+1 Recommend
1 collections
      • Record: found
      • Abstract: found
      • Article: found

      Incremental Threshold as Obtained by the Visually Evoked Cortical Potential (VECP)

      Read this article at

          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.


          Measurements were made of the range of threshold (dl) in response to a blue (451 nm) and a green (550 nm) monochromatic test light during exposure to step-wise increased backgrounds of illumination Photopic vision (I) in man. Criterion was the increment of radiation power of a test stimulus necessary for a threshold sensation and for a constant latency of the negativity N<sub>2</sub> of the visually evoked cortical potential (VECP). In darkness and at low background illumination (below log –0.70 td) latencies were linearly related to the radiation power of the test light between 200 and 280 msec. At higher levels of illumination a similar relation was seen for latencies between 125 and 200 msec. Within the low and the high range of background illumination dl/I curves were obtained for a criterion latency of 240 msec (low background illumination) and of 170 msec (high background illumination). At background illumination above the transition point (log ––0.70 td) the change of threshold for blue was greater than for the green test stimulus indicating a Purkinje shift in the VECP. For the sensory measurement the dl/I curves for the blue and green test stimuli were seen to split into branches at background illumination of log ––0.70 td, i.e. at the transition point between the scotopic and the photopic range of latencies of the VECP. It is concluded that the determination of incremental threshold is a useful means of separating scotopic and photopic activities of the visual system for physiological and clinical purposes.

          Related collections

          Author and article information

          Ophthalmic Res
          Ophthalmic Research
          S. Karger AG
          27 November 2009
          : 6
          : 1
          : 55-63
          Arbeitsgemeinschaft Abteilung für Experimentelle Ophthalmologie (II.Physiol.Abt.) des Max-Planck-Instituts für Physiologische und Klinische Forschung (Direktor: Prof. E. Dodt), Bad Nauheim und Universitäts-Augenklinik (Direktor: Prof. W. Doden), Frankfurt/Main
          264600 Ophthal Res 1974;6:55–63
          © 1974 S. Karger AG, Basel

          Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

          Page count
          Pages: 9


          Comment on this article