Biomedical subjects

Sabine Heim

Publications and source records attributed to Sabine Heim.

14 recordsLinked to original sources

PubMed2006

Development of structure and function in the infant brain: implications for cognition, language and social behaviour.

Recent advances in cognitive neuroscience have allowed us to begin investigating the development of both structure and function in the infant brain. However, despite the rapid evolution of technology, surprisingly few studies have examined the intersection between brain and behaviour over the first years of life. Even fewer have done so in the context of a particular research question. This paper aims to provide an overview of four domains that have been studied using techniques amenable to elucidating the brain/behaviour interface: language, face processing, object permanence, and joint attention, with particular emphasis on studies focusing on early development. The importance of the unique role of development and the interplay between structure and function is stressed throughout. It is hoped that this review will serve as a catalyst for further thinking about the substantial gaps in our understanding of the relationship between brain and behaviour across development. Further, our aim is to provide ideas about candidate brain areas that are likely to be implicated in particular behaviours or cognitive domains.

Animals↗

PubMed2006

Early cortical facilitation for emotionally arousing targets during the attentional blink.

BACKGROUND: The present study aimed to investigate the time course of electrocortical facilitation for affectively arousing written words during the so-called 'attentional blink' (AB) period in a rapid serial visual presentation (RSVP) task. The AB refers to a period of reduced awareness for second-target stimuli following a first target by an interval of about 200-500 ms. Pleasant, neutral, and unpleasant written verbs were used as second targets in an 8.6-Hz RSVP paradigm that contained affectively neutral words as distractors. Replicating and extending behavioral studies, we expected that emotional second targets would be associated with better identification accuracy and greater electrocortical activity, compared with neutral targets. RESULTS: The steady-state visual evoked potential was recorded using 129 scalp electrodes. The time-varying energy at the presentation frequency of 8.6 Hz was extracted as a continuous measure of electrocortical activity related to the RSVP stream. Behavioral data showed that at an inter-target interval of 232 ms, the report for emotionally arousing (pleasant and unpleasant) words was more accurate than for neutral control words. This result was mirrored by the electrocortical response at posterior sensors, which showed rapid amplitude enhancement (120-270 ms after T2 onset) for pleasant and unpleasant targets specifically. CONCLUSION: The present data suggest that identification facilitation for emotionally arousing target words in the AB is related to rapid enhancement of sensory processing. Affectively arousing information is preferentially selected at the level of early perceptual analysis, leading to facilitation at later stages of processing, including consolidation in working memory and visual awareness.

Adolescent↗

PubMed2006

Acquisition of affective dispositions in dementia patients.

In this study, we investigated the acquisition of affective dispositions towards neutral faces in patients with Alzheimer's disease and mixed dementia. Participants viewed four affectively neutral male faces from the International Affective Picture System. Biographical information about the depicted persons was presented, which described them in terms of positive or negative traits varying in intensity. Participants were asked to rate the pictures with respect to emotional valence, arousal, and preference prior to and after the presentation of the biographical information. Following a retention interval of 180 min, pictures were rated again and the biographical information was presented once more. Final ratings were obtained after another interval of 1300 min. As expected, healthy control participants identified the faces and recalled parts of the information in the delayed recall test. They showed pronounced changes in affective ratings. Patients did not recognize the faces in a recognition test after the retention intervals, but valence, arousal, and preference ratings were systematically altered by the affective content of biographies. The results suggest that acquisition and maintenance of implicit affective dispositions are preserved in dementia even when explicit memory is impaired.

Affect↗

PubMed2006

Effects of classical conditioning on identification and cortical processing of speech syllables.

The present study was designed to examine effects of learned motivational significance on processing of speech syllables in adults using a classical conditioning paradigm. Aversive white noise (unconditioned stimulus) was paired with two exemplars of /ba/ (conditioned stimulus, CS+) occurring near the category boundary of a 10-item /ba/-da/ continuum. Two corresponding /da/ syllables served as the CS- and indicated absence of white noise. High-density electroencephalogram (EEG) was recorded while participants passively listened to the stimuli. Prior to the EEG session and after intermittent conditioning, participants were asked to identify the syllables in a categorical perception task. Analysis of time-locked electrocortical data revealed amplitude modulations of the N2 (248-312 ms) component as a function of acquired stimulus properties (CS+ versus CS-). Over right hemisphere regions, negativity was specifically enhanced for the CS+ during intermittent conditioning. During extinction, this conditioning effect was paralleled by findings in the time-frequency domain, showing greater oscillatory activity in the gamma-band (25-40 Hz) range, 80-120 ms following onset of the CS+ compared with CS-. A similar pattern emerged in a later time segment of 400-600 ms (30-45 Hz). Aversive conditioning was not reflected in superior categorical perception performance. Our data indicate that electrocortical correlates of speech syllable perception are susceptible to changes induced by contingencies. Physiological differences were not manifest in behavioral advantage for a specific stimulus, i.e., the CS+, however. We conclude that training speech categorization by merely enhancing motivational relevance is not effective for conveying behavioral improvement.

Adolescent↗

PubMed2005

Lipophilic organic contaminants in the Rhine river, Germany.

Detailed gas chromatographic-mass spectrometric analyses applied to eight Rhine river water samples constituted a comprehensive characterization of the low molecular weight organic contamination. Within the group of predominant anthropogenic contaminants, only a few compounds were characterized as frequently detected or priority pollutants. Numerous compounds exhibiting physiological or ecotoxicological properties are only rarely reported or still unnoticed riverine contaminants. Information on environmental behaviour or ecotoxicological effects is still limited for most of these substances. In particular, several brominated compounds (mono- and dibrominated (methoxyphenyl)propionic acids and hydroxymethylacetophenones) were identified for the first time as environmental contaminants. Quantitative analyses differentiated five groups of pollutants with respect to their concentration profiles. The spatial distribution and the intensity of emission sources on the one hand and the environmental stability as well as the tendency to adsorb on the particulate matter on the other hand determined the quantitative occurrence of individual compounds.

Acetophenones↗

PubMed2005

Reduced hemispheric asymmetry of the auditory N260m in dyslexia.

Dyslexia seems to be related to a lack of planum temporale (PT) asymmetry that is accompanied by functional differences to control subjects in both left and right hemispheric temporal regions during language tasks. PT asymmetry has been found to correlate with phonological and verbal skills. In accordance, reduced asymmetry of the auditory N100m sources in dyslexic adults and P100m sources in dyslexic children has been reported. These results might also be related to an atypical PT symmetry or the recruitment of other structures than the PT for speech processing in dyslexia. In the present study we tried to replicate and extend previous findings by examining a sample of 64 dyslexic and 22 control children in the MEG. We measured cortical activity during a passive auditory oddball-paradigm and localised ERF sources evoked by the standard stimulus /ba/. Reduced hemispheric asymmetry in the localisation of the auditory N260m was revealed. While control children displayed a typical asymmetrical pattern with more anterior sources in the right hemisphere, this asymmetry was not present for the dyslexic children. Further, a correlation between N260m asymmetry and spelling test performance was found. Our results suggest that localisation of ERF components is indeed an applicative tool for investigating cortical deviances in dyslexia. A lack of source localisation asymmetry in dyslexia appears to be a robust finding across different samples of dyslexic children and adults. It appears that cortical auditory (language) processing is organised differently in dyslexic subjects than in controls. This might be the consequence of a more symmetrical PT organisation, which in turn might be the result of maturational delay.

Acoustic Stimulation↗

PubMed2004

Timing errors in auditory event-related potentials.

Electronic problems of electroencephalographic (EEG) system may occur in even the best-managed laboratories. Timing error may happen in the coupling of computers from various manufactures, resulting in the misalignment of event markers that signal the onset of stimuli. In one system, an impedance check desynchronized a computer and thus caused misalignment of events in EEG signals. Thus, the aim of this study was to develop a method to identify and correct such timing errors that contaminated 114 raw data of EEG/auditory event-related potentials (ERPs) recorded in one of our longitudinal studies. A two-step procedure was introduced in the correction of timing errors. First, the time delay was roughly estimated by identifying a P150 component in two ERP blocks. Second, a small phase-locked positive wave was identified for fine estimation. Reliability within and among evaluators was examined using ERP data with simulated timing errors. Concordant results were obtained in 104 (91.2%) of the 114 raw EEG/ERP data sets. Our results showed that the method presented here is reliable and can be used for correcting timing errors without introduction of experimenter bias.

Acoustic Stimulation↗

PubMed2004

Large-scale neural correlates of developmental dyslexia.

Recent work in the field of developmental dyslexia has emphasized the large-scale neural aspects of the disorder as measured by means of contemporary imaging techniques, electrophysiology, and post-mortem analyses. This article presents findings from these research domains and comprehensively reviews their relevance with respect to the behavioral and cognitive profiles of dyslexia. Large-scale alterations were observed in the perisylvian region across paradigms. Convergent evidence has also been reported in terms of hemispheric balance. Specifically, deviances in cerebral asymmetry associated with atypical organization of the left hemisphere were found in both children and adults with dyslexia. Emerging research encompassing high-temporal resolution methods such as magnetoencephalography (MEG) suggests right-hemisphere involvement and points to the complexity of the developmental disorder. A combined approach of structural imaging and MEG, and most importantly theory driven behavioral tasks may shed light on dynamics and trajectories of the neurobiology of dyslexia.

Adult↗

PubMed2004

Cerebral lateralization in schizophrenia and dyslexia: neuromagnetic responses to auditory stimuli.

Many studies have shown altered hemispheric asymmetry-particularly in perisylvian regions-in schizophrenia patients as well as in individuals with dyslexia. Here we explore the similarity of these findings comparing the localization of the magnetic auditory N100m to the German syllable [ba:] in schizophrenia patients, dyslexic adults, and healthy control subjects. Control subjects showed the typical finding of more anterior sources in the right than in the left perisylvian region. In contrast, both schizophrenia patients and dyslexic subjects displayed a symmetrical N100m source configuration. While in people with dyslexia the alteration appears to originate in the right hemisphere, left-hemispheric deviations might contribute to reduced asymmetry in schizophrenia patients. Our results indicate that an absence of lateralized auditory responses in the temporal lobes may reflect a common deviance present in dyslexia and schizophrenia. The nonspecific finding of reduced cerebral laterality may be accounted for by population-specific differences in the functional organization of perisylvian sites.

Acoustic Stimulation↗

PubMed2004

Anthropogenic organic contaminants in sediments of the Lippe river, Germany.

Sediment samples of the Lippe river (Germany) taken between August 1999 and March 2001 were investigated by GC-MS-analyses. These analyses were performed as non-target-screening approaches in order to identify a wide range of anthropogenic organic contaminants. Unknown contaminants like 3,6-dichlorocarbazole and bis(4-octylphenyl)amine as well as anthropogenic molecular marker compounds were selected for quantification. The obtained qualitative and quantitative analytical results were interpreted in order to visualize the anthropogenic contamination of the Lippe river including spatial distribution, input effects and time dependent occurrence. Anthropogenic molecular markers derived from municipal sources like polycyclic musks, 4-oxoisophorone and methyltriclosan as well as from agricultural sources (hexachlorobenzene) were gathered. In addition molecular markers derived from effluents of three different industrial branches, e.g. halogenated organics, tetrachlorobenzyltoluenes and tetrabutyltin, were identified. While municipal and agricultural contaminations were ubiquitous and diffusive, industrial emission sources were spatially isolated. Specific seasonal trends of distribution patterns were not observed.

Environmental Monitoring↗

PubMed2003

Altered hemispheric asymmetry of auditory N100m in adults with developmental dyslexia.

The current study aimed at determining whether the deviance of hemispheric asymmetry in the auditory cortex of children with dyslexia is also evident in dyslexic adults. Ten adult dyslexic subjects and 10 normally literate controls were presented with the syllable [ba:] while event-related brain activity was recorded from both hemispheres using whole-head magnetoencephalography. In control subjects, the auditory N100m source was found to be asymmetrical with a more anterior localization in the right than in the left perisylvian cortex (difference = 0.78 cm). The N100 m dipoles in dyslexic adults did not exhibit the same interhemispheric asymmetry (difference = -0.06 cm). The results indicate that reduced hemispheric laterality of perisylvian regions in dyslexia persists into adulthood.

Adult↗

PubMed2003

Temporal stability of high-frequency brain oscillations in the human EEG.

Temporal stability of a given measurement within individual participants is a desirable property of psychophysiological measures. The present study aims to examine the reliability of high-frequency oscillatory activity in the human electroencephalogram (EEG) across 4 sessions. Convolution of the EEG time series with Morlet wavelets yielded time-frequency representations of the signal for each session. Stability of both topography and time course of gamma-band activity (GBA) was determined for two participants performing a feature-based selective attention task in four separate sessions, spaced at weekly intervals. We found high temporal stability of non-phase-locked GBA typically occurring in time ranges between 200 and 500 ms following presentation of a stimulus, both in terms of topography and time course. Early phase-locked GBA (80-120 ms) showed higher variability with respect to topography, but was consistent in terms of time course. We conclude that measures of high-frequency oscillatory activity as used in the cognitive neurosciences meet stability requirements necessary for meaningful interpretation of this parameter of brain function.

Adult↗

PubMed2003

Altered hemispheric asymmetry of auditory P100m in dyslexia.

In various studies, deviances of hemispheric laterality in the organization of the perisylvian region in dyslexia have been suggested. Although associated with impaired language functioning, the clinical significance of atypical cerebral lateralization remains unclear. The present study examined interhemispheric source differences of magnetic responses to the German synthetic syllable [ba:] in the auditory cortex of 14 dyslexic children and 12 normally literate controls aged 8-15 years. In all subjects, two main deflections, P100m and N260m, were evident in the responses over each hemisphere. While in the control group the right P100m dipole was located more anterior than the corresponding dipole of the left hemisphere, the dyslexic group displayed a rather symmetrical source configuration between the hemispheres. This symmetry reflected a deviance in the right perisylvian region for the dyslexic subjects' P100m, which was generated approximately 1 cm more posterior than the response in controls. The deviation was also obvious relative to the source location of the later component, N260m, which did not systematically differ between the participant groups. Our results suggest that the altered hemispheric asymmetry reflects an atypical organization of the right hemisphere in children and adolescents with dyslexia.

Acoustic Stimulation↗

PubMed2002

Occurrence and alteration of organic contaminants in seepage and leakage water from a waste deposit landfill.

Organic-geochemical analyses have been applied to seepage water and leakage water samples of a waste deposit landfill in order to give a comprehensive view on the composition of the organic contaminants. Based on intense GC/MS screening analyses a wide variety of organic substances were identified and attributed to natural or xenobiotic waste components. Apart from plant material-derived compounds and degradation products of peptides, carbohydrates and lignin, numerous xenobiotic substances were identified and attributed to the groups of pharmaceuticals, plasticizers, pesticides or chlorinated aromatics. Not all of the substances identified in the seepage water samples were recovered in the leakage water sample due to degradation processes or dilution by uncontaminated water. Quantitative analysis of selected contaminants was used to discriminate substances affected by degradation processes and persistent compounds.

Biodegradation, Environmental↗