Impact of intraoperative hypotension and blood pressure fluctuations on early postoperative delirium after non-cardiac surgery

INTRODUCTION

Postoperative delirium is common in older patients. Despite its prognostic significance, the pathophysiology is incompletely understood. Although many risk factors have been identified, no reversible factors, particularly ones potentially modifiable by anaesthetic management, have been identified. The goal of this prospective cohort study was to investigate whether intraoperative hypotension was associated with postoperative delirium in older patients undergoing major non-cardiac surgery.

METHODS

Study subjects were patients >65 years of age, undergoing major non-cardiac surgery, who were enrolled in an ongoing prospective observational study of the pathophysiology of postoperative delirium. Intraoperative blood pressure was measured and predefined criteria were used to define hypotension. Delirium was measured by the Confusion Assessment Method on the first two postoperative days. Data were analysed using t-tests, two-sample proportion tests and ordered logistic regression multivariable models, including correction for multiple comparisons.

RESULTS

Data from 594 patients with a mean age of 73.6 years (sd 6.2) were studied. Of these 178 (30%) developed delirium on day 1 and 176 (30%) on day 2. Patients developing delirium were older, more often female, had lower preoperative cognitive scores, and underwent longer operations. Relative hypotension (decreases by 20, 30, or 40%) or absolute hypotension [mean arterial pressure (MAP)<50 mm Hg] were not significantly associated with postoperative delirium, nor was the duration of hypotension (MAP<50 mm Hg). Conversely, intraoperative blood pressure variance was significantly associated with postoperative delirium.

DISCUSSION

These results showed that increased blood pressure fluctuation, not absolute or relative hypotension, was predictive of postoperative delirium.

Qualitative and quantitative evaluation of rigid and deformable motion correction algorithms using dual-energy CT images in view of application to CT perfusion measurements in abdominal organs affected by breathing motion

OBJECTIVE

To compare six different scenarios for correcting for breathing motion in abdominal dual-energy CT (DECT) perfusion measurements.

METHODS

Rigid [RRComm(80 kVp)] and non-rigid [NRComm(80 kVp)] registration of commercially available CT perfusion software, custom non-rigid registration [NRCustom(80 kVp], demons algorithm) and a control group [CG(80 kVp)] without motion correction were evaluated using 80 kVp images. Additionally, NRCustom was applied to dual-energy (DE)-blended [NRCustom(DE)] and virtual non-contrast [NRCustom(VNC)] images, yielding six evaluated scenarios. After motion correction, perfusion maps were calculated using a combined maximum slope/Patlak model. For qualitative evaluation, three blinded radiologists independently rated motion correction quality and resulting perfusion maps on a four-point scale (4 = best, 1 = worst). For quantitative evaluation, relative changes in metric values, R(2) and residuals of perfusion model fits were calculated.

RESULTS

For motion-corrected images, mean ratings differed significantly [NRCustom(80 kVp) and NRCustom(DE), 3.3; NRComm(80 kVp), 3.1; NRCustom(VNC), 2.9; RRComm(80 kVp), 2.7; CG(80 kVp), 2.7; all p < 0.05], except when comparing NRCustom(80 kVp) with NRCustom(DE) and RRComm(80 kVp) with CG(80 kVp). NRCustom(80 kVp) and NRCustom(DE) achieved the highest reduction in metric values [NRCustom(80 kVp), 48.5%; NRCustom(DE), 45.6%; NRComm(80 kVp), 29.2%; NRCustom(VNC), 22.8%; RRComm(80 kVp), 0.6%; CG(80 kVp), 0%]. Regarding perfusion maps, NRCustom(80 kVp) and NRCustom(DE) were rated highest [NRCustom(80 kVp), 3.1; NRCustom(DE), 3.0; NRComm(80 kVp), 2.8; NRCustom(VNC), 2.6; CG(80 kVp), 2.5; RRComm(80 kVp), 2.4] and had significantly higher R(2) and lower residuals. Correlation between qualitative and quantitative evaluation was low to moderate.

CONCLUSION

Non-rigid motion correction improves spatial alignment of the target region and fit of CT perfusion models. Using DE-blended and DE-VNC images for deformable registration offers no significant improvement.

ADVANCES IN KNOWLEDGE

Non-rigid algorithms improve the quality of abdominal CT perfusion measurements but do not benefit from DECT post processing.

Negative blood oxygen level dependent signals during speech comprehension

Speech comprehension studies have generally focused on the isolation and function of regions with positive blood oxygen level dependent (BOLD) signals with respect to a resting baseline. Although regions with negative BOLD signals in comparison to a resting baseline have been reported in language-related tasks, their relationship to regions of positive signals is not fully appreciated. Based on the emerging notion that the negative signals may represent an active function in language tasks, the authors test the hypothesis that negative BOLD signals during receptive language are more associated with comprehension than content-free versions of the same stimuli. Regions associated with comprehension of speech were isolated by comparing responses to passive listening to natural speech to two incomprehensible versions of the same speech: one that was digitally time reversed and one that was muffled by removal of high frequencies. The signal polarity was determined by comparing the BOLD signal during each speech condition to the BOLD signal during a resting baseline. As expected, stimulation-induced positive signals relative to resting baseline were observed in the canonical language areas with varying signal amplitudes for each condition. Negative BOLD responses relative to resting baseline were observed primarily in frontoparietal regions and were specific to the natural speech condition. However, the BOLD signal remained indistinguishable from baseline for the unintelligible speech conditions. Variations in connectivity between brain regions with positive and negative signals were also specifically related to the comprehension of natural speech. These observations of anticorrelated signals related to speech comprehension are consistent with emerging models of cooperative roles represented by BOLD signals of opposite polarity.

Amodal brain activation and functional connectivity in response to high-energy-density food cues in obesity

OBJECTIVE

The obesogenic environment is pervasive, yet only some people become obese. The aim was to investigate whether obese individuals show differential neural responses to visual and auditory food cues, independent of cue modality.

METHODS

Obese (BMI 29-41, n = 10) and lean (BMI 20-24, n = 10) females underwent fMRI scanning during presentation of auditory (spoken word) and visual (photograph) cues representing high-energy-density (ED) and low-ED foods. The effect of obesity on whole-brain activation, and on functional connectivity with the midbrain/VTA, was examined.

RESULTS

Obese compared with lean women showed greater modality-independent activation of the midbrain/VTA and putamen in response to high-ED (vs. low-ED) cues, as well as relatively greater functional connectivity between the midbrain/VTA and cerebellum (P < 0.05 corrected).

CONCLUSIONS

Heightened modality-independent responses to food cues within the midbrain/VTA and putamen, and altered functional connectivity between the midbrain/VTA and cerebellum, could contribute to excessive food intake in obese individuals.

De novo membranous nephropathy in renal allograft associated with antibody-mediated rejection and review of the literature

A 71-year-old woman with unknown renal failure etiology received living donor transplantation had normal graft function for many years. At 11 years from transplantation, she developed nephrotic syndrome. Allograft biopsy showed membranous nephropathy (MN) and C4d positivity in the peritubular capillaries, suggestive of antibody-mediated rejection. At the time of nephrosis onset, she had new donor-specific antibody positivity. The case is unusual in that the diagnosis of de novo MN is based on evidence that she had antibody-mediated rejection. De novo MN remains relatively uncommon; we have reviewed the literature on this diagnosis.

Vacuolar H+-ATPase is down-regulated by the angiogenesis-inhibitory pigment epithelium-derived factor in metastatic prostate cancer cells

The Vacuolar H+-ATPases (V-ATPases), a multi-subunits nanomotor present in all eukaryotic cells resides in the endomembranes of exocytotic and endocytotic pathways. Plasmalemmal V-ATPases have been shown to be involved in tumor cell metastasis. Pigment epithelium-derived factor (PEDF), a potent endogenous inhibitor of angiogenesis, is down-regulated in prostate cancer cells. We hypothesized that the transduction of PEDF in prostate cancer cells will down-regulate V-ATPase function; that in turn will decrease the expression of the V-ATPase accessory protein ATP6ap2 and a-subunit isoforms that target V-ATPase to the cell surface. To test these hypotheses, we used the human androgen-sensitive prostate cancer cells LNCaP, and its castration-refractory-derivative CL1 that were engineered to stably co-express the DsRed Express Fluorescent Protein with or without PEDF. To determine if PEDF down-regulates the function of V-ATPase, we measured the rate of proton fluxes (JH+) of the cytosolic and endosome/lysosome compartments. The mRNA levels for subunit-a isoforms and the ATP6ap2 were measured using quantitative reverse transcription-PCR. The results showed that PEDF expression decreased the rate of JH+ in metastatic CL1 cells without affecting JH+ in non-metastatic LNCaP cells, when studying pH(cyt). Interestingly, PEDF did not affect JH+ in endosomes/lysosomes either in metastatic cells or in non-metastatic cells. We also showed that PEDF significantly decreases the levels of a4 isoform and ATP6ap2 in metastatic CL1 cells, without affecting the levels of a4 isoform in the non-metastatic LNCaP cells. These data identify PEDF as a novel regulator of V-ATPase suggesting a new way by which PEDF may inhibit prostate tumor growth.

Pigment epithelium-derived factor expression prolongs survival and enhances the cytotoxicity of low-dose chemotherapy in castration-refractory prostate cancer

There is currently no cure for advanced castration-refractory prostate cancer (CRPC) despite the recent approval of several new therapeutic agents. We report here the anti-tumor effect of the angio-inhibitory pigment epithelium-derived factor (PEDF) in the metastatic LNCaP-derivative CRPC CL1 model and explore PEDF anti-neoplasic efficacy in combination with low-dose chemotherapy. Androgen-sensitive LNCaP and CRPC PC3 cell lines were examined as comparison. Using a retroviral expression system, we showed that PEDF limited the proliferation of all prostatic cell lines tested; an effect attributed to interleukin 8 (IL8)-CXCR1/IL8RA inhibition. PEDF also reduced the number and size of 3D tumor spheroids in vitro, but only induced cell differentiation in CRPC spheroids. Similarly, PEDF inhibited the migration of CRPC cells suggesting both anti-proliferative and anti-migratory functions. In vivo, PEDF decreased by 85% and 65% the growth of subcutaneous (s.c.) PC3 and CL1 tumors, respectively. In the CL1 orthotopic model, tumor intake with lethal metastases was found in all animals; nevertheless, PEDF prolonged the median survival of tumor-bearing mice (95% confidence interval: 53±0.001 to 57±1 days). Accordingly, PEDF delayed the emergence of skeletal-related event in intra-tibial xenografts. Next, we evaluated low-dose docetaxel (DTX; 5, 1, 0.5 mg/kg) or cyclophosphamide (CTX; 10–20 mg/kg) on established s.c. PC3 tumors that conditionally express PEDF anti-tumoral epitope/NT3. Although NT3–DTX-5 mg/kg combination was inefficient, NT3–DTX-1 mg/kg and -0.5 mg/kg inhibited by 95% and 87.8%, respectively, tumor growth compared with control and induced tumor stasis. Both NT3–CTX combinations were advantageous. Inversely, PEDF–DTX-5 mg/kg and PEDF–CTX-10 mg/kg delayed the most CL1 tumor growth (15, 11 and 5 days for PEDF–DTX-5 mg/kg, PEDF–CTX-10 mg/kg and single treatments, respectively) with elevated apoptosis and serum thrombospondin-1 as possible mechanism and marker, respectively. As well, both PEDF–CTX-10 mg/kg and PEDF–DTX-5 mg/kg prolonged significantly the survival of tumor-bearing mice compared with single treatments. Metastases were reduced in PEDF–DTX-5 mg/kg compared with other treatments, suggesting that PEDF–DTX delayed metastases formation. Our results advocate that PEDF/low-dose chemotherapy may represent a new therapeutic alternative for CRPC.

[Metaanalysis to estimate the expected drop out-rates reported in clinical trials on cataract surgery]

BACKGROUND

A realistic sample size calculation is crucial to achieve significant results in clinical trials. As an expected drop out-rate has to be included in the sample size calculation, current practice consists in the presumption of drop out-rates published in previous similar investigations. This approach may, however, result in severely over- or under-estimated sample sizes. Therefore this meta-analysis sought to aggregate the drop out-rates from published clinical trial reports on cataract surgery to derive a quantitative suggestion for the planning of future clinical trials.

METHODS

The data collection was a complete review of all prospective and retrospective studies in five journals of the years 2002-2012; trial-wise recall rates of subjects at follow-up 3, 6, 12, and 24 months after recruitment were documented. The primary endpoint of the meta-analysis was the reported drop out-rates after 6 months. 95 % confidence intervals were calculated for each trial, respectively; a median drop out-rate was estimated including its 95 % confidence interval. The drop-out-rate estimates were furthermore stratified by design characteristics of the reported studies.

RESULTS

For randomised clinical trials on cataract surgery, the median drop out-rate increased during the follow-up period of 24 months from 4 % at three months to 17 % at 24 months after recruitment; for the six-month drop out-rate a median drop-out rate of 3 % (95 % CI 0 %; 14 %) was estimated.

CONCLUSION

Drop out-rates in sample size calculations for clinical trials on cataract surgery were found to be over-estimated in general, ending up in the calculation of overly large patient numbers and thereby in both ethical and economic consequences. For randomised clinical trials on cataract surgery the median drop out-rate can be expected to be 5 % during a six-month follow-up and may rise up to 15 % during a 12-month trial period.

Learning not to fear: neural correlates of learned safety

The ability to recognize and properly respond to instances of protection from impending danger is critical for preventing chronic stress and anxiety-central symptoms of anxiety and affective disorders afflicting large populations of people. Learned safety encompasses learning processes, which lead to the identification of episodes of security and regulation of fear responses. On the basis of insights into the neural circuitry and molecular mechanisms involved in learned safety in mice and humans, we describe learned safety as a tool for understanding neural mechanisms involved in the pathomechanisms of specific affective disorders. This review summarizes our current knowledge on the neurobiological underpinnings of learned safety and discusses potential applications in basic and translational neurosciences.

Tissue specific arterial spin labeling fMRI: a superior method for imaging cerebral blood flow in aging and disease

Cerebral blood flow (CBF) is a physiological correlate of brain function and metabolism and as such an essential parameter for investigating how aging and disease affect the brain. Arterial spin labeling (ASL) is an fMRI method that provides absolute measurement of CBF non-invasively and with higher spatial resolution than non-MRI methods. However, application of ASL in older populations is hampered by partial volume effects (PVE) and tissue dependent changes in CBF. We have developed a tissue-specific ASL method (ts-ASL) that provides `flow density' measures by quantifying CBF for each tissue separately and independently of tissue content. Using simulated functional and structural images, we investigated the effects of brain atrophy and random noise on the SNR of GM CBF measured with conventional and ts-ASL. Results showed that: (1) For all noise levels, the SNR of ts-ASL was higher. For example, for a random Gaussian noise with standard deviation σ = 4, the SNR of GM CBF obtained with ts-ASL was ~3 times higher than the SNR of the conventional method. (2) In contrast to conventional ASL, which was substantially affected by brain atrophy, ts-ASL was virtually independent of it. (3) The sensitivity of ts-ASL for detecting focal changes in CBF (ΔCBF) in the presence of atrophy and noise was also higher compared to the conventional method. In hippocampus, for 15% atrophy and Gaussian noise with σ = 4, conventional and ts-ASL retrieved 73% and 90% of the modeled ΔCBF, respectively. Taken together, these results indicate that ts-ASL may be better suited for measuring CBF in the presence of atrophy and random noise, both of which are expected to increase with aging and disease.

Shared space, separate processes: Neural activation patterns for auditory description and visual object naming in healthy adults

Historically, both clinicians and cognitive scientists have used visual object naming measures to study naming, and lesion-type studies have implicated the left posterior, temporo-parietal region as a critical component of naming circuitry. However, recent results from behavioral and cortical stimulation studies using auditory description naming as well as visual object naming in left temporal lobe epilepsy patients suggest that discrete sites in anterior temporal cortex are critical for description naming, whereas posterior temporal regions mediate both visual object naming and description naming. To determine whether this task specificity reflects normal cerebral organization and processing, 13 healthy adults performed description naming and visual naming during functional neuroimaging. In addition to standard univariate analysis, multivariate, ordinal trend analysis examined the network character of the regions involved in task-specific naming. Univariate analysis indicated posterior temporal activation for both visual naming and description naming, whereas multivariate analysis revealed broader networks for both tasks, with both overlapping and task-specific regions, as well as task-related differences in the way the tasks utilized common regions. Additionally, multivariate analysis revealed unique, task-specific, regionally covarying activation patterns that were strikingly consistent in all 13 subjects for visual naming and 12/13 subjects for description naming. Results suggest a common neural substrate, yet differentiable neural processes underlying visual naming and description naming in neurologically intact individuals. These findings support the use of both types of tasks for clinical assessment and may have application in the treatment of neurologically based naming deficits. Inc.

[Men with type 2 diabetes and erectile dysfunction are a particular risk group for LUTS - results of the Witten Diabetes Survey]

INTRODUCTION

According to our data on 4 071 patients with type 2 diabetes, 65.5% of the men and 70.4% of the women complain of lower urinary tract symptoms (LUTS). That is twice as much as the normal population for the same age group. The most common symptom was overactive bladder (OAB). In patients with a diabetes-related complication such as retinopathy or nephropathy, the incidence for LUTS was about 20% higher than that in patients without complications, whereas in men with diabetes mellitus type 2 and erectile dysfunction (ED) the incidence for LUTS was 31.9% higher than without ED. We wanted to compare the incidence of LUTS in patients with type 2 diabetes and ED against patients without ED as well as women with type 2 diabetes.

RESULTS

Men with ED had a statistically significant longer history of diabetes, a higher HbA1c and increased serum creatinine compared to men without ED (p value <0.0001). The length of diabetes history was not statistically relevant compared to women with type 2 diabetes. However the HbA1c and serum creatinine were higher than those of the women from the data bank (p value <0.0001). Diabetic men with ED complained more often of urinary incontinence, urge incontinence and made more often use of incontinence pads (p value <0.0001). As for pollakisuria and nocturia the difference was not significant. 42.3% of type 2 diabetic patients with ED were diagnosed with OAB by their urologist or GP. That was significantly more than type 2 diabetic patients without ED and type 2 diabetic women (see graph). The same was true of stress incontinence, overflow incontinence and non-classified incontinence with the exception of faecal incontinence. Patients with type 2 diabetes and ED had to take drugs more often than type 2 diabetic men without ED and women with diabetes.

CONCLUSION

Amongst patients with type 2 diabetes, ED increases the risk of developing lower urinary tract disorders. Moreover it is connected with a higher HbA1c and a higher risk for LUTS, especially for OAB. The regular use of incontinence pads in every fourth patient with type 2 diabetes and erectile dysfunction demonstrates a high number of under-treated patients. Patients with type 2 diabetes and especially patients with type 2 diabetes AND erectile dysfunction represent a risk group that needs special attention and a special management plan from urologists and GPs.

Dynamic coupling between the lateral occipital-cortex, default-mode, and frontoparietal networks during bistable perception

The lateral occipital cortex (LOC), a visual area known to be involved in object recognition, was dynamically coupled with each of two distributed patterns of neural activity depending upon the percept (default or alternative) elicited by a bistable figure. The two distributed patterns included core nodes of the default-mode and frontoparietal networks (FPN), and they were most highly coupled to each other during the alternative percept, whereas they were less coupled during the default percept. Surprisingly, the regions associated with the nonengaged percept exhibited the highest connectivity to the LOC. Together, these findings reveal a dynamic organization between the default mode and the FPNs, and the incoming bottom-up visual stream during perceptual binding of visual images.

Effects of reduced weight maintenance and leptin repletion on functional connectivity of the hypothalamus in obese humans

Treating obesity has proven to be an intractable challenge, in part, due to the difficulty of maintaining reduced weight. In our previous studies of in-patient obese subjects, we have shown that leptin repletion following a 10% or greater weight loss reduces many of the metabolic (decreased energy expenditure, sympathetic nervous system tone, and bioactive thyroid hormones) and behavioral (delayed satiation) changes that favor regain of lost weight. FMRI studies of these same subjects have shown leptin-sensitive increases in activation of the right hypothalamus and reduced activation of the cingulate, medial frontal and parahippocampal gryi, following weight loss, in response to food stimuli. In the present study, we expanded our cohort of in-patient subjects and employed psychophysiological interaction (PPI) analysis to examine changes in the functional connectivity of the right hypothalamus. During reduced-weight maintenance with placebo injections, the functional connectivity of the hypothalamus increased with visual areas and the dorsal anterior cingulate (dorsal ACC) in response to food cues, consistent with higher sensitivity to food. During reduced-weight maintenance with leptin injections, however, the functional connectivity of the right hypothalamus increased with the mid-insula and the central and parietal operculae, suggesting increased coupling with the interoceptive system, and decreased with the orbital frontal cortex, frontal pole and the dorsal ACC, suggesting a down-regulated sensitivity to food. These findings reveal neural mechanisms that may underlie observed changes in sensitivity to food cues in the obese population during reduced-weight maintenance and leptin repletion.

Gray matter abnormalities in social anxiety disorder: primary, replication, and specificity studies

BACKGROUND

Despite increasing evidence that neuroanatomical abnormalities underlie pathological anxiety, social anxiety disorder (SAD)-although among the most common of anxiety disorders-has received little attention. With magnetic resonance imaging, we: 1) examined gray matter (GM) differences between generalized SAD and healthy control groups; 2) retested the findings in an independent clinical sample; and 3) tested for specificity by contrasting the SAD group to a separate group of panic disorder (PD) subjects.

METHODS

The primary SAD group (n = 16) was required to meet DSM-IV criteria for SAD, with onset by age 30 years; control subjects (n = 20) had no lifetime history of anxiety. The replication sample included 17 generalized SAD and 17 control subjects. The PD comparison group (n = 16) was required to have no lifetime SAD. Images were acquired on a 1.5-Tesla GE Signa magnetic resonance imaging scanner with a three-dimensional T1-weighted spoiled gradient recalled pulse sequence. Morphological differences were determined with voxel-based morphometry, in SPM8.

RESULTS

After adjusting for age, gender, and total intracranial volume, SAD (as compared with control) subjects had greater GM in the left parahippocampal and middle occipital, and bilateral supramarginal and angular cortices, and left cerebellum; and lower GM in bilateral temporal poles and left lateral orbitofrontal cortex. Cerebellar, parahippocampal, and temporal pole differences were observed in both samples, survived whole brain corrections, and were not observed in the PD group, pointing to relative specificity to SAD.

CONCLUSIONS

These findings parallel the functional literature on SAD and suggest structural abnormalities underlying the functional disturbances.

Conceptual representations of perceptual knowledge

Many neuroimaging studies of semantic memory have argued that knowledge of an object's perceptual properties are represented in a modality-specific manner. These studies often base their argument on finding activation in the left-hemisphere fusiform gyrus-a region assumed to be involved in perceptual processing-when the participant is verifying verbal statements about objects and properties. In this paper, we report an extension of one of these influential papers-Kan, Barsalou, Solomon, Minor, and Thompson-Schill (2003 )-and present evidence for an amodal component in the representation and processing of perceptual knowledge. Participants were required to verify object-property statements (e.g., "cat-whiskers?"; "bear-wings?") while they were being scanned by functional magnetic resonance imaging (fMRI). We replicated Kan et al.'s activation in the left fusiform gyrus, but also found activation in regions of left inferior frontal gyrus (IFG) and middle-temporal gyrus, areas known to reflect amodal processes or representations. Further, only activations in the left IFG, an amodal area, were correlated with measures of behavioural performance.

Frontal-occipital connectivity during visual search

Although expectation- and attention-related interactions between ventral and medial prefrontal cortex and stimulus category-selective visual regions have been identified during visual detection and discrimination, it is not known if similar neural mechanisms apply to other tasks such as visual search. The current work tested the hypothesis that high-level frontal regions, previously implicated in expectation and visual imagery of object categories, interact with visual regions associated with object recognition during visual search. Using functional magnetic resonance imaging, subjects searched for a specific object that varied in size and location within a complex natural scene. A model-free, spatial-independent component analysis isolated multiple task-related components, one of which included visual cortex, as well as a cluster within ventromedial prefrontal cortex (vmPFC), consistent with the engagement of both top-down and bottom-up processes. Analyses of psychophysiological interactions showed increased functional connectivity between vmPFC and object-sensitive lateral occipital cortex (LOC), and results from dynamic causal modeling and Bayesian Model Selection suggested bidirectional connections between vmPFC and LOC that were positively modulated by the task. Using image-guided diffusion-tensor imaging, functionally seeded, probabilistic white-matter tracts between vmPFC and LOC, which presumably underlie this effective interconnectivity, were also observed. These connectivity findings extend previous models of visual search processes to include specific frontal-occipital neuronal interactions during a natural and complex search task.

Sleep restriction leads to increased activation of brain regions sensitive to food stimuli

BACKGROUND

Epidemiologic evidence shows an increase in obesity concurrent with a reduction in average sleep duration among Americans. Although clinical studies propose that restricted sleep affects hormones related to appetite, neuronal activity in response to food stimuli after restricted and habitual sleep has not been investigated.

OBJECTIVE

The objective of this study was to determine the effects of partial sleep restriction on neuronal activation in response to food stimuli.

DESIGN

Thirty healthy, normal-weight [BMI (in kg/m²): 22-26] men and women were recruited (26 completed) to participate in a 2-phase inpatient crossover study in which they spent either 4 h/night (restricted sleep) or 9 h/night (habitual sleep) in bed. Each phase lasted 6 d, and functional magnetic resonance imaging was performed in the fasted state on day 6.

RESULTS

Overall neuronal activity in response to food stimuli was greater after restricted sleep than after habitual sleep. In addition, a relative increase in brain activity in areas associated with reward, including the putamen, nucleus accumbens, thalamus, insula, and prefrontal cortex in response to food stimuli, was observed.

CONCLUSION

The findings of this study link restricted sleep and susceptibility to food stimuli and are consistent with the notion that reduced sleep may lead to greater propensity to overeat.

Decoding unattended fearful faces with whole-brain correlations: an approach to identify condition-dependent large-scale functional connectivity

Processing of unattended threat-related stimuli, such as fearful faces, has been previously examined using group functional magnetic resonance (fMRI) approaches. However, the identification of features of brain activity containing sufficient information to decode, or "brain-read", unattended (implicit) fear perception remains an active research goal. Here we test the hypothesis that patterns of large-scale functional connectivity (FC) decode the emotional expression of implicitly perceived faces within single individuals using training data from separate subjects. fMRI and a blocked design were used to acquire BOLD signals during implicit (task-unrelated) presentation of fearful and neutral faces. A pattern classifier (linear kernel Support Vector Machine, or SVM) with linear filter feature selection used pair-wise FC as features to predict the emotional expression of implicitly presented faces. We plotted classification accuracy vs. number of top N selected features and observed that significantly higher than chance accuracies (between 90-100%) were achieved with 15-40 features. During fearful face presentation, the most informative and positively modulated FC was between angular gyrus and hippocampus, while the greatest overall contributing region was the thalamus, with positively modulated connections to bilateral middle temporal gyrus and insula. Other FCs that predicted fear included superior-occipital and parietal regions, cerebellum and prefrontal cortex. By comparison, patterns of spatial activity (as opposed to interactivity) were relatively uninformative in decoding implicit fear. These findings indicate that whole-brain patterns of interactivity are a sensitive and informative signature of unattended fearful emotion processing. At the same time, we demonstrate and propose a sensitive and exploratory approach for the identification of large-scale, condition-dependent FC. In contrast to model-based, group approaches, the current approach does not discount the multivariate, joint responses of multiple functional connections and is not hampered by signal loss and the need for multiple comparisons correction.

Cortical functional connectivity decodes subconscious, task-irrelevant threat-related emotion processing

It is currently unclear to what extent cortical structures are required for and engaged during subconscious processing of biologically salient affective stimuli (i.e. the 'low-road' vs. 'many-roads' hypotheses). Here we show that cortical-cortical and cortical-subcortical functional connectivity (FC) contain substantially more information, relative to subcortical-subcortical FC (i.e. 'subcortical alarm' and other limbic regions), that predicts subliminal fearful face processing within individuals using training data from separate subjects. A plot of classification accuracy vs. number of selected whole-brain FC features revealed 92% accuracy when learning was based on the top 8 features from each training set. The most informative FC was between right amygdala and precuneus, which increased during subliminal fear conditions, while left and right amygdala FC decreased, suggesting a bilateral decoupling of this key limbic region during processing of subliminal fear-related stimuli. Other informative FC included angular gyrus, middle temporal gyrus and cerebellum. These findings identify FC that decodes subliminally perceived, task-irrelevant affective stimuli, and suggest that cortical structures are actively engaged by and appear to be essential for subliminal fear processing.

Relation between changes in neural responsivity and reductions in desire to eat high-calorie foods following gastric bypass surgery

Reductions in reward-related (e.g. striatal) neural activation have been noted following obesity surgery. It has been speculated that these postoperative neural changes may be related to documented postoperative changes in food preferences; however, this relation has not been previously established. In this study, functional magnetic resonance imaging and rating scales were used to assess neural responsivity, desire to eat (i.e. wanting), and liking for high- and low-calorie food cues in 14 females one month pre- and one month post-Roux-en-Y gastric bypass (RYGB) surgery. Pre- to post-RYGB changes in all variables were assessed, and postoperative changes in neural responsivity were regressed on postoperative changes in desire to eat and liking of foods. Results revealed significant postoperative reductions in mesolimbic (e.g. striatal) neural responsivity, desire to eat (wanting), and liking for high- relative to low-calorie food cues. Postoperative reductions in mesolimbic responsivity were associated with postoperative reductions in wanting, but not liking, for high- versus low-calorie foods. Interestingly, reductions in food wanting were also related to reductions in inhibitory (e.g. dorsolateral prefrontal cortex) activation following RYGB. Results are consistent with the hypothesized delineation between wanting and liking, supporting the notion that wanting, but not liking, is processed through the dopaminergic reward pathway. Concurrent reductions in both reward-related and inhibitory activation-predicted reductions in desire to eat might suggest that less dietary inhibition was elicited to resist potential overconsumption as the anticipated reward value of high-calorie foods decreased following RYGB.