Left hemisphere enhancement of auditory activation in language impaired children

Specific language impairment (SLI) is a developmental disorder linked to deficient auditory processing. In this magnetoencephalography (MEG) study we investigated a specific prolonged auditory response (N250m) that has been reported predominantly in children and is associated with level of language skills. We recorded auditory responses evoked by sine-wave tones presented alternately to the right and left ear of 9–10-year-old children with SLI (n = 10) and children with typical language development (n = 10). Source analysis was used to isolate the N250m response in the left and right hemisphere. In children with language impairment left-hemisphere N250m responses were enhanced compared to those of controls, while no group difference was found in the right hemisphere. Consequently, language impaired children lacked the typical right-ward asymmetry that was found in control children. Furthermore, left but not right hemisphere N250m responses correlated positively with performance on a phonological processing task in the SLI group exclusively, possibly signifying a compensatory mechanism for delayed maturation of language processing. These results suggest that enhanced left-hemisphere auditory activation reflects a core neurophysiological manifestation of developmental language disorders, and emphasize the relevance of this developmentally specific activation pattern for competent language development. © 2019, The Author(s).Peer reviewe

Functional significance of auditory cortex activation for cognitive skills in children

Lapsilla ja aikuisilla on huomattavia eroja aivojen kuuloinformaation käsittelyssä. Lasten aivoissa nähdään erityinen pitkäkestoinen aivovaste ~250 ms kuuloärsykkeen esittämisen jälkeen elektroenkefalografialla ja magnetoenkefalografialla (M/EEG) mitattuna. Kuulotiedon käsittelyn kehitys on lisäksi merkittävässä roolissa monien taitojen, kuten lukemisen, kirjoittamisen ja kielen oppimisen kannalta. Kuuloaivokuoren kehitys on viime aikoina yhdistetty myös laajemmin kognitiiviseen kehitykseen, mm. toiminnanohjaukseen ja tarkkaavuuteen. Tämänhetkisen tutkimuskirjallisuus osoittaa, että kuulotiedon käsittely erityisesti vasemmalla kuuloaivokuorella on yhteydessä suoriutumiseen kielellisissä tehtävissä, mutta kehittyvän kuulojärjestelmän merkitys laajemmin on epäselvää. Tämän väitöskirjan tavoitteena on (i) selvittää lasten pitkäkestoisen aivoaktivaation toiminnallinen merkitys ja (ii) tutkia kuulotiedon käsittelyn yhteyttä kognitiiviseen suoriutumiseen kielellisissä, tarkkaavuus- ja inhibitiotehtävissä lapsilla ja aikuisilla. Ensimmäisessä osatutkimuksessa aktivaation lähdemallinnus osoitti voimakkaampia vasteita lapsilla, joilla oli viivästynyt kielen kehitys verrattuna kontrolleihin. Tässä kliinisessä ryhmässä vasemman aivopuoliskon aktivaation voimakkuus oli kuitenkin positiivisesti yhteydessä kognitiiviseen suorituskykyyn fonologisen tiedonkäsittelyn tehtävässä. Toisessa osatutkimuksessa selvitettiin kuuloaktivaation yhteyttä tarkkaavuuteen ja inhibitioon tyypillisesti kehittyvillä lapsilla ja havaittiin, että vaikka tehtävän vaatimukset eivät vaikuttaneet aktivaation voimakkuuteen, voimakkaampi aktivaatio vasemmassa aivopuoliskossa oli yhteydessä parempaan suorituskykyyn inhibitiotehtävässä. Kolmannessa osatutkimuksessa verrattiin lasten ja aikuisten kuuloaktivaatiota ja tutkittiin sen toiminnallista merkitystä reaktioinhibitiolle. Kuuloaktivaation yhteys suoriutumiseen reaktioinhibitio-tehtävässä oli lapsilla ja aikuisilla erilainen. Yhdessä nämä tulokset viittaavat toiminnalliseen eroon aikuisten ja lasten kuulotiedon käsittelyssä; lapsen aivot näyttävät nojaavan voimakkaammin kuuloaivokuoren aktivaatioon, kunnes aikuisikään mennessä on muodostunut automatisoituneempi kuulon prosessointiketju. Tällä kuuloaivokuoren aktivaatiolla näyttää olevan tärkeä rooli kielen ja inhibitorisen kontrollin kehityksen kannalta.Children and adults show marked differences in their neural processing of auditory information. Most notably, children show a robust, prolonged activation pattern at ~250 ms after auditory stimulation, as measured by electro- and magnetoencephalography (M/EEG). Furthermore, auditory processing during development is crucial in enabling essential skills such as reading, writing, and language learning. Recently, this list of skills that rely on the proper development of the auditory cortex has been extended to include more general cognitive skills such as executive functioning and attention. The current literature has related auditory processes in children, especially in the left hemisphere, to performance on language-related tasks, but the extent of the functional significance of a developing auditory system remains elusive. This dissertation aims to (i) provide a comprehensive account of the functional significance of the prolonged activation pattern in children and (ii) examine the associations between auditory activation and performance on language, attention, and inhibition tasks in children and adults. In study I, source analysis of the activation pattern at ~250 ms showed stronger responses in children with delayed language development compared to typical controls. However, in the clinical group, the left hemisphere activation strength correlated positively with performance on a phonological processing task. Study II investigated the association between auditory activation and attention and inhibition tasks in typical developing children and found that, while the activation strength was unaffected by the task demands, stronger left hemisphere activation was associated with a superior performance on certain inhibition tasks. Finally, study III contrasted the auditory activation patterns of children and adults and investigated their functional significance for response inhibition. We found divergent associations between auditory activation and inhibition task performance in children and adults. Together, the results suggest a functional difference in the auditory processing of adults and children: children seem to rely more strongly on auditory cortical activation until more automatized auditory processing is established in adulthood, which seems especially important for competent language development and inhibitory control

Divergent auditory activation in relation to inhibition task performance in children and adults

Adults and children show remarkable differences in cortical auditory activation which, in children, have shown relevance for cognitive performance, specifically inhibitory control. However, it has not been tested whether these differences translate to functional differences in response inhibition between adults and children. We recorded auditory responses of adults and school-aged children (6–14 years) using combined magneto- and electroencephalography (M/EEG) during passive listening conditions and an auditory Go/No-go task. The associations between auditory cortical responses and inhibition performance measures diverge between adults and children; while in children the brain–behavior associations are not significant, or stronger responses are beneficial, adults show negative associations between auditory cortical responses and inhibitory performance. Furthermore, we found differences in brain responses between adults and children; the late (~200 ms post stimulation) adult peak activation shifts from auditory to frontomedial areas. In contrast, children show prolonged obligatory responses in the auditory cortex. Together this likely translates to a functional difference between adults and children in the cortical resources for performance consistency in auditory-based cognitive tasks.peerReviewe

Activity level in left auditory cortex predicts behavioral performance in inhibition tasks in children

Sensory processing during development is important for the emerging cognitive skills underlying goal-directed behavior. Yet, it is not known how auditory processing in children is related to their cognitive functions. Here, we utilized combined magneto- and electroencephalographic (M/EEG) measurements in school-aged children (6-14y) to show that child auditory cortical activity at ∼250 ms after auditory stimulation predicts the performance in inhibition tasks. While unaffected by task demands, the amplitude of the left-hemisphere activation pattern was significantly correlated with the variability of behavioral response time. Since this activation pattern is typically not present in adults, our results suggest divergent brain mechanisms in adults and children for consistent performance in auditory-based cognitive tasks. This difference can be explained as a shift in cortical resources for cognitive control from sensorimotor associations in the auditory cortex of children to top–down regulated control processes involving (pre)frontal and cingulate areas in adults.peerReviewe

How salience enhances inhibitory control : An analysis of electro-cortical mechanisms

Stop-signal tasks (SSTs) combined with human electro-cortical recordings (Event-Related Potentials, ERPs) have revealed mechanisms associated with successful stopping (relative to failed), presumably contributing to inhibitory control. The corresponding ERP signatures have been labeled stop N1 (+/- 100-ms latency), stop N2 (200 ms), and stop P3 (160–250 ms), and argued to reflect more sensory-specific (N1) versus more generic (N2, P3) mechanisms. However, stop N1 and stop N2, as well as latencies of stop-P3, appear to be quite inconsistent across studies. The present work addressed the possible influence of stop-signal salience, expecting high salience to induce clear stop N1s but reduced stop N2s, and short-latency stop P3s. Three SST varieties were combined with high-resolution EEG. An imperative visual (go) stimulus was occasionally followed by a subsequent (stop) stimulus that signalled to withhold the just initiated response. Stop-Signal Reaction Times (SSRTs) decreased linearly from visual-low to visual-high-salience to auditory. Auditory Stop N1 was replicated. A C1-like visual evoked potential (latency < 100 ms) was observed only with high salience, but not robustly associated with successful versus failed stops. Using the successful-failed contrast a visual stop-N1 analogue (112–156 ms post-stop-signal) was identified, as was right-frontal stop N2, but neither was sensitive to salience. Stop P3 had shorter latency for high than for low salience, and the extent of the early high-salience stop P3 correlated inversely with SSRT. These results suggest that salience-enhanced inhibitory control as manifest in SSRTs is associated with generic rather than sensory-specific electrocortical mechanisms.peerReviewe