We present the first cellular-resolution magnetic resonance (MRI) images of an alert animal. Unanesthetized blowflies were inserted into an efficient home-built gradient probe in a 14.1 T magnet, and images of (20-40 μm)3 voxel size—smaller than the dimensions of many cells in the fly’s brain—were obtained in several hours. The images have exceptional contrast-to-noise levels, and comparison with histology-based anatomical information shows that the MRI microscopy faithfully represents detailed patterns of musculature and nervous tissue common to muscoid species. Even at the highest resolutions we explored, morphological detail was pronounced in the apparent absence of instabilities or movement-related artifacts frequently observed during in vivo imaging of animal specimens. Cellular-level structural information is present in the images and rigorously demonstrable by cross-correlation of the data in Fourier space. Our work constitutes a methodological prerequisite for functional imaging studies at cellular...

Previous studies suggest that high resolution MRI can detect amyloid deposits [Benveniste H, 1999]. In this study we used a 11.7T imaging system to record 3-D T2*-weighted gradient echo images at 11.7 µm per voxel of formalin-fixed T1 temporal horn specimens from 3 aged non demented subjects and 3 Alzheimer's disease subjects. Tissue encompassed cerebral cortex and white matter. The samples were then stained for amyloid (Aß) deposits and for iron deposits. In both Alzheimer diseased and control cerebral cortices, hypo-intense spots and halo-like structures were clearly visible in MR images. 3D visualization of the images and comparison of MR images with neuropathology revealed that some of the hypo-intense structures were blood vessels. Due to susceptibility effects caused by residual iron, the blood vessels appeared larger in MR images than in neuropathological slices. In some Alzheimer samples, spots in the MR images had a geographical pattern similar to the pattern of amyloid deposits. However, in other...

It is now well established behaviorally that syncopation (moving antiphase to a pacing stimulus) is intrinsically less stable and requires more attention than inphase synchronization. Recent fMRI results have shown that, relative to synchronization, syncopation results in significant increases in activation of cortical and subcortical areas involved in planning, preparation and timing. We investigated the degree to which this increased activation is altered by practice. Baseline levels of the BOLD response were obtained from eight subjects while they syncopated or synchronized with an auditory metronome at 1.25 Hz. Subjects then practiced syncopation at the same rate while fMR images were acquired continuously. Post practice scans of the two coordination modes were then performed. Before practice, baseline syncopation was associated with significantly greater activation than synchronization in SMA, pre-motor cortices and cerebellum, reflecting the extra planning and timing requirements of syncopation. Acti...

We describe a frameless stereotaxic method for guiding recording electrode position. This involves two steps; Stereotaxic mapping of the brain to position a recording chamber, and subsequent stereotaxic mapping of the brain beneath the chamber expressed in chamber coordinates. Prior to surgery the animal undergoes T1 weighted 3D MR imaging, providing an anatomical dataset of 0.7mm resolution. The monkey is anesthetized for the MRI using a cocktail of ketamine, xylazine and atropine. Only light anesthesia is needed as the method requires no rigid stereotaxic fixation. Images are post-processed using AFNI software. The 3D image is rotated into the standard stereotaxic plane using skull/brain anatomy, and stereotaxic zero is set in the midline at the extended horizontal convergence of the external auditory meatii (to coincide with the surgical stereotaxic unit). This MRI is used to determine the optimal center and angle for surgically placing the recording chamber. Following attachment of the chamber the monk...

In order to understand the kinematics of the musculature controlling feeding in the marine mollusk Aplysia californica, we have developed a series of increasingly realistic kinematic models of the feeding apparatus, the buccal mass (Drushel et al., JEB, 1998; Chiel et al., Soc. Neurosci. Abstr., 1998, 1999). Using high spatial resolution MRI scans of freshly dissected buccal masses, a realistic external shape of the radula/odontophore at rest has been determined, which is approximated by modified ellipsoid octants. The surface of the radula is approximated by two planes that intersect the volume of the odontophore. By extracting parameters from high temporal resolution MRI taken of the buccal mass during swallowing movements in intact animals, it is possible to generate realistic shapes and positions for the radula/odontophore during the entire swallowing cycle, subject to the biological constraints that the total surface of the radula and the total volume of the odontophore are kept constant. To validate ...

Comparative neuroimaging allows for the identification of similarities and differences between species. It provides an important and promising avenue, to answer questions about the evolutionary origins of the brain´s organization, in terms of both structure and function. Dog functional magnetic resonance imaging (fMRI) has recently become one particularly promising and increasingly used approach to study brain function and coevolution. In dog neuroimaging, image acquisition has so far been mostly performed with coils originally developed for use in human MRI. Since such coils have been tailored to human anatomy, their sensitivity and data quality is likely not optimal for dog MRI. Therefore, we developed a multichannel receive coil (K9 coil, read “canine”) tailored for high-resolution functional imaging in canines, optimized for dog cranial anatomy. In this paper we report structural ( n  = 9) as well as functional imaging data (resting-state, n  = 6; simple visual paradigm, n  = 9) collected with the K9 c...

Comparative neuroimaging allows for the identification of similarities and differences between species. It provides an important and promising avenue, to answer questions about the evolutionary origins of the brain´s organization, in terms of both structure and function. Dog fMRI has recently become one particularly promising and increasingly used approach to study brain function and coevolution. In dog neuroimaging, image acquisition has so far been mostly performed with coils originally developed for use in human MRI. Since such coils have been tailored to human anatomy, their sensitivity and data quality is likely not optimal for dog MRI. Therefore, we developed a multi-channel receive coil (K9 coil, read “canine”) tailored for high-resolution functional imaging in canines, optimized for dog cranial anatomy. In this paper we report structural (n = 9) as well as functional imaging data (resting-state, n = 6; simple visual paradigm, n = 9) collected with the K9 coil in comparison to reference data collect...

The well-known arcuate fasciculus that connects the posterior superior temporal region with the language production region in the ventrolateral frontal cortex constitutes the classic peri-Sylvian dorsal stream of language. A second temporofrontal white matter tract connects ventrally the anterior to intermediate lateral temporal cortex with frontal areas via the extreme capsule. This temporofrontal extreme capsule fasciculus (TFexcF) constitutes the ventral stream of language processing. The precise origin, course, and termination of this pathway has been examined in invasive tract tracing studies in macaque monkeys, but there have been no standard protocols for its reconstruction in the human brain using diffusion imaging tractography. Here we provide a protocol for the dissection of the TFexcF in vivo in the human brain using diffusion magnetic resonance imaging (MRI) tractography which provides a solid basis for exploring its functional role. A key finding of the current dissection protocol is the demon...

Our eyes are constantly in motion and the various kinds of eye movements are closely linked to many aspects of human cognitive processing. Measuring all possible eye movements unobtrusively is not achievable with current methods. Video-based eye-trackers only measure rotational but not translational motion of the eye, require a calibration process relying on the participant’s self-report of accurate fixation, and do not work if vision of the eyeball is blocked. Scleral search coils attach physical weight on the eyeball and also do not measure translation. Here, we describe a novel and fully automated method to use real-time magnetic resonance imaging (MRI) for eye tracking. We achieved a temporal resolution sufficient to measure eye rotations and translations as short as those that occur within a blink and behind a closed eyelid. To demonstrate this method, we measured the full extent of the blink-related eye movement for two individuals, suggesting that the eye approaches a holding position during lid clo...

The exact mechanisms involved in cognitive impairment that occurs with AIDS is unclear. Neuropsychological testing is often performed to assess deficits, however, non-invasive measurements of cerebral blood flow may allow for detection of deficits prior to abnormal neuropsychological results. Early diagnosis and treatment may lead to improvement. CASL MRI is a non-invasive tool that follows tissue and microvasculature perfusion of arterial water. 32 HIV patients and 6 controls underwent neuropsychological evaluation and were rated on the HIV dementia scale by Power (10 asymptomatic, 14 MCD, 8 ADC). Patients had laboratory results (CD4+, viral load, hemoglobin, hematocrit) taken within 2 months of the scan. Images were obtained on a Siemens 3.0T scanner using a standard quadrature head coil and imaging protocol which includes an axial rapid gradient echo followed by a CASL perfusion sequence. Global resting perfusion (GRP) and resting perfusion (RP) within the perforating branches of arterial circulation wa...