The entorhinal cortex (EC) and hippocampal formation (HF) are pathologically affected very early in Alzheimer’s disease (AD). Therefore, the in vivo quantitation of changes in these regions is of great interest for identifying those at risk for developing AD. In the present study we used proportional odds models to assess the relationship between EC and HF size and risk of incident AD among 58 non-demented elderly people. All participants were followed with yearly clinical evaluations and high resolution MRI scans for up to 6 years. 23/58 people received a diagnosis of amnestic mild cognitive impairment (MCI) during the baseline evaluation and 35/58 had no cognitive impairment (NCI). EC and HF volumes were derived from 1.6 mm gapless T1 weighted coronal images reformatted to be perpendicular to the long axis of the HF. The Analyze software was used for volumetric determinations and the coregistration of sequential scans. Of the 58 non-demented subjects, 14 developed AD during the follow-up period. Results ...

A pregnant viral infection has been considered as one of the etiological factors of neurodevelopmental disorders in offspring. Indeed, maternal immune activation (MIA) by several pseudoviral infections in pregnant mice using polyinosinic:polycytidylic a...

We have embarked on a series of studies lesioning the amygdala in rhesus monkeys to understand its involvement in mediating fear-related psychopathology. Ibotenic acid lesions are preferable because they allow for selective damage and spare fibers of passage. Since these experiments are long term, relying on traditional histopathological verification of lesion extent is problematic. Therefore, we have been exploring noninvasive methods to determine the accuracy and extent of lesions. To assess the validity of using MRI to verify lesions, T2-weighted images were obtained from 5 monkeys at 1,2, and 3 weeks after lesioning. Approximately 9-12 months after surgery, 40 micron thick histological brain sections were obtained, and the extent of histopathological damage was compared with the one week post-surgery MRI data. A Region-of-Interest (ROI) was drawn around the bright signal region on the T2-weighted MRI (indicative of edema). Then the region of actual tissue loss based on each individual's histological da...

It is well documented that gray matter (GM) and white matter (WM) volumes decrease with age, while CSF increases. Statistical Parametric Mapping (SPM) is a widely used method for automated segmentation of brain tissue on MRI images. SPM uses a material mixture model of the distribution of image intensities with initial estimates provided by apriori probablility maps. Tissue volumes are expressed relative to Intra-Cranial Cavity Volume (ICCV) to normalize across different sized brains. Whole brain images of 24 elderly subjects (81.8 +/-6.3 years, 12 men) were acquired with a Siemens 1.5T Magnetom Vision scanner using a 3D MPRAGE sequence (TR/TE1= 11.4s/4.4) with 160-192 sagittal slices yielding 1mm3 voxels. SPM segmentation estimated normalized tissue volume (%ICCV). Individual subject tissue volume results (GM, WM and CSF) and ICCV were correlated with age. Average tissue volumes were 39.3 GM, 30.0 WM and 30.6 CSF %ICCV, though individual results varied substantially. Visual inspection demonstrated that GM...

It has been argued that the longer lasting effects of low-frequency rTMS trains rely on post-synaptic inhibitory GABAergic synapses, but there remains some uncertainty whether an additional pathophysiological mechanism might support this post-synaptic inhibition. In this study, we investigated whether rTMS at 1 Hz administered for 12 minutes at 90% of motor threshold to the primary motor cortex would lead to any changes in cortical diffusivity of water protons by comparing a series of diffusion weighted MRI (DWI) scans acquired before and after the rTMS train. Impairments of water diffusivity can typically be seen in the acute stage of an ischemic insult or focal status epilepticus, and their reversibility has been shown. Preliminary analysis of the diffusion images shows only a minimally increased signal within the motor region in half of the subjects (3 out of 6). This minimal signal change was no longer present 15 minutes after the end of the rTMS train. The initial signal change in some subjects is not...

The Meet-the-Experts Series will continue with live one-hour webinars after the conclusion of Neuroscience 2022, between December 2022 and September 2023.

We used functional MRI to study cerebellar activity during three bimanual coordination tasks: Syncopation at 1.33Hz and synchronization at 1.33Hz and 2.66Hz. Previous research (EEG & MEG) shows that spatiotemporal patterns of brain activation depend on both coordination frequency and the mode of coordination (syncopation or synchronization). Participants coordinated bimanual finger-thumb opposition either on-the-beat (synchronize) or in-between two consecutive beats (syncopate). We used the noise (pings) produced by the scanner (Signa 1.5T, GE Inc.) as auditory stimuli. The repetition time (TR) and number of slices was set in each condition such that the pings took place at the desired frequency, i.e. at 1.33Hz and 2.66Hz. Behavioral performance was monitored as pressure changes in two small air pillows which the subjects were holding between the thumb, and the index and middle finger of each hand. This signal was compared to the time points of pulses produced by the scanner when taking a slice. Results sh...

A salient visual stimulus can be rendered invisible by presenting it to one eye while flashing a mask to the other eye. This procedure, called continuous flash suppression (CFS), has been proposed as an ideal way of studying awareness as it can make a stimulus imperceptible for extended periods of time. Previous studies have reported robust suppression of cortical activity in higher visual areas during CFS, but the role of primary visual cortex (V1) is still controversial. In this study, we resolve this controversy on the role of V1 in CFS and also begin characterizing the computational processes underlying CFS. Early visual cortical activity was measured with functional magnetic resonance imaging while human subjects viewed stimuli composed of target and mask, presented to the same or different eyes. Functional MRI responses in early visual cortex were smaller when target and mask were in different eyes compared with the same eye, not only for the lowest contrast target rendered invisible by CFS, but also...

Diffusion MRI tractography streamlines terminate predominantly at the gyral crown, rather than more uniformly across the cortex as seen in histology. This bias to the gyral crown is generally attributed to the limited resolution of diffusion MRI, which ...

Aniridia is a congenital and progressive disorder affecting approximately 1 in 83,000 live births. Although the disorder is most well known for its ocular phenotypes, the condition has several other abnormalities, which are only recently emerging as pro...