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Jürgen Reul

Publications and source records attributed to Jürgen Reul.

10 recordsLinked to original sources
PubMed2004

Differences of cerebral activation between superior and inferior learners during motor sequence encoding and retrieval.

Cerebral activation during memory encoding and retrieval might depend on subjects' learning capacity, either by corresponding to better performance in superior learners or by reflecting increased effort in inferior learners. To investigate these alternative hypotheses, the study compared cerebral activation during encoding and retrieval of a motor sequence in groups of subjects with superior and inferior learning performances. Ten healthy subjects underwent functional magnetic resonance imaging (fMRI) while performing a motor sequence encoding paradigm (i.e. finger tapping sequence) and a retrieval paradigm (i.e. reproduction of the learned sequence). Subjects were divided into superior and inferior learners according to the correctness of sequence reproduction during retrieval. During encoding, there was strong bilateral activation in the middle frontal gyrus, the supplementary motor area (SMA), the lateral parietal lobe and the cerebellum. During retrieval, again strong activation was found in identical areas of the prefrontal cortex, the parietal lobe and the cerebellum. During encoding, inferior learners showed more left-sided activations in the left middle frontal and inferior parietal gyri. Superior learners showed increased activation in the corresponding right-sided brain areas during encoding as well as during retrieval. Differences of cerebral activations in the prefrontal and parietal cortex during encoding and retrieval were found to be related to retrieval performance, i.e. success and effort. Further intervention studies are needed to assess whether these interindividual differences are the cause or the consequence of differences in memory performance.

Achievement↗
PubMed2004

Evidence for a dysfunctional retrosplenial cortex in patients with schizophrenia: a functional magnetic resonance imaging study with a semantic-perceptual contrast.

We investigated whether the retrosplenial and the posterior cingulate cortex (RS-PCC) is functionally impaired in schizophrenia patients. Therefore, we measured functional magnetic resonance imaging (fMRI) signal changes associated with a synonym-judgment task known to activate, among other areas, the RS-PCC. Compared to 12 matched control subjects, 12 schizophrenia patients exhibited reliably weaker activations in the RS-PCC, the dorsolateral prefrontal cortex and the left orbitofrontal cortex (P < 0.05, corrected). Differences in frontal activations are in line with previous studies showing a structurally and functionally affected prefrontal cortex in schizophrenia. The impaired RS-PCC functionality in a semantic task may relate to verbal memory deficits frequently observed in schizophrenia patients, because this region is pivotal for gating information into the medial temporal lobe memory system.

Brain Mapping↗
PubMed2004

Cranial magnetic resonance imaging in genetically proven myotonic dystrophy type 1 and 2.

Cranial magnetic resonance imaging (MRI) in 19 German patients with genetically proven myotonic dystrophy Type 1 (DM1, n = 10) or Type 2 (DM2, n = 9) showed pathological findings consisting of white matter lesions (WML) and/or brain atrophy in 9/10 DM1 and 8/9 DM2 patients. Anterior temporal WML (ATWML) were exclusively seen in DM1 patients. Our findings indicate a high frequency of central nervous system (CNS) involvement in both disorders. However, temporopolar pathology, previously associated with intellectual dysfunction, seems to be restricted to DM1.

Adult↗
PubMed2004

Using visual advance information: an event-related functional MRI study.

Our event-related functional MRI (efMRI) study investigates whether visual advance information (AI) affects rather perceptual or central response-related processing areas. Twelve subjects were required to make a go/no-go decision to a conjunction of a specific color and motion direction. The stimuli were preceded by a cue, providing 100% valid advance information about motion direction. Partial and full advance information (PAI and FAI) predicted possible targets, respectively, certain nontargets, neutral cues (NAI) gave no prediction. The time between cue and stimulus (stimulus onset asynchrony, SOA) was varied. A response benefit was found after PAI as compared with NAI. The benefit was small with a short SOA (150 ms), increased with intermediate SOA (450 ms) and sustained with long SOA (750 ms). Perceptual and central processing areas were more active with increasing SOA, but only central response-related processing areas were selectively modulated by cue information. In particular, supplementary motor area and bilateral inferior parietal lobe were more active with PAI than with NAI. If comparing NAI with FAI, more errors were made and activity was larger in central processing areas. Our results suggest that, depending on the processing time, cues providing perceptual information modulate central response-related processes.

Adult↗
PubMed2004

Temporal and cerebellar brain regions that support both declarative memory formation and retrieval.

Using event-related fMRI, we scanned young healthy subjects while they memorized real-world photographs and subsequently tried to recognize them within a series of new photographs. We confirmed that activity in the medial temporal lobe (MTL) and inferior prefrontal cortex correlates with declarative memory formation as defined by the subsequent memory effect, stronger responses to subsequently remembered than forgotten items. Additionally, we confirmed that activity in specific regions within the parietal lobe, anterior prefrontal cortex, anterior cingulate and cerebellum correlate with recognition memory as measured by the conventional old/new effect, stronger responses for recognized old items (hits) than correctly identified new items (correct rejections). To obtain a purer measure of recognition success, we introduced two recognition effects by comparing brain responses to hits and old items misclassified as new (misses). The positive recognition effect (hits > misses) revealed prefrontal, parietal and cerebellar contributions to recognition, and in line with electrophysiological findings, the negative recognition effect (hits < misses) revealed an anterior medial temporal contribution. Finally, by inclusive masking, we identified temporal and cerebellar brain areas that support both declarative memory formation and retrieval. For matching operations during recognition, these areas may re-use representations formed and stored locally during encoding.

Adult↗
PubMed2003

Menstrual cycle-dependent neural plasticity in the adult human brain is hormone, task, and region specific.

In rodents, cyclically fluctuating levels of gonadal steroid hormones modulate neural plasticity by altering synaptic transmission and synaptogenesis. Alterations of mood and cognition observed during the menstrual cycle suggest that steroid-related plasticity also occurs in humans. Cycle phase-dependent differences in cognitive performance have almost exclusively been found in tasks probing lateralized neuronal domains, i.e., cognitive domains such as language, which are predominantly executed by one hemisphere. To search for neural correlates of hormonally mediated neural plasticity in humans, we thus conducted a functional magnetic resonance imaging study measuring brain activity related to a semantic decision task in the language domain. This was contrasted with a letter-matching task in the perceptual domain, in which we expected no steroid hormone-mediated effect. We investigated 12 young healthy women in a counterbalanced repeated-measure design during low-steroid menstruation and high-steroid midluteal phase. Steroid serum levels correlated with the volume and lateralization of particular brain activations related to the semantic task but not with brain activity related to the perceptual task. More specifically, bilateral superior temporal recruitment correlated positively with progesterone and medial superior frontal recruitment with both progesterone and estradiol serum levels, whereas activations in inferior and middle frontal cortex were unaffected by steroid levels. In contrast to these specific interactions, testosterone levels correlated nonselectively with overall activation levels by neural and/or vascular factor(s). In conclusion, our data demonstrate steroid hormone responsivity in the adult human brain by revealing neural plasticity in the language domain, which appears hormone, task, and region specific.

Adult↗
PubMed2003

In vivo voxel-based morphometry in multiple system atrophy of the cerebellar type.

BACKGROUND: Multiple system atrophy (MSA) is a sporadic neurodegenerative disease. According to the clinical presentation a parkinsonian type and a cerebellar type (MSA-C) are distinguished. OBJECTIVE: To study the morphological alterations of MSA-C-affected brains in vivo using voxel-based morphometric analysis of magnetic resonance images. SETTING: University hospital. PATIENTS: Fourteen patients (5 men and 9 women) with MSA-C (mean age [SD], 59.4 [7.4] years; mean [SD] disease duration, 3.7 [1.4] years) and 13 healthy control subjects (5 men and 8 women) (mean [SD] age, 55.1 [6.9] years) were studied. METHODS: T1-weighted magnetic resonance images were normalized to a common stereotaxic space and segmented into gray and white matter. Data were analyzed using statistical parametric mapping (SPM99). RESULTS: Gray matter was reduced in the brainstem and the anterior lobe of the cerebellum. Reduction of white matter was observed in the middle cerebellar peduncles, cerebellar white matter, and brainstem. The inverted comparison revealed an increase of white matter density along the pyramidal tracts. CONCLUSIONS: Voxel-based morphometry revealed a significant loss of cerebellar and brainstem tissue in MSA-C. It allowed a precise anatomical localization and a distinction between gray and white matter densities. In addition, our data point to a particular involvement of the pyramidal tract in MSA-C.

Brain Stem↗
PubMed2003

Functional segregation of the temporal lobes into highly differentiated subsystems for auditory perception: an auditory rapid event-related fMRI-task.

With this study, we explored the blood oxygen level-dependent responses within the temporal lobe to short auditory stimuli of different classes. To address this issue, we performed an attentive listening event-related fMRI study, where subjects were required to concentrate during the presentation of different types of stimuli. Because the order of stimuli was randomized and not predictable for the subject, the observed differences between the stimuli types were interpreted as an automatic effect and were not affected by attention. We used three types of stimuli: tones, sounds of animals and instruments, and words. We found in all cases bilateral activations of the primary and secondary auditory cortex. The strength and lateralization depended on the type of stimulus. The tone trials led to the weakest and smallest activations. The perception of sounds increased the activated network bilaterally into the superior temporal sulcus mainly on the right and the perception of words led to the highest activation within the left superior temporal sulcus as well as in left inferior frontal gyrus. Within the left temporal sulcus, we were able to distinguish between different subsystems, showing an extending activation from posterior to anterior for speech and speechlike information. Whereas posterior parts were involved in analyzing the complex auditory structure of sounds and speech, the middle and anterior parts responded strongest only in the perception of speech. In summary, a functional segregation of the temporal lobes into several subsystems responsible for auditory processing was visible. A lateralization for verbal stimuli to the left and sounds to the right was already detectable when short stimuli were used.

Acoustic Stimulation↗
PubMedDate not supplied

"Soundmorphing": a new approach to studying speech perception in humans.

A problem in current studies of brain activation in speech perception is that most studies use stimuli that are sampled from different categories. This study presents a new approach in creating acoustic stimuli by filtering real words in different ways, thus this enables one to 'morph' the sounds gradually from something like tones to real words while preserving temporal characteristics ("soundmorphing"). This will make it possible to explore steps between tone and speech processing on a gradual scale. This study aimed to investigate more closely the network, involved in the perception of speech and the decoding of auditory (speech-)stimuli. Sets of auditory stimuli were created by dividing real words into several frequency-bands and creating a randomised rearrangement of these components. Four different sets of stimuli were used, containing 1, 2, 3 or 4 frequency bands (total range: 0-2500 Hz). Only the latter one contained intelligible words. During the fMRI session, these four trial types were presented pseudo-randomised. In all conditions, significant activations of auditory cortex were observed. The number of activated voxels and their significance increased over the four trial types. In addition, Broca's area, SMA, left thalamus, and right cerebellum were activated in the most complex and most speech-like condition. Comparing these complexes with the tone-like trials, only the left auditory cortex, left SMA, and cingulate gyrus became significant. These activations reflect the bilateral processing of the auditory stimuli, but only the left temporal areas demonstrated an increasing BOLD response with an increasing number of presented frequency components.

Acoustic Stimulation↗