Fig 1.
Photographs of headstage socket, and waterproof thimble attachment.
A polyamide head-stage socket is shown with its connecting stainless steel thimble and screws, and also a PCB connector which is placed inside during surgery (A). A wireless system attachment was created using electrode connectors, glue, and a sewing thimble (B).
Fig 2.
Rat skull-implant diagram for the water-maze recording group.
Diagram showing the location of the headstage socket on the rat’s skull, along with the electrode and anchor positions. Photographs taken during the surgery procedure depict the position of electrodes, socket and anchors (top), and the position of the PCB connector (bottom). The control group received the electrodes, anchors and PCB connector, but no headstage socket.
Fig 3.
Photographs of Waterproof Connector.
The wireless system connector provides stability for the wireless system, and is shown both without (A) and with (B) the W32 wireless system (Multichannel Systems Gmbh; Germany). With the waterproofing latex finger-cot (C), the rat is able to swim freely about the water maze (D) whilst LFP is transmitted wirelessly.
Fig 4.
Rat behavioural performance during the water-maze task.
Performance differences are shown between the wireless system (square) and non-wireless system (triangle) groups, + SEM. Both groups had shown comparable performance on all measures, including the time taken to reach the goal arm (A) and platform (B), as well as the number of initial (C) and repetitive (D) errors.
Fig 5.
LFP recording quality inside the water maze.
A representative trace from the dCA1 and striatal electrodes is shown (A), alongside representative spectrograms pertaining to a single trial inside the water maze (B). Recording quality was maintained throughout the training sessions, and the system was able to quickly recover from movement artefacts, which arose whenever the rats shook their head or hit the system on the maze wall.
Fig 6.
Power spectral density and coherence at different task phases.
Power-spectral density (PSD) is shown for the dCA1 (A) and striatum (B), along with the coherence between these two regions (C). The traces shown are: pre-maze (blue), water-maze (red) and platform (black), ± SEM. A magnified signal (0–20 Hz) is shown in the inset. Notably, theta-frequency PSD and coherence are both elevated inside the water-maze environment. Coherence is also elevated for rats on the maze platform, albeit to lesser extent.
Fig 7.
Cross-frequency modulation at different task phases.
Montage depicting the theta-gamma cross-frequency modulation between and within the dCA1 and striatal (STR) brain regions, for each of the three task phases (pre-maze, maze and platform). The y-axis represents the modulated gamma frequency, whereas the x-axis is the modulating theta frequency. MI values are represented as a z-score following statistical comparisons with shuffled data. Notably, cross-frequency modulation is at its strongest for dCA1 gamma, for rats inside the maze. Intra-striatal cross-frequency modulation is also at its strongest when the rat is not engaged in the water-maze task (Pre-Maze; STR-STR).
Fig 8.
Recovered LFP following artefact removal.
The mean percentage of recovered LFP + SEM is shown for both dCA1 and striatal (dl-Str) brain regions, for behavioural sessions 1–4. The percentage of recovered signal increased for both brain regions, from ~85% in session 1, to ~95% in session 4.