ISSN:
1432-1351
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. Most movement fibers in the crayfish optic nerve show no response during the regular flickering of a stationary light with a flash duration of less than 50 msec when the flash frequency is between 4 and 20 Hz (“habituation”), whereas they do respond with short “off” burst when the flickering stops after a certain number of flashes (“dishabituation”, Fig. 2). 2. The dishabituated response to cessation of regular flicker is not a normal “off” response because the discharge appears about 50 ms after the “missing flash” which would have occurred (Fig. 2). This fact indicates that the dishabituation to cessation of the flicker is entrained to the periodicity of the flicker and locked to the time of the first missing flash (Fig. 3). The features of this “entrained response” are not affected by differences in light intensity or flash duration of the flicker train used for entrainment (Fig. 4). 3. The timing of the entrained response can be shifted by a test flash following the entraining flicker. The entrained response advances when the test flash is given earlier than the expected flash, whereas it lags when the flash is given later. The amount of shift in the response timing is equal to the change in temporal position of the test flash (Fig. 5). The response also advances for a test flash of lower light value (light intensity × flash duration) than that of the entraining flicker, whereas it lags for a flash of higher light value. The amount of shift is proportional to the logarithm of the light value (Figs. 6, 7). 4. It is proposed that the habituation during regular flicker and dishabituation, that is, the entrained response evoked by cessation of the flicker, are both essentially based upon a copying mechanism of the incoming light pattern and a comparison mechanism between the copy and a newly incoming flash. These mechanisms are part of the circuitry of movement fibers (Fig. 11). The accuracy of the periodicity of the entrained activity is better than 5% of the original. 5. The movement fibers also show habituation and dishabituation to stimulus flicker with double periodicities consisting of paired flashes, so that the copying circuit can extract and store more than one periodicity at the same time (Figs. 9, 10).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00657323
