The lateral geniculate nucleus (LGN) is the thalamic station in the retinocortical projection and has been studied extensively using single-cell recordings in nonhuman primates. It has proven difficult to activate the human LGN using fMRI due to its small size and deep location. We developed an fMRI paradigm that reliably activated the LGN to study its functions at the neural population level. Seven subjects were scanned in a 3 T head scanner using gradient echo EPI (TR=2s, TE = 30 ms, flip angle = 90 deg.). Checkerboard stimuli that were modulated in temporal frequency (0.5, 7.5, 20 Hz) or contrast (3 to 100%) were presented in alternation to the left or right hemifield in blocks of 16 seconds while subjects passively viewed a central fixation cross. Contrast response functions (CRFs) and temporal frequency functions (TRFs) were obtained in the LGN and in visual areas V1, V2, V3/VP, V3A, MT/MST and V4/TEO. CRFs increased approximately monotonically in the LGN and in visual cortex with a more rapid saturat...

Functional Magnetic Resonance Imaging (fMRI) is a powerful tool for studying brain function in living intact specimen. Thus far it has only been used in mammals and in the case of laboratory animals its use was even restricted to simple stimulation paradigms due to the required anaesthesia. However fMRI has far more potentials such as repeated observations on neuronal information processing during the performance of simple and cognitive tasks. This study explores fMRI to study auditory processing in the thalamic and telencephalic auditory regions in the brain of songbirds. They represent a well documented animal model for vocal learning and related functional changes in the involved brain regions, even under anaesthetised conditions. We exposed anaesthetised male European starlings to various acoustic stimuli with increasing degree of complexity, ranging from white noise to conspecific song. We localised and monitored the auditory brain responses as a function of stimulus exposure time. Field L showed acti...

Introduction: Executive function abnormalities have been described in patients with obstructive sleep apnea (OSA). There is evidence that the prefrontal cortex may be vulnerable in states of disrupted sleep. We describe the results of a functional magnetic resonance imaging study (fMRI) of working memory in 11 patients with OSA. Hypothesis: Impaired executive function in OSA patients is due to regional (dorsolateral prefrontal cortex, DLPFC) dysfunction in the prefrontal cortex. Study design and methods: Prospective clinical and fMRI (Siemens 3T scanner) evaluation of patients with severe OSA. The task paradigm was two runs of a block design verbal 2-back task with each run lasting 13 minutes. 16 slices parallel to the AC-PC line were obtained every 2 seconds. Statistical activation maps were generated using the Brain Voyager software. Results: 11 male patients, mean age 42. Prior to therapy with PAP, 11/11 patients demonstrated poor or absent prefrontal (including DLPFC) activation. Posterior parietal act...

Diffusion tensor imaging (DTI) is a robust magnetic resonance imaging (MRI) method that expands the capabilities of structural MRI beyond volumetric and morphometric investigations toward the characterization of tissue microstructure. The three-dimensional diffusion of water in brain tissue can be

The imaging of soft tissue is important in both the research and clinical diagnosis of damage and disease. Magnetic resonance imaging (MRI) utilizes the electromagnetic energy released from altering the proton spins of hydrogen under changing magnetic f...

Cognitive behavioral strategies (CBS) are used to help chronic pain patients control their level of pain. The goal of this study is to distinguish the neural correlates of two different cognitive strategies: external focus of attention and reappraisal. ...

Functional imaging in awake animals has become an important tool for measuring whole-brain functional connectivity. Unfortunately, the imaging environment is stressful, and the loud noises emanating from the magnetic resonance imaging (MRI) gradients ar...

Dopamine (DA) receptors play a central role in such diverse pathologies as Parkinson's disease, schizophrenia, and drug abuse. We used an amphetamine challenge combined with pharmacologic magnetic resonance imaging (phMRI) to map DA-associated circuitry in nonhuman primates with high sensitivity and spatial resolution. Seven control cynomolgous monkeys and 10 MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-treated parkinsonian primates were studied longitudinally using both positron emission tomography (PET) and phMRI. Amphetamine challenge (2.5 mg/kg, i.v.) in control monkeys increased relative cerebral blood volume (rCBV) in a number of brain regions not described previously, such as parafascicular thalamus, precentral gyrus, and dentate nucleus of the cerebellum. With the high spatial resolution, we were also able to readily identify changes in rCBV in the anterior cingulate, substantia nigra, ventral tegmental area, caudate (tail and head), putamen, and nucleus accumbens. Amphetamine induced decrea...

The growth in using noninvasive multi-modal functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) to characterize perceptual and cognitive processes in the human brain with high spatiotemporal resolution has made understanding th...

The validity of movement kinematics during functional magnetic resonance imaging (fMRI) experiments is poorly controlled due to technical constraints of the imaging environment. To reliably identify brain areas related to simple and complex movement sequences as well as learning related motor performance changes it is important to control carefully for type, speed and accuracy of the performed movement. We present a method designed to record kinematics of drawing-like upper limb movements during functional magnetic resonance imaging. The recording system consists of a translucent plastic board, a plastic pen with fiber optics and a halogen light power source, a CCD camera, a video monitor and a PC with a video grabber card. Our method yields high temporal and spatial resolution of the recorded movement kinematics during fMRI scanning. Control experiments using a commercially available digitizer tablet show a) the reliability of the kinematic data recorded during functional magnetic resonance imaging and b)...