Quick tips and did-you-knows

One-line tips gathered from the questions HVS users ask. Each is short on purpose.

• Water maze calibration screen: Calibrate every platform position you may use now, centre first: it saves recalibrating mid-experiment.
• Check Lighting: Fix shadows first, then glare, with the threshold at 100, before you touch the threshold.
• Threshold setting: Right-click the arrows for big changes and left-click to fine-tune.
• Water maze run screen: After ‘PREPARE’ the mouse pointer is locked to ‘RUN’, and after ‘RUN’ to ‘END’, so you can control trials from the poolside.
• Probe trials: Keep the learned platform number in probe trials, so your results show time near the target correctly.
• Analysis: Advanced: Trying different settings in ‘Advanced’ can reveal effects that the usual values miss, and you can repeat analyses with different values.
• Making a SUM file: If a SUM will not build, sort the HVS folder by size and leave out tiny files with no path, or make smaller batches.
• Analysis trial list: Newest trials missing? The HVS folder may hold 10,000 or more .hvs files: back it up and move older files into a subfolder.
• Export and calibration: Negative paths, or a calibration that will not save? Set Windows number formats to UK or USA and restart HVS Image.
• Open field analysis grid: Pick a grid size that puts each object in its own cell; you can re-analyse with other grid sizes at any time.
• Open field text export: In the full text file, a zone latency of -1 means the zone was not visited.
• Open field freezing: Not measuring freezing? Enter a large time window (e.g. 100 s) and a small movement (0.1 cm), and leave freezing out of your results.
• Multi-arm results: Per-arm data start from the left-most arm and go clockwise (plus maze: left, top, right, bottom).
• Forced swim, three containers: Ran three containers on a 3 x 3 grid? Move the .hvs files ending 4 to 9 to another folder before analysing, and delete them only after a successful analysis.
• Barnes TXP files: To start a Barnes trial from the centre, type C (the short form of the centre start code) in the start field; it appears in your results.
• Video frame recording: Saving frames rather than video keeps every frame at original resolution and lets you choose compression and frame rate yourself.
• Quadrant measures: Quadrants are NE, SE, SW and NW, with North at the top of the image.
• HVS 6D VR trial running: Trial disrupted? Press Escape, then Enter to re-run it; the original is saved as far as it got.
• HVS 6D VR function keys: Wrong scene? A missing .vrScript file for that key falls back to default.vrScript, so each key needs a file named exactly for it (F1.vrScript for F1, up to F12.vrScript) in C:\Users\[User name]\AppData\LocalLow\HVS Image Software Ltd\HVS 4D VR (a hidden folder).
• HVS 6D VR participant briefing: Tell participants they can turn their body and look around; looking slightly upwards shows the distal cues.
• HVS 6D VR reporting: Your vrScript settings are retained in the .BOND headers, ready for reporting.
• HVS 6D VR end messages: End-of-trial messages can be written in any language, or left blank for no message.
• Behaviour identification: Did you know? HVS Image identifies search strategies with predefined, transparent quantitative rules applied to time-stamped positions, not machine learning or path images.
• Tracking: Did you know? The tracker scans from the top-left and locks on to the first dark object it finds, which is why working from the south side helps.
• Atlantis platform: Did you know? The Atlantis platform sits well below the surface and rises when the subject reaches or dwells at the target, so it won't be found by chance.
• Direct Path Measures: Did you know? The Direct Path classifications are also evaluated for each other calibrated position, so in reversal you can see whether the first approach went to the old or new location.
• Water maze history: Did you know? The Morris water maze has become one of the most frequently used laboratory tools in behavioural neuroscience (D'Hooge and De Deyn, 2001).
• Water maze design: Did you know? Escape from water is relatively immune from activity or body mass differences, which makes the water maze ideal for many experimental models (Vorhees and Williams, 2006).
• Gallagher proximity: Did you know? The proximity measure was found to be highly sensitive to age-related impairment (Gallagher et al., 1993).
• Probe measures: Did you know? Across more than 1600 mouse probe tests, the proximity measure consistently outperformed quadrant, zone and crossing measures in detecting group differences (Maei et al., 2009).
• Virtual water maze: Did you know? A review of over 200 VR navigation papers found that the most popular task used is the virtual analogue of the Morris water maze (Thornberry et al., 2021).
• Virtual reality: Did you know? Rats learn spatial tasks in a virtual environment quite readily when the set-up takes their wide-angle vision into account (Hölscher et al., 2005).
• Elevated plus maze: Did you know? In the original plus-maze validation, neither novelty nor illumination was a significant contributor to the behaviour of the rats (Pellow et al., 1985).
• Radial arm maze: Did you know? In the classic eight-arm maze study, the data suggested no tendency to generalise among spatially adjacent arms (Olton and Samuelson, 1976).
• Open field: Did you know? Mice's tendency to stay close to the walls of an open field decreases gradually during the first minutes of exploration (Simon et al., 1994).
• T-maze: Did you know? Each T-maze alternation trial should be completed in under 2 min (Deacon and Rawlins, 2006).
• Barnes maze history: Did you know? The Barnes maze began as a circular platform which favoured the use of spatial cues for its solution (Barnes, 1979).

More background on the system these tips belong to: HVS Image systems for neuroscience: background, validation and applications.

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