Brightness discriminations with constant duration intermittent flashes.

1962 ◽  
Vol 63 (4) ◽  
pp. 353-360 ◽  
Author(s):  
Robert L. Erdmann
Keyword(s):  
Constant Duration

scholarly journals Characteristic Alterations in Responses to Imposed Wrist Displacements in Parkinsonian Rigidity and Dystonia Musculorum Deformans

1984 ◽  
Vol 11 (2) ◽  
pp. 281-287 ◽  
Author(s):  
W.G. Tatton ◽  
W. Bedingham ◽  
M.C. Verrier ◽  
R.D.G. Blair
Keyword(s):  
Initial Velocity ◽  
Background Activity ◽  
Normal Population ◽  
Emg Activity ◽  
Temporal Modulation ◽  
Normal Response ◽  
Wrist Extension ◽  
Descending Facilitation ◽  
Dystonia Musculorum ◽  
Constant Duration

ABSTRACT:The amplitude and temporal modulation of the segmented EMG activity in flexor carpi radialis, evoked by imposed angular wrist extension, was studied with respect to the level of pre-existing background activity in rigid parkinsonian (PK) and dystonia musculorum deformans (DMD) patients. The interdependence of the evoked M1 and M2-3 segments on pre-existing background EMG activity and initial velocity of imposed displacement was established previously for a normal population. Individual responses of 21 parkinsonian and 12 dystonic patients were compared to the established normal “response volume”. The augmented magnitude of the M2-3 segment in rigid PK patients, which correlates to the measure of rigidity, could not be accounted for by the low level of pre-existing EMG activity. Therefore, increased descending facilitation does not impinge directly on alpha motoneurons. Paradoxical excitation in the shortened muscle and resetting of tonic tremor of the stretched muscle by the imposed wrist extension are two other demonstrated abnormalities which may also contribute to PK rigidity. In contrast, DMD patients demonstrated normal amplitude modulation of the M1 and M2-3 segments, but exhibited a disturbance of normal temporal mechanisms that result in constant duration of the M1 and M2-3 responses with imposed force step loads.

scholarly journals Experimental and theoretical study of velocity fluctuations during slow movements in humans

2019 ◽  
Vol 121 (2) ◽  
pp. 715-727 ◽  
Author(s):  
Emmanuel Guigon ◽  
Oussama Chafik ◽  
Nathanaël Jarrassé ◽  
Agnès Roby-Brami
Keyword(s):  
Control Process ◽  
Arm Movement ◽  
Velocity Profiles ◽  
Optimal Feedback Control ◽  
Movement Speed ◽  
Velocity Fluctuations ◽  
Model Driven ◽  
Movement Trajectories ◽  
Position Signal ◽  
Constant Duration

Moving smoothly is generally considered as a higher-order goal of motor control and moving jerkily as a witness of clumsiness or pathology, yet many common and well-controlled movements (e.g., tracking movements) have irregular velocity profiles with widespread fluctuations. The origin and nature of these fluctuations have been associated with the operation of an intermittent process but in fact remain poorly understood. Here we studied velocity fluctuations during slow movements, using combined experimental and theoretical tools. We recorded arm movement trajectories in a group of healthy participants performing back-and-forth movements at different speeds, and we analyzed velocity profiles in terms of series of segments (portions of velocity between 2 minima). We found that most of the segments were smooth (i.e., corresponding to a biphasic acceleration) and had constant duration irrespective of movement speed and linearly increasing amplitude with movement speed. We accounted for these observations with an optimal feedback control model driven by a staircase goal position signal in the presence of sensory noise. Our study suggests that one and the same control process can explain the production of fast and slow movements, i.e., fast movements emerge from the immediate tracking of a global goal position and slow movements from the successive tracking of intermittently updated intermediate goal positions. NEW & NOTEWORTHY We show in experiments and modeling that slow movements could result from the brain tracking a sequence of via points regularly distributed in time and space. Accordingly, slow movements would differ from fast movement by the nature of the guidance and not by the nature of control. This result could help in understanding the origin and nature of slow and segmented movements frequently observed in brain disorders.

Neural circuits in the flight system of the locust

1985 ◽  
Vol 53 (1) ◽  
pp. 110-128 ◽  
Author(s):  
R. M. Robertson ◽  
K. G. Pearson
Keyword(s):  
Locusta Migratoria ◽  
Motor Pattern ◽  
Short Latency ◽  
Dependent Manner ◽  
Flight System ◽  
Neuronal Connections ◽  
Staining Techniques ◽  
Constant Duration ◽  
To Receive ◽  
Flight Motor

Circuitry in the flight system of the locust, Locusta migratoria, was investigated by use of intracellular recording and staining techniques. Neuronal connections were established by recording simultaneously from neuropile segments of pairs of identified interneurons. Brief depolarizing current pulses delivered to interneurons 301 and 501 reset the flight rhythm in a phase-dependent manner, thus establishing the importance of these neurons in rhythm generation. Interneuron 301 was found to make a strong delayed excitatory connection with 501 and to receive a short-latency inhibitory connection from 501. The circuit formed by 301 and 501 appears suited for promoting rhythmicity in the flight system. The delayed excitatory potential recorded in 501 following each spike of 301 was reversed by hyperpolarizing 501. This potential and short-latency inhibitory postsynaptic potentials from 301 to other interneurons were blocked with the application of picrotoxin. We conclude that the delayed excitation is produced via a disynaptic pathway from 301 to 501, with 301 inhibiting in a graded manner the tonic release of transmitter from one or more unidentified intercalated neurons. Interconnections between the 301-501 circuit and other identified interneurons were discovered. This circuitry can account for two features of the flight motor pattern recorded in deafferented preparations. These features are the constant-latency relationship between depolarizations in elevator and depressor motoneurons and the relatively constant duration of depressor motoneuron bursts. The locust flight system shares general features with other described rhythm-generating systems. These include the occurrence of graded interactions, the probability of multiple oscillatory mechanisms, and a predominance of inhibitory connections. Its uniqueness lies in the way that components and processes are assembled and operate.

PREDICTION OF ONE-HOUR RUNNING PERFORMANCE USING CONSTANT DURATION TESTS

2006 ◽  
Vol 20 (4) ◽  
pp. 735-739 ◽  
Author(s):  
FRANÇOIS XAVIER GAMELIN ◽  
JÉRÉMY COQUART ◽  
NICOLAS FERRARI ◽  
HUBERT VODOUGNON ◽  
RÉGIS MATRAN ◽  
...  
Keyword(s):  
Running Performance ◽  
Constant Duration

Discrimination and Generalization of Rhythmic and Arrhythmic Sound Patterns by European Starlings (Sturnus vulgaris)

1984 ◽  
Vol 1 (4) ◽  
pp. 442-464 ◽  
Author(s):  
Stewart H. Hulse ◽  
John Humpal ◽  
Jeffrey Cynx
Keyword(s):  
Temporal Structure ◽  
Discrimination Performance ◽  
Temporal Patterns ◽  
Test Session ◽  
Sturnus Vulgaris ◽  
Rhythmic Pattern ◽  
European Starlings ◽  
Linear Pattern ◽  
Qualitative Pattern ◽  
Constant Duration

European starlings (Sturnus vulgaris) learned to discriminate patterns of 2000-Hz tones organized into rhythmic as compared with random, arrhythmic temporal structures, and the perceptual processes underlying the discrimination were then analyzed. Two rhythmic patterns were constructed, for different birds, according to a linear rule in which tones and intertone intervals of equal duration alternated or according to a hierarchical rule in which two subpatterns alternated. The arrhythmic pattern was a sequence of tone and intertone intervals each of random duration. The birds were required to peck at one key in the presence of a rhythmic pattern and at another key in the presence of the arrhythmic pattern to obtain food reward. All birds learned the rhythmic–arrhythmic discrimination, and discrimination accuracy was the same for both the linear and hierarchical rhythmic structures. In a series of transfer tests that followed, discrimination performance was tested when the temporal structure of the rhythmic stimulus patterns was transformed and when their pitch was shifted up or down an octave. For temporal transformations, performance was well maintained under (a) a log transformation which, from test to test, changed the absolute duration of tones and intertone intervals but kept their ratios constant (a simple tempo transformation); (b) an additive transformation which kept either tone duration or intertone interval constant from test to test while their counterparts changed in duration; and (c) a pattern interchange in which, for the appropriate birds, the linear was substituted for the hierarchical pattern, or the hierarchical was substituted for the linear pattern. Performance deteriorated (but remained above chance), however, when rhythmic patterns were degraded by holding tone (or intertone) duration constant while intertone (or tone) durations varied randomly within a test session. Performance was also well maintained when the baseline temporal patterns were shifted an octave in pitch, but the data do not necessarily force the conclusion that the birds showed true octave generalization. The results suggest the birds solved the rhythmic–arrhythmic discrimination on the basis of a nominal, qualitative pattern attribute, rhythmicity. Patterns are high in rhythmicity if pattern components are of constant duration within a test session, and if they reoccur periodically. Rhythmicity deteriorates as pattern components vary in duration within a test session and reoccur at varying time intervals. The results also show that the human capacity for discrimination among complex temporal patterns of sound is shared with at least one other species and may, therefore, represent a perceptual process that is—within limits yet to be determined—phylogenetically general.

scholarly journals Pattern and reset analysis of the gastric mill rhythm in a spiny lobster, Panulirus interruptus

1985 ◽  
Vol 114 (1) ◽  
pp. 71-98
Author(s):  
D. F. Russell
Keyword(s):  
Spiny Lobster ◽  
Activity Level ◽  
Cycle Period ◽  
Gastric Mill ◽  
Panulirus Interruptus ◽  
Terrestrial Locomotion ◽  
Variable Duration ◽  
Burst Pattern ◽  
Constant Duration

The burst pattern of the gastric mill rhythm was studied by varying its cycle period in in vitro preparations comprising the stomatogastric (STG), oesophageal and (paired) commissural ganglia. Reset tests using intracellular polarization of identified STG neurones showed that the CI, LC, GP and GM cells can all strongly affect the cycle period, and therefore apparently play a role in generating the gastric rhythm. Variation in the cycle period could be obtained by: (i) cutting certain input nerves; (ii) relative coordination between the gastric and oesophageal rhythms; or (iii) intracellular polarization of identified STG cells, especially the LC motoneurone. Variation in the cycle period by any of these means showed that the gastric pattern (in such preparations) comprises two basic alternating phases: a variable-duration ‘powerstroke’ and a constant-duration ‘returnstroke’. The powerstroke is taken to include bursts in the LC, GP and GM motoneurones (since they evoke closing of the gastric mill teeth and mastication of food), along with the interburst intervals of the other cells. The durations of all these events co-varies over a large range, as a linear function of the cycle period. The activity level of neurones bursting during the powerstroke is directly proportional to their burst length, and hence appears to be a basic parameter affecting the cycle period. The returnstroke is taken to include bursts in the CP, AM and LG motoneurones (since they evoke opening and resetting of the gastric mill teeth), along with the interburst intervals of the powerstroke cells. All these events tended to assume a fixed duration. The two-part gastric mill pattern can be analogized to other two-part rhythms, e.g. for terrestrial locomotion, in which the load-bearing phase has a variable duration and accounts for most of the variation in the cycle period whereas the unloaded phase tends to assume a constant duration.

Effect of timing of FICO2 changes on ventilatory period in domestic fowl

1979 ◽  
Vol 237 (5) ◽  
pp. R260-R265
Author(s):  
R. D. Tallman ◽  
A. L. Kunz ◽  
D. A. Miller
Keyword(s):  
Domestic Fowl ◽  
Open Loop ◽  
Step Change ◽  
Total Period ◽  
Gas Source ◽  
Normal Breathing ◽  
Ventilatory Pattern ◽  
Proportional Increase ◽  
Constant Duration ◽  
Feedback Algorithm

These experiments were conducted to see if the pacing phenomenon found by Kunz and Miller (Respir. Physiol., 22: 167--177, 1974) in the open-loop, unidirectionally ventilated chicken is important in normally breathing birds. In this study, chickens breathed spontaneously through a tracheostomy from a gas source in which the fraction of CO2 (FICO2) could be rapidly changed. A feedback algorithm kept the FICO2 at 0.05 except for a constant duration pulse (approx 0.6 s) of low FICO2 given tau seconds after the beginning of each inspiration. In all birds tested an increase in tau resulted in a proportional increase of both inspiratory period (TI), expiratory period (TE), and the total period (Ttot). Increases in TI were from 0.5 to 1.0 times the increase in tau. Dynamic expeiments showed TI usually changed on the next breath after a step change in tau, and sinusoidal modulation of tau caused concurrent sinusoidal changes in TI, TE, and Ttot. These findings indicate that the phenomenon that produced pacing in the unidirectionally ventilated birds is important to the ventilatory pattern of normal breathing.

Metachronal exopodite beating in the mysid Praunus flexuosus : a quantitative analysis

1977 ◽  
Vol 198 (1131) ◽  
pp. 139-154 ◽  
Keyword(s):  
Quantitative Analysis ◽  
Strong Coupling ◽  
Phase Relations ◽  
Thoracic Segment ◽  
Computer Assisted ◽  
Restricted Range ◽  
Phase Interaction ◽  
Phase Coupling ◽  
Temporal Parameters ◽  
Constant Duration

The exopodite beating of Praunus flexuosus has been analysed from highspeed photographic records with the use of computer-assisted techniques. Limbs beat with a modified rowing action (figures 2, 3), and follow elliptical paths which facilitate an overlapping sequence of movement (figures 3, 4). Analysis of key temporal parameters indicates that beating occurs within a restricted range of frequencies around 4 Hz (table 1). Each beat cycle is composed of a powerstroke (p. s.), returnstroke (r. s.) and pause (p.), the r. s. being of constant duration in all exopodites (figure 5). P. s. and p show rostrocaudal gradients such that the p. s. is of longer duration and p. shorter in more posterior segments (table 2, figure 6). Ipsilateral phase relations are maintained at around 0.2 (figure 7) with strong coupling between exopodites separated by up to four segments (figure 8). Contralateral phase coupling within segments is also strong, with a dominant antiphase relation (figure 9). However, other stable coupling modes have also been observed (figure 10). The exopodite beat shows some phase interaction with another observed cyclical activity, the baling action of the epipodite on thoracic segment 1 (figure 11). These results are discussed in relation to the properties of other metachronal systems, and particular comparisons are drawn between the performance of exopodites in Praunus and in Homarus larvae (table 3). Possible mechanisms of neuronal coordination are considered.

Exercise intensity: effect on postexercise O2 uptake in trained and untrained women

1991 ◽  
Vol 70 (4) ◽  
pp. 1713-1719 ◽  
Author(s):  
K. E. Chad ◽  
B. M. Quigley
Keyword(s):  
Exercise Intensity ◽  
Respiratory Exchange Ratio ◽  
Cycle Ergometer ◽  
Open Circuit ◽  
Acid Oxidation ◽  
Intensity Effect ◽  
Ergometer Exercise ◽  
Varied Intensity ◽  
Constant Duration

Despite many reports of long-lasting elevation of metabolism after exercise, little is known regarding the effects of exercise intensity and duration on this phenomenon. This study examined the effect of a constant duration (30 min) of cycle ergometer exercise at varied intensity levels [50 and 70% of maximal O2 consumption (VO2max)] on 3-h recovery of oxygen uptake (VO2). VO2 and respiratory exchange ratios were measured by open-circuit spirometry in five trained female cyclists (age 25 +/- 1.7 yr) and five untrained females (age 27 +/- 0.8 yr). Postexercise VO2 measured at intervals for 3 h after exercise was greater (P less than 0.01) after exercise at 50% VO2max in trained (0.40 +/- 0.01 l/min) and untrained subjects (0.39 +/- 0.01 l/min) than after 70% VO2max in (0.31 +/- 0.02 l/min) and untrained subjects (0.29 +/- 0.02 l/min). The lower respiratory exchange ratio values (P less than 0.01) after 50% VO2max in trained (0.78 +/- 0.01) and untrained subjects (0.80 +/- 0.01) compared with 70% VO2max in trained (0.81 +/- 0.01) and untrained subjects (0.83 +/- 0.01) suggest that an increase in fat metabolism may be implicated in the long-term elevation of metabolism after exercise. This was supported by the greater estimated fatty acid oxidation (P less than 0.05) after 50% VO2max in trained (147 +/- 4 mg/min) and untrained subjects (133 +/- 9 mg/min) compared with 70% VO2max in trained (101 +/- 6 mg/min) and untrained subjects (85 +/- 7 mg/min).

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