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Examples of audiovisual stimuli

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Despite extensive behavioral research on complex word recognition, the neural mechanisms involved in the production of inflections in agglutinative languages, such as Finnish, are still poorly understood. Finnish inflected nouns typically involve morphophonological alternations of the stem (i.e. consonant gradation; CG), which is less common in other languages. Behavioral research on recognition of inflected nouns containing consonant gradation has shown that the number of stem allomorphs results in faster recognition times. To our knowledge, no functional magnetic resonance imaging (fMRI) studies have explicitly investigated consonant gradation in word production. In this study, participants performed covert and overt production tasks during event-related fMRI. Our stimuli comprised real word stems of high and medium frequency as well as pseudoword stems. The stems either included consonant gradation or were non-gradating. Our findings showed that the production of inflected forms containing high frequency stems or CG stems (irrespective of frequency and lexicality) yield enhanced activation of the left inferior frontal and middle frontal gyri (LIFG and MFG, respectively). This suggests that CG stems, that is, stems with more than one allomorph, facilitate lexical lookup, and that the activation of multiple stem allomorphs is reflected in increased recruitment of frontal brain regions.

Recent studies utilizing electrophysiological speech envelope reconstruction have sparked renewed interest in the cocktail party effect by showing that auditory neurons entrain to selectively attended speech. Yet, the neural networks of attention to speech in naturalistic audiovisual settings with multiple sound sources remain poorly understood. We collected functional brain imaging data while participants viewed audiovisual video clips of lifelike dialogues with concurrent distracting speech in the background. Dialogues were presented in a full-factorial design, comprising task (listen to the dialogues vs. ignore them), audiovisual quality and semantic predictability. We used univariate analyses in combination with multivariate pattern analysis (MVPA) to study modulations of brain activity related to attentive processing of audiovisual speech. We found attentive speech processing to cause distinct spatiotemporal modulation profiles in distributed cortical areas including sensory and frontal-control networks.Semantic coherence modulated attention-related activation patterns in the earliest stages of auditory cortical processing, suggesting that the auditory cortex is involved in high-level speech processing. Our results corroborate views that emphasize the dynamic nature of attention, with task-specificity and context as cornerstones of the underlying neuro-cognitive mechanisms.

Learning to recognize morphemic boundaries is essential for fluent language use. In languages with rich morphology, the question of morphological learning is particularly relevant. Some neurocognitive models propose that morphologically complex words are parsed and their constituents are stored as separate units in lexical memory. Neural mechanisms underlying the acquisition of such novel morphological units, however, remain largely unexplored. Here, we trained 19 native Finnish-speaking participants with novel derivational suffixes through a word-picture association task. Following this short training session, we used magnetoencephalography to record the participants’ brain responses to trained and untrained suffixes combined with new real and pseudoword stems in a 22-minute passive listening task. Existing Finnish suffixes served as controls. We compared the responses measured early and late (first/last 5 minutes) during passive exposure to investigate the online build-up of novel suffix representations. In the left frontal and temporal cortices, source activation for real suffixes was significantly higher than for both trained and untrained novel suffixes in the 60-80 ms, 120-140 ms and 220-260 ms time-windows (around ERF peaks) following the suffix onset, suggesting the activation of pre-existing long-term memory traces. However, we also found increased source amplitudes for the trained as opposed to the untrained suffixes already early in exposure. Although such a brief exposure may not be sufficient for the integration of novel morphological units into lexical memory, our findings suggest that a short semantic training of novel affixes facilitates morphological decomposition and speeds up suffix memory trace formation in the left fronto-temporal language networks.

Referencias: p. 38-44. Abstract: There is considerable behavioral evidence that morphologically complex words such as ‘tax-able’ and ‘kiss-es’ are processed and represented combinatorially. In other words, they are decomposed into their constituents ‘tax’ and ‘-able’ during comprehension (reading or listening), and producing them might also involve on–the–spot combination of these constituents (especially for inflections). However, despite increasing amount of neurocognitive research, the neural mechanisms underlying these processes are still not fully understood. The purpose of this critical review is to offer a comprehensive overview on the state-of-the-art of the research on the neural mechanisms of morphological processing. In order to take into account all types of complex words, we include findings on inflected, derived, and compound words presented both visually and aurally. More specifically, we cover a wide range of electro- and magnetoencephalography (EEG and MEG, respectively) as well as structural/functional magnetic resonance imaging (s/fMRI) studies that focus on morphological processing. We present the findings with respect to the temporal course and localization of morphologically complex word processing. We summarize the observed findings, their interpretations with respect to current psycholinguistic models, and discuss methodological approaches as well as their possible limitations. Sitio web de la revista (Consulta: 07-10-2019)

Over the past decades, research into bilingualism has demonstrated that learning and speaking a second language influences the neuroanatomy of the brain. What has remained relatively overlooked so far in the literature is that experience-dependent structural modulation does not occur in isolation, but rather reflect an interaction between person's life experiences and current developmental state of the brain. Thus, the present thesis addressed the nature of bilingualism-induced experience-dependent brain changes as a function of age of second language acquisition. To this end, structural grey and white matter properties as well as anatomo-functional cortical organisation of language were assessed in early and late bilinguals using advanced brain imaging methods. In early bilinguals, increased cortical surface area, higher fractional anisotropy, and language-specific neural populations were observed within the left fronto-temporal language network previously associated with phonological processing. Moreover, the early bilinguals were also found to exhibit increased cortical surface area and enhanced structural connectivity of the right temporal area housing the auditory cortex. Given that early bilingual experiences coincide with the developmental phase during which the brain has been found to be maximally sensitive to phonological and prosodic inputs aiding native language development (i.e. establishing and locking such phonological and prosodic representations is a precondition to later native language development), early auditory inputs appear as a key element driving the experience-dependent brain changes associated with early bilingualism. In late bilinguals, increased structural connectivity was observed bilaterally over the frontal parts of the ventral language processing trajectory previously linked with semantic language processing. This finding was taken to suggest that the developing brain accommodates bilingualism-related increased semantic processing demands differently from the more mature brain: whereas later second language acquisition appears to induce structural growth to adapt the pre-existing semantic network to support the second language, the developing brain establishes an effective bilingual semantic processing network by promoting accelerated structural maturation along the fibre tracts carrying semantic language information. Taken together, the results show that the age of second language acquisition is an important factor in determining how the two languages are built into the bilingual brain. Kaksikielisyyden aivotutkimus viimeisen vuosikymmenen ajalta on osoittanut, että toisen kielen oppiminen ja puhuminen vaikuttavat aivojen neuroanatomiseen perustaan. Kaksikielisyyteen liitettyjä rakenteellisia muutoksia ei kuitenkaan toistaiseksi ole juurikaan tutkittu aivojen kehityksellisestä näkökulmasta ja epäselvää on, miten aivojen kulloinenkin kehitysvaihe vaikuttaa kaksikielisyyden kokemuksesta riippuvaisten aivojen rakenteellisten muutosten ilmiasuun. Tässä väitöskirjassa tarkasteltiin täten toisen kielen oppimisiän merkitystä kaksikielisyyden synnyttämien aivojen rakenteellisten muutosten taustalla. Aivojen harmaan ja valkean aineen rakenteellisia ominaisuuksia sekä kielen käsittelyn toiminnallista järjestäytymistä aivokuorella tarkasteltiin varhaisilla ja myöhäisillä kaksikielisillä tarkkoja aivokuvantamismenetelmiä hyödyntäen. Varhaisilla kaksikielisillä havaittiin suurentunut aivokuoren pinta-ala ja myöhäisiä kaksikielisiä suurempi valkean aineen fraktionaalinen anisotropia sekä kielikohtaisia hermojoukkoja kielen fonologisten piirteiden käsittelyyn osallistuvilla aivojen vasemman puolen otsa- ja ohimolohkojen alueilla ja näitä yhdistävissä valkean aineen radoissa. Lisäksi varhaiseen kaksikielisyyteen havaittiin liittyvän kuuloaistimusten käsittelyyn osallistuvan oikean aivopuoliskon ohimolohkon suurentunut pinta-ala ja vastaavan alueen suurempi rakenteellinen konnektiivisuus. Koska varhaiset kaksikieliset kokemukset osuvat samaan aikaan aivojen fonologisten ja prosodisten käsittelyalueiden kehityksen herkkyyskauden kanssa (ts. pysyvien kielen fonologisten ja prosodisten edustumien rakentuminen on edellytys kielen myöhemmälle kehitykselle), varhaiset kaksikieliset kuuloaistimukset näyttäisivät olevan keskeinen tekijä kaksikielisyyden hermoperustan muovautumiselle. Myöhäisillä kaksikielisillä puolestaan havaittiin molempien aivopuoliskoiden etuosien rakenteellisen konnektiivisuuden kasvua kielen semanttisen tiedon käsittelyyn osallistuvaa hermoverkkoa yhdistävässä valkean aineen radastossa. Tämän havainnon tulkittiin viittaavan keskeneräisten ja jo pidemmälle kehittyneiden aivojen erilaiseen tapaan vastata kaksikielisyyteen liittyviin semanttisen käsittelyn lisääntyneisiin vaatimuksiin: siinä missä myöhäinen kaksikielisyys vaikuttaisi aiheuttavan aivojen olemassa olevien semanttiseen prosessointiin osallistuvien hermoverkkojen rakenteellista tehostamista, varhainen kaksikielisyys näyttäisi nopeuttavan semanttisen tiedon käsittelyyn osallistuvan valkean aineen radaston rakenteellista kypsymistä mahdollistaakseen hermoverkoston osallistumisen kahden kielen prosessointiin. Kaiken kaikkiaan tulokset osoittavat, että toisen kielen oppimisen ikä on tärkeä tekijä määritettäessä, kuinka kaksi kieltä rakentuvat kaksikielisiin aivoihin.