Trial-by-trial variability in perceptual performance on identical stimuli has been related to spontaneous fluctuations in ongoing activity of intrinsic functional connectivity networks (ICNs). In a paradigm requiring sustained vigilance for instance, we previously observed that higher prestimulus activity in a cingulo-insular-thalamic network facilitated subsequent perception. Here, we test our proposed interpretation that this network underpins maintenance of tonic alertness. We used simultaneous acquisition of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) in the absence of any paradigm to test an ensuing hypothesis, namely that spontaneous fluctuations in this ICN′s activity (as measured by fMRI) should show a positive correlation with the electrical signatures of tonic alertness (as recorded by concurrent EEG). We found in human subjects (19 male, 7 female) that activity in a network comprising dorsal anterior cingulate cortex, anterior insula, anterior prefrontal cortex ...

Concomitant increase in activity within the mid-dorsolateral prefrontal cortex (MDLFC) and the posterior parietal cortex (PPC) is observed in most functional neuroimaging studies of working memory ([Collette et al., 1999][1]; [Gerton et al., 2004][2]; [Sun et al., 2005][3]; [Postle et al., 2006][4]; [Champod and Petrides, 2007][5]; [Emery et al., 2008][6]). Despite broad consensus on the importance of these two brain regions in working memory, their unique contribution, especially that of the PPC, remains a matter of heated debate ([Paulesu et al., 1993][7]; [Smith and Jonides, 1998][8]; [Postle et al., 1999][9]; [Berryhill and Olson, 2008][10]). The main objective of the present parametric event-related functional magnetic resonance imaging study was to examine the hypothesis that the cortex in the intraparietal sulcus region in the PPC is involved in the manipulation (i.e., rearrangement) of verbal information in working memory and to dissociate the involvement of this brain region from that of the MDLFC...

Neurophysiological data obtained in primates suggests that merely observing others' actions can modulate activity in the observer's motor cortices. In humans, it has been suggested that these multimodal vicarious responses extend well beyond the motor cortices, including somatosensory and insular brain regions, which seem to yield vicarious responses when witnessing others' actions, sensations, or emotions ([Gazzola and Keysers, 2009][1]). Despite the wealth of data with respect to shared action responses in the monkey motor system, whether the somatosensory and insular cortices also yield vicarious responses during observation of touch remains largely unknown. Using independent tactile and motor fMRI localizers, we first mapped the hand representations of two male monkeys' primary (SI) and secondary (SII) somatosensory cortices. In two subsequent visual experiments, we examined fMRI brain responses to (1) observing a conspecific's hand being touched or (2) observing a human hand grasping or mere touching ...

Diffusion tensor imaging (DTI) and immunohistochemistry were used to examine axon injury in the rat spinal cord after unilateral L2–L4 dorsal root axotomy at multiple time points (from 16 h to 30 d after surgery). Three days after axotomy, DTI revealed a lesion in the ipsilateral dorsal column extending from the lumbar to the cervical cord. The lesion showed significantly reduced parallel diffusivity and increased perpendicular diffusivity at day 3 compared with the contralateral unlesioned dorsal column. These findings coincided with loss of phosphorylated neurofilaments, accumulation of nonphosphorylated neurofilaments, swollen axons and formation of myelin ovoids, and no clear loss of myelin (stained by Luxol fast blue and 2′-3′-cyclic nucleotide 3′-phosphodiesterase). At day 30, DTI of the lesion continued to show significantly decreased parallel diffusivity. There was a slow but significant increase in perpendicular diffusivity between day 3 and day 30, which correlated with gradual clearance of myeli...

In the article “Magnocellular Pathway Impairment in Schizophrenia: Evidence from Functional Magnetic Resonance Imaging” by Antígona Martínez, Steven A. Hillyard, Elisa C. Dias, Donald J. Hagler Jr, Pamela D. Butler, David N. Guilfoyle, Maria Jalbrzikowski, Gail Silipo, and Daniel C. Javitt,

Oxytocin is released in the maternal brain during breastfeeding and may help strengthen the mother–infant relationship. Here, we used functional magnetic resonance imaging to determine whether oxytocin modulates brain activity in postpartum day 4–8 dams receiving suckling stimulation. During imaging sessions, dams were exposed to pup suckling before and after administration of an oxytocin receptor antagonist. Another group of dams received oxytocin alone. Changes in brain activation in response to suckling closely matched that elicited by oxytocin administration. The overlapping brain areas included the olfactory system, nucleus accumbens, insular cortex, prefrontal cortex, ventral tegmental area, cortical amygdala, and several cortical and hypothalamic nuclei. Blockade of oxytocin receptors largely attenuated activation in these regions. The data suggest that oxytocin may strengthen mother–infant bond formation partly by acting through brain areas involved in regulating olfactory discrimination, emotions,...

The cause of stuttering remains unknown. Several studies indicate the presence of subtle differences in neurophysiological function and structure in adults who stutter (AWS) compared to normally fluent controls, supporting past hypotheses of aberrant speech motor and sensory function related to stuttering. To date, such findings have not been replicated in children, although stuttering starts and more often than not resolves on its own during childhood. The mechanisms of stuttering persistence and recovery can best be revealed through investigating children, as they are less likely to exhibit structural/functional differences due to the possible effects of years dealing with their speech deficit, common in AWS. In this study, subtle volumetric differences in brain white and gray matter (wm, gm) growth in three groups of children differing in stuttering status (children with persistent developmental stuttering (P), those recovered naturally from stuttering (R), and normally fluent children (N)) were compare...

Regional brain volume deficits are accompanied by a commensurate increase in the local volume of CSF. Thus, CSF may be considered an endogenous tracer for detecting regional brain volume deficits using MRI. In diffusion tensor imaging (DTI), affected brain areas show greater CSF partial volume effects and increased apparent diffusion coefficient (ADC). We propose a new method, ADC-based morphometry (ABM), for assessment of regional brain volume deficits using voxelwise analysis of ADC maps computed from DTI. We demonstrate this approach by its application to 15 patients with schizophrenia and 15 healthy controls. DTI and structural MRI were performed on all subjects. All 30 ADC maps were registered to a template in Talairach space by applying a nonlinear registration to their corresponding structural MRI volume. Following inter-subject registration of the ADC maps, a two-tailed independent samples t-test was applied at each voxel to determine the voxels at which the ADC values significantly differed betwee...

Humans can judge grating orientation by touch. Previous studies indicate that the extrastriate cortex is involved in tactile orientation judgments, suggesting that this area is related to visual imagery. However, it has been unclear which neural mechanisms are crucial for the tactile processing of orientation, because visual imagery is not always required for tactile spatial tasks. We expect that such neural mechanisms involve multisensory areas, because our perception of space is highly integrated across modalities. The current study uses functional magnetic resonance imaging during the classification of grating orientations to evaluate the neural substrates responsible for the multisensory spatial processing of orientation. We hypothesized that a region within the intraparietal sulcus (IPS) would be engaged in orientation processing, regardless of the sensory modality. Sixteen human subjects classified the orientations of passively touched gratings and performed two control tasks with both the right and ...