COMT Val158Met genotype is associated with fluctuations in working memory performance: converging evidence from behavioural and single-trial P3b measures.

Intra-subject variability in reaction times (ISV) is a promising endophenotype for several psychiatric conditions, but its neural underpinnings are not yet established. Converging evidence from neuroimaging, molecular genetics, and psychopharmacology suggests that ISV could index catecholaminergically-mediated neural noise. The fine-grained temporal resolution of electroencephalography is ideal for investigating ISV, but only if potential neural correlates of ISV can be assessed in single trials. Based on evidence that ISV is associated with dopaminergic functioning, we apply a recently developed method of single-trial P3b analysis to investigate the association of COMT Val(158)Met genotype with measures of ISV on the behavioural and neural levels at different working memory loads. Greater number of Met alleles was associated with poorer and more intra-individually variable performance on the tasks, and greater latency jitter in single-trial P3bs. These converging results at the behavioural and neurophysiological levels confirm previous observations that prefrontal dopamine availability is associated with stability and accuracy of cognitive performance. Together with previous studies, these data imply pleiotropic cognitive effects of COMT genotype.

Emotional faces and the default mode network.

The default-mode network (DMN) of the human brain has become a central topic of cognitive neuroscience research. Although alterations in its resting state activity and in its recruitment during tasks have been reported for several mental and neurodegenerative disorders, its role in emotion processing has received relatively little attention. We investigated brain responses to different categories of emotional faces with functional magnetic resonance imaging (fMRI) and found deactivation in ventromedial prefrontal cortex (VMPFC), posterior cingulate gyrus (PC) and cuneus. This deactivation was modulated by emotional category and was less prominent for happy than for sad faces. These deactivated areas along the midline conformed to areas of the DMN. We also observed emotion-dependent deactivation of the left middle frontal gyrus, which is not a classical component of the DMN. Conversely, several areas in a fronto-parietal network commonly linked with attention were differentially activated by emotion categories. Functional connectivity patterns, as obtained by correlation of activation levels, also varied between emotions. VMPFC, PC or cuneus served as hubs between the DMN-type areas and the fronto-parietal network. These data support recent suggestions that the DMN is not a unitary system but differentiates according to task and even type of stimulus. The emotion-specific differential pattern of DMN deactivation may be explored further in patients with mood disorder, where the quest for biological markers of emotional biases is still ongoing.

Upregulation of emotion areas through neurofeedback with a focus on positive mood.

Real-time functional magnetic resonance imaging can be used to feed back signal changes from the brain to participants such that they can train to modulate activation levels in specific brain areas. Here we present the first study combining up-regulation of brain areas for positive emotions with psychometric measures to assess the effect of successful self-regulation on subsequent mood. We localized brain areas associated with positive emotions through presentation of standardized pictures with positive valence. Participants up-regulated activation levels in their target area during specific periods, alternating with rest. Participants attained reliable self-control of the target area by the last of three seven-minute runs. This training effect was supported by an extensive network outside the targeted brain region, including higher sensory areas, paralimbic and orbitofrontal cortex. Self-control of emotion areas was not accompanied by clear changes in self-reported emotions; trend-level improvements on depression scores were counteracted by increases on measures of fatigue, resulting in no overall mood improvement. It is possible that benefits of self-control of emotion networks may only appear in people who display abnormal emotional homeostasis. The use of only a single, short, training session, overlap between positive and negative emotion networks and aversive reactions to the scanning environment may have prevented the detection of subtle changes in mood.

Neurofeedback: A promising tool for the self-regulation of emotion networks.

Real-time functional magnetic resonance imaging (fMRI) affords the opportunity to explore the feasibility of self-regulation of functional brain networks through neurofeedback. We localised emotion networks individually in thirteen participants using fMRI and trained them to upregulate target areas, including the insula and amygdala. Participants achieved a high degree of control of these networks after a brief training period. We observed activation increases during periods of upregulation of emotion networks in the precuneus and medial prefrontal cortex and, with increasing training success, in the ventral striatum. These findings demonstrate the feasibility of fMRI-based neurofeedback of emotion networks and suggest a possible development into a therapeutic tool.

Do I know you? Insights into memory for faces from brain potentials.

The recognition of faces is central to human social interaction. Recordings of event-related potentials (ERPs) from the brain can shed light on the various processes that occur when a face is recognized and when knowledge related to a specific person is retrieved. ERP contrasts between processing familiar and processing novel faces offer a gateway into investigations of semantic memory for familiar persons. In particular, activity of face recognition units and semantic information units--memory representations of faces and person-related knowledge, respectively--can be indexed by specific ERPs. These potentials thus provide valuable tools for studying the cognitive and neurobiological architecture of person recognition. ERPs have also been found useful for investigating other types of memory for faces. Specifically, important insights have been derived from the study of a category of memory phenomena known as priming. Priming can be revealed in special tests when face recognition is facilitated based on prior experience. Describing the neural processes associated with memory for faces is an exciting focus of research, and future results from this line of inquiry promise to provide further knowledge about face recognition and the various types of memory that can be provoked by a human face.