To seek neural sources of endogenous event-related potentials, brain activations related to rare target stimuli detection in auditory and visual oddball tasks were imaged using a high temporal resolution functional MRI technique. There were multiple modality specific and modality non-specific activations. Auditory specific activations were seen in the bilateral transverse temporal gyri and posterior superior temporal planes while visual specific activations were seen in the bilateral occipital lobes and their junctions with the temporal lobes. Modality non-specific activations were seen in multiple areas including the bilateral parietal and temporal association areas, bilateral prefrontal cortex, bilateral premotor areas, bilateral supplementary motor areas and anterior cingulate gyrus. Results were consistent with previous intracranial evoked potential recording studies, and supported the multiple generator theory of the endogenous event-related potentials.

These findings demonstrate lower signal intensity of the cortex on T2-weighted images in the first HG and surrounding STG compared with that of the MTG.

Background Continuous circulation and drainage of cerebrospinal fluid (CSF) are essential for the elimination of CSF-borne metabolic products and neuronal function. While multiple CSF drainage pathways have been identified, the significance of each to normal drainage and whether there are differential changes at CSF outflow regions in the aging brain are unclear. Methods Dynamic in vivo imaging of near infrared fluorescently-labeled albumin was used to simultaneously visualize the flow of CSF at outflow regions on the dorsal side (transcranial and -spinal) of the central nervous system. This was followed by kinetic analysis, which included the elimination rate constants for these regions. In addition, tracer distribution in ex vivo tissues were assessed, including the nasal/cribriform region, dorsal and ventral surfaces of the brain, spinal cord, cranial dura, skull base, optic and trigeminal nerves and cervical lymph nodes. Results Based on the in vivo data, there was evidence of CSF elimination, as determined by the rate of clearance, from the nasal route across the cribriform plate and spinal subarachnoid space, but not from the dorsal dural regions. Using ex vivo tissue samples, the presence of tracer was confirmed in the cribriform area and olfactory regions, around pial blood vessels, spinal subarachnoid space, spinal cord and cervical lymph nodes but not for the dorsal dura, skull base or the other cranial nerves. Also, ex vivo tissues showed retention of tracer along brain fissures and regions associated with cisterns on the brain surfaces, but not in the brain parenchyma. Aging reduced CSF elimination across the cribriform plate but not that from the spinal SAS nor retention on the brain surfaces. Conclusions Collectively, these data show that the main CSF outflow sites were the nasal region across the cribriform plate and from the spinal regions in mice. In young adult mice, the contribution of the nasal and cribriform route to outflow was much higher than from the spinal regions. In older mice, the contribution of the nasal route to CSF outflow was reduced significantly but not for the spinal routes. This kinetic approach may have significance in determining early changes in CSF drainage in neurological disorder, age-related cognitive decline and brain diseases.

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Purpose: To optimize timing parameters in an intermolecular double-quantum coherence (iDQC) imaging pulse sequence for overall image signal-to-noise ratio (SNR) and blood oxygenation level-dependent (BOLD) sensitivity for brain functional imaging. Material and Methods:Fresh human blood was measured under different oxygenation conditions, and human brain functional magnetic resonance (fMR) images in three normal volunteers were obtained, using iDQC techniques at 1.5 T. The dependence of SNR and BOLD sensitivity was measured as a function of time delays after the iDQC evolution period.Results: A time delay after the iDQC evolution period can be adjusted either to refocus the dephasing accumulated during , thus increasing SNR, with full rephasing occurring at delay ϭ Ϯ2 (for iDQC order n ϭ Ϯ2), or to enhance BOLD effects with consequent reduced image SNR at delay ϭ 0. Conclusion:Image SNR and BOLD sensitivity often impose different requirements for iDQC image sequence design and timing parameter selections. It is therefore important to select properly relevant parameters for different applications. INTERMOLECULAR DOUBLE-QUANTUM coherence (iDQC), or intermolecular long-range dipolar interactions, may provide new contrast in magnetic resonance imaging (MRI) (1-5). The correlation distance of intermolecular dipolar interaction, which is under control of the experimenter, may supply a "structural probe" at mesoscopic scales for exploring distributions of microvascular or cellular structures (1,6,7). It has been suggested that the contrast in iDQC imaging can be derived from variations in magnetic susceptibilities over a distance between 10 m and a few millimeters (1,2). The sensitivity of iDQC to the blood oxygenation level-dependent (BOLD) effect is based on long-range dipolar interactions, and the preliminary studies have suggested that iDQC is more sensitive to the local magnetic susceptibility effect than the conventional single-quantum coherence (SQC) (8,9). Functional MRI (fMRI) applications with iDQC signals potentially allow more specific determination of functional locations in the brain, complementing the conventional fMRI based on SQC signals. In the past few years, unique effects of longrange dipolar fields have been applied to a wide range of studies, including fMRI in humans (8,9), enhancing rat brain tumor contrast in MRI (2), the determination of the absolute concentration of nuclear spins in the brain (10), diffusion-weighted MRI (11), structural measurements in phantoms (12) and cancerous trabecular bones (7,13), high-field MR microscopic imaging in mouse brain (14), human brain tumor imaging (15), and observing high-resolution spectra in a 1-GHz resistive electromagnet (16).It is known, however, that the signal-to-noise ratio (SNR) is intrinsically much lower for iDQC imaging than for conventional SQC imaging (2,4,5). It was determined from both theoretical calculations and experiments that the signal intensity of iDQC is in the order of only a few percent of SQC at 1.5 T (4,5), though its SNR increa...