Modulation of attentional bias by hypnotic suggestion: experimental evidence from an emotional Stroop task.

Hypnosis is considered a unique tool capable of modulating cognitive processes. The extent to which hypnotic suggestions intervenes is still under debate. This study was designed to provide a new insight into this issue, by focusing on an unintentional emotional process: attentional bias. In Experiment 1, highly suggestible participants performed three sessions of an emotional Stroop task where hypnotic suggestions aiming to increase and decrease emotional reactivity towards emotional stimuli were administered within an intra-individual design. Compared to a baseline condition (without hypnotic suggestion), a significant increase in attentional bias was found when a hypnotic suggestion to increase emotional reactivity was administered. In contrast, the bias was eliminated when a suggestion to decrease emotional reactivity was administered. Experiment 2 investigated the effect of session repetition on attentional bias across three successive experimental sessions without hypnosis, and showed that the emotional Stroop effect did not vary across sessions. Hence, session repetition could not account for part of the modulation of attentional bias in Experiment 1. Taken together, the results suggest that specific hypnotic suggestions can influence elicitation of unintentional emotional processing. The implications are discussed regarding the locus of intervention of hypnotic suggestion in cognitive and emotional processes.

Arterial hypertension and cerebral hemodynamics: impact of head-down tilt on cerebral blood flow (arterial spin-labeling-MRI) in healthy and hypertensive patients.

OBJECTIVE: Hypertension affects cerebrovascular autoregulation and increases the risk of cerebrovascular events and dementia. Notably, it is associated with cerebrovascular remodeling and lower resting cerebral blood flow (CBF). We wanted to determine, using arterial spin-labeling-MRI, the impact of a head-down tilt (HDT) dynamic maneuver on CBF in hypertensive patients. METHODS: The current prospective study measured 36 patients' CBFs (18 normotensive individuals; 18 hypertensive patients) on 1.5T arterial spin-labeling-MRI in the supine position and after 4 min at -15° HDT. We reconstructed CBF maps of left and right subcortical nuclear gray matter, cortical gray matter and white matter (16 structures) to explore cerebrovascular autoregulation modification under dynamic conditions. RESULTS: Normotensive and hypertensive participants had no significant CBF differences in the supine position. After HDT, CBF mean variations (CBF-mVs) across all structures declined (mean -5.8%) for the whole population (n = 36), with -6.6 and -7.6% decreases, respectively, in white matter and gray matter (P < 0.001). Left and right accumbens nuclei had the largest changes (-9.6 and -9.2%, respectively; P < 0.001). No CBF-mV difference (0/16) was found in hypertensive patients after HDT, whereas normotensive participants' CBF-mVs changed significantly in four structures (left and right accumbens, putamen and left caudate nucleus) and gray matter. Hypertensive patients exhibited fewer CBF-mVs in left caudate nuclei (P = 0.039) and cortical gray matter (P = 0.013). Among hypertensive patients, people with diabetes had smaller CBF-mVs than people without diabetes. CONCLUSION: Our results highlight the significantly different CBF reactions to HDT of normotensive and hypertensive participants. They support the hypothesis that hypertension is responsible for deficient cerebrovascular autoregulation.

Impact of Head-Down Position on Cerebral Blood Flow in Healthy Subjects: An Arterial Spin-Labeling MR Perfusion Study.

BACKGROUND: A head-down (HD) position is used in some stroke centers to maintain cerebral perfusion (CP) in stroke patients. PURPOSE: To assess CP in healthy volunteers in the supine and HD (-15°) positions. STUDY TYPE: Prospective. POPULATION: Eighteen healthy subjects of 53 (±8) years old. FIELD STRENGTH/SEQUENCE: 1.5T / arterial spin-labeling (ASL) in the supine position and after 4 minutes of HD position. ASSESSMENT: Regions of interest from reconstructed cerebral blood-flow (CBF) maps: subcortical nuclear gray matter (accumbens, amygdala, caudate, hippocampus, pallidum, putamen, thalamus), cortical gray matter (cGM), and white matter (WM). We also monitored hemodynamic parameters. STATISTICAL TESTS: Shapiro-Wilk test, analysis of variance (ANOVA) tests, Student's t-tests, and Pearson correlation analysis. RESULTS: CBF was higher in women compared to men, whatever the position (mean difference of 17% in supine, and 13% in HD position). From supine to HD position, CBF was decreased in all regions (mean decrease of -7%). Simultaneously, mean arterial pressure and systolic blood pressure increased (respectively P = 0.004 and P < 0.001). DATA CONCLUSION: The CBF decrease, despite increased hemodynamic parameters, may indicate efficient cerebral autoregulation. Our results seem to reflect only early cerebral autoregulation stages but may open the way towards a more precise understanding of CP. LEVEL OF EVIDENCE: 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:218-224.

Can MRI water apparent diffusion coefficient (ADC) value discriminate between idiopathic normal pressure hydrocephalus, Alzheimer's disease and subcortical vascular dementia?

Numerous similarities in MRI and clinical symptoms exist between Alzheimer's disease (AD), subcortical vascular dementia (sVD) and possible idiopathic normal pressure hydrocephalus (iHPN). The aim of this study is to explore mean apparent coefficient diffusion (ADC) difference between theses diseases in different periventricular and deep white matter areas, as compared to healthy controls. This retrospective study analyzed mean ADC values of 120 patients in normal appearing deep white matter and lenticular nuclei, frontal, caudate nuclei corpus and parietal periventricular and deep white matter areas INPH group showed significantly lower ADC than sVD group in frontal periventricular region (1567.10-6mm2/s vs 1755.10-6mm2/s; P=0.0009) and in parietal deep region (1087.10-6mm2/s vs 1271.10-6mm2/s; P=0.0052), but showed significantly higher ADC in lenticular nuclei ROI (834.10-6mm2/s vs 753.10-6mm2/s; P=0.002). The comparison between iNPH and sVD showed a cut-off value of 1676.10-6mm2/s (sensitivity 0.70, specificity 0.77) in periventricular frontal area. INPH group, in comparison with NA group, showed significantly higher ADC in all ROIs. The iNPH group also showed significantly higher ADC than AD group in all ROIs. AD group showed significantly lower ADC than sVD group in all regions, except in normal appearing lenticular nuclei and caudate nuclei corpus deep ROI. SVD group showed significantly higher ADC than NA in all ROIs, except in normal appearing lenticular nucleus ROI. Different patterns of ADC values can differentiate between AD, sVD and iNPH, even when other MRI sequences appear morphologically similar.

Absolute and regional cerebral perfusion assessment feasibility in head-down position with arterial spin-labeling magnetic resonance. A preliminary report on healthy subjects.

PURPOSE: Head-down (HD)-positioning, used in some stroke centers during early ischemic stroke management, is empirical but supported by some physiological findings. It has been shown by nonmagnetic resonance methods that this position can increase cerebral perfusion. This study aimed to investigate magnetic resonance imaging (MRI) ability to measure the response to head-down tilt (HDT) challenge in healthy volunteers. Cerebral blood flow (CBF) was assessed with arterial spin labeling (ASL) in supine and HD (-15°) positions. METHODS: Cerebral perfusion was measured in supine and HD positions in seven healthy subjects at 1.5T with a large magnet bore (70cm) MRI device. 3D pseudocontinuous arterial spin-labeling (pCASL) sequences were acquired in both positions and cerebral blood flow (CBF) maps were reconstructed. Regions of interest were subcortical gray matter structures (accumbens nuclei, amygdala, caudate nucleus, hippocampus, pallidum, putamen and thalamus), whole cortical gray matter and whole white matter. RESULTS: White matter and subcortical gray matter structures' CBF, averaged over the volunteers' sample, remained stable from supine to HD position. Accumbens nuclei and cortical gray matter CBF decreased by 11.5% (P=0.013) and 11.4% (P=0.018) when head position was changed from flat to -15°. CONCLUSIONS: Regional CBF assessment, especially in HDT, is challenging with most perfusion techniques because of ionizing radiations, inherent limitations and logistical considerations. This preliminary report presents a noninvasive technique assessing regional and absolute cerebral blood flow changes in response to posture change. It can lead to further clinical investigations for a better understanding of cerebral perfusion.

MRI characteristics of carotid bulb atypical fibromuscular dysplasia in black stroke patients.

BACKGROUND AND PURPOSE: In black stroke patients, a particular form of fibromuscular dysplasia (FMD), called atypical FMD (aFMD), is involved in stroke mechanism. The high rate of stroke recurrence under medical treatment leads to propose surgery in such patients. Regarding its location level on the carotid bulb, aFMD is often confused with atherosclerosis or free-floating thrombus. Nowadays, only histology can confirm the diagnosis. MRI of aFMD has never been assessed. MATERIALS AND METHODS: The constitution of a black patient's cohort with aFMD-related ischemic stroke is currently in progress in the French West Indies, Martinique. In patients scheduled for surgery, MRI of the carotid bifurcation was analyzed preoperatively, with subsequent histological examination of the excised specimen. The first four black stroke patients with MRI and histological findings are described. RESULTS: On imaging, aFMD lesion was homogeneous with isosignal on T2-weighted sequences and slight hypersignal on T1-weighted sequences with mild gadolinium enhancement of the inner layer. Histological findings confirmed the aFMD mainly located in the intima. CONCLUSIONS: aFMD generates a particular MRI pattern in our four patients, which could increase the diagnosis accuracy. Carotid bulb lesion in black stroke patients should suggest aFMD and MRI analysis may contribute to rule out differential diagnoses.