Human neuroelectric patterns predict performance accuracy.

In seven right-handed adults, the brain electrical patterns before accurate performance differed from the patterns before inaccurate performance. Activity overlying the left frontal cortex and the motor and parietal cortices contralateral to the performing hand preceded accurate left- or right-hand performance. Additional strong activity overlying midline motor and premotor cortices preceded left-hand performance. These measurements suggest that brief, spatially distributed neural activity patterns, or "preparatory sets," in distinct cognitive, somesthetic-motor, and integrative motor areas of the human brain may be essential precursors of accurate visuomotor performance.

Urinary tract infection and hip fracture.

A routine audit revealed that in 25 per cent of patients with proximal femoral fracture, hospital stay was complicated by urinary tract infection (UTI). A prospective study was undertaken to investigate the relationship of UTI to fracture type, timing of surgery and the effect of perioperative antibiotics. Eighty-eight patients were investigated over a 4-month period with urine specimens obtained at time of operation and 48 h from operation. Of the patients, all female, 12.5 per cent had positive urine cultures at the time of operation. Of all patients, 42 per cent had positive urine cultures 48 h after operation. Females with intra-capsular fractures were more likely to have positive cultures both pre- and post-operatively (P < 0.005). Age (P < 0.05) and operative delay beyond 48 h (P < 0.05) were also found to predispose to infection. All patients except one who had urinary infection at the time of surgery had post-operative urine infection with the same organism. Present audit methods have significantly under estimated the presence of UTI in these patients. Fracture type and operative delay would appear to be the most significant determinants of a positive urine culture 48 h after operation. Prophylactic antibiotics appear to be ineffective in eradicating pre-existing or preventing early post-operative infection.

Self protection in surgery: the use of double gloves.

This study assesses the perforation rate of single and double gloves and thus the extent to which double gloving protects the surgeon from diseases transmissible from the patient. We have also investigated whether double gloving offers the patient extra protection by reducing wound sepsis. Two hundred adult hernia repairs were performed, the first 100 single gloved and the second 100 double gloved. Glove perforation rates were not significantly different between single gloves and the outer of the double gloves. Although 46 of 400 outer gloves were perforated there were only 15 inner glove perforations and only eight of these matched the outer perforations. The percentage of operations in which the latex protective barrier was breached was reduced from 31 per cent when the surgeon wore single gloves to 8 per cent with double gloves. Wound sepsis was not increased by glove perforation nor reduced by double gloving. While careful technique remains mandatory we conclude that double gloving offers increased protection to the surgeon operating on high risk infectious cases.

Improved event-related potential estimation using statistical pattern classification.

A new method of ERP estimation with minimal statistical assumptions is presented. A mathematical pattern classification procedure is used to select trials with discriminable event-related signals in a time interval of interest. A method of forming a reference 'baseline' is also presented. Stimulus-registered and response-registered 'enhanced' ERP averages computed from selected trials of a visuo-motor experiment show substantial enhancement of event-related signals, especially for channels with weak signals, while rejected trials have minimal event-related signals.

Event-related covariances during a bimanual visuomotor task. II. Preparation and feedback.

Event-related covariance (ERC) patterns were computed from pre-stimulus and feedback intervals of a bimanual, visuomotor judgment task performed by 7 right-handed men. Late contingent negative variation (CNV) ERC patterns that preceded subsequently accurate right- or left-hand responses differed from patterns that preceded subsequently inaccurate responses. Recordings from electrodes placed at left frontal, midline antero-central, and appropriately contralateral central and parietal sites were prominent in ERC patterns of subsequently accurate performances. This suggests that a distributed cortical 'preparatory network,' composed of distinct cognitive, integrative motor, somesthetic, and motor components, is essential for accurate visuomotor performance. ERC patterns related to feedback about accurate and inaccurate responses were similar to each other in the interval immediately after feedback onset, but began to differ in an interval spanning an early P300 peak. The difference became even greater in an interval spanning a late P300 peak. For both early and late P300 peaks, ERC patterns following feedback about inaccurate performance involved more frontal sites than did those following feedback about accurate performance. Together with the stimulus- and response-locked results presented in part I, results of this study on the preparatory and feedback periods suggest that ERCs show salient features of the rapidly shifting, functional cortical networks that are responsible for simple cognitive tasks. ERCs thus provide a new perspective on information processing in the human brain in relation to behavior--a perspective that supplements conventional EEG and ERP procedures.

Event-related covariances during a bimanual visuomotor task. I. Methods and analysis of stimulus- and response-locked data.

A new method that measures between-channel, event-related covariances (ERCs) from scalp-recorded brain signals has been developed. The method was applied to recordings of 26 EEG channels from 7 right-handed men performing a bimanual visuomotor judgment task that required fine motor control. Covariance and time-delay measures were derived from pairs of filtered, laplacian-derived, averaged wave forms, which were enhanced by rejection of outlying trials, in intervals spanning event-related potential components. Stimulus- and response-locked ERC patterns were consistent with functional neuroanatomical models of visual stimulus processing and response execution. In early post-stimulus intervals, ERC patterns differed according to the physical properties of the stimulus; in later intervals, the patterns differed according to the subjective interpretation of the stimulus. The response-locked ERC patterns suggested 4 major cortical generators for the voluntary fine motor control required by the task: motor, somesthetic, premotor and/or supplementary motor, and prefrontal. This new method may thus be an advancement toward characterizing, both spatially and temporally, functional cortical networks in the human brain responsible for perception and action.