Biomedical subjects

A A T S Reinders

Publications and source records attributed to A A T S Reinders.

5 recordsLinked to original sources

PubMed2006

Detecting fearful and neutral faces: BOLD latency differences in amygdala-hippocampal junction.

Evolutionary survival and procreation are augmented if an individual organism quickly detects environmental threats and rapidly initiates defensive behavioral reactions. Thus, facial emotions signaling a potential threat, e.g., fear or anger, should be perceived rapidly and automatically, possibly through a subcortical processing route which includes the amygdala. Using event-related functional magnetic resonance imaging (fMRI), we investigated the time course of the response in the amygdala to neutral and fearful faces, which appear from dynamically decreasing random visual noise. We aimed to detect differences of the amygdala response between fearful and neutral faces by estimating the latency of the blood oxygenation level-dependent (BOLD) response. We found that bilateral amygdala-hippocampal junction activation occurred earlier for fearful than for neutral faces. Our findings support the theory of a dual route architecture in which the subcortical thalamic-hippocampal-amygdala route serves fast preconscious threat perception.

Amygdala↗

PubMed2005

The robustness of perception.

The natural environment around us, which is often crowded, cluttered or even foggy, is subject to a dynamically changing composition of objects and events. The human brain is continuously perceiving, recognizing and evaluating this dynamic scene composition. If the perception of degraded visual objects is important, e.g. in the case of potential threat stimuli, the brain needs to be more sensitive in detecting these objects from the natural environment. It is therefore hypothesized that reacting to the dynamically changing environment involves a robust and quick processing of salient information, which can be either with or without conscious awareness. We investigated the dynamics and robustness of perception using pictures of three salience levels, i.e. fearful faces (most salient), neutral faces (salient) and houses (nonsalient), which appear from dynamically decreasing random visual noise. Stimuli were matched for luminance, contrast, brightness and spatial frequency information. Reaction times show a significantly earlier response for faces than for houses. Fearful faces were significantly more quickly detected than neutral faces. The neural correlates sustaining robust perception were investigated with event-related functional magnetic resonance imaging (fMRI). The amygdala showed a significant perception-related response for faces, as compared to houses, that was further enhanced for fearful faces as compared to neutral faces. Our data indicate that emotionally salient information processing is (i) mediated by the amygdala and (ii) more robust than for nonsalient stimuli as it shows a significantly lower perceptual threshold.

Adolescent↗

PubMed2003

One brain, two selves.

Having a sense of self is an explicit and high-level functional specialization of the human brain. The anatomical localization of self-awareness and the brain mechanisms involved in consciousness were investigated by functional neuroimaging different emotional mental states of core consciousness in patients with Multiple Personality Disorder (i.e., Dissociative Identity Disorder (DID)). We demonstrate specific changes in localized brain activity consistent with their ability to generate at least two distinct mental states of self-awareness, each with its own access to autobiographical trauma-related memory. Our findings reveal the existence of different regional cerebral blood flow patterns for different senses of self. We present evidence for the medial prefrontal cortex (MPFC) and the posterior associative cortices to have an integral role in conscious experience.

Adult↗

PubMed2002

Iterative versus filtered backprojection reconstruction for statistical parametric mapping of PET activation measurements: a comparative case study.

The significance of task-induced cerebral blood flow responses, assessed using statistical parametric mapping, depends, among other things, on the signal-to-noise ratio (SNR) of these responses. Generally, positron emission tomography sinograms of H(2)(15)O activation studies are reconstructed using filtered backprojection (FBP). Alternatively, the acquired data can be reconstructed using an iterative reconstruction procedure. It has been demonstrated that the application of iterative reconstruction methods improves image SNR as compared with FBP. The aim of this study was to compare FBP with iterative reconstruction, to assess the statistical power of H(2)(15)O-PET activation studies using statistical parametric mapping. For this case study, PET data originating from a bimanual motor task were reconstructed using both FBP and maximum likelihood expectation maximization (ML-EM), an iterative algorithm. Both resulting data sets were statistically analyzed using statistical parametric mapping. It was found, with this dataset, that the statistical analysis of the iteratively reconstructed data confirm the a priori expected physiological response. In addition, increased Z scores were obtained in the iteratively reconstructed data. In particular, for the expected task-related response, activation of the posterior border of the left angular gyrus, the Z score increased from 3.00 to 3.96. Furthermore, the number of statistically significant clusters doubled while their volume increased by more than 50%. In conclusion, iterative reconstruction has the potential to increase the statistical power in H(2)(15)O-PET activation studies as compared with FBP reconstruction.

Brain Mapping↗

PubMed2002

Interscan displacement-induced variance in PET activation data is excluded by a scan-specific attenuation correction.

In PET activation studies, linear changes in regional cerebral blood flow may be caused by subject interscan displacements rather than by changes in cognitive state. The aim of this study was to investigate the impact of these artifacts and to assess whether they can be removed by applying a scan-specific calculated attenuation correction (CAC) instead of the default measured attenuation correction (MAC). Two independent data sets were analyzed, one with large (data I) and one with small (data II) interscan displacements. After attenuation correction (CAC or MAC), data were analyzed using SPM99. Interscan displacement parameters (IDP), obtained during scan realignment, were included as additional regressors in the General Linear Model and their impact was assessed by variance statistics revealing the affected brain volume. For data I, this volume reduced dramatically from 579 to 12 cm(3) (approximately 50-fold) at P(uncorr) </= 0.001 and from 100 to 0 cm(3) at P(corr) </= 0.05 when CAC was applied instead of MAC. Surprisingly, for data II, applying CAC instead of MAC still resulted in a substantial (approximately 10-fold) reduction of the affected volume from 23 to 2 cm(3) at P(uncorr) </= 0.001. We conclude that interscan displacement-induced variance can be prevented by applying a (realigned attenuation correction scan (e.g., CAC). With MAC data, introducing IDP covariates is not an alternative since they model only this variance. Even in data with minor interscan displacements, applying a (realigned attenuation correction method (e.g., CAC) is superior to a nonaligned MAC with IDP covariates.

Adult↗