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F L Steinberg

Publications and source records attributed to F L Steinberg.

15 recordsLinked to original sources
PubMed2006

A parametric fMRI investigation of context effects in sensorimotor timing and coordination.

Mounting evidence suggests that information derived from environmental and behavioral sources is represented and maintained in the brain in a context-dependent manner. Here we investigate whether activity patterns underlying movements paced according to an internal temporal representation depend on how that representation is acquired during a previous pacing phase. We further investigate the degree to which context dependence is modulated by different time delays between pacing and continuation. BOLD activity was recorded while subjects moved at a rate established during a pacing interval involving either synchronized or syncopated coordination. Either no-delay or a 3, 6 or 9s delay was introduced prior to continuation. Context-dependent regions were identified when differences in neural activity generated during pacing continued to be observed during continuation despite the intervening delay. This pattern was observed in pre-SMA, bilateral lateral premotor cortex, bilateral declive and left inferior semi lunar lobule. These regions were more active when continuation followed from syncopation than from synchronization regardless of the delay length putatively revealing a context-dependent neural representation of the temporal interval. Alternatively, task related regions in which coordination-dependent differences did not persist following the delay, included bilateral putamen and supplementary-motor-area. This network may support the differential timing demands of coordination. A classic prefrontal-parietal-temporal working memory network was active only during continuation possibly providing mnemonic support for actively maintaining temporal information during the variable delay. This work provides support for the hypothesis that some timing information is represented in a task-dependent manner across broad cortical and subcortical networks.

Adult↗
PubMed2005

Functional MRI reveals the existence of modality and coordination-dependent timing networks.

Growing evidence suggests that interval timing in humans is supported by distributed brain networks. Recently, we demonstrated that the specific network recruited for the performance of rhythmic timing is not static but is influenced by the coordination pattern employed during interval acquisition. Here we expand on this previous work to investigate the role of stimulus modality and coordination pattern in determining the brain areas recruited for performance of a self-paced rhythmic timing task. Subjects were paced with either a visual or an auditory metronome in either a synchronized (on the beat) or syncopated (off the beat) coordination pattern. The pacing stimulus was then removed and subjects continued to move based on the required interval. When compared with networks recruited for auditory pacing and continuation, the visual-specific activity was observed in the classic dorsal visual stream that included bilateral MT/V5, bilateral superior parietal lobe, and right ventral premotor cortex. Activity in these regions was present not only during pacing, when visual information is used to guide motor behavior, but also during continuation, when visual information specifying the temporal interval was no longer present. These results suggest a role for modality-specific areas in processing and representing temporal information. The cognitive demands imposed by syncopated coordination resulted in increased activity in a broad network that included supplementary motor area, lateral pre-motor cortex, bilateral insula, and cerebellum. This coordination-dependent activity persisted during the subsequent continuation period, when stimuli were removed and no coordination constraints were imposed. Taken together, the present results provide additional evidence that time and timing are served by a context-dependent distributed network rooted in basic sensorimotor processes.

Acoustic Stimulation↗
PubMed2005

Assessing recovery in middle cerebral artery stroke using functional MRI.

PRIMARY OBJECTIVE: To understand the temporal evolution of brain reorganization during recovery from stroke. RESEARCH DESIGN: A patient who suffered left middle cerebral artery stroke 9 months earlier was studied on three occasions, approximately 1 month apart. METHODS AND PROCEDURES: Brain activation was studied using functional Magnetic Resonance Imaging (fMRI). During each session, the patient performed a finger-to-thumb opposition task, which involved one bimanual and two unimanual conditions. Each condition consisted of overt movement of fingers and imagery of the same task. RESULTS: With recovery, greater recruitment was observed of the affected primary motor cortex (M1) and a decrease in activation of the unaffected M1 and supplementary motor area. In addition, the widespread activation of brain areas seen during the initial session changed to a more focused pattern of activation as the patient recovered. Imagery tasks resulted in similar brain activity as overt execution pointing to imagery as a potential tool for rehabilitation.

Aged↗
PubMed2004

Neural substrates of real and imagined sensorimotor coordination.

Much debate in the behavioral literature focuses on the relative contribution of motor and perceptual processes in mediating coordinative stability. To a large degree, such debate has proceeded independently of what is going on in the brain. Here, using blood oxygen level-dependent measures of neural activation, we compare physically executed and imagined rhythmic coordination in order to better assess the relative contribution of hypothesized neuromusculoskeletal mechanisms in modulating behavioral stability. The executed tasks were to coordinate index finger to thumb opposition movements of the right hand with an auditory metronome in either a synchronized (on the beat) or syncopated (off the beat) pattern. Imagination involved the same tasks, except without physical movement. Thus, the sensory stimulus and coordination constraints were the same in both physical and imagination tasks, but the motoric requirements were not. Results showed that neural differences between executed synchronization and syncopation found in premotor cortex, supplementary motor area, basal ganglia and lateral cerebellum persist even when the coordinative patterns were only imagined. Neural indices reflecting behavioral stability were not abolished by the absence of overt movement suggesting that coordination phenomena are not exclusively rooted in purely motoric constraints. On the other hand, activity in the superior temporal gyrus was modulated by both the presence of movement and the nature of the coordination, attesting to the intimacy between perceptual and motoric processes in coordination dynamics.

Acoustic Stimulation↗
PubMed2002

Practice-dependent modulation of neural activity during human sensorimotor coordination: a functional Magnetic Resonance Imaging study.

We investigated the degree to which differences in the pattern of blood oxygen level dependent activity (BOLD) between syncopated and synchronized coordination patterns are altered by practice. Baseline levels of BOLD activity were obtained from eight subjects while they syncopated or synchronized with an auditory metronome at 1.25 Hz. Subjects then practiced syncopation at the same rate for four consecutive sessions. Post practice scans of the two coordination patterns were then performed. Before practice, baseline syncopation activated a much broader network of both cortical and subcortical regions than synchronization that included Supplementary Motor Area (SMA), bilateral putamen, left thalamus, bilateral superior temporal gyrus as well as the vermis. This pattern of activity is hypothesized to reflect the extra timing and attention requirements of syncopation. After practice, activity in superior temporal gyrus and vermis were no longer observed during syncopation reflecting a reduction in the need for attention and the use of sensory feedback for guiding behavior. Surprisingly, post practice synchronization resulted in additional significant activations in SMA, inferior frontal gyrus and superior temporal gyrus as well as small activations in bilateral putamen. Practice with the more difficult syncopation task thus had a dual effect of decreasing the number of active regions during syncopation and increasing the number of active regions during synchronization. Since overt syncopation performance did not change significantly as a result of practice, these observed neural changes appear to be due to context- and history-dependent factors, rather than behavioral learning per se.

Adult↗
PubMed1990

Peripheral vascular and abdominal applications of MR flow imaging techniques.

Many MR flow imaging techniques that have been successfully applied in the carotid arteries and intracranial circulation have been tested in the peripheral and abdominal vasculature. The results have been variable. The lack of success can be attributed to different imaging requirements as well as different patterns of blood flow. These requirements include a large field of view, sensitivity to a wide range of blood flow velocities and complex flow directions, and suppression of overlapping vascular structures and stationary tissue. We have designed strategies using phase contrast MR angiography (MRA) for imaging the arteries and veins of the lower extremity and the abdominal vasculature in normal subjects. This strategy takes advantage of the pulsatile flow pattern present in normal arteries. Overlapping blood flow and stationary tissue were suppressed by a combination of spatial presaturation, optimization of the amplitude and duration of the velocity sensitive gradients, and postprocessing techniques.

Blood Flow Velocity↗
PubMed1990

Penetrating aortic ulcers: diagnosis with MR imaging.

The authors studied seven patients with penetrating aortic ulcers with use of magnetic resonance (MR) imaging. All patients were evaluated for acute chest symptoms, and the presence of aortic ulcers was confirmed by means of angiography in all seven patients. Five patients also underwent computed tomography (CT). Three patients underwent surgical repair of the thoracic aorta. MR findings included intramural hematoma and focal aortic wall ulceration in four patients, focal ulceration in one, focal intramural hematoma in one, and focal intramural hematoma with rupture in one. The diagnosis of intramural hematoma was made by the detection of increased signal intensity on T1- and T2-weighted MR images. MR imaging was superior to angiography in depicting the extent of intramural thrombus, although one ulceration diagnosed at angiography was missed at MR imaging. MR imaging was superior to CT in differentiating acute intramural hematoma from atherosclerotic plaque and chronic intraluminal thrombus, although it did not depict displaced intimal calcification in one patient with extensive intramural hematoma.

Aged↗
PubMed1989

Simon nitinol inferior vena cava filter: initial clinical experience. Work in progress.

The Simon nitinol filter for percutaneous interruption of the vena cava to prevent pulmonary embolism is currently undergoing a multicenter clinical trial. Preliminary clinical results are reported as work in progress. The results in 44 patients at two centers are analyzed in detail, and major events are reported from 103 patients in 17 centers in the United States during a 10-month period. The filter was successfully inserted via the femoral or jugular route in all patients through a 9-F catheter. The placement procedure was easy and without significant complications. Follow-up studies included plain radiography, ultrasonography, magnetic resonance (MR) imaging, and clinical evaluation. No filter migration or perforation occurred among the 103 patients. Symptomatic occlusions occurred in 7%-9%, comparable to other series, and some asymptomatic occlusions were detected with MR imaging only. The implications of occlusion of the filter are discussed.

Adult↗
PubMed1988

Spontaneous aortic dissection in the presence of coexistent or previously repaired atherosclerotic aortic aneurysm.

Acute aortic dissection occurred in 18 patients who had previously diagnosed atherosclerotic aneurysms of the thoracic and/or abdominal aorta. These patients were reviewed to assess the clinical course when these two forms of aortic pathology coexist. Patients were grouped according to status of their atherosclerotic aneurysm (previously repaired vs. untreated) and the segments of the aorta effected by the acute spontaneous dissection. Group 1 patients (n = 5) had previously undergone-abdominal aortic aneurysmectomy (AAA) repair, and the abdominal aortic suture line effectively terminated the dissection process. In Group 2 patients (n = 5), the acute dissection and the atherosclerotic aneurysm involved different segments of the aorta. Group 3 patients (n = 8) experienced spontaneous aortic dissection involving atherosclerotic aneurysms (five infrarenal, three thoracoabdominal), with threatened or actual rupture occurring in six patients, resulting in three deaths. In Group 3 patients, rupture occurred both at the atherosclerotic aneurysm (four patients) and at the site of the aortic intimal tear of the dissection (two patients) after AAA repair. The use of Magnetic Resonance Imaging (MRI) has proven to be highly accurate in delineating the nature and extent of pathology in recently encountered patients with complicated aortic disease. Coexistence of atherosclerotic aneurysm and acute dissection appears to increase the risk of aortic rupture, in both proximal and distal aortic segments.

Acute Disease↗
PubMed1987

The radiology information system: its evolution and current status.

Radiology information systems (RIS) have developed over the past 20 years as a specialized area of medical informatics. Although an increasing number of radiology departments utilize such systems, the majority do not. Perhaps this is because no commercially available system has yet demonstrated its ability to provide cost-effective solutions to the diverse problems of different departments. This review begins with a brief history of RIS to point out some approaches that have proven successful and some that have not. Learning about the historical development of RIS also helps understand many of the features that are found in current systems. The bulk of the article is devoted to a detailed discussion of the functional modules found in RIS, including patient registration and data base management, examination scheduling, process control, film file management, diagnostic reporting, financial packages, and management statistics. These discussions emphasize the wide range of activities and problems found in different radiology departments and the wide range of techniques utilized by RIS. General issues of designing or selecting, installing, operating, and optimizing a RIS are discussed briefly. A final section points out areas for future development and expansion of RIS, giving special attention to the incorporation of digital image information into overall radiology systems.

Appointments and Schedules↗
PubMed1985

Internal derangement of the knee: diagnosis by arthrography, arthroscopy, and arthrotomy.

Three hundred eighty-four cases involving all patients with meniscal or anterior cruciate ligament tears were examined surgically by 16 orthopedic surgeons over two distinct 12-month periods. The incidence of both menisci (ipsilateral knee) torn was 3.9%, and the ratio of medial to lateral meniscal tears was 2.7:1. Twelve percent of cases had tears of the anterior cruciate ligament, 70% of which were found with a concomitant medial meniscus tear. Arthrography was completely accurate in 73.2% of cases, and arthroscopy was accurate in 94.9%. When clinical impression, arthrography, and arthroscopy were combined, the overall diagnostic accuracy was 96.8%.

Arthroscopy↗
PubMedDate not supplied

Two- and three-dimensional phase contrast MR angiography of the abdomen.

Protocols for two- and three-dimensional phase contrast magnetic resonance angiography of the major vessels in the abdomen were developed and demonstrated in healthy volunteers. Phase contrast imaging provides excellent suppression of stationary tissue signal and can be used to quantify the speed and direction of flow in a given vessel. The two-dimensional protocols provide rapid breath-held images, which proved useful for anatomical localization. The three-dimensional studies required longer acquisition times but provided superior image quality. Artifacts from bowel and respiratory motion were not significant with either protocol. Vasculature detected includes the renal, splenic, hepatic, and mesenteric systems as well as the aorta and inferior vena cava.

Abdomen↗
PubMedDate not supplied

Reduction of artifacts from breathing and peristalsis in phase-contrast MRA of the chest and abdomen.

Strategies for the acquisition of temporally resolved phase-contrast angiography are described and demonstrated. Projections are acquired through the entire thickness of the subject permitting excitation geometries to be independent of image orientation. Minimal delays are used between the acquisition of oppositely flow-encoded data resulting in fewer artifacts from movement of nominally stationary tissue. A protocol that suppresses artifacts from both peristalsis and breathing is presented for the aortic arch and iliac arteries.

Abdomen↗