Biomedical subjects

Anja Hahne

Publications and source records attributed to Anja Hahne.

23 records · Page 2Linked to original sources

PubMed2003

Information flow in the mental lexicon during speech planning: evidence from event-related brain potentials.

A major issue in speech production research is the question of how speakers retrieve words from the so-called mental lexicon. Current models of lexical retrieval converge on the assumption that category associates of a target word are semantically activated during speech planning. However, the question of whether these competitors are also phonologically activated is less agreed on. Past research has addressed this issue by testing whether lexical retrieval of a picture name (e.g. sheep) affects, or is affected by, the processing of a word that is phonologically related to a semantic category associate to the picture name (e.g. goal, phonologically related to goat). Behavioral studies have failed to obtain such so-called mediated priming effects, but have been questioned on the grounds of possibly insufficient task sensitivity. As such priming effects have reliably been obtained with event-related brain potentials in word recognition, we used this approach for testing these effects in lexical retrieval during speech planning. Our results consistently demonstrate the absence of mediated priming effects, putting strong constraints on the activation flow in the mental lexicon during speech planning.

Adult↗

PubMed2003

The role of left inferior frontal and superior temporal cortex in sentence comprehension: localizing syntactic and semantic processes.

An event-related functional magnetic resonance imaging (fMRI) paradigm was used to specify those brain areas supporting the processing of sentence-level semantic and syntactic information. Hemodynamic responses were recorded while participants listened to correct, semantically incorrect and syntactically incorrect sentences. Both anomalous conditions recruited larger portions of the superior temporal region than correct sentences. Processing of semantic violations relied primarily on the mid-portion of the superior temporal region bilaterally and the insular cortex bilaterally, whereas processing of syntactic violations specifically involved the anterior portion of the left superior temporal gyrus, the left posterior frontal operculum adjacent to Broca's area and the putamen in the left basal ganglia. A comparison of the two anomalous conditions revealed higher levels of activation for the syntactic over the semantic condition in the left basal ganglia and for the semantic over the syntactic condition in the mid-portion of the superior temporal gyrus, bilaterally. These data indicate that both semantic and syntactic processes are supported by a temporo-frontal network with distinct areas specialized for semantic and syntactic processes.

Adult↗

PubMed2002

Segregating early physical and syntactic processes in auditory sentence comprehension.

Auditory language comprehension involves physical as well as syntactic processing. The present study examined whether early physical and syntactic processes in spoken sentence comprehension can be segregated using event-related brain potentials (ERPs). In the physical manipulation condition, the terminal word of the sentence was presented either from the same or from a different location to the preceding sentence fragment. In the syntactic manipulation condition, the terminal word was either a syntactically correct continuation of the preceding sentence fragment or violated syntactic constraints. These two factors were completely crossed. Physical deviances elicited the mismatch negativity (MMN) and syntactic deviances the early syntax-related negativity, both deviance-related components of the ERP. Sentences which violated physical as well as syntactic constraints elicited a negativity which was larger than that elicited by only a physical or only a syntactic deviance. The elicitation of the MMN in connected speech demonstrates that this component can be used as a probe for auditory change-detection even in ecologically highly valid situations. The increase of deviance-related effects with double deviants suggests that the early physical and syntactic processing systems act, to a high degree, in parallel and independently of each other.

Adolescent↗

PubMed2002

Differential task effects on semantic and syntactic processes as revealed by ERPs.

Two experiments investigated the time-course of semantic and syntactic processes in auditory language comprehension as well as their possible functional dependencies, using event-related brain potentials (ERPs). Participants listened to sentences which were either correct, semantically incorrect, syntactically incorrect, or both semantically and syntactically incorrect. In experiment 1, participants judged the overall correctness of these sentences. The semantic violation elicited an N400 whereas the syntactic phrase structure violation elicited an early anterior negativity followed by a P600. Sentences in which the critical element violated both semantic and syntactic constraints elicited the same pattern of ERPs as the syntactic violation alone, not evoking an N400. In experiment 2, participants judged the same sentences for semantic coherence, required to ignore syntactic violations. Again, an early anterior negativity was elicited for those sentences containing phrase-structure errors. In contrast to experiment 1, however, combined violations elicited both an early negativity and an N400. Together, the results suggest that the N400 associated with semantic aspects of sentence comprehension reflects controlled processes whereas initial parsing processes associated with the early anterior negativity are independent of semantic constraints and task requirements.

Adult↗

PubMed2002

Distinct neurophysiological patterns reflecting aspects of syntactic complexity and syntactic repair.

Aspects of syntactic complexity and syntactic repair were investigated by comparing the event-related (brain) potentials (ERPs) for sentences of different syntactic complexity to those containing a syntactic violation. Previous research had shown that both aspects of syntactic processing are reflected in a late positivity (P600). Results from the present reading experiment demonstrate, however, that although both processing aspects elicit a late positivity, they are different in distribution. The repair-related positivity preceded by a negativity displayed a centroparietal distribution, whereas the complexity-related positivity showed a frontocentral scalp distribution. These data indicate that the P600 is not a unitary phenomenon. Moreover, the distributional differences strongly suggest that different neural structures underlie the two aspects of processing, namely syntactic repair and syntactic integration difficulties, most evident when processing syntactically complex sentences.

Adult↗