Biomedical subjects

Maritza Rivera-Gaxiola

Publications and source records attributed to Maritza Rivera-Gaxiola.

6 recordsLinked to original sources

PubMed2005

Neural patterns to speech and vocabulary growth in American infants.

We report infant auditory event-related potentials to native and foreign contrasts. Foreign contrasts are discriminated at 11 months of age, showing significant differences between the standard and deviant over the positive (P150-250), or over the negative (N250-550) part of the waveform. The amplitudes of these deflections have different amplitude scalp distributions. Infants were followed up longitudinally at 18, 22, 25, 27 and 30 months for word production. The infant speech discriminatory P150-250 and N250-550 are different components with different implications for later language development.

Acoustic Stimulation↗

PubMed2005

Brain potentials to native and non-native speech contrasts in 7- and 11-month-old American infants.

Abstract Behavioral data establish a dramatic change in infants' phonetic perception between 6 and 12 months of age. Foreign-language phonetic discrimination significantly declines with increasing age. Using a longitudinal design, we examined the electrophysiological responses of 7- and 11-month-old American infants to native and non-native consonant contrasts. Analyses of the event-related potentials (ERP) of the group data at 7 and at 11 months of age demonstrated that infants' discriminatory ERP responses to the non-native contrast are present at 7 months of age but disappear by 11 months of age, consistent with the behavioral data reported in the literature. However, when the same infants were divided into subgroups based on individual ERP components, we found evidence that the infant brain remains sensitive to the non-native contrast at 11 months of age, showing differences in either the P150-250 or the N250-550 time window, depending upon the subgroup. Moreover, we observed an increase in infants' responsiveness to native language consonant contrasts over time. We describe distinct neural patterns in two groups of infants and suggest that their developmental differences may have an impact on language development.

Acoustic Stimulation↗

PubMed2004

An event-related brain potential study of sentence comprehension in preschoolers: semantic and morphosyntactic processing.

The goal of this study was to investigate the distinctiveness and the relative time course of the event-related brain potentials (ERP) elicited by syntactically and semantically anomalous words within sentences in 36- and 48-month-old children. ERPs were recorded while children listened to semantically anomalous (i.e., My uncle will blow the movie*), syntactically anomalous (i.e., My uncle will watching the movie*) and control sentences (i.e., My uncle will watch the movie). Semantic violations elicited a negative slow wave with different peaks at 400, 600 and 800 ms in both age groups, whereas the morphosyntactic violations elicited two positive shifts: the first starting at 200 ms with a frontal distribution over the scalp and the second starting at 600 ms and peaking around 800 ms with a broad distribution across the scalp in 36-month-olds and anteriorly distributed for 48-month-olds. These results show that preschoolers display different ERP patterns to syntactic and to semantic violations within sentences. It is possible that the ERP effects here reported are analogous to those elicited in adults by the same type of stimuli, although differences in topography are evident.

Acoustic Stimulation↗

PubMed2003

Are poor readers semantically challenged? An event-related brain potential assessment.

This study explores visual event-related potentials components in a group of poor readers (PRs) and control children who carried out figure and word categorization tasks. In both tasks, every child had to categorize between animal and non-animal stimuli in an odd-ball GO-GO paradigm. During the word categorization task, PRs presented longer reaction times, a poorer performance, longer and larger P2 amplitudes, and smaller amplitudes and longer P300 latencies than controls. There were no differences in the N400 component between groups. These results suggest that semantic processing underachievement in PRs may not be a semantic deficit per se, but the late reflection of an early word codification problem, deficient use of attentional resources and lack of target identification during reading.

Analysis of Variance↗

PubMed2003

Speech and non-speech processing in hemispherectomised children: an event-related potential study.

Although hemispherectomy is now used as a radical treatment for intractable seizures in a number of centres, there have been limited electrophysiological studies investigating post-procedure auditory-speech processing and recovery or reorganisation. We therefore recorded auditory event-related potentials (ERPs) evoked by pure tones and syllables employing a 51-channel electrode array concentrated over the functional hemisphere in 17 patients (nine males, mean age 14.2 years) who had undergone hemispherectomy for intractable seizures; eight of the patients had congenital brain damage and nine had sustained their initial insult at an age of 1 year or older. For comparison, recordings were made from 10 controls (five males, mean age 13.5 years). Responses from patients consisted of five small amplitude components restricted to the functional hemisphere whose scalp polarity was opposite to the ERPs observed in control subjects. The topography of the auditory ERPs in the patients was localised to the centro-temporal regions of the functional hemisphere in comparison to the midline distribution observed in control subjects. As in the control subjects, the latencies of the components evoked by tones were shorter than those evoked by syllables in both left and right hemispherectomised children. In addition, further analysis of the N1 and P2 component revealed increased syllable latencies in left hemispherectomised children only. The results of this study suggest that the left hemisphere alone may be more efficient at processing both pure tones and syllables compared to the right or both together.

Acoustic Stimulation↗

PubMed2003

N400 during lexical decision tasks: a current source localization study.

OBJECTIVE: Our primary aim in the present study was to establish the anatomic and psychophysiological correlates of automatic and controlled semantic priming. METHODS: Current sources were calculated on N400 component data from a previous study on lexical decision tasks [Clin Neurophysiol 1999;110:813] using the variable resolution electromagnetic tomography method (VARETA). In this study, two experiments were carried out, one using directly related pairs and the other one using mediated related pairs. Each experiment consisted of 3 tasks that required different levels of contribution from controlled processes. RESULTS: Average source localization images showed the brain structures involved in lexical decision tasks. The automatic component of the N400 effect was related to activation of occipitotemporal and parahippocampal gyri and anterior temporal lobes bilaterally. The expectancy strategy was related to activation of the right posterior temporal and right frontal areas. The postlexical strategy was associated with activation of right frontal, anterior cingulate and bilateral superior parietal areas. CONCLUSIONS: The findings indicated that the current sources of the N400 varied according to the relative contributions of automatic and controlled mechanisms. Moreover, the sources of the N400 effect depended on the type of strategy used.

Adult↗