The current rise of neurodevelopmental disorders poses a critical need to detect risk early in order to rapidly intervene. One of the tools pediatricians use to track development is the standard growth chart. The growth charts are... more
The current rise of neurodevelopmental disorders poses a critical need to detect risk early in order to rapidly intervene. One of the tools pediatricians use to track development is the standard growth chart. The growth charts are somewhat limited in predicting possible neurodevelopmental issues. They rely on linear models and assumptions of normality for physical growth data – obscuring key statistical information about possible neurodevelopmental risk in growth data that actually has accelerated, non-linear rates-of-change and variability encompassing skewed distributions. Here, we use new analytics to profile growth data from 36 newborn babies that were tracked longitudinally for 5 months. By switching to incremental (velocity-based) growth charts and combining these dynamic changes with underlying fluctuations in motor performance – as the transition from spontaneous random noise to a systematic signal – we demonstrate a method to detect very early stunting in the development of voluntary neuromotor control and to flag risk of neurodevelopmental derail.
It has recently been demonstrated that soleus motor-evoked potentials (MEPs) are facilitated prior to the onset of dorsiflexion. The purpose of this study was to examine if this could be explained by removal of spinal inhibition of the... more
It has recently been demonstrated that soleus motor-evoked potentials (MEPs) are facilitated prior to the onset of dorsiflexion. The purpose of this study was to examine if this could be explained by removal of spinal inhibition of the descending command to soleus motoneurons. To test this, we investigated how afferent inputs from the tibialis anterior muscle modulate the corticospinal activation of soleus spinal motoneurons at rest, during static contraction and prior to movement. MEPs activated by transcranial magnetic stimulation (TMS) and Hoffmann reflexes (H-reflexes), activated by electrical stimulation of the posterior tibial nerve (PTN), were conditioned by prior stimulation of the common peroneal nerve (CPN) at a variety of conditioning-test (CT) intervals. MEPs in the precontracted soleus muscle were inhibited when the TMS pulse was preceded by CPN stimulation with a CT interval of 35 ms, and they were facilitated for CT intervals of 50-55 ms. A similar inhibition of the s...
Modern theories of behavioral control converge with the idea that goal-directed/voluntary behaviors are intimately tied to the evaluation of resources. Of key relevance in the decision-making processes that underlie action selection are... more
Modern theories of behavioral control converge with the idea that goal-directed/voluntary behaviors are intimately tied to the evaluation of resources. Of key relevance in the decision-making processes that underlie action selection are those stimuli that bear emotional content. However, even though it is acknowledged that emotional information affects behavioral control, the exact way in which emotions impact on action planning is largely unknown. To clarify this issue, I gave an emotional version of a go/no-go task to healthy participants, in which they had to perform the same arm reaching movement when pictures of fearful or happy faces were presented, and to withhold it when pictures of faces with neutral expressions were presented. This task allows for the investigation of the effects of emotional stimuli when they are task-relevant without conflating movement planning with target detection and task switching. It was found that both the reaction times (RTs) and the percentages ...
Performing multi-joint arm movements in controllable dynamic environments during functional magnetic resonance imaging (fMRI) could provide important insights into the brain mechanisms involved in human motor control and related... more
Performing multi-joint arm movements in controllable dynamic environments during functional magnetic resonance imaging (fMRI) could provide important insights into the brain mechanisms involved in human motor control and related dysfunctions. In order to obtain useful data, these movements must be possible and comfortable for the subject within the narrow bore of the scanner and should not create any movement artifacts in the image. We found that commonly studied arm movements involving the shoulder create movement artifacts, and investigated alternative multi-joint arm movements within a mock-up of an MR scanner. We selected movements involving the elbow and wrist joints, with an extension attached to the hand, and propose a dedicated kinematic structure using the MR compatible actuators we have previously developed
Modern theories of behavioral control converge with the idea that goal-directed/voluntary behaviors are intimately tied to the evaluation of resources. Of key relevance in the decision-making processes that underlie action selection are... more
Modern theories of behavioral control converge with the idea that goal-directed/voluntary behaviors are intimately tied to the evaluation of resources. Of key relevance in the decision-making processes that underlie action selection are those stimuli that bear emotional content. However, even though it is acknowledged that emotional information affects behavioral control, the exact way in which emotions impact on action planning is largely unknown. To clarify this issue, I gave an emotional version of a go/no-go task to healthy participants, in which they had to perform the same arm reaching movement when pictures of fearful or happy faces were presented, and to withhold it when pictures of faces with neutral expressions were presented. This task allows for the investigation of the effects of emotional stimuli when they are task-relevant without conflating movement planning with target detection and task switching. It was found that both the reaction times (RTs) and the percentages of errors increased when the go-signal was the image of a fearful looking face, as opposed to when the go-signal was a happy looking face. Importantly, to control for the role of the features of the stimuli, I ran a control task in which the same pictures were shown; however, participants had to move/withhold the commanded movement according to gender, disregarding the emotional valence. In this context, the differences between RTs and error percentages between the fearful and happy faces disappeared. On the one hand, these results suggest that fearful facial stimuli are likely to capture and hold attention more strongly than faces that express happiness, which could serve to increase vigilance for detecting a potential threat in an observer's environment. On the other hand, they also suggest that the influence of fearful facial stimuli is not automatic, but it depends on the task requirements.
Traditionally conceived of and studied as a disorder of cognitive and emotional functioning, schizo-phrenia (SZ) is also characterized by alterations in bodily sensations. These have included subjective reports based on self-evaluations... more
Traditionally conceived of and studied as a disorder of cognitive and emotional functioning, schizo-phrenia (SZ) is also characterized by alterations in bodily sensations. These have included subjective reports based on self-evaluations and/or clinical observations describing motor, as well as sensory-based corporeal anomalies. There has been, however, a paucity of objective methods to capture and characterize bodily issues in SZ. Here we present a new research method and statistical platform that enables precise evaluation of peripheral activity and its putative contributions to the cognitive control of vi-suomotor actions. Specifically, we introduce new methods that facilitate the individualized characterization of the function of sensory-motor systems so as to detect if subjects perform outside of normal limits. In this paper, we report data from a cohort of patients with a clinical diagnosis of SZ. First, we characterize neurotypical subjects performing a visually guided pointing task that requires visuomotor transformations, multi-joint coordination, and the proper balance between different degrees of intent, among other factors. Then we measure SZ patients against the normative statistical ranges empirically determined. To this end, we examine the stochastic signatures of minute fluctuations in motor performance (micro-movements) of various velocity-and geometric-transformation-dependent trajectory parameters from the hand motions. These include the motions en-route to the target as well as spontaneous (without instructions) hand-retractions to rest. The comparisons reveal fundamental differences between SZ patients and controls. Specifically, velocity-dependent signatures show that SZ patients move significantly slower than controls with more noise and randomness in their moment-by-moment hand micro-motions. Furthermore, the normative geometric-dependent signatures of deliberateness are absent from the goal-directed reaches in SZ, but present within normative ranges in their spontaneous hand retractions to rest. Given that the continuous flow of micro-motions contributes to internally sensed feedback from self-produced movements, it is highly probable that sensory-motor integration with externally perceived inputs is impaired. Such impairments in this SZ cohort seem to specifically alter the balance between deliberate and spontaneous control of actions. We interpret these results as potential indexes of avolition and lack of agency and action ownership. We frame our results in the broad context of Precision Psychiatry initiatives and discuss possible implications on the putative contributions of the peripheral nervous system to the internal models for the cognitive control of self-produced actions in the individual with a clinical diagnosis of SZ.
Traditionally conceived of and studied as a disorder of cognitive and emotional functioning, schizophrenia (SZ) is also characterized by alterations in bodily sensations. These have included subjective reports based on self-evaluations... more
Traditionally conceived of and studied as a disorder of cognitive and emotional functioning, schizophrenia (SZ) is also characterized by alterations in bodily sensations. These have included subjective reports based on self-evaluations and/or clinical observations describing motor, as well as sensory-based corporeal anomalies. There has been, however, a paucity of objective methods to capture and characterize bodily issues in SZ. Here we present a new research method and statistical platform that enables precise evaluation of peripheral activity and its putative contributions to the cognitive control of visuomotor actions. Specifically, we introduce new methods that facilitate the individualized characterization of the function of sensory-motor systems so as to detect if subjects perform outside of normal limits. In this paper, we report data from a cohort of patients with a clinical diagnosis of SZ. First, we characterize neurotypical subjects performing a visually guided pointing ...
It has recently been demonstrated that soleus motor-evoked potentials (MEPs) are facilitated prior to the onset of dorsiflexion. The purpose of this study was to examine if this could be explained by removal of spinal inhibition of the... more
It has recently been demonstrated that soleus motor-evoked potentials (MEPs) are facilitated prior to the onset of dorsiflexion. The purpose of this study was to examine if this could be explained by removal of spinal inhibition of the descending command to soleus motoneurons. To test this, we investigated how afferent inputs from the tibialis anterior muscle modulate the corticospinal activation of soleus spinal motoneurons at rest, during static contraction and prior to movement. MEPs activated by transcranial magnetic stimulation (TMS) and Hoffmann reflexes (H-reflexes), activated by electrical stimulation of the posterior tibial nerve (PTN), were conditioned by prior stimulation of the common peroneal nerve (CPN) at a variety of conditioning-test (CT) intervals. MEPs in the precontracted soleus muscle were inhibited when the TMS pulse was preceded by CPN stimulation with a CT interval of 35 ms, and they were facilitated for CT intervals of 50-55 ms. A similar inhibition of the s...
Understanding how humans control unstable systems is central to many research problems, with applications ranging from quiet standing to aircraft landing. Increasingly much evidence appears in favor of event-driven control hypothesis:... more
Understanding how humans control unstable systems is central to many research problems, with applications ranging from quiet standing to aircraft landing. Increasingly much evidence appears in favor of event-driven control hypothesis: human operators only start actively controlling the system when the discrepancy between the current and desired system states becomes large enough. The event-driven models based on the concept of threshold can explain many features of the experimentally observed dynamics. However, much still remains unclear about the dynamics of human-controlled systems, which likely indicates that humans employ more intricate control mechanisms. The present paper argues that control activation in humans may be not threshold-driven, but instead intrinsically stochastic, noise-driven. Specifically, we suggest that control activation stems from stochastic interplay between the operator's need to keep the controlled system near the goal state on one hand and the tendency to postpone interrupting the system dynamics on the other hand. We propose a model capturing this interplay and show that it matches the experimental data on human balancing of virtual overdamped stick. Our results illuminate that the noise-driven activation mechanism plays a crucial role at least in the considered task, and, hypothetically, in a broad range of human-controlled processes.
