Biology subjects

Bunzeck, N.

Publications and source records attributed to Bunzeck, N..

3 recordsLinked to original sources

bioRxiv2018

Age-related impairment of semantic integration into long-term memory is related to theta-alpha and low beta oscillations

Long-term memory can improve when incoming information is congruent with known semantic information. This so-called congruence effect has widely been shown in younger adults but age-related changes and neural mechanisms remain unclear. Here, congruence improved recognition memory in younger and older adults (i.e. congruency effect), but - importantly - this effect decreased with age. Electroencephalography data show that, in both groups, congruence led to widespread differences in event-related potentials (ERPs) and alpha-beta oscillations (8-30 Hz), known to support semantic processing. Importantly, these ERP differences predicted increases in memory performance, especially for congruent items. Finally, age-related differences in memory were accompanied by a positive ERP and later decrease in theta-alpha (5-13 Hz) during encoding, which were greater in the younger group. Together, although semantic congruence generally increases long-term memory, the effect is less pronounced in the elderly. At the neural level, theta-alpha oscillations, previously linked to memory and attentional processes, provide a mechanistic explanation for such an age-related effect.

neuroscience↗

bioRxiv2018

Dopamine is a double-edged sword: Enhancing memory retrieval performance at the expense of metacognition

While memory encoding and consolidation processes have been linked with dopaminergic signaling for a long time, the role of dopamine in episodic memory retrieval remained mostly unexplored. Based on previous observations of striatal activity during memory retrieval, we used pharmacological fMRI to investigate the effects of dopamine on retrieval performance and metacognitive memory confidence in healthy humans. Dopaminergic modulation by the D2 antagonist haloperidol administered acutely during the retrieval phase improved recognition accuracy of previously learned pictures significantly and was associated with increased activity in the SN/VTA, locus coeruleus, hippocampus and amygdala during retrieval. In contrast, confidence for new-decisions was impaired by unsystematically increased activity of the striatum across confidence levels and restricted range of responsiveness in frontostriatal networks under haloperidol. These findings offer new insights into the mechanisms underlying memory retrieval and metacognition and provide a broader perspective on the presence of memory problems in dopamine-related diseases and the treatment of memory disorders.

neuroscience↗

bioRxiv2018

Altered cingulate and substantia nigra/ventral tegmental activation to novelty and emotional salience in antipsychotic naive first episode psychosis patients

Abnormal salience processing has been suggested to contribute to the formation of positive psychotic symptoms in schizophrenia and related conditions. Previous research utilising reward learning or anticipation paradigms has demonstrated cortical and subcortical abnormalities in people with psychosis, specifically in the prefrontal cortex, the dopaminergic midbrain and the striatum. In these paradigms, reward prediction errors attribute motivational salience to stimuli. However, little is known about possible abnormalities across different forms of salience processing in psychosis patients, and whether any such abnormalities involve the dopaminergic midbrain. The aim of our study was, therefore, to investigate possible alterations in psychosis in neural activity in response to various forms of salience: novelty, negative emotion, targetness (task-driven salience) and rareness/deviance. We studied 14 antipsychotic naive participants with first episode psychosis, and 37 healthy volunteers. During fMRI scanning, participants performed a visual oddball task containing these four forms of salience. Psychosis patients showed abnormally reduced signalling in the substantia nigra/ventral tegmental area (SN/VTA) for novelty, negative emotional salience and targetness; reduced striatal and occipital (lingual gyrus) signalling to novelty and negative emotional salience, reduced signalling in the amygdala, anterior cingulate cortex and parahippocamal gyrus to negative emotional salience, and reduced cerebellar signalling to novelty and negative emotional salience. Our results indicate alterations of several forms of salience processing in patients with psychosis in the midbrain SN/VTA, with additional subcortical and cortical regions also showing alterations in salience signalling, the exact pattern of alterations depending on the form of salience in question.

neuroscience↗