Biomedical subjects

K Schiltz

Publications and source records attributed to K Schiltz.

7 recordsLinked to original sources

PubMed2006

Relationship between hippocampal structure and memory function in elderly humans.

With progressing age, the ability to recollect personal events declines, whereas familiarity-based memory remains relatively intact. It has been hypothesized that age-related hippocampal atrophy may contribute to this pattern because of its critical role for recollection in younger humans and after acute injury. Here, we show that hippocampal volume loss in healthy older persons correlates with gray matter loss (estimated with voxel-based morphometry) of the entire limbic system and shows no correlation with an electrophysiological (event-related potential [ERP]) index of recollection. Instead, it covaries with more substantial and less specific electrophysiological changes of stimulus processing. Age-related changes in another complementary structural measure, hippocampal diffusion, on the other hand, seemed to be more regionally selective and showed the expected correlation with the ERP index of recollection. Thus, hippocampal atrophy in older persons accompanies limbic atrophy, and its functional impact on memory is more fundamental than merely affecting recollection.

Adult↗

PubMed2002

[Lipomatosis dolorosa--a frequently overlooked disease picture].

Dercum's disease (lipomatosis dolorosa) is a relatively unknown illness. The disorder usually affects middle-aged females. Subcutaneous fatty tissue deposits may occur in many parts of the body. The upper arms, elbows, stomach wall, buttocks, thighs, or knees are most commonly affected. Severe hyperalgesia is found on light pressure and touch. Analgesics or pain-modulating drugs usually have little or no effect. The following case report demonstrates successful symptomatic treatment of the otherwise nearly unbearable complaints: intravenous infusions of 5 mg/kg body weight of lidocaine over 30-90 min may give pain relief lasting several weeks or even months. Alternatively, patients are treated with 150-750 mg orally administered mexiletine daily. Surgical excision or liposuction of these fatty tissue deposits have shown significant reduction of pain. However, this effect reduces over time and recurrences often develop.

Adiposis Dolorosa↗

PubMed2001

An electrophysiological analysis of the time course of conceptual and syntactic encoding during tacit picture naming.

A central question in psycholinguistic research is when various types of information involved in speaking (conceptual/semantic, syntactic, and phonological information) become available during the speech planning process. Competing theories attempt to distinguish between parallel and serial models. Here, we investigated the relative time courses of conceptual and syntactic encoding in a tacit picture-naming task via event-related brain potential (ERP) recordings. Participants viewed pictures and made dual-choice go/no-go decisions based on conceptual features (whether the depicted item was heavier or lighter than 500 g) and syntactic features (whether the picture's German name had feminine or masculine syntactic gender). In support of serial models of speech production, both the lateralized readiness potential, or LRP (related to response preparation), and the N200 (related to response inhibition) measures indicated that conceptual processing began approximately 80 msec earlier than syntactic processing.

Adult↗

PubMed2001

Control of semantic interference in episodic memory retrieval is associated with an anterior cingulate-prefrontal activation pattern.

Prefrontal activation is a consistent finding in functional neuroimaging studies of episodic memory retrieval. In the present study we aimed at a further analysis of prefrontal neural systems involved in the executive control of context-specific properties in episodic memory retrieval using an event-related fMRI design. Nine subjects were asked to learn two 20-item word lists that consisted of concrete nouns assigned to four semantic categories. Ten items of both word lists referred to the same semantic category. Subjects were instructed to determine whether nouns displayed in random order corresponded to the first 20-item target list. The interference evoked by the retrieval of semantically related items of the second list resulted in significantly longer reaction times compared to the noninterference condition. Contrasting the interference against the noninterference retrieval condition demonstrated an activation pattern that comprised a right anterior cingulate and frontal opercular area and a left-lateralized dorsolateral prefrontal region. Trial averaged time series revealed that the PFC areas were selectively activated at the interference condition and did not respond to the familiarity of learned words. These findings suggest a functionally separable role of prefrontal cortical areas mediating processes associated with the executive control of interfering context information in episodic memory retrieval.

Adult↗

PubMed1999

Decomposition of morphologically complex words in English: evidence from event-related brain potentials.

To explain processing differences between regular (e.g., start/started) and irregular (e.g., think/thought) word formation linguistic models posit either a single mechanism handling both morphological clusters or separate mechanisms for regular and irregular words. The purpose of the present study is to investigate how these processing differences map onto brain processes by assessing electrophysiological effects of English past tense forms, using the repetition priming paradigm. Event-related brain potentials (ERPs) were recorded from 59 scalp sites as 19 subjects read stem forms of regular and irregular verbs from a list of 1152 words; the stem forms were either preceded (5-9 intervening items) by their past tense forms (=primed condition) or by past tense forms of unrelated verbs (=unprimed condition). The difference between the ERPs to the primed and unprimed stems was taken as a measure of morphological priming. We found that the ERPs to regular verbs were clearly different from those to irregular verbs: the former were associated with an N400 reduction in the primed condition; primed irregular verb stems, however, showed no such effect. Control conditions demonstrated that the N400 modulation for regular verbs cannot be attributed to formal (i.e., phonological or orthographical) priming. These ERP effects indicate that regular verbs serve as more powerful primes for their corresponding stem forms than irregular past tense forms, suggesting that regular (but not irregular) past tense forms may be decomposed into stem plus affix.

Adolescent↗

PubMed1999

Neurophysiological aspects of synesthetic experience.

Synesthesia is a perceptual condition in which stimulation in one sensory modality elicits a concurrent sensation in another. The authors studied possible electrophysiological correlates of synesthetic experience in 17 subjects claiming to continuously experience chromatic-graphemical synesthesia and a matched control group. Subjects had to respond to one of four numbers and one of six letters by pressing a button. Even-related potentials (ERPs) were recorded from multiple scalp sites. Most synesthetic subjects reported strong synesthetic perceptions during the experiment. The ERPs of both groups showed a distinct P300 component when subjects encountered the assigned target number or letter. Synesthetic subjects had significantly and clearly more positive waveform over frontal and prefrontal scalp regions than control subjects for target and nontarget stimuli. This electrophysiological marker is discussed in terms of cortical inhibition in synesthetic subjects and the role of prefrontal regions in multisensory integration.

Adult↗

PubMed1998

When temporal terms belie conceptual order.

We conceive of time as a sequential order of real-world events, one event following another from past to present to future. This conception colours the way we speak of time ("we look forward to the time") and, as we show here, the way we process written statements referring to the temporal order of events, in real time. Terms such as 'before' and 'after' give us the linguistic freedom to express a series of events (real or imaginary) in any order. However, sentences that present events out of chronological order require additional discourse-level computation. Here we examine how and when these computations are carried out by contrasting brain potentials across two sentence types that differ only in their initial word ('After' X, Y versus 'Before' X, Y). At sites on the left frontal scalp, the responses to 'before' and 'after' sentences diverge within 300 ms; the size of this difference increases over the course of the sentences and is correlated with individual working-memory spans. Thus, we show that there are immediate and lasting consequences for neural processing of the discourse implications of a single word on sentence comprehension.

Brain Mapping↗