental task where occasional non-targets had to be detected. Repetition of same and different photos of famous faces resulted in an N400 amplitude decrement. No such N400 repetition-induced attenuation was observed for unfamiliar faces. In addition, repetition of same photos of faces, and not different ones, gave rise to an early ERP repetition effect (starting at approximately 350 ms) with an occipito-temporal scalp distribution. Together, these results suggest that repetition effects depend on two temporally and may be neuro-functionally distinct loci, episode-based representation and face recognition units stored in long-term memory.

Stepwise emergence of the face-sensitive N170 event-related potential component.

The present study used a parametric design to characterize early event-related potentials (ERP) to face stimuli embedded in gradually decreasing random noise levels. For both N170 and the vertex positive potential (VPP) there was a linear increase in amplitude and decrease in latency with decreasing levels of noise. In contrast, the earlier visual P1 component was stable across noise levels. The P1/N170 dissociation suggests not only a functional dissociation between low and high-level visual processing of faces but also that the N170 reflects the integration of sensorial information into a unitary representation. In addition, the N170/VPP association supports the view that they reflect the same processes operating when viewing faces.

Perceptual chunking and its effect on memory in speech processing: ERP and behavioral evidence.

We examined how perceptual chunks of varying size in utterances can influence immediate memory of heard items (monosyllabic words). Using behavioral measures and event-related potentials (N400) we evaluated the quality of the memory trace for targets taken from perceived temporal groups (TGs) of three and four items. Variations in the amplitude of the N400 showed a better memory trace for items presented in TGs of three compared to those in groups of four. Analyses of behavioral responses along with P300 components also revealed effects of chunk position in the utterance. This is the first study to measure the online effects of perceptual chunks on the memory trace of spoken items. Taken together, the N400 and P300 responses demonstrate that the perceptual chunking of speech facilitates information buffering and a processing on a chunk-by-chunk basis.

Face-specific impairment in holistic perception following focal lesion of the right anterior temporal lobe.

Recent studies have provided solid evidence for pure cases of prosopagnosia following brain damage. The patients reported so far have posterior lesions encompassing either or both the right inferior occipital cortex and fusiform gyrus, and exhibit a critical impairment in generating a sufficiently detailed holistic percept to individualize faces. Here, we extended these observations to include the prosopagnosic patient LR (Bukach, Bub, Gauthier, & Tarr, 2006), whose damage is restricted to the anterior region of the right temporal lobe. First, we report that LR is able to discriminate parametrically defined individual exemplars of nonface object categories as accurately and quickly as typical observers, which suggests that the visual similarity account of prosopagnosia does not explain his impairments. Then, we show that LR does not present with the typical face inversion effect, whole-part advantage, or composite face effect and, therefore, has impaired holistic perception of individual faces. Moreover, the patient is more impaired at matching faces when the facial part he fixates is masked than when it is selectively revealed by means of gaze contingency. Altogether these observations support the view that the nature of the critical face impairment does not differ qualitatively across patients with acquired prosopagnosia, regardless of the localization of brain damage: all these patients appear to be impaired to some extent at what constitutes the heart of our visual expertise with faces, namely holistic perception at a sufficiently fine-grained level of resolution to discriminate exemplars of the face class efficiently. This conclusion raises issues regarding the existing criteria for diagnosis/classification of patients as cases of apperceptive or associative prosopagnosia.