A Framework for Online Experimenter-Moderated Looking-Time Studies Assessing Infants’ Linguistic Knowledge

Online data collection methods pose unique challenges and opportunities for infant researchers. Looking-time measures require relative timing precision to link eye-gaze behavior to stimulus presentation, particularly for tasks that require visual stimuli to be temporally linked to auditory stimuli, which may be disrupted when studies are delivered online. Concurrently, by widening potential geographic recruitment areas, online data collection may also provide an opportunity to diversify participant samples that are not possible given in-lab data collection. To date, there is limited information about these potential challenges and opportunities. In Study 1, twenty-one 23- to 26-month-olds participated in an experimenter-moderated looking-time paradigm that was administered via the video conferencing platform Zoom, attempting to recreate in-lab data collection using a looking-while-listening paradigm. Data collected virtually approximated results from in-lab samples of familiar word recognition, after minimal corrections to account for timing variability. We also found that the procedures were robust to a wide range of internet speeds, increasing the range of potential participants. However, despite the use of an online task, the participants in Study 1 were demographically unrepresentative, as typically observed with in-person studies in our geographic area. The potentially wider reach of online data collection methods presents an opportunity to recruit larger, more representative samples than those traditionally found in lab-based infant research, which is crucial for conducting generalizable human-subjects research. In Study 2, microtargeted Facebook advertisements for online studies were directed at two geographic locations that are comparable in population size but vary widely in demographic and socioeconomic factors. We successfully elicited sign-up responses from caregivers in neighborhoods that are far more diverse than the local University community in which we conduct our in-person studies. The current studies provide a framework for infancy researchers to conduct remote eye-gaze studies by identifying best practices for recruitment, design, and analysis. Moderated online data collection can provide considerable benefits to the diversification of infant research, with minimal impact on the timing precision and usability of the resultant data.

An information theoretic method to resolve millisecond-scale spike timing precision in a comprehensive motor program

Sensory inputs in nervous systems are often encoded at the millisecond scale in a temporally precise code. There is now a growing appreciation for the prevalence of precise timing encoding in motor systems. Animals from moths to birds control motor outputs using precise spike timing, but we largely do not know at what scale timing matters in these circuits due to the difficulty of recording a complete set of spike-resolved motor signals and relatively few methods for assessing spike timing precision. We introduce a method to estimate spike timing precision in motor circuits using continuous MI estimation at increasing levels of added uniform noise. This method can assess spike timing precision at fine scales for encoding rich motor output variation. We demonstrate the advantages of this approach compared to a previously established discrete information theoretic method of assessing spike timing precision. We use this method to analyze a data set of simultaneous turning (yaw) torque output and EMG recordings from the 10 primary muscles of Manduca sexta as tethered moths visually tracked a robotic flower moving with a 1 Hz sinusoidal trajectory. We know that all 10 muscles in this motor program encode the majority of information about yaw torque in spike timings, but we do not know whether individual muscles receive information encoded at different levels of precision. Using the continuous MI method, we demonstrate that the scale of temporal precision in all motor units in this insect flight circuit is at the sub-millisecond or millisecond-scale, with variation in precision scale present between muscle types. This method can be applied broadly to estimate spike timing precision in sensory and motor circuits in both invertebrates and vertebrates.

Thalamic state influences timing precision in the thalamocortical circuit

Sensory signals from the outside world are transduced at the periphery, passing through thalamus before reaching cortex, ultimately giving rise to the sensory representations that enable us to perceive the world. The thalamocortical circuit is particularly sensitive to the temporal precision of thalamic spiking due to highly convergent synaptic connectivity. Thalamic neurons can exhibit burst and tonic modes of firing that strongly influence timing within the thalamus. The impact of these changes in thalamic state on sensory encoding in the cortex, however, remains unclear. Here, we investigated the role of thalamic state on timing in the thalamocortical circuit of the vibrissa pathwayin the anesthetized rat. We optogenetically hyperpolarized thalamus while recording single unit activity in both thalamus and cortex. Tonic spike triggered analysis revealed temporally precise thalamic spiking that was locked to weak white-noise sensory stimuli, while thalamic burst spiking was associated with a loss in stimulus-locked temporal precision. These thalamic state dependent changes propagated to cortex such that the cortical timing precision was diminished during the hyperpolarized (burst biased) thalamic state. While still sensory driven, the cortical neurons became significantly less precisely locked to the weak white-noise stimulus. The results here suggests a state dependent differential regulation of spike timing precision in the thalamus that could gate what signals are ultimately propagated to cortex.

Dynamic changes of timing precision in timed actions during a behavioural task in guinea pigs

Temporal precision is a determinant of performance in various motor activities. Although the accuracy and precision of timing in activities have been previously measured and quantified, temporal dynamics with flexible precision have not been considered. Here, we examined the temporal dynamics in timed motor activities (timed actions) using a guinea pig model in a behavioural task requiring an animal to control action timing to obtain a water reward. In well-trained animals, momentary variations in timing precision were extracted from the temporal distribution of the timed actions measured over daily 12-h sessions. The resampling of the observed time of action in each session demonstrated significant changes of timing precision within a session. Periods with higher timing precision appeared indiscriminately during the same session, and such periods lasted ~ 20 min on average. We conclude that the timing precision in trained actions is flexible and changes dynamically in guinea pigs. By elucidating the brain mechanisms involved in flexibility and dynamics with an animal model, future studies should establish more effective methods to actively enhance timing precision in our motor activities, such as sports.