Lysergic acid diethylamide (LSD) is a potent drug that produces distorted perceptions, disorganized thought, and altered mood in humans. At present, the neuronal substrates mediating these effects are poorly understood. In this study, we used functional magnetic resonance imaging (fMRI) to evaluate LSD-induced blood oxygen level dependent (BOLD) response in rat brain. Briefly, rats (n=3) were anesthetized with isoflurane (1%), paralyzed with pancuronium (0.5 mg/kg, i.p.), artificially ventilated (50 breaths/min, tidal volume of 3 ml), and placed in a Varian 9.4 Tesla MRI instrument. After collecting basal volume data sets for 20 min, rats received LSD (500 µg/kg, i.p.) and volume data sets were collected for 40 min post drug. Mean voxel values averaged across a 5 min period prior to and 25-30 min after LSD administration were compared using Student's t-test (significance level set at p < 0.001). Anatomical localization of the BOLD signal was determined by using a rat brain atlas template (Paxinos and Watso...

Previous studies have detected locations of electrode tips in cortices by combining anatomical information acquired with MRI and tip positional information acquired by other techniques such as radiography (Nahm et al, Exp. Brain Res., 1994) or sonography (Glimcher et al, J. Neurosci. Methods, 2001). In this study, we tested the detectability of electrode tips directly on anatomical MR images. We first conducted in vitro study to optimize MR scan conditions and examined the accuracy of the tip detection. As a phantom we used a glass insulated tungsten electrode and reference glass tubes that were sunk together in Copper Sulfate solution. To estimate the accuracy of tip detection, distances between the electrode and the reference glass tubes were measured and compared in two different ways; one using MRI and the other using an optical microscope. MR images were acquired with a 4.7 T MRI scanner (Biospec 47/40, Bruker, Ettlingen) using a Fast Spin Echo sequence (in-plane resolution=50-200 µm by side, TR=1000-...

Prior studies have used fMRI to measure the onset of neural activity from a stable baseline with a temporal precision on the order of 100 msec. Many important neural processes, however, reveal themselves as increases in activity that lie on top of another neural response. We attempted to determine whether fMRI could measure the timing of an increase that occurred 200 msec after initial response. Subjects viewed stimuli from three conditions. In our baseline condition, a low contrast flickering checkerboard was presented for 600 msec. We added a 400 msec contrast increment to this stimulus either at a 200 msec delay or immediately upon stimulus presentation; thus in the delay condition the low contrast checkerboard increased its contrast after 200 msec and remained high contrast for 400 msec, while in the immediate condition a high contrast flickering checkerboard reduced its contrast after 400 msec and remained low for 200 msec. We acquired BOLD fMR images every 100 msec (TR) while these conditions were pr...

Object Incidence of silent microbleeds (MBs) in patients with moyamoya disease (MMD) was investigated using 3-tesla (3T) MR unit. Methods We retrospectively examined incidence of silent MBs in twenty-five patients among 63 patients hospitalized with MMD between 1999 and 2004 by gradient-echo T2*-weighted images using 3-tesla (3T) and 1.5T MR units. There were five men and twenty women, ranging in age from 17 to 66 years old (mean 41+14 years old). Eighteen patients were diagnosed with ischemic MMD and seven patients with hemorrhagic MMD. Incidence of MBs was also evaluated with the same 3T MR unit in thirty-four healthy volunteers including seven men and twenty-seven women, ranging in age from 18 to 71 years old (mean 33+12 years old). Silent MBs could be fond in eleven patients (44 %) by 3T MR unit, while they were detected in seven patients (28%) by1.5T unit. At the 3T study of the healthy individuals, MBs were found in two patients (5.8%). Incidence of MBs was significantly higher in the patients with M...

This study assessed, via fMRI, changes in cortical activity during a training session with Functional Electrical Therapy (FET) - a rehabilitative therapy that combines voluntary activation with patterned Functional Electrical Stimulation of muscles (FES). Five able bodied subjects participated in this study. Each subject was instrumented with surface stimulation electrodes positioned over motor points of the finger flexor/extensors muscles on the right arm. A button press with the left index finger initiated patterned electrical stimuli (50 Hz, 200 ìs pulse duration, 8-15 mA pulse amplitude) to produce right hand opening and closing. Right index finger flexion/extension was recorded with a goniometer. Subjects were scanned in a 3T GE scanner using standard fMRI methods in a randomized block design paradigm with 5 different conditions: rest, voluntary activation (VA), imagined movement, FES, and FET. Each task lasted 30 s and repeated 5 times. Data were realigned, smoothed and normalized using standard proc...

We compared psychophysical and functional magnetic resonance imaging (fMRI) responses within areas V1-V3 and MT+ during both a speed and a contrast discrimination task. We found that fMRI responses did not depend significantly on task in any of these areas. Moreover, responses in V1-V3 were larger than those in MT+ for both the speed and the contrast discrimination tasks across a wide range of contrasts. This pattern of results demonstrates that localizing function based on finding those regions of cortex that show greater activity to a given task-stimulus combination than to other tasks and stimuli may, under certain conditions, be misleading. However, a simple ideal observer model assuming that perceptual thresholds are dependent on neuronal population responses does successfully show that V1 has neuronal properties consistent with our subjects' contrast discrimination performance, and that MT+ has neuronal properties consistent with subjects' performance on a speed discrimination task.

Introduction: The use of manganese chloride as a contrast agent for visualizing specific axonal projections with MRI is currently a topic under intense investigation. We demonstrate here the use of this technique to visualize normal and lesioned optic nerve in adult frog and fish. Materials and Methods: Adult frogs (rana pipiens, n=5) and adult fish (brown trout, n=5) were subjected to unilateral optic nerve transection followed by ipsilateral intravitreal injection of 2 ul of 100 mM manganese chloride. Normal control animals (n=3) underwent unilateral intravitreal injections of 2 ul of 100 mM of manganese chloride. All procedures were in accordance with national and local authority regulations. MRI was performed at 2.35 T using a Bruker Biospec Avance DBX-100 (Bruker AG, Germany) in accordance with a modified protocol by Brekken et al. 2003. Results: MRI performed at 48-72 hours post-injection demonstrated specific contrast uptake and transport in vivo throughout the visual system of both frog and fish. F...

We used functional magnetic resonance imaging (fMRI) to investigate human visual pathways underlying perception of three-dimensional (3-D) structure from motion induced by two-dimensional (2-D) rotational or translational motion. We compared significant brain activity regions between 2-D and 3-D conditions in each motion stimulus by using a block paradigm. In each experimental scan, subjects viewed a rotational or translational stimuli. The 3-D condition was presented for 16 seconds, followed by the 2-D condition for 16 seconds. Each condition was alternately repeated 12 times. The fMRI was done at 3T. For 3-D structure-from-motion (SFM) by the rotational motion stimulus, the parieto-occipital area, especially V3A, the intraparietal sulcus (IPS) and the inferior parietal lobule (IPL), activated. On the other hand, for 3-D SFM by the translational motion stimulus, significant activation was not observed in the parieto-occipital area. It may be suggested that the separated pathways contribute to 3-D SFM by r...

Tactile-visual cross-modal plasticity due to visual deprivation has been reported. Whether this is solely due to visual deprivation or with any long-term tactile training is not yet determined, particularly in the primary visual cortex (V1). If tactile learning by the sighted subjects induces activation of the visual cortex by the tactile tasks, the latter may be the case. Here we conducted fMRI studies with normal sighted persons who had long been trained by tactile shape discrimination of Mah-Jong tiles with their right thumb (Saito et al., 2003). The tasks were the tactile shape discrimination with Mah-Jong tiles and with Braille characters to which they are naïve. During the scan, two dimensional shape patterns on a plastic tile were presented tactually. Subjects were explored the presented tiles by the right thumb with eyes closed and asked to discriminate the presented pair was same or not. Tactile discrimination with Mah-Jong tile with their right thumb activated the V1 of the well-trained subjects....

Functional magnetic resonance imaging (fMRI) was used to study memory-associated activation of medial temporal lobe (MTL) regions in 3 groups: cognitively intact elderly controls (n=10), individuals with mild cognitive impairment (MCI, n=9), and patients with probable Alzheimer’s disease (AD, n=10). Subjects performed a face-name associative encoding task during fMRI scanning, and were tested for recognition of stimuli afterward. High-resolution structural and fMRI data were acquired with a 3T scanner. Two approaches were used to analyze MRI data: statistical parametric mapping of group mean activation and differences between groups, and a functional-anatomic method in which fMRI activation was quantified within MTL regions of interest identified from each individual’s structural MRI. Despite clinical evidence of a history of decline in memory function, MCI subjects performed similarly to controls on the fMRI memory task (85% and 87%, p=0.6); AD patients performed significantly worse (66%, p<0.005). In the...