It has been suggested that learning is associated with a transient and highly selective increase in brain gray matter in healthy young volunteers. It is not clear whether and to what extent the aging brain is still able to exhibit such structural plasticity. We built on our original study, now focusing on healthy senior citizens. We observed that elderly persons were able to learn three-ball cascade juggling, but with less proficiency compared with 20-year-old adolescents. Similar to the young group, gray-matter changes in the older brain related to skill acquisition were observed in area hMT/V5 (middle temporal area of the visual cortex). In addition, elderly volunteers who learned to juggle showed transient increases in gray matter in the hippocampus on the left side and in the nucleus accumbens bilaterally.

Type 1 vanilloid receptors (VR1) have been identified recently in the brain, in which they serve as yet primarily undetermined purposes. The endocannabinoid anandamide (AEA) and some of its oxidative metabolites are ligands for VR1, and AEA has been shown to afford protection against ouabain-induced in vivo excitotoxicity, in a manner that is only in part dependent on the type 1 cannabinoid (CB1) receptor. In the present study, we assessed whether VR1 is involved in neuroprotection by AEA and by arvanil, a hydrolysis-stable AEA analog that is a ligand for both VR1 and CB1. Furthermore, we assessed the putative involvement of lipoxygenase metabolites of AEA in conveying neuroprotection. Using HPLC and gas chromatography/mass spectroscopy, we demonstrated that rat brain and blood cells converted AEA into 12-hydroxy- N -arachidoylethanolamine (12-HAEA) and 15-hydroxy- N -arachidonoylethanolamine (15-HAEA) and that this conversion was blocked by addition of the lipoxygenase inhibitor nordihydroguaiaretic acid....

Using functional magnetic resonance imaging, we found that cortical visual motion area MT+/V5 responded to auditory motion in two rare subjects who had been blind since early childhood and whose vision was partially recovered in adulthood. Visually normal control subjects did not show similar auditory responses. These auditory responses in MT+ were specific to motion compared with other complex auditory stimuli including frequency sweeps and speech. Thus, MT+ developed motion-specific responses to nonvisual input, suggesting that cross-modal plasticity can be influenced by the normal functional specialization of a cortical region. Regarding sight recovery after early blindness, our results further demonstrate that cross-modal responses coexist with regained visual responses within the visual cortex.

Repetitive transcranial magnetic stimulation (rTMS) applied over the right posterior parietal cortex (PPC) in healthy participants has been shown to trigger a significant rightward shift in the spatial allocation of visual attention, temporarily mimicking spatial deficits observed in neglect. In contrast, rTMS applied over the left PPC triggers a weaker or null attentional shift. However, large interindividual differences in responses to rTMS have been reported. Studies measuring changes in brain activation suggest that the effects of rTMS may depend on both interhemispheric and intrahemispheric interactions between cortical loci controlling visual attention. Here, we investigated whether variability in the structural organization of human white matter pathways subserving visual attention, as assessed by diffusion magnetic resonance imaging and tractography, could explain interindividual differences in the effects of rTMS. Most participants showed a rightward shift in the allocation of spatial attention af...

This anatomical study presents MRI-based volumetric analysis of all structures of the Medial Temporal Lobe (MTL) including the hippocampus, the amygdala, the temporopolar cortex and the parahippocampal gyrus (perirhinal, entorhinal and parahippocampal cortices) spared after unilateral MTL removal carried out for the treatment of drug-refractory temporal-lobe epilepsy. Such methods already applied to epileptic patients before surgery, have not been used after surgical treatment. Based on the location of the remaining anatomical landmarks, we quantified the volume of all these regions in 40 patients after unilateral MTL resection (right: N= 20; left: N = 20) and in 16 control participants using MRI-based volumetric analysis. The results showed that (1) the mean volumes of these regions contralateral to the epileptic focus were similar to those measured from normal subjects (2) the volumetric measures obtained from the resected side were obviously reduced compared to those from the non-resected side or from n...

We observed smaller volumes in total cerebrum and cerebellar vermis in cross-sectional studies of boys with ADHD. In a longitudinal study (Giedd et al., 1999), we described developmentally related changes in normal brain anatomy. We now examine longitudinal changes in ADHD, to test the hypothesis that anatomic abnormalities reflect medication effects rather than being intrinsic to the disorder. Subjects: ADHD girls (n=33, mean age = 10.0 ± 2.5 y), ADHD boys (n=40, 11.4 ± 3.4 y), normal girls (n=29, 9.9 ± 3.0 y) and normal boys (n=46, 11.1 ± 3.6 y). 17 patients (9 girls) were medication naïve prior to first MRI scan. Methods: All scans were obtained on the same Signa 1.5 T imager at a mean interval of 3.5 y. 56 ADHD children were medicated prior to first scan and throughout. 17 previously unmedicated ADHD Ss were treated naturalistically with stimulants by their own physicians. Results: Although total cerebral & adjusted cerebellar volumes were smaller in ADHD (p<.05), change over time was equivalent in the...

We recently reported the successful use of the early-negative BOLD fMRI signal to map orientation columns in the cat visual cortex. However, the early-negative BOLD response can not be readily used for routine mapping of brain functions because of its low signal-to-noise combined with the need for high spatio-temporal resolution. In this study, we evaluated the feasibility of using perfusion-based fMRI to resolve columnar layouts in the same cat model and compared its spatial specificity with that of the conventional BOLD. The MRI perfusion-based signal is devoid of large draining venous vessels and is derived from a single physiological parameter without the convoluted susceptibility effect present in the BOLD signal. We hypothesized that perfusion-based fMRI is better suited to resolve columnar layouts as it is more spatially localized relative to the conventional BOLD signal. Perfusion-based and BOLD fMRI were performed on 6 cats. The visual stimulus consisted of drifting gratings of 4 orientations (ide...

A common structural MRI abnormality is punctate regions of hyperintensity (HI, also called leukoaraiosis or encephalomalacia) on T2-weighted or FLAIR scans. These abnormalities occur in periventricular white, deep white, and subcortical gray matter, increase in frequency with aging and in specific neurological and psychiatric disorders. Previous research linked HIs to hypoperfusion. To further characterize their pathophysiology, we measured cerebral blood flow (CBF), metabolic rate (CMR), and vascular reactivity (CVR) within the HIs of 26 elderly participants. Hyperintensities were segmented on FLAIR images by a seed-growing algorithm which identified the borders of lesions that had been seeded by an experienced rater. Positron emission tomograms (PET), using O15-H2O and F18-FDG (for measures of CBF and CMR, respectively), were coregistered to the FLAIRs. The CBF scan was repeated during inhalation of 5% carbon dioxide, a potent vasodilator, providing measures of CVR. Anatomical regions were defined on eac...

Albinism causes foveal hypoplasia and an abnormally large number of fibres from temporal retina to cross the chiasmatic midline. Previous MRI work (Schmitz et al 2003 IOVS, 44 16-21) has indicated that the dimensions of the optic chiasm are abnormal in human subjects with albinism. The same subjects also showed a narrowing of the optic nerves and tracts and an increased angle between the nerves and tracts. Thus, abnormal crossing of visual fibres and reduced foveal cell numbers appear to have an effect on the gross anatomy of the optic chiasm. We have made a series of anatomical measurements of the optic chiasm, optic nerves and tracts based on T1-weighted (1x0.98x0.98mm) structural MRI scans of 20 control subjects (mean age, 34±11) and 19 subjects with albinism (mean age, 33±11). Similar to the previous study, we found that the dimensions of the chiasm were different for the two groups (albino width=9.3±1.0mm, control width=11.5±1.9mm , albino height=3.7±0.9mm, control height=3.4±0.7mm), but this only rea...

OBJECTIVE: During EEG acquisition inside a magnet the generation of induced currents causes several technical and human safety issues. We designed an MRI compatible high resistive-lead EEG cap (InkCap) to reduce Specific Absorption Rate (SAR), improve EEG signal, preserve MRI image quality and enhance subject’s convenience. METHODS: The InkCap consists of 3 flexible circuit boards with conductive ink microstrips of 2 kΩ/m resistivity. The sensors have half-rings shape to reduce Eddy currents. Evaluation: 1) SAR simulations were performed on a high-resolution human head model for a wide range of microstip resistivity. 2) Temperature measurements on a human head-shaped agarose gel phantom were conducted with Luxtron equipment. High power TSE sequences at 7T were used comparing the InkCap with standard electrodes. 3) EEG acquisition was performed using a custom-made MRI-compatible EEG system with piezoelectric motion sensors. 4) MR imaging was done at 7T. RESULTS: Simulated SAR values and temperature increase...