Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are two noninvasive methods commonly used to study neural mechanisms supporting visual attention in humans. Studies using these tools, which have complementary spatial and temporal resolutions, implicitly assume they index similar underlying neural modulations related to external stimulus and internal attentional manipulations. Accordingly, they are often used interchangeably for constraining understanding about the impact of bottom-up and top-down factors on neural modulations. To test this core assumption, we simultaneously manipulated bottom-up sensory inputs by varying stimulus contrast and top-down cognitive modulations by changing the focus of spatial attention. Each of the male and female subjects participated in both fMRI and EEG sessions performing the same experimental paradigm. We found categorically different patterns of attentional modulation on fMRI activity in early visual cortex and early stimulus-evoked potential...

Brain [Na+] has been proposed to assess insult duration in evolving stroke. Advances in sodium MRI make possible the measurement of the rate of [Na+] increase in a rat model of cortical ischemia. In five Sprague-Dawley rats (~400 g) focal cortical ischemia was induced with occlusion of the distal left middle cerebral artery and both common carotid arteries under isoflurane anesthesia. Sodium 3D data were acquired on a 3 T whole body scanner (GE MS), using a dual-tuned (23Na/1H), dual-quadrature birdcage RF coil. [Na+] maps (twisted projection) were acquired every 5.3 min from which the [Na+] in the ischemic and normal cortex was measured. The infarct was located using T2-weighted 1H images and immunoreactivity to MAP2 (HM2 ab, Sigma). The figure shows the time course of the [Na+] from the ischemic and normal cortex for one animal. [Na+] did not increase in normal cortex (0.02 ± 0.03 %/hr). In ischemic cortex, [Na+] increased at mean rate of 16 ± 3 %/hr (p < 0.001), comparing favorably with 23 ± 4 %/hr (n =...

Nonhuman primates have proven to be a valuable animal model for exploring neuronal mechanisms of cognitive control. One important aspect of executive control is the ability to switch from one task to another, and task-switching paradigms have often been used in human volunteers to uncover the underlying neuronal processes. To date, however, no study has investigated task-switching paradigms in nonhuman primates during functional magnetic resonance imaging (fMRI). We trained two rhesus macaques to switch between arm movement, eye movement, and passive fixation tasks during fMRI. Similar to results obtained in human volunteers, task switching elicits increased fMRI activations in prefrontal cortex, anterior cingulate cortex, orbitofrontal cortex, and caudate nucleus. Our results indicate that the macaque monkey is a reliable model with which to investigate higher-order cognitive functioning such as task switching. As such, these results can pave the way for a detailed investigation of the neural basis of com...

Human cognitive abilities decline with increasing chronological age, with decreased explicit memory performance being most strongly affected. However, some older adults show “successful aging,” that is, relatively preserved cognitive ability in old age. One explanation for this could be higher brain-structural integrity in these individuals. Alternatively, the brain might recruit existing resources more efficiently or employ compensatory cognitive strategies. Here, we approached this question by testing multiple candidate variables from structural and functional neuroimaging for their ability to predict chronological age and memory performance, respectively. Prediction was performed using support vector machine (SVM) classification and regression across and within two samples of young ( N  = 106) and older ( N  = 153) adults. The candidate variables were (1) behavioral response frequencies in an episodic memory test; (2) recently described functional magnetic resonance imaging (fMRI) scores reflecting pres...

We previously reported that manual acupuncuture results in biphasic activation of specific CNS regions. In the present study we employed a continuous 25 min Electro-Acupuncture (EA) stimulation to examine the brain responses associated with attaining acupuncture-induced analgesia. Ten subjects were studied,all signed our institution’s human subject protection (IRB) form. The study consisted of three conditions: EA acupuncture of two analgesia-related acupoints (LI-4, St-36), EA of a sham acupoint, and no stimulation. EA (2Hz) was applied for 25 minutes. Analgesia was assessed by determining a heat pain threshold for each subject before and after the test situations. Brain imaging was done on a Siemens 3T head only (Allegra) scanner with a standard bird-cage coil. Images were taken every 5 minutes. Data was analyzed using SPM99 and AFNI.We measured changes in activation volume for the 25 min and at each 5min step. FFT was used to determine changes in oscillation frequency and/or amplitude. The following reg...

Ischemic brain injury develops from a complex sequence of pathological events that evolve over time. Authors tried to assess the changes and progress of ischemia in photothrombotic ischemia model using MRI and histological analysis and to provide the information regarding the timing and effect of therapeutic intervention researches. Photothrombotic ischemia was induced in the motor cortex of Sprague-Dawley male rat using Rose Bengal dye (20mg/kg) and cold light. MRIs including T1-weighted(T1W), T2- weighted (T2W), Diffusion-weighted imaging (DWI), were obtained using 1.5T MRI and 47mm surface coil at 1, 6, 12, 24 hours, 3, 7, 14, 21. 28, 42, and 56 days. After MRI, rats were sacrificed, and the brain sections were stained with H & E, Nissl, Synaptophysin, and Neurofilament. Infarction volume and contrast-noncontrast ratio (CNR) were measured in all images. Infarction volume was measured the greatest (109mm©ø) on day 1, decreased progressively and reached 8.9mm©ø in 8 weeks. CNR was greatest on 12 hours in ...

We developed experimental techniques to study the neural substrates of goal-directed oculomotor behavior in trained rhesus macaques using a high-field 4.7 T vertical MRI scanner. We recorded BOLD activity, eye movements, reward and timing information while monkeys performed direct and memory saccades to visual cues during GE-EPI scans. Using a saccade vs. fixation block design, we obtained reliable activation maps of cortical and subcortical structures implicated in eye movement control. Next we compared BOLD responses during direct and memory saccades, in order to extract spatial-specific memory and/or planning signals. However, differential activation between memory and direct saccades in the block design was obscured, in part because block activity comprises signals from several task-related components. We therefore utilized an event-related design to delineate contributions from different epochs within the task sequence - presentation of visual cues, motor planning, spatial memory, saccade execution, a...

Explicit and implicit knowledge represent two different types of memory with distinct neural substrates. A key question in the field of memory concerns whether explicit and implicit representations of knowledge are acquired using distinct, overlapping, or partially overlapping networks of brain areas. In the Serial Reaction Time (SRT) task participants learn a sequence of target locations by making button-press responses to cues that follow a repeating sequence. The sequential information can be learned implicitly through practice or can be learned explicitly by memorization. The neural correlates of SRT after these two types of learning were compared in separate groups. The implicit group performed 240 trials of practice without being informed about the repeating sequence. The explicit group memorized the sequence (see Reber et al. 1998, J. Cog Neuro). After training, subjects performed the SRT task during fMRI (3T, TR=2.4, TE=25ms, 44 x 3mm slices) under three intermixed conditions: in response to the tr...

It is controversial about the human somatotopic representation of orofacial areas, especially of the teeth. In addition, some studies of the postcentral somatosensory cortices of the non-human primates support a hierarchical scheme for information processing: the receptive field size and complexity increase with caudal progression. But there are few studies about hierarchical scheme in the orofacial area of the human. To verify human somatosensory orofacial representation including teeth and to show a hierarchal structure of this area, we conducted functional MRI. Tactile stimuli were applied to the forehead, lower lip, chin, tongue, and teeth. Our expectation was that the separated somatotopic representation in the rostral portion of the postcentral gyrus (PoCG) will be merging with caudal progression. Hence we compared the activated foci in the rostral PoCG nearby the central sulcus and those in the caudal portion nearby the postcentral sulcus. The foci activated by each stimulus were characterized by me...

Background: The study of a pair of identical twins, only one of whom had clinical Parkinson s disease (PD), provided an internally-controlled opportunity to assess important function changes related to PD, and the relative responses of the PD after levodopa challenge. This presentation reports the first fMRI study of identical twins discordant for Parkinson’s disease. Methods: 37-year old monozygotic male twins were initially assessed with neuropsychological and motor function batteries. In this fMRI investigation, both siblings performed a sequential finger tapping task with and without visual feedback of their movement before and after levodopa administration. Results: The life and past medical histories of the twins were remarkably similar, except that the non-PD twin had migraine headache since age seven. The PD twin had right arm rigidity, bradykinesia, and resting tremor, whereas the non-PD twin showed no signs of PD. The PD twin had motor, mild learning and executive decrements. In the PD twin, levo...