Biomedical subjects

Arthur P Wunderlich

Publications and source records attributed to Arthur P Wunderlich.

6 recordsLinked to original sources

PubMed2003

No hypofrontality, but absence of prefrontal lateralization comparing verbal and spatial working memory in schizophrenia.

Hypofrontality and decreased lateralization have been two major, albeit controversial, results from functional neuroimaging studies of schizophrenia. We used fMRI to study cortical activation during a verbal and spatial working memory (WM) task (2-back) in 15 inpatients acutely ill with schizophrenia and 15 matched control subjects. We hypothesized (i) hypofrontality in patients in both tasks and (ii) decreased lateralization of prefrontal activation in patients under the assumption that, in controls, left prefrontal cortex (PFC) is engaged preferentially in the verbal task (verbal domain dominance) and the right prefrontal cortex is engaged preferentially in the spatial task (spatial domain dominance). Our results showed no significant differences in frontal activation between controls and patients, i.e. no hypofrontality in patients, even at a very liberal threshold (p<0.01). This may be explained by the fact that nearly all patients studied received atypical neuroleptics. Nonetheless, we found evidence for more subtle, domain-related prefrontal dysfunction. Whereas controls showed verbal WM domain dominance in left inferior frontal cortex and spatial WM domain dominance in right prefrontal cortex, these domain dominance effects were absent in the patient group, i.e. there were no lateralization effects. Finally, only patients showed an inverse correlation between performance and right prefrontal activation in verbal WM. We conclude that the finding of hypofrontality may depend on the medication of the patients and that there is prefrontal dysfunction even in the absence of hypofrontality.

Adult↗

PubMed2003

Emotional context modulates subsequent memory effect.

Emotions have been shown to modulate memory processes. However, the neuronal substrate underlying these modulatory effects is largely unknown. Using event-related functional magnetic resonance imaging (fMRI), we investigated whether the context of emotional encoding modulates brain activation predictive for subsequent recall of emotionally neutral material. While inferior frontal activation predicted recall in general, our data show that in a positive encoding context, recall was predicted by activation of right anterior parahippocampal and extrastriate visual brain areas, whereas in a negative encoding context, recall was predicted by activation of the amygdala. Thus, we could demonstrate that successful episodic encoding is differentially modulated by emotional context. These results contribute to the understanding of the interaction of emotion and cognition and moreover are of general relevance for studies of episodic memory.

Adult↗

PubMed2002

Cultural objects modulate reward circuitry.

Using event-related fMRI we investigated the rewarding properties of cultural objects (cars) signaling wealth and social dominance. It has been shown recently that reward mechanisms are involved in the regulation of social relations like dominance and social rank. Based on evolutionary considerations we hypothesized that sports cars in contrast to other categories of cars, e.g. limousines and small cars, are strong social reinforcers and would modulate the dopaminergic reward circuitry. Twelve healthy male subjects were studied with fMRI while viewing photographs of different car classes followed by an attractivity rating. Behaviorally sports cars were rated significantly more attractive than limousines and small cars. Our fMRI results revealed significantly more activation in ventral striatum, orbitofrontal cortex, anterior cingulate and occipital regions for sports cars in contrast to other categories of cars. We could thus demonstrate that artificial cultural objects associated with wealth and social dominance elicit activation in reward-related brain areas.

Adult↗

PubMed2002

Subjective memory complaints: objective neural markers in patients with Alzheimer's disease and major depressive disorder.

Patients with probable Alzheimer's disease and depressive patients frequently present with subjective memory complaints. Objective distinction of underlying neuronal substrate malfunction and early cross-sectional differential diagnosis have been elusive thus far. We used repetitive learning and free recall of abstract geometric patterns during functional magnetic resonance imaging to assess episodic memory in older subjects (ages 56-64 years) who sought first-time medical attention with subjective memory complaints and were diagnosed with probable Alzheimer's disease (NINCDS-ADRDA criteria; ages 51-67 years) or major depressive disorder (DSM-IV; ages 50-65 years). Contrasting healthy seniors or depressive patients with Alzheimer's disease patients revealed superiority of hippocampal activation. Contrasting Alzheimer's disease patients with seniors showed bilateral prefrontal activity as a correlate of futile compensation of episodic memory failure. Contrasting patients who had major depressive disorder with seniors or patients who had Alzheimer's disease showed bilateral activation of the orbitofrontal cortex and the anterior cingulate. Subjective memory complaints may be classified objectively and very early with functional magnetic resonance imaging of episodic memory in groups of patients with Alzheimer's disease and depressive syndrome. This may facilitate drug trials with evaluation of specific treatments, but further studies will be needed to establish the differential diagnosis for the individual patient.

Aged↗

PubMed2002

Spatial congruence of neuronavigated transcranial magnetic stimulation and functional neuroimaging.

OBJECTIVES: Transcranial magnetic stimulation (TMS) is progressively gaining relevance as a tool in cognitive neuroscience and clinical research. However, most studies in this field do not consider individual anatomy. Neuronavigational devices allow to guide the coil to a specific cortical area, predetermined by functional magnetic resonance imaging (fMRI). Therefore, it is crucial to know whether the area of a certain function as identified by fMRI corresponds to the area where the TMS should be placed in order to influence this function. METHODS: We investigated the spatial relation between the cortical area activated by a motor task in fMRI and the area of magnetically evoked motor potentials (MEP) in 8 subjects, using a spacing of 5x5 mm. A neuronavigational system was adapted for coil positioning and for the registration of the stimulation coordinates. RESULTS: A spatial divergence of the centers of gravity from fMRI and MEP was found with a mean distance of about 10 mm, with the MEP centers being, by a mean derivation of 7.5 mm, consistently anterior to the center of fMRI activation. However, regarding MEP areas and fMRI activities, a large overlap was found for stimulation intensities of both 110 and 120% motor threshold. CONCLUSIONS: The combination of fMRI and neuronavigated TMS is useful for non-invasive investigation of individual cortical functions predetermined by fMRI. Whereas both are spatially by and large congruent, discrepencies in the exact spatial relation between MEP and fMRI areas should be considered and further studied.

Adult↗

PubMedDate not supplied

Variability in memory performance in aged healthy individuals: an fMRI study.

Episodic memory performance varies in older subjects but underlying biological correlates remain as yet ambiguous. We investigated episodic memory in healthy older individuals (n=24; mean age: 64.4+/-6.7 years) without subjective memory complaints or objective cognitive impairment. Episodic memory was assessed with repetitive learning and recall of abstract geometric patterns during fMRI. Group analysis of brain activity during initial learning and maximum recall revealed hippocampal activation. Correlation analysis of brain activation and task performance demonstrated significant hippocampal activity during initial learning and maximum recall in a success-dependent manner. Neither age nor gray matter densities correlated with hippocampal activation. Functional imaging of episodic memory thus permits to detect objectively variability in hippocampal recruitment in healthy aged individuals without subjective memory complaints. Correlation analysis of brain activation and performance during an episodic memory task may be used to determine and follow-up hippocampal malfunction in a very sensitive manner.

Aged↗