Olfaction in the canine cognitive and emotional processes: From behavioral and neural viewpoints to measurement possibilities

Cholecystokinin neurons in the spinal trigeminal nucleus interpolaris regulate mechanically evoked predatory hunting in male mice

Predatory hunting plays a critical role in animal survival. Motion-related vibrissal somatosensory signaling is essential for prey detection and hunting in mice. However, little is known about the neural circuits that convert vibrissal somatosensory cues to trigger predatory hunting. Here, we report that mechanical force onto the vibrissal area of the male mice is a key stimulus for predatory hunting. Mechanically evoked predatory hunting was abrogated by the chemogenetic inactivation of cholecystokinin-positive (Cck+) neurons in the spinal trigeminal nucleus interpolaris (Sp5I). The Cck+ Sp5I neurons responded to the intensity of mechanical stimulus and sent neural signals to the superior colliculus that were relevant to stereotypical predatory hunting motor actions. Synaptic inactivation of the projections from Cck+ Sp5I neurons to the superior colliculus impaired mechanically evoked predatory attacks. Together, these data reveal a spinal trigeminal nucleus neural circuit that is specifically engaged in translating vibrissal somatosensory cues to provoke predatory hunting.

The manipulation of odor availability of training aids used in detection canine training

Detection canines can identify numerous substances for which they have been trained. Historically, and a point of ongoing contention, detection canine threshold (i.e., sensitivity or limit of detection) training has primarily focused on changing the weight of the training aid substance used. There has been minimal focus on other principles, such as surface area, confinement, and temperature, which can be manipulated to affect odor availability. That said, trainers have been manipulating odor availability for years without necessarily understanding the governing scientific principles. The aim of this review is to highlight the principles that control odor availability of a substance and how an end user can apply these principles for operational detection canine training needs.

The odour of an unfamiliar stressed or relaxed person affects dogs' responses to a cognitive bias test

Dogs can discriminate stressed from non-stressed human odour samples, but the effect on their cognition is unstudied. Using a cognitive bias task, we tested how human odours affect dogs' likelihood of approaching a food bowl placed at three ambiguous locations ("near-positive", "middle" and "near-negative") between trained "positive" (rewarded) and "negative" (unrewarded) locations. Using odour samples collected from three unfamiliar volunteers during stressful and relaxing activities, we tested eighteen dogs under three conditions: no odour, stress odour and relaxed odour, with the order of test odours counterbalanced across dogs. When exposed to stress odour during session three, dogs were significantly less likely to approach a bowl placed at one of the three ambiguous locations (near-negative) compared to no odour, indicating possible risk-reduction behaviours in response to the smell of human stress. Dogs' learning of trained positive and negative locations improved with repeated testing and was significant between sessions two and three only when exposed to stress odour during session three, suggesting odour influenced learning. This is the first study to show that without visual or auditory cues, olfactory cues of human stress may affect dogs' cognition and learning, which, if true, could have important consequences for dog welfare and working performance.

Calibrating canines-a universal detector calibrant for detection dogs

Since the advent of the Universal Detector Calibrant (UDC) by scientists at Florida International University in 2013, this tool has gone largely unrecognized and under-utilized by canine scent detection practitioners. The UDC is a chemical that enables reliability testing of biological and instrumental detectors. Training a biological detector, such as a scent detection canine, to respond to a safe, non-target, and uncommon compound has significant advantages. For example, if used prior to a search, the UDC provides the handler with the ability to confirm the detection dog is ready to work without placing target odor on site (i.e., a positive control), thereby increasing handler confidence in their canine and providing documentation of credibility that can withstand legal scrutiny. This review describes the UDC, summarizes its role in canine detection science, and addresses applications for UDC within scent detection canine development, training, and testing.