Functional magnetic resonance imaging (fMRI) was used to study memory-associated activation of medial temporal lobe (MTL) regions in 3 groups: cognitively intact elderly controls (n=10), individuals with mild cognitive impairment (MCI, n=9), and patients with probable Alzheimer’s disease (AD, n=10). Subjects performed a face-name associative encoding task during fMRI scanning, and were tested for recognition of stimuli afterward. High-resolution structural and fMRI data were acquired with a 3T scanner. Two approaches were used to analyze MRI data: statistical parametric mapping of group mean activation and differences between groups, and a functional-anatomic method in which fMRI activation was quantified within MTL regions of interest identified from each individual’s structural MRI. Despite clinical evidence of a history of decline in memory function, MCI subjects performed similarly to controls on the fMRI memory task (85% and 87%, p=0.6); AD patients performed significantly worse (66%, p<0.005). In the...

The brain activity involved in perception of spectrally degraded but intelligible processed speech was studied by using functional magnetic resonance imaging, fMRI. Japanese spoken sentences were spectrally divided into four bands, and then the amplitude envelope was extracted from each band, which was used to modulate noise of the same bandwidth. This processing severely reduced the spectral resolution but preserved the amplitude envelope of each band. Previous studies demonstrated that the present processed speech sound called noise-vocoded speech sound, NVS, was almost unintelligible without any training, but it became intelligible at about 80% level after a brief training. Moreover, prosodic characteristics, such as accents or intonations, normally carried by spectral information were found to be correctly perceived with NVS without F0 or formants. The findings suggest that the brain reconstructs essential cues from the envelope cues to make sentences intelligible. Thus, the neural circuits for making ...

Functional MRI (fMRI) based on blood oxygenation level dependent (BOLD) contrast relies on changes in brain hemodynamics. Recently, a new method for fMRI, named Activity-Induced Manganese Dependent (AIM) MRI, was reported as being independent of hemodynamics. We investigated whether AIM MRI would detect neurotransmitter-induced brain activity in the rat. The aim of this study is to produce new neurotransmitter-sensitive MR contrast. Dopamine (n = 5) and norepinephrine (n = 5) groups were used. The paradigm consisted of 6 steps as follows; 1) T1 weighted (T1W) MRI acquisition without manganese chloride (MnCl2), 2) 25% mannitol injection for BBB disruption, 3) MRI acquisition after MnCl2 and saline injection, 4) same acquisition as #3, 5) MRI acquisition after MnCl2 and neurotransmitter injection, and 6) MRI acquisition after MnCl2 and glutamate injection. There were 3 major results: 1) Neurotransmitter-induced brain activity mapping was successfully performed with phAIM MRI. 2) Dopamine-induced enhancement ...

Several investigators have used motor challenges to study brain function in patients with schizophrenia. We were interested in learning more about the functional brain abnormalities that might underlie the motor difficulties so we performed a meta-analytic review of the functional magnetic imaging (fMRI) literature pertaining to motor tasks. We wanted to answer two questions. First, what is the magnitude of the difference in brain activity between patients and controls in tasks placing demands on primary sensorimotor cortex? Second, is there a reversal of normal primary sensorimotor cortical laterality in patients with schizophrenia? Six studies challenging the motor systems of predominantly right-handed subjects with finger tapping/sequencing tasks provided sufficient fMRI intensity information from which effect sizes (expressed as d-values and interpreted as standard deviation units) could be extracted. From these, we estimated a population effect size for the sensorimotor cortices of each hemisphere by ...

Introduction – Dopamine D2 and D3 receptors have functions of autoreceptors on pre-synaptic neurons to regulate dopamine release. Thus, one expects different responses to antagonists and agonists. We used MRI to show that not only are different signs for the relative cerebral blood volume (rCBV) induced by these agents, but different brain regions are activated. Methods - We used norpropylapomorphine and quinpirole (2mg/kg i.v. for both) as D2 agonists, and eticlopride as a D2 antagonist; 7-OHDPAT (2mg/kg i.v.) as a D3 agonist and a very selective D3 antagonist – SB-277011 A (10 mg/kg i.p.; Stemp et al., J. Med. Chem. 43:1878; 2000). Significant changes in rCBV via a t-test are reported. Results - The D3 agonist 7-OHDPAT produced the large changes in the nucleus accumbens, olfactory tubercule and thalamus (rCBV changes respectively -9.7±2.0%, -17.0± 9.5%, and –7.2±3.9%). The rCBV changes were negative. The D2 agonists quinpirole and norpropylapomorphine induced negative rCBV changes in striatum and accumbe...

A comprehensive characterization of intra-striatal ICH produced in rats by the double-injection method (15 µL fresh arterial blood over 3 min, followed 7 min later by 30 µL over 5 min). Sequential susceptibility-weighted (SWI) and T2 MR imaging was carried out on a 4.7T MRI at 0-1, 6, 24, 72h, and 7 days after induction of ICH. Neurological status before ICH and after treatment (at 4, 24, 48, 72h and 7 days) was graded as previously described1. Following the final MRI study, brains were fixed and re-imaged on an 11.7T MRI and studied by histopathology and immunochemistry. SWI MRI revealed a consistent hematoma involving the striatum and overlying corpus callosum, with significant volume changes over time. Histological hematoma volume at 7d was 5.1±0.1 mm3 (SEM). Other findings included peripheral microglial activation and macrophage infiltration (ED-1), peripheral extracellular iron deposition and hemoxygenase-1 (HO-1) expression; and bilateral astrocytic activation (GFAP). The area of neuronal loss by Neu...

The assessment of hemispheric dominance for language is being carried out after intracarotid administration of sodium amytal (Wada Test). This highly invasive method is not free of risks and is also distressing to the patient. Recent studies in adults have shown a good correlation between language dominance and lateralisation on fMRI. Here we present preliminary data in 6 consecutive patients who underwent Wada testing and fMRI scanning prior to epilepsy surgery. FMRI was performed on a 1.5T Siemens Vision system using a whole brain 3D EPI sequence. Two scans each with a total of 120 data sets were collected. During scanning the subjects silently generated verbs in response to auditory presentation of nouns. fMRI activations (analysed using SPM96b) included: the left inferior frontal gyrus (Broca’s area), premotor cortex and superior temporal gyrus bilaterally. The Wada test was not completed in 2 patients. One patient did not show language-related activation in any of 4 scans performed. Of the remaining 4...

Diabetes mellitus targets the human brain by contributing to the risk of stroke and contributing to white matter abnormalities, demonstrable using magnetic resonance imaging (MRI). In humans, these abnormalities have been associated with cognitive decline as well as subtle impairments in reasoning and coordination skills. We studied an in vivo model of streptozotocin-induced chronic long term (8 months) experimental diabetes in mice and littermate age- and sex-matched controls using MRI. MRI sequences obtained under general anesthesia included T1-weighted images, T2-weighted images and apparent diffusion coefficient (ADC) images. All MRI sequences were assessed blindly. As compared to controls, diabetic mouse brains demonstrated significant differences in T2 multi-echo image values at subcortical regions including striatum, thalamus, amygdala, substantia nigra, as well as hippocampus. Visually identified areas of T2 abnormalities were seen within regions such as the striatum, substantia nigra, and hippocam...

Rhesus monkeys undergo cognitive decline as a function of age, which correlates with the breakdown of axonal myelin. Whether the myelin breakdown is diffuse or specific to individual white matter fiber pathways remains to be clarified. In the present study we investigated the changes in the cingulum bundle using DT-MRI in young (Group 1, N=5), middle-aged (Group 2, N=2), and old (Group 3, N=6) monkeys. METHOD: MRI scanning was performed using a Siemens Sonata 1.5T. Scans included sagittal MP-RAGE pulse sequences and echo-planar DT-MRI. The diffusion tensor, D, was sampled using a seven-shot EPI technique with the following parameters: TR=130ms, TE=80ms, 96 averages, voxel size=1.3x1.3x2.0mm3, b=600s/mm2, 40 contiguous coronal slices for a total acquisition time=66 minutes and SNR=100. RESULTS: The average total cingulum bundle volumes were 0.60cm3 (SD=0.19) in Group 1, 0.75cm3 (SD=0.19) in Group 2, and 0.49cm3 (SD=0.28) in Group 3. The average total cingulum bundle fractional anisotropy (FA) values were 0....

We studied the effects of working memory (WM) on semantic neural systems using event-related functional magnetic resonance imaging (fMRI). Semantic congruency was manipulated using a series of visual sentence pairs with predictable endings. In each pair, the first sentence primed contextual expectation for the terminal word in the second sentence. The second sentence ended with either a semantically appropriate or a semantically inappropriate ending. WM was manipulated by increasing the memory set size. Level 1 WM load contained a single prime sentence and Level 2 contained two prime sentences. Task related activation occurred predominately in the left hemisphere and increased as a function of WM load. Interactions between semantic processing and WM effects were examined within the inferior parietal, superior temporal, lateral frontal, and cingulate regions. The correspondence between the current fMRI results and prior work on the manner in which WM influences the semantic N400 response was examined. Overa...