An Integrated Platform for In Vivo Electrophysiology in Spatial Cognition Experiments

Abstract

Spatial cognition research requires behavioral paradigms that can distinguish between different navigational elements, such as allocentric (map-like) navigation and egocentric (e.g., body centered) navigation. To fill this need, we developed a flexible experimental platform that can be quickly modified without the need for significant changes to software and hardware. In this paper, we present this inexpensive and flexible behavioral platform paired with software which we are making freely available. Our behavioral platform serves as the foundation for a range of experiments, and although developed for assessing spatial cognition, it also has applications in the nonspatial domain of behavioral testing. There are two components of the software platform, "Maze" and "Stim Trigger." While intended as a general platform, presently both programs can work in conjunction with Neuralynx and Open Ephys electrophysiology acquisition systems, allowing for precise time stamping of neural events. The Maze program includes functionality for automatic reward delivery based on user defined zones. "Stim Trigger" permits control of brain stimulation via any equipment that can be paired with an Arduino board. We seek to share our software and leverage the potential by expanding functionality in the future to meet the needs of a larger community of researchers.

Keywords: brain stimulation; electrophysiology; novel tools; open-source software; spatial cognition.

Figure 1.

Pinout mapping for IDC breakout boards in the behavioral platform connecting the electronic components to USB Access I/O modules. Each pin offers a connection to control LEDs, solenoids, or send TTL signals. The circle denotes the maze surface and which electronic components are mounted under the maze.

Figure 2.

“Maze” GUI. A, Control of electronic hardware including reward type, stimulation parameters, and valve control. B, Characteristics of zones of interest, including number of zones. C, Counters and configuration controls. D, Zone location, selection of “Zones” and “Rewarded zones,” and randomization of rewarded zones. E, LED test and auto calibration controls. F, Animal ID and comment boxes. G, Real-time position tracking. Zones are marked with * along with their identification number.

Figure 3.

“Stim Trigger” software GUI. Top, Stimulus setting input boxes. Middle, “Send Manually” triggers stimulation with each mouse click, “Start Ext Trigger” turns on the automatic trigger, “Clear Stim” resets the stimulation counters (right). Bottom, Radio Buttons to select the timing of the automatic trigger on the rising edge or the falling edge of the input TTL from the external triggering source.

Figure 4.

Bonsai workflow for animal’s location extraction and transfer to Maze. Each graphical element represents a function within the data processing pipeline. From left to right, The live video is processed to extract and transmit the animal’s location to both Maze and a .csv file.

Figure 5.

A, Complex Spatial Sequence Task. Schematic for the complex spatial sequence task. The rat always starts at zone 5 and continues to zones 1-2-3-4-1-2-3-5-. The Zones and Rewarded Zones are set in the “Maze” GUI. As no reward delay was used for this task, as soon as the animal enters the currently active zone, an automatic reward is delivered and the next “Rewarded zone” becomes active following the input order. B, Capture of the behavior during a “cued run.” C, Two plots showing the activity of two hippocampal place cells as a heat plot of occupancy-adjusted firing rate, using an evenly spaced color-map with max rate indicated in red. The firing frequency is also shown. Only areas with a high enough occupancy during the task are represented in the figures.

Figure 6.

Maze GUI for OPPA task. A, Control of electronic hardware including reward type: none as manual food reward is used. B, Five zones of interest. C, Counters and configuration controls. D, Allocated coordinates for zone location. E, LED test and auto calibration controls. F, Animal ID and comment boxes. G, Real time position tracking with zones (*) in green, unused in black. Unused zones are listed above and below the zones that are positioned on the maze for visualization.

Figure 7.

Map-to-action (MAT) task. Layout for the allocentric (left), transformation (middle), and egocentric conditions (right) of the MAT task. For allocentric and transformation, using “Maze” software, one “Rewarded zone” is used. All the arms S1–S7 and R are marked as “Zones” as well as a center zone. The coordinates as well as the size of the zones can be set in the “Maze” GUI (Fig. 2B,D). No reward delay was used for this task. For egocentric the experimenter determines zone entries manually and triggers the reward using “Send Manually” in “Stim Trigger” (Fig. 3).