Nest Building Assessment
Overview
The nest building assessment is a simple, non-invasive assay that exploits the innate motivation of mice to construct nests from available material, providing a sensitive readout of general well-being, thermoregulatory drive, and hippocampal integrity. A single compressed cotton nestlet (approximately 5 cm square, 2.5-3.0 g) is placed in the cage at the onset of the dark cycle, and the nest is scored the following morning using the Deacon 5-point scale, where 1 indicates an untouched nestlet and 5 indicates a near-perfect enclosed dome with walls higher than the body height of the mouse. Because nest construction requires planning, material manipulation, and sustained motivation across several hours, the task engages prefrontal, hippocampal, and basal ganglia circuits in a naturalistic behavioral context.
Impaired nest building has been documented across a remarkably wide range of pathological conditions, including prion disease, Alzheimer transgenic models, hippocampal lesions, hypothalamic dysfunction, and acute sickness behavior induced by lipopolysaccharide or inflammatory cytokines. The Deacon scale is complemented by measuring the percentage of nestlet material shredded—unshredded nestlet weight subtracted from the starting weight divided by the starting weight—which provides a continuous variable more amenable to parametric statistical analysis. Longitudinal tracking across days or weeks enables detection of progressive neurodegeneration or recovery trajectories that would be missed by single-timepoint behavioral batteries.
ConductMaze automates the nest building assessment by photographing the cage at the scoring timepoint and computing both Deacon score (via a convolutional classification model or manual entry) and nestlet shredding percentage from pre-weighed material. The software logs ambient temperature, humidity, and light cycle phase alongside behavioral scores to control for environmental confounds that influence thermoregulatory nest building. Repeated assessments can be scheduled at configurable intervals, with automatic trending, alerts for score deviations exceeding user-defined thresholds, and export of longitudinal data in publication-ready formats.
Trial Flow
Cage Preparation
Transfer mouse to clean cage with standard bedding; remove all existing nesting material and enrichment items
Nestlet Placement
Weigh and place one compressed cotton nestlet (2.5-3.0 g) in the center of the cage at dark cycle onset
Overnight Incubation
Leave animal undisturbed for 12-16 hours spanning the active dark phase for nest construction
Visual Scoring
Score the nest using the Deacon 5-point scale by assessing shape, wall height, and degree of enclosure
Nestlet Weighing
Carefully remove and weigh any unshredded nestlet fragment to calculate percent material used
Photograph Documentation
Capture standardized overhead photograph of the completed nest for archival and automated scoring validation
Data Compilation
Record Deacon score, shredding percentage, nest position, and environmental conditions in the database
Session End
Return mouse to home cage or proceed with next assessment; clean and reset test cage for subsequent animals
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Nestlet Weight | float | 2.7 | Starting weight of the compressed cotton nestlet in grams |
| Assessment Duration | duration | 43200 | Time from nestlet placement to scoring in seconds (default 12 hours) |
| Scoring Timepoint | enum | next_morning | When to score the nest: next_morning, 3h, 6h, or custom |
| Ambient Temperature | temperature | 22 | Room temperature in degrees Celsius during the assessment period |
| Cage Bedding Depth | float | 2.0 | Depth of standard bedding in the test cage in centimeters |
| Light Cycle Phase | enum | dark_onset | Light cycle phase at nestlet placement: dark_onset, light_onset, or mid_dark |
| Number of Assessments | integer | 3 | Number of repeated assessments for longitudinal tracking |
| Inter-Assessment Interval | duration | 604800 | Days between repeated assessments in seconds (default 7 days) |
Metrics
| Metric | Unit | Description |
|---|---|---|
| Deacon Nest Score | score 1-5 | Ordinal nest quality score from 1 (untouched) to 5 (perfect enclosed dome) |
| Nestlet Shredding | % | Percentage of nestlet material torn and incorporated into the nest |
| Unshredded Weight | g | Remaining weight of intact nestlet fragment after the assessment period |
| Nest Height | cm | Maximum wall height of the constructed nest measured from bedding surface |
| Nest Width | cm | Maximum diameter of the nest structure |
| Nest Position | quadrant | Location of the nest within the cage (corner, wall, center) |
| Longitudinal Slope | score/week | Rate of change in Deacon score across repeated weekly assessments |
Sample Data
| Subject | Genotype | Week | Deacon Score | Shredding (%) | Nest Height (cm) | Nest Position |
|---|
Representative data for illustration purposes. Actual values will vary by species, strain, and experimental conditions.
Applications
- 1Neurodegeneration monitoring — tracking progressive decline in nest quality across Alzheimer, prion, and Huntington disease models as an early welfare indicator
- 2Sickness behavior screening — detecting acute illness, pain, or inflammatory responses through rapid suppression of nest building within 24 hours
- 3Hippocampal function assessment — evaluating hippocampal lesion models and pharmacological interventions that disrupt planning and spatial organization
- 4Thermoregulatory phenotyping — characterizing metabolic and hypothalamic mutants with altered thermoregulatory drive using ambient temperature manipulations
- 5Drug side-effect profiling — identifying sedative, anxiogenic, or motivational side effects of novel compounds through changes in nest construction effort
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