Brain imaging and the effects of caffeine and nicotine

Tobacco Smoking Functional Networks: A Whole-Brain Connectome Analysis in 24 539 Individuals

INTRODUCTION

Nicotine addiction, a multifaceted neuropsychiatric disorder, profoundly impacts brain functions through interactions with neural pathways. Despite its significance, the impact of tobacco smoking on the whole-brain functional connectome remains largely unexplored.

AIMS AND METHODS

We conducted a whole-brain analysis on 24 539 adults aged 40 and above from the United Kingdom Biobank cohort. Subjects were categorized into individuals who use nicotine and those who do not use nicotine based on current and chronic tobacco smoking information. Functional connectivity was assessed using resting-state functional magnetic resonance imaging. We employed a network analysis method to assess the systematic effects of tobacco smoking on brain connectome by identifying subnetworks that show nicotine-use-related differences.

RESULTS

Our analyses revealed two nicotine-use-related subnetworks with distinct network structure (permutation p < .001). In the first network, there is a significant decrease in resting-state functional connectivity (rsFC) between the basal ganglia regions (eg, nucleus accumbens) and 73% of the remaining brain regions, emphasizing the central hub role of basal ganglia in addictive smoking behaviors. Additionally, a data-driven subnetwork, mainly involving regions from frontal and occipital lobes, showed reduced rsFC among individuals who use nicotine.

CONCLUSIONS

The results suggest significant alterations in the communication and coordination among the basal ganglia and the broader network of brain regions. The observed changes in rsFC indicate a widespread disruption in the connectivity patterns associated with nicotine use.

IMPLICATIONS

This study identifies rsFC subnetworks related to chronic nicotine use through whole-brain connectome analysis. The findings confirm that widespread alterations in rsFC are centered around hub nodes within the basal ganglia, including bilateral nucleus accumbens, putamen, caudate, and globus pallidus. In addition, our analysis found a clique-forming subnetwork vulnerable to tobacco smoking consisting of regions from the visual, dorsal/ventral attention, and frontoparietal networks.

Acute psilocybin and ketanserin effects on cerebral blood flow: 5-HT2AR neuromodulation in healthy humans

Psilocin, the active metabolite of psilocybin, is a psychedelic and agonist at the serotonin 2A receptor (5-HT2AR) that has shown positive therapeutic effects for brain disorders such as depression. To elucidate the brain effects of psilocybin, we directly compared the acute effects of 5-HT2AR agonist (psilocybin) and antagonist (ketanserin) on cerebral blood flow (CBF) using pseudo-continuous arterial spin labeling magnetic resonance imaging (MRI) in a single-blind, cross-over study in 28 healthy participants. We evaluated associations between plasma psilocin level (PPL) or subjective drug intensity (SDI) and CBF. We also evaluated drug effects on internal carotid artery (ICA) diameter using time-of-flight MRI angiography. PPL and SDI were significantly negatively associated with regional and global CBF (∼11.6% at peak drug effect, p < 0.0001). CBF did not significantly change following ketanserin (2.3%, p = 0.35). Psilocybin induced a significantly greater decrease in CBF compared to ketanserin in the parietal cortex (pFWER < 0.0001). ICA diameter was significantly decreased following psilocybin (10.5%, p < 0.0001) but not ketanserin (-0.02%, p = 0.99). Our data support an asymmetric 5-HT2AR modulatory effect on CBF and provide the first in vivo human evidence that psilocybin constricts the ICA, which has important implications for understanding the neurophysiological mechanisms underlying its acute effects.

Opening the dialogue: A preliminary exploration of hair color, hair cleanliness, light, and motion effects on fNIRS signal quality

INTRODUCTION

Functional near-infrared spectroscopy (fNIRS) is a promising tool for studying brain activity, offering advantages such as portability and affordability. However, challenges in data collection persist due to factors like participant physiology, environmental light, and gross-motor movements, with limited literature on their impact on fNIRS signal quality. This study addresses four potentially influential factors-hair color, hair cleanliness, environmental light, and gross-motor movements-on fNIRS signal quality. Our aim is to raise awareness and offer insights for future fNIRS research.

METHODS

Six participants (4 Females, 2 Males) took part in four different experiments investigating the effects of hair color, hair cleanliness, environmental light, and gross-motor movements on fNIRS signal quality. Participants in Experiment 1, categorized by hair color, completed a finger-tapping task in a between-subjects block design. Signal quality was compared between each hair color. Participants in Experiments 2 and 3 completed a finger-tapping task in a within-subjects block design, with signal quality being compared across hair cleanliness (i.e., five consecutive days without washing the hair) and environmental light (i.e., sunlight, artificial light, no light, etc.), respectively. Experiment 4 assessed three gross-motor movements (i.e., walking, turning and nodding the head) in a within-subjects block design. Motor movements were then compared to resting blocks. Signal quality was evaluated using Scalp Coupling Index (SCI) measurements.

RESULTS

Lighter hair produced better signals than dark hair, while the impact of environmental light remains uncertain. Hair cleanliness showed no significant effects, but gross motor movements notably reduced signal quality.

CONCLUSION

Our results suggest that hair color, environmental light, and gross-motor movements affect fNIRS signal quality while hair cleanliness does not. Nevertheless, future studies with larger sample sizes are warranted to fully understand these effects. To advance future research, comprehensive documentation of participant demographics and lab conditions, along with signal quality analyses, is essential.

Effect of caffeine on hippocampal memory and levels of gene expression in social isolation stress

BACKGROUND

Caffeine (Cf) antagonizes the adenosine receptors and has neuroprotective properties. The effect of Cf has been seen on stress-induced deficits of cognitive. In this study, we have investigated the effect of Cf on learning and memory functions induced by social isolation (SI) stress.

MATERIALS AND METHODS

In the present study, 21-day-old Wistar albino male rats (n = 28) were divided into four groups: the control (C), the SI, the Cf, and the social isolation + caffeine (SICf). Cf (0.3 g/L) was added to the drinking water of the experimental animals for 4 weeks. The learning and memory functions were assessed using the Morris Water Maze Test (MWMT). Following, was performed histopathological evaluation and determined hippocampal gene expression levels by RT-qPCR.

RESULTS

According to MWMT findings, the time spent in the quadrant where the platform removed was decreased in the SI group compared with the C (p < 0.05). Histological evaluation showed morphological changes in SI by irregular appearance, cellular edema, and dark pycnotic appearance of nuclei in some neurons. However, it was observed that the histological structure of most of the neurons in the SICf group was similar to the C and Cf groups. Hippocampal SNAP25 expression was decreased in the Cf and SICf groups than in the C group (p < 0.05). The GFAP expression was increased in the SICf group than in the C group (p < 0.05). NR2A increased in the SI and SICf groups compared with C and Cf groups (p < 0.05). NR2B expression decreased in the Cf group compared with C and SI groups (p < 0.05).

CONCLUSIONS

SI impaired spatial memory and causes morphological changes in adolescent rats, but this effect of isolation was not seen in Cf-treated animals. The effects of SI on NR2A, Cf on NR2B, and SNAP25 are remarkable. Here, we propose that the impaired effect of SI on spatial memory may be mediated by NR2A, but further studies are needed to explain this effect.

Impact of cannabis use on brain metabolism using 31P and 1H magnetic resonance spectroscopy

PURPOSE

This prospective cross-sectional study investigated the influence of regular cannabis use on brain metabolism in young cannabis users by using combined proton and phosphorus magnetic resonance spectroscopy.

METHODS

The study was performed in 45 young cannabis users aged 18-30, who had been using cannabis on a regular basis over a period of at least 2 years and in 47 age-matched controls. We acquired 31P MRS data in different brain regions at 3T with a double-resonant 1H/31P head coil, anatomic images, and 1H MRS data with a standard 20-channel 1H head coil. Absolute concentration values of proton metabolites were obtained via calibration from tissue water as an internal reference, whereas a standard solution of 75 mmol/l KH2PO4 was used as an external reference for the calibration of phosphorus signals.

RESULTS

We found an overall but not statistically significant lower concentration level of several proton and phosphorus metabolites in cannabis users compared to non-users. In particular, energy-related phosphates such as adenosine triphosphate (ATP) and inorganic phosphate (Pi) were reduced in all regions under investigation. Phosphocreatine (PCr) showed lowered values mainly in the left basal ganglia and the left frontal white matter.

CONCLUSION

The results suggest that the increased risk of functional brain disorders observed in long-term cannabis users could be caused by an impairment of the energy metabolism of the brain, but this needs to be verified in future studies.

Relieving Chronic Musculoskeletal Pain in Older Adults Using Transcranial Direct Current Stimulation: Effects on Pain Intensity, Quality, and Pain-Related Outcomes

Introduction

Chronic pain is a significant health problem and is particularly prevalent amongst the elderly. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has been proposed to reduce chronic pain. The aim of this study was to evaluate and compare the efficacy of active and sham tDCS in reducing pain in older individuals living with chronic musculoskeletal pain.

Materials and Methods

Twenty-four older individuals (mean age: 68 ± 7 years) suffering from chronic musculoskeletal pain were randomized to receive either anodal tDCS over the contralateral motor cortex (2 mA, 20 min; n = 12) or sham tDCS (20 min; n = 12) for five consecutive days. Pain logbooks were used to measure pain intensity. Questionnaires (McGill Pain Questionnaire, Brief Pain Inventory, Beck Depression Inventory [BDI], Beck Anxiety Inventory, Pain Catastrophizing Scale [PCS], and Margolis Pain Drawing and Scoring System [MPDSS]) were also used to assess pain in its globality.

Results

Analysis of pain logbooks revealed that active tDCS led to a reduction in daily average pain intensity (all p ≤ 0.04), while sham tDCS did not produce any change (p = 0.15). Between-group comparisons for change in pain intensity reduction between active and sham tDCS showed a trend during treatment (p = 0.08) which was significant at the follow-up period (p = 0.02). Active tDCS also improved scores of all questionnaires (all p ≤ 0.02), while sham tDCS only reduced MPDSS scores (p = 0.04). Between-group comparisons for the pain-related outcomes showed significant differences for BDI et PCS after the last tDCS session.

Conclusions

These results suggest that anodal tDCS applied over the primary motor cortex is an effective modality to decrease pain in older individuals. tDCS can also improve other key outcomes, such as physical and emotional functioning, and catastrophic thinking.

A Neurochemical and Electrophysiological Study on the Combined Effects of Caffeine and Nicotine in the Cortex of Rats

Introduction:

Caffeine and nicotine are the most widely consumed psychostimulants worldwide. Although the effects of each drug alone on the central nervous system have been studied extensively, the literature on the neurochemical and electrophysiological effects of their combined treatments is scarce. The present study investigated the cortical electrophysiological and neurochemical alterations induced by acute administration of caffeine and nicotine in rats.

Methods:

The rats received caffeine and nicotine at a 1-hour interval between the two treatments.

Results:

Caffeine and nicotine administration resulted in a significant decrease in the concentrations of cortical amino acid neurotransmitters, namely glutamate, aspartate, glycine, and taurine, while γ-aminobutyric acid (GABA) significantly increased. Increased cortical lipid peroxidation and reduced glutathione and nitric oxide levels and acetylcholinesterase and Na⁺/K⁺-ATPase activities were also observed. The Electroencephalogram (EEG) showed an increase in delta frequency power band, whereas theta, beta-1, and beta-2 decreased after caffeine and nicotine treatment.

Conclusion:

These findings suggest that caffeine and nicotine adversely exacerbate their stimulant effects manifested by the EEG changes mediated by increasing cholinergic transmission and disturbing the balance between the excitatory and inhibitory amino acids leading to oxidative stress.

EEG-Based Measures in At-Risk Mental State and Early Stages of Schizophrenia: A Systematic Review

Introduction: Electrophysiological (EEG) abnormalities in subjects with schizophrenia have been largely reported. In the last decades, research has shifted to the identification of electrophysiological alterations in the prodromal and early phases of the disorder, focusing on the prediction of clinical and functional outcome. The identification of neuronal aberrations in subjects with a first episode of psychosis (FEP) and in those at ultra high-risk (UHR) or clinical high-risk (CHR) to develop a psychosis is crucial to implement adequate interventions, reduce the rate of transition to psychosis, as well as the risk of irreversible functioning impairment. The aim of the review is to provide an up-to-date synthesis of the electrophysiological findings in the at-risk mental state and early stages of schizophrenia. Methods: A systematic review of English articles using Pubmed, Scopus, and PsychINFO was undertaken in July 2020. Additional studies were identified by hand-search. Electrophysiological studies that included at least one group of FEP or subjects at risk to develop psychosis, compared to healthy controls (HCs), were considered. The heterogeneity of the studies prevented a quantitative synthesis. Results: Out of 319 records screened, 133 studies were included in a final qualitative synthesis. Included studies were mainly carried out using frequency analysis, microstates and event-related potentials. The most common findings included an increase in delta and gamma power, an impairment in sensory gating assessed through P50 and N100 and a reduction of Mismatch Negativity and P300 amplitude in at-risk mental state and early stages of schizophrenia. Progressive changes in some of these electrophysiological measures were associated with transition to psychosis and disease course. Heterogeneous data have been reported for indices evaluating synchrony, connectivity, and evoked-responses in different frequency bands. Conclusions: Multiple EEG-indices were altered during at-risk mental state and early stages of schizophrenia, supporting the hypothesis that cerebral network dysfunctions appear already before the onset of the disorder. Some of these alterations demonstrated association with transition to psychosis or poor functional outcome. However, heterogeneity in subjects' inclusion criteria, clinical measures and electrophysiological methods prevents drawing solid conclusions. Large prospective studies are needed to consolidate findings concerning electrophysiological markers of clinical and functional outcome.

Reliability of quantitative transverse relaxation time mapping with [Formula: see text]-prepared whole brain pCASL

Arterial spin labeling (ASL) is increasingly applied for cerebral blood flow mapping, but [Formula: see text] relaxation of the ASL signal magnetization is often ignored, although it may be clinically relevant. To investigate the extent, to which quantitative [Formula: see text] values in gray matter (GM) obtained by pseudocontinuous ASL (pCASL) perfusion MRI can be reproduced, are reliable and a potential neuroscientific biomarker, a prospective study was performed with ten healthy volunteers (5F,28 ± 3y) at a 3 T scanner. A [Formula: see text]-prepared pCASL sequence enabled the measurement of quantitative [Formula: see text] and perfusion maps. [Formula: see text] times were modeled per voxel and analyzed within four GM-regions-of-interest (ROI). The intraclass correlation coefficients (ICCs) of the quantified ASL-[Formula: see text] varied across brain regions. When averaged across subjects and postlabeling delays (PLDs), the ICCs ranged from reasonable values in parietal regions (ICC = 0.56) to smaller values in frontal regions (ICC = 0.36). Corresponding subject-averaged within-subject coefficients of variation (WSCVs) showed good test-retest measurement precision ([Formula: see text] for all PLDs), but more pronounced inter-subject variance. Reliability and precision of quantified ASL-[Formula: see text] were region-, PLD- and subject-specific, showing fair to robust results in occipital, parietal and temporal ROIs. The results give rise to consider the method for future cerebral studies, where variable perfusion or altered [Formula: see text] times are suspected.

Age Modulates the Association of Caffeine Intake With Cognition and With Gray Matter in Elderly Diabetics

BACKGROUND

The association between caffeine and cognitive performance has not been tested in older individuals with type 2 diabetes (T2D). Its association with brain volume in T2D has been tested only in animals.

METHODS

We examined the association of caffeine with cognitive function and brain volume in a sample of elderly diabetics participating in the Israel Diabetes and Cognitive Decline Study (n = 638) and the moderating effect of age on this association. In a subsample (n = 185) with magnetic resonance imaging, we also examined these associations with gray and white matter volumes (GM/WM).

RESULTS

Using linear regression adjusting for cognition-related covariates, we found that higher caffeine intake was associated with better function in overall cognition (p = .018), attention/working memory (p = .002), executive functioning (p = .047), and semantic categorization (p = .026). Interaction analyses of caffeine intake with age were significant for semantic categorization (p = .025), and approached significance for overall cognition (p = .066). This association was driven by the older group (above-median) for whom the association of caffeine intake with semantic categorization (p = .001), attention/working memory (p = .007), executive functioning (p = .005), and overall cognition (p = .002) were significant. In the magnetic resonance imaging subsample, there was an interaction (p = .034) of caffeine intake with age for GM volume; in the older group, higher caffeine intake was associated with greater GM volume (β = .198, p = .033).

CONCLUSIONS

Caffeine intake may have a beneficial role in cognitive functioning of elderly adults with T2D, which may be moderated by age. Greater GM volume may be a mechanism underlying the association of higher caffeine intake with better cognitive function.

Comparison of brain white matter hyperintensities in methamphetamine and methadone dependent patients and healthy controls

Background:

Previous studies have proven the development of white matter hyperintensities (WMH) in methamphetamine and opioid users. Opiates and methamphetamines (MA) are the most common addictive agents in Iran. The adverse effects of drugs on the CNS is of concern to specialists and researchers, and given that the neurotoxicity associated with methamphetamine is greater than opioids, it is hypothesized that the severity of WMH in patients with methamphetamine dependence is more than opioid drug-dependent individuals.

Objectives:

To our knowledge, this is the first research comparing the effect of methamphetamine and methadone (M) on the brain.

Patients and Methods:

In a historical cohort study, we compared WMH in the brain MRI of 50 methamphetamine-dependent patients, 50 methadone-dependent patients and 50 healthy volunteers who were matched for age, sex and dominant hand.

Results:

WMH was detected in 18 methamphetamine users, in 12 methadone users and in seven controls (P = 0.038). The site of brain lesions in MA users was mostly in the frontal lobe in 17 cases, in M users in the frontal lobe in 12 cases and in the control group, it was in the parietal lobe in four cases (P=0.001). The frontal lobes were the predominant locations of WMH in MA and M groups (P = 0.001). The frequency of brain lesions was mostly in the deep WM in 18 cases in MA users, in 12 cases in M users and in two cases in the control group (P=0.007). Hyper-signal foci of deep WM in the MA group were grade I (punctuate) in 12 cases, grade II (beginning confluence) in five cases and grade III (large confluent) in four cases. In the M group, there were six cases in grade I, three cases in grade II and one case in grade III. In the control group, there were three grade I cases, two grade II cases, and no grade III cases. Except for periventricular WMH (P = 0.13), there were statistical significant differences in the deep WMH (P = 0.007) and subcortex WMH (P = 0.01) between the three groups. The history of using other drugs and the duration of MA and M consumption were similar. The prevalence of brain lesions was generally higher in both drug user groups compared with the healthy controls. Increased WMH in the MA group was higher than the M group.

Conclusions:

A greater number of blood flow defects and ischemic lesions in the brain of MA users compared to opiate users may explain the prevalence of psychiatric disorders in these patients.

Acute effects of tea consumption on attention and mood

Tea has historically been associated with mood and performance benefits, such as relaxation and concentration. This review summarizes the research on the acute effects of tea, and its ingredients theanine and caffeine, on attention and mood. Consistent with abundant research on the benefits of caffeine, the performance benefits of tea were identified in a number of studies, with particularly consistent evidence for improved attention. Tea consumption also consistently improved self-reported alertness and arousal, whereas effects on pleasure or relaxation were less consistent. In addition to the research on caffeine in real-life performance, 2 recent studies have provided a broader perspective on tea's effects on psychological function in that they showed beneficial effects in related areas such as work performance and creativity. These studies showed the validity of laboratory findings by supporting the idea that tea consumption has acute benefits on both mood and performance in real-life situations.

Comorbid substance use disorder in schizophrenia: a selective overview of neurobiological and cognitive underpinnings

Although individuals with schizophrenia show a lifetime prevalence of 50% for suffering from a comorbid substance use disorder, substance abuse usually represents an exclusion criterion for studies on schizophrenia. This implies that surprisingly little is known about a large group of patients who are particularly difficult to treat. The aim of the present work is to provide a brief and non-exhaustive overview of the current knowledgebase about neurobiological and cognitive underpinnings for dual diagnosis schizophrenia patients. Studies published within the last 20 years were considered using computerized search engines. The focus was on nicotine, caffeine, alcohol, cannabis and cocaine being among the most common substances of abuse. All drugs of abuse target dopaminergic, glutamatergic and GABAergic transmission which are also involved in the pathophysiology of schizophrenia. Current literature suggests that neurocognitive function might beless disrupted in substance-abusing compared to non-abusing schizophrenia patients, but in particular the neuroimaging database on this topic is sparse. Detrimental effects on brain structure and function were shown for patients for whom alcohol is the main substance of abuse. It is as yet unclear whether this finding might be an artifact of age differences of patient subgroups with different substance abuse patterns. More research is warranted on the specific neurocognitive underpinnings of schizophrenia patients abusing distinct psychoactive substances. Treatment programs might either benefit from preserved cognitive function as a resource or specifically target cognitive impairment in different subgroups of addicted schizophrenia patients.

Caffeine as an attention enhancer: reviewing existing assumptions

RATIONALE

Despite the large number of studies on the behavioural effects of caffeine, an unequivocal conclusion had not been reached. In this review, we seek to disentangle a number of questions.

OBJECTIVE

Whereas there is a general consensus that caffeine can improve performance on simple tasks, it is not clear whether complex tasks are also affected, or if caffeine affects performance of the three attention networks (alerting, orienting and executive control). Other questions being raised in this review are whether effects are more pronounced for higher levels of caffeine, are influenced by habitual caffeine use and whether there effects are due to withdrawal reversal.

METHOD

Literature review of double-blind placebo controlled studies that assessed acute effects of caffeine on attention tasks in healthy adult volunteers.

RESULTS

Caffeine improves performance on simple and complex attention tasks, and affects the alerting, and executive control networks. Furthermore, there is inconclusive evidence on dose-related performance effects of caffeine, or the influence of habitual caffeine consumption on the performance effects of caffeine. Finally, caffeine's effects cannot be attributed to withdrawal reversal.

CONCLUSIONS

Evidence shows that caffeine has clear beneficial effects on attention, and that the effects are even more widespread than previously assumed.

Effects of chronic marijuana use on brain activity during monetary decision-making

Marijuana (MJ) acutely acts on cannabinoid receptors that are found in numerous brain regions, including those involved in reward processing and decision-making. However, it remains unclear how long-term, chronic MJ use alters reward-based decision-making. In the present study, using [(15)O]water PET imaging, we measured brain activity in chronic MJ users, who underwent monitored abstinence from MJ for approximately 24 h before imaging, and control participants, while they took part in the Iowa Gambling Task (IGT), a monetary decision making task that strongly relies on the ventromedial prefrontal cortex (vmPFC). During PET imaging, participants took part in the standard and a variant version of the IGT as well as a control task. Chronic MJ users performed equally well on the standard IGT, but significantly worse than controls on the variant IGT. Chronic MJ users and control subjects showed increased regional cerebral blood flow (rCBF) in the vmPFC on both versions of the IGT compared to the control task. In the two-group comparison, chronic MJ users showed significantly greater rCBF than controls in the vmPFC on the standard IGT and greater activity in the cerebellum on both versions of the IGT. Furthermore, duration of use, but not age of first use, was associated with greater activity in the vmPFC. Thus, chronic MJ users tend to strongly recruit neural circuitry involved in decision-making and reward processing (vmPFC), and probabilistic learning (cerebellum) when performing the IGT.

Reduced fronto-cerebellar functional connectivity in chronic alcoholic patients

BACKGROUND

Alcohol dependence is associated with neurocognitive deficits related to neuropathological changes in structure, metabolism, and function of the brain. Impairments of motor functioning in alcoholics have been attributed to well-characterized neuropathological brain abnormalities in cerebellum.

METHODS

Using functional magnetic resonance imaging (fMRI), we studied in vivo the functional connectivity between cerebellar and cortical brain regions. Participants were 10 uncomplicated chronic alcoholic patients studied after 5 to 7 days of abstinence when signs of withdrawal had abated and 10 matched healthy controls. We focused on regions of prefrontal, frontal, temporal, and parietal cortex that exhibited an fMRI response associated with nondominant hand finger tapping in the patients but not in the controls. We predicted that fronto-cerebellar functional connectivity would be diminished in alcoholics compared with controls.

RESULTS

Functional connectivity in a circuit involving premotor areas (Brodmann Area 6) and Lobule VI of the superior cerebellum was reduced in the patients compared with the controls. Functional connectivity was also reduced in a circuit involving prefrontal cortex (Brodmann Area 9) and Lobule VIII of the inferior cerebellum. Reductions in connectivity were specific to fronto-cerebellar circuits and were not found in other regions examined.

CONCLUSIONS

Our findings show a pattern in recently abstinent alcoholic patients of specific deficits in functional connectivity and recruitment of additional brain regions for the performance of a simple finger-tapping task. A small sample, differences in smoking, and a brief abstinence period preclude definitive conclusions, but this pattern of diminished fronto-cerebellar functional connectivity is highly compatible with the characteristic neuropathological lesions documented in alcoholics and may reflect brain dysfunction associated with alcoholism.

Caffeine dose effect on activation-induced BOLD and CBF responses

Caffeine is a popular psychostimulant, typically found in beverages. While low to intermediate doses of caffeine are associated with positive feelings and increased mental performance and alertness, high doses induce negative feelings such as insomnia, anxiety and nervousness. We investigate if this nonlinear dose-response is present for caffeine's effects on functional activation. Twenty-seven healthy subjects were assigned randomly to four different groups: saline, 1 mg/kg, 2.5 mg/kg and 5 mg/kg doses of caffeine. Simultaneous ASL/BOLD timeseries were collected both before and after an intravenous infusion of saline or caffeine and the task-induced CBF and BOLD percent changes were compared. The maximum increase in BOLD response was associated with the intermediate caffeine dose of 2.5 mg/kg, which increased BOLD response by 32.2% and 32.5% in motor and visual areas respectively. The maximum increase in CBF response was associated with the highest caffeine dose of 5 mg/kg. This difference could be related to a different density of A(1) and A(2A) adenosine receptors in the brain.

Bipolar and major depressive disorder: neuroimaging the developmental-degenerative divide

Both major depressive disorder and bipolar disorder are the subject of a voluminous imaging and genetics literature. Here, we attempt a comprehensive review of MRI and metabolic PET studies conducted to date on these two disorders, and interpret our findings from the perspective of developmental and degenerative models of illness. Elevated activity and volume loss of the hippocampus, orbital and ventral prefrontal cortex are recurrent themes in the literature. In contrast, dorsal aspects of the PFC tend to display hypometabolism. Ventriculomegaly and white matter hyperintensities are intimately associated with depression in elderly populations and likely have a vascular origin. Important confounding influences are medication, phenotypic and genetic heterogeneity, and technological limitations. We suggest that environmental stress and genetic risk variants interact with each other in a complex manner to alter neural circuitry and precipitate illness. Imaging genetic approaches hold out promise for advancing our understanding of affective illness.

Does caffeine modulate verbal working memory processes? An fMRI study

To assess the effect of caffeine on the functional MRI signal during a 2-back verbal working memory task, we examined blood oxygenation level-dependent regional brain activity in 15 healthy right-handed males. The subjects, all moderate caffeine consumers, underwent two scanning sessions on a 1.5-T MR-Scanner separated by a 24- to 48-h interval. Each participant received either placebo or 100 mg caffeine 20 min prior to the performance of the working memory task in blinded crossover fashion. The study was implemented as a blocked-design. Analysis was performed using SPM2. In both conditions, the characteristic working memory network of frontoparietal cortical activation including the precuneus and the anterior cingulate could be shown. In comparison to placebo, caffeine caused an increased response in the bilateral medial frontopolar cortex (BA 10), extending to the right anterior cingulate cortex (BA 32). These results suggest that caffeine modulates neuronal activity as evidenced by fMRI signal changes in a network of brain areas associated with executive and attentional functions during working memory processes.

Functional magnetic resonance imaging in nursing research

Functional magnetic resonance imaging (fMRI) is a powerful noninvasive neuroimaging technique nurse scientists can use to investigate the structure and cognitive capacities of the brain. A strong magnetic field and intermittent high-frequency pulses cause protons in body tissues to release energy, which can be recorded and processed into images that are sensitive to specific tissue characteristics. Although temporal and spatial resolution constraints define an upper limit to the precision of magnetic resonance (MR) scanners, the primary index of neuronal activity, hemodynamic response, can be efficiently estimated. Characteristics of the experimental environment, the hypothesis of interest, and the physiology of the cognitive process under investigation provide guidance for the design and limit available options. The processing of functional data to remove unwanted variability is briefly described as are the techniques used to estimate statistical effects and control for the rate of false positives in the results. A detailed applied example of nursing research is included to demonstrate the practical application of the theory, methods, and techniques being discussed. A glossary of key terms is also provided.

Increased white matter hyperintensities in male methamphetamine abusers

BACKGROUND

The current study was conducted to compare the prevalence, severity, and location of white matter signal hyperintensities (WMH) on brain magnetic resonance (MR) imaging in methamphetamine (MA) abusers.

METHODS

Thirty-three MA abusers and 32 age- and gender-matched healthy comparison subjects were studied. Axial T-2 weighted images and fluid attenuated inversion recovery axial images were obtained using 3.0 T MR scanner. The severity of WMH was assessed separately for deep and periventricular WMH. Ordinal logistic regression models were used to assess the odds ratio for WMH.

RESULTS

MA abusers had greater severity of WMH than the healthy comparison subjects (odds ratio: 7.06, 8.46, and 4.56 for all, deep, and periventricular WMH, respectively). Severity of deep WMH correlated with total cumulative dose of MA (p = 0.027). Male MA abusers had greater severity of WMH than female MA abusers (odds ratio = 10.00). While male MA abusers had greater severity of WMH than male comparison subjects (odds ratio = 18.86), there was no significant difference in WMH severity between female MA abusers and female comparison subjects.

CONCLUSIONS

The current study reports increased WMH in MA abusers, which may be related to MA-induced cerebral perfusion deficits. In addition, female MA abusers had less severe WMH than male MA abusers, possibly due to estrogen's protective effect against ischemic or neurotoxic effects of MA.

Clinical applicability of functional MRI

Functional MRI (fMRI) has become the most widely used modality for examining human brain function in basic and clinical neuroscience. As compared to the application of fMRI in basic neuroscience research, clinical fMRI presents unique challenges. A growing body of literature supports the feasibility of clinical fMRI, with the best-studied applications being localization of motor cortex and lateralization of language. While it may be tempting to assume that fMRI will supercede prior approaches, it may turn out that fMRI will be used to complement more difficult or invasive methods rather than replace them entirely. This article focuses on fMRI studies in patients and patient populations. Specific considerations for such applications include pathophysiological effects on functional physiology, brain-behavior correlations in the presence of cognitive or sensorimotor deficits, and test-retest reliability for longitudinal studies.

Concurrent CBF and CMRGlc changes during human brain activation by combined fMRI–PET scanning

A novel approach for concurrent measurement of regional cerebral blood flow (CBF) and regional cerebral metabolic rate for glucose consumption (CMRGlc) in humans is proposed and validated in normal subjects during visual stimulation. 18F-labeled fluorodeoxyglucose was administered during the measurement of CBF by continuous arterial spin labeled magnetic resonance imaging (MRI). Subsequent positron emission tomographic (PET) scanning demonstrated the distribution of labeled deoxyglucose during the MRI acquisition. An excellent concordance between regional CBF and regional CMRGlc during visual stimulation was found, consistent with previously published PET findings. Although initially validated using a brief, non-quantitative protocol, this approach can provide quantitative CBF and CMRGlc, with a broad range of potential applications in functional physiology and pathophysiology.

Personality predicts brain responses to cognitive demands

Eysenck (1981) proposed that the personality dimension of introversion- extraversion (E) reflects individual differences in a cortical arousal system modulated by reticulothalamic- cortical pathways: it is chronically more active in introverts relative to extraverts and influences cognitive performance in interaction with task parameters. A circuit with connections to this system, including the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate (AC) cortex, has been identified in studies applying functional magnetic resonance imaging (fMRI) to a broad range of cognitive tasks. We examined the influence of E, assessed with the Eysenck Personality Questionnaire-Revised (Eysenck and Eysenck, 1991), in fMRI activity during an "n-back" task involving four memory loads (0-, 1-, 2-, and 3-back) and a rest condition in healthy men. To confirm the specificity of E effects, we also examined the effects of neuroticism and psychoticism (P) scores. We observed that, as predicted by Eysenck's model, the higher the E score, the greater the change in fMRI signal from rest to the 3-back condition in the DLPFC and AC. In addition, E scores were negatively associated with resting fMRI signals in the thalamus and Broca's area extending to Wernicke's area, supporting the hypothesized (negative) relationship between E and resting arousal. P scores negatively correlated with resting fMRI signal in the globus pallidus-putamen, extending previous findings of a negative relationship of schizotypy to striatal activity seen with older neuroimaging modalities to fMRI. These observations suggest that individual differences affect brain responses during cognitive activity and at rest and provide evidence for the hypothesized neurobiological basis of personality.

Smoking and depression

The relationship between smoking and depression is bidirectional. Recent research has focused on nicotine's neurobiologic impact on the brain as it relates to depression. Genetic factors are also important and may account for up to 67% of smoking initiation, maintenance, and dependence. Because nicotine withdrawal may mimic and induce depression, appropriate clinical evaluation and treatment are essential to reduce the high morbidity and mortality associated with smoking and depression and maximize smoking cessation rates.

White matter hyperintensities in subjects with cocaine and opiate dependence and healthy comparison subjects

The prevalence, severity, and location of white matter signal hyperintensities (WMH) on brain magnetic resonance images were compared in patients with cocaine or opiate dependence and healthy subjects. Patients with cocaine (n=32) and opiate dependence (n=32), whose diagnoses were confirmed with the Structured Clinical Interview for DSM-IV, and age- and sex-matched healthy subjects (n=32) were scanned using a 1.5 T whole body GE magnetic resonance scanner. Axial proton-density and T2-weighted images were obtained as well as fluid-attenuated inversion recovery axial images. The severity of WMH was assessed separately for deep (and insular) and periventricular WMH, using a modified composite version of the rating scales of Fazekas and Coffey. The cocaine-dependent group had greater severity of WMH than the opiate-dependent group, which in turn had greater severity of WMH than the healthy comparison group (odds ratios=2.54 and 2.90, respectively). The cocaine-dependent group had greater lesion severity of deep and insular WMH than the opiate-dependent group and the healthy comparison group (odds ratio>3.25 for deep WMH; odds ratio>4.38 for insular WMH). For periventricular WMH, there were no significant differences between the three groups. The frontal lobes were the predominant locations of WMH in both substance-dependent groups. The greater prevalence and severity of WMH in cocaine-dependent subjects than in opiate-dependent subjects may reflect the fact that cocaine induces more ischemia via vasoconstriction than opiates. Also, there was a trend for lower WMH severity in substance-dependent women relative to the healthy comparison group, possibly due to estrogen's protective effect against cerebrovascular accidents.

Dietary caffeine consumption and withdrawal: confounding variables in quantitative cerebral perfusion studies?

PURPOSE

To evaluate the effects of dietary caffeine intake and withdrawal on cerebral blood flow (CBF), as determined from a randomized, blinded, placebo-controlled study.

MATERIALS AND METHODS

Twenty adults (16 men, four women; age range, 24-64 years) categorized as low (mean, 41 mg/d) or high (mean, 648 mg/d) caffeine users underwent quantitative flow-sensitive alternating inversion-recovery perfusion magnetic resonance (MR) imaging twice: 90 minutes after a dose of caffeine (250 mg) on one day and after a dose of placebo on another day (randomized counterbalanced design). Doses were preceded by 30 hours of caffeine abstinence to induce withdrawal in high caffeine users. Quantitative CBF maps were gray matter (GM)-white matter (WM) segmented and subjected to region-of-interest analysis to obtain mean CBF in WM, anterior circulation GM (AGM), and posterior circulation GM (PGM). By using two-way repeated-measures analysis of variance, regional CBF data were tested for within-subject differences between caffeine and placebo and for between-subject differences related to dietary caffeine habits. Linear regression was used to determine whether dietary caffeine use predicts CBF or CBF response to caffeine.

RESULTS

Caffeine reduced CBF (P < or =.05) by 23% (AGM, PGM) and 18% (WM) in all subjects. Postplacebo (withdrawal) CBF in high caffeine users exceeded that in low users (P < or =.05) by 31% (AGM) and 32% (WM) (PGM, not significant). Mean postcaffeine CBF reduction in AGM was 26% in high users versus 19% in low users (P < or =.05; PGM and WM, not significant). Increasing caffeine consumption predicted higher CBF (P < or =.05) in all regions: r = 0.79 (AGM), 0.57 (PGM), and 0.76 (WM). Dietary caffeine use did not predict CBF response to caffeine.

CONCLUSION

Dietary caffeine consumption and withdrawal are potential confounding variables in cerebral perfusion and functional MR imaging.