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S Christ

Publications and source records attributed to S Christ.

7 recordsLinked to original sources
PubMed2000

ERP components on reaction errors and their functional significance: a tutorial.

Some years ago we described a negative (Ne) and a later positive (Pe) deflection in the event-related brain potentials (ERPs) of incorrect choice reactions [Falkenstein, M., Hohnsbein, J., Hoormann, J., Blanke, L., 1990. In: Brunia, C.H.M., Gaillard, A.W.K., Kok, A. (Eds.), Psychophysiological Brain Research. Tilburg Univesity Press, Tilburg, pp. 192-195. Falkenstein, M., Hohnsbein, J., Hoormann, J., 1991. Electroencephalography and Clinical Neurophysiology, 78, 447-455]. Originally we assumed the Ne to represent a correlate of error detection in the sense of a mismatch signal when representations of the actual response and the required response are compared. This hypothesis was supported by the results of a variety of experiments from our own laboratory and that of Coles [Gehring, W. J., Goss, B., Coles, M.G.H., Meyer, D.E., Donchin, E., 1993. Psychological Science 4, 385-390. Bernstein, P.S., Scheffers, M.K., Coles, M.G.H., 1995. Journal of Experimental Psychology: Human Perception and Performance 21, 1312-1322. Scheffers, M.K., Coles, M. G.H., Bernstein, P., Gehring, W.J., Donchin, E., 1996. Psychophysiology 33, 42-54]. However, new data from our laboratory and that of Vidal et al. [Vidal, F., Hasbroucq, T., Bonnet, M., 1999. Biological Psychology, 2000] revealed a small negativity similar to the Ne also after correct responses. Since the above mentioned comparison process is also required after correct responses it is conceivable that the Ne reflects this comparison process itself rather than its outcome. As to the Pe, our results suggest that this is a further error-specific component, which is independent of the Ne, and hence associated with a later aspect of error processing or post-error processing. Our new results with different age groups argue against the hypotheses that the Pe reflects conscious error processing or the post-error adjustment of response strategies. Further research is necessary to specify the functional significance of the Pe.

Adult↗
PubMed2000

Different error types and error processing in spatial stimulus-response-compatibility tasks: behavioural and electrophysiological data.

We tested the hypothesis that in spatial stimulus-response-compatibility (SRC) tasks two different error types occur: A noise-induced 'general error' independent of SRC and reaction time and a 'position driven error' in incompatible trials with short RT being driven by the irrelevant stimulus position. A second issue was whether error detection is different for these two types of errors, which should be reflected by differences in the error negativity (Ne), since the Ne is seen as a neural correlate of error detection. To study these issues, we used a Simon- and a spatial Stroop-task. In incompatible (vs. compatible) trials we found more errors and a below chance accuracy in fast responses. Neither the amplitude nor the latency of the Ne were significantly affected by the experimental factors. This pattern of behavioural results supports the above hypothesis of two error types in such tasks. The Ne results indicate that error detection is similar for both types of errors.

Adult↗
PubMed1997

Anti-human epithelial antigen (Ber-EP4) helps define basal cell carcinoma masked by inflammation.

BACKGROUND: Anti-human epithelial antigen (Dako-Ber-EP4) is an antibody raised in mice that reacts with two glycoproteins of 34 and 49 kD. These glycoproteins are present on the cell surface and in the cytoplasm of basal cell carcinoma (BCC) cells, sweat glands, and some hair follicles in the skin. METHODS: We selected 27 BCCs (15 nodular, 11 morpheic/infiltrative, and one adenoid) and one trichoblastoma and performed rapid immunohistochemical studies with Ber-EP4 and a labeled streptavidin biotin alkaline phosphatase system. RESULTS: Twenty-seven of 27 BCCs and one of one trichoblastoma were positive for Ber-EP4. Thirteen of 27 BCCs stained with Ber-EP4 showed areas of BCC in dense inflammation that were better defined by the Ber-EP4 immunostain than by the H&E stain. In two cases persistent infiltrative BCC was found in the final Mohs margins while appearing negative with routine H&E. Several instances occurred where negative Ber-EP4 in inflammatory fields resulted in tissue sparing with the avoidance of a further Mohs (insurance) layer. CONCLUSION: In conclusion, we found mouse anti-human Ber-EP4 a useful and reliable marker for BCC. This antibody helps to locate latent BCC tumor in inflammatory Mohs margins.

Animals↗
PubMed1986

[Serum sialic acid levels in cancer, pregnancy and upper respiratory infections].

A significant increase in sialic acid content is demonstrable in the sera of cancer patients. Our investigations were performed to find out whether the serum sialic acid level is altered also during pregnancy or with infections of the upper respiratory tract. Our results have revealed a slight increase in sialic acid level to occur only in the last trimester of pregnancy. However, this distinct, though statistically insignificant, increase will not lead to misjudgement in regard to cancer diagnosis, or in case control of this disease. By contrast, in 7 out of 15 patients with infected upper respiratory tract the sialic acid content was clearly above the tolerance limit so that false positive findings may possibly be obtained.

Abortion, Threatened↗