Neural Correlates of Unsuccessful Memory Performance in MCI

People with mild cognitive impairment (MCI) are at an elevated risk of developing Alzheimer’s disease or other forms of dementia. Although the neural correlates of successful memory performance in MCI have been widely investigated, the neural mechanisms involved in unsuccessful memory performance remain unknown. The current study examines the differences between patients suffering from stable amnestic MCI with multiple deficit syndromes and healthy elderly controls in relation to the neural correlates of both successful and unsuccessful encoding and recognition. Forty-six subjects (27 controls, 19 MCI) from the HelMA (Helmholtz Alliance for Mental Health in an Aging Society) completed a comprehensive neuropsychological test battery and participated in an fMRI experiment for associative face-name memory. In patients, the areas of frontal, parietal, and temporal cortices were less involved during unsuccessful encoding and recognition. A temporary dysfunction of the top-down control of frontal or parietal (or both) areas is likely to result in a non-selective propagation of task-related information to memory.

Attenuated prefrontal activation during decision-making under uncertainty in schizophrenia: a multi-center fMRI study

Decisions are called decisions under uncertainty when either prior information is incomplete or the outcomes of the decision are unclear. Alterations in these processes related to decisions under uncertainty have been linked to delusions. In patients with schizophrenia, the underlying neural networks have only rarely been studied. We aimed to disentangle the neural correlates of decision-making and relate them to neuropsychological and psychopathological parameters in a large sample of patients with schizophrenia and healthy subjects. Fifty-seven patients and fifty-seven healthy volunteers from six centers had to either indicate via button-press from which of two bottles red or blue balls were drawn (decision-making under uncertainty condition), or indicate whether eight red balls had been presented (baseline condition) while BOLD signal was measured with fMRI. Patients based their decisions on less conclusive evidence and had decreased activations in the underlying neural network, comprising of medial and lateral frontal as well as parietal areas, as compared to healthy subjects. While current psychopathology was not correlated with brain activation, positive symptoms led to longer decision latencies in patients. These results suggest that decision-making under uncertainty in schizophrenia is affected by a complex interplay of aberrant neural activation. Furthermore, reduced neuropsychological functioning in patients was related to impaired decision-making and task performance was modulated by distinct positive symptoms.

The scent of salience--is there olfactory-trigeminal conditioning in humans?

Pavlovian fear conditioning has been thoroughly studied in the visual, auditory and somatosensory domain, but evidence is scarce with regard to the chemosensory modality. Under the assumption that Pavlovian conditioning relies on the supra-modal mechanism of salience attribution, the present study was set out to attest the existence of chemosensory aversive conditioning in humans as a specific instance of salience attribution. fMRI was performed in 29 healthy subjects during a differential aversive conditioning paradigm. Two odors (rose, vanillin) served as conditioned stimuli (CS), one of which (CS+) was intermittently coupled with intranasally administered CO2. On the neural level, a robust differential response to the CS+ emerged in frontal, temporal, occipito-parietal and subcortical brain regions, including the amygdala. These changes were paralleled by the development of a CS+-specific connectivity profile of the anterior midcingulate cortex (aMCC), which is a key structure for processing salience information in order to guide adaptive response selection. Increased coupling could be found between key nodes of the salience network (anterior insula, neo-cerebellum) and sensorimotor areas, representing putative input and output structures of the aMCC for exerting adaptive motor control. In contrast, behavioral and skin conductance responses did not show significant effects of conditioning, which has been attributed to contingency unawareness. These findings imply substantial similarities of conditioning involving chemosensory and other sensory modalities, and suggest that salience attribution and adaptive control represent a general, modality-independent principle underlying Pavlovian conditioning.

Effects of a CACNA1C genotype on attention networks in healthy individuals

BACKGROUND

Recent genetic studies found the A allele of the variant rs1006737 in the alpha 1C subunit of the L-type voltage-gated calcium channel (CACNA1C) gene to be over-represented in patients with psychosis, including schizophrenia, bipolar disorder and major depressive disorder. In these disorders, attention deficits are among the main cognitive symptoms and have been related to altered neural activity in cerebral attention networks. The particular effect of CACNA1C on neural function, such as attention networks, remains to be elucidated.

METHOD

The current event-related functional magnetic resonance imaging (fMRI) study investigated the effect of the CACNA1C gene on brain activity in 80 subjects while performing a scanner-adapted version of the Attention Network Test (ANT). Three domains of attention were probed simultaneously: alerting, orienting and executive control of attention.

RESULTS

Risk allele carriers showed impaired performance in alerting and orienting in addition to reduced neural activity in the right inferior parietal lobule [Brodmann area (BA) 40] during orienting and in the medial frontal gyrus (BA 8) during executive control of attention. These areas belong to networks that have been related to impaired orienting and executive control mechanisms in neuropsychiatric disorders.

CONCLUSIONS

Our results suggest that CACNA1C plays a role in the development of specific attention deficits in psychiatric disorders by modulation of neural attention networks.

Gender differences in the neural correlates of humor processing: implications for different processing modes

Humor is a complex phenomenon of human social cognition with large inter-individual variability. Gender differences in emotion processing are a common finding in functional neuroimaging studies, and have been documented in behavioral studies of humor, but have received limited attention in functional neuroimaging studies on humor. Using blood oxygenation level dependent (BOLD) contrasts with high-field (3T) functional magnetic resonance imaging (fMR) we investigated 29 healthy subjects (14 female, 15 male) during the processing of humorous cartoons. In women, the ventral system implicated ín detection and appraisal of emotion was activated, including amygdala, insula, and Anterior Cingulate Cortex (ACC). Men showed activation in both the ventral and dorsal processing systems. The results indicate that women process humor though limbic reactivity, involving appraisal of its emotional features, while men apply more evaluative, executive resources to humor processing.

[Experiences in the radiographic contrast medium dimer-X in orbital diagnosis (author's transl)]

Experiments in animals and the employment of the contrast medium in a number of patients showed, that Dimer-X is well tolerated. No negative side effects were observed during the study. Employing only a little quantity of the medium, diluted with distilled water in the ratio of 1:3 or 1:4, good contrast representations are obtainable in the tissue of the orbits. It is completely absorbed within a relatively short period.