Wireless 'under the skull' epidural EEG and behavior in piglets during nitrous oxide or carbon dioxide gas euthanasia.

Consciousness is central to animal welfare concerns. Its assessment is most often conducted based on behavior, with a poor understanding of the correspondence between behavior and the neurobiological processes that underlie the subjective experience of consciousness. Recording of brain electrical activity using electrodes placed under the skull improves EEG recording by minimizing artifacts from muscular or cardiac activities, and it can now be combined with wireless recording in free-moving animals. This experiment investigated the correspondence between wireless 'under the skull' epidural EEG and the behavior of 18 five-week-old female piglets undergoing nitrous oxide (N2O) or carbon dioxide (CO2) gradual fill gas euthanasia at 25% replacement rate per minute of the chamber volume. Piglets exposed to CO2 had a peak in EEG total power ('Ptot') during the flailing stage, whereas piglets exposed to N2O had a higher EEG 95% spectral edge frequency ('F95') during their initial explorative behavior phase and a drop in EEG median frequency ('F50') after loss of posture. Loss of posture without righting attempt, as the last behavioral state observed during euthanasia, preceded the onset of transitional EEG on average by 0.9 and 3.1 min (for CO2 and N2O treatments, respectively), and the onset of isoelectric EEG by 4.5 and 6.2 min (for CO2 and N2O treatments, respectively). Paddling movements occurred shortly before and during transitional EEG but never during isoelectric EEG, whereas gasps persisted after the EEG had become isoelectric. The dynamics of EEG spectral changes were complex to interpret in relation to the degree of consciousness, but isoelectric EEG as an unequivocal indicator of unconsciousness appeared several minutes after loss of posture with no righting attempt. This leaves a window of uncertainty in regards to the potential for consciousness after loss of posture during gradual fill gas euthanasia in piglets.

Gentle abdominal stroking ('belly rubbing') of pigs by a human reduces EEG total power and increases EEG frequencies.

The neurobiological response to gentle touch remains poorly understood, especially in the context of human-animal interaction. A novel approach allowed recording the pig electroencephalogram (EEG) cranially epidurally and wirelessly during positive interactions with a human. Stroking of the pig's abdomen ('belly rubbing'), applied opportunistically, elicited a distinct behavioral response characterized by lateral recumbency, limb stretching, frequent short-lasting grunts and eye closure. Pigs varied in their responsiveness to belly rubbing but all pigs showed it. Their EEG was compared to EEG during human presence and other positive interactions except belly rubbing; isolation; and in the home pen as a baseline. Total EEG power ('Ptot') was lower during belly rubbing, whereas the median frequency ('F50', 5.3 ± 0.9 Hz vs. 3.8 ± 0.9 Hz for other contexts) and the 95% spectral edge frequency ('F95', 45.2 ± 3.2 Hz vs. 40.0 ± 3.2 Hz for other contexts) were higher during belly rubbing compared to other contexts. Lower EEG total power combined with a shift in spectral power distribution toward higher frequencies were linked to behavioral changes indicative of a positive welfare state during belly rubbing. The effects of belly rubbing on animal psychobiology and well-being warrant further research as a model of positive welfare state induced by touch.

Electrophysiological features in dogs with peripheral nerve sheath tumors: 51 cases (1993-2010).

OBJECTIVE: To determine the electrophysiological changes in dogs with peripheral nerve sheath tumors (PNSTs), evaluate the prevalence of these changes, assess the correlation between spontaneous activity in epaxial muscles and proximal invasion by the tumor, and evaluate whether knowledge of electrophysiological changes could be helpful in the imaging diagnosis via CT or MRI. DESIGN: Retrospective case series. ANIMALS: 51 dogs with a histologic (n = 18) or a suspected (33) diagnosis of PNST. PROCEDURES: Clinical, postmortem, and histologic reports and details of electrodiagnostic procedures and CT or MRI reports were studied. Twenty-four CT and 6 MRI reports for dogs with PNSTs were reviewed by a single observer blinded to the diagnosis. RESULTS: Only 2 of the 51 dogs had no electrophysiological changes. The most commonly affected muscles were those innervated by the radial, ulnar, median, tibial-sciatic, and peroneal nerves. Abnormal spontaneous epaxial muscle activity was significantly more frequent in the group with foraminal or spinal invasion by the tumors. Knowledge of the electrophysiological changes increased diagnostic accuracy of CT. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that electrophysiological studies may be sensitive for the detection of PNST and helpful in the imaging diagnosis. Epaxial electromyographic abnormalities appeared to be predictive for intervertebral or vertebral canal invasion by PNSTs in dogs.

Longitudinal ambulatory measurements of gait abnormality in dystrophin-deficient dogs.

BACKGROUND: This study aimed to measure the gait abnormalities in GRMD (Golden retriever muscular dystrophy) dogs during growth and disease progression using an ambulatory gait analyzer (3D-accelerometers) as a possible tool to assess the effects of a therapeutic intervention. METHODS: Six healthy and twelve GRMD dogs were evaluated twice monthly, from the age of two to nine months. The evolution of each gait variable previously shown to be modified in control and dystrophin-deficient adults was assessed using two-ways variance analysis (age, clinical status) with repeated measurements. A principal component analysis (PCA) was applied to perfect multivariate data interpretation. RESULTS: Speed, stride length, total power and force significantly already decreased (p<0.01) at the age of 2 months. The other gait variables (stride frequency, relative power distributions along the three axes) became modified at later stages. Using the PCA analysis, a global gait index taking into account the main gait variables was calculated, and was also consistent to detect the early changes in the GRMD gait patterns, as well as the progressive degradation of gait quality. CONCLUSION: The gait variables measured by the accelerometers were sensitive to early detect and follow the gait disorders and mirrored the heterogeneity of clinical presentations, giving sense to monitor gait in GRMD dogs during progression of the disease and pre-clinical therapeutic trials.