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Biomedical subjects

E M Robertson

Publications and source records attributed to E M Robertson.

At least 19 recordsLinked to original sources
PubMed2003

Studies in cognition: the problems solved and created by transcranial magnetic stimulation.

The application of transcranial magnetic stimulation (TMS) to investigate important questions in cognitive neuroscience has increased considerably in the last few years. TMS can provide substantial insights into the nature and the chronometry of the computations performed by specific cortical areas during various aspects of cognition. However, the use of TMS in cognitive studies has many potential perils and pitfalls. Although TMS can help bridge the gap between psychological models and brain-based arguments of cognitive functions, hypothesis-driven carefully designed experiments that acknowledge the current limitations of TMS are critical.

Brain↗
PubMed2003

Prefrontal cortex: procedural sequence learning and awareness.

Activation of the prefrontal cortex has been linked to awareness during sequence-learning tasks. A recent study, however, finds activation of the prefrontal cortex during such tasks regardless of awareness. So what is the neurophysiological basis of awareness, and what is the role of the prefrontal cortex in sequence learning?

Awareness↗
PubMed2003

A prospective study of early diagnostic investigations in the diagnosis of ankylosing spondylitis.

This study was designed to assess the relative values current of locally available investigations in the early diagnosis of inflammatory sacroiliitis. Consecutive patients attending routine rheumatology clinics in Aberdeen clinically considered by consultant rheumatologists to have inflammatory back disease but with insufficient criteria to firmly establish a diagnosis of ankylosing spondylitis were included. Patients were assessed using a standard questionnaire, clinical examination of spinal movements, plain radiology of the sacroiliac joints, computerised tomographic scanning of the sacroiliac joints and HLA-B27 typing. Patients were systematically followed up using repeated clinical and radiological examination for five years. Plain film evidence of grade 2 radiological sacroiliitis (bilateral or unilateral) was found to be the most reliable predictor for the development of ankylosing spondylitis satisfying the New York criteria at 5 year follow up. CT scanning and HLA-B27 typing were of no added value in this series and the clinical questionnaire lacked specificity. It is concluded that the combination of clinical history, examination and plain film radiology are currently reliable criteria for diagnosing the subsequent development of ankylosing spondylitis satisfying established criteria.

Adult↗
PubMed2001

Aspects of sensory guidance in sequence learning.

We explored the effects of sensory information upon procedural learning using three versions of the serial reaction-time task (SRTT): a standard task where the position of the stimulus cued the response; a non-standard task where the color of the stimulus was related to the correct response; and a combined task where both the color and position simultaneously cued the response. Despite these differences, each task had the same temporal pattern of a repeating ten-item sequence. We refer to each of these tasks based upon the cues available for guiding learning: position, color, and combined tasks. Procedural sequence learning was greater for the combined than for the other two tasks, suggesting that learning is enhanced when multiple sources of sensory information cue consistently and simultaneously for the same response. Transfer of skill occurred across all the tasks, except from the position to the color task. These results suggest that a fundamental neural algorithm is responsible for acquiring knowledge about a temporal sequence of responses rather than forming an associative relationship amongst stimuli.

Adult↗
PubMed2001

The role of the dorsolateral prefrontal cortex during sequence learning is specific for spatial information.

Many studies have implicated the dorsolateral prefrontal cortex in the acquisition of skill, including procedural sequence learning. However, the specific role it performs in sequence learning has remained uncertain. This type of skill has been intensively studied using the serial reaction time task. We used three versions of this task: a standard task where the position of the stimulus cued the response; a non-standard task where the color of the stimulus was related to the correct response; and a combined task where both the color and position simultaneously cued the response. We refer to each of these tasks based upon the cues available for guiding learning as position, color and combined tasks. The combined task usually shows an enhancement of skill acquisition, a result of being driven by two simultaneous and congruent cues. Prior to the performance of each of these tasks the function of the dorsolateral prefrontal cortex was disrupted using repetitive transcranial magnetic stimulation. This completely prevented learning within the position task, while sequence learning occurred to a similar extent in both the color and combined tasks. So, following prefrontal stimulation the expected learning enhancement in the combined task was lost, consistent with only a color cue being available to guide sequence learning in the combined task. Neither of these effects was observed following stimulation at the parietal cortex. Hence the critical role played by the dorsolateral prefrontal cortex in sequence learning is related exclusively to spatial cues. We suggest that the dorsolateral prefrontal cortex operates over the short term to retain and manipulate spatial information to allow cortical and subcortical structures to learn a predictable sequence of actions. Such functions may emerge from the broader role the dorsolateral prefrontal cortex has in spatial working memory. These results argue against the dorsolateral prefrontal cortex constituting part of the neuronal substrate responsible for general aspects of implicit or explicit sequence learning.

Adult↗
PubMed2000

Neural features of the reach and grasp.

The concept of canonical representations within the motor system has been both supported and refuted using a variety of behavioral studies. Here, based upon neurophysiological data, I discuss the relationship amongst those neuronal substrates of action and the behavioral components of a movement. A novel view of reaching and grasping has been proposed which predicts that movements with similar kinematic and dynamic properties have a similar representation within the nervous system (Smeets & Brenner, 1999). However this is broadly inconsistent with a variety of neurophysiological findings that emphasize the independence amongst representations of action.

Electromyography↗
PubMed1999

Visuomotor adaptation during inactivation of the dentate nucleus.

Recent experiments have suggested that the process of visuomotor adaptation depends on how a visual distortion is introduced. The cerebellum is thought to be involved in adapting to rapidly introduced visual distortions; however its role in adapting to a gradually introduced distortion is unknown. We tested adaptation to a sudden or a gradual introduction of a visual distortion, during reversible inactivation of a monkey's dentate nucleus. There was significant adaptation in both of these tasks without any lignocaine infusion and during saline infusions. However after inactivation the ability to adapt to either visual distortion was slightly impaired. This dysfunction was significant when the visuomotor distortion was introduced over several trials, suggesting that the cerebellum has a differential contribution to visual adaptation depending on the type of visuo-motor disturbance encountered.

Adaptation, Physiological↗
PubMed1997

Multi-joint limbs permit a flexible response to unpredictable events.

The human arm is kinematically redundant, which may allow flexibility in the execution of reaching movements. We have compared reaching movements with and without kinematic redundancy to unpredictable double-step targets. Subjects sat in front of a digitising tablet and were able to view an arc of four targets reflected in the mirror as virtual images in the plane of the tablet. They were instructed to move, from a central starting point, in as straight a line as possible to a target. In one-third of trials, the target light switched to one of its neighbours during the movement. Subjects made 60 movements using shoulder, elbow and wrist and then another 60 movements in which only shoulder and elbow movement were allowed. By restraining the wrist, the limb was made non-redundant. The path length was calculated for each movement. In single-step trials, there was no significant difference between path lengths performed with and without wrist restraint. As expected there was a significant increase in path length during double-step trials. Moreover this increase was significantly greater when the wrist was restrained. The variability across both single- and double-step movements was significantly less while the wrist was restrained. Importantly the performance time of the movements did not alter significantly for single-step, double-step or restrained movements. These results suggest that the nervous system exploits the intrinsic redundancy of the limb when controlling voluntary movements and is therefore more effective at reprogramming movements to double-step targets.

Adult↗
PubMed1994

Can radiologists detect osteopenia on plain radiographs?

The main purpose of this study was to compare subjective estimates of vertebral ostepenia with bone mineral density (BMD) measurements of the same region in 200 (107 male, 93 female) subjects, aged 52-90 years, invited randomly from the community. Standardized plain thoracolumbar radiographs were examined by three senior radiologists, and given a semiquantitative osteopenia score using the method of Saville. The BMD of the anteroposterior (AP) lumbar spine and femoral neck was measured by dual energy X-ray absorptiometry. In addition BMD measurements were compared in subjects without significant vertebral deformity, and those with mild (20-25%) or definite (> 25%) reductions of vertebral height. For the Saville score, intraobserver agreement was moderate to good (kappa 0.46-0.57), and interobserver agreement was fair to moderate (kappa 0.25-0.41). Although the overlap between gradings was considerable, BMD was significantly related to visually estimated osteopenia. Subjects without apparent radiographic osteopenia (Saville grade 0) had a low risk (9-15%), compared to those with definite osteopenia (64-86%), of falling below the lowest quartile of BMD at either the femoral neck or the AP spine. In women (but not men), BMD measured at the hip and spine was related to vertebral deformity.

Absorptiometry, Photon↗
PubMed1993

Computed tomography (CT) appearances of acute pancreatitis presenting as polyarthropathy with subcutaneous fat necrosis.

A case of severe acute pancreatitis presenting with polyarthropathy and subcutaneous nodules but no abdominal pain is described. Abdominal CT showed multiple subcutaneous soft tissue densities which on histological examination were identified as areas of fat necrosis consistent with pancreatic disease. Such CT appearances have not been described previously.

Acute Disease↗
PubMed1989

Low-field (0.08 T) magnetic resonance imaging of the pancreas: comparison with computed tomography and ultrasound.

Seventy-four patients referred for computed tomography (CT) and ultrasound examination with a presumptive diagnosis of pancreatic disease have been studied using a low-field (0.08 T) magnetic resonance (MR) imaging instrument. A further 50 patients being examined for non-pancreatic disease were also examined to assess the appearances of the normal pancreas. All the MR examinations were performed using an interleaved saturation-recovery/short inversion time (TI) inversion-recovery sequence. Part or all of the pancreas was seen in 96% of normal cases. In inflammatory disease, MR was more accurate than either CT or ultrasound for diagnosis, whilst for the demonstration of pancreatic tumours, MR was found to be no better or worse than either CT or ultrasound. The use of specific T1 measurement for soft-tissue characterization was not useful because of the large overlap in values between normal, inflamed and malignant pancreatic tissue. T1 measurement was found to be useful in differentiating different pathological fluids.

Adult↗
PubMed1986

Role of computed tomography in assessing "operability" of bronchial carcinoma.

To try to assess the accuracy of predicting "operability" (as defined by local policy) of bronchial carcinoma 300 patients underwent computed tomography of the thorax in a prospective study. The results of 141 patients showed an agreement between computed tomographic and surgical (including pathological) findings in those patients who had received operations. Most of the other patients had more advanced disease than suggested by the findings of computed tomography. A total of 118 patients did not receive operations: in 47 their disease was considered to be inoperable on the basis of computed tomographic findings alone, and this was accepted by the cardiothoracic surgeons after consultation. Thirty two other patients had further evidence of metastatic disease on other investigations. Computed tomography of the thorax should be performed early in the assessment of operability of patients with bronchial carcinoma and before the start of an extensive search for metastatic disease.

Carcinoma, Bronchogenic↗