Evidence for Neural Effects of Repetition that Directly Correlate with Behavioral Priming

Stimulus repetition associates with neural activity reductions during tasks that elicit behavioral priming. Here we present direct evidence for a quantitative relation between neural activity reductions and behavioral priming. Fifty-four subjects performed a word classification task while being scanned with functional MRI. Activity reductions were found in multiple high-level cortical regions including those within the prefrontal cortex. Importantly, activity within several of these regions, including the prefrontal cortex, correlated with behavior such that greater activity reductions associated with faster performance. Whole-brain correlational analyses confirmed the observation of anatomic overlap between regions showing activity reductions and those showing direct brain–behavioral correlations. The finding of a quantitative relation between neural and behavioral effects in frontal regions suggests that repetition reduces frontally mediated processing in a manner that ultimately facilitates behavior.Psycholog

A case study of voltage-gated potassium channel antibody-related limbic encephalitis with PET/MRI findings

Preclinical and clinical studies have demonstrated the significance of inflammation and autoantibodies in epilepsy, and the use of immunotherapies in certain situations has become an established practice. Temporal lobe epilepsy can follow paraneoplastic or nonparaneoplastic limbic encephalitis associated with antibodies directed against brain antigens. Here, we focus on a patient with worsening confusion and temporal lobe seizures despite treatment with antiepileptic medications. Serial brain MRIs did not conclusively reveal structural abnormalities, so the patient underwent brain PET/MRI to simultaneously evaluate brain structure and function, revealing bitemporal abnormalities. The patient was diagnosed with voltage-gated potassium channel antibody-related limbic encephalitis based on clinical presentation, imaging findings, and antibody testing. Treatment included the addition of a second antiepileptic agent and oral steroids. His seizures and cognitive deficits improved and stabilized

Evaluating functional MRI procedures for assessing hemispheric language dominance in neurosurgical patients.

International audienceTwo methods of quantifying hemispheric language dominance (HLD) in neurosurgical patients are compared: (1) an average magnitudes (AM) method, which is a calculation of the average signal intensity variation in regions of interest for each patient that were predefined in a group analysis for each task, and (2) a lateralization indices (LI) method, which is based on the number of activated pixels in regions of interest predefined in each individual patient. Four language tasks [a living/nonliving (LNL) judgment, word stem completion (WSC), semantic associate (SA) and a phonological associate (PA) task] were compared with "gold standard" measures such as the Wada test or electrocortical stimulation. Results showed that the LI method was more accurate (73% agreement with gold standard methods) than the AM method (only 40% agreement) across tasks and subjects. Furthermore, by varying the threshold used for determining laterality, the ability of functional magnetic resonance imaging (fMRI) to predict HLD was influenced for the AM method, whereas the LI method was relatively unaffected by changing the threshold. Using the LI method, the SA task was the most accurate for quantifying HLD (100% agreement with gold standard methods) with respect to the other three language tasks (80% accuracy for WSC, 65% for the LNL and 63% for phonological task). Depending on the method and the task, fMRI may be a promising tool for assessing HLD in neurosurgical patients