Personality factors correlate with regional cerebral perfusion

Behavioral activation system modulation on brain activation during appetitive and aversive stimulus processing

The reinforcement sensitivity theory (RST) proposed the behavioral activation system (BAS) as a neurobehavioral system that is dependent on dopamine-irrigated structures and that mediates the individual differences in sensitivity and reactivity to appetitive stimuli associated with BAS-related personality traits. Theoretical developments propose that high BAS sensitivity is associated with both enhanced appetitive stimuli processing and the diminished processing of aversive stimuli. The objective of this study was to analyze how individual differences in BAS functioning were associated with brain activation during erotic and aversive picture processing while subjects were involved in a simple goal-directed task. Forty-five male participants took part in this study. The task activation results confirm the activation of the reward and punishment brain-related structures while viewing erotic and aversive pictures, respectively. The SR scores show a positive correlation with activation of the left lateral prefrontal cortex, the mesial prefrontal cortex and the right occipital cortex while viewing erotic pictures, and a negative correlation with the right lateral prefrontal cortex and the left occipital cortex while viewing aversive pictures. In summary, the SR scores modulate the activity of the cortical areas in the prefrontal and the occipital cortices that are proposed to modulate the BAS and the BIS-FFFS.

Individual sensitivity to pain expectancy is related to differential activation of the hippocampus and amygdala

Anxiety arising during pain expectancy can modulate the subjective experience of pain. However, individuals differ in their sensitivity to pain expectancy. The amygdale and hippocampus were proposed to mediate the behavioral response to aversive stimuli. However, their differential role in mediating anxiety-related individual differences is not clear. Using fMRI, we investigated brain activity during expectancy to cued or uncued thermal pain applied to the wrist. Following each stimulation participants rated the intensity of the painful experience. Activations in the amygdala and hippocampus were examined with respect to individual differences in harm avoidance (HA) personality trait, and individual sensitivity to expectancy, (i.e. response to cued vs. uncued painful stimuli). Only half of the subjects reported on cued pain as being more painful than uncued pain. In addition, we found a different activation profile for the amygdala and hippocampus during pain expectancy and experience. The amygdala was more active during expectancy and this activity was correlated with HA scores. The hippocampal activity was equally increased during both pain expectancy and experience, and correlated with the individual's sensitivity to expectancy. Our findings suggest that the amygdala supports an innate tendency to approach or avoid pain as reflected in HA trait, whereas the hippocampus mediates the effect of context possibly via appraisal of the stimulus value.

Anxiety, cognitive self-evaluation and performance: ERP correlates

The relation between anxiety, cognitive self-evaluation, performance, and electrical brain activity (event-related potentials, ERPs) in a sustained attention task (Go/NoGo; SART) was investigated in 18 participants. No significant correlation was found between reaction times and anxiety (assessed by State and Trait Anxiety Inventory or STAI), and cognitive self-evaluation (assessed by Cognitive Failures Questionnaire or CFQ). N2 (ERP time-window 250-350ms) and P3 (350-650ms) amplitudes were found to be related to anxiety and cognitive self-evaluation. N2 amplitude increased in trait and state high anxious participants, whereas P3 decreased in participants who reported a higher frequency of cognitive failures. Electrophysiological responses revealed that cognitive strategies were probably activated by more anxious and less self-confident individuals in order to be efficient in their performance. As shown by current research, frontal areas and anterior cingulated cortex appear to be particularly involved in this affective-cognitive interaction.

Human fear conditioning and extinction in neuroimaging: a systematic review

Fear conditioning and extinction are basic forms of associative learning that have gained considerable clinical relevance in enhancing our understanding of anxiety disorders and facilitating their treatment. Modern neuroimaging techniques have significantly aided the identification of anatomical structures and networks involved in fear conditioning. On closer inspection, there is considerable variation in methodology and results between studies. This systematic review provides an overview of the current neuroimaging literature on fear conditioning and extinction on healthy subjects, taking into account methodological issues such as the conditioning paradigm.

A Pubmed search, as of December 2008, was performed and supplemented by manual searches of bibliographies of key articles. Two independent reviewers made the final study selection and data extraction. A total of 46 studies on cued fear conditioning and/or extinction on healthy volunteers using positron emission tomography or functional magnetic resonance imaging were reviewed. The influence of specific experimental factors, such as contingency and timing parameters, assessment of conditioned responses, and characteristics of conditioned and unconditioned stimuli, on cerebral activation patterns was examined. Results were summarized descriptively. A network consisting of fear-related brain areas, such as amygdala, insula, and anterior cingulate cortex, is activated independently of design parameters. However, some neuroimaging studies do not report these findings in the presence of methodological heterogeneities. Furthermore, other brain areas are differentially activated, depending on specific design parameters. These include stronger hippocampal activation in trace conditioning and tactile stimulation. Furthermore, tactile unconditioned stimuli enhance activation of pain related, motor, and somatosensory areas.

Differences concerning experimental factors may partly explain the variance between neuroimaging investigations on human fear conditioning and extinction and should, therefore, be taken into serious consideration in the planning and the interpretation of research projects.

States vs. Traits

Hans-Jürgen Eysenck suggested that introverts are characterized by greater cortical arousal or arousability than extraverts. This prediction was tested in several studies that used the electroencephalogram (EEG) to index cortical activity, but the relations between the EEG measures and Extraversion are typically small. Possibly, situational factors that are external to the laboratory may act as nuisance variables and affect cortical activity, thus, mitigating the relation between arousal or arousability and Extraversion. To test this hypothesis, resting EEG was acquired on four occasions of measurement and Extraversion was assessed by questionnaire. A structural equation model (SEM) represented cortical arousal, arousability, and external factors. This analysis suggested that (1) arousal and arousability are independent factors, (2) external factors only marginally contribute to the variance of the EEG measures, and (3) the relations between the EEG measures and Extraversion were insignificant even if external factors were statistically controlled.

Latent state-trait structure of cerebral blood flow in a resting state

Cerebral blood flow (CBF) is an important parameter for the study of brain function. The present paper examines to what extent CBF in a resting state reflects a stable latent trait and to what extent it reflects phasic situational effects. In 38 healthy subjects resting CBF was measured with continuous arterial spin labeling. Data analyses were performed within the methodological framework of latent state-trait theory, which allows the decomposition of the measured variables into temporally stable differences, occasion-specific fluctuations, and measurement errors. For most of the regions of interest, about 70% of the observed variance in resting CBF was determined by individual differences on a latent physiological trait whereas about 20% of the variance was due to occasion-specific influences. Thus, an aggregation across measurement occasions is not necessary in order to yield a stable physiological trait.

Increased cerebral perfusion in adult attention deficit hyperactivity disorder is normalised by stimulant treatment: a non-invasive MRI pilot study

The neurobiological basis for attention deficit hyperactivity disorder (ADHD) has not yet been fully established, although there is a growing body of evidence pointing to functional and structural abnormalities involving the basal ganglia, cerebellum, and regions of frontal grey matter. The purpose of this study was to investigate regional cerebral perfusion in adults with ADHD and age-matched control subjects, and to assess the perfusion response to stimulant treatment in the ADHD group using a non-invasive magnetic resonance perfusion imaging technique. Whole-brain cerebral perfusion images were acquired from nine right-handed male patients with ADHD and eleven age-matched control subjects using a continuous arterial spin labelling (CASL) technique. The ADHD group was assessed once on their normal treatment and once after withdrawing from treatment for at least one week. An automated voxel-based analysis was used to identify regions where the cerebral perfusion differed significantly between the ADHD and control groups, and where the perfusion altered significantly with stimulant treatment. Regional cerebral perfusion was increased in the ADHD group in the left caudate nucleus, frontal and parietal regions. Psychomotor stimulant treatment acted to normalise perfusion in frontal cortex and the caudate nucleus with additional decreases in parietal and parahippocampal regions. These findings highlight the potential sensitivity of non-invasive perfusion MRI techniques like CASL in the evaluation of perfusion differences due to illness and medication treatment, and provide further evidence that persistence of ADHD symptomatology into adulthood is accompanied by abnormalities in frontal and striatal brain regions.

Clinical neuroimaging using arterial spin-labeled perfusion magnetic resonance imaging

The two most common methods for measuring perfusion with MRI are based on dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL). Although clinical experience to date is much more extensive with DSC perfusion MRI, ASL methods offer several advantages. The primary advantages are that completely noninvasive absolute cerebral blood flow (CBF) measurements are possible with relative insensitivity to permeability, and that multiple repeated measurements can be obtained to evaluate one or more interventions or to perform perfusion-based functional MRI. ASL perfusion and perfusion-based functional MRI methods have been applied in many clinical settings, including acute and chronic cerebrovascular disease, CNS neoplasms, epilepsy, aging and development, neurodegenerative disorders, and neuropsychiatric diseases. Recent technical advances have improved the sensitivity of ASL perfusion MRI, and increasing use is expected in the coming years. The present review focuses on ASL perfusion MRI and applications in clinical neuroimaging.