Biology subjects

Bollu, T.

Publications and source records attributed to Bollu, T..

3 recordsLinked to original sources

bioRxiv2025

A neural geometry for forelimb proprioception in the cervical spinal cord

Precise, real-time somatosensory feedback is essential for coordinated movement. While the anatomy and physiology of these sensory pathways is well described, their neural code and its construction remains unclear. Here we show that neurons in the cervical spinal cord generate a precise neural representation of the forelimbs kinematic state using muscle and tendon sensory afferent inputs. We identify two classes of movement responsive neurons - the first encodes speed, position and direction of the limb, while the second exhibits precise firing at specific limb positions or grid-like firing patterns that tile space. Their composite population activity is constrained to a low dimensional manifold that is an ordered representation of the position and velocity of the limb. Ablating muscle and tendon sensory afferents, but not cutaneous sensory afferents, disrupts this neural manifold. Moreover, transient perturbations of muscle and tendon afferents in freely moving mice reaching to spatial targets cause end-point errors as predicted by the deficits in the neural code. Our findings demonstrate that spinal networks, one synapse from the periphery, perform the complex computations necessary to represent forelimb movement.

neuroscience↗

bioRxiv2019

Tongue Kinematics. Cortex-dependent corrections as the mouse tongue reaches for, and misses, targets

AbstractPrecise tongue control is necessary for drinking, eating, and vocalizing1, 2. Yet because tongue movements are fast and difficult to resolve, neural control of lingual kinematics remains poorly understood. Here we combine kilohertz frame-rate imaging and a deep learning based neural network to resolve 3D tongue kinematics in mice drinking from a water spout. Successful licks required previously unobserved corrective submovements (CSMs) which, like online corrections during primate reaches3-10, occurred after the tongue missed unseen, distant, or displaced targets. Photoinhibition of anterolateral motor cortex (ALM) impaired online corrections, resulting in hypometric licks that missed the spout. ALM neural activity reflected upcoming, ongoing, and past CSMs, as well as errors in predicted spout contact. Though less than a tenth of a second in duration, a single mouse lick exhibits hallmarks of online motor control associated with a primate reach, including cortex-dependent corrections after misses.

neuroscience↗

bioRxiv2018

Cortical control of kinematic primitives in mice performing a hold-still-center-out reach task

Motor sequences are constructed from primitives, hypothesized building blocks of movement, but mechanisms of primitive generation remain unclear. Using automated homecage training and a novel forelimb sensor, we trained freely-moving mice to initiate forelimb sequences with clearly resolved submillimeter-scale micromovements followed by millimeter-scale reaches to learned spatial targets. Hundreds of thousands of trajectories were decomposed into millions of kinematic primitives, while closed-loop photoinhibition was used to test roles of motor cortical areas. Inactivation of contralateral motor cortex reduced primitive peak speed but, surprisingly, did not substantially affect primitive direction, initiation, termination, or complexity, resulting in isomorphic, spatially contracted trajectories that undershot targets. Our findings demonstrate separable loss of a single kinematic parameter, speed, and identify conditions where loss of cortical drive reduces the gain of motor primitives but does not affect their generation, timing or direction. The combination of high precision forelimb sensing with automated training and neural manipulation provides a system for studying how motor sequences are constructed from elemental building blocks.

neuroscience↗