This experiment manipulated digit uncertainty, duration uncertainty, and response duration (dit or dah) in a choice reaction time key press task. A new method of precueing was developed that effectively "precued" the digit and/or the duration of the key press task without confounding the number of stimulus response alternatives with the levels of uncertainty of digit and duration. When the duration of the response was certain, there were no RT differences between dit and dah responses, however, when duration was uncertain, RT to dah responses were longer than dit. In addition, level of duration uncertainty and digit uncertainty produced an overadditive interaction upon RT. These results are discussed in terms of generalized motor programs and a feature construction hypothesis. In addition, these results support the view that precueing of movement dimensions can be accomplished without confounding the number of stimulus response alternatives and the uncertainties of movement dimensions.

The simultaneous control of the hindlimb paw-shake response and hindlimb walking at slow treadmill speeds (0.2-0.4 m/s) was examined in adult cats spinalized at the T12 level, 3-6 mo earlier. Paw shaking was elicited by either 1) application of adhesive tape or 2) water to the right hindpaw. To assess intralimb and interlimb coordination of the combined behaviors, activity from selected flexor and extensor muscles at the hip, knee, and ankle was recorded, and the kinematics of these joints were determined from high-speed cinefilm. When paw shaking was combined with hindlimb walking, the response in the stimulated limb was initiated during swing (F phase) of the step cycle. The onset of knee extensor activity provided the transition from the flexor synergy of swing to the mixed synergy of paw shake. At the end of the paw shake, an extensor synergy initiated the E-1 phase of swing, and the resultant joint motion was in-phase extension at the hip, knee, and ankle to lower the paw for contact with the treadmill belt. During the rapid (81 ms) paw-shake cycles, knee extensor and ankle flexor muscles exhibited single, coactive bursts that were reciprocal with coactive hip and ankle extensor bursts. This mixed synergy was reflected in the limb coordination, as knee flexion coincided with ankle extension and knee flexion coincided with ankle extension. Phasing of hip motions was variable, reflecting the role of the proximal in stabilization during paw shake (16). Although the number of paw-shake cycles combined during swing varied greatly from 2 to 14, average cycle periods, burst durations, and intralimb synergies were similar to those previously reported for spinal cats tested under conditions in which the trunk was suspended and hindlimbs were pendent (23, 27). For step cycles during which a long paw-shake response of 8-14 cycles occurred, swing duration of the shaking limb increased by 1 s, and during this prolonged interval, the contralateral hindlimb completed two support steps. Stance duration of the support steps was also prolonged. This adjustment maximized the duration of paw-contact and minimized any period of nonsupport by the contralateral hindlimb during paw shake. Completion of the paw-shake response was followed by either an alternating, or a nonalternating, gait pattern on the recovery steps. One spinal cat combined locomotion with short two-cycle paw-shake responses, and because the shortened response was limited primarily to the time ordinarily devoted to swing, interlimb adjustments were slight.(ABSTRACT TRUNCATED AT 400 WORDS)

Atkinson et al. (1952) reported the oeciirrenee of two lysogenic strains of S. waycross among 31 tested. The phages from botli strains appeared similar and their general eharacteristics are given in the present paper. METHODS.The phages were isolated by cross-jjlating with strain Currie and subsequently purified by picking single plaques from successive platings on strain Currie. Heat resistance tests and serologieal tests were performed as described by Atkinson and Geytenbeek (1953) for S. adelaide phages except that patch tests instead of plaque counts were used to test the treated phage preparations. Eesistant strains were obtained by growing strain Currie in broth overnight with the phage, plating out the resultant growth and testing separate colonies for susceptibility to lysis by phage and for lysogenicitj'. To detect lysogenicity the test strain was cross-plated with strain Currie, the spot of mixed growth was extracted with a little broth which was centrifuged and then patch tested on strain Currie and the test strain. RESULTS.Isolation and range of action of the phages. Phages were isolated from the two lysogenie strains Cronin and S 215 and labelled W Cr and W 215 respectively. The plaques of each phage were similar but rather heterogeneous in size and extent of secondary growth. However, these variations appeared in single plaque preparations from plaques of various sizes and degrees of secondary growth and seemed to represent various stages in development of the plaques. When tested on our 31 strains of S. ivaycross (described by Atkinson et al., 1950), phages W Cr and W 215 lysed all strains except Cronin and S 215 from which they were derived. The 29 strains which were lysed all came from a single outbreak of gastro-enteritis and were subsequently called S. ivaycross Athci-toii group (see Table 2). Both phages were also tested on a number of Salmonellas representing various 0 groups and on other members of the Enterobacteriaceae.

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