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Proton nuclear magnetic resonance (NMR) signals may be obtained from the human body in such a way as to produce images of anatomical slices. The NMR signal is mapped in the selected slice by application of field gradients which provide spatial encoding. Excellent NMR images are now obtained which are useful in clinical practice. Introduction of NMR imaging into major hospitals is proceeding rapidly, with 10 commercial companies supplying the market; over 500 whole body systems have been installed worldwide. As a method of medical imaging NMR has the advantage that it uses no ionizing radiation and is therefore inherently safe; moreover, it gives sections in transverse, coronal, and sagittal planes with equal ease, and has good tissue contrast and pathological contrast arising from relaxation time differences. Contrast may be improved by use of contrast agents. Current trends suggest that before very long, whole-body NMR systems will be found in all major hospitals.

Two experiments were conducted to determine whether consistent algorithmic response patterning on 8- and 10-arm versions of the radial maze is independent of spatial encoding. On the 8-arm version well-trained hooded rats were tested in darkness, after maze rotation that rendered room cues ambiguous with respect to arm positions, or with room cues unsystematically relocated. Ambiguous maze rotation was also used with well-trained subjects on the 10-arm version. If algorithmic patterning is a learned, non-spatial strategy, animals using it consistently ought not to have been affected by changes in the spatial layout of the test environment, and the type of pattern used by each subject would have remained constant. On the 8-arm radial maze, responses were most often made to arms 2 or 3 from that just visited. In many animals patterns were interchangeable, switching occurring between preferred angles of turn from day to day. Performance fell when animals were tested in darkness and upon ambiguous maze rotation early (but not later) in training. Testing in darkness increased the angle through which animals turned when responding, perhaps due to the disturbance of intramaze cue use. On the 10-arm maze the “consecutive arm” pattern was used persistently by several animals and appeared to protect their performance from disruption by ambiguous maze rotation. Animals not using rigid patterning were adversely affected. However, on both mazes animals using patterning correctly identified maze arms that had been omitted from otherwise patterned choice sequences. Animals adopted continuous patterning only when spatial encoding had been established. Response patterning appears to serve a mnemonic function and in rats complements rather than replaces the use of a spatial representation of the environment. It was concluded that a complex, flexible relationship exists between spatial functioning and its expression via motor responses.

Three experiments were designed to investigatelength distortion—the tendency to inflate estimates of the inferred distance between two points, as the length of a circuitous pathway between them increases. This phenomenon, previously demonstrated with haptic and locomotor exploration (Lederman, Klatzky, Collins, & Wardell, 1987), was extended to vision through the presentation of pathways as a temporal sequence of illuminated points. The magnitude of the visual effect was less than that previously found in haptics, and conditions promoting the effect included a relatively slow presentation rate and moderately complex pathways. Commonalities in the pattern, if not the magnitude, of length distortion in vision and haptics suggest that similar processes of spatial encoding may underlie the phenomenon in both domains.

The authors report a spatial encoding technique such that the moire fringe pattern inherently existing with the retrieved image can be avoided. To improve the diffraction efficiency of the film, they have introduced a bleaching process so that the step of obtaining a positive encoded transparency can be eliminated. Instead of restricting the encoding processing to the linear region of the T-E curve, they allow encoding in the linear region of the D-E curve, so that a broader range of encoding exposure can be utilized. Experimental results indicate that excellent color fidelity, high signal to noise ratio, and good resolution of the reproduced color images can be obtained.

Summary Six male and six female subjects were given 112 trials on each of two tasks requiring a yes-no comparison of pairs of letters presented to the right and left hemispheres. One task was predominantly visual (detection of curved letter segments) and the other was predominantly verbal (detection of rhyming “ee”" sounds). It was found that for “yes” decisions, females were faster in the right hemisphere than in the left, while the reverse was the case for males. Also for females “no” decisions were faster than “yes” decisions in the left hemisphere but “yes” decisions were faster than “no” decisions in the right hemisphere.

Resolution limits in NMR imaging are imposed by bandwidth considerations, available magnetic gradients for spatial encoding, and signal to noise. This work reports modification of a clinical NMR imaging device with picture elements of 500 × 500 × 5000 μm to yield picture elements of 50 × 50 × 1000 μm. Resolution has been increased by using smaller gradient coils permitting gradient fields >0.4 mT/cm. Significant improvements in signal to noise are achieved with smaller rf coils, close attention to choice of bandwidth, and signal averaging. These improvements permit visualization of anatomical structures in the rat brain with an effective diameter of 1 cm with the same definition as is seen in human imaging. The techniques and instrumentation should open a number of basic sciences such as embryology, plant sciences, and teratology to the potentials of NMR imaging.

Two experiments were conducted which examined conjoint retention of spatial and verbal information in memory. The first experiment examined processing of text with simultaneous active dual coding. With spatial and verbal information from experiment one, the second experiment examined the effects of introducing dual coding prior to text processing and keyed recall to what was encoded prior to reading. Recall of both concrete features and events referring to these features was keyed to constructive encoding processes. Even minimal cueing produced better recall than no cues. Spatial primers produced not only better recall of features, but subjects who encoded spatial primers demonstrated increased ability to recall those primers. Results were interpretet in terms of dual coding theory for encoding and retrieval.

The tonotopic organization of brainstem auditory nuclei was compared in embryonic and hatchling chickens. In embryos, neurons at any given position in these nuclei were maximally sensitive to lower frequency sounds than the best frequency after hatching. This finding indicates that neurons are maximally stimulated by sounds of different frequencies as development proceeds and supports the hypothesis that during development there is a change in the spatial encoding of frequency along the cochlea.

The present experiment was designed to determine if a strategy imposed on a memory loaded task by a certain method of presentation of materials would transfer to a different display mode involving basically the same task but in a different format. It was found that, in general, spatial encoding strategies do transfer to different display formats requiring that the same task be performed.

The next few years will undoubtedly see a refinement of proton imaging technology and a broader data base will indicate to what extent proton relaxation parameters are able to detect and characterize disease. In addition, it is likely that imaging of other nuclei (e.g. 31P, 23Na, 19F) will become a reality, although it must be stated that due to their inherently lower sensitivity to NMR detection and/or lower physiological concentration, clinical images of nuclei other than 1H will undoubtedly have a low spatial resolution and may require relatively long imaging times [41]. Nonetheless, herein lies the exciting possibility of non-invasive metabolic or functional imaging [42]. The realm of NMR contrast agents is just beginning to be explored [43, 44], and developments in high-speed imaging [45] indicate useful applications in cardiology [46]. So whilst improvements in image quality can be expected, as was the case with X-ray CT, the application of NMR in medicine will diversify to yield information of a more specifically functional nature. This, together with the very low attendant biological risk [47], heralds a bright future for NMR in clinical diagnosis.

Following the lead of electronic computers, optical computers must adopt floating point calculation to allow for both high accuracy and high dynamic range. Given here is a method for using spatial encoding for that purpose.

Initial learning of the eight-arm radial maze was examined in groups of rats having either bilateral superior colliculus or posterior (visual) cortical lesions. Compared with a control group, colliculectomized animals were mildly impaired but visual decorticates exhibited a severe deficit comparable to that observed elsewhere in hippocampally lesioned rats. Postoperative retention of the task was transiently impaired by lesions of the superior colliculus, but once again posterior cortical lesions caused more marked deficits. Visual information used by spatial encoding mechanisms does not appear to be derived from the superior colliculus but rather from neocortical visual processes. Unlike hippocampally lesioned rats which make initial errors (reentering an already explored arm) fairly early in a trial, visual decorticates make initial errors later in the choice sequence. This suggests that these two types of lesion affect different aspects of performance.

Three-dimensional nuclear magnetic resonance (3D NMR) provides one of the foremost analytical tools available for the elucidation of biomolecular structure, function and dynamics. Executing a 3D NMR experiment generally involves scanning a series of time-domain signals S(t (3)), as a function of two time variables (t (1), t (2)) which need to undergo parametric incrementations throughout independent experiments. Recent years have witnessed extensive efforts towards the acceleration of this kind of experiments. Among the different approaches that have been proposed counts an "ultrafast" scheme, which distinguishes itself from other propositions by enabling-at least in principle-the acquisition of the complete multidimensional NMR data set within a single transient. 2D protein NMR implementations of this single-scan method have been demonstrated, yet its potential for 3D acquisitions has only been exemplified on model organic compounds. This publication discusses a number of strategies that could make these spatial encoding protocols compatible with 3D biomolecular NMR applications. These include a merging of 2D ultrafast NMR principles with temporal 2D encoding schemes, which can yield 3D HNCO spectra from peptides and proteins within approximate to 100 s timescales. New processing issues that facilitate the collection of 3D NMR spectra by relying fully on spatial encoding principles are also assessed, and shown capable of delivering HNCO spectra within 1 s timescales. Limitations and prospects of these various schemes are briefly addressed.

Purpose: In this study, we demonstrate the first combination of 3D FID proton MRSI and spatial encoding via concentric-ring trajectories (CRTs) at 3T. FID-MRSI has many benefits including high detection sensitivity, in particular for J-coupled metabolites (e.g., glutamate/glutamine). This makes it highly attractive, not only for clinical, but also for, potentially, functional MRSI. However, this requires excellent reliability and temporal stability. We have, therefore, augmented this 3D-FID-MRSI sequence with single-echo, imaging-based volumetric navigators (se-vNavs) for real-time motion/shim-correction (SHMOCO), which is 2× quicker than the original double-echo navigators (de-vNavs), hence allowing more efficient integration also in short-TR sequences. Methods: The tracking accuracy (position and B-field) of our proposed se-vNavs was compared to the original de-vNavs in phantoms (rest and translation) and in vivo (voluntary head rotation). Finally, the intra-session stability of a 5:40 min 3D-FID-MRSI scan was evaluated with SHMOCO and no correction (NOCO) in 5 resting subjects. Intra/inter-subject coefficients of variation (CV) and intra-class correlations (ICC) over the whole 3D volume and in selected regions of interest ROI were assessed. Results: Phantom and in vivo scans showed highly consistent tracking performance for se-vNavs compared to the original de-vNavs, but lower frequency drift. Up to ~30% better intra-subject CVs were obtained for SHMOCO (P < 0.05), with values of 9.3/6.9/6.5/7.8% over the full VOI for Glx/tNAA/tCho/m-Ins ratios to tCr. ICCs were good-to-high (91% for Glx/tCr in motor cortex), whereas the inter-subject variability was ~11–19%. Conclusion: Real-time motion/shim corrected 3D-FID-MRSI with time-efficient CRT-sampling at 3T allows reliable, high-resolution metabolic imaging that is fast enough for clinical use and even, potentially, for functional MRSI.

Multidimensional acquisitions play a central role in the progress and applications of nuclear magnetic resonance (NMR) spectroscopy. Such experiments have been collected traditionally as an array of one-dimensional scans, with suitably incremented delay parameters that encode along independent temporal domains the nD spectral distribution being sought. During the past few years, an ultrafast approach to nD NMR has been introduced that is capable of delivering any type of multidimensional spectrum in a single transient. This method operates by departing from the canonical nD NMR scheme and by replacing its temporal encoding with a series of spatial manipulations derived from magnetic resonance imaging. The present survey introduces the main principles of this subsecond approach to spectroscopy, focusing on the applications that have hitherto been demonstrated for single-scan two-dimensional NMR in different areas of chemistry.

The ability to reinstate neuronal assemblies representing mnemonic information is thought to require their consolidation through offline reactivation during sleep/rest. To test this, we detected cell assembly patterns formed by repeated neuronal co-activations in the mouse hippocampus during exploration of spatial environments. We found that the reinstatement of assembly patterns representing a novel, but not a familiar, environment correlated with their offline reactivation and was impaired by closed-loop optogenetic disruption of sharp wave-ripple oscillations. Moreover, we discovered that reactivation was only required for the reinstatement of assembly patterns whose expression was gradually strengthened during encoding of a novel place. The context-dependent reinstatement of assembly patterns whose expression did not gain in strength beyond the first few minutes of spatial encoding was not dependent on reactivation. This demonstrates that the hippocampus can hold concurrent representations of space that markedly differ in their encoding dynamics and their dependence on offline reactivation for consolidation. VIDEO ABSTRACT.

1. Cerebellar saccadic dysmetria may result from a disturbance in the processes that ensure correct execution of gaze displacement. Alternatively, an impairment in the preparatory processes that lead to the specification of the movement goal may also produce this deficit. 2. We report here on a pharmacologically induced dysmetria that suggests a cerebellar contribution to the neural processes encoding the location of the goal for orienting gaze shifts. 3. Shifts of gaze (eye-in-space) were recorded in the head-free cat after the GABA agonist muscimol was unilaterally injected into the caudal part of the fastigial nucleus. 4. Gaze saccades towards the inactivated side were hypermetric. These ipsiversive movements overshot the target by a constant error, regardless of target eccentricity and initial gaze position. 5. Gaze saccades directed away from the inactivated side undershot the target. The degree of hypometria increased when the amplitude of the required movement increased. 6. These results suggest a different contribution of the caudal fastigial nucleus to the accuracy of visually triggered gaze shifts, depending on the direction of the impending saccade. The systematic error of ipsiversive movements and the inappropriate movements evoked by presenting a target at the same physical location as gaze reveal that fastigial inactivation interfered with the processes that encode the location of a visual target.

A technique of color restoration for faded color films with whitelight optical processing is presented. The color restoration can be accomplished with spatial encoding and color filtering. Although the technique offers an advantage of faded color encoding, however, it is not a real-time technique. We have also presented a real-time color restoration with white-light optical processing technique. Experimental demonstrations of this color restoration technique are also included. We have shown that the white-light color restoration is a simple, versatile and economical technique. The white-light processing technique also offers the advantage of direct viewing capability, which is very suitable for instantaneous color restoration and enhancement applications.