Variants
The Barnes maze
Spatial memory, without the swimming.
Carol Barnes introduced the circular platform maze in 1979, in a study of memory in ageing rats. The animal learns which of the holes round the edge of a circular table leads to an escape box, using cues in the room. There's no water, so the animal never has to swim.
Barnes maze in eight steps
Open the Barnes maze, calibrate the table and holes, set threshold and subject size, run, then analyse with the Barnes options.
- Clean the maze so no faeces are present, light it evenly so it looks close to white on screen, and plug in the camera first.
- Click ‘Barnes Maze’; its ‘Barnes’ box is ticked for you.
- Click ‘CALIBRATE’, enter the ‘Pool or Arena Diameter (cm)’, click the top, bottom, left and right extremes of the maze surface, then calibrate the holes (or use ‘Suggested Hole Positions’) and click ‘Save and Return’.
- Click ‘CHECK LIGHTING’ and remove shadow and glare dots.
- Start the threshold at 100 and move the ‘Subject size’ slider right until the graticules enclose an area bigger than any faeces but slightly smaller than the animal.
- Enter ‘Max Seconds’, choose an ‘Auto-end on escape hole’ option and the ‘Hole Number’, then click ‘PREPARE’ and line up the target hole with the on-screen circle.
- Click ‘RUN’ as you release the animal. Unless ‘Auto-end on escape hole’ is on, click ‘END’ as it fully enters the target hole.
- Click ‘ANALYZE’, then ‘Advanced’: set the thigmotaxis band so the holes fall within it (e.g. 0.65) and the counter size (e.g. 2.0), then make your SUM and CST files.
More detail
Work from the south (bottom of the screen) side; a small glass beaker as the start container and a white glove and sleeve help keep shadows out. On probe day, enter the learned target hole, tick ‘Probe’ and set ‘Auto-end on escape hole’ to ‘No’.
HVS Image counts hole approaches automatically, records pokes (errors) per hole, and gives latency and path to the target hole and primary path length. Barnes results use Barnes wording (holes, not platforms).
Barnes errors, hole visits and primary path
Barnes results tell you how many wrong holes the subject investigated (errors), which holes it visited and how quickly and directly it reached the escape hole.
More detail
Measures include hole approaches counted automatically, pokes (errors) per hole, latency and path to the target hole, and primary path length (the route from the start to the first approach of the escape hole). Set the thigmotaxis band so the holes fall in it (e.g. 0.65) and the counter size for hole investigation (e.g. 2.0).
For a probe day, tick ‘Probe’ in Monitor on the Barnes maze Run screen. Primary errors are the wrong holes investigated before the first approach of the escape hole.
Reading Barnes maze results
Look at errors (pokes) per hole, latency and path to the target hole and primary path length, and check the paths look clean before you interpret them.
- Typical control pattern
- No published pattern has been confirmed for this test yet, so compare with your own control group. HVS Image reports hole approaches counted automatically, pokes (errors) per hole, latency and path to the target hole, and primary path length (the route from the start to the first approach of the escape hole).
- Signs of impairment
- In the original platform study, the senescent rats were shown to exhibit poorer memory for the rewarded place (Barnes, 1979).
- Signs of strong memory
- No published pattern has been confirmed for this test yet, so compare with your own control group.
Set-up problems that look like results
- Path jumps at the start: a temporary shadow (your hand or the start container) attracts the tracker; use a small glass beaker, a white glove and sleeve, and work from the south end.
- Straight lines (short tracking drops): make lighting even and diffuse, remove black dots (shadows) in the lighting check, avoid red dots (glare) and close other programs.
- Trial does not end at the escape hole: it ends by itself only if ‘Auto-end on escape hole’ is switched on; otherwise click ‘END’ when the animal fully enters the hole.
More detail
Paths are not artificially smoothed, so jagged paths reflect jerky movement. An animal may investigate a hole without entering, which is why many users leave ‘Auto-end on escape hole’ on ‘No’ and end the trial themselves. Set the thigmotaxis band so the holes fall in it before you read approaches and errors.
Barnes (1979) tested rats on a circular platform which favoured the use of spatial cues for its solution, and found the amount of synaptic enhancement was statistically correlated with the ability to perform the circular platform task.
Questions people ask
How do I calibrate the Barnes maze, and why is there a white patch or are the holes not masked?
Open the Barnes maze, click Calibrate, click the table edges (top, bottom, left, right), then click each hole. 1) Open the Barnes maze; its Barnes box is ticked for you. 2) Click Calibrate and click the table edges in the order top, bottom, left, right. 3) Click each hole as if it were a platform, or enter them as polar positions. 4) Click Save and Return: the holes should show white discs.
More detail
The Barnes maze has its own calibration, separate from the water maze: open the Barnes maze, click Calibrate, click the table edges, then click each hole. Click the table edges in the order N, S, W, E (top, bottom, left, right), then click each hole as you would a platform; with alignment calibration enter holes as polar coordinates (angle = 360 / number of holes, e.g. 30° for 12; distance from centre as a proportion of radius). Enter correct maze and hole diameters. After Save and Return the holes are masked by white discs (pink if auto-end is set). If the holes are not masked, check the Barnes box is ticked, which shows you opened the Barnes maze; if not, close the screen and open the Barnes maze.
Going deeper
If only the top half of the table tracks, dark edges are visible inside the calibrated area: place the camera directly above so the table is round on screen and test by clicking just inside the edge. A displaced hole has been caused by clicking W before S. A faulty or low-battery mouse can double-click. Keep a backup of a working calibration file.
Why doesn't the Barnes trial end automatically when the animal reaches the escape hole?
The trial only ends by itself if 'Auto-end on escape hole' is switched on. 1) On the Barnes maze Run screen, set 'Auto-end on escape hole' to 'Yes' or 'Delay in Secs'. 2) Or choose 'No' and click 'END' (or the remote) when the animal fully enters the hole. 3) Watch the animal: it may look into a hole without going in.
More detail
A Barnes trial ends by itself only if 'Auto-end on escape hole' is switched on in the Barnes maze Run screen; choose 'Yes', 'No' or 'Delay in Secs'. The Barnes maze detects the animal entering the target hole. Many users leave it on 'No' and click 'END' themselves, because an animal may investigate a hole without entering and the tracker ignores dark objects behind the white hole masks, so ending by hand avoids ending too early. Any USB or electrically powered aversive stimulus can be stopped as the subject approaches the target hole.
Going deeper
A Barnes .txp line is start, target hole, subject, descriptor, e.g. C,1,mouse1,groupA. To start from the centre type 'Center' (or C) in the start field; it appears in results.
The Barnes path jumps at the start or shows straight lines. How do I fix it?
Usually a temporary shadow (your hand or the start container) attracts the tracker; work from the bottom of the screen and keep shadows out. 1) Use a small glass beaker as the start container. 2) Wear a white glove and sleeve. 3) Stand at the 'south' end (bottom of the screen). 4) Or click start just after your hand has left the area.
More detail
The tracker scans from the top of the image and attaches to the first object meeting the size and darkness criteria, so shadows from the start container or experimenter cause jumps. Remedies: smaller glass beaker, white glove and sleeve, working from the south end, or starting only once the hand or shadow has left (may miss about 0.5 s). Paths are not artificially smoothed, so jagged paths reflect jerky movement. Short tracking drops (straight lines) come from uneven light or background tasks: make lighting even and diffuse with uplighters around the maze at or below table height, remove black dots (shadows) in the lighting check, avoid red dots (glare), and close other programs.
Going deeper
Camera: open the aperture fully so the table looks near-white like the masks, zoom until the maze almost fills the window, then focus. Set the size slider so the small green box is wider than the tail but fits inside the body. HVS can check set-ups from raw .hvs files. To show the screen during practice, start the Snipping Tool before HVS and use video capture (only HVS should run during real trials) or use a smartphone video.
How do I analyse Barnes trials (errors, hole visits, primary path)?
A Barnes analysis measures how quickly and accurately the animal finds the escape hole: errors (pokes into wrong holes), hole visits, latency and primary path. Use 'Barnes Maze' > 'ANALYZE', with counters round the holes and the thigmotaxis band. 1) In Advanced, set the thigmotaxis band so the holes fall in it (e.g. 0.65) and the counter size for hole investigation (e.g. 2.0). 2) Double-click a trial for the plot, 'OK' for the summary. 3) For many trials make a SUM then a CST; ignore water-maze-only measures.
More detail
The primary path is the route from the start to the first approach of the escape hole, and primary errors are the wrong holes investigated before that first approach; together with latency they show how accurately the animal found the goal. HVS Image counts hole approaches automatically, records pokes (errors) per hole, and gives latency and path to the target hole and primary path length. Set the thigmotaxis band (here the ring containing the holes) and the counter size in Advanced. Barnes results use Barnes wording (holes, not platforms). For a probe day, tick Probe in Monitor on the Barnes maze Run screen.
Going deeper
To overlay paths, highlight one file and click Multi Paths, add trials to Selected Plots, click Plot and Export Image.
Which camera and lighting do I need for a Barnes maze?
It depends on the maze diameter and height and the ceiling height, so send HVS those measurements. For lighting: 1) Light evenly with uplighters around the maze. 2) Remove shadows (black dots) and glare (red dots) in Check Lighting. 3) Aim for a table that looks close to white on screen.
More detail
Camera type depends on maze diameter, maze height and the distance from ceiling to maze surface. Red dots in Check Lighting are glare: change the light angle, move lights further away or use smaller bulbs; dark animals on a white table may still track well, so test. Use four short uplighters evenly around the maze about 2 m out, below the table surface if they spill light downwards, so the table appears close to white.
Going deeper
The Run screen shows the whole camera picture, so a high-resolution camera gives a sharper view of the table. The Barnes tracker ignores the holes, and droppings with shadows.
How do I use the Auditory button for tones in a dry maze?
The Auditory button plays sounds in a dry water maze with 'Auto-end on platform'. 1) Left-click until it shows 'Auditory Off' to turn sound off. 2) Right-click to choose the sound played during the trial ('Tone on Swim') and when the platform is reached ('Tone on End'). 3) The tone stops by itself at the end of each trial and when you close the Run screen.
More detail
The Auditory button is for the dry water maze with 'Auto-end on platform'. Left-click cycles to 'Auditory Off'. Right-click lets you pick the file played during the trial ('Tone on Swim') and on reaching the platform ('Tone on End'). The tone stops by itself at the end of each trial and when the Run screen closes.
Going deeper
To view a path more slowly: use time slices (e.g. 0–10 s, 10–20 s), which save slice plots and analyses, or tick 'Real time plot' to plot dots then a line.
How should I set up a Barnes maze?
Use a round, raised table with holes round the edge and one escape box. Light it brightly and keep cues fixed on the walls. Rotate and wipe the table between animals. Your local ethics committee, licence conditions and vet always take precedence.
More detail
A Barnes maze is a raised circular table with holes round the edge, one leading to an escape box; size it for your species and clean it between animals. Rats 100–122 cm tables, 18–20 holes, 80–90 cm high; mice 65–92 cm [Gawel 2019]; original 122 cm, 18 holes [Barnes 1979]. Rotate and wipe to remove odour [Gawel 2019].
Going deeper
Larger tables favour spatial strategies; walls favour serial search [Gawel 2019].
How should I set subject size for a Barnes or other dry maze?
Set Subject Size so the tracking box is larger than any droppings but smaller than the animal. 1) Start with no faeces on the maze. 2) Move the slider right until the cross appears. 3) Keep going until the graticules are larger than any droppings and slightly smaller than the animal.
More detail
With no faeces present, move the Subject Size slider to the right until the green tracking cross appears, then until the graticules enclose an area larger in all directions than any expected faeces and slightly smaller than the animal. If no cross appears with the threshold at 100, move the slider one step from the left and raise the threshold until it appears. Once faeces appear, check they are consistently ignored and increase subject size if needed.
Going deeper
Centre the cross by adjusting threshold: lower for dark animals on light backgrounds, higher for white animals on dark backgrounds.
For tracking and analysing the test, see HVS Image for the Barnes maze.
Sources
- Barnes (1979). Memory deficits associated with senescence: A neurophysiological and behavioral study in the rat. Journal of Comparative and Physiological Psychology 93(1):74-104. doi:10.1037/h0077579
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