Biomedical subjects

M J Wright

Publications and source records attributed to M J Wright.

129 records · Page 8Linked to original sources

PubMedDate not supplied

Visual motion and cortical velocity.

Recent studies have revealed some remarkably simple relationships between visual performance and the neuroanatomy of the visual pathways. The visual field is mapped topographically on the surface of the striate cortex in man; the projection is large for the central visual field and is progressively compressed towards the periphery. Visual acuity decreases with distance from the fovea in proportion to the estimated cortical magnification factor, M (the extent of striate cortex in millimetres corresponding to a degree of arc in visual space). If a stimulus is magnified at peripheral locations in proportion to 1/M, it becomes equally resolvable across the visual field. This scaling procedure (M-scaling) maintains equivalence of the cortical projection of stimuli with different visual field loci. We have used M-scaling to investigate motion perception as a visual field variable. We report here that both the lower threshold of motion and adaptation to motion are uniform for M-scaled stimuli, and are related to the velocity of the 'cortical image'.

Humans↗

PubMedDate not supplied

Event-related potential measurement of deficits in information processing following moderate to severe closed head injury.

Event-related potentials may offer more precision than behavioural measures for understanding the extent and timing of information processing difficulties that follow closed head injury (CHI). Behavioural tests consistently indicate a general reduction in cognitive function but lack adequate diagnostic or prognostic function. This study compares a group of seven CHI patients, in which time since injury varied between 1 and 5 years following injury, with 10 matched controls on a three-tone discrimination task. Abnormality in the processing of tones as early as 200 ms following their onset, as measured by the P2 and N2 components of the event-related potential, indicated a general difficulty with tone discrimination. This abnormality was obtained despite differing damage profiles over patients and is likely to be due to the diffuse aspects of damage normal in CHI. These results also indicate that functional deficits in CHI patients can extend up to 5 years or more. A correlation between P2/N2 amplitudes and time since injury, however, suggests that both these components normalize with the passage of time and offers the prospect of a sensitive, non-behavioural measure of recovery in cognitive processing.

Adolescent↗

PubMedDate not supplied

Randomized prospective comparison of laparoscopic and open peritoneal dialysis catheter insertion.

OBJECTIVE: To compare laparoscopic and conventional peritoneal dialysis catheter insertion with respect to post operative discomfort, complication rates, and catheter survival. DESIGN: Randomized prospective study. SETTING: Tertiary referral renal unit. PATIENTS: Fifty patients commencing peritoneal dialysis. INTERVENTION: Catheters were implanted laparoscopically or by a conventional surgical technique. MAIN OUTCOME MEASURES: The duration of surgery, hospital stay, pain scores, and analgesic requirements were recorded. Complications (early/late) and catheter survival were compared. RESULTS: The conventional procedure was faster than the laparoscopic (14.3 vs 21.9 minutes, p < 0.0001). There was no difference in any other parameter assessed. CONCLUSIONS: The data suggest that the insertion techniques are equivalent, and that laparoscopic insertion does not reduce early complication rates.

Catheterization↗