Biomedical subjects

Arthur M Jacobs

Publications and source records attributed to Arthur M Jacobs.

14 recordsLinked to original sources

PubMed2006

Event-related theta activity reflects memory processes in pronoun resolution.

A recent eye-tracking study reported a reverse effect of a noun's lexical frequency in the context of the resolution of coreferring pronouns. Investigating the neurophysiological basis of this effect, the present electroencephalographic study found differential patterns in theta activation when participants read pronouns referring to nouns of different frequency classes. Evoked theta power after pronoun onset increased with the frequency of the critical noun. This finding suggests differential load on memory resources depending on the nouns' frequency. Elevated attention promoting memory encoding for low-frequency words is assumed to facilitate the resolution of pronouns. Location of sources of differential theta activity in the parahippocampal region is accounted for by its role in an association network that mediates memory processes.

Adolescent↗

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

Frequency and predictability effects on event-related potentials during reading.

Effects of frequency, predictability, and position of words on event-related potentials were assessed during word-by-word sentence reading in 48 subjects in an early and in a late time window corresponding to P200 and N400. Repeated measures multiple regression analyses revealed a P200 effect in the high-frequency range; also the P200 was larger on words at the beginning and end of sentences than on words in the middle of sentences (i.e., a quadratic effect of word position). Predictability strongly affected the N400 component; the effect was stronger for low than for high-frequency words. The P200 frequency effect indicates that high-frequency words are lexically accessed very fast, independent of context information. Effects on the N400 suggest that predictability strongly moderates the late access especially of low-frequency words. Thus, contextual facilitation on the N400 appears to reflect both lexical and post-lexical stages of word recognition, questioning a strict classification into lexical and post-lexical processes.

Adult↗

PubMed2006

Does the frequency of the antecedent noun affect the resolution of pronominal anaphors? An ERP study.

Behavioral studies investigating the influence of the relative word frequency of antecedent nouns on the processing of anaphoric pronouns have yielded contradictory results. While some researchers found no effect of an antecedent's frequency of occurrence on coreference resolution [J. Simner, R. Smyth, Phonological activation in anaphoric lexical access (ALA), Brain Lang. 68 (1999) 40-45], others report shorter reading times for pronouns referring to low compared to high frequency nouns [R.G.P. van Gompel, A. Majid, Antecedent frequency effects during the processing of pronouns, Cognition 90 (2004) 255-264]. Using event-related potentials, our study aimed to further investigate the issue. Participants were presented with sentence pairs, of which the first contained either a high frequency, a middle frequency or a low frequency noun. The second sentence contained a pronoun which referred back to the noun in the first sentence. ERP waves were determined, time-locked to both the nouns and the anaphoric pronouns. We observed a graded N400 effect for antecedents of the three frequency classes with amplitudes reversely related to the word's lexical frequency. Coreferential pronouns elicited a P300, with amplitudes dependent on the noun's relative frequency of occurrence, i.e. the lower the antecedent's word frequency, the higher was the amplitude of the P300. This amplitude effect at the pronoun is interpreted in terms of the allocation of attentional resources to salient discourse entities.

Adult↗

PubMed2006

Model-generated lexical activity predicts graded ERP amplitudes in lexical decision.

Recent neurocognitive studies of visual word recognition provide information about neuronal networks correlated with processes involved in lexical access and their time course (e.g., [Holcomb, Ph.J., Grainger J. and O'Rourke, T. (2002). An Electrophysiological Study of the Effects of Orthographic Neighborhood Size on Printed Word Perception, J. of Cogn. Neurosci. 14 938-950; Binder, J.R., McKiernan, K.A., Parsons, M.E., Westbury, C.F., Possing, E.T., Kaufman, J.N. and Buchanan, L. (2003). Neural Correlates of Lexical Access during Visual Word Recognition, J. Cogn. Neurosci. 15 372-393.]). These studies relate the orthographic neighborhood density of letter strings to the amount of global lexical activity in the brain, generated by a hypothetical mental lexicon as speculated in an early paper by [Jacobs, A.M. and Carr, T.H. (1995). Mind mappers and cognitive modelers: Toward cross-fertilization, Behav. Brain. Sci. 18 362-363]. The present study uses model-generated stimuli theoretically eliciting graded global lexical activity and relates this activity to activation of lexical processing networks using event-related potentials (ERPs). The results from a lexical decision task provide evidence for an effect of lexicality around 350 ms post-stimulus and also a graded effect of global lexical activity for nonwords around 500 ms post-stimulus. The data are interpreted as reflecting two different decision processes: an identification process based on local lexical activity underlying the 'yes' response to words and a temporal deadline process underlying the 'no' response to nonwords based on global lexical activity.

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.

Association↗

PubMed2005

Perhaps correlational but not causal: no effect of dyslexic readers' magnocellular system on their eye movements during reading.

During reading, dyslexic readers exhibit more and longer fixations and a higher percentage of regressions than normal readers. It is still a matter of debate, whether these divergent eye movement patterns of dyslexic readers reflect an underlying problem in word processing or whether they are - as the proponents of the magnocellular deficit hypothesis claim - associated with deficient visual perception that is causal for dyslexia. To overcome problems in the empirical linkage of the magnocellular theory with reading, a string processing task is presented that poses similar demands on visual perception (in terms of letter identification) and oculomotor control as reading does. Two experiments revealed no differences in the eye movement patterns of dyslexic and control readers performing this task. Furthermore, no relationship between the functionality of the participants' magnocellular system assessed by the coherent motion task and string processing were found. The perceptual and oculomotor demands required during string processing were functionally equivalent to those during reading and the presented consonant strings had similar visual characteristics as reading material. Thus, a strong inference can be drawn: Dyslexic readers do not seem to have difficulties with the accurate perception of letters and the control of their eye movements during reading - their reading difficulties therefore cannot be explained in terms of oculomotor and visuo-perceptual problems.

Adolescent↗

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

Syllable structure and sonority in language inventory and aphasic neologisms.

Phonological theories have raised the notion of a universally preferred syllable type which is defined in terms of its sonority structure (e.g., ). Empirical evidence for this notion has been provided by distributional analyses of natural languages and of language acquisition data, and by aphasic speech error analyses. The present study investigates frequency distributions of syllable types in German, which allows for a rather complex syllable structure, and in neologistic utterances of a German speaking jargon aphasic. The findings suggest that the sonority structure of the patient's neologisms is generally in accordance with the notion of theoretically preferred syllables. Moreover, comparative analyses suggest that the predominance of the preferred syllable type is especially pronounced in the aphasic data. On the basis of these findings, the influence of sonority in impaired phonological lexical processing is discussed.

Aphasia, Wernicke↗

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↗

PubMed2003

Receiver operating characteristics in the lexical decision task: evidence for a simple signal-detection process simulated by the multiple read-out model.

This study provides further evidence for the hypothesis that performance in the lexical decision task is based on the output of a signal detection mechanism, as implemented by the multiple read-out model of word recognition (MROM; J. Grainger & A. M. Jacobs, 1996). We extend the MROM to allow predictions of receiver operating characteristics in a data-limited variant of the lexical decision task and show that the model provides accurate descriptions of the data. Our results challenge all models of word recognition that do not include a familiarity assessment mechanism. They also suggest that under data-limited conditions a deadline mechanism for generating "no" responses in the lexical decision task may not necessarily be functional.

Decision Making↗

PubMed2002

Early contingent negative variation of the EEG and attentional flexibility are reduced in hypotension.

This study explored the question as to whether hypotension is related to decreased attentional performance and reduced cortical activation. A total of 50 females aged 19-44 years participated in the study. Attentional performance was assessed using three subtests of the Attentional and Cognitive Efficiency (ACE) battery. Contingent negative variation (CNV) as a measure of cortical activation was registered during a constant fore-period reaction time paradigm: two conditions were defined using tones as S1 (80 or 60 dB) and S2 (70 dB). The following results were obtained. Hypotensive patients performed significantly more poorly on one subtest of the ACE, which indicates a reduced speed for switching from a routine to a controlled response (quantifying attentional flexibility). They also had longer reaction times and revealed a significantly smaller amplitude of the early CNV component. In addition, a significant correlation was observed between systolic blood pressure and the amplitude of the early CNV component. The data support previous findings that hypotension can be related to lowered cortical activation and indicate that specific aspects of attentional performance might be negatively affected by hypotension.

Adult↗