Biology subjects

Santello, M.

Publications and source records attributed to Santello, M..

5 recordsLinked to original sources

bioRxiv2025

Transfer of learned object manipulations between two- and five-digit grasps

Successful object manipulation involves integrating object properties into a motor plan and scaling fingertip forces through learning. This study investigated whether learned manipulations using a two-digit grip transfer to a five-digit grip and vice versa, focusing on the challenges posed by added degrees of freedom in force distribution. The goal of the task was to exert the necessary compensatory torque (Tcom) and vertical forces to minimize object roll on a visually symmetrical object that with an asymmetrical mass distribution. To examine this, subjects performed blocked consecutive learning trials before switching grip type. Our results support the learning transfer between two-digits and five-digit grasp configurations despite challenges in maintaining perfect stability during the grip switch. Subjects adapted their grip forces (GF), center of pressure (CoP), and Tcom to minimize object roll, with significant improvements observed from novel (1st) to transfer (11th) trials. These findings suggest high-level, effector-independent representations of object manipulation that enable generalization across grip types, though some limitations in force distribution and digit position arise during transfers.

neuroscience↗

bioRxiv2024

Human Slip Control: Investigating the Role of Hand Acceleration Modulation in Preventing Slips

Ensuring a stable grasp during manipulative movements is crucial for robotic applications. While grip force has been the primary means of slip control, our human study revealed that trajectory modulation is also an effective slip control policy during pick-and-place tasks. Motivated by these findings, we developed and compared a slip control policy based on trajectory modulation to one based on grip force control for robotic pick-and-place tasks. Our results show that trajectory modulation significantly outperforms grip force control in certain scenarios, highlighting its potential for slip control in robotics. Moreover, we demonstrate the importance of incorporating forward models in developing effective trajectory modulation slip control systems. Overall, our study provides insight into an alternative method for slip control and suggests that humans use trajectory modulation as an alternative to grip force control for slippage prevention. This insight helps design algorithm for improving robotic manipulation tasks to prevent slippage.

neuroscience↗

bioRxiv2021

Leaders are made: Learning acquisition of consistent leader-follower relationships depends on implicit haptic interactions.

Are leaders made or born? Leader-follower roles have been well characterized in social science, but they remain somewhat obscure in sensory-motor coordination. Furthermore, it is unknown how and why leader-follower relationships are acquired, including innate versus acquired controversies. We developed a novel asymmetrical coordination task in which two participants (dyad) need to collaborate in transporting a simulated beam while maintaining its horizontal attitude. This experimental paradigm was implemented by twin robotic manipulanda, simulated beam dynamics, haptic interactions, and a projection screen. Clear leader-follower relationships were learned despite participants not being informed that they were interacting with each other, but only when strong haptic feedback was introduced. For the first time, we demonstrate the emergence of consistent leader-follower relationships in sensory-motor coordination, and further show that haptic interaction is essential for dyadic co-adaptation. These results provide insights into neural mechanisms responsible for the formation of leader-follower relationships in our society.

neuroscience↗

bioRxiv2019

Transcranial focused ultrasound enhances behavioral and network mechanisms underlying response inhibition in humans

Response inhibition is important to avoid undesirable behavioral action consequences. Neuroimaging and lesion studies point to a locus of inhibitory control in right inferior frontal gyrus (rIFG). Electrophysiology studies have implicated a downstream event-related potential from rIFG, the fronto-central P300, as a putative neural marker of the success and timing of inhibition over behavioral responses. However, it remains to be established whether rIFG effectively drives inhibition as represented by the P300 activity, and whether rIFG contributions to inhibition are conveyed through either the P300 timing or amplitude. Here, we aimed to causally uncover the connection between rIFG and P300 for inhibition by using transcranial focused ultrasound (tfUS) to target rIFG of human subjects while they performed a Stop-Signal task. By applying tFUS simultaneous with different task events, we found behavioral inhibition was improved only when applied to rIFG simultaneous with a stop signal. Applying tFUS simultaneous with the go signal or control regions had no impact on behavior. The improvement in inhibition performance caused by tFUS to rIFG during stop conditions occurred through faster stopping times that were paired with significantly shorter P300 latencies, whereas amplitude was not affected. These results reveal a causal connection between rIFG in driving response inhibition in that it may regulate the speed of stopping directly, as indexed by the reduced P300 onset latency during tFUS. Our tFUS-EEG approach provides a causal connection, in healthy humans, between prefrontal rIFG regions and downstream P300 production in service of inhibitory control.

neuroscience↗

bioRxiv2019

Choice of Contact Points Modulates Sensorimotor Cortical Interactions for Dexterous Manipulation

Humans are unique in their ability to perform dexterous object manipulation in a wide variety of scenarios. However, previous work has used a grasping context that predominantly elicits memory-based control of digit forces by constraining where the object should be grasped. For this constrained grasping context, primary motor cortex (M1) is involved in storage and retrieval of digit forces used in previous manipulations. In contrast, when choice of digit contact points is allowed ( unconstrained grasping), behavioral studies revealed that forces are adjusted, on a trial-to-trial basis, as a function of digit position. This suggests a role of online feedback that detects digit position, rather than memory, for force control. However, despite the ubiquitous nature of unconstrained hand-object interactions in activities of daily living, the underlying neural mechanisms are unknown. Using non-invasive brain stimulation and electroencephalography, we found the role of M1 to be sensitive to grasping condition. While confirming the role of M1 in storing and retrieving learned digit forces and position in constrained grasping, we also found that M1 is involved in modulating digit forces to digit position in unconstrained grasping. Furthermore, we found that digit force modulation to position relies on sensorimotor integration mediated by primary sensory cortex (S1) and M1. This finding supports the notion of a greater contribution of somatosensory feedback of digit position in unconstrained grasping. We conclude that the relative contribution of memory and online feedback based on whether contact points are constrained or unconstrained modulates sensorimotor cortical interactions for dexterous manipulation.

neuroscience↗