Neurons responding to the observation of actions performed by others have been described in the superior temporal sulcus (STS), parietal area PF, and prefrontal area F5 (see Rizzolatti and Craighero, Ann Rev Neurosci., 2004). In the present study we defined the whole cortical circuit underlying action observation, using contrast-enhanced fMRI in awake macaques. Three macaques (Macaca mulatta) were scanned (1.5Tesla; Siemens Sonata; MION) while they viewed video-sequences of grasping actions. These included object directed human hand actions, human actions using tools, actions performed by a robot hand and mimed human actions. As a control either static images or phase-scrambled sequences were presented. Comparing human actions with their static or phase-scrambled controls, revealed activations throughout the lower bank and the middle part of the upper bank of the STS, in the anterior part of the intraparietal sulcus, extending sometimes laterally on the parietal convexity, and in the posterior bank, fundus...

Blood brain barrier (BBB) integrity is lost several neurological conditions in which astrocytes are damaged. We have studied the focal lesions induced by systemic injection of 3-choloropropanediol, a toxicant that induces early astrocytic (but not neuronal) death followed by BBB leakage. Anatomical images of coronal brain sections illustrate the regional selectivity of the lesions, with affected areas including symmetrical brain stem and midbrain nuclei: primarily the inferior colliculi and red nuclei. The MRI intensity in the lesioned areas peaked at 2 days post-injection, correlating with the later BBB breakdown, and diminished thereafter; returning to close to pre-injection levels by 30 days in parallel with the return of astrocytes. T2 measurements of the lesioned areas increased at 2 days indicating increased water content in the lesioned areas, consistent with cellular damage and BBB leakage. T2 was not increased at 6 hours, a time when astrocyte swelling is marked but the vasculature is intact. Inje...

We used functional Magnetic Resonance Imaging (fMRI) to assess motor recovery in a patient with left middle cerebral artery (MCA) stroke. The patient was scanned on three occasions, at one-month intervals using a finger-sequencing paradigm consisting of both overt movement and movement imagery. Each of these finger-to-thumb opposition tasks were carried out in a prescribed sequence and consisted of three conditions, two unimanual and one bimanual. Although the first session showed more ipsilateral sensorimotor cortex activation during movement using the affected hand, later sessions exhibited more contralateral activation, which conforms to the pattern of the vascular response in normal subjects. However, blood flow to ipsilateral parietal cortex increased over sessions, suggesting that the undamaged parietal cortex took over the function of the affected side, even after improved blood flow to the contralateral sensorimotor cortex. Stronger activation was observed in the motor cortex of the lesion side and...

Optical imaging spectroscopy (OIS), laser Doppler flowmetry (LDF) and magnetic resonance imaging (MRI) were used to investigate the hemodynamic response to neural activation in rat barrel cortex. The MRI measurements were made at 3T in a small animal magnet facility (Magnex with MRRS console). Both fMRI measurements of the BOLD signal and cbv-MRI estimates of changes in blood volume (CBV) were obtained concurrently with measurements of CBF using a magnet compatible LDF probe (Perimed) following both electrical stimulation of the whisker pad (16s,1.2mA @5Hz) and hypercapnic challenge (120s @10% CO2). MRI measurements were obtained using a GRE-EPI sequence at a voxel resolution of 470x470x2000µm. Of necessity, cbv-MRI data was collected after BOLD measurements following infusion of the contrast agent AMI-227 (10mgFe/kg ~200µmol Fe/kg). The BOLD and cbv-MRI data from the hypercapnic challenges were used to estimate the baseline scaling term M=TE.A.CBV0.[Hbr]βv0 used in the biophysical model of the BOLD signal...

Introduction: In the brain of premature infants primary intracerebral hemorrhage (ICH) is a common occurrence. It is usually unilateral and deep in the cerebrum near the ganglionic eminence beside the lateral ventricle. Blood can extend into the ventricles causing hydrocephalus. Even small lesions of this type, are associated with poor developmental outcome including cerebral palsy and mental retardation. The purpose of this study was to obtain magnetic resonance images (MRI) of the mouse brain after ICH and to correlate the images with histological evolution. Methods: ICH was induced in one-day-old mice, which are developmentally similar to a 24-26 weeks human fetus, by injection of autologous blood into the striatum. MRI was obtained 15 minutes to 48 hours later. Mice were perfused with 4% paraformaldehyde 8 hours to 28 days later. H&E, immunohistochemical, and TUNEL staining were used to quantify the lesion area, neutrophils, microglia, and cell death at the edge of the hemorrhagic lesion. Results: Hist...

Co-registering functional brain images across subjects offers experimental advantages and is widely used for studies in humans. Voxel-based co-registration methods require a high-quality 3D template image. Here we describe the formation of T1-weighted structural MRI and PET blood flow template images for baboon and Macaca nemestrina. The images derive from 9 baboons, 12 macaques, and over 500 PET [15O]water scans. Custom software aligns individual MR images to the MRI template using a 12-parameter (affine) model. In the realigned baboon MR images, subcortical test points correspond closely to a photomicrographic atlas with an average error of 1.53mm. Cortical test points on average were within 1.99mm of the mean location for each point. Alignment of individual PET blood flow images directly to the PET template was compared to a two-step alignment process via each subject's MR image. The two transformations were identical within 0.41 mm, 0.54 degrees, and 1.0 percent (translation, rotation, and linear stret...

The relay of nociceptive information through the brainstem to cortical structures has been determined primarily in animals using neuroanatomical and/or electrophysiological techniques. Somatic pain sensation, primarily via peripheral C-fiber stimulation is known to relay in the parabrachial (PB) nucleus of the rostral pons and periaqueductal grey area (PAG) of the midbrain, on its way to the forebrain. This representation of nociceptive information within the brainstem has not yet been demonstrated conclusively in humans. Functional magnetic resonance imaging (fMRI) was used to demonstrate that the PB and PAG are the critical brain stem sites mediating the relay of pain information in the human. Two models of pain were used: electrical stimulation of the ulnar nerve as a model for acute pain and immersion of the left hand in ice-water as an experimental model for chronic pain. Eight subjects were scanned in a 4T functional MRI during the tasks. High resolution (1.5 mm in-plane, 3 mm thick slices) functiona...

Whereas previous imaging research on language has focused largely on single word or single sentence presentation, the current study concerns brain activation that occurs as a result of making forward and backward inferences between two sentences. To accomplish this, participants read pairs of sentences in two activation conditions, inference, where participants judged if the second sentence logically followed the first, and gist match, where participants judged whether the two sentences had the same meaning, and a baseline condition, read-only. As expected, because both tasks required allocation of working memory resources, transformations of verbal material, and maintenance of such materials in memory, the inference and gist conditions activated areas related to the Baddeley-Hitch model of working memory (e.g., bilateral anterior cingulate cortex and left operculum (dorsal and ventral portions)) in both the first and second sentence. The gist condition, in the first and second sentence, activated in regio...

The frontal and the supplementary eye fields (FEF and SEF) play a major role in the cortical control of the voluntary saccades in humans but little is known about anatomical location of the parietal and cingular eye fields (PEF and CEF) in functional MRI. The aim of this study was to obtain detailed information of PEF and CEF activation during voluntary saccades. We investigated the cerebral activation during a horizontal self-paced voluntary saccade task versus central fixation in seven young adult healthy volunteers, using echo-planar fMRI in a 1.5 T scanner. Data were analyzed with SPM99. In addition to FEF and SEF activation, both individual and group analysis disclosed significant activation in two anatomically distinct areas within the cingular cortex (posterior cingular sulcus, anterior cingular sulcus) and bilaterally in three anatomically distinct areas within the parietal cortex (anterior part of the intraparietal sulcus (IPS), posterior part of the IPS, precuneus in the interhemispheric fissure)...

With a paradigm of forepaw stimulation in a rat model, where identical stimulation was repeated with the inter-stimulus interval (ISI) longer than ~600msec, SEP was the same for these stimuli and BOLD signal was proportional to the number of stimuli (between 1 to at least 4). However, when ISI was shorter, the induced SEP was lower and its pattern changed for the successive stimulation events following the first. The corresponding BOLD signal was also reduced and no longer proportional to the number of stimuli. The fMRI signal and the SEP induced by a pair of stimuli showed a neural refractory period lasted longer than 600 msec. In another paradigm where the left and right forepaws were stimulated once each at different times (ISI between 0 to 100 msec), an inhibitive cross-hemisphere interaction appeared in SEP and BOLD signal at ISI of 30-40 msec. We saw similar refractory phenomena in the human brain. With two short visual stimulation pulses, there was observed a neural refractory suppression of the sec...