A new device for the simultaneous recording of cerebral, cardiac, and muscular electrical activity in freely moving rodents

AbstractWe present a new technique for the simultaneous capture of bioelectrical time signals from the brain and peripheral organs of freely moving rodents. The recording system integrates all systemic signals into an electrical interface board that is mounted on an animal's head for an extended period. The interface board accommodates up to 48 channels, enabling us to analyze neuronal activity patterns in multiple brain regions by comparing a variety of physiological body states over weeks and months. This technique will advance the understanding of the neurophysiological correlate of mind–body associations in health and disease

The Integration of Goal-Directed Signals onto Spatial Maps of Hippocampal Place Cells

Summary: Spatial firing of hippocampal place cells varies depending on the animal’s behavior relative to its goals. Here, rats were trained to approach visually guided reward ports in a two-dimensional open field. Hippocampal place cells encoded two independent pieces of information, spatial representation and goal-directed representation, by amplifying firing rates within their place fields specifically while the animal was moving toward a specific goal location. Irrespective of running speed and direction, substantial place-selective firing was observed that sustained a basal spatial map independent of goal-directed signals. When animals were allowed to freely forage in the field, in-field firing rates similarly increased when the animals transiently ran toward remembered goal locations. Disruption of medial septal activity significantly decreased goal-directed firing while maintaining spatial representation patterns. The findings indicate that the integrated encoding of spatial and goal-directed signals by hippocampal circuits is crucial for flexible spatial navigation to a goal location. : Aoki et al. find that firing rates of CA1 neurons increase when rats are running toward a goal location irrespective of the positional relationship between their place fields and goal location. The results suggest possible neurophysiological mechanisms for encoding place-selective and goal-directed signals by a hippocampal cell. Keywords: place cells, hippocampus, goal-directed behavior, theta oscillation, medial septu

Awake hippocampal synchronous events are incorporated into offline neuronal reactivation

Summary: Learning novel experiences reorganizes hippocampal neuronal circuits, represented as coordinated reactivation patterns in post-experience offline states for memory consolidation. This study examines how awake synchronous events during a novel run are related to post-run reactivation patterns. The disruption of awake sharp-wave ripples inhibited experience-induced increases in the contributions of neurons to post-experience synchronous events. Hippocampal place cells that participate more in awake synchronous events are more strongly reactivated during post-experience synchronous events. Awake synchronous neuronal patterns, in cooperation with place-selective firing patterns, determine cell ensembles that undergo pronounced increases and decreases in their correlated spikes. Taken together, awake synchronous events are fundamental for identifying hippocampal neuronal ensembles to be incorporated into synchronous reactivation during subsequent offline states, thereby facilitating memory consolidation

Spatial Representation of Hippocampal Place Cells in a T-Maze with an Aversive Stimulation

The hippocampus contains place cells representing spaces in an environment, and these place cells have been suggested to play a fundamental role in the formation of a cognitive map for spatial processing. However, how alterations in the firing patterns of place cells in response to aversive events encode the locations tied to these aversive events is unknown. Here, we analyzed spiking patterns of place cell ensembles in the dorsal hippocampal CA1 region of rats performing a T-maze alternation task with an aversive air-puff stimulation applied at a specific location on one side of a trajectory. The intensity of the air puff was adjusted so that the rats decreased their running speed before passing the aversive location. The addition of the aversive stimulus induced reorganization of place cell ensembles on both left and right trajectories with and without the aversive stimulus, respectively. Specifically, the animals showed a more abundant spatial representation in the vicinity of the aversive location. Removing the aversive stimulus induced new spatial firing patterns on both of the trajectories that differed from those both before and during application of the aversive stimulus. These results demonstrate that hippocampal spatial maps are flexibly reorganized to represent particular aversive events

Development of a Stereo-Vision Based High-Throughput Robotic System for Mouse Tail Vein Injection

In this paper, we present a robotic device for mouse tail vein injection. We propose a mouse holding mechanism to realize vein injection without anesthetizing the mouse, which consists of a tourniquet, vacuum port, and adaptive tail-end fixture. The position of the target vein in 3D space is reconstructed from a high-resolution stereo vision. The vein is detected by a simple but robust vein line detector. Thanks to the proposed two-staged calibration process, the total time for the injection process is limited to 1.5 minutes, despite that the position of needle and tail vein varies for each trial. We performed an injection experiment targeting 40 mice and succeeded to inject saline to 37 of them, resulting 92.5% success ratio.Comment: accepted to ICRA2022 (7 pages, 11 figures, 2 tables