Differential cerebellar functional interactions during an interference task across multiple sclerosis phenotypes.

PURPOSE: To determine whether modification of the connections between cerebellar and prefrontal areas might vary among multiple sclerosis (MS) phenotypes and might be associated with cognitive failure. MATERIALS AND METHODS: Approval of the institutional review boards and written informed consent were obtained from each participant. Stroop-related functional magnetic resonance (MR) imaging activations and effective connectivity abnormalities between the right cerebellum and any other brain regions were assessed by using a psychophysiologic interaction (PPI) analysis from 17 patients with relapsing-remitting (RR), 17 with benign, and 23 with secondary progressive (SP) MS and 18 healthy control subjects (P < .05, corrected at cluster level). Correlations with disease duration, T2 lesion volume, brain volume, and response times (RTs) during the incongruent condition were estimated (P < .001, uncorrected). RESULTS: Activation and PPI analyses showed that, compared with the other groups, RR MS group had abnormal recruitment of regions of the left frontoparietal lobes, whereas compared with RR MS group, SP MS group had abnormal recruitment of the cingulum or precuneus. Benign MS group had increased activation of the right prefrontal cortex, and increased interaction between these regions and the right cerebellum. In healthy controls, RTs inversely correlated with activity of right cerebellum and several frontoparietal regions. In MS, RTs inversely correlated with bilateral cerebellar activity and directly correlated with right precuneus activity. In MS, disease duration inversely correlated with right cerebellar activity and directly correlated with left inferior frontal gyrus and right precuneus activity. Higher T2 lesion volume and lower brain volumes were related to activity in these areas. CONCLUSION: Patients with MS who have various clinical phenotypes experience different abnormalities in activation and effective connectivity between the right cerebellum and frontoparietal areas, which contribute to inefficient cortical reorganization, with increasing cognitive load. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120216/-/DC1.

Differential cerebellar and cortical involvement according to various attentional load: role of educational level.

Recent imaging studies have evidenced various cerebral patterns dependent on educational level during cognitive tasks in neurodegenerative diseases. Determining relationships between educational status and cerebral activation during cognitive demands in physiological conditions may help to better understand the role of education on cognitive efficacy and functional reorganisation in pathological conditions. We proposed to analyse by functional MRI (fMRI) the relationship between educational status and cerebral activation during various attentional requests in healthy young adults. Twenty healthy young adults completed four successive conditions of a Go/No-go test of increasing complexity under fMRI. An effect of education was observed on attentional performances. Both in-scanner response times and cerebral activation increased during the Go/No-go paradigm. Healthy subjects with higher education exhibited higher activity in cerebellum and lower activity in medial prefrontal and inferior parietal regions compared with the healthy subjects with lower educational levels while performing the conditions of Go/No-go task. Our data evidence the influence of education on automatized strategies in healthy adults by modulating a functional balance of activation between cerebral cortex and cerebellar regions during attentional processes.

Evidence of cognitive compensation associated with educational level in early relapsing-remitting multiple sclerosis.

BACKGROUND: Cognitive compensatory mechanisms may limit the cognitive dysfunction due to cerebral tissue destruction in multiple sclerosis (MS). OBJECTIVE: To explore the effect of educational status on cognitive performances in early relapsing-remitting (RR) MS. METHODS: 43 RRMS patients were individually matched for age, sex and educational level with 43 healthy controls. Each patient underwent neuropsychological tests, clinical assessment and magnetic resonance imaging (MRI). Cognitive scores of MS patients were compared to those of their paired controls according to educational level. RESULTS: Less educated patients had low performances on all but two neuropsychological tests, while more educated patients had low scores only for three tests. Cognitive performances of more educated patients but not those of less educated ones were strongly correlated with MRI parameters and decreased with the severity of cerebral tissue destruction. CONCLUSION: These different cognitive patterns suggest the existence of a cognitive compensation in more educated patients which is limited by the accumulation of tissue damage.

Neuronal Circuits for Fear Expression and Recovery: Recent Advances and Potential Therapeutic Strategies.

Recent technological developments, such as single unit recordings coupled to optogenetic approaches, have provided unprecedented knowledge about the precise neuronal circuits contributing to the expression and recovery of conditioned fear behavior. These data have provided an understanding of the contributions of distinct brain regions such as the amygdala, prefrontal cortex, hippocampus, and periaqueductal gray matter to the control of conditioned fear behavior. Notably, the precise manipulation and identification of specific cell types by optogenetic techniques have provided novel avenues to establish causal links between changes in neuronal activity that develop in dedicated neuronal structures and the short and long-lasting expression of conditioned fear memories. In this review, we provide an update on the key neuronal circuits and cell types mediating conditioned fear expression and recovery and how these new discoveries might refine therapeutic approaches for psychiatric conditions such as anxiety disorders and posttraumatic stress disorder.