QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Boyd, M. R. Articles by McClellan, A. D. Search for Related Content PubMed PubMed Citation Articles by Boyd, M. R. Articles by McClellan, A. D. Social Bookmarking                         What's this?

Changes in locomotor activity parameters with variations in cycle time in larval lamprey

Malinda R. Boyd and Andrew D. McClellan

Division of Biological Sciences and Interdisciplinary Neuroscience Program, University of Missouri, Columbia, MO 65211-6190, USA

View larger version (20K): [in a new window]   Fig. 1. Swimming in larval lamprey. (A) Idealized diagram illustrating the sequential movements, from left to right, of a lamprey swimming in a forward direction. (B, top) Diagram of a larval lamprey showing the positions of muscle recording electrodes (1-5). (B, bottom) Idealized locomotor activity generated during swimming, characterized by left-right alternation (12 and 35) and a rostrocaudal phase lag (15, 23 and 34). Parameters of locomotor activity: (i) Cycle time (T), defined as the time interval between successive cycles or bursts, is inversely related to burst frequency f(f=1/T) and swimming speed. (ii) Burst duration (BD) is defined as the interval between the onsets and offsets of bursts. (iii) Burst proportion (BP) is calculated as the ratio of burst duration and cycle time (BD/T). (iv) Burst delay (d) is the interval between rostral and caudal bursts in the same cycle on the same side of the body. (v) Intersegmental phase lag () is calculated as the ratio of burst delay and cycle time divided by (i.e. normalized to) the number of intervening body segments (N) between the recording sites [(d/T)/N].

View larger version (41K): [in a new window]   Fig. 2. (A) Muscle activity (electromyographs) during swimming in a larval lamprey (whole animal). (Ai) Diagram of a larval lamprey with EMG recording electrodes (1-4; see Materials and methods for positions of electrodes). (Aii) Episode of spontaneous locomotor muscle activity, characterized by a left—right alternation (12) and a rostrocaudal phase lag (23 and 34). (B) Locomotor activity in preparations in vitro. (Bi) In vitro brain/spinal cord preparation from a lamprey in which pharmacological agents (5 mmol l-1 D-glutamate/5 mmol l-1 D-aspartate) were pressure-ejected through micropipettes (PER and PEL) in brain locomotor areas to initiate spinal locomotor activity (see Materials and methods for list of source articles), which was recorded from the ventral roots using suction electrodes (1-4). (Bii) Episode of brain-initiated in vitro locomotor activity (1-4; integrated with =50 ms) elicited by pressure ejection (PE) in the rostrolateral rhombencephalon and characterized by left—right alternation (12) and a rostrocaudal phase lag (23 and 34). Note that phase lags for in vitro locomotor activity are smaller than those for locomotor muscle activity in whole animals, as previously reported (McClellan, 1994). Time scale, 1 s (A); 5 s (B).

View larger version (23K): [in a new window]   Fig. 3. Analysis of locomotor muscle activity (EMGs). Distribution histograms of the slopes for (A) BP1-BP5 and (B) 23, 34 and 15 versus cycle time (see Fig. 1B) (N=7-39 animals; see Table 1, left). The slopes of these parameters of locomotor activity versus cycle time were, to a first approximation, normally distributed, which validated use of the Sign test to determine if the composite mean slopes were significantly different from zero (see Materials and methods).

View larger version (21K): [in a new window]   Fig. 4. Analysis of in vitro locomotor activity. Distribution histograms of the slopes for (A) BP1-BP5 and (B) 23, 34 and 15 versus cycle time (see Fig. 2B) recorded from animals (N=4-29 animals; see Table 1, right). As discussed for Fig. 3, use of the Sign test was valid to determine if the composite slopes of these locomotor activity parameters versus cycle time were significantly different than zero.

View larger version (35K): [in a new window]   Fig. 5. (A) Larval lamprey (length=122 mm) with EMG recording electrodes at 20% BL (1,2), 40% BL (3) and 60% BL (4). (B,C) Muscle activity recorded during (B) moderately slow swimming (T=436±42 ms) and (C) faster swimming (T=225±13 ms). Note that the `chart speed' was adjusted so that the cycle times of the two episodes would appear similar in the figure (see time scale below). (B) During slow swimming, the mean burst proportions (BP1, BP2, BP3, BP4) were 0.23, 0.31, 0.39 and 0.31, and mean phase lags (23, 34) were 0.0086 and 0.0047, respectively. (C) During the faster swimming episode, in which the cycle times were approximately 200 ms shorter than in B, the mean values for these parameters were (BP1, BP2, BP3, BP4) 0.28, 0.37, 0.42 and 0.45, and (23, 34) 0.0066 and 0.0063, respectively. Time scale, 500 ms (A); 250 ms (B).

View larger version (43K): [in a new window]   Fig. 6. (A,B) Analysis of locomotor muscle activity from two whole animals (A and B), showing individual data points for burst proportion (BP2 in Ai; BP3 in Bi) and intersegmental phase lag (23 in both Aii and Bii) plotted against cycle time T. Lines are derived from linear regression analysis (see Materials and methods). (C) Linear regression lines for all animals for (Ci) burst proportion, BP2, and (Cii) phase lag, 23. Note that the regression line for each animal is plotted over the range of cycle times that occurred for that given animal.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

Twitter