"Signal" - what is it, definition of the term
Signal — a quantifiable alteration in a physical or biological system that conveys information from a source to a receiver, allowing detection, interpretation and appropriate response; in rodent research such transmissions may include electrical potentials, chemical gradients or behavioral cues that trigger neural or physiological processes.
Detailed information
Rats and mice rely on a variety of biological cues to coordinate social interaction, predator avoidance, and foraging. These cues are transmitted through distinct channels that differ in frequency range, modality, and physiological origin.
Chemical cues dominate olfactory communication. Pheromonal compounds released from the flank glands or urine convey reproductive status, territorial boundaries, and individual identity. Detection occurs via the vomeronasal organ, which triggers stereotyped neural patterns in the accessory olfactory bulb.
Auditory cues consist of ultrasonic vocalizations (USVs) ranging from 20 to 100 kHz. Pup distress calls, adult courtship trills, and aggression bursts each occupy specific temporal and spectral envelopes. Production involves laryngeal musculature; reception relies on the cochlear hair cells tuned to high frequencies.
Tactile cues are mediated by whisker (vibrissae) contact. Whisker deflection generates mechanoreceptor activation, producing precise spatiotemporal maps in the barrel cortex. This system supports texture discrimination, object localization, and navigation in dark environments.
Electrophysiological cues emerge from neuronal action potentials that propagate along axonal pathways. In rodents, spike timing and firing rate encode sensory inputs, motor commands, and reward predictions. Recording techniques such as in‑vivo electrophysiology and calcium imaging capture these rapid events.
Key applications of these biological cues in research include:
- Behavioral assays that quantify USV frequency to assess anxiety or social motivation.
- Olfactory discrimination tests that measure investigation time of pheromone‑laden substrates.
- Whisker‑based texture discrimination tasks used to probe somatosensory processing.
- Electrophysiological mapping of neural circuits underlying learning and memory.
Understanding each channel’s physical parameters and neural correlates enables precise manipulation of rodent models, facilitating the study of neuropsychiatric disorders, sensory processing deficits, and pharmacological interventions.