Integrating Functional and Diffusion Magnetic Resonance Imaging for Analysis of Structure-Function Relationship in the Human Language Network

The capabilities of magnetic resonance imaging (MRI) to measure structural and functional connectivity in the human brain have motivated growing interest in characterizing the relationship between these measures in the distributed neural networks of the brain. In this study, we attempted an integration of structural and functional analyses of the human language circuits, including Wernicke's (WA), Broca's (BA) and supplementary motor area (SMA), using a combination of blood oxygen level dependent (BOLD) and diffusion tensor MRI.Functional connectivity was measured by low frequency inter-regional correlations of BOLD MRI signals acquired in a resting steady-state, and structural connectivity was measured by using adaptive fiber tracking with diffusion tensor MRI data. The results showed that different language pathways exhibited different structural and functional connectivity, indicating varying levels of inter-dependence in processing across regions. Along the path between BA and SMA, the fibers tracked generally formed a single bundle and the mean radius of the bundle was positively correlated with functional connectivity. However, fractional anisotropy was found not to be correlated with functional connectivity along paths connecting either BA and SMA or BA and WA. for use in diagnosing and determining disease progression and recovery

Somatotopic organization of corticospinal/corticobulbar motor tracts in controls and patients with tumours: A combined fMRI–DTI study

Objectives: To investigate the relative somatotopic organization of the motor corticospinal/corticobulbar foot, hand, lip and tongue fascicles by combining fMRI with DTI and to examine the influence of subjacent intrinsic tumours on these fascicles. Methods: The study was approved by the local ethics committee. Seven male and three female volunteers (median age: 35 years) and one female and eight male patients with brain tumours (median age: 37 years) were scanned on a 1.5-T MRI scanner. fMRI data, analysed using SPM5, identified the motor task-driven fMRI grey matter activations of the hand, foot, lips and tongue as seed regions for probabilistic tractography. The relationship between the components of the CST was assessed and the distances between them were measured. A statistical comparison was performed comparing these distances in the group of healthy hemispheres with those of the group of non-affected hemispheres and healthy hemispheres. Results: Hand fascicles were identified in all subjects (38/38, 100%), followed by foot (32/38, 84%), lip (31/38, 81%) and tongue fascicles (28/38, 74%). At superior levels, the hand fascicles were anterolateral to the foot fascicles in 77–93% of healthy hemispheres (HH), in 50–71% of non-affected patients' hemispheres (pH) and in 67–89% of affected PH. At inferior levels, the hand fascicles were either anteromedial in 46–45% of HH or anterior in 75% of non-affected PH and in 67–83% of affected PH. Tongue and lip fascicles overlapped in 25–45% of HH, in 10–20% of non-affected PH and in 15–25% of affected PH. No significant difference was found between the group of affected hemispheres and that of healthy and non-affected hemispheres. Conclusion: The somatotopy of the hand fascicles in relation to the foot fascicles was anterolateral in patients and volunteers at superior levels but anteromedial in volunteers and mostly anterior in patients at inferior levels. The lip and tongue fascicles generally overlapped. Intracranial tumours displaced the motor fascicles without affecting their relative somatotopy

Fattori che modulano i processi decisionali: uno studio sull’effetto framing

Lo studio prende in considerazione il cosiddetto “effetto framing”, definito come il contesto in cui l’individuo si trova a operare una scelta. Nello specifico, il modo in cui un problema decisionale è formulato influisce sulla percezione del punto di partenza del problema, rispetto al quale valutare i possibili esiti delle proprie azioni. Lo studio ha indagato l’entità e le caratteristiche dell’effetto framing in soggetti sani e in pazienti con esiti di grave cerebrolesione acquisita (GCA) ed ha esaminato le possibili relazioni tra tale effetto e alcuni processi cognitivi che si ritiene siano alla base dei processi decisionali. Sono state quindi valutate caratteristiche neuropsicologiche (working memory, funzioni attentive ed esecutive) e neuropsichiatriche (impulsività/disinibizione in particolare), ipotizzando che la presenza dell’effetto framing sia direttamente correlata a quella dei disturbi neuropsicologici e di personalità eventualmente presenti. Tutti i partecipanti sani che i pazienti sono stati esaminati mediante test neuropsicologici, scale cliniche e una prova computerizzata costruita ad hoc. I risultati hanno evidenziato la presenza degli effetti attesi, con un aumento di tale effetto nel gruppo dei pazienti con GCA, ponendo rilievo nella pratica clinica agli aspetti decisionali che incidono sulla qualità della loro vita e dell’intero sistema familiare. Questo è l’unico studio in cui una procedura che richiede di inibire attivamente le risposte automatiche, viene utilizzata per indagare i processi cognitivi coinvolti nell’effetto framing. In conclusione, raccolte insieme, le precedenti scoperte e i nostri primi risultati, forniscono evidenze convergenti a partire da paradigmi sperimentali differenti che supportano l’ipotesi secondo cui l’attivazione di un sistema esecutivo-analitico (caratterizzato da processi controllati, deliberati e cognitivi) possa influenzare i processi decisionali in condizione di framing

Multimodal fMRI tractography in normal subjects and in clinically recovered traumatic brain injury patients

In this study, we defined an operator-independent protocol for reconstructing the anatomical connections originating from fMRI activations in order to demonstrate that results obtained with this protocol are affected by alterations of functional activations. Seven healthy volunteers and two patients who sustained traumatic brain injury underwent an fMRI with a finger tapping task and a DTI scan. Cortical fMRI activations were used directly as seed mask for tractography for the reconstruction of individual motor pathways. On patients we observed a different motor network if compared to healthy subjects. However, when the activations of healthy subjects were used as seed masks for the tractography in patients, we observed for the patients a pattern of connectivity more similar to what was observed for healthy subjects. At the same time, when the activations of patients were used for the tractography on healthy subjects, we obtained patterns of connectivity similar to those obtained for patients. These results show the potential of the integration of fMRI and tractography for clarifying the mechanisms of cortical plasticity in the recovery of motor functions