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A P Wunderlich

Publications and source records attributed to A P Wunderlich.

15 recordsLinked to original sources
PubMed2006

Inhibition of hippocampal function in mild cognitive impairment: targeting the cholinergic hypothesis.

Mild cognitive impairment (MCI) is a condition with an increased risk of developing Alzheimer's disease. Chief complaint and diagnostic criterion in subjects with mild cognitive impairment is memory failure. We hypothesized that cholinergic malfunction may underlie memory impairment in these subjects and applied a low dosage of an acetylcholinesterase inhibitor and modulator of nicotinic acetylcholine receptors, galantamine (4 mg bid), for 7 days. We used neuropsychological tests to investigate attention, cognitive flexibility, verbal and visual short-term and working memory, susceptibility to interference and episodic memory and functional magnetic resonance imaging to assess spatial navigation both prior to and after treatment. Late episodic learning and delayed recall improved on treatment as did recruitment of the hippocampal region during spatial navigation. Performance in all other neuropsychological measures remained unchanged. We show that an increase of cholinergic neurotransmission in subjects with MCI specifically improves hippocampal function and thus that a cholinergic deficit is functionally relevant in subjects with MCI. Malfunction of the cholinergic system may be tackled pharmacologically via the inhibition of acetylcholinesterase even when the impairment is slight.

Acetylcholine↗
PubMed2003

Alike performance during nonverbal episodic learning from diversely imprinted neural networks.

Performance on neuropsychological testing permits inferences to be made regarding neural networks required to solve the task. In healthy young human subjects it is common sense that differential performance in cognitive tasks results from recruitment of different neural networks and that alike performance results from recruitment of alike neural networks. It was the goal of the present study to investigate whether these assumptions are also valid in cross-cultural studies. To address this, we used functional MRI during a nonverbal episodic memory task with repeated learning of abstract geometric patterns. Behavioural performance in this task was alike over repeated trials in native Chinese and Caucasian subjects. Given this equivalent performance, the distinct pattern of neuronal activation observed is interpreted as the outcome of different culturally imprinted processing routines. In the 'what' and 'where' framework of visuo-spatial processing initial learning in Chinese subjects activated the dorsal stream for analysis of spatial features whereas Caucasians recruited the ventral stream for object identification. With repeated learning Chinese subjects integrated visuo-spatial processing to object coding and vice versa. Thus, imprints of culture result in activation of distinct neural networks and mandate monitoring of both behavioural performance and neural recruitment in cross-cultural studies of cognition.

Adult↗
PubMed2001

The navigation of transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is a new method for investigating cortical information processing and for investigating therapeutic applications in psychiatry and neurology. A common problem of most studies in this field regards the localization of the magnetic coil with respect to the cortex. This article reviews the currently used methods and proposes a neuronavigational approach. The method of neuronavigated TMS is described and discussed in detail. It is used to guide the magnetic coil on an individual basis to a structurally or functionally predetermined cortical area while monitoring the location of the coil in relation to the subject's head in real time. Possible applications of TMS in combination with functional neuroimaging in clinical research within a cognitive neuroscience framework are discussed. Future applications of TMS should take individual anatomy into account, and neuronavigation provides the means to do so.

Brain Mapping↗
PubMed2001

The neural correlates of driving.

We studied 12 healthy subjects with fMRI while they performed a driving simulation task. In the active condition they steered the car themselves (driving), in the passive condition a person from outside the scanner was steering the car (passive driving). Common activations in both conditions were found in occipital and parietal regions bilaterally. Activity specifically associated with driving was found only in the sensorimotor cortex and the cerebellum. Compared to passive driving, activity during driving was reduced in numerous brain regions including MT/MST. It is concluded that simulated driving requires mainly perceptual-motor integration and that the limited cognitive capacity model of driving has to be revised.

Adult↗
PubMed2001

Enantio-selective cognitive and brain activation effects of N-ethyl-3,4-methylenedioxyamphetamine in humans.

In a randomised double-blind trial the subjective, neuropsychological and brain activation effects of the two enantiomers of the MDMA (ecstasy-) like drug N-ethyl-3,4-methylenedioxyamphetamine (MDE) were studied in five normal subjects using functional magnetic resonance imaging (fMRI). (S)-MDE produced elevated mood, impairments in conceptually driven cognition and marked right frontal activation. In contrast, (R)-MDE produced increased depression, enhanced visual feature processing, and activation of visual cortical and left frontal areas. Plasma concentrations were higher for the (R)-enantiomer. The so-called entactogenic effects of MDE are likely to be caused by the (S)-enantiomer, whereas (R)-MDE appears to be responsible for neurotoxic effects.

3,4-Methylenedioxyamphetamine↗
PubMed2000

Brain activation during human navigation: gender-different neural networks as substrate of performance.

Visuospatial navigation in animals and human subjects is generally studied using maze exploration. We used functional MRI to observe brain activation in male and female subjects as they searched for the way out of a complex, three-dimensional, virtual-reality maze. Navigation activated the medial occipital gyri, lateral and medial parietal regions, posterior cingulate and parahippocampal gyri as well as the right hippocampus proper. Gender-specific group analysis revealed distinct activation of the left hippocampus in males, whereas females consistently recruited right parietal and right prefrontal cortex. Thus we demonstrate a neural substrate of well established human gender differences in spatial-cognition performance.

Adult↗
PubMed1998

[High-resolution virtual laryngoscopy based on spiral CT data].

This pilot study investigated the feasibility and clinical value of high-resolution virtual real-time laryngoscopy based on helical CT data sets. Nine patients with laryngeal pathology (three with tumors of the vocal cords, two laryngeal carcinomas, one with invasion of the larynx by thyroid carcinoma and six subglottic stenoses) underwent examination by helical CT at a collimation of 1 mm. Following acquisition, the images were processed at a workstation with standard visualization software, such that virtual endoscopy (VE) in real time was possible. The images were then compared with the findings of conventional endoscopy. Because of swallowing artifacts, reconstruction failed in 2 of 12 patients. None of the carcinomas of the vocal cords was recognized at VE or in the cross-sectional CT images. VE provided the correct diagnosis in 8 of 12 cases (laryngeal tumors, subglottic stenoses). Virtual laryngoscopy is capable of simulating the visual findings of endoscopy in cases of laryngeal tumors and subglottic stenoses. Small tumors of the vocal cords are not adequately visualized. The major problem affecting results is motion artifacts resulting from involuntary swallowing.

Aged↗
PubMed1996

[Spiral CT angiography: computed improvement of the slice thickness profile].

It is possible to improve on the low skirt selectivity of the slice sensitivity profile (SSP) in spiral CT by interpolation of the raw data or suitable image after-processing. We determined the SSP function of spiral CT by means of a plexiglas phantom which we subsequently modified empirically-mathematically by a correction function until we obtained maximum possible skirt selectivity and smallest possible FWHM (= full width at half maximum) of the corrected image data set. The corrected image data set was obtained by bilateral convolution of a real image data set with a correction function. This resulted in most cases in a more realistic imaging of the angiographic morphology when applied to SSD and MIP (3D) reconstructions of a. mesenterica sup. and tr. coeliacus from spiral CT data sets, compared with the original data sets.

Celiac Artery↗
PubMed1993

[Color-coded three-dimensional reconstruction from spiral CT data sets: physical viewpoint for improvement of the method].

This paper demonstrates the possibility of improving the spatial depth impression of colour-coded three-dimensional reconstructions by modulation of colour saturation. Patients were observed with spiral computed tomography (slice thickness 10 mm, table feed 10 mm/s, reconstruction of overlapping axial images at 2 mm increment). Interesting anatomical and pathological objects (vessels, organs, tumours, metastases) were segmented, colour-coded, and reconstructed three-dimensionally. Spatial depth impression of the coloured objects could be improved by modulating not only the brightness, but also the colour saturation.

Aorta, Abdominal↗
PubMed1993

[Spiral CT in aortic aneurysms. 2D and 3D reconstructions and CT angiography].

Spiral CT was performed in 8 normals and 40 patients with alterations of the large thoracic and abdominal vessels. It proved to be the ideal basis for 2D and 3D reconstructions. In 2D reconstruction the topographic aspects of aortic aneurysms were displayed better compared to the axial scans. In 3D reconstruction the segmentation of small vessels, and vessels running parallel to the scan plane showed problems. Stenoses were displayed unsatisfactory. In patients with aortic aneurysms 3D reconstruction showed well the location and dimension of the aneurysm as well as its position to branching arteries and the intraarterial thrombus. In case of dissecting aneurysms the true and the false lumen could clearly be distinguished. Colour-coded 3D reconstruction proved to be valuable to illustrate topographic information that could be detected only with difficulty on examining the original axial scan.

Aged↗
PubMedDate not supplied

fMRI for preoperative neurosurgical mapping of motor cortex and language in a clinical setting.

PURPOSE: Identification of the precentral gyrus can be difficult in patients with brain tumors. The purpose of the current study was to evaluate the clinical usefulness of functional MRI (fMRI) in identifying motor cortex and speech areas as a part of preoperative neurosurgical planning. METHOD: fMRI was performed using a 1.5 T MR unit in 41 patients with brain tumors. The motor paradigm was finger tapping and foot movement, whereas the language paradigm consisted of a two word semantic test. Statistical analysis of the data was done using the Kolmogorow-Smirnow test. Plots of signal intensities over time were created. RESULTS: The precentral gyrus was identified in 38 of 41 patients. In two patients, fMRI was not of acceptable quality due to motion artifacts. Speech areas were localized in 33 patients. In a typical clinical setting, the value of the method was graded "high." CONCLUSION: fMRI's efficacy in the preoperative localization of language and motor areas is high. The method should become a routine adjunct for preoperative evaluation of brain tumors in the near future.

Adult↗
PubMedDate not supplied

Hippocampal activations during repetitive learning and recall of geometric patterns.

Hippocampal activation is required for episodic memory. Encoding and retrieval of novel and memorable items have been related to different locations in the hippocampus; however, the data remain ambiguous. The application of a newly designed keyboard allowed investigation of brain activation during encoding and free immediate and delayed recall with functional magnetic resonance imaging (fMRI) in young healthy controls (n = 12). Because of the repetitive learning and recall conditions, an individual learning gradient was used to contrast neural activity at different individual levels of novelty. During learning, subjects were asked to memorize 10 geometric patterns requiring the establishment of intra-item associations for memorization. After learning, subjects were asked to recall the items actively via the keyboard. Learning and recall were alternated five times. Delayed recall was scanned about 15 min after the fifth immediate recall condition without subjects having seen the items again. Left-sided anterior hippocampal activity was observed during conditions of initial learning as well as maximum recall. Neural activity during delayed recall did not reveal hippocampal responses and was characterized by a transition of neural activity from occipitoparietal regions to bilateral temporal cortices. We conclude that both lateralization and segregation depend on the specific relational characteristics of the stimuli requiring establishment of intra-item associations for encoding as well as retrieval. The absence of hippocampal activation during delayed recall together with the increase of lateral temporal involvement possibly corresponds with an emerging transition from episodic to long-term memory.

Adult↗