PubMed · 9610161
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A Meymandi. Brain and behavior.. https://pubmed.ncbi.nlm.nih.gov/9610161/
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HYPOTHESIS: Mental strain measured by heart rate variability differs during laparoscopic and conventional sigmoid resections. DESIGN: Prospective randomized study. SETTING: University hospital. PARTICIPANTS: Two surgeons performed 10 conventional and 10 laparoscopic sigmoid resections, alternating roles as primary surgeon and assistant. The kind of technique was randomly chosen each time. INTERVENTION: Electrocardiograms of the surgeon and assistant were continuously recorded during the procedures and heart rate variability was analyzed off-line. The first 10 procedures (5 laparoscopic and 5 conventional) were performed by the more experienced and the next 10 by the less experienced surgeon. MAIN OUTCOME MEASURES: Heart rate variability was determined by power spectral analysis as heart rate in beats per minute, high frequency (HF) and low frequency (LF) components in normalized units, and LF/HF ratio. RESULTS: Results are given for heart rate, HF, LF, and LF/HF ratio for the following variables: laparoscopic surgery: 87.9, 14.7, 90.1, 7.5; conventional surgery: 90.2, 17.1, 87.6, 6.4; surgeon: 94.0, 13.5, 91.4, 8.4; first assistant: 84.1, 17.8, 86.3, 5.6; more experienced surgeon: 93.1, 16.5, 87.8, 6.4; and less experienced surgeon: 85.0, 14.8, 90.0, 7.5. The LF/HF ratio was significantly higher (P<.05) for laparoscopic compared with conventional surgery and for the surgeon compared with the assistant (P<.001), but not between the less and the more experienced surgeons. CONCLUSION: Performing laparoscopic colorectal surgery causes higher mental strain in surgeons than performing conventional surgery.
The literature on time perception is discussed. This is done with reference both to the "cognitive-timer" model for time estimation and to the subjective experience of apparent duration. Three assumptions underlying the model are scrutinized. I stress the strong interplay among attention, arousal, and time perception, which is at the base of the cognitive-timer model. It is suggested that a multiplicative function of two key components (the number of subjective time units and their size) should predict apparent duration. Implications for other cognitive domains are drawn, and in particular an analogy is suggested between apparent duration and apparent movement.
Behavioural studies in patients and functional neuroimaging studies in normal subjects suggest that the right frontal cortex plays an important role in sustaining attention to a task. However, the contribution of different regions of the frontal lobe to performance changes has not been clearly established. First, the assessment of sustained attention has not been carried out in patients with lesions that are restricted to cortical regions of the frontal lobe. Second, although sustained attention is often measured by performance on a task requiring effortful attention, it may be more meaningful to measure changes in performance as a function of time-on-task. Two studies were carried out in five groups of subjects: patients with left or right frontal cortical resections, patients with left or right anterior temporal lobe resections, and normal controls. In the first experiment, a brief (4-min) selective attention task was performed. The right frontal group, unlike the other groups, did not show improved reaction times after the first minute on the task. The second experiment involved a long (30-min) shifting attention task. Both the left and right frontal groups were slower than control groups; however, reaction times in the right frontal group increased with time spent on the task. We conclude that the right frontal cortex plays an essential role in modulating arousal during performance of a task and may also underlie aspects of learning during the early stages of task performance.