Biomedical subjects

Erich Seifritz

Publications and source records attributed to Erich Seifritz.

28 records · Page 2Linked to original sources

PubMed2003

Sustained blood oxygenation and volume response to repetition rate-modulated sound in human auditory cortex.

The blood oxygen level-dependent (BOLD) signal time course in the auditory cortex is characterized by two components, an initial transient peak and a subsequent sustained plateau with smaller amplitude. Because the T(2)(*) signal detected by functional magnetic resonance imaging (fMRI) depends on at least two counteracting factors, blood oxygenation and volume, we examined whether the reduction in the sustained BOLD signal results from decreased levels of oxygenation or from increased levels of blood volume. We used conventional fMRI to quantify the BOLD signal and fMRI in combination with superparamagnetic contrast agent to quantify blood volume and employed repetition rate-modulated sounds in a silent background to manipulate the response amplitude in the auditory cortex. In the BOLD signal, the initial peak reached 3.3% with pulsed sound and 1.9% with continuous sound, whereas the sustained BOLD signal fell to 2.2% with pulsed sound and to 0.5% with continuous sound, respectively. The repetition rate-dependent reduction in the sustained BOLD amplitude was accompanied by concordant changes in sustained blood volume levels, which, compared to silence, increased by approximately 30% with pulsed and by approximately 10% with continuous sound. Thus, our data suggest that the reduced amplitude of the sustained BOLD signal reflects stimulus-dependent modulation of blood oxygenation rather than blood volume-related effects.

Acoustic Stimulation↗

PubMed2002

Neural processing of auditory looming in the human brain.

Acoustic intensity change, along with interaural, spectral, and reverberation information, is an important cue for the perception of auditory motion. Approaching sound sources produce increases in intensity, and receding sound sources produce corresponding decreases. Human listeners typically overestimate increasing compared to equivalent decreasing sound intensity and underestimate the time to contact of approaching sound sources. These characteristics could provide a selective advantage by increasing the margin of safety for response to looming objects. Here, we used dynamic intensity and functional magnetic resonance imaging to examine the neural underpinnings of the perceptual priority for rising intensity. We found that, consistent with activation by horizontal and vertical auditory apparent motion paradigms, rising and falling intensity activated the right temporal plane more than constant intensity. Rising compared to falling intensity activated a distributed neural network subserving space recognition, auditory motion perception, and attention and comprising the superior temporal sulci and the middle temporal gyri, the right temporoparietal junction, the right motor and premotor cortices, the left cerebellar cortex, and a circumscribed region in the midbrain. This anisotropic processing of acoustic intensity change may reflect the salience of rising intensity produced by looming sources in natural environments.

Adult↗

PubMed2002

Spatiotemporal pattern of neural processing in the human auditory cortex.

The principles that the auditory cortex uses to decipher a stream of acoustic information have remained elusive. Neural responses in the animal auditory cortex can be broadly classified into transient and sustained activity. We examined the existence of similar principles in the human brain. Sound-evoked, blood oxygen level-dependent signal response was decomposed temporally into independent transient and sustained constituents, which predominated in different portions-core and belt-of the auditory cortex. Converging with unit recordings, our data suggest that this spatiotemporal pattern in the auditory cortex may represent a fundamental principle of analyzing sound information.

Acoustic Stimulation↗

PubMed2002

Skill learning in patients with moderate Alzheimer's disease: a prospective pilot-study of waltz-lessons.

The authors report the effect of a 12-day prospective, blinded dance-learning trial in 5 patients with moderate Alzheimer's disease (AD) and 5 age-matched depressed patients. Patients with AD showed a significant effect in procedural learning whereas depressed patients did not. These findings suggest potential implications for therapeutic interventions in patients with moderate AD.

Aged↗

PubMed2002

Spatial independent component analysis of functional MRI time-series: to what extent do results depend on the algorithm used?

Independent component analysis (ICA) has been successfully employed to decompose functional MRI (fMRI) time-series into sets of activation maps and associated time-courses. Several ICA algorithms have been proposed in the neural network literature. Applied to fMRI, these algorithms might lead to different spatial or temporal readouts of brain activation. We compared the two ICA algorithms that have been used so far for spatial ICA (sICA) of fMRI time-series: the Infomax (Bell and Sejnowski [1995]: Neural Comput 7:1004-1034) and the Fixed-Point (Hyvärinen [1999]: Adv Neural Inf Proc Syst 10:273-279) algorithms. We evaluated the Infomax- and Fixed Point-based sICA decompositions of simulated motor, and real motor and visual activation fMRI time-series using an ensemble of measures. Log-likelihood (McKeown et al. [1998]: Hum Brain Mapp 6:160-188) was used as a measure of how significantly the estimated independent sources fit the statistical structure of the data; receiver operating characteristics (ROC) and linear correlation analyses were used to evaluate the algorithms' accuracy of estimating the spatial layout and the temporal dynamics of simulated and real activations; cluster sizing calculations and an estimation of a residual gaussian noise term within the components were used to examine the anatomic structure of ICA components and for the assessment of noise reduction capabilities. Whereas both algorithms produced highly accurate results, the Fixed-Point outperformed the Infomax in terms of spatial and temporal accuracy as long as inferential statistics were employed as benchmarks. Conversely, the Infomax sICA was superior in terms of global estimation of the ICA model and noise reduction capabilities. Because of its adaptive nature, the Infomax approach appears to be better suited to investigate activation phenomena that are not predictable or adequately modelled by inferential techniques.

Adult↗

PubMed2002

fMRI of the auditory cortex in patients with unilateral carotid artery steno-occlusive disease.

PURPOSE: To examine whether an internal carotid artery (ICA) steno-occlusive disease leads to a reduced blood oxygenation level dependent (BOLD)-signal change due to a decreased vasodilatory reserve capacity. MATERIALS AND METHODS: Patients suffering from unilateral ICA stenosis or occlusion were examined using functional magnetic resonance imaging (fMRI) of the auditory cortex with a bilateral stimulation applying a pulsed 1000 Hz sine-tone. RESULTS: Compared to control subjects, who showed symmetric bilateral BOLD-responses within the auditory cortex, the ICA patients revealed either a normal bilateral cortical activation pattern or a reduced cortical activation on the steno-occluded side. This latter decrease of BOLD-signal change might indicate a depressed vasomotor reserve capacity. The observed coincidence between this asymmetric reduction in BOLD-signal and ischemic borderzone lesions on the affected side in this subgroup of patients strongly supports this assumption. CONCLUSION: This study shows that fMRI of the auditory cortex appears to have clinical merit in the workup of cerebrovascular conditions.

Acoustic Stimulation↗

PubMed2002

New aspects in the treatment of heroin dependence with special reference to neurobiological aspects.

The Swiss trials on medical prescription of injectable diacetylmorphine (pharmaceutical heroin) for "severe" heroin dependence provoked very controversial commentaries. Despite methodological shortcomings, the evaluation of the Swiss heroin trials yielded some interesting findings. Study participants showed substantial improvements in health and well-being and noticeable declines in illicit drug use and criminal activities. Heroin prescription may thus be helpful for some of those who continue to regularly use illicit heroin while maintained on methadone or who refuse other available treatment options. However, research-based evidence suggests that the intravenous (IV) application of heroin under medical supervision may have untoward side effects. Recent studies have shown that heroin injections produce transient, but significant decreases in systemic and cortical oxygenation most likely secondary to respiratory depression. Among others, these effects are the subject of ongoing studies.

Adult↗

PubMed2002

Amplitopicity of the human auditory cortex: an fMRI study.

Whereas specialized frequency-encoding patterns in the human auditory cortex are generally accepted, termed tonotopicity, a similar principle of intensity encoding--amplitopicity--is debated controversially. This functional magnetic resonance imaging study describes the relationship of the activation volume and the spatial distribution of activated clusters under different sound pressure levels (SPL) across the temporal plane including the transverse temporal gyrus (TTG). Nine healthy subjects with no hearing deficiencies were investigated using an echo-planar imaging technique at 1.5 T. A boxcar stimulation paradigm was applied with a 5-Hz pulsed sine tone of 1000 Hz frequency at three SPLs of 70, 82, and 90 dB. Linear cross-correlation analysis (correlation coefficient > 0.3 corresponding to P < 0.08) of the functional data set revealed bilateral BOLD response within the auditory cortex of the nine subjects with moderate increase of activation volume for higher sound pressure levels. With increasing sound pressure a two-dimensional drift of cortical activation was observed (a) from the ventral to the dorsal edge and (b) from lateral to medial parts of TTG. This latero-medial drift therefore mimics the well-accepted principle of tonotopy for frequency-encoding neurons. This study demonstrates the existence of an amplitopic pattern of intensity-encoding neuronal clusters that in part resembles the tonotopic distribution of frequency-encoding neurons. This finding has to be integrated into the understanding of the auditory organization for the interpretation of higher auditory functions such as sound perception or speech.

Acoustic Stimulation↗

PubMedDate not supplied

Interactive computer-training as a therapeutic tool in Alzheimer's disease.

The current study sought to evaluate a novel kind of interactive computer-based cognitive training (ICT) in Alzheimer's disease (AD). AD patients (N = 9), age- and gender-matched patients with a major depressive episode (N = 9), and healthy control subjects (N = 10) were trained to use an ICT program that relates to activities of daily living (ADL). Digital photographs of a shopping route were implemented in a close-to-reality simulation on a computer touch-screen. The task was to find a predefined shopping route, to buy three items, and to answer correctly 10 multiple-choice questions addressing knowledge related to the virtual tasks. Training performance was rated using the number of mistakes (wrong way), time needed for the tasks, number of correct multiple-choice answers, and of repeat of instruction. Compared to normal controls and depressed patients, AD patients performed significantly worse with regard to all variables. Within a 4-week training period including 12 sessions, however, substantial training gains were observed, including a significant reduction of mistakes. Training effects were sustained until follow-up 3 weeks later. The performance of the depressed patients and the normal controls improved as well, with no difference between the two groups. Self-reported effects revealed that the training was well perceived. Thus, the task performance of AD patients improved substantially and subjects appeared to have liked this approach to ICT. New interactive media, therefore, may yield interesting opportunities for rehabilitation and (psycho)therapeutic interventions.

Activities of Daily Living↗

PubMedDate not supplied

Red wine ingredient resveratrol protects from beta-amyloid neurotoxicity.

BACKGROUND: beta-Amyloid peptide (Abeta), a neutrotoxic substance, has been implicated to a great degree in cell death during the course of AD. Resveratrol, a natural polyphenol mainly found in red wine, has been shown to be cardioprotective and chemoprotective. Since a moderate wine intake correlates with a lower risk for Alzheimer disease (AD), an additional neuroprotective effect has been postulated for resveratrol. OBJECTIVE: The present study aimed at elucidating the possible neuroprotective effects of resveratrol against Abeta-induced neurotoxicity. METHODS: The neuroprotective capacity against Abeta-related oxidative stress was studied in a cell culture model suitable for studying such potentially neuroprotective substances. RESULTS: Resveratrol maintains cell viability and exerts an anti-oxidative action by enhancing the intracellular free-radical scavenger glutathione. CONCLUSION: Our findings suggest that red wine may be neuroprotective through the actions of resveratrol.

Alzheimer Disease↗