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Brain ERPs to changes of speech segment durations in six-month-olds
Abstracts /International Joumal of Psychophysiology 25 (1997) 17-84
Controversy lingers as to whether Specific Language Impairment (SLI) and dyslexia represent a unitary phenomenon. Although attempts are made to separate these two diagnoses for research and treatment purposes, theories regarding their singularity have been largely supported. Early studies of dyslexic populations via structural MRIs implicated the Sylvian fissure bilaterally. Recent structural MRI studies with SLI children suggest the populations are generally indistinguishable at the structural level. This presentation will focus on the use of neuroimaging techniques, that are functionally (e.g., fMRI) and behaviorally based, as a more viable path for determining potential differences in the neural bases of these disorders. BRAIN ERPs TO CHANGES OF SPEECH SEGMENT DURATIONS IN SIX-MONTH-OLDS P.H.T. Lepplnen* , U. Richardson and H. Lyytinen Department of Psychology, University of Jyvlskyll, P.O. Box 35, FIN-40351 Jyvlskyll, Finland Event-related potentials (ERPs) to variation in duration of speech segments were studied in a sub-sample of 41 six months old infants. Eighteen infants had a familial background of dyslexia and 23 belonged to control families. Two naturally produced /atta/-pseudowords, one with intermediate and one with long duration of the voiceless dental stop, were used as the deviants embedded among the standard short /ata/ in an oddball paradigm. Six of control Ss participated in the control experiment, in which the positions of the long /atta/ and /ata/ were reversed, the long /atta/ being the standard. In both groups the ERPs to both deviant stimuli differed from those to the standards. The late negative deflection of the differences wave (deviant- minus standard-response) to the long /atta/ was smaller at the left hemisphere in the at risk Ss than in the control Ss. The responses to the intermediate and long /atta/s had two distinct negative deflections in both experiments, whereas the response to the short /ata/ had two distinct peaks only when /ata/ was presented as a deviant in the control experiment. The ERPs in this study seem to reflect mainly processing of acoustic features of the stimuli. However, the occurrence of the second negative peak in the ERP to the /ata/-deviant suggests a possibility of adult like mismatch negativity response (MMN), reflecting in adults processing of change in similar conditions. Group differences indicate that infants at risk for develop mental dyslexia show differences in processing of speech segment durations, as reflected in ERPs, already at this early age compared to infants without such risk. TOPOGRAPHIC ANALYSIS OF BRAIN POTENTIALS IN DYSLEXIC AND NORMAL CHILDREN Robert Licht*a, H.L. Hamburger” & L.H.J. Nyens’ ‘Paedological Institute, Duivendrecht; “Municipal Hospital Slotervaart, Amsterdam, the Netherlands
55
The aim of the present study was to examine whether dyslexic children differ from normal readers in distribution of brain activity during semantic processing in general or only when words have to be decoded. For that purpose a word- and a picture semantic decision task were presented, while EventRelated Potentials (ERPs) were recorded from 21 electrode locations (lo-20 system). In the word task target words consisted of animal names, whereas in the picture task targets consisted of colored line drawings of the same animals. Targets were presented on 33% of the trials. The children were required to respond to targets and nontargets by pressing a button. The resulting ERPs were analyzed by performing adaptive segmentation on the potential map field configuration in order to identify periods of stable landscape orientation of the electrical field generated at the 21 electrode locations. This resulted in four landscapes of which the topography and latencies conform to the well known PlOO, N200, P300 and P3b, respectively. Global Field Power (GFP), latency and scalp locations of the positive and negative centroids for each of the potential maps were analyzed. It was found that the topographic distribution of P3b differed significantly between dyslexic and controls in the word task only. In addition, dyslexics had lower GFP than controls in all landscapes and tasks. The findings suggest that words activate differently located or oriented neuronal generators in dyslexic children than in normal readers, whereas pictures do not.
AUTOMATIC AND CONTROLLED PROCESSING OF PHONETIC CONTRAST IN YOUNG SCHOOLCHIL DREN: COMPARISON OF MMN AND CNV
Valtria Cstpe, Judit Osman-Sbgi and Mark Molnlr Inst. for Psych. Hungarian Academy of Sciences, Dept. of Psychophysiology, Budapest, Hungary
By using event-related potentials (ERPs) the age dependence of automatic and controlled processing of phoneme contrast was investigated in young school-children (6-10 years). ERPs were obtained to digitized syllables /ba:/, /pa:/ and /pa:/ in a passive and in an active paradigm. In the passive oddball /ba:/ served as standard and the two other syllables as deviants. The children were watching cartoons in the passive condition. In the active paradigm the subjects had to judge on syllable pairs and pressing a button when the imperative stimulus (S2) differed from the warning stimulus (Sl). The mismatch negativity (MMN to the deviants in the passive condition, the N2-P3 wavecomplex to the S2 and the contingent negative variation (CNV) preceding the S2 were measured and compared. The MMN to deviation in place of articulation was well defined in most of the children investigated. The MMN to voicing differences, however, showed a large variability in the younger (6-7 years) children. Furthermore, in those children whose MMN was absent to voicing, the reaction to S2 failed and a robust P3 to the S2 occurred.
Controversy lingers as to whether Specific Language Impairment (SLI) and dyslexia represent a unitary phenomenon. Although attempts are made to separate these two diagnoses for research and treatment purposes, theories regarding their singularity have been largely supported. Early studies of dyslexic populations via structural MRIs implicated the Sylvian fissure bilaterally. Recent structural MRI studies with SLI children suggest the populations are generally indistinguishable at the structural level. This presentation will focus on the use of neuroimaging techniques, that are functionally (e.g., fMRI) and behaviorally based, as a more viable path for determining potential differences in the neural bases of these disorders. BRAIN ERPs TO CHANGES OF SPEECH SEGMENT DURATIONS IN SIX-MONTH-OLDS P.H.T. Lepplnen* , U. Richardson and H. Lyytinen Department of Psychology, University of Jyvlskyll, P.O. Box 35, FIN-40351 Jyvlskyll, Finland Event-related potentials (ERPs) to variation in duration of speech segments were studied in a sub-sample of 41 six months old infants. Eighteen infants had a familial background of dyslexia and 23 belonged to control families. Two naturally produced /atta/-pseudowords, one with intermediate and one with long duration of the voiceless dental stop, were used as the deviants embedded among the standard short /ata/ in an oddball paradigm. Six of control Ss participated in the control experiment, in which the positions of the long /atta/ and /ata/ were reversed, the long /atta/ being the standard. In both groups the ERPs to both deviant stimuli differed from those to the standards. The late negative deflection of the differences wave (deviant- minus standard-response) to the long /atta/ was smaller at the left hemisphere in the at risk Ss than in the control Ss. The responses to the intermediate and long /atta/s had two distinct negative deflections in both experiments, whereas the response to the short /ata/ had two distinct peaks only when /ata/ was presented as a deviant in the control experiment. The ERPs in this study seem to reflect mainly processing of acoustic features of the stimuli. However, the occurrence of the second negative peak in the ERP to the /ata/-deviant suggests a possibility of adult like mismatch negativity response (MMN), reflecting in adults processing of change in similar conditions. Group differences indicate that infants at risk for develop mental dyslexia show differences in processing of speech segment durations, as reflected in ERPs, already at this early age compared to infants without such risk. TOPOGRAPHIC ANALYSIS OF BRAIN POTENTIALS IN DYSLEXIC AND NORMAL CHILDREN Robert Licht*a, H.L. Hamburger” & L.H.J. Nyens’ ‘Paedological Institute, Duivendrecht; “Municipal Hospital Slotervaart, Amsterdam, the Netherlands
55
The aim of the present study was to examine whether dyslexic children differ from normal readers in distribution of brain activity during semantic processing in general or only when words have to be decoded. For that purpose a word- and a picture semantic decision task were presented, while EventRelated Potentials (ERPs) were recorded from 21 electrode locations (lo-20 system). In the word task target words consisted of animal names, whereas in the picture task targets consisted of colored line drawings of the same animals. Targets were presented on 33% of the trials. The children were required to respond to targets and nontargets by pressing a button. The resulting ERPs were analyzed by performing adaptive segmentation on the potential map field configuration in order to identify periods of stable landscape orientation of the electrical field generated at the 21 electrode locations. This resulted in four landscapes of which the topography and latencies conform to the well known PlOO, N200, P300 and P3b, respectively. Global Field Power (GFP), latency and scalp locations of the positive and negative centroids for each of the potential maps were analyzed. It was found that the topographic distribution of P3b differed significantly between dyslexic and controls in the word task only. In addition, dyslexics had lower GFP than controls in all landscapes and tasks. The findings suggest that words activate differently located or oriented neuronal generators in dyslexic children than in normal readers, whereas pictures do not.
AUTOMATIC AND CONTROLLED PROCESSING OF PHONETIC CONTRAST IN YOUNG SCHOOLCHIL DREN: COMPARISON OF MMN AND CNV
Valtria Cstpe, Judit Osman-Sbgi and Mark Molnlr Inst. for Psych. Hungarian Academy of Sciences, Dept. of Psychophysiology, Budapest, Hungary
By using event-related potentials (ERPs) the age dependence of automatic and controlled processing of phoneme contrast was investigated in young school-children (6-10 years). ERPs were obtained to digitized syllables /ba:/, /pa:/ and /pa:/ in a passive and in an active paradigm. In the passive oddball /ba:/ served as standard and the two other syllables as deviants. The children were watching cartoons in the passive condition. In the active paradigm the subjects had to judge on syllable pairs and pressing a button when the imperative stimulus (S2) differed from the warning stimulus (Sl). The mismatch negativity (MMN to the deviants in the passive condition, the N2-P3 wavecomplex to the S2 and the contingent negative variation (CNV) preceding the S2 were measured and compared. The MMN to deviation in place of articulation was well defined in most of the children investigated. The MMN to voicing differences, however, showed a large variability in the younger (6-7 years) children. Furthermore, in those children whose MMN was absent to voicing, the reaction to S2 failed and a robust P3 to the S2 occurred.