Biology subjects

Milekovic, T.

Publications and source records attributed to Milekovic, T..

4 recordsLinked to original sources

bioRxiv2022

Interpreting dynamics of neural activity after dimensionality reduction

Dimensionality reduction methods are frequently used to analyze high-dimensional activity of cortical neuron populations during behavior. The resulting oscillatory trajectories that consistently emerge from this analysis have been interpreted as a signature of latent dynamical systems. Here, we show that these oscillatory trajectories necessarily result from applying dimensionality reduction methods on recordings that approximately exhibit continuous variation in time, regardless of whether or not the recorded system incorporates latent dynamics.

neuroscience↗

bioRxiv2020

Electrical Stimulation Of The Cervical Dorsal Roots Enables Functional Arm And Hand Movements In Monkeys With Cervical Spinal Cord Injury

Recovering arm control is a top priority for people with paralysis. Unfortunately, the complexity of the neural mechanisms underlying arm control practically limited the effectiveness of neurotechnology approaches. Here, we exploited the neural function of surviving spinal circuits to restore voluntary arm and hand control in three monkeys with spinal cord injury using spinal cord stimulation. Our neural interface leverages the functional organization of the dorsal roots to convey artificial excitation via electrical stimulation to relevant spinal segments at appropriate movement phases. Stimulation bursts targeting specific spinal segments produced sustained arm movements enabling monkeys with arm paralysis to perform an unconstrained reach-and-grasp task. Stimulation specifically improved strength, task performances and movement quality. Electrophysiology suggested that residual descending inputs were necessary to produce coordinated movements. The efficacy and reliability of our approach hold realistic promises of clinical translation.

bioengineering↗

bioRxiv2020

Motor cortical dynamics are shaped by multiple distinct subspaces during naturalistic behavior

Behavior relies on continuous influx of sensory information about the body. In primates, motor cortex must integrate somatic feedback to accurately reach and manipulate objects. Yet, prior work demonstrates that motor cortex is well-described with deterministic, rather than input-driven, dynamics. Deterministic dynamics facilitate robust movement generation, but flexible motor output requires rapid responses to unexpected inputs. Here, we resolved this paradox by simultaneously recording neural population activity in motor and somatosensory cortex from four monkeys performing a naturalistic object interaction behavior resulting in occasional errors. Motor cortex was strikingly input-driven surrounding behavioral error correction. Intriguingly, input-driven dynamics were isolated to a subspace of the population activity that putatively captured somatosensory feedback. Using electrical stimulation of ascending somatosensory tracts, we causally verified that this feedback subspace captured peripheral inputs to cortex. Our results demonstrate that cortical activity is compartmentalized within distinct subspaces, enabling flexible integration of salient inputs for robust behavior.

neuroscience↗

bioRxiv2019

A VERSATILE ROBOTIC PLATFORM FOR THE DESIGN OF NATURAL, THREE-DIMENSIONAL REACHING AND GRASPING TASKS IN MONKEYS

Translational studies on motor control and neurological disorders require detailed monitoring of sensorimotor components of natural limb movements in relevant animal models. However, available experimental tools do not provide a sufficiently rich repertoire of behavioral signals. Here, we developed a robotic platform that enables the monitoring of kinematics, interaction forces, and neurophysiological signals during user-definable upper limb tasks for monkeys. We configured the platform to position instrumented objects in a three-dimensional workspace and provide an interactive dynamic force-field. We show the relevance of our platform for fundamental and translational studies with three example applications. First, we study the kinematics of natural grasp in response to variable interaction forces. We then show simultaneous and independent encoding of kinematic and forces in single unit intra-cortical recordings from sensorimotor cortical areas. Lastly, we demonstrate the relevance of our platform to develop clinically relevant brain computer interfaces in a kinematically unconstrained motor task

neuroscience↗