Moral competence and brain connectivity: A resting-state fMRI study.

Moral competence (MC) refers to the ability to apply certain moral orientations in a consistent and differentiated manner when judging moral issues. People greatly differ in terms of MC, however, little is known about how these differences are implemented in the brain. To investigate this question, we used functional magnetic resonance imaging and examined resting-state functional connectivity (RSFC) in n=31 individuals with MC scores in the highest 15% of the population and n=33 individuals with MC scores in the lowest 15%, selected from a large sample of 730 Master of Business Administration (MBA) students. Compared to individuals with lower MC, individuals with higher MC showed greater amygdala-ventromedial prefrontal connectivity, which may reflect better ability to cope with emotional conflicts elicited by moral dilemmas. Moreover, individuals with higher MC showed less inter-network connectivity between the amygdalar and fronto-parietal networks, suggesting a more independent operation of these networks. Our findings provide novel insights into how individual differences in moral judgment are associated with RSFC in brain circuits related to emotion processing and cognitive control.

Assessment of risk-taking and impulsive behaviors: A comparison between three tasks.

The balloon analogue risk task (BART), the delay discounting task (DDT), and the Iowa gambling task (IGT) are increasingly used for the assessment of risk-taking and impulsive behaviors. This study examined the reliability of and relationships between these three tasks in healthy Chinese subjects. The BART and DDT showed moderate to high test-retest reliability across three test sessions. However, the IGT showed low reliability for the first two sessions but high reliability for the last two sessions. Between tasks, only the BART and IGT showed significant correlations at the last two sessions, while no other correlations were found. These findings support the view that impulsivity is a complex construct with no single personality trait underlying the disposition for impulsive behaviors.

Direct comparison of fluorodeoxyglucose positron emission tomography and arterial spin labeling magnetic resonance imaging in Alzheimer's disease.

BACKGROUND: The utility of fluorodeoxyglucose positron emission tomography (FDG-PET) imaging in Alzheimer's disease (AD) diagnosis has been well established. Recently, measurement of cerebral blood flow using arterial spin labeling magnetic resonance imaging (ASL-MRI) has shown diagnostic potential in AD, although it has never been directly compared with FDG-PET. METHODS: We used a novel imaging protocol to obtain FDG-PET and ASL-MRI images concurrently in 17 AD patients and 19 age-matched control subjects. Paired FDG-PET and ASL-MRI images from 19 control subjects and 15 AD patients were included for qualitative analysis, and paired images from 18 control subjects and 13 AD patients were suitable for quantitative analyses. RESULTS: The combined imaging protocol was well tolerated. Both modalities revealed similar regional abnormalities in AD, as well as comparable sensitivity and specificity for the detection of AD after visual review by two expert readers. Interobserver agreement was better for FDG-PET (κ: 0.75, standard error: 0.12) than ASL-MRI (κ: 0.51, standard error: 0.15); intermodality agreement was moderate to strong (κ: 0.45-0.61); and readers were more confident of FDG-PET reads. Simple quantitative analysis of global cerebral fluorodeoxyglucose uptake (FDG-PET) or whole-brain cerebral blood flow (ASL-MRI) showed excellent diagnostic accuracy for both modalities, with area under receiver operating characteristic curves of 0.90 for FDG-PET (95% confidence interval: 0.79-0.99) and 0.91 for ASL-MRI (95% confidence interval: 0.80-1.00). CONCLUSIONS: Our results demonstrate that FDG-PET and ASL-MRI identify similar regional abnormalities and have comparable diagnostic accuracy in a small population of AD patients, and support the further study of ASL-MRI in dementia diagnosis.

Heterogeneity of functional activation during memory encoding across hippocampal subfields in temporal lobe epilepsy.

Pathology studies have shown that the anatomical subregions of the hippocampal formation are differentially affected in various neurological disorders, including temporal lobe epilepsy (TLE). Analysis of structure and function within these subregions using magnetic resonance imaging (MRI) has the potential to generate insights on disease associations as well as normative brain function. In this study, an atlas-based normalization method (Yushkevich, P.A., Avants, B.B., Pluta, J., Das, S., Minkoff, D., Mechanic-Hamilton, D., Glynn, S., Pickup, S., Liu, W., Gee, J.C., Grossman, M., Detre, J.A., 2009. A high-resolution computational atlas of the human hippocampus from postmortem magnetic resonance imaging at 9.4 T. NeuroImage 44 (2), 385-398) was used to label hippocampal subregions, making it possible to examine subfield-level functional activation during an episodic memory task in two different cohorts of healthy controls and subjects diagnosed with intractable unilateral TLE. We report, for the first time, functional activation patterns within hippocampal subfields in TLE. We detected group differences in subfield activation between patients and controls as well as inter-hemispheric activation asymmetry within subfields in patients, with dentate gyrus (DG) and the anterior hippocampus region showing the greatest effects. DG was also found to be more active than CA1 in controls, but not in patients' epileptogenic side. These preliminary results will encourage further research on the utility of subfield-based biomarkers in TLE.

Cerebral blood flow changes associated with different meditation practices and perceived depth of meditation.

Our goal in this study was to advance the understanding of the neural pathways of meditation by addressing the cerebral blood flow (CBF) responses associated with two different meditation practices performed by the same individuals and how such changes related to the "stress" circuits in the brain. Ten experienced meditators performed two types of meditation, a "focused-based" practice and a "breath-based" practice. Subjects were scanned using perfusion functional magnetic resonance imaging (fMRI) during a baseline state, both meditation states, and a post meditation baseline state. Using general linear model, we found that the frontal regions, anterior cingulate, limbic system and parietal lobes were affected during meditation and that there were different patterns of CBF between the two meditation states. We observed strong correlations between depth of meditation and neural activity in the left inferior forebrain areas including the insula, inferior frontal cortex, and temporal pole. There were persistent changes in the left anterior insula and the precentral gyrus even after meditation was stopped. This study revealed changes in the brain during two different meditation practices in the same individuals and that these changes correlated with the subjective experiences of the practitioners.

The optimal template effect in hippocampus studies of diseased populations.

We evaluate the impact of template choice on template-based segmentation of the hippocampus in epilepsy. Four dataset-specific strategies are quantitatively contrasted: the "closest to average" individual template, the average shape version of the closest to average template, a best appearance template and the best appearance and shape template proposed here and implemented in the open source toolkit Advanced Normalization Tools (ANTS). The cross-correlation similarity metric drives the correspondence model and is used consistently to determine the optimal appearance. Minimum shape distance in the diffeomorphic space determines optimal shape. Our evaluation results show that, with respect to gold-standard manual labeling of hippocampi in epilepsy, optimal shape and appearance template construction outperforms the other strategies for gaining data-derived templates. Our results also show the improvement is most significant on the diseased side and insignificant on the healthy side. Thus, the importance of the template increases when used to study pathology and may be less critical for normal control studies. Furthermore, explicit geometric optimization of the shape component of the unbiased template positively impacts the study of diseased hippocampi.

Early parental care is important for hippocampal maturation: evidence from brain morphology in humans.

The effects of early life experience on later brain structure and function have been studied extensively in animals, yet the relationship between childhood experience and normal brain development in humans remains largely unknown. Using a unique longitudinal data set including ecologically valid in-home measures of early experience during childhood (at age 4 and 8 years) and high-resolution structural brain imaging during adolescence (mean age 14 years), we examined the effects on later brain morphology of two dimensions of early experience: parental nurturance and environmental stimulation. Parental nurturance at age 4 predicts the volume of the left hippocampus in adolescence, with better nurturance associated with smaller hippocampal volume. In contrast, environmental stimulation did not correlate with hippocampal volume. Moreover, the association between hippocampal volume and parental nurturance disappears at age 8, supporting the existence of a sensitive developmental period for brain maturation. These findings indicate that variation in normal childhood experience is associated with differences in brain morphology, and hippocampal volume is specifically associated with early parental nurturance. Our results provide neuroimaging evidence supporting the important role of warm parental care during early childhood for brain maturation.

Structure specific analysis of the hippocampus in temporal lobe epilepsy.

The hippocampus is a major structure of interest affected by temporal lobe epilepsy (TLE). Region of interest (ROI)-based analysis has traditionally been used to study hippocampal involvement in TLE, although spatial variation of structural and functional pathology have been known to exist within the ROI. In this article, structure-specific analysis (Yushkevich et al. (2007) Neuroimage 35:1516-1530) is applied to the study of both structure and function in TLE patients. This methodology takes into account information about the spatial correspondence of voxels within ROIs on left and right sides of the same subject as well as between subjects. Hippocampal thickness is studied as a measure of structural integrity, and functional activation in a functional magnetic resonance imaging (fMRI) experiment in which subjects performed a memory encoding task is studied as a measure of functional integrity. Pronounced disease-related decrease in thickness is found in posterior and anterior hippocampus. A region in the body also shows increased thickness in patients' healthy hippocampi compared with controls. Functional activation in diseased hippocampi is reduced in the body region compared to controls, whereas a region in the tail showing greater right-lateralized activation in controls also shows greater activation in healthy hippocampi compared with the diseased side in patients. Summary measurements generated by integrating quantities of interest over the entire hippocampus can also be used, as is done in conventional ROI analysis.

Hippocampal volumetry and functional MRI of memory in temporal lobe epilepsy.

This study examined the utility of structural and functional MRI at 1.5 and 3T in the presurgical evaluation and prediction of postsurgical cognitive outcome in temporal lobe epilepsy (TLE). Forty-nine patients undergoing presurgical evaluation for temporal lobe (TL) resection and 25 control subjects were studied. Patients completed standard presurgical evaluations, including the intracarotid amobarbital test (IAT) and neuropsychological testing. During functional imaging, subjects performed a complex visual scene-encoding task. High-resolution structural MRI scans were used to quantify hippocampal volumes. Both structural and functional imaging successfully lateralized the seizure focus and correlated with IAT memory lateralization, with improvement for functional imaging at 3T as compared with 1.5 T. Ipsilateral structural and functional MRI data were related to cognitive outcome, and greater functional asymmetry was related to earlier age at onset. These findings support continued investigation of the utility of MRI and fMRI in the presurgical evaluation of TLE.

Neural correlates of voluntary and involuntary risk taking in the human brain: an fMRI Study of the Balloon Analog Risk Task (BART).

Increasing effort has been devoted to understanding the neural mechanisms underlying decision making during risk, yet little is known about the effect of voluntary choice on risk taking. The Balloon Analog Risk Task (BART), in which subjects inflate a virtual balloon that can either grow larger or explode [Lejuez, C.W., Read, J.P., Kahler, C.W., Richards, J.B., Ramsey, S.E., Stuart, G.L., Strong, D.R., Brown, R.A., 2002. Evaluation of a behavioral measure of risk taking: the Balloon Analogue Risk Task BART. J. Exp. Psychol. Appl. 8, 75-84.], provides an ecologically valid model to assess human risk taking propensity and behaviour. In the present study, we modified this task for use during functional magnetic resonance imaging (fMRI) and administered it in both an active choice mode and a passive no-choice mode in order to examine the neural correlates of voluntary and involuntary risk taking in the human brain. Voluntary risk in the active choice task is associated with robust activation in mesolimbic-frontal regions, including the midbrain, ventral and dorsal striatum, anterior insula, dorsal lateral prefrontal cortex (DLPFC), and anterior cingulate/medial frontal cortex (ACC/MFC), in addition to activation in visual pathway regions. However, these mesolimbic-frontal activation patterns were not observed for involuntary risk in the passive no-choice task. Decision making was associated with neural activity in the right DLPFC. These findings demonstrate the utility of the modified BART paradigms for using during fMRI to assess risk taking in the human brain, and suggest that recruitment of the brain mesolimbic-frontal pathway during risk-taking is contingent upon the agency of the risk taker. The present paradigm may be extended to pathological populations to determine the specific neural components of their impaired risk behavior.

Functional magnetic resonance imaging and working memory in adolescents with gestational cocaine exposure.

OBJECTIVE: To assess the effect of gestational cocaine exposure on the prefrontal cortex (PFC) with functional magnetic resonance imaging (fMRI). STUDY DESIGN: Using an n-back task, we obtained fMRI with a 3T Siemens scanner on 49 adolescents, 25 who were exposed to cocaine and 24 who were not exposed. The primary outcome was PFC activation during task performance. Five functionally derived regions of interest (ROI) were defined; in addition, 2 a priori anatomical ROIs were generated for Brodmann regions 10 and 46. RESULTS: Of the 49 adolescents who underwent imaging, data from 17 who were exposed to cocaine and 17 who were not exposed were in the final analysis. Groups had similar performance on the n-back task (P >/= .4), with both showing a fewer number of correct responses on the 2-back than the 1-back (P < .001), indicating increased demands on working memory with greater task difficulty. In functionally derived ROIs, imaging results showed increased activation for both groups in the 2-back versus the 1-back condition. In anatomical ROIs, both groups showed greater activation in the 2-back versus the 1-back condition, with activation in the non-exposed group proportionally greater for the left prefrontal region (P = .05). CONCLUSION: In this sample of adolescents, participants who were exposed to cocaine and participants who were not exposed were similar in performance on an executive function task and in fMRI activation patterns during task performance.

Combination antiretroviral therapy modulates the blood oxygen level-dependent amplitude in human immunodeficiency virus-seropositive patients.

Combination antiretroviral therapy (cART) limits human immunodeficiency virus (HIV) replication in the central nervous system (CNS) and prevents progressive neurological dysfunction. We examined if the degree of CNS penetration by cART, as estimated by the CNS penetration effectiveness (CPE) score, affects brain activity as measured by the amplitude of the blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) response. HIV+ patients on low-CPE cART (n=12) had a significantly greater BOLD fMRI response amplitude than HIV+ patients on high-CPE cART (n=12) or seronegative controls (n=10). An increase in the BOLD fMRI response in HIV patients on low-CPE cART may reflect continued HIV replication in the CNS leading to increased oxidative stress and associated metabolic demands.

Genetic variation in serotonin transporter alters resting brain function in healthy individuals.

BACKGROUND: Perfusion functional magnetic resonance imaging (fMRI) was used to investigate the effect of genetic variation of the human serotonin transporter (5-HTT) gene (5-HTTLPR, SLC6A4) on resting brain function of healthy individuals. METHODS: Twenty-six healthy subjects, half homozygous for the 5-HTTLPR short allele (s/s group) and half homozygous for the long allele (l/l group), underwent perfusion functional and structural magnetic resonance imaging during a resting state. The two genotype groups had no psychiatric illness and were similar in age, gender, and personality scores. RESULTS: Compared with the l/l group, the s/s group showed significantly increased resting cerebral blood flow (CBF) in the amygdala and decreased CBF in the ventromedial prefrontal cortex. The effect of functional modulation in these regions by 5-HTTLPR genotype cannot be accounted for by variations in brain anatomy, personality, or self-reported mood. CONCLUSIONS: The 5-HTTLPR genotype alters resting brain function in emotion-related regions in healthy individuals, including the amygdala and ventromedial prefrontal cortex. Such alterations suggest a broad role of the 5-HTT gene in brain function that may be associated with the genetic susceptibility for mood disorders such as depression.

Canine and human visual cortex intact and responsive despite early retinal blindness from RPE65 mutation.

BACKGROUND: RPE65 is an essential molecule in the retinoid-visual cycle, and RPE65 gene mutations cause the congenital human blindness known as Leber congenital amaurosis (LCA). Somatic gene therapy delivered to the retina of blind dogs with an RPE65 mutation dramatically restores retinal physiology and has sparked international interest in human treatment trials for this incurable disease. An unanswered question is how the visual cortex responds after prolonged sensory deprivation from retinal dysfunction. We therefore studied the cortex of RPE65-mutant dogs before and after retinal gene therapy. Then, we inquired whether there is visual pathway integrity and responsivity in adult humans with LCA due to RPE65 mutations (RPE65-LCA). METHODS AND FINDINGS: RPE65-mutant dogs were studied with fMRI. Prior to therapy, retinal and subcortical responses to light were markedly diminished, and there were minimal cortical responses within the primary visual areas of the lateral gyrus (activation amplitude mean +/- standard deviation [SD] = 0.07% +/- 0.06% and volume = 1.3 +/- 0.6 cm(3)). Following therapy, retinal and subcortical response restoration was accompanied by increased amplitude (0.18% +/- 0.06%) and volume (8.2 +/- 0.8 cm(3)) of activation within the lateral gyrus (p < 0.005 for both). Cortical recovery occurred rapidly (within a month of treatment) and was persistent (as long as 2.5 y after treatment). Recovery was present even when treatment was provided as late as 1-4 y of age. Human RPE65-LCA patients (ages 18-23 y) were studied with structural magnetic resonance imaging. Optic nerve diameter (3.2 +/- 0.5 mm) was within the normal range (3.2 +/- 0.3 mm), and occipital cortical white matter density as judged by voxel-based morphometry was slightly but significantly altered (1.3 SD below control average, p = 0.005). Functional magnetic resonance imaging in human RPE65-LCA patients revealed cortical responses with a markedly diminished activation volume (8.8 +/- 1.2 cm(3)) compared to controls (29.7 +/- 8.3 cm(3), p < 0.001) when stimulated with lower intensity light. Unexpectedly, cortical response volume (41.2 +/- 11.1 cm(3)) was comparable to normal (48.8 +/- 3.1 cm(3), p = 0.2) with higher intensity light stimulation. CONCLUSIONS: Visual cortical responses dramatically improve after retinal gene therapy in the canine model of RPE65-LCA. Human RPE65-LCA patients have preserved visual pathway anatomy and detectable cortical activation despite limited visual experience. Taken together, the results support the potential for human visual benefit from retinal therapies currently being aimed at restoring vision to the congenitally blind with genetic retinal disease.

Detection of human immunodeficiency virus induced inflammation and oxidative stress in lenticular nuclei with magnetic resonance spectroscopy despite antiretroviral therapy.

BACKGROUND: Single-voxel magnetic resonance spectroscopy measurements of N-acetyl aspartate, choline, and creatine (Cr) are affected in patients with human immunodeficiency virus (HIV) and neurocognitive impairment. However, these metabolic markers are often normalized in affected central nervous system regions, such as the lenticular nuclei, after initiation of highly active antiretroviral therapy (HAART). OBJECTIVE: To examine whether lactate (Lac), a marker of inflammation and anaerobic glycolysis, and lipid, an indicator of cell membrane turnover resulting from oxidative stress, could serve as surrogate biomarkers within the lenticular nuclei of HIV-positive patients with different degrees of neurocognitive impairment. DESIGN: Three-tesla 2-dimensional-chemical shift imaging magnetic resonance spectroscopy at echo times of 30 milliseconds and 135 milliseconds was performed in voxels overlapping the lenticular nuclei of seronegative controls and a spectrum of HIV-positive patients (neurocognitively normal, mildly impaired, or moderately to severely impaired). SETTING: University of Pennsylvania, Philadelphia. PARTICIPANTS: Ten seronegative controls and 45 HIV-positive patients with different degrees of neurocognitive impairment (15 neurocognitively normal patients, 12 mildly impaired patients, and 18 moderately to severely impaired patients). MAIN OUTCOME MEASURES: In vivo 2-dimensional-chemical shift imaging magnetic resonance spectroscopy analysis of N-acetyl aspartate:Cr, choline:Cr, Lac:Cr, and (lipid + Lac):Cr ratios among the various groups. In addition, the effect of the degree of HAART central nervous system penetration (high vs low) on these ratios was studied. RESULTS: No significant lenticular nuclei atrophy was detected with volumes similar across all of the groups. Both N-acetyl aspartate:Cr and choline:Cr ratios were similar across all of the groups at either echo time. In contrast, the Lac:Cr ratio was significantly greater in HIV-positive patients with moderate to severe impairment compared with seronegative controls. The (lipid + Lac):Cr ratio was significantly elevated within each HIV-positive subgroup compared with seronegative controls. Within HIV-positive patients receiving HAART, the degree of central nervous system penetration (high vs low) did not affect metabolic ratios. CONCLUSIONS: As seen with 2-dimensional-chemical shift imaging magnetic resonance spectroscopy, HIV induces inflammation and oxidative stress in HIV-positive patients despite HAART. Lipid and Lac are more sensitive inflammatory biomarkers that may be used to differentiate HIV-positive subgroups. However, no significant difference in efficacy, as measured by metabolic ratios, exists for high- vs low-central nervous system-penetrating HAART.

Post-conventional moral reasoning is associated with increased ventral striatal activity at rest and during task.

People vary considerably in moral reasoning. According to Kohlberg's theory, individuals who reach the highest level of post-conventional moral reasoning judge moral issues based on deeper principles and shared ideals rather than self-interest or adherence to laws and rules. Recent research has suggested the involvement of the brain's frontostriatal reward system in moral judgments and prosocial behaviors. However, it remains unknown whether moral reasoning level is associated with differences in reward system function. Here, we combined arterial spin labeling perfusion and blood oxygen level-dependent functional magnetic resonance imaging and measured frontostriatal reward system activity both at rest and during a sequential risky decision making task in a sample of 64 participants at different levels of moral reasoning. Compared to individuals at the pre-conventional and conventional level of moral reasoning, post-conventional individuals showed increased resting cerebral blood flow in the ventral striatum and ventromedial prefrontal cortex. Cerebral blood flow in these brain regions correlated with the degree of post-conventional thinking across groups. Post-conventional individuals also showed greater task-induced activation in the ventral striatum during risky decision making. These findings suggest that high-level post-conventional moral reasoning is associated with increased activity in the brain's frontostriatal system, regardless of task-dependent or task-independent states.

Neural correlates of post-conventional moral reasoning: a voxel-based morphometry study.

Going back to Kohlberg, moral development research affirms that people progress through different stages of moral reasoning as cognitive abilities mature. Individuals at a lower level of moral reasoning judge moral issues mainly based on self-interest (personal interests schema) or based on adherence to laws and rules (maintaining norms schema), whereas individuals at the post-conventional level judge moral issues based on deeper principles and shared ideals. However, the extent to which moral development is reflected in structural brain architecture remains unknown. To investigate this question, we used voxel-based morphometry and examined the brain structure in a sample of 67 Master of Business Administration (MBA) students. Subjects completed the Defining Issues Test (DIT-2) which measures moral development in terms of cognitive schema preference. Results demonstrate that subjects at the post-conventional level of moral reasoning were characterized by increased gray matter volume in the ventromedial prefrontal cortex and subgenual anterior cingulate cortex, compared with subjects at a lower level of moral reasoning. Our findings support an important role for both cognitive and emotional processes in moral reasoning and provide first evidence for individual differences in brain structure according to the stages of moral reasoning first proposed by Kohlberg decades ago.

Serotonin transporter genotype modulates functional connectivity between amygdala and PCC/PCu during mood recovery.

The short (S) allele of the serotonin transporter-linked polymorphic region (5-HTTLPR) has been associated with increased susceptibility to depression. Previous neuroimaging studies have consistently showed increased amygdala activity during the presentation of negative stimuli or regulation of negative emotion in the homozygous short allele carriers, suggesting the key role of amygdala response in mediating increased risk for depression. The brain default mode network (DMN) has also been shown to modulate amygdala activity. However, it remains unclear whether 5-HTTLPR genetic variation modulates functional connectivity (FC) between the amygdala and regions of DMN. In this study, we re-analyzed our previous imaging dataset and examined the effects of 5-HTTLPR genetic variation on amygdala connectivity. A total of 15 homozygous short (S/S) and 15 homozygous long individuals (L/L) were scanned in functional magnetic resonance imaging (fMRI) during four blocks: baseline, sad mood, mood recovery, and return to baseline. The S/S and L/L groups showed a similar pattern of FC and no differences were found between the two groups during baseline and sad mood scans. However, during mood recovery, the S/S group showed significantly reduced anti-correlation between amygdala and posterior cingulate cortex/precuneus (PCC/PCu) compared to the L/L group. Moreover, PCC/PCu-amygdala connectivity correlated with amygdala activity in the S/S group but not the L/L group. These results suggest that 5-HTTLPR genetic variation modulates amygdala connectivity which subsequently affects its activity during mood regulation, providing an additional mechanism by which the S allele confers depression risk.

Imaging mesial temporal lobe activation during scene encoding: comparison of fMRI using BOLD and arterial spin labeling.

Memory encoding is a critical brain function subserved by the hippocampus (HP) and mesial temporal lobe (mTL) structures. Visualization of mTL memory activation with BOLD fMRI is complicated by the presence of static susceptibility gradients in this region. Arterial spin labeled (ASL) perfusion fMRI offers an alternative approach not dependent on susceptibility contrast that instead suffers from lower intrinsic signal-to-noise ratio. An improved ASL perfusion fMRI approach combining pseudo-continuous ASL and a T(2)*-insensitive sequence (GRASE) with background suppression was compared to BOLD fMRI at 3 T during a scene encoding task known to activate the HP. Overall, an approximate sixfold sensitivity increase of ASL fMRI was achieved, with improved coverage in the anterior mTL, while suppression of the static tissue enhanced the stability of the ASL series by a factor of 2.4. Perfusion fMRI using this approach with 4 mm isotropic resolution yielded better localized and stronger group activation maps than BOLD fMRI at a standard resolution of 3 mm isotropic voxels. Increasing the resolution for BOLD to 2.5 mm isotropic produced stronger mTL and hippocampal activation in the group and individual subjects than the ASL technique, due to superior temporal resolution and reduced partial volume effects. Future improvements in ASL spatial and temporal resolution would allow the benefits of both approaches to be combined to further enhance the sensitivity for detecting mTL activation during memory encoding.

Multivariate examination of brain abnormality using both structural and functional MRI.

A multivariate classification approach has been presented to examine the brain abnormalities, i.e., due to prenatal cocaine exposure, using both structural and functional brain images. First, a regional statistical feature extraction scheme was adopted to capture discriminative features from voxel-wise morphometric and functional representations of brain images, in order to reduce the dimensionality of the features used for classification, as well as to achieve the robustness to registration error and inter-subject variations. Then, this feature extraction method was used in conjunction with a hybrid feature selection method and a nonlinear support vector machine for the classification of brain abnormalities. This brain classification approach has been applied to detecting the brain abnormality associated with prenatal cocaine exposure in adolescents. A promising classification performance was achieved on a data set of 49 subjects (24 normal and 25 prenatally cocaine-exposed teenagers), with a leave-one-out cross-validation. Experimental results demonstrated the efficacy of our method, as well as the importance of incorporating both structural and functional images for brain classification. Moreover, spatial patterns of group difference derived from the constructed classifier were mostly consistent with the results of the conventional statistical analysis method. Therefore, the proposed approach provided not only a multivariate classification method for detecting brain abnormalities, but also an alternative way for group analysis of multimodality images.