Rhythmic tapping difficulties in adults who stutter: a deficit in Central Clock and/or Motor Implementation?

The study aims to better understand the origin of increased tapping variability and inaccuracy in people who stutter during paced and un-paced tapping. The overall question is to what extent these timing difficulties are related to a central clock deficit, a deficit in motor execution, or both.Finger tapping behavior of 16 adults who stutter (PWS) with different levels of musical training was compared with performance of 16 matching controls (PNS) in three finger tapping synchronization tasks ― a simple 1:1 isochronous pattern, a complex non-isochronous pattern, and a 4 tap:1 beat isochronous pattern ―, a continuation task (without external stimulation), and a reaction task involving aperiodic and unpredictable patterns. The results show that PWS exhibited larger negative asynchrony (expressed as phase angles), and increased synchronization variability (expressed as phase locking values) in paced tapping tasks, and that these differences from the PNS group were modulated by rhythmic complexity and musical training. The tapping asynchrony with a simple isochronous pattern correlated significantly with the average inter-tap duration, and with tap reaction times during the reaction task. The synchronization variability with a simple isochronous pattern correlated significantly with both the central clock and motor implementation variances as extracted during un-paced tapping, according to the Wing and Kristofferson’s model of timing.The results support the idea that increased tapping variability of PWS is associated with both a central clock and a motor execution deficit. The greater Negative Mean Asynchrony of PWS does not appear to be attributable to a deficit in time estimation but rather to a motor deficit. Several models and theories related to deficits in sensorimotor integration were considered to explain the interactions with beat strength, pattern complexity, and musical training.

Rapid Dual-Task Decrements After a Brief Period of Manual Tracking in Simulated Weightlessness by Water Submersion

Objective Investigating dual-task (DT) performance during simulated weightlessness by water submersion, using a manual tracking and a choice reaction task. In contrast to previous work, we focus on performance changes over time. Background Previous research showed motor tracking and choice reaction impairments under DT and single-task (ST) conditions in shallow water submersion. Recent research analyzed performance as average across task time, neglecting potential time-related changes or fluctuations of task-performance. Method An unstable tracking and a choice reaction task was performed for one minute under ST and DT conditions in 5 m water submersion and on dry land in 43 participants. Tracking and choice reaction time performance for both tasks were analyzed in blocks of 10 seconds. Results Tracking performance deteriorated underwater compared to dry land conditions during the second half while performing one minute in DT conditions. Choice reaction time increased underwater as well, but independent of task time and type. Conclusion Tracking error increased over time when performing unstable tracking and choice reaction together. Potentially, physiological and psychological alterations under shallow submersion further strain the human system during DT operations, exceeding available recourse capacities such that DT performance deteriorated over time. Application Humans operating in simulated weightlessness underwater should be aware of substantial performance declines that can occur within a short amount of time during DT situations that include continuous tracking.

Motor Chunking in Internally Guided Sequencing

Motor skill learning involves the acquisition of sequential motor movements with practice. Studies have shown that we learn to execute these sequences efficiently by chaining several elementary actions in sub-sequences called motor chunks. Several experimental paradigms, such as serial reaction task, discrete sequence production, and m × n task, have investigated motor chunking in externally specified sequencing where the environment or task paradigm provides the sequence of stimuli, i.e., the responses are stimulus driven. In this study, we examine motor chunking in a class of more realistic motor tasks that involve internally guided sequencing where the sequence of motor actions is self-generated or internally specified. We employ a grid-navigation task as an exemplar of internally guided sequencing to investigate practice-driven performance improvements due to motor chunking. The participants performed the grid-sailing task (GST) (Fermin et al., 2010), which required navigating (by executing sequential keypresses) a 10 × 10 grid from start to goal position while using a particular type of key mapping between the three cursor movement directions and the three keyboard buttons. We provide empirical evidence for motor chunking in grid-navigation tasks by showing the emergence of subject-specific, unique temporal patterns in response times. Our findings show spontaneous chunking without pre-specified or externally guided structures while replicating the earlier results with a less constrained, internally guided sequencing paradigm.

Menos masculino, demasiado infantil

Age is an under-analyzed variable in linguistic research concerning gender and sexuality. We consider these three constructs by examining diminutives as an index of gay sexuality in Madrid Spanish across two tasks. Although phonetic cues have received great attention, morphological features (e.g. diminutives) may also index gayness (Mendes 2014). Moreover, despite frequent usage across Spanish-speaking varieties, diminutives are primarily restricted to women and children in north-central Spain (Haensch 2002). In a diminutive reaction task, 53 Madrid residents indicated whether men, women, adults, or children were likely to have uttered diminutivized sentences. Mixed-effects models indicated that the number of diminutives and sentence theme significantly affected perception, and participants’ evaluations in a free response task corroborated that men using diminutives were considered effeminate, gay, and childish. Thus, even with sociophonetic cues removed, morphological phenomena create a gay percept. This study demonstrates how age ideologies inform indexicalization processes related to gender and sexuality.

Motion-Onset Visual Potentials Evoked in a Sport-Specific Visuomotor Reaction Task

Although neural visual processes play a crucial role in sport, experiments have been restricted to laboratory conditions lacking ecological validity. Therefore, this study examined the feasibility of measuring visual evoked potentials in a sport-specific visuomotor task. A total of 18 international elite young table tennis athletes (mean age 12.5 years) performed a computer-based and a sport-specific visuomotor reaction task in response to radial motion-onset stimuli on a computer screen and table tennis balls played by a ball machine, respectively. A 64-channel electroencephalography system identified the N2 and N2-r motion-onset visual evoked potentials in the motion-sensitive midtemporal visual area. Visual evoked potential amplitudes were highly correlated between conditions (N2 r = .72, N2-r r = .74) although significantly lower in the sport-specific task than in the lab-based task (N2 p < .001, N2-r p < .001). The results suggest that sport-specific visual stimulation is feasible to evoke visual potentials. This emphasizes the investigation of visual processes under more ecologically valid conditions in sport and exercise science.

Lack of Automatic Vocal Response Learning While Reading Aloud

Research on implicit sequence learning with the Serial Reaction Task (SRT) has demonstrated that people automatically acquire knowledge about fixed repeating sequences of responses and can transfer response sequence knowledge to novel stimuli. Such demonstrations are, however, mostly limited to setups with visual stimuli and manual responses. Here we systematically follow up on scarce attempts to demonstrate implicit sequence learning in word reading. While the literature on implicit sequence learning can be taken to suggest that sequence knowledge is acquired and affecting performance in word reading, we show that neither is the case in a series of four experiments. Sequence knowledge was acquired and affecting performance in color naming but not in word reading. On the one hand, we observed slowing of voice-onset times in off-sequence as compared to regularly sequenced trials when people named the color of a centrally presented disk. Yet, hardly any effect was observed when the very same sequence of words was verbalized in word reading instead. Transfer of sequence knowledge to and from color naming was not observed, either. This contrasts with sequence learning studies with manual responses, which have been taken to suggest that a fixed and repeating sequence of responses is sufficient for learning to occur even in fast choice reaction tasks and to transfer across stimuli as long as the sequence of responses remains intact. Rather, in line with dimensional action accounts of task performance, the results underline the role of translation between processing streams for implicit sequence learning.