NeuroImage
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Simultaneous acquisition of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) aims to disentangle the description of brain processes by exploiting the advantages of each technique. Most studies in this field focus on exploring the relationships between fMRI signals and the power spectrum at some specific frequency bands (alpha, beta, etc.). On the other hand, brain mapping of EEG signals (e.g., interictal spikes in epileptic patients) usually assumes an haemodynamic response function for a parametric analysis applying the GLM, as a rough approximation. ⋯ This approach avoids EEG subsampling to fMRI time resolution and naturally provides a test for EEG predictive power over BOLD signal fluctuations, in a well-established statistical framework. We illustrate this concept in resting state (eyes closed) and visual simultaneous fMRI-EEG experiments. The results point out that it is possible to predict the BOLD fluctuations in occipital cortex by using EEG measurements.
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Pain is a multidimensional experience. Human pain perception can be modulated by subjective emotional responses. We examined this association within the context of a neuroimaging study, using functional MRI to examine neural responses to electrical pain-inducing stimuli in 15 healthy subjects (6 females; age range=20-30 years). ⋯ We found that subjective pain ratings were higher in the sad emotional context than in the happy and neutral contexts, and that pain-related activation in the ACC was more pronounced in the sad context relative to the happy and neutral contexts. Psychophysiological interaction (PPI) and dynamic causal modeling (DCM) analyses demonstrated amygdala to ACC connections during the experience of pain in the sad context. These findings serve to highlight the neural mechanisms that may be relevant to understanding the broader relationship between somatic complaints and negative emotion.
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Brain-derived neurotrophic factor (BDNF) is involved in memory and the pathophysiology of various neuropsychiatric disorders. A single nucleotide polymorphism in the human BDNF gene (Val66Met) affects memory, and influences Alzheimer's disease and depression vulnerability in a sex-specific manner. Recent animal studies suggest that BDNF mediates memory for emotional experiences in the amygdala, but it is currently unknown whether BDNF Val66Met influences memory processing in the amygdala. ⋯ Subsequent tests showed a larger contribution of these brain regions to successful encoding and retrieval in male Met allele carriers than male Val homozygotes, whereas no significant differences were observed in females. These results provide preliminary evidence that the BDNF Val66Met polymorphism influences specific mnemonic operations underlying encoding and retrieval of salient stimuli, and suggest less efficient memory processing in male Met allele carriers. Furthermore, the sex-specific genotype effects may contribute to sex-specific effects of BDNF Val66Met on depression vulnerability.
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Comparative Study
Graph-theory based parcellation of functional subunits in the brain from resting-state fMRI data.
Resting-state fMRI provides a method to examine the functional network of the brain under spontaneous fluctuations. A number of studies have proposed using resting-state BOLD data to parcellate the brain into functional subunits. In this work, we present two state-of-the-art graph-based partitioning approaches, and investigate their application to the problem of brain network segmentation using resting-state fMRI. ⋯ Resting-state fMRI data were acquired from 43 healthy subjects, and the Ncut algorithm was used to parcellate several different cortical regions of interest. The group-wise delineation of the functional subunits based on resting-state fMRI was highly consistent with the parcellation results from two task-based fMRI studies (one with 18 subjects and the other with 20 subjects). The findings suggest that whole-brain parcellation of the cortex using resting-state fMRI is feasible, and that the Ncut algorithm provides the appropriate technique for this task.
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The lateral surface of the right frontal lobe has a relevant role in modulating behavioral responses to aversive stimuli and may significantly influence pain experience. Imaging studies suggest that this modulatory role is multifaceted, but no studies have assessed the regional specialization of this cortex on the basis of its response dynamics during pain processing. We aimed to investigate functional specialization within the right lateral frontal cortex using a dynamic fMRI approach. ⋯ The anterior prefrontal cortex showed full activation during late painful stimulation and was negatively correlated with pain unpleasantness. In conclusion, different elements within the right lateral frontal cortex showed distinct activation dynamics in response to painful stimulation, which would suggest relevant regional specialization during pain processing. These findings are congruent with the broad functional role of the right frontal cortex and its influence on crucial aspects of human behavior.