Biomedical subjects

R L Marsh

Publications and source records attributed to R L Marsh.

At least 19 recordsLinked to original sources

PubMed2001

False recognition occurs more frequently during source identification than during old-new recognition.

A number of recent reports have investigated false memories using variants of the Deese-Roediger-McDermott (DRM) paradigm. Because these false memories have been difficult to eliminate, this study investigated whether false recognition could be reduced by incorporating source-monitoring criteria into decision processes. Making claims about the manner in which items were learned should require more careful scrutiny of memories, and therefore false recognition should be minimized with source instructions as compared with old-new recognition instructions. In 3 experiments that varied the combination of sources, false recognition was increased rather than reduced by applying source-monitoring processes. The theoretical implications of these counterintuitive results are discussed in terms of the old-new detection component of source judgments.

Adult↗

PubMed2001

Output monitoring tests reveal false memories of memories that never existed.

Three experiments were conducted to assess participants' beliefs about potential false memories that might have occurred during free recall tests. An input-output monitoring test was administered that required participants to discriminate between items that were studied and recalled, studied and not recalled, or were entirely new. Critical lures from Roediger and McDermott's (1995) paradigm were inserted into this test. The results demonstrated that participants believed erroneously recalled items were both studied and recalled. The intriguing finding was that unrecalled items were believed to have been studied approximately 80% of the time, and half of those were also believed to have been recalled. This result represents a dual false memory effect in which items were believed to have been studied and also to have been recalled. The ramifications of this new procedure are discussed in terms of proposed experiments that might clarify the genesis of these false memories.

Analysis of Variance↗

PubMed2001

Effects of long-term exercise on the biomechanical properties of the Achilles tendon of guinea fowl.

The purpose of this study was to determine the effect of long-term exercise on tendon compliance and to ascertain whether tendons adapt differently to downhill running vs. running on a level surface. We carried out this investigation on the gastrocnemius tendon of helmeted guinea fowl (Numida meleagris) that were trained for 8-12 wk before commencing experimental procedures. We used an in situ technique to measure tendon stiffness. The animals were deeply anesthetized with isofluorane during all in situ procedures. Our results indicate that long-term exercise increased tendon stiffness. This finding held true after normalization for the cross-sectional area of the free tendon, likely reflecting a change in the material properties of the exercised tendons. Whether training consisted of level or downhill running did not appear to influence response of the tendon to exercise. We hypothesize that the increased stiffness observed in tendons after a long-term running program may be a response to repeated stress and may function as a mechanism to resist tendon damage due to mechanical fatigue.

Achilles Tendon↗

PubMed2000

The properties of retention intervals and their affect on retaining prospective memories.

Five experiments were conducted to explore how the character of the retention interval affected event-based prospective memory. According to the canons of retrospective memory, prospective performance should have been worse with increasing delays between intention formation and the time it was appropriate to complete an action. That result did not occur. Rather, prospective memory was better with increasing retention intervals in Experiments 1A, 1B, and 3. In manipulating the nature of the retention interval, the authors found that there were independent contributions of retention interval length and the number of intervening activities, with more activities leading to better prospective memory (Experiments 2 and 3). The identical retention intervals did not improve retrospective memory in Experiment 4. Theoretical explanations for these dissociations between prospective and retrospective memory are considered.

Adult↗

PubMed2000

Toward specifying the attentional demands of recognition memory.

Previous studies have concluded that recognition memory is immune to disruption from divided attention and therefore is a relatively automatic process (A. Baddeley, V. Lewis, M. Eldridge, & N. Thomson, 1984; F. I. M. Craik, R. Govoni, M. Naveh-Benjamin, & N. D. Anderson, 1996). Because costs have been found on the concurrent task used to divide attention, recognition may nevertheless require some attentional resources (M. Naveh-Benjamin, F. I. M. Craik, J. Guez, & H. Dori, 1998). The present authors used attention-demanding concurrent tasks to demonstrate significant costs on both the concurrent task and recognition memory performance. Decrements in recognition accuracy were found for classes of items that were studied deeply but not for more shallowly learned materials. The present findings suggest that recognition processes can require significant attentional resources when tested under the appropriate conditions. The results are discussed in terms of the requirements both at encoding and at test that are needed to observe dual-task decrements to recognition accuracy.

Adolescent↗

PubMed2000

Dissociation of two kinds of source attributions.

We examined the relationship between two different source attribution errors. One error found primarily in the cognitive psychology literature is the belief that one is an author of an idea when one is not. The other error, reported in the social psychology literature, occurs when people overestimate how long they have known an idea. Although somewhat different, both errors are a form of misappropriation of ideas to oneself. We investigated both attributions and found that when participants performed a more elaborate encoding task, erroneous claims of authorship were reduced but length-of-knowing judgments increased. The results are discussed in terms of the cognitive processing that is likely to give rise to each source attribution.

Adult↗

PubMed1999

The credibility of a source influences the rate of unconscious plagiarism.

Three experiments were conducted to investigate the relationship between the credibility of information and later unconscious plagiarism of that information. In each experiment, ideas concerning ways to reduce traffic accidents were presented from a more credible source (traffic planners) and a less credible source (college freshmen). After a distractor task, participants were asked to generate novel ways to reduce traffic accidents. In Experiments 1 and 2, unconscious plagiarism of ideas presented from the more credible source was greater than from the less credible source. In neither experiment was explicit memory for ideas from each source different in tests of source monitoring or free recall. However, the difference in unconscious plagiarism was eliminated in Experiment 3 by having participants generate the implications of ideas at study. The results are discussed in terms of the explicit factors that affect the incidence of unconscious plagiarism.

Adult↗

PubMed1999

Contractile properties of muscles used in sound production and locomotion in two species of gray tree frog.

The sound-producing muscles of frogs and toads are interesting because they have been selected to produce high-power outputs at high frequencies. The two North American species of gray tree frog, Hyla chrysoscelis and Hyla versicolor, are a diploid-tetraploid species pair. They are morphologically identical, but differ in the structure of their advertisement calls. H. chrysoscelis produces very loud pulsed calls by contracting its calling muscles at approximately 40 Hz at 20 degrees C, whereas, H. versicolor operates the homologous muscles at approximately 20 Hz at this temperature. This study examined the matching of the intrinsic contractile properties of the calling muscles to their frequency of use. I measured the isotonic and isometric contractile properties of two calling muscles, the laryngeal dilator, which presumably has a role in modulating call structure, and the external oblique, which is one of the muscles that provides the mechanical power for calling. I also examined the properties of the sartorius as a representative locomotor muscle. The calling muscles differ greatly in twitch kinetics between the two species. The calling muscles of H. chrysoscelis reach peak tension in a twitch after approximately 15 ms, compared with 25 ms for the same muscles in H. versicolor. The muscles also differ significantly in isotonic properties in the direction predicted from their calling frequencies. However, the maximum shortening velocities of the calling muscles of H. versicolor are only slightly lower than those of the comparable muscles of H. chrysoscelis. The calling muscles have similar maximum shortening velocities to the sartorius, but have much flatter force-velocity curves, which may be an adaptation to their role in cyclical power output. I conclude that twitch properties have been modified more by selection than have intrinsic shortening velocities. This difference corresponds to the differing roles of shortening velocity and twitch kinetics in determining power output at differing frequencies.

Animals↗

PubMed1999

Power output of sound-producing muscles in the tree frogs Hyla versicolor and Hyla chrysoscelis.

Sound-producing muscles provide the opportunity of studying the limits of power production at high contractile frequencies. We used the work loop technique to determine the power available from the external oblique muscles in two related species of North American gray tree frog, Hyla chrysoscelis and Hyla versicolor. These trunk muscles contract cyclically, powering high-intensity sound production in anuran amphibians. The external oblique muscles in H. chrysoscelis have an in vivo operating frequency of 40-55 Hz at 20-25 degrees C, whereas in H. versicolor these muscles contract with a frequency of 20-25 Hz at these temperatures. In vivo investigations have shown that these muscles use an asymmetrical sawtooth length trajectory (with a longer shortening phase compared with the lengthening phase) during natural cycles. To study the influence of this particular length trajectory on power output, we subjected the muscles to both sinusoidal and sawtooth length trajectories. In both species, the sawtooth trajectory yielded a significantly higher power output than the sinusoidal length pattern. The maximum power output during sawtooth cycles was similar in both species (54 W kg(-)(1) in H. chrysoscelis and 58 W kg(-)(1) in H. versicolor). These values are impressive, particularly at the operating frequencies and temperatures of the muscle. The sinusoidal length trajectory yielded only 60 % of the total power output compared with the sawtooth trajectory (34 W kg(-)(1) for H. chrysoscelis and 36 W kg(-)(1) for H. versicolor). The optimum cycle frequencies maximizing the power output using a sawtooth length pattern were approximately 44 Hz for H. chrysoscelis and 21 Hz for H. versicolor. These frequencies are close to those used by the two species during calling. Operating at higher frequencies, H. chrysoscelis maximized power at a strain amplitude of only 8 % compared with a value of 12 % in H. versicolor. These strains match those used in vivo during calling. The stimulus timing observed in vivo during calling was also similar to that yielding maximum power at optimal frequency in both species (6 ms and 8 ms before the start of shortening in H. chrysoscelis and H. versicolor, respectively). As expected, twitch duration in H. chrysoscelis is much shorter than that in H. versicolor (23 ms and 37 ms, respectively). There was a less remarkable difference between their maximum shortening velocities (V(max)) of 13.6 L(0 )s(-)(1) in H. chrysoscelis and 11.1 L(0 )s(-)(1) in H. versicolor, where L(0) is muscle length. The force-velocity curves are very flat, which increases power output. At the myofibrillar level, the flat force-velocity curves more than compensate for the lower peak isometric force found in these muscles. The data presented here emphasize the importance of incorporating in vivo variables in designing in vitro studies.

Animals↗

PubMed1999

How muscles deal with real-world loads: the influence of length trajectory on muscle performance.

The performance of skeletal muscles in vivo is determined by the feedback received when the muscle interacts with the external environment via various morphological structures. This interaction between the muscle and the 'real-world load' forces us to reconsider how muscles are adapted to suit their in vivo function. We must consider the co-evolution of the muscles and the morphological structures that 'create' the load in concert with the properties of the external environment. This complex set of interactions may limit muscle performance acutely and may also constrain the evolution of morphology and physiology. The performance of skeletal muscle is determined by the length trajectory during movement and the pattern of stimulation. Important features of the length trajectory include its amplitude, frequency, starting length and shape (velocity profile). Many of these parameters interact. For example, changing the velocity profile during shortening may change the optimum values of the other parameters. The length trajectory that maximizes performance depends on the task to be performed. During cyclical work, muscles benefit from using asymmetric cycles with longer shortening than lengthening phases. Modifying this 'sawtooth' cycle by increasing the velocity during shortening may further increase power by augmenting force output and speeding deactivation. In contrast, when accelerating an inertial load, as in jumping, the predicted 'optimal' velocity profile has two peak values, one early and one late in shortening. During level running at constant speed, muscles perform tasks other than producing work and power. Producing force to support the body weight is performed with nearly isometric contractions in some of the limb muscles of vertebrates. Muscles also play a key role in producing stability during running, and the intrinsic properties of the musculoskeletal system may be particularly important in stabilizing rapid running. Recently, muscles in running invertebrates and vertebrates have been described that routinely absorb large amounts of work during running. These muscles are hypothesized to play a key role in stability.

Animals↗

PubMed1999

The inadvertent use of prior knowledge in a generative cognitive task.

In four experiments with 332 participants, participants were asked to generate novel nonwords for English categories. When participants were shown examples embedded with regular orthographic structures, participants' nonwords tended to conform orthographically to the examples, despite instructions to avoid using features of the examples. The effect was found with immediate testing (Experiments 1) and delayed testing (Experiment 2). The effect was also found with arbitrary features (Experiments 1-4), as well as with naturally occurring orthographic regularities (Experiment 4). Participants had difficulty avoiding the use of this prior knowledge, despite being able to list the features they were asked to avoid (Experiment 3). The results are discussed in terms of the inadvertent use of prior knowledge in generative cognitive tasks.

Adult↗

PubMed1999

The activation of unrelated and canceled intentions.

The intention superiority effect is the finding that intentions to perform an activity are stored in a heightened state of activation. The effect has also been generalized to the finding that once an intention is fulfilled, it is inhibited relative to more neutral material about which no intentionality has been formed. In two experiments, we tested some ecological and naturally occurring situations taken from the literature on prospective memory and demonstrated that they have consistent consequences for the activation level of an intention. In Experiment 1, a constellation of unrelated activities displayed heightened activation prior to completion and displayed inhibition after completion. In Experiment 2, canceling the intention resulted in inhibition just as completing the intention does in this paradigm. The results are discussed in terms of their practical and theoretical importance to theories of prospective memory.

Humans↗

PubMed1999

Conceptual priming in a generative problem-solving task.

Three experiments explored how participants solved a very open-ended generative problem-solving task. Previous research has shown that when participants are shown examples, novel creations will tend to conform to features shared across those examples (Smith, Ward, & Schumacher, 1993). We made the shared features of the examples conceptually related to one another. We found that when the features were related to the concept of hostility, participants' creations contained hostile features that were not part of any of the examples. These results suggest that participants will design novel entities to be consistent with emergent properties of examples shown to them. We also found that a mild hostility prime from unscrambling sentences had a similar conceptual effect. Together, the two effects suggest that conceptual priming of generative cognitive tasks will influence the cognitive aspects of the creative process.

Analysis of Variance↗

PubMed1998

Topographic differences in CNV amplitude reflect different preparatory processes.

Topographic differences in Contingent Negative Variation (CNV) were recorded while people were preparing for cognitive versus motor tasks in an S1-S2 paradigm. CNV had a frontal distribution when people prepared to encode words into long-term memory, whereas CNV was more centrally distributed when the tasks were predominantly motoric. These topographic differences appeared to be related to the type of task rather than the amount of information extracted from the S2, because a direct manipulation of the level of S2 processing had little effect on CNV amplitude. The topographic differences in CNV suggest that preparation for motor activity is a different psychological process from preparation for stimulus processing and that these two processes are subserved by different neural structures. This experiment also demonstrated that a recognition memory paradigm can be useful in the investigation of the psychological correlates of CNV.

Adolescent↗

PubMed1998

Event-based prospective memory and executive control of working memory.

In 5 experiments, the character of concurrent cognitive processing was manipulated during an event-based prospective memory task. High- and low-load conditions that differed only in the difficulty of the concurrent task were tested in each experiment. In Experiments 1 and 2, attention-demanding tasks from the literature on executive control produced decrements in prospective memory. In Experiment 3, attention was divided by different loads of articulatory suppression that did not ultimately lead to decrements in prospective memory. A high-load manipulation of a visuospatial task requiring performance monitoring resulted in worse prospective memory in Experiment 4, whereas in Experiment 5 a visuospatial task with little monitoring did not. Results are discussed in terms of executive functions, such as planning and monitoring, that appear to be critical to successful event-based prospective memory.

Adult↗

PubMed1998

Optimal shortening velocity (V/Vmax) of skeletal muscle during cyclical contractions: length-force effects and velocity-dependent activation and deactivation.

The force-velocity relationship has frequently been used to predict the shortening velocity that muscles should use to generate maximal net power output. Such predictions ignore other well-characterized intrinsic properties of the muscle, such as the length-force relationship and the kinetics of activation and deactivation (relaxation). We examined the effects of relative shortening velocity on the maximum net power output (over the entire cycle) of mouse soleus muscle, using sawtooth strain trajectories over a range of cycle frequencies. The strain trajectory was varied such that the proportion of the cycle spent shortening was 25, 50 or 75 % of the total cycle duration. A peak isotonic power output of 167 W kg-1 was obtained at a relative shortening velocity (V/Vmax) of 0.22. Over the range of cyclical contractions studied, the optimal V/Vmax for power production ranged almost fourfold from 0.075 to 0.30, with a maximum net power output of 94 W kg-1. The net power output increased as the proportion of the cycle spent shortening increased. Under conditions where the strain amplitude was high (i.e. low cycle frequencies and strain trajectories where the proportion of time spent shortening was greater than that spent lengthening), the effects of the length-force relationship reduced the optimal V/Vmax below that predicted from the force-velocity curve. At high cycle frequencies and also for strain trajectories with brief shortening periods, higher rates of activation and deactivation with increased strain rate shifted the optimal V/Vmax above that predicted from the force-velocity relationship. Thus, the force-velocity relationship alone does not accurately predict the optimal V/Vmax for maximum power production in muscles that operate over a wide range of conditions (e.g. red muscle of fish). The change in the rates of activation and deactivation with increasing velocity of stretch and shortening, respectively, made it difficult to model force accurately on the basis of the force-velocity and length-force relationships and isometric activation and deactivation kinetics. The discrepancies between the modelled and measured forces were largest at high cycle frequencies.

Animals↗

PubMed1998

Activation patterns and length changes in hindlimb muscles of the bullfrog Rana catesbeiana during jumping.

We measured the electromyographic (EMG) activity of seven hindlimb muscles during jumping in the bullfrog Rana catesbeiana. The semimembranosus, gracilis major, gluteus magnus, adductor magnus, cruralis and plantaris longus were consistently active approximately 20-40 ms before any perceptible movement, as indicated by simultaneous video recordings. Activity ended before full extension of the hindlimb and take-off. Activity in the semitendinosus was variable among the jumps recorded. Simultaneous measurements of EMG activity and length changes (via sonomicrometry) in the semimembranosus (SM) and gluteus magnus (GM) muscles indicated that the performance characteristics of these two muscles differed. The SM muscle (a hip extensor) shortens and is activated in a manner consistent with its producing power during a significant fraction of the take-off phase. It shortened by a mean of 26.2% of the resting length during the propulsive phase of the two longest jumps for each frog. The delay between the onset of EMG activity and the beginning of shortening averaged 24 ms, which was brief compared with that found for the GM. The total strain and mean shortening velocity of the SM increased with jumping distance. Contrary to our initial expectations, the GM muscle does not shorten as one would expect of a muscle involved in powering the jump throughout take-off. This muscle has an extensor action at the knee, but also has a flexor action at the hip. A long delay existed between the onset of EMG activity and the beginning of shortening (46-116 ms among the individuals tested). Shortening during take-off by the GM (a mean of 16.7% for all jumps) was much less than by the SM, and in many jumps most of this shortening occurred late in the take-off period. Although the GM cannot contribute directly to power output early in take-off, it may contribute to powering the jump indirectly by transferring energy from the hip extensors to the knee joint. We conclude that muscles previously assumed (on the basis of anatomical criteria) by ourselves and others to be powering the jump may show considerable diversity of function. We hypothesize that elastic energy storage is used to help power jumping, and therefore suggest that muscles in series with major tendinous elements should be targeted for further study.

Animals↗

PubMed1998

An investigation of everyday prospective memory.

Prospective memory, remembering to carry out one's planned activities, was investigated using a naturalistic paradigm. Three experiments, with a total of 405 participants, were conducted. The goal was to demonstrate that the cognitive processing underlying successful everyday prospective remembering involves components other than mere "memory." Those components are probably best represented as individual differences in various cognitive capacities. More specifically, metamemory, attentional capacities, and planning processes that reprioritize intentions according to the demands of everyday life may determine how people actually accomplish the plans they establish for themselves. The results of these experiments suggest that researchers interested in the topic will have to contend with a multidimensional set of factors before any comprehensive understanding of prospective remembering can be realized.

Adult↗