Biomedical subjects

Conny F Schmidt

Publications and source records attributed to Conny F Schmidt.

10 recordsLinked to original sources

PubMed2006

Better memory and neural efficiency in young apolipoprotein E epsilon4 carriers.

The apolipoprotein E (APOE) epsilon4 allele is the major genetic risk factor for Alzheimer's disease, but an APOE effect on memory performance and memory-related neurophysiology in young, healthy subjects is unknown. We found an association of APOE epsilon4 with better episodic memory compared with APOE epsilon2 and epsilon3 in 340 young, healthy persons. Neuroimaging was performed in a subset of 34 memory-matched individuals to study genetic effects on memory-related brain activity independently of differential performance. E4 carriers decreased brain activity over 3 learning runs, whereas epsilon2 and epsilon3 carriers increased activity. This smaller neural investment of epsilon4 carriers into learning reappeared during retrieval: epsilon4 carriers exhibited reduced retrieval-related activity with equal retrieval performance. APOE isoforms had no differential effects on cognitive measures other than memory, brain volumes, and brain activity related to working memory. We suggest that APOE epsilon4 is associated with good episodic memory and an economic use of memory-related neural resources in young, healthy humans.

Adult↗

PubMed2006

Enhanced brain activity may precede the diagnosis of Alzheimer's disease by 30 years.

Presenilin 1 (PSEN1) mutations cause autosomal dominant familial Alzheimer's disease (FAD). PSEN1 mutation carriers undergo the course of cognitive deterioration, which is typical for sporadic Alzheimer's disease but disease onset is earlier and disease progression is faster. Here, we sought to detect signs of FAD in presymptomatic carriers of the PSEN1 mutation (C410Y) by use of a neuropsychological examination, functional MRI during learning and memory tasks and MRI volumetry. We examined five non-demented members of a FAD family and 21 non-related controls. Two of the five family members were carrying the mutation; one was 20 years old and the other 45 years old. The age of clinical manifestation of FAD in the family studied here is approximately 48 years. Neuropsychological assessments suggested subtle problems with episodic memory in the 20-year-old mutation carrier. The middle-aged mutation carrier fulfilled criteria for amnestic mild cognitive impairment. The 20-year-old mutation carrier exhibited increased, while the middle-aged mutation carrier exhibited decreased brain activity compared to controls within memory-related neural networks during episodic learning and retrieval, but not during a working-memory task. The increased memory-related brain activity in the young mutation carrier might reflect a compensatory effort to overcome preclinical neural dysfunction caused by first pathological changes. The activity reductions in the middle-aged mutation carrier might reflect gross neural dysfunction in a more advanced stage of neuropathology. These data suggest that functional neuroimaging along with tasks that challenge specifically those brain areas which are initial targets of Alzheimer's disease pathology may reveal activity alterations on a single-subject level decades before the clinical manifestation of Alzheimer's disease.

Adult↗

PubMed2006

The emotional power of music: how music enhances the feeling of affective pictures.

Music is an intriguing stimulus widely used in movies to increase the emotional experience. However, no brain imaging study has to date examined this enhancement effect using emotional pictures (the modality mostly used in emotion research) and musical excerpts. Therefore, we designed this functional magnetic resonance imaging study to explore how musical stimuli enhance the feeling of affective pictures. In a classical block design carefully controlling for habituation and order effects, we presented fearful and sad pictures (mostly taken from the IAPS) either alone or combined with congruent emotional musical excerpts (classical pieces). Subjective ratings clearly indicated that the emotional experience was markedly increased in the combined relative to the picture condition. Furthermore, using a second-level analysis and regions of interest approach, we observed a clear functional and structural dissociation between the combined and the picture condition. Besides increased activation in brain areas known to be involved in auditory as well as in neutral and emotional visual-auditory integration processes, the combined condition showed increased activation in many structures known to be involved in emotion processing (including for example amygdala, hippocampus, parahippocampus, insula, striatum, medial ventral frontal cortex, cerebellum, fusiform gyrus). In contrast, the picture condition only showed an activation increase in the cognitive part of the prefrontal cortex, mainly in the right dorsolateral prefrontal cortex. Based on these findings, we suggest that emotional pictures evoke a more cognitive mode of emotion perception, whereas congruent presentations of emotional visual and musical stimuli rather automatically evoke strong emotional feelings and experiences.

Acoustic Stimulation↗

PubMed2005

Segregated neural representation of distinct emotion dimensions in the prefrontal cortex-an fMRI study.

Emotions are frequently characterized by distinct dimensions such as valence, intensity, and recognition. However, the exact neural representation of these dimensions in different prefrontal cortical regions remains unclear. One of the problems in revealing prefrontal cortical representation is that the very same regions are also involved in cognitive functions associated with emotion processing. We therefore conducted an fMRI study involving the viewing of emotional pictures (using the International Affective Picture System; IAPS) and controlled for associated cognitive processing like judgment and preceding attention. Functional activation was correlated with subjective post-scanning ratings of valence, intensity, and recognition. Valence significantly correlated with the functional response in ventromedial prefrontal cortex (VMPFC) and dorsolateral prefrontal cortex (DLPFC), intensity with activation in ventrolateral prefrontal cortex (VLPFC) and dorsomedial prefrontal cortex (DMPFC), and recognition with the functional response in perigenual anterior cingulate cortex (PACC). In conclusion, our results indicate segregated neural representation of the different emotion dimensions in different prefrontal cortical regions.

Adult↗

PubMed2005

Face perception is mediated by a distributed cortical network.

The neural system associated with face perception in the human brain was investigated using functional magnetic resonance imaging (fMRI). In contrast to many studies that focused on discreet face-responsive regions, the objective of the current study was to demonstrate that regardless of stimulus format, emotional valence, or task demands, face perception evokes activation in a distributed cortical network. Subjects viewed various stimuli (line drawings of unfamiliar faces and photographs of unfamiliar, famous, and emotional faces) and their phase scrambled versions. A network of face-responsive regions was identified that included the inferior occipital gyrus, fusiform gyrus, superior temporal sulcus, hippocampus, amygdala, inferior frontal gyrus, and orbitofrontal cortex. Although bilateral activation was found in all regions, the response in the right hemisphere was stronger. This hemispheric asymmetry was manifested by larger and more significant clusters of activation and larger number of subjects who showed the effect. A region of interest analysis revealed that while all face stimuli evoked activation within all regions, viewing famous and emotional faces resulted in larger spatial extents of activation and higher amplitudes of the fMRI signal. These results indicate that a mere percept of a face is sufficient to localize activation within the distributed cortical network that mediates the visual analysis of facial identity and expression.

Adult↗

PubMed2005

Implicit associative learning engages the hippocampus and interacts with explicit associative learning.

The hippocampus is crucial for conscious, explicit memory, but whether it is also involved in nonconscious, implicit memory is uncertain. We investigated with functional magnetic resonance imaging whether implicit learning engages the hippocampus and interacts with subsequent explicit learning. The presentation of subliminal faces-written profession pairs for implicit learning was followed by the explicit learning of supraliminal pairs composed of the same faces combined with written professions semantically incongruous to those presented subliminally (experiment 1), semantically congruous professions (experiment 2), or identical professions (experiment 3). We found that implicit face-profession learning interacted with explicit face-profession learning in all experiments, impairing the explicit retrieval of the associations. Hippocampal activity increased during the subliminal presentation of face-profession pairs versus face-nonword pairs and correlated with the later impairment of explicit retrieval. These findings suggest that implicit semantic associative learning engages the hippocampus and influences explicit memory.

Association Learning↗

PubMed2005

Comparison of fMRI activation as measured with gradient- and spin-echo EPI during visual perception.

In this study, we compared fMRI activation measured with gradient- and spin-echo-based fMRI during visual perception of faces, which is mediated by neural activation within a distributed cortical network. With both fMRI techniques, bilateral activation was observed in multiple regions including the inferior occipital gyrus, fusiform gyrus, superior temporal sulcus, amygdala, inferior frontal gyrus, and orbitofrontal cortex. When compared with the gradient-echo sequence, activation measured with the spin-echo sequence was significantly reduced. This decrease was manifested by smaller cluster size, lower statistical significance, smaller amplitude of the fMRI signal, and smaller number of subjects who showed activation in all face-responsive regions. In orbitofrontal cortex, a region prone to susceptibility-related signal dephasing, the spin-echo acquisition considerably restored the signal, but did not reveal stronger activation when compared with the gradient-echo acquisition. Our data indicate that optimized GE sequences that reduce susceptibility artefacts are sufficient to detect activation in regions such as the orbitofrontal cortex.

Adult↗

PubMed2005

Sensitivity-encoded (SENSE) echo planar fMRI at 3T in the medial temporal lobe.

Parallel imaging techniques are useful for fMRI studies in light of the increasing susceptibility effects at high magnetic field strength. Yet, spatially varying noise amplification constitutes a challenge for the application of these techniques. The medial temporal lobe is particularly vulnerable to susceptibility effect with increasingly strong signal reduction. We present two fMRI studies comparing SENSE single-shot (ssh) echo planar imaging (EPI) at acceleration factors of 2.0, 2.4, 2.7, and 3.0 with conventional sshEPI at TE of 22 and 35 ms. Data were acquired during a learning task which activates the medial temporal lobe bilaterally. Susceptibility related image distortion was markedly reduced with increasing SENSE acceleration. Moreover, in the group results, statistical power increased in the whole brain with SENSE compared to conventional imaging and with a TE of 35 ms compared to 22 ms. Higher SENSE acceleration factors further improved image quality and increased statistical power in the occipital lobe and fusiform gyrus, but not in the medial temporal lobe. We therefore conclude that an sshEPI acquisition protocol with a moderate SENSE acceleration factor of R = 2.0 and TE 35 ms is suitable for the detection of medial temporal activation at 3T.

Adult↗

PubMed2005

One month of human memory consolidation enhances retrieval-related hippocampal activity.

We studied the role of the hippocampus in memory retrieval at 1 day and 1 month following associative learning of word pairs. Retrieval-related brain activity was recorded using functional magnetic resonance imaging in 20 healthy students, of which 12 were good learners and eight were poor learners. At the day lag, the poor learners exhibited enhanced neural recruitment in the hippocampus and neocortex to reach a retrieval performance comparable to that of the good learners. Over the 20 subjects, there was a positive correlation between retrieval-related hippocampal activity at the day lag and forgetting over the month retention interval (the greater the activity, the more forgetting). Although the poor learners' retrieval performance declined dramatically from the day to the month lag, the good learners maintained a high retrieval performance, which distinguishes them as good memory consolidators. Their retrieval-related hippocampal and neocortical activity increased from the day to the month lag. This increase was observed both when retrieval performance was matched between the day and the month lag and when the learning procedure for information retrieved at the day and the month lag was matched. This activity increase in the task-specialized neural network from the day lag to the month lag may reflect an increase in task demands or the proliferation of hippocampal-neocortical memory traces during memory consolidation as suggested by the multiple trace theory.

Adult↗

PubMed2005

Effects of memory consolidation on human hippocampal activity during retrieval.

Day-to-day memories undergo transformation from short-term to long-term storage, a process called memory consolidation. Animal studies showed that memory consolidation requires protein synthesis and the growth of new hippocampal synapses within 24 h. To test for effects of memory consolidation in the human, we examined brain activation during the retrieval of information at 10 min and at 24 h following learning using functional magnetic resonance imaging (fMRI), an indirect measure of synaptic activity. Learning instructions were adjusted to yield a comparable retrieval quantity and retrieval quality at 10 min and 24 h after learning. The left hippocampal formation exhibited enhanced activity during the retrieval at the 24 h lag compared to the retrieval at the 10 min lag. Moreover, the activity in the left anterior hippocampal formation showed stronger correlations with retrieval quantity and retrieval quality at the 24 h lag than at the 10 min lag. This suggests that the relation between left anterior hippocampal activity and retrieval success became closer as consolidation progressed. These fMRI results in the human hippocampal formation may correspond to the neurobiological results in the animal hippocampal formation of a strengthening and growth of synaptic connections within 24 h.

Adult↗