Functional Neuroimaging Techniques Research Articles

Inverse source imaging methods in recovering distributed brain sources

Over the past decades tremendous efforts have been made in developing functional neuroimaging techniques to better understand human brain functions in both normal and diseased states. Towards this goal, it is essential to develop a technique that can noninvasively image human brain activity with high spatial and temporal resolution. Electroencephalography (EEG) and magnetoencephalography (MEG) are important tools for studying the human brain’s large-scale neuronal dynamics, thanks to their millisecond temporal resolution. However, EEG and MEG are limited in providing spatial information concerning the location of active sources in the brain. Localizing the sources of EEG/MEG dynamics can be achieved by the so-called electrophysiological source imaging techniques. Recently, there has been a growing interest in source imaging techniques in recovering distributed brain sources. Such distributed source imaging techniques have been advanced in many aspects, including the forward modeling and the inverse imaging, and have been shown promising in many neuroscience and clinical applications. This paper reviews the basic principles, recent advancements and applications of the distributed source imaging techniques.

Infrared thermal imaging of rat somatosensory cortex with whisker stimulation

The present study aims to validate the applicability of infrared (IR) thermal imaging for the study of brain function through experiments on the rat barrel cortex. Regional changes in neural activity within the brain produce alterations in local thermal equilibrium via increases in metabolic activity and blood flow. We studied the relationship between temperature change and neural activity in anesthetized rats using IR imaging to visualize stimulus-induced changes in the somatosensory cortex of the brain. Sensory stimulation of the vibrissae (whiskers) was given for 10 s using an oscillating whisker vibrator (5-mm deflection at 10, 5, and 1 Hz). The brain temperature in the observational region continued to increase significantly with whisker stimulation. The mean peak recorded temperature changes were 0.048 ± 0.028, 0.054 ± 0.036, and 0.097 ± 0.015°C at 10, 5, and 1 Hz, respectively. We also observed that the temperature increase occurred in a focal spot, radiating to encompass a larger region within the contralateral barrel cortex region during single-whisker stimulation. Whisker stimulation also produced ipsilateral cortex temperature increases, which were localized in the same region as the pial arterioles. Temperature increase in the barrel cortex was also observed in rats treated with a calcium channel blocker (nimodipine), which acts to suppress the hemodynamic response to neural activity. Thus the location and area of temperature increase were found to change in accordance with the region of neural activation. These results indicate that IR thermal imaging is viable as a functional quantitative neuroimaging technique.

Using manganese-enhanced MRI to understand BOLD

The 1990s were designated "The Decade of the Brain" by U.S. Congress, perhaps in great anticipation of the impact that functional neuroimaging techniques would have on advancing our understanding of how the brain is functionally organized. While it is impossible to overestimate the impact of functional MRI in neuroscience, many aspects of the blood oxygenation level-dependent (BOLD) contrast remain poorly understood, in great part due to the complex relationship between neural activity and hemodynamic changes. To better understand such relationship, it is important to probe neural activity independently. Manganese-enhanced MRI (MEMRI), when used to monitor neural activity, is a technique that uses the divalent manganese ion, Mn(2+), as a surrogate measure of calcium influx. A major advantage of using Mn(2+) as a functional marker is that the contrast obtained is directly related to the accumulation of the ion in excitable cells in an activity dependent manner. As such, the contrast in MEMRI is more directly related to neural activity then hemodynamic-based fMRI techniques. In the present work, the early conceptualization of MEMRI is reviewed, and the comparative experiments that have helped provide a better understanding of the spatial specificity of BOLD signal changes in the cortex is discussed.

Memory and motivational/emotional processes

As we know from our own experiences and the findings of many studies, emotional events are remembered with greater accuracy, vividness, and persistency compared to events lacking an emotional component (LaBar and Cabeza, 2006; Roozendaal and McGaugh, 2011). How emotional memory is controlled and regulated? This question has fascinated scientists and clinicians for a long time; in fact, the field focused on memory and motivational/emotional processes represents one of the fastest growing areas of neuroscience research. The selectivity that arousal creates is generally beneficial, as emotionally arousing situations in our lives are worth remembering, so that they can be savored and/or instructive. From an evolutionary point of view, it seems logical that a confrontation with an emotionally arousing event, such as a stressful one, is better remembered than a neutral one, resulting in a more adequate motivation to react in a similar situation. Why emotional arousal enhances memory? Taking into account that neural processes initiated by an experience perseverate and consolidate over time, a possible explanation is that emotional arousal could activate neurobiological processes that modulate the consolidation of memories of recent experiences. This special issue includes original papers and review articles that cover cutting-edge research in the interplay between memory, motivation, and emotion, providing the reader with what is up and coming with respect to research findings, theoretical advances, and methodological techniques. Many of the current “hot” topics in the field are covered, including the involvement of specific cerebral regions on the interaction between memory and motivational/emotional processes, the contribution of neurotransmitters and neuromodulators, and the role of arousal and stress. The enhanced memory for emotional events has been attributed to the involvement and interaction of brain regions, in particular between the amygdala and other areas such as the hippocampal formation and prefrontal cortex (Phelps, 2004; Richter-Levin, 2004; McIntyre et al., 2012). The amygdala is active during emotional situations, and this activity influences the encoding and consolidation of the memory trace for the emotional event (McGaugh, 2004). On the light of previous evidence, some papers of this special issue focus on the role of specific neural regions in the interplay between memory and motivational/emotional processes, such as cortical and mesocorticolimbic areas (Martinez-Moreno et al., 2011; El Rawas et al., 2012; Holloway-Erickson et al., 2012; Puglisi-Allegra and Ventura, 2012), hippocampal formation (Hori et al., 2011; Garin-Aguilar et al., 2012), amygdala, substantia nigra, and striatum (Salado-Castillo et al., 2011; Wolf et al., 2011), septal nuclei (Matsuyama et al., 2011), nucleus accumbens (Nunez-Jaramillo et al., 2012), and autonomic nervous system (Garcia et al., 2011). Another group of papers analyzes the role and interaction of neurotransmitters and neuromodulators, such as catecholamines (Puglisi-Allegra and Ventura, 2012), endocannabinoids (Campolongo et al., 2012), acetylcholine and glucocorticoids (Fornari et al., 2012; Sanchez-Resendis et al., 2012) on memory and motivational/emotional processes. In order to highlight the impact of motivation and emotion on memory, functional neuroimaging techniques were used, including multichannel electroencephalography (EEG) (Arnone et al., 2011; Garcia et al., 2011; Uribe et al., 2011) and functional magnetic resonance imaging (fMRI) (Jepma et al., 2012; Rosales-Lagarde et al., 2012). Moreover, taking into account that recent studies have revealed seemingly large, but previously unsuspected, sex-related influences on the well-known mechanism that emotional events are better memorized than neutral events, this special issue includes evidence of sex-related differences in memory and talkativeness for emotional stimuli (Arnone et al., 2011). Finally, considering that in recent years a key conceptual issue, that warrants attention, is the fact that many studies examining emotional memory have focused on the highly arousing nature of emotional stimuli or experimental contexts, as the key component contributing to the enhancement of memory, some papers of this special issue discuss the involvement of arousal and stress in the interplay between memory, motivation, and emotion (Cruciani et al., 2011; Uribe et al., 2011; Packard and Goodman, 2012). In conclusion, we hope that this special issue have provided evidence of the important and rapid progresses in this very interesting and relevant topic, and may give a significant contribution to the knowledge of how memory can be affected by emotional experiences, and related motivation. Then, taking into account that this emergent field is in continuous and fast growing, we strongly hope that the present special issue may motivate many neuroscientists to conduct other studies, paving the way for the next great theories and advances.

Treatment effect of behavior therapy and pharmacotherapy on obsessive-compulsive disorder exploring by functional neuroimaging techniques

Treatment effect of behavior therapy and pharmacotherapy on obsessive-compulsive disorder exploring by functional neuroimaging techniques

Neuroimaging in cluster headache and other trigeminal autonomic cephalalgias

The central nervous system mechanisms involved in trigeminal autonomic cephalalgias, a group of primary headaches characterized by strictly unilateral head pain that occurs in association with ipsilateral craniofacial autonomic features, are still not comprehensively understood. However, functional imaging methods have revolutionized our understanding of mechanisms involved in these primary headache syndromes. The present review provides a brief overview of the major modern functional neuroimaging techniques used to examine brain structure, biochemistry, metabolic state, and functional capacity. The available functional neuroimaging data in cluster headache and other TACs will thus be summarized. Although the precise brain structures responsible for these primary headache syndromes still remain to be determined, neuroimaging data suggest a major role for posterior hypothalamus activation in initiating and maintaining attacks. Furthermore, pathophysiological involvement of the pain neuromatrix and of the central descending opiatergic pain control system was observed. Given the rapid advances in functional and structural neuroimaging methodologies, it can be expected that these non-invasive techniques will continue to improve our understanding into the nature of the brain dysfunction in cluster headache and other trigeminal autonomic cephalalgias.

Glucose metabolism in sporadic Creutzfeldt–Jakob disease: a statistical parametric mapping analysis of 18F‐FDG PET

Reports describing functional neuroimaging techniques, such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT), in sporadic Creutzfeldt-Jakob disease (sCJD) have consistently suggested that these tools are sensitive for the identification of areas of hypoperfusion or hypometabolism, even in the early stages of sCJD. However, there are few reports on the use of [18F]fluoro-2-deoxy-D-glucose (FDG) PET in sCJD, and most of them are single case reports. Only two small cohort studies based on visual inspection or a region of interest method have been published to date. Using a statistical parametric mapping (SPM) analysis of (18) F-FDG PET, we investigated whether there are brain regions preferentially affected in sCJD. After controlling for age and gender, using SPM 2, we compared the glucose metabolism between (i) 11 patients with sCJD and 35 controls and (ii) the subset of five patients with the Heidenhain variant of sCJD and 35 controls. The patients with sCJD showed decreased glucose metabolism in bilateral parietal, frontal and occipital cortices. The Heidenhain variant of sCJD showed glucose hypometabolism mainly in bilateral occipital areas. Glucose hypometabolism in sCJD was detected in extensive cortical regions; however, it was not found in the basal ganglia or thalamus, which are frequently reported to be affected on diffusion-weighted images. The medial temporal area, which is possibly resistant to the prion deposits, was also less involved in sCJD.

How the Blind “See” Braille and the Deaf “Hear” Sign: Lessons from fMRI on the Cross-Modal Plasticity, Integration, and Learning

What does the visual cortex of the blind do during Braille reading? This process involves converting simple tactile information into meaningful patterns that have lexical and semantic properties. The perceptual processing of Braille might be mediated by the somatosensory system, whereas visual letter identity is accomplished within the visual system in sighted people. Recent advances in functional neuroimaging techniques have enabled exploration of the neural substrates of Braille reading (Sadato et al. 1996, 1998, 2002, Cohen et al. 1997, 1999). The primary visual cortex of early-onset blind subjects is functionally relevant to Braille reading, suggesting that the brain shows remarkable plasticity that potentially permits the additional processing of tactile information in the visual cortical areas. Similar cross-modal plasticity is observed by the auditory deprivation: Sign language activates the auditory cortex of deaf subjects (Neville et al. 1999, Nishimura et al. 1999, Sadato et al. 2004). Cross-mod...

The Motivated Brain: Insights from Neuroimaging Studies of Human Male Sexual Affiliation Context

The advent of functional neuroimaging techniques has allowed to address the question of the role of the brain in a new light, being now able to record brain activity under different kinds of perceptual, cognitive or motor paradigms. Two exponentially emerging fields, i.e. social and affective neurosciences, converge on topics such as brain processing of emotional information issued by the congeners. As any social interaction obbeys a motivational dimension of interattraction, it is therefore important to study the role of the brain in specific functional contexts. In this paper we show how the emergence of a new field crystallized around the study of brain circuits involved in sexual affiliation has helped providing important results to understand the brain’s role in social motivated interactions. Specifically, these studies show for this involvement a central physiological component and its cortical representation that seems to be essential for social interactions with motivational component.

Structural and Functional Imaging Correlates of Cognitive and Brain Reserve Hypotheses in Healthy and Pathological Aging

In the field of ageing and dementia, brain- or cognitive reserve refers to the capacity of the brain to manage pathology or age-related changes thereby minimizing clinical manifestations. The brain reserve capacity (BRC) hypothesis argues that this capacity derives from an individual's unique neural profile (e.g., cell count, synaptic connections, brain volume, etc.). Complimentarily, the cognitive reserve (CR) hypothesis emphasizes inter-individual differences in the effective recruitment of neural networks and cognitive processes to compensate for age-related effects or pathology. Despite an abundance of research, there is scarce literature attempting to synthesize the BRC the CR models. In this paper, we will review important aging and dementia studies using structural and functional neuroimaging techniques to investigate and attempt to assimilate both reserve hypotheses. The possibility to conceptualize reserve as reflecting indexes of brain plasticity will be proposed and novel data suggesting an intimate and complex correspondence between active and passive components of reserve will be presented.

Traitement par électroconvulsivothérapie d’une tétraplégie par conversion hystérique : à propos d’un cas

Conversion disorder refers to the occurrence of neurological-like symptoms or deficits that are neither intentionally produced nor simulated. While it cannot be explained by an organic disease, it is often related to psychological events. We report the case of a 33-year-old patient with a fluctuating hysterical tetraplegia, which had started three years earlier. After the failure or the exhaustion of several biological (psychotropic medication, transcranial magnetic stimulation) and psychotherapeutic strategies, treatment with electroconvulsive therapy (ECT) was conducted. A total of thirty-five ECT sessions were performed. Whereas the patient's clinical state was initially characterized by a complete quadriplegia and an uncontrollable muscular hypertonia, we noted that the ECT sessions were associated with a slow, though remarkable, progress. At first, the sessions were followed by moments of altered consciousness during which the patient would be relaxed and could make simple movements. Secondarily, not only was our patient able to consciously move his four limbs, but he was also able to walk. However, those improvements remained partial and fluctuating, sometimes allowing the symptom to return temporarily secondary to frustrations or annoyances. Finally, our patient relapsed. Nevertheless, his clinical state presently remains better than that in which we first knew him. The treatment of conversion disorders has been the subject of few studies and predominantly remains symptomatic. Its main goals are: to lessen secondary gains impact by adopting a neutral behaviour towards the symptom and by encouraging physical rehabilitation; to lower the symptom by allowing the patient to understand the normal functioning of the diseased organ, and; to help the patient to deal with stressful situations. There is no evidence that hypnosis is superior to medical and other psychotherapeutic approaches. Pharmacological treatments may be helpful in the case of anxiety, impulsivity or depression, albeit delivered with caution. According to some case reports, transcranial magnetic stimulation has also been associated with clinical remission. Although the use of ECT in motor conversion disorders constitutes an uncommon procedure, and even if no clinical trial has evaluated its impact on such a pathological condition, several case reports suggest that electroconvulsive therapy can be efficient in the treatment of motor conversion disorders. This efficacy may rely on several hypotheses. ECT could induce neural modifications, and participate in the suppression of an active inhibition, which is responsible for hysterical symptoms. Indeed, conversion cerebral disorder correlates can be explored with the help of functional neuro-imaging techniques, which could therefore also identify ECT neural effects. ECT adverse effects on memory could lead to a new relationship with the symptom, and modulate the psychological conflict which has participated in its emergence. Narcoanalysis, ECT sessions could have an impact on consciousness by means of some dissolution and reorganization phenomenon. It could therefore participate in the ending of an emotional block, the psychic integration of traumatic events and the recovery of a voluntary motor control. Finally, ECT could be efficient thanks to its antidepressant properties, especially its ability to stimulate triaminergic, and particularly dopaminergic transmission. This case report reminds us how difficult it can be to deal with severe conversion disorders, and to navigate between two reefs, which are abstention, and therapeutic escalation.

Neural reward processing under dopamine agonists: Imaging

Impulse control disorders (ICDs) are increasingly reported as a considerable side-effect of treatment with dopaminergic medication (both levodopa and dopamine agonists (DA)). ICDs together with punding are described within the entity of dopamine dysregulation syndrome along with immediate reward seeking and addictive behaviors. The brain functions involved in reward processing in general and their modulation by medication can be characterized by neuropsychological assessments and underlying neurobiology can be investigated by functional neuroimaging techniques such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET). By this approach, functional changes of brain areas involved in reward processing under short-term or chronic DA therapy were studied. Functional changes in a network involving striatal–thalamic loops, key structures of the reward system, together with limbic areas (such as the amygdala) and the ventral tegmental area could be related to pharmacological alterations of reward processing by dopaminergic medication. In particular, altered ventral striatal functioning seems to relate to ICDs such as pathological gambling. A general medication effect in patients under DA in terms of a sensitization toward ICD could be demonstrated. A synopsis is given on the applications of functional neuroimaging to investigate reward processing and the influence of dopaminergic medication.

Functional mapping of rat brain activation following rTMS using activity-induced manganese-dependent contrast

Objective: Functional neuroimaging techniques act as the navigator to assess changes in brain activity induced by repetitive transcranial magnetic stimulation (rTMS) in rTMS studies. The aim of this study was to investigate the feasibility of using manganese-enhanced magnetic resonance imaging (MEMRI) to measure the brain activity in rTMS studies.Methods: Eighteen Wistar rats were randomized into three groups (n = 6) including a high rTMS group, a low rTMS group and a sham stimulation group (controls). They were given rTMS of 10 Hz, 1 Hz or sham stimulation for 5 hours separately. MEMRI was used to assess the changes of brain activity.Results: Compared with the controls, image intensity was enhanced differently in various brain regions on T1-weighted images after rTMS with different frequencies, higher intensity and wider enhancement occurred in the high frequency rTMS group as compared with that in the low frequency rTMS group.Conclusion: MEMRI can be used to reveal the changes of brain activity in live rats following rTMS.Significance: The current experiment might provide a new functional neuroimaging technique for the study of rTMS.

Autistic Traits and Brain Activation during Face-to-Face Conversations in Typically Developed Adults

BackgroundAutism spectrum disorders (ASD) are characterized by impaired social interaction and communication, restricted interests, and repetitive behaviours. The severity of these characteristics is posited to lie on a continuum that extends into the general population. Brain substrates underlying ASD have been investigated through functional neuroimaging studies using functional magnetic resonance imaging (fMRI). However, fMRI has methodological constraints for studying brain mechanisms during social interactions (for example, noise, lying on a gantry during the procedure, etc.). In this study, we investigated whether variations in autism spectrum traits are associated with changes in patterns of brain activation in typically developed adults. We used near-infrared spectroscopy (NIRS), a recently developed functional neuroimaging technique that uses near-infrared light, to monitor brain activation in a natural setting that is suitable for studying brain functions during social interactions.MethodologyWe monitored regional cerebral blood volume changes using a 52-channel NIRS apparatus over the prefrontal cortex (PFC) and superior temporal sulcus (STS), 2 areas implicated in social cognition and the pathology of ASD, in 28 typically developed participants (14 male and 14 female) during face-to-face conversations. This task was designed to resemble a realistic social situation. We examined the correlations of these changes with autistic traits assessed using the Autism-Spectrum Quotient (AQ).Principal FindingsBoth the PFC and STS were significantly activated during face-to-face conversations. AQ scores were negatively correlated with regional cerebral blood volume increases in the left STS during face-to-face conversations, especially in males.ConclusionsOur results demonstrate successful monitoring of brain function during realistic social interactions by NIRS as well as lesser brain activation in the left STS during face-to-face conversations in typically developed participants with higher levels of autistic traits.

Is There a Cartesian Renaissance of the Mind or Is It Time for a New Taxonomy for Low Responsive States?

The mass media have recently pointed out the likelihood of diagnostic errors in post-coma patients. Late recoveries of consciousness, even after 20 years, might indicate hidden misdiagnoses that are not corrected over a long period of time. The rate of misdiagnoses of patients in a vegetative state is very high when based on behavioral assessment strategies alone. An extremely restrictive motor repertoire, as occurs in locked-in patients, seems to be the major factor responsible for diagnostic confusion. Functional neuroimaging techniques are regarded as promising tools in unearthing covert awareness in behaviorally unresponsive patients who are unable to produce any motor output. However, unless we believe that these patients persistently live in an unconvincing Cartesian-like state, in which thinking and acting are mutually dissociated, we have to admit that a new taxonomy for low responsive states is called for. This taxonomy should take into account the possible syndromic overlap between disorders of consciousness and locked-in syndrome. We should suspect a "locked-in state" in behaviorally unresponsive patients unless we reach strong evidence that such is not the case; this is the only way to avoid dramatic misdiagnoses.

An empirical investigation of motion effects in eMRI of interictal epileptiform spikes

We recently developed a functional neuroimaging technique called encephalographic magnetic resonance imaging (eMRI). Our method acquires rapid single-shot gradient-echo echo-planar MRI (repetition time=47 ms); it attempts to measure an MR signal more directly linked to neuronal electromagnetic activity than existing methods. To increase the likelihood of detecting such an MR signal, we recorded concurrent MRI and scalp electroencephalography (EEG) during fast (20–200 ms), localized, high-amplitude (>50 μV on EEG) cortical discharges in a cohort of focal epilepsy patients. Seen on EEG as interictal spikes, these discharges occur in between seizures and induced easily detectable MR magnitude and phase changes concurrent with the spikes with a lag of milliseconds to tens of milliseconds. Due to the time scale of the responses, localized changes in blood flow or hemoglobin oxygenation are unlikely to cause the MR signal changes that we observed. While the precise underlying mechanisms are unclear, in this study, we empirically investigate one potentially important confounding variable — motion. Head motion in the scanner affects both EEG and MR recording. It can produce brief “spike-like” artifacts on EEG and induce large MR signal changes similar to our interictal spike-related signal changes. In order to explore the possibility that interictal spikes were associated with head motions (although such an association had never been reported), we had previously tracked head position in epilepsy patients during interictal spikes and explicitly demonstrated a lack of associated head motion. However, that study was performed outside the MR scanner, and the root-mean-square error in the head position measurement was 0.7 mm. The large inaccuracy in this measurement therefore did not definitively rule out motion as a possible signal generator. In this study, we instructed healthy subjects to make deliberate brief (<500 ms) head motions inside the MR scanner and imaged these head motions with concurrent EEG and MRI. We compared these artifactual MR and EEG data to genuine interictal spikes. While per-voxel MR and per-electrode EEG time courses for the motion case can mimic the corresponding time courses associated with a genuine interictal spike, head motion can be unambiguously differentiated from interictal spikes via scalp EEG potential maps. Motion induces widespread changes in scalp potential, whereas interictal spikes are localized and have a regional fall-off in amplitude. These findings make bulk head motion an unlikely generator of the large spike-related MR signal changes that we had observed. Further work is required to precisely identify the underlying mechanisms.

Pharmacological differentiation of opioid receptor antagonists by molecular and functional imaging of target occupancy and food reward-related brain activation in humans

Opioid neurotransmission has a key role in mediating reward-related behaviours. Opioid receptor (OR) antagonists, such as naltrexone (NTX), can attenuate the behaviour-reinforcing effects of primary (food) and secondary rewards. GSK1521498 is a novel OR ligand, which behaves as an inverse agonist at the μ-OR sub-type. In a sample of healthy volunteers, we used [11C]-carfentanil positron emission tomography to measure the OR occupancy and functional magnetic resonance imaging (fMRI) to measure activation of brain reward centres by palatable food stimuli before and after single oral doses of GSK1521498 (range, 0.4–100 mg) or NTX (range, 2–50 mg). GSK1521498 had high affinity for human brain ORs (GSK1521498 effective concentration 50=7.10 ng ml−1) and there was a direct relationship between receptor occupancy (RO) and plasma concentrations of GSK1521498. However, for both NTX and its principal active metabolite in humans, 6-β-NTX, this relationship was indirect. GSK1521498, but not NTX, significantly attenuated the fMRI activation of the amygdala by a palatable food stimulus. We thus have shown how the pharmacological properties of OR antagonists can be characterised directly in humans by a novel integration of molecular and functional neuroimaging techniques. GSK1521498 was differentiated from NTX in terms of its pharmacokinetics, target affinity, plasma concentration–RO relationships and pharmacodynamic effects on food reward processing in the brain. Pharmacological differentiation of these molecules suggests that they may have different therapeutic profiles for treatment of overeating and other disorders of compulsive consumption.

Electrophysiological imaging of brain activity and connectivity-challenges and opportunities.

Unlocking the dynamic inner workings of the brain continues to remain a grand challenge of the 21st century. To this end, functional neuroimaging modalities represent an outstanding approach to better understand the mechanisms of both normal and abnormal brain functions. The ability to image brain function with ever increasing spatial and temporal resolution has made a significant leap over the past several decades. Further delineation of functional networks could lead to improved understanding of brain function in both normal and diseased states. This paper reviews recent advancements and current challenges in dynamic functional neuroimaging techniques, including electrophysiological source imaging, multimodal neuroimaging integrating fMRI with EEG/MEG, and functional connectivity imaging.

HIV and chronic methamphetamine dependence affect cerebral blood flow.

Human immunodeficiency virus (HIV) and methamphetamine (METH) dependence are independently associated with neuronal dysfunction. The coupling between cerebral blood flow (CBF) and neuronal activity is the basis of many task-based functional neuroimaging techniques. We examined the interaction between HIV infection and a previous history of METH dependence on CBF within the lenticular nuclei (LN). Twenty-four HIV-/METH-, eight HIV-/METH+, 24 HIV+/METH-, and 15 HIV+/METH+ participants performed a finger tapping paradigm. A multiple regression analysis of covariance assessed associations and two-way interactions between CBF and HIV serostatus and/or previous history of METH dependence. HIV+ individuals had a trend towards a lower baseline CBF (-10%, p = 0.07) and greater CBF changes for the functional task (+32%, p = 0.01) than HIV- subjects. Individuals with a previous history of METH dependence had a lower baseline CBF (-16%, p = 0.007) and greater CBF changes for a functional task (+33%, p = 0.02). However, no interaction existed between HIV serostatus and previous history of METH dependence for either baseline CBF (p = 0.53) or CBF changes for a functional task (p = 0.10). In addition, CBF and volume in the LN were not correlated. A possible additive relationship could exist between HIV infection and a history of METH dependence on CBF with a previous history of METH dependence having a larger contribution. Abnormalities in CBF could serve as a surrogate measure for assessing the chronic effects of HIV and previous METH dependence on brain function.

CS02-01 - Imaging the serotonergic system

Biological markers are an important objective in psychiatric research. Molecular and functional neuroimaging techniques are promising tools to provide these biomarkers that may be used for early detection, indication of presence and severity of psychiatric disorders, prediction of treatment response and clinical prognosis. In this lecture, recent results from molecular imaging with positron emission tomography (PET) will be presented, including cerebral quantification of several major players in serotonergic neurotransmission, i.e. the serotonin transporter, the serotonin 1A, 2A, and 1B receptor subtypes, and the degrading enzyme MAOA. Differences between psychiatric disorders will be discussed. Furthermore, pharmacological effects on these targets and brain activation will be shown using PET and functional magnetic resonance imaging (fMRI).