Impact of truncating diffusion MRI scans on diffusional kurtosis imaging.

OBJECTIVE: Diffusional kurtosis imaging (DKI) extends diffusion tensor imaging (DTI), characterizing non-Gaussian diffusion effects but requires longer acquisition times. To ensure the robustness of DKI parameters, data acquisition ordering should be optimized allowing for scan interruptions or shortening. Three methodologies were used to examine how reduced diffusion MRI scans impact DKI histogram-metrics: 1) the electrostatic repulsion model (OptEEM); 2) spherical codes (OptSC); 3) random (RandomTRUNC). MATERIALS AND METHODS: Pre-acquired diffusion multi-shell data from 14 female healthy volunteers (29±5 years) were used to generate reordered data. For each strategy, subsets containing different amounts of the full dataset were generated. The subsampling effects were assessed on histogram-based DKI metrics from tract-based spatial statistics (TBSS) skeletonized maps. To evaluate each subsampling method on simulated data at different SNRs and the influence of subsampling on in vivo data, we used a 3-way and 2-way repeated measures ANOVA, respectively. RESULTS: Simulations showed that subsampling had different effects depending on DKI parameter, with fractional anisotropy the most stable (up to 5% error) and radial kurtosis the least stable (up to 26% error). RandomTRUNC performed the worst while the others showed comparable results. Furthermore, the impact of subsampling varied across distinct histogram characteristics, the peak value the least affected (OptEEM: up to 5% error; OptSC: up to 7% error) and peak height (OptEEM: up to 8% error; OptSC: up to 11% error) the most affected. CONCLUSION: The impact of truncation depends on specific histogram-based DKI metrics. The use of a strategy for optimizing the acquisition order is advisable to improve DKI robustness to exam interruptions.

Working memory during spontaneous migraine attacks: an fMRI study.

OBJECTIVE: To investigate the neural correlates of working memory during a spontaneous migraine attack compared to the interictal phase, using functional magnetic resonance imaging (fMRI). BACKGROUND: Cognitive disturbances are commonly observed during migraine attacks, particularly in the headache phase. However, the neural basis of these changes remains unknown. METHODS: In a fMRI within-subject test-retest design study, eleven women (32 years of age, average) with episodic migraine were evaluated twice, first during a spontaneous migraine attack, and again in a pain-free period. Each session consisted in a cognitive assessment and fMRI while performing a working memory task (N-back). RESULTS: Cognitive test scores were lower during the ictal session than in the pain-free session. Regions typically associated with working memory were activated during the N-back task in both sessions. A voxel wise between session comparison showed significantly greater activation in the left frontal pole and orbitofrontal cortex during the attack relative to the interictal phase. CONCLUSION: Migraine patients exhibited greater activation of the left frontal pole and orbitofrontal cortex while executing a verbal working memory task during a spontaneous migraine attack when compared to the interictal state. Given the association of these regions with pain processing and inhibitory control, these findings suggest that patients recruit inhibitory areas to accomplish the cognitive task during migraine attacks, a neural signature of their cognitive difficulties.

Impact of susceptibility-induced distortion correction on perfusion imaging by pCASL with a segmented 3D GRASE readout.

PURPOSE: The consensus for the clinical implementation of arterial spin labeling (ASL) perfusion imaging recommends a segmented 3D Gradient and Spin-Echo (GRASE) readout for optimal signal-to-noise-ratio (SNR). The correction of the associated susceptibility-induced geometric distortions has been shown to improve diagnostic precision, but its impact on ASL data has not been systematically assessed and it is not consistently part of pre-processing pipelines. Here, we investigate the effects of susceptibility-induced distortion correction on perfusion imaging by pseudo-continuous ASL (pCASL) with a segmented 3D GRASE readout. METHODS: Data acquired from 28 women using pCASL with 3D GRASE at 3T was analyzed using three pre-processing options: without distortion correction, with distortion correction, and with spatial smoothing (without distortion correction) matched to control for blurring effects induced by distortion correction. Maps of temporal SNR (tSNR) and relative perfusion were analyzed in eight regions-of-interest (ROIs) across the brain. RESULTS: Distortion correction significantly affected tSNR and relative perfusion across the brain. Increases in tSNR were like those produced by matched spatial smoothing in most ROIs, indicating that they were likely due to blurring effects. However, that was not the case in the frontal and temporal lobes, where we also found increased relative perfusion with distortion correction even compared with matched spatial smoothing. These effects were found in both controls and patients, with no interactions with the participant group. CONCLUSION: Correction of susceptibility-induced distortions significantly impacts ASL perfusion imaging using a segmented 3D GRASE readout, and this step should therefore be considered in ASL pre-processing pipelines. This is of special importance in clinical studies, reporting perfusion across ROIs defined on relatively undistorted images and when conducting group analyses requiring the alignment of images across different subjects.

Structural Anatomical Investigation of Long-Term Memory Deficit in Behavioral Frontotemporal Dementia.

Although a growing body of work has shown that behavioral variant frontotemporal dementia (bvFTD) could present with severe amnesia in approximately half of cases, memory assessment is currently the clinical standard to distinguish bvFTD from Alzheimer's disease (AD). Thus, the concept of "relatively preserved episodic memory" in bvFTD remains the basis of its clinical distinction from AD and a criterion for bvFTD's diagnosis. This view is supported by the idea that bvFTD is not characterized by genuine amnesia and hippocampal degeneration, by contrast to AD. In this multicenter study, we aimed to investigate the neural correlates of memory performance in bvFTD as assessed by the Free and Cued Selective Reminding Test (FCSRT). Imaging explorations followed a two-step procedure, first relying on a visual rating of atrophy of 35 bvFTD and 34 AD patients' MRI, contrasted with 29 controls; and then using voxel-based morphometry (VBM) in a subset of bvFTD patients. Results showed that 43% of bvFTD patients presented with a genuine amnesia. Data-driven analysis on visual rating data showed that, in bvFTD, memory recall & storage performances were significantly predicted by atrophy in rostral prefrontal and hippocampal/perihippocampal regions, similar to mild AD. VBM results in bvFTD (pFWE<0.05) showed similar prefrontal and hippocampal regions in addition to striatal and lateral temporal involvement. Our findings showed the involvement of prefrontal as well as medial/lateral temporal atrophy in memory deficits of bvFTD patients. This contradicts the common view that only frontal deficits explain memory impairment in this disease and plead for an updated view on memory dysfunctions in bvFTD.

Using game authoring platforms to develop screen-based simulated functional assessments in persons with executive dysfunction following traumatic brain injury.

The assessment of functional status is a critical component of clinical neuropsychological evaluations used for both diagnostic and therapeutic purposes in patients with cognitive brain disorders. There are, however, no widely adopted neuropsychological tests that are both ecologically valid and easily administered in daily clinical practice. This discrepancy is a roadblock to the widespread adoption of functional assessments. In this paper, we propose a novel approach using a serious game authoring platform (eAdventure) for creating screen-based simulated functional assessments. We created a naturalistic functional task that consisted of preparing a cup of tea (SBS-COT) and applied the assessment in a convenience sample of eight dyads of therapists/patients with mild executive dysfunction after traumatic brain injury. We had three main aims. First, we performed a comprehensive review of executive function assessment in activities of daily living. Second, we were interested in measuring the feasibility of this technology with respect to staffing, economic and technical requirements. Third, a serious game was administered to patients to study the feasibility of this technology in the clinical context (pre-screening test). In addition, quantitative (Technology Acceptance Model (TAM) questionnaires) and qualitative (semistructured interviews) evaluations were applied to obtain user input. Our results suggest that the staffing, economic and technical requirements of the SBS-COT are feasible. The outcomes of the pre-screening test provide evidence that this technology is useful in the functional assessment of patients with executive dysfunction. In relation to subjective data, the TAM questionnaire showed good user acceptability from a professional perspective. Interview analyses with professionals and patients showed positive experiences related to the use of the SBS-COT. Our work indicates that the use of these types of authoring platforms could have positive long-term implications for neuropsychological research, opening the door to more reproducible, cooperative and efficient research by allowing the facilitated production, reuse and sharing of neuropsychological assessment tools.

Towards affordable biomarkers of frontotemporal dementia: A classification study via network's information sharing.

Developing effective and affordable biomarkers for dementias is critical given the difficulty to achieve early diagnosis. In this sense, electroencephalographic (EEG) methods offer promising alternatives due to their low cost, portability, and growing robustness. Here, we relied on EEG signals and a novel information-sharing method to study resting-state connectivity in patients with behavioral variant frontotemporal dementia (bvFTD) and controls. To evaluate the specificity of our results, we also tested Alzheimer's disease (AD) patients. The classification power of the ensuing connectivity patterns was evaluated through a supervised classification algorithm (support vector machine). In addition, we compared the classification power yielded by (i) functional connectivity, (ii) relevant neuropsychological tests, and (iii) a combination of both. BvFTD patients exhibited a specific pattern of hypoconnectivity in mid-range frontotemporal links, which showed no alterations in AD patients. These functional connectivity alterations in bvFTD were replicated with a low-density EEG setting (20 electrodes). Moreover, while neuropsychological tests yielded acceptable discrimination between bvFTD and controls, the addition of connectivity results improved classification power. Finally, classification between bvFTD and AD patients was better when based on connectivity than on neuropsychological measures. Taken together, such findings underscore the relevance of EEG measures as potential biomarker signatures for clinical settings.

Social Cognition in a Clinical Sample of Personality Disorder Patients.

Social cognition was assessed in a clinical sample of personality disorder (PD) stable patients receiving ambulatory treatment (N = 17) and healthy matched controls (N = 17) using tests of recognition of emotions in faces and eyes, in a test of social faux pas and in theory of mind (ToM) stories. Results indicated that when compared with healthy controls, individuals with PD showed a clear tendency to obtain lower scoring in tasks assessing recognition of emotion in faces (T = -2.602, p = 0.014), eyes (T = -3.593, p = 0.001), ToM stories (T = -4.706, p = 0.000), and Faux pas (T = -2.227, p = 0.035). In the present pilot study, PD individuals with a normal cognitive efficiency showed an impaired performance at social cognition assessment including emotion recognition and ToM.

[Prognostic heterogeneity of attention deficit/hyperactivity disorder in adults]. / Descomponiendo el síndrome de déficit atencional en el adulto: hacia un entendimiento de su heterogeneidad pronóstica.

Attention Deficit/Hyperactivity Disorder (ADHD) is a clinical syndrome characterized by an onset in early life. More than 65% of patients persist with manifestations of ADHD in adulthood. These symptoms may interfere in activities of daily-living, interpersonal relationships and professional and academic achievement. Nevertheless, the observation of an important group of adults with ADHD who do not show significant difficulties in the areas mentioned before puts into evidence the prognostic heterogeneity of this disorder. One of the current, most accepted explanations is the Double-Pathway Model: two double-dissociated deficits (Executive Disorders and Delayed-Reward Processing impairments) are involved in the genesis of ADHD, which explains the existence of different behavioral phenotypes. Moreover, personality traits like tenacity or perseverance are associated with higher levels of achievement in adults. On these grounds, we propose the hypothesis that the neurobiological correlate of tenacity/perseverance is a preserved Delayed-Reward Processing capacity, although further studies are needed to verify this idea.

Descomponiendo el síndrome de déficit atencional en el adulto: hacia un entendimiento de su heterogeneidad pronóstica / Prognostic heterogeneity of attention deficit/hyperactivity disorder in adults

Attention Deficit/Hyperactivity Disorder (ADHD) is a clinical syndrome characterized by an onset in early life. More than 65% of patients persist with manifestations of ADHD in adulthood. These symptoms may interfere in activities of daily-living, interpersonal relationships and professional and academic achievement. Nevertheless, the observation of an important group of adults with ADHD who do not show significant difficulties in the areas mentioned before puts into evidence the prognostic heterogeneity of this disorder. One of the current, most accepted explanations is the Double-Pathway Model: two double-dissociated deficits (Executive Disorders and Delayed-Reward Processing impairments) are involved in the genesis of ADHD, which explains the existence of different behavioral phenotypes. Moreover, personality traits like tenacity or perseverance are associated with higher levels of achievement in adults. On these grounds, we propose the hypothesis that the neurobiological correlate of tenacity/perseverance is a preserved Delayed-Reward Processing capacity, although further studies are needed to verify this idea.

Psiquiatría de enlace e interconsultoría psiquiátrica en un hospital general: 25 años después / Liason psychiatric and psychiatric consultation in a general hospital after 25 years

El presente estudio analiza las características actuales de la atención psiquiátrica brindada por el equipo de Enlace del Hospital del Salvador de Santiago de Chile, comparándolas con otro estudio efectuado en la misma unidad hace veinticinco años. Se trabaja con 793 interconsultas recibidas entre enero 2003 hasta julio del 2004, estudiando a 680 pacientes hospitalizados en los distintos servicios del complejo Salvador Infante (Hospital del Salvador, Instituto Nacional de Enfermedades Respiratorias y Cirugía Torácica e Instituto de Neurocirugía). Se indaga respecto a características sociodemográficas de la población atendida, servicios solicitantes, patologías médicas, motivos de solcitud de interconsulta psiquiátrica y/o diagnóstico psiquiátrico presuntivos, diagnósticos entregados por los especialistas según criterio del CIE-10, atención entregada y sugerencias de derivación. Los datos son registrados al momento de evaluar a los pacientes en una ficha estructurada a tal fin. Se observan importantes diferencias respecto a las prevalencias entre los médicos solicitantes y el equipo de enlace, destacándose el alto porcentaje de depresiones diagnósticadas por el primer grupo (36 por ciento). El equipo de enlace diagnosticó en cambio mayor porcentaje de trastornos secundarios al estrés (37 por ciento) y de trastornos por abuso de sustancias (22por ciento). Las diferencias observadas para ambos grupos resultaron estadísticamente significativas (chi cuadrado=168,71)(p<0,001). Esta disparidad fue observada ya en 1981 aunque en menor grado. Se discute el aumento progresivo de la demanda de atención psiquiátrica de enlace en el Hospital del Salvador y su inclusión en nuevos ámbitos de la medicina.