Functional tractography by means of Direct Electrical Stimulation (DES) provides information about functional connections between remote brain areas. Here, we perform group analysis of DES data and corroborate results obtained by multi-subject clusterin...

Illusory contours (perceived edges that exist in the absence of local stimulus borders) demonstrate that perception is an active process, creating features not present in the light patterns striking the retina. Illusory contours are thought to be processed using mechanisms that partially overlap with those of “real” contours, but questions about the neural substrate of these percepts remain. Here, we employed functional magnetic resonance imaging to obtain physiological signals from human visual cortex while subjects viewed different types of contours, both real and illusory. We sampled these signals independently from nine visual areas, each defined by retinotopic or other independent criteria. Using both within- and across-subject analysis, we found evidence for overlapping sites of processing; most areas responded to most types of contours. However, there were distinctive differences in the strength of activity across areas and contour types. Two types of illusory contours differed in the strength of ac...

In many cases of callosal dysgenesis in both human patients and mouse models, misguided fibers from the cortex form abnormal bilateral, barrel-shaped structures known as Probst bundles. Because little is known about how axons are arranged within these anomalous fiber bundles, understanding this arrangement may provide structural and molecular insights into how axons behave when they are misguided in vivo . Previous studies described these bundles as longitudinal swirls of axons that fail to cross the midline ([Ozaki et al., 1987][1]). However, recent studies on human acallosal patients using diffusion tensor magnetic resonance imaging (DTMRI) technology suggest that axons project in an anteroposterior direction within the Probst bundle ([Lee et al., 2004][2]; [Tovar-Moll et al., 2007][3]). This led us to ask the question, is DTMRI an accurate method for analyzing axonal tracts in regions of high axon overlap and disorganization, or is our current perception of axon arrangement within these bundles inaccura...

Magnetic resonance imaging using the blood-oxygenation-level-dependent response (BOLD-fMRI) is the technique of choice for non-invasive, high spatial resolution measurement of human brain activity. Proton magnetic resonance spectroscopy (1H-MRS) can be ...

Picking up a cup requires transporting the arm to the cup (transport component) and preshaping the hand appropriately to grasp the handle (grip component). Here, we used functional magnetic resonance imaging to examine the human neural substrates of the transport component and its relationship with the grip component. Participants were shown three-dimensional objects placed either at a near location, adjacent to the hand, or at a far location, within reach but not adjacent to the hand. Participants performed three tasks at each location as follows: (1) touching the object with the knuckles of the right hand; (2) grasping the object with the right hand; or (3) passively viewing the object. The transport component was manipulated by positioning the object in the far versus the near location. The grip component was manipulated by asking participants to grasp the object versus touching it. For the first time, we have identified the neural substrates of the transport component, which include the superior pariet...

The present study investigated the neural circuitry of affective processing in depression using event-related fMRI. Positive, negative, and neutral affective images were presented sequentially for 3 s, separated by blank screens, while BOLD signal fMRI data were acquired. Six medication-free individuals with Major Depressive Disorder or Dysthymia and six healthy controls viewed 3 runs of 63 different picture presentations. Three different time conditions provided an effective time resolution of 1s. A voxel-by-voxel 2-way (Valence x Group) ANOVA was done to examine percent signal change. Voxels exceeding the significance threshold for the interaction were further tested with planned comparison t-tests that were corrected by the Bonferroni method. Paired t-tests for the significant voxel clusters revealed differences between the negative and the neutral images for the depressed group, p's <.005. Depressed participants showed greater right prefrontal activation (tranverse frontal polar gyrus, superior frontal...

Humans can acquire appropriate behaviors that maximize rewards on a trial-and-error basis. Recent electrophysiological and imaging studies have demonstrated that neural activity in the midbrain and ventral striatum encodes the error of reward prediction. However, it is yet to be examined whether the striatum is the main locus of reward-based behavioral learning. To address this, we conducted functional magnetic resonance imaging (fMRI) of a stochastic decision task involving monetary rewards, in which subjects had to learn behaviors involving different task difficulties that were controlled by probability. We performed a correlation analysis of fMRI data by using the explanatory variables derived from subject behaviors. We found that activity in the caudate nucleus was correlated with short-term reward and, furthermore, paralleled the magnitude of a subject's behavioral change during learning. In addition, we confirmed that this parallelism between learning and activity in the caudate nucleus is robustly m...

Introduction: Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging treatment option for various neurological and psychiatric diseases. Functional magnetic resonance imaging studies show increased activity of nucleus tractus solitarii,...

Current functional neuroimaging techniques, such as functional magnetic resonance imaging, rely on indirect consequences (the hemodynamic response) to quantify neural activity. With the development of a photoacoustic (PA) imaging system and use of trans...

Current functional imaging techniques, such as functional magnetic resonance imaging, rely upon activity-induced blood flood changes to neurons. This indirect measurement of neuronal activity inherently limits image resolution and specificity. However, ...