Maintaining and manipulating sequences online is essential for daily activities such as scheduling a day. In Parkinson's disease (PD), sequential working memory deficits have been associated with altered regional activation and functional connectivity in the basal ganglia. This study demonstrates that the substantia nigra (SN) integrity correlated with basal ganglia function and sequencing performance in 29 patients with PD (17 women) and 29 healthy controls (HCs; 18 women). In neuromelanin-sensitive structural magnetic resonance imaging (MRI), PD patients showed smaller SNs than HCs. In a digit-ordering task with functional MRI (fMRI), participants either recalled sequential digits in the original order (pure recall) or rearranged the digits and recalled the new sequence (reorder and recall). PD patients performed less accurately than HCs, accompanied by the caudate and pallidal hypoactivation, subthalamic hyperactivation, and weakened functional connectivity between the bilateral SN and all three basal g...

We have examined the activity levels produced in various areas of the human occipital cortex in response to various motion stimuli using functional magnetic resonance imaging (fMRI) methods. In addition to standard luminance-defined (first-order) motion, three types of second-order motion were used. The areas examined were the motion area V5 (MT) and the following areas that were delineated using retinotopic mapping procedures: V1, V2, V3, VP, V3A, and a new area that we refer to as V3B. Area V5 is strongly activated by second-order as well as by first-order motion. This activation is highly motion-specific. Areas V1 and V2 give good responses to all motion stimuli, but the activity seems to be related primarily to the local spatial and temporal structure in the image rather than to motion processing. Area V3 and its ventral counterpart VP also respond well to all our stimuli and show a slightly greater degree of motion specificity than do V1 and V2. Unlike V1 and V2, the response in V3 and VP is significa...

Although it is well documented that the ability to perceive biological motion is mediated by the lateral temporal cortex, whether and when neural activity in this brain region is modulated by attention is unknown. In particular, it is unclear whether the processing of biological motion requires attention or whether such stimuli are processed preattentively. Here, we used functional magnetic resonance imaging, high-density electroencephalography, and cortically constrained source estimation methods to investigate the spatiotemporal effects of attention on the processing of biological motion. Directing attention to tool motion in overlapping movies of biological motion and tool motion suppressed the blood oxygenation level-dependent (BOLD) response of the right superior temporal sulcus (STS)/middle temporal gyrus (MTG), while directing attention to biological motion suppressed the BOLD response of the left inferior temporal sulcus (ITS)/MTG. Similarly, category-based modulation of the cortical current source...

The dissociation between magnetic resonance imaging (MRI) and permanent disability in multiple sclerosis (MS), termed the clinicoradiological paradox, can primarily be attributed to the lack of specificity of conventional, relaxivity-based MRI measurements in detecting axonal damage, the primary pathological correlate of long-term impairment in MS. Diffusion tensor imaging (DTI) has shown promise in specifically detecting axonal damage and demyelination in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). To quantify the specificity of DTI in detecting axonal injury, in vivo DTI maps from the spinal cords of mice with EAE and quantitative histological maps were both registered to a common space. A pixelwise correlation analysis between DTI parameters, histological metrics, and EAE scores revealed a significant correlation between the water diffusion parallel to the white matter fibers, or axial diffusivity, and EAE score. Furthermore, axial diffusivity was the primary correlate of q...

Motor control can be divided into automatic and voluntary processes. These processes require planning and preparation in order to deciding in advance to perform one action and not another when a particular sensory event occurs. It is known that the prim...

Binocular disparity provides a strong, unambiguous cue for depth perception in primates. Several cortical areas in both the dorsal and the ventral visual pathways are involved in the processing of depth from binocular disparity. Previous functional magn...

Epochal developmental events like pregnancy and lactation can alter cortical organization and representation affecting memory, perception and attendant behavior. This study used fMRI to observe cortical activation in conscious, first time mother (primiparous) rats in response to pup suckling vs the general tactile stimulus of mechanical rubbing. Pup suckling and general tactile stimulation over the long hair of the ventrum and hairless skin of the nipples and areolas resulted in a similar pattern of cortical activation in primiparous dams. Ventrum rubbing in virgin females activated the same cortical areas. In addition to the anticipated stimulus-evoked activity in the somatosensory cortex, activation was observed in parietal, motor, temporal, cingulate, retrosplenial, auditory and visual cortices for all stimulus conditions. These activations suggest that the stimuli under these experimental conditions were not modality specific and promoted general arousal across the cortical mantel. Interestingly, the s...

Recent work has investigated memory formation during sleep and over extended retention periods. Early formation of associative declarative memories during wakefulness immediately after acquisition of new information has remained largely unexplored. We c...

A characteristic pattern of behavioral and physiological effects is produced by marijuana and its principal psychoactive component, THC, in humans. However, THC’s sites of action in the human brain and their relationships to the drug’s actions are not well described. We have now studied in frequent marijuana users, the effects of two doses of THC (1 and 3 mg iv over 1 min) that produce effects similar to those seen with marijuana use in a social situation, on regional brain activity using BOLD fMRI. The subjects reported that the intensity of the “high” produced by the 3 mg dose was twice that of the lower dose (8/10 vs. 4.5/10). A modest dose-related tachycardia was also observed.Both increases and decreases in brain activity as measured by BOLD fMRI were seen in discrete brain regions. The 3 mg dose of THC produced time-related decreases in fMRI signal in the cerebellum including the region of the dentate nucleus, the middle temporal gyrus and the orbitofrontal region. Decreases were also seen in several...

Obstructive sleep apnea (OSA) is precipitated by atonia of the upper airway muscles and is characterized by extreme loading of airflow, marked diaphragmatic efforts, excessive thoracic and upper airway negative pressures, and significant changes in blood pressure and heart rate. In addition to anatomical factors that enhance obstruction, neural mechanisms that maintain upper airway patency appear defective in the syndrome. We examined the time course of signal changes in neural sites recruited during a challenge approximating the extreme constriction of the airway in OSA, i.e., marked inspiratory loading. A series of 20 image slices (25 repetitions, Echo Planar technique) through the entire brain of 12 male OSA patients (29-59 yrs) and 8 control subjects (29-62 yrs) was collected during 1 min baseline and 1.5 min inspiratory loading challenges in a GE 1.5T Signa scanner. Images collected during baseline and challenge conditions were subjected to a fixed effects analysis using the SPM imaging package. Regio...