PubMed Health⌕ Search

Biomedical subjects

M C Wetzel

Publications and source records attributed to M C Wetzel.

At least 19 recordsLinked to original sources
PubMed1990

Learning and rhythmic human EMG in ecological perspective.

Previous evidence of strong interactions between learning and human treadmill locomotion led to a simplified system for studying learned rhythms in a framework of behavioral ecology. Motor control combined with instrumental conditioning in a rhythmic hand task with repeating trials, blocks, and complete regimens. Regimen contexts differed with respect to the pattern of stimulation before and after an electromyographic (EMG) response. Both an antecedent stimulus (a light flash) and a consequent stimulus (a tone indicating success or failure) were necessary for conditioning. Arguments were given for defining reinforcement as a composite of interdependent and size-scaled processes, some including knowledge of results, instead of as a single event after a response.

Association Learning↗
PubMed1987

Two-muscle coordination versus natural treadmill locomotion.

When a single-muscle learned behavior was superimposed upon natural human treadmill locomotion, in previous work, it operated as a self-contained behavioral unit. The new behavior altered some features, however, of ongoing stepping patterns. These findings prompted broader consideration of how individual muscle actions combine to form large, patterned ensembles. Accordingly, the present experiment constructed a larger, double-muscle learned behavior to see if it would compete with natural treadmill locomotion or combine with it harmoniously. A demanding requirement was made for in-phase bilateral EMG and contraction by rectus femoris (RF), in opposition to its natural out-of-phase interlimb pattern. EMG bursts were controlled, through computer-assisted operant conditioning, by a flash shortly after left heel strike. The new, double ensemble was conditioned rapidly, within 1-6 days, for all four adults. Harmonious stepping continued, for the most part, with little alteration in step cycle timings. Leg positioning was modified appreciably, however, pointing to complex neural mechanisms. The evidence argued that operant conditioning can construct fine-grained behaviors and also participate powerfully across the full range of single- and interlimb coordination.

Adult↗
PubMed1987

Operant conditioning in relation to natural EMG during rapid human walking.

Interactions between specific operant conditioning and ongoing treadmill walking have been characterized in several previous investigations of mechanisms that coordinate locomotion. The present study examined a higher walking velocity in which contractile forces and, by inference, reflex behavior, might be more powerful. Two subjects walked on a motor-driven treadmill at 0.90 m/sec. As in past work, at 0.45 m/sec, a conditioning regimen constructed a test operant in the following way. With training, a green light that flashed approximately 200 msec after heel strike on every third step produced, after operant reinforcement, a 100-500 msec electromyographic burst in the rectus femoris (RF) muscle before the end of a 500 msec performance duration. Reinforcement consisted of a tone that sounded after each response and indicated success or failure. Burst durations were shorter than had been typical at a lower treadmill speed, a characteristic that could favor rapid matching of contractile patterns to more rapidly changing conditions. No evidence was gained of interference from stretch reflexes or any other ongoing inborn behavior. The resulting rapid walk was as well coordinated as that seen at lower velocity, to argue for increased emphasis on the role of learning in normal locomotion and to improve pathological walking.

Adult↗
PubMed1986

Integration of learned and naturally occurring flexor EMG in the human step cycle.

Human locomotion, as a behavioral system, is well suited for investigating the interplay of learning with innate biological mechanisms. The present work assembled, from previous findings, a test battery of operant conditioning to modify strong ongoing electromyographic (EMG) activity of the left tibialis anterior (TA), an ankle flexor muscle. An EMG segment 100-400 msec long had to occur within 700 msec, and (in different training regimens) with filtered amplitude both above and below different thresholds--all in response to a colored light that flashed at a designated time in the step cycle. Reinforcement was a high or low tone that indicated success or failure, respectively. All four subjects met training criteria (90% success rate) at a moderate amplitude, just as had been true previously for a relatively inactive knee extensor. Subject-specific limitations were found in operant control at higher and lower amplitudes. New learning was not disruptive, although ipsilateral swing duration increased, nor was it phase-dependent on any portion of the step cycle.

Conditioning, Operant↗
PubMed1986

Operant conditioning in motor and neural integration.

Empirical and theoretical reasons were given to investigate operant conditioning in a new, integrative approach within motor control physiology. Elements of inborn and learned behavior were presented in a framework specifying their stimuli and responses. The operant was redefined as a controlling discriminative stimulus, Sd, together with the response, R, it produces, on the basis of a previous literature of operant and instrumental research. Complex motor and neural activity were reviewed in accordance with partitioning of: responses, controlling stimulation, reinforcement, and functions of movement-produced stimulation. Schematics portrayed reinforcement principles through analysis of a fast pathway from Ia muscle spindle afferents to motor outflow. Methods were suggested to minimize operant units through selective reinforcement and establish them to defined end points of learning within composite, ongoing behavior. It was argued that operant neural mechanisms can be investigated efficiently only by starting with individual operants that are thoroughly characterized.

Animals↗
PubMed1985

Antibody diversity in fish. Isoelectrofocalisation study of individually-purified specific antibodies in three teleost fish species: tench, carp and goldfish.

Natural anti-DNP antibodies were isolated by affinity chromatography from individual sera of three Cyprinid fish species (carp, goldfish and tench) and their electrofocusing (IEF) spectra were analysed in reducing conditions. In addition, immune anti-penicillin and anti-BSA antibodies were isolated from individual and pooled tench sera, and studied by IEF techniques on reduced samples. Diversity rates appeared to be rather low in the three fish species, and striking similarities arose between individuals of a same species. These results can be interpreted by the existence of particular selective pressures operating in poikilothermic species as it was already suggested by Du Pasquier. No enhancement of antibody heterogeneity could be detected in the tetraploid (carp and goldfish) species. This result is also in accordance with the selection of a restricted germ-line determined antibody repertoire in lower vertebrates.

Animals↗
PubMed1984

Structural and functional analysis of spontaneous anti-nitrophenyl antibodies in three cyprinid fish species: carp (Cyrinus carpio), goldfish (Carassius auratus) and tench (Tinca tinca).

High spontaneous anti-trinitrophenyl (TNP) activities were found in three Cyprinid fish species: Carp (Cyprinus carpio), Goldfish (Carassius auratus) and Tench (Tinca tinca). The molecules involved, isolated by affinity chromatography on dinitrophenyl-lysine Sepharose (DNP-lysine-Sepharose), had the main characteristics of a high molecular weight immunoglobulin (IgM-like). Affinity measurements were performed on natural anti-DNP/TNP antibodies isolated from nine individual tench sera, using the inhibition of DNP-T4 bacteriophage inactivation technique. The antibodies analysed were more specific for TNP than for DNP. No activity was found against paranitrophenyl hapten. Affinities were all very low, even for TNP. In the three species, natural anti-DNP/TNP antibodies constitute as much as 11 to 16% of the total immunoglobulin concentration. This high level of nitrophenyl-binding serum immunoglobulins either suggests the existence of a particular regulatory mechanism in fish or reflects a generally low antibody diversity in these species.

Animals↗
PubMed1977

Motor-driven treadmill for studying locomotion in cats.

Increasing experimental concern with locomotion and its neural control prompted the construction of a motor-driven treadmill for cats. The apparatus was designed for kinematic analysis of gait from 16 mm movie film, but it will also permit a variety of other records to be taken. A box, or base, houses two large drums and the belt drive. Space is provided on top of the base for a closed locomotion compartment that is transparent on the filming side. There is also sufficient space on top of the base for support apparatus, operator controls, and animal exits. Cats may be trained to work for food reward alone, as delivered from the front by the operator. Alternatively, they can be trained to stay near the front of the treadmill belt in order to avoid an aversive jet of air or electric shock, either of which can be delivered at the rear of the test chamber. The operator can maintain forward belt velocity at fixed levels between 0.5 and 6 m/sec, or he can vary velocity continuously. Displays of a tachometer and a special timing device are large enough to be clearly visible on the film. These various features in combination provide a controlled and varsatile stepping environment, in which the cat can move without physical restraints.

Animals↗
PubMed1976

Kinematics of locomotion by cats with a single hindlimb deafferented.

1. Cinematographic measurements were made of stepping by cats on a motor-driven treadmill, both normally and 2-3 wk after deafferentation of the LH (left hind) limb. 2. After surgery, rhythmic cycling of the LH limb was blurred whether the leg was dragged, as by some cats, or if it was lifted from the surface, as by others. 3. Interlimb coordination was also blurred with respect to normal, although distinct rhythms were still seen. The RH (right hind) limb descended prematurely and, in the walk, had a prolonged stance phase. The interval between touchdowns of hind- and forelimb on the left side no longer equaled that interval on the right side. 4. As is true for a normal cat, if the LH-deafferented animal stumbled, relatively normal single and interlimb cyclings were regained after several strides. 5. By kinematic analysis, force deficits were found in the deafferented LH limb both during the stance, when extensors should be most active, and the swing, when the limb failed to attain a normal position above the surface of the belt. Weight bearing by the LF (left fore) limb was altered in some animals. 6. At high speed, mean LH stance duration failed to decrease in the normal fashion. Inter-limb timings were reset to greater extent than in low-speed walking, as if the LH limb was being used only minimally. 7. It was concluded that both rhythm and force were impaired in the deafferented limb and also in the three intact limbs, whose weight bearing had to compensate for LH weakness. The changed mechanical demands after surgery were probably met by interactions between the remaining afferent input and central pattern generators so as to secure fairly effective and expedient locomotion.

Afferent Pathways↗
PubMed1975

Neural implications of different profiles between treadmill and overground locomotion timings in cats.

A cinematographic comparison of treadmill and overground performances by the cat revealed considerable flexibility in the neural control program for locomotion. For the single limb's step cycle, swing duration (time foot is off the surface) was approximately equal in both situations, as has been found previously. Subcomponents of the swing (flexion duration and timings between joints during the transition from flexion to extension) differed, however. Interlimb timings also responded to situation. The interval between touchdown of one hindlimb and the ipsilateral forelimb was reduced for treadmill stepping. An ipsilateral coupling interval also differed that had been previously reported to involve propriospinal activity, the time for onset of extension during the swing phase of the hindlimb to the onset of flexion at the beginning of the swing phase in the forelimb. Segmental afferent input, visual and other suprasegmental inputs, and motivational variables probably all contribute to the separation of treadmill and overground timing profiles.

Animals↗