Circadian Activity Monitoring
Overview
Circadian activity monitoring provides continuous, non-invasive recording of locomotor activity patterns in the home cage over days to weeks using infrared beam-break arrays, passive infrared motion sensors, or running wheel rotations. The resulting actograms reveal the animal's circadian rhythm — the endogenous ~24-hour oscillation in rest-activity cycles that is controlled by the suprachiasmatic nucleus (SCN) of the hypothalamus and entrained by environmental light-dark cycles.
Circadian analysis extracts key rhythm parameters: period (tau, the free-running cycle length under constant conditions), amplitude (the strength of the rhythm), acrophase (the time of peak activity), and alpha (the duration of the active phase). Disruptions in these parameters are observed in clock gene mutants, aging, neurodegenerative diseases, and after experimental jet lag or shift-work protocols. Running wheel activity provides particularly clean data because it reflects volitional, motivated locomotion.
ConductMaze collects continuous activity data from IR beam arrays or running wheel encoders, generates double-plotted actograms, and performs periodogram analysis (chi-square, Lomb-Scargle) to compute circadian period and amplitude. The software supports free-running protocols (constant dark/DD or constant light/LL), light-pulse phase-shifting experiments, and jet lag protocols with automated light schedule control.
Trial Flow
Setup Sensors
Install IR beam arrays or running wheel in home cage
Entrained Baseline
Record activity under standard 12L:12D for 7+ days
Free-Running Phase
Switch to constant dark (DD) to measure endogenous period
Continuous Recording
Activity counts binned in 5-10 min epochs 24/7
Phase Perturbation
Light pulse, jet lag, or feeding schedule shift (optional)
Actogram Generation
Double-plotted actogram with period line overlay
Analysis
Periodogram, amplitude, acrophase computation
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Recording Duration | days | 21 | Total recording period (7 entrained + 14 free-running typical) |
| Bin Size | minutes | 5 | Activity count epoch duration |
| Light Schedule | enum | 12L:12D then DD | Light-dark cycle protocol |
| Sensor Type | enum | IR beam array | Activity detection method (IR beams, running wheel, PIR) |
| Light Intensity | lux | 300 | Light phase illumination level |
| Food Access | enum | Ad libitum | Feeding schedule (ad lib, timed restricted feeding) |
Metrics
| Metric | Unit | Description |
|---|---|---|
| Period (Tau) | hours | Free-running circadian period under constant conditions — primary rhythm parameter |
| Amplitude | counts | Peak-to-trough activity difference — rhythm robustness |
| Acrophase | hours | Time of peak activity relative to light cycle — rhythm phase |
| Alpha Duration | hours | Duration of the active phase per cycle |
| Total Daily Activity | counts/day | Cumulative activity per 24-hour period — general locomotion |
| Light/Dark Activity Ratio | ratio | Dark-phase / Light-phase activity — nocturnality index |
| Phase Shift Magnitude | hours | Activity onset shift after light pulse or jet lag |
Sample Data
| Subject | Group | Condition | Period_h | Amplitude | Acrophase_ZT | Alpha_h | Daily_Activity |
|---|
Representative data for illustration purposes. Actual values will vary by species, strain, and experimental conditions.
Applications
- 1Clock gene research — phenotyping Per, Cry, Clock, and Bmal1 mutant mice
- 2Jet lag and shift work — re-entrainment dynamics after light-dark cycle shifts
- 3Aging — circadian rhythm fragmentation and amplitude decline in old mice
- 4Neurodegeneration — activity disruption in Alzheimer, Parkinson, and Huntington models
- 5Chronopharmacology — time-of-day effects on drug efficacy and behavior
Related Protocols
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