NEW ENGLAND SEQUENCING AND TIMING (NEST)
Sixteenth Annual Meeting
Time: Saturday, March 11, 2006, 8:30 a.m. – 5:00 p.m.
Place: Haskins Laboratories, 300 George Street, New Haven, CT
Organizer: Bruno H. Repp (e-mail: repp@haskins.yale.edu)
Assistant: Aaron Schultz
PROGRAM
8:30 – 9:00 Continental breakfast 9:00 – 9:25 9:25 – 9:50 Two experiments on the discrimination of time intervals presented in sequences marked by brief auditory signals are presented. Participants had to indicate whether the last interval in a series of 3 intervals marked by 4 auditory signals was shorter or longer than the previous intervals. Three base durations were under investigation: 75, 150 and 225 ms. In Experiment 1, sounds were presented through headphones, from a single speaker in front of the participants or by four equally spaced speakers. In all three presentation modes, the highest differential threshold was obtained in the lower base duration condition (75 ms), thus indicating an impairment of temporal processing when sounds are presented too rapidly. The results also indicate the presence, in each presentation mode, of a “time-shrinking effect” (i.e., with the last interval being perceived as briefer than the preceding ones) at 75 ms, but not at 225 ms. Lastly, using different sound sources to mark time did not significantly impair discrimination. In Experiment 2, three signals were presented from the same source, and the last signal was presented at one of two locations, either close or far. The perceived duration was not influenced by the location of the fourth signal when the participant knew before each trial where the sounds would be delivered. However, when the participant was uncertain as to its location, more space between markers resulted in longer perceived duration, a finding that applies only at 150 and 225 ms. Moreover, the perceived duration was affected by the direction of the sequences (left-right vs. right-left). Overall, the results are mainly discussed in relation to the kappa effect and the time-shrinking illusion. 9:50 – 10:15 Behavioral and event-related potential (ERP) studies of selective attention to distinct levels of hierarchical auditory stimuli suggest there are similarities between visual and auditory local and global processing. Specifically, by combining short (40 ms) frequency modulated tones in series to create global auditory patterns, we independently varied whether pitch increased or decreased over short time spans (local) and longer time spans (global). Accuracy and reaction time measures revealed better performance for global judgments and asymmetric interference that were modulated by amount of pitch change. ERPs recorded while participants listened to identical sounds and indicated the direction of pitch change at the local or global levels provided evidence for differential processing similar to that found in ERP studies employing hierarchical visual stimuli. ERP measures failed to provide evidence for lateralization of local and global auditory perception, but differences in distributions suggest preferential processing in more ventral and dorsal areas respectively. We will also present data from new studies comparing the effects of selective attention to specific times and to time scales on auditory processing. 10:15 – 10:45 Coffee break 10:45 – 11:10 A basic finding in the time perception literature is the interference effect, in which timing performance is disrupted by a concurrent distractor task. Previous research has shown that practice on a distractor task reduces interference on the timing task. According to an attentional model, this result occurs because practice reduces the resource requirements of the distractor task, thereby making more resources available for timing. The present research was designed to determine whether practice on a timing task would also serve to minimize distractor task interference. In Experiment 1, subjects reproduced a series of 6—14 sec intervals in a series of practice trials. Some subjects received feedback regarding the accuracy of each response and others received no feedback. Subsequent testing under dual-task (timing + digit memory) conditions showed that feedback training reduced interference. In Experiment 2, the practice trials included both single-task and dual-task conditions. Later tests showed that feedback training eliminated the interference effect. The results highlight the role of attentional resources and compensatory decision processes in time judgment skill training. 11:10 – 11:35 Eyeblink conditioning has long been a model for understanding behavioral and physiological principles of learning, memory, and performance. The present research extends previous research on the role of temporal uncertainty in eyeblink conditioning to situations involving multiple cues.Rabbits were trained to make eyeblink conditioned responses (CRs) to a compound conditioned stimulus (CS) consisting of a tone (T) and light (L) presented simultaneously and reinforced with an unconditioned stimulus (US). This training involved a mixture of two CS-US intervals. On some trials, the compound CS was reinforced 300 ms after CS-onset; on other trials, the CS-US interval was 700 ms. Randomly mixing trials with these CS-US intervals produced bimodal CR waveforms with amplitude peaks located at the two temporal loci of the US. Test trials revealed that the bimodality of CR waveforms was preserved when the component CSs, T and L, were presented separately. However, the component waveforms were shifted in time toward longer peak latencies, while preserving the inter-peak intervals of the compound waveforms. These `decomposition shifts’ in latency were greater for the light CS than the tone CS, the tone being the more salient cue. Furthermore, waveform amplitudes were greater to the tone than the light, also reflecting a difference in salience. The compound waveform could be reconstituted by summing the component waveforms, as would be expected by mathematical models of classical conditioning that assume that the `associative value’ of a compound CS is the sum of the `associative values’ of its components. 11:35 – 12:00 Effects of MK-801, an N-methyl-D-aspartate antagonist, on short-interval timing in rats were examined using the peak-interval (PI) procedure. Following PI training, Fisher 344 rats were given daily injections of 0.025 mg/kg, 0.05 mg/kg, 0.2 mg/kg MK-801, or saline. The main results were (a) 0.2 mg/kg MK-801 produced an immediate over-estimation of the criterion time, (b) MK-801 increased peak-rate of responding at all doses, and (c) 0.2 mg/kg MK-801 produced a non-scalar increase in variability. Results of this study and related work will be discussed within the framework of scalar expectancy theory (Gibbon, 1977). 12:00 – 1:00 Lunch (provided) 1:00 – 1:15 A simple adaptive staircase procedure was used to determine the “synchronization threshold”—the fastest rate of an isochronous tone sequence at which participants still can achieve and maintain synchrony with selected tones—for each of 8 tapping tasks. The tasks consisted of tapping with every nth tone (n = 2 to 9) in the sequence. This required repeated implicit counting at rates that often exceeded the maximal possible rate of verbal counting. Both musicians and non-musicians were tested. Not surprisingly, the musicians had lower synchronization thresholds than the non-musicians. For both groups, however, tapping with every 5th or 7th tone was difficult, whereas tapping with every 2nd, 4th, or 8th tone was easy; tapping with every 3rd, 6th, or 9th tone was of intermediate difficulty. These results suggest that non-prime event counts (4, 6, 8, 9) are automatically subdivided into smaller groups (with duple subdivision being easier than triple), whereas prime counts (5, 7) are either subdivided into unequal groups or not at all. This automatic grouping process generates the metrical hierarchies that are commonly found in Western music. It seems to require neither musical experience nor a sequence rate so fast that verbal counting is impossible. 1:15 – 1:40 Synchronization in many everyday activities involves the co-influence of two rhythmic entities; for example, a conductor and his/her orchestra almost always influence each other. In most tapping tasks, however, the participant is unidirectionally influenced by an external metronome. We built an analog electronic oscillator with which the participant coordinates and which can be influenced in real time by the participant’s behavior. In such a paradigm, the rhythmic components are bidirectionally coupled, allowing for the study of co-influence. The oscillator and how it is coupled to the participant is under experimental control, and the evolving state of the oscillator can be collected and analyzed in detail. In this first experiment, a synchronization/continuation tapping task, each cycle of the oscillator triggered an acoustic pacing tone, and each tap produced by the participant could deliver a discrete perturbation to the oscillator’s state. Depending on the magnitude, direction, and timing of each perturbation, the latter determined solely by the participant, the oscillator could be sped up or slowed down, and so each pacing sequence was co-determined by the oscillator and the participant. Systematic variations in the resultant tapping frequency, tap-to-beep asynchrony, and dynamical measures on the state of the oscillator, were found as a function of the magnitude and direction of perturbation. Production of continuation taps were also influenced by the nature of the coupling present during the synchronization phase. 1:40 – 2:05 During the past five years, Spencer along with Ivry and Zelaznik has proposed the hypothesis that some tasks require a temporal representation to guide temporal behavior, and other tasks do not. Spencer et al. (2003, Science) call the former tasks event timing, and the latter tasks emergent timing. A tapping task is considered the archetypal event timing task, and continuous timing in circle drawing has been the stand-in for emergent timing. Over a wide range of behavioral manipulations a dissociation was observed between tasks that are hypothesized to require event timing compared to those that require emergent timing. Spencer et al. also observed that individuals with cerebellar lesions were impaired on event-timing tasks, but not on emergent timing ones. In the present study we build on this finding by asking whether an event timing task differentially affects posture compared to an emergent timing task. The logic we used was straightforward. Cerebellar processes are necessary for good balance control, and of course also necessary for timing in tapping. However, circle drawing, an emergent timing task, does not tap into cerebellar resources to the same extent as tapping. Twelve young adults performed a quiet standing task and also performed each of two timing tasks, while standing. We found that tapping while standing caused a loss of complexity in the postural center of the pressure time series, whereas circle drawing did not. We take these results as preliminary support for structural interference between tapping and postural control. 2:05 – 2:30
The distinction between event timing and emergent timing has been applied to tasks that differ in their temporal profile (e.g., tapping vs. repetitive circle drawing). A dynamical perspective seeks to account for the differences by evaluating and comparing the properties of the synergies assembled for each task. The soft assembled arm-hand system for a given timing task may be constrained such that only specific settings of damping and stiffness are possible. One challenge is how to identify the specific set of nonlinear components on the basis of empirical data. One methodological tool, the W-function approach, is so designed as to dissect rhythms into their constituent dynamical functions. The W-approach begins with position and velocity measurements of a rhythmic movement. The plot of the phase plane is matched to the most general form of a self-sustained oscillator,
2:30 – 3:00 Coffee break 3:00 – 3:25
Movement during standing, sway, is primarily detected by perception of correlated optic flow on the retina and proprioception of changes in joint angles. Aging can result in loss of acuity in vision as well as proprioception. Acuity in these two senses may not be lost at an equal rate with respect to their contributions to stance. Thus, aging may require postural control to readapt to the changing accuracy of information from these senses. We present results of an experiment in which the information from proprioception and vision give conflicting perceptions. Younger and older participants stand on a stable platform in a small room whose walls are moved either laterally or anterior--posterior to the participant's gaze. Participant's head, trunk, arms, hands, and knees are motion--tracked. Head, sacrum, and right hand data were fit using multilevel windowed second order linear differential equations. Head frequency is found to be positively related to the frequency of the moving room, male gender, and height, but negatively related to age. On the other hand, sacrum frequency is not related to the frequency of the room or height but is positively related to male gender and age. Negative linear coupling was found between head and room velocity which was found to be attenuated by age and height. Negative coupling effects of room frequency and age category as well as a positive effect of male gender were found. Overall these results are inconsistent with a monolithic view of postural control, but are consistent with a coupled multiple systems view.
3:25 – 3:50
Previous work in 2-D workspaces has applied the posture-based model of movement planning (Rosenbaum, et al., 2001) to tasks including reaching to targets, grasping objects, handwriting, and circumventing obstacles. The model uses two computed postures, a goal posture and a "bounce" posture, to generate the movement trajectory, by superimposing a back-and-forth movement to the bounce posture on the direct movement from a start posture to the goal posture. Because the bounce movement is reversible, superimposing it on the direct movement modifies the overall trajectory to avoid the obstacle but does not otherwise affect the posture adopted at the goal. We now report on modeling movements of a tool around an obstacle in 3-D space, using a torso-limb system with 8 degrees of freedom. Participants' movements were recorded as they touched a sequence of targets with a hand-held tool, with or without intervening obstacles. The model computes realistic tool and arm trajectories to touch the same sequence of targets. The presentation will demonstrate the model in operation, address the challenges of modeling in 3-D workspaces, and discuss methods for evaluating such models.
3:50 – 4:15
Individuals with developmental dyslexia demonstrate reading impairments (e.g., in decoding words from spelling to sound; Bradley and Bryant, 1983). One deficit that is not often considered is manual motor performance. Wolff, Michael, Ovrut, and Drake (1990) observed motor deficits in dyslexic readers when the task required the individual to tap two fingers in an alternating fashion. Non-dyslexic individuals with poor phonological recoding ability also show motor deficits in the timing and variability of finger taps in a sequential coordination task using four fingers (Carello, LeVasseur, & Schmidt, 2002). The present study measured non-impaired readers’ performance on a series of reading tasks (e.g., rapid object/digit naming, word attack, and phonological recoding skill). Each participant then took part in several sequencing tasks in which task complexity was manipulated (e.g., number of fingers and hands used). Performance was measured in three ways and can be thought of as a motor timing hierarchy: (1) timing and variability within one sequence, (2) timing and variability of intervals between successive fingers within a sequence, and (3) the time between one sequence and the next. Spoken language is also comprised of a motor hierarchy beginning with the coarticulation of overlapping phonemic segments and terminating with the articulation of a word. The results of the study suggest that each measure of reading skill correlated with a different layer of the motor sequencing hierarchy.
4:15 – 4:40 The author of “the Magna Carta of the information age” identified a general timing requirement for juggling: The ratio of an object cycle time (T object) to a hand cycle time (T hand) is equal to the ratio of the number of objects (O) to the number of hands (H), T object/T hand = O/H. In acknowledgment of the 5th anniversary of Shannon’s passing, I will review the major results of experiments conducted within the framework of the juggling equation and discuss other examples of potentially universal timing relations that live abstractly in task space (e.g., Fitts’ law, HKB elementary coordination dynamics).
5:00 – 6:20 Drinks at Bar (254 Crown Street)
6:30 – 8:30 Dinner at Bentara (76 Orange Street) |
, where 
and 
represent the necessary components of any oscillating system and comprise the ideal mass-spring system. The 
function includes all the derivations from the ideal in terms of friction and non-linear elastic terms. The 
function provides a graphical means of identifying local linear damping behavior (e.g., Duffing type oscillators) and non-linear friction behaviors (e.g., Van der Pol and Rayleigh type oscillators) in timing data. The equivalent 
function provides statistical means of quantifying the contributions of the constituent dynamical functions. The qualitative graphical analysis and the quantitative statistical procedures are applied to timing data from two timing tasks. In a paced tapping task (so-called event timing), seated participants oscillate a 60-cm wooden dowel about the wrist to tap the dowel against a wooden block in time to an auditory metronome. In a paced circle drawing task (so called emergent timing), seated participants rotate the dowel about the wrist to trace a circle target on the floor using a laser beam emitted from the end of the dowel.