Hyperspectral analysis for perioperative perfusion monitoring-a clinical feasibility study on free and pedicled flaps.

OBJECTIVES: In reconstructive surgery, flap monitoring is crucial for early identification of perfusion problems. Using hyperspectral imaging (HSI), this clinical study aimed to develop a non-invasive, objective approach for perfusion monitoring of free and pedicled flaps. MATERIAL AND METHODS: HSI of 22 free (FF) and 8 pedicled flaps (PF) in 30 patients was recorded over time. Parameters assessed were tissue oxygenation/superficial perfusion (0-1 mm) (StO2 (0-100%)), near-infrared perfusion/deep perfusion (0-4 mm) (NIR (0-100)), distribution of haemoglobin (THI (0-100)), and water (TWI (0-100)). Measurements up to 72 h were correlated to clinical assessment. RESULTS: Directly after flap inset, mean StO2 was significantly higher in FF (70.3 ± 13.6%) compared with PF 56.2 ± 14.2% (p = 0.05), whereas NIR, THI, and TWI were similar (NIR_p = 0.82, THI_p = 0.97, TWI_p = 0.27). After 24 h, StO2, NIR, THI, and TWI did not differ between FF and PF. After 48 h, StO2, NIR, and TWI did not differ between FF and PF whereas THI was significantly increased in FF compared with PF(p = 0.001). In three FF, perfusion decreased clinically and in HSI, 36(1), 40(2), 5(3), and 61(3) h after flap inset which was followed by prompt intervention. CONCLUSIONS: StO2 < 40%, NIR < 25/100, and THI < 40/100 indicated arterial occlusion, whereas venous problems revealed an increase of THI. In comparison with FF, perfusion parameters of PF were decreased after flap transfer but remained similar to FF later on. CLINICAL RELEVANCE: HSI provides objective and non-invasive perfusion monitoring after flap transplantation in accordance to the clinical situation. With HSI, signs of deterioration can be detected hours before clinical diagnosis.

Three treatments for chronic venous insufficiency: escin, hydroxyethylrutoside, and Daflon.

Escin, hydroxyethylrutoside (HR), and Daflon have been shown to be safe and effective for the treatment of chronic venous insufficiency (CVI). They seem to work differently than compression therapy, suggesting that they would usefully augment this therapy. All three phlebotonics attenuate the drop in adenosine triphosphate in venous endothelial cells during hypoxia. This attenuates (1) the inflammation response, (2) the attraction of neutrophils, (3) damage to the veins, and (4) the release of growth factors. These factors otherwise would perpetuate venous insufficiency and contribute to varicose veins. Additional independent effects that would be useful for the treatment of CVI are that they reduce permeability and fragility; HR, Daflon, and perhaps escin increase venous tone; escin inhibits hyaluronidase; Daflon and probably HR are attracted to the veins. With regard to similarity, no differences in effect have been established among these phlebotonics.

Row blindness in Gestalt grouping and developmental dyslexia.

A classic Gestalt figure is a 4 x 4 array of items grouped by similarity into either rows or columns. We found that some people do not see rows ("row blindness"). Furthermore, row blindness correlates with difficulties processing written language--more than half of the college-age dyslexics tested were row blind. Reading difficulties are probably not a cause of row blindness and forming rows by grouping is a part of reading, suggesting that row blindness might be one source of problems processing written language.

Implicit learning and concept learning.

In Experiments 1 and 2, subjects were exposed to letter strings that followed a pattern--the second letter was always the same. This exposure was disguised as a test of immediate memory. Following this training, subjects could discriminate new letter strings following the pattern from letter strings not following the pattern more often than would be expected by chance, which is the traditional evidence for concept learning. Discrimination was also better than would be predicted from subjects' explicit report of the pattern, demonstrating the co-occurrence of concept learning and implicit learning. In Experiment 3, rules were learned explicitly. Discrimination was worse than would be predicted from subjects' explicit report, validating the implicit learning paradigm. In Experiment 4, deviations from a prototypical pattern were presented during training. In the test of discrimination, prototypes were as familiar as old deviations and more familiar than new deviations, even when considering only implicit knowledge. Experiment 5 found implicit knowledge of a familiar concept. These results are consistent with the hypothesis that the distinguishing features of a concept can be learned implicitly, and that one type of implicit learning is concept learning.

Accepting the null hypothesis.

This article concerns acceptance of the null hypothesis that one variable has no effect on another. Despite frequent opinions to the contrary, this null hypothesis can be correct in some situations. Appropriate criteria for accepting the null hypothesis are (1) that the null hypothesis is possible; (2) that the results are consistent with the null hypothesis; and (3) that the experiment was a good effort to find an effect. These criteria are consistent with the meta-rules for psychology. The good-effort criterion is subjective, which is somewhat undesirable, but the alternative--never accepting the null hypothesis--is neither desirable nor practical.

Interestingness.

What makes a statement interesting? In Expts 1 and 2, merely increasing the amount of background knowledge on a topic did not always increase the interest for statements on that topic. However, background knowledge that combined with a statement to create an interesting implicit proposition did increase interest. In Expt 3, the likelihood of an event's occurrence was not a good predictor of its interestingness, whereas there was a good correspondence between interest and changes in the subjects' beliefs. These findings suggest that interest is not a simple function of either unexpectedness or amount of background knowledge. The results are consistent with the hypothesis that statements changing a person's beliefs or confidence in beliefs are interesting.

Recency and the modality effect in immediate ordered recall.

In immediate ordered recall, recency is the improved recall of the last item of a presentation, and the modality effect is the advantage for an acoustic presentation over a subvocalized visual presentation, primarily occurring at the last serial position. Experiment 1 tested grouped presentations. There was a modality effect for the first item of the last group, even though that item was at the third-to-last or fourth-to-last serial position. In Experiment 2, for vocalized presentations of syllables ending in a, recency was larger for staccato speech than legato speech; for subvocalized presentations, there was a substantial recency for the legato style. In Experiment 3, recency was larger for a set of syllables ending in ATE than for a set of syllables ending in AME. These results suggest that recency cannot be explained by the existence of a fixed-capacity store, auxiliary to the auditory short-term store, that retains only some types of presentations. It is suggested instead that recency might reflect an auxiliary method of using the information in the auditory short-term store.

Explanations of grouping in immediate ordered recall.

This article is about grouping in immediate ordered recall. The following findings are reported: (1) grouping a presentation improves recall, even when steps are taken to prevent rehearsal; (2) grouping primarily improves recall of the items adjoining the grouping, creating primacy and recency within groups; and (3) this primacy and recency are found even when single, isolated errors in recall are considered. These results suggest that the effects of grouping cannot be fully explained by rehearsal, chunking, or the number of directions in which an item can be transposed. It is suggested instead that (1) the auditory short-term store contains an unparsed and uncategorized representation that must be parsed and categorized just prior to recall, in a process of recovery; (2) items adjoining the boundary of a presentation are more easily recovered; and (3) grouping creates a boundary within the presentation. To support this explanation, a final experiment demonstrates an interaction between type of stimuli and serial position, with grouping most improving recall of adjoining phonemes.

Issues of representation and limited capacity in the visuospatial sketchpad.

This article is about a visual short-term store called the visuospatial sketchpad (VSSP), which is tested by immediate ordered recall. Several claims are made: first, even for categorizable stimuli such as digits and letters, the representation in VSSP is uncategorized and unparsed. Second, the representation in VSSP is parsed and categorized just prior to recall in a process called recovery. The probability of recovering an item depends upon the fidelity of that item's representation. Third, VSSP has a fixed amount of representational medium which is allocated proportionally to the items in the presentation. When too many items are presented for recall, not all of the items are represented with sufficient fidelity to be recovered, producing the phenomenon of limited capacity.

Issues of representation and limited capacity in the auditory short-term store.

This article makes several related claims about the auditory short-term store (ASTS) tested by immediate ordered recall. The first claim is that the representation in ASTS is uncategorical and unparsed. The second claim is that there is a stage of recovery just prior to recall, in which the information in ASTS is parsed and categorized. Finally, it is proposed that the amount of representational medium in ASTS is fixed and allocated proportionally to each item in the presentation. When too many items are presented, the items are not represented with sufficient fidelity to be recovered, leading to the phenomenon of limited capacity. These claims are contrasted to the predictions of a slot model, in which ASTS is hypothesized to store a fixed number of categorical and parsed items. Novel explanations are given for several phenomena in immediate ordered recall, including the Hebb effect, the correlation between perceptibility and capacity, and serial position curves.

A dissociation of conscious visual imagery and visual short-term memory.

Two people who reported an impaired ability to form conscious visual images were tested. Compared to a control group of college students, these impaired visualizers were not impaired on two tests of visual short-term memory. Furthermore, they retained more digits in visual short-term memory than they could visualize. These results suggests that deficits in the ability to form conscious visual images can arise without visual short-term memory being impaired, and conscious visual imagery should not be equated with visual short-term memory.