Structural MRIs of the brains of humans with extensive navigation experience, licensed London taxi drivers, were analyzed and compared with those of control subjects who did not drive taxis. The posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects. A more anterior hippocampal region was larger in control subjects than in taxi drivers. Hippocampal volume correlated with the amount of time spent as a taxi driver (positively in the posterior and negatively in the anterior hippocampus). These data are in accordance with the idea that the posterior hippocampus stores a spatial representation of the environment and can expand regionally to accommodate elaboration of this representation in people with a high dependence on navigational skills. It seems that there is a capacity for local plastic change in the structure of the healthy adult human brain in response to environmental demands. O ne important role of the hippocampus is to facilitate spatial memory in the form of navigation (1). Increased hippocampal volume relative to brain and body size has been reported in small mammals and birds who engage in behavior requiring spatial memory, such as food storing (2). In some species, hippocampal volumes enlarge specifically during seasons when demand for spatial ability is greatest (2, 3). In the healthy human, structural brain differences between distinct groups of subjects (for example, males and females, ref. 4, or musicians and nonmusicians, ref. 5) have been documented. From existing studies, it is impossible to know whether differences in brain anatomy are predetermined or whether the brain is susceptible to plastic change in response to environmental stimulation. Furthermore, although lesion work (6, 7) and functional neuroimaging work (8) confirm the involvement of the human hippocampus in spatial memory and navigation, there is still debate about its precise role. Given the propensity of lower mammalian͞avian hippocampi to undergo structural change in response to behavior requiring spatial memory (2, 3), the present study addressed whether morphological changes could be detected in the healthy human brain associated with extensive experience of spatial navigation. Our prediction was that the hippocampus would be the most likely brain region to show changes.Taxi drivers in London must undergo extensive training, learning how to navigate between thousands of places in the city. This training is colloquially known as ''being on The Knowledge'' and takes about 2 years to acquire on average. To be licensed to operate, it is necessary to pass a very stringent set of police examinations. London taxi drivers are therefore ideally suited for the study of spatial navigation. The use of a group of taxi drivers with a wide range of navigating experience permitted an examination of the direct effect of spatial experience on brain structure. In the first instance, we used voxel-based morphometry (VBM) to examine whether morphological changes associated with navigation experience ...

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Global anterograde amnesia is described in three patients with brain injuries that occurred in one case at birth, in another by age 4, and in the third at age 9. Magnetic resonance techniques revealed bilateral hippocampal pathology in all three cases. Remarkably, despite their pronounced amnesia for the episodes of everyday life, all three patients attended mainstream schools and attained levels of speech and language competence, literacy, and factual knowledge that are within the low average to average range. The findings provide support for the view that the episodic and semantic components of cognitive memory are partly dissociable, with only the episodic component being fully dependent on the hippocampus.

Proton nuclear magnetic resonance (1H NMR) spectroscopy is a noninvasive technique that can provide information on a wide range of metabolites. Marked abnormalities of 1H NMR brain spectra have been reported in patients with neurological disorders, but their neurochemical implications may be difficult to appreciate because NMR data are obtained from heterogeneous tissue regions composed of several cell populations. The purpose of this study was to examine the 1H NMR profile of major neural cell types. This information may be helpful in understanding the metabolic abnormalities detected by 1H NMR spectroscopy. Extracts of cultured cerebellar granule neurons, cortical astrocytes, oligodendrocyte-type 2 astrocyte (O-2A) progenitor cells, oligodendrocytes, and meningeal cells were analyzed. The purity of the cultured cells was > 95% with all the cell lineages, except for neurons (approximately 90%). Although several constituents (creatine, choline-containing compounds, lactate, acetate, succinate, alanine, glutamate) were ubiquitously detectable with 1H NMR, each cell type had distinctive qualitative and/or quantitative features. Our most unexpected finding was a large amount of N-acetyl-aspartate (NAA) in O-2A progenitors. This compound, consistently detected by 1H NMR in vivo, was previously thought to ne present only in neurons. The finding that meningeal cells have an alanine:creatine ratio three to four times higher than astrocytes, neurons, or oligodendrocytes is in agreement with observations that meningiomas express a higher alanine:creatine ratio than gliomas. The data suggest that each individual cell type has a characteristic metabolic pattern that can be discriminated by 1H NMR, even by looking at only a few metabolites (e.g., NAA, glycine, beta-hydroxybutyrate).(ABSTRACT TRUNCATED AT 250 WORDS)

The metabolic state of skeletal muscle and brain within intact rats is monitored using high resolution phosphorus nuclear magnetic resonance. Regional disturbances in metabolism (for example, localised ischaemia) are easily observed, indicating the diagnostic possibilities of the method. Measurements are made using 'surface' radiofrequency coils, which we discuss in detail.

Dynamic susceptibility contrast (DSC) MRI is now increasingly used for measuring perfusion in many different applications. The quantification of DSC data requires the measurement of the arterial input function (AIF) and the deconvolution of the tissue concentration time curve. One of the most accepted deconvolution methods is the use of singular value decomposition (SVD). Simulations were performed to evaluate the effects on DSC quantification of the presence of delay and dispersion in the estimated AIF. Both delay and dispersion were found to introduce significant underestimation of cerebral blood flow (CBF) and overestimation of mean transit time (MTT). While the error introduced by the delay can be corrected by using the information of the arrival time of the bolus, the correction for the dispersion is less straightforward and requires a model for the vasculature. Magn Reson Med 44:466–473, 2000. © 2000 Wiley‐Liss, Inc.

Muscular fatigue has been studied using 31PNMR to measure the levels and rates of utilisation of several key metabolites and the free-energy change for ATP hydrolysis. Force development is closely correlated with metabolite levels and is proportional to the rate at which ATP is hydrolysed.

Although observational findings linking breast milk to higher scores on cognitive tests may be confounded by factors associated with mothers' choice to breastfeed, it has been suggested that one or more constituents of breast milk facilitate cognitive development, particularly in preterms. Because cognitive scores are related to head size, we hypothesized that breast milk mediates cognitive effects by affecting brain growth. We used detailed data from a randomized feeding trial to calculate percentage of expressed maternal breast milk (%EBM) in the infant diet of 50 adolescents. MRI scans were obtained (mean age ϭ 15 y 9 mo), allowing volumes of total brain (TBV) and white and gray matter (WMV, GMV) to be calculated. In the total group, %EBM correlated significantly with verbal intelligence quotient (VIQ); in boys, with all IQ scores, TBV and WMV. VIQ was, in turn, correlated with WMV and, in boys only, additionally with TBV. No significant relationships were seen in girls or with gray matter. These data support the hypothesis that breast milk promotes brain development, particularly white matter growth. The selective effect in males accords with animal and human evidence regarding gender effects of early diet. Our data have important neurobiological and public health implications and identify areas for future mechanistic study. (Pediatr Res 67: 357-362, 2010) N umerous studies report that breastfeeding is associated with higher scores on tests of neurodevelopment and cognition in later life (1,2), suggesting that breast milk may impact early brain development, with potentially important biologic, medical, and social implications. These findings are often questioned because other factors associated with mothers' choice to breastfeed (e.g. higher socioeconomic status and level of education, different child-rearing attitudes) might promote cognitive development. In a study using data from a national database, adjustment for maternal intelligence quotient (IQ) eliminated the breastfeeding effect (3). All these studies, however, are potentially flawed by lack of experimental design.More recently, a large cluster randomized trial of breastfeeding promotion using an experimental design demonstrated a large effect of breastfeeding on cognition, adding credence to the evidence for beneficial effects seen in past observational studies (4). Anderson et al. (5) showed in a meta-analysis that, after appropriate adjustments, breastfeeding was associated with an advantage of around three points on tests of cognition in children born at term and around five points in those born preterm, both large effects in population terms. The implication is that, over and above social factors, one or more constituents of breast milk benefit neurodevelopment, particularly so in those born preterm, at a more sensitive stage of brain development.Our current study was prompted by two factors, the now likely causal relationship between breastfeeding and cognition and the previous observation that cognitive scores in preterms are rela...