Biomedical subjects

Markus Conrad

Publications and source records attributed to Markus Conrad.

6 recordsLinked to original sources

PubMed2006

Modulation of prefrontal cortex activation by emotional words in recognition memory.

We employed event-related functional magnetic resonance imaging to examine emotional valence effects on verbal recognition memory. Using a yes/no recognition task, we focussed on prefrontal cortex responses to positive, negative and neutral words. Behavioral data confirmed enhanced processing of emotional items and functional magnetic resonance imaging revealed different subregions in the prefrontal cortex supporting retrieval of emotional words. Activations in the right mid-ventrolateral prefrontal cortex correlated with the correct retrieval conditions for negative words, whereas the right ventromedial and orbitofrontal prefrontal cortex showed enhanced responses to positive words. Additionally, differences between old and new items mainly affected bilateral orbitofrontal regions when processing positive words. The results are discussed in terms of higher monitoring demands owing to familiarity-based recognition bias for emotional words.

Adult↗

PubMed2006

Associated or dissociated effects of syllable frequency in lexical decision and naming.

Most empirical work investigating the role of syllable frequency in visual word recognition has focused on the Spanish language, in which syllable frequency seems to produce a classic dissociation: inhibition in lexical decision tasks but facilitation in naming. In the present study, two experiments were run in German, using identical stimulus materials, in a lexical decision task and a naming task. In both tasks, there was an inhibitory effect for words with a high-frequency first syllable. This pattern of results, suggesting a stronger weight of lexical access in the naming process in German than in Spanish, is discussed with regard to the issue of stress assignment in the two languages and within the framework of word production models. Items, mean response latencies, and accuracy rates per item for both experiments can be downloaded from www.psychonomic.org/archive.

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PubMed2005

Incidental effects of emotional valence in single word processing: an fMRI study.

The present study aimed at identifying the neural responses associated with the incidental processing of the emotional valence of single words using event-related functional magnetic resonance imaging (fMRI). Twenty right-handed participants performed a visual lexical decision task, discriminating between nouns and orthographically and phonologically legal nonwords. Positive, neutral and negative word categories were matched for frequency, number and frequency of orthographic neighbors, number of letters and imageability. Response times and accuracy data differed significantly between positive and neutral, and positive and negative words respectively, thus, replicating the findings of a pilot study. Words showed distributed, mainly left hemisphere activations, indicating involvement of a neural network responsible for semantic word knowledge. The neuroimaging data further revealed areas in left orbitofrontal gyrus and bilateral inferior frontal gyrus with greater activation to emotional than to neutral words. These brain regions are known to be involved in processing semantic and emotional information. Furthermore, distinct activations associated with positive words were observed in bilateral middle temporal and superior frontal gyrus, known to support semantic retrieval, and a distributed network, namely anterior and posterior cingulate gyrus, lingual gyrus and hippocampus when comparing positive and negative words. The latter areas were previously associated with explicit and not incidental processing of the emotional meaning of words and emotional memory retrieval. Thus, the results are discussed in relation to models of processing semantic and episodic emotional information.

Adult↗

PubMed2005

Effects of syllable-frequency in lexical decision and naming: an eye-movement study.

In three experiments we explored task-specific effects of syllable-frequency, following Perea and Carreiras' (1998) findings of a facilitative effect during naming and an inhibitory effect during lexical decision. In Experiment 1, an inhibitory effect of first syllable-frequency on articulation duration suggested a process-specific effect during naming: a facilitative effect on construction of phonological output, but an inhibitory effect on lexical access. Eye-movement recording was used in Experiment 2 to disentangle these two processes. An inhibitory effect on eye-movement parameters during both lexical decision and naming supported the assumption that higher first syllable-frequency inhibits lexical access. Implications of a general inhibitory effect of syllable-frequency for computational models of word recognition, specifically for the multiple-trace memory (MTM) model of polysyllabic word naming (Ans, Carbonnel, & Valdois, 1998), are discussed.

Adult↗

PubMed2005

Frequency effects with visual words and syllables in a dyslexic reader.

The present study investigated the nature of the inhibitory syllable frequency effect, recently reported for normal readers, in a German-speaking dyslexic patient. The reading impairment was characterized as a severe deficit in naming single letters or words in the presence of spared lexical processing of visual word forms. Three visual lexical decision experiments were conducted with the dyslexic patient, an unimpaired control person matched to the patient and a control group: Experiment 1 manipulated the frequency of words and word-initial syllables and demonstrated systematic effects of both factors in normal readers and in the dyslexic patient. The syllable frequency effect was replicated in a second experiment with a more strictly controlled stimulus set. Experiment 3 confirmed the patient's deficit in activating phonological forms from written words by demonstrating that a pseudohomophone effect as observed in the unimpaired control participants was absent in the dyslexic patient.

Aged↗

PubMed2004

Inhibitory effects of first syllable-frequency in lexical decision: an event-related potential study.

Electrophysiological correlates of the behaviorally well-documented inhibitory effect of first syllable-frequency during lexical access are presented. In a lexical decision task, response times to words with high-frequency first syllables were longer than those to words with low-frequency first syllables and resulted in more negative event-related potentials (ERPs) in an early time window from 190 ms to 280 ms and in the N400 component. The onset of the observed first syllable-frequency effect was prior to the onset of the effect of lexicality (i.e., the first reliable differentiation in ERP waveforms in response to words and pseudowords, a potential marker of lexical access). The present study's results support Barber et al.'s [Neuroreport 15 (2004) 545] notion of the prelexical nature of the first syllable-frequency effect by (A) providing evidence for electrophysiological correlates of first syllable-frequency in another, non-Romance orthography (i.e., German), (B) relating the onset of the first syllable-frequency effect to the onset of the lexicality effect and (C) strengthening this pattern of results by means of a novel item-based analysis of ERP data. Implications of the prelexical nature of the inhibitory first syllable-frequency effect for computational models of reading, specifically for Ans et al.'s [Psychol. Rev. 105 (1998) 678] multiple-trace memory (MTM) model of reading are discussed.

Adult↗