Distinct roles of cortical and pallidal β and γ frequencies in hemiparkinsonian and dyskinetic rats.

Enhanced β band (βB) activity, which is suppressed by levodopa (LD) treatment, has been demonstrated within the basal ganglia (BG) of Parkinson's disease (PD) patients. However, some data suggest that Parkinsonian symptoms are not directly related to this brain frequency and therefore, its causative role remains questionable. A less explored phenomenon is the link between the γ band (γB) and PD phenomenology. Here, we monitored the development of the oscillatory activity during chronic LD depletion and LD treatment in Parkinsonian and levodopa-induced dyskinesia (LID) in rats. We found a significant and bilateral power increase in the high βB frequencies (20-30Hz) within the first 10days after 6-hydroxydopamine (6-OHDA) lesion, which was in accordance with a significant depletion of dopaminergic fibers in the striatum. We also observed a clear-cut γB increase during LD treatment. The development of LID was characterized by a slight increase in the cumulative power of βB accompanied by a large augmentation in the γB frequency (60-80Hz). This latter effect reached a plateau in the frontal cortex bilaterally and the left globus pallidus after the second week of LD treatment. Our data suggest that the βB parallels the emergence of Parkinsonian signs and can be taken as a predictive sign of DA depletion, matching TH-staining reduction. On the other hand, the γB is strictly correlated to the development of LID. LD treatment had an opposite effect on βB and γB, respectively.

Clinical and Breed Characteristics of Idiopathic Head Tremor Syndrome in 291 Dogs: A Retrospective Study.

Objective. To establish signalment and phenomenology of canine idiopathic head tremor syndrome (IHTS), an episodic head movement disorder of undetermined pathogenesis. Design. Retrospective case series. Animals. 291 dogs with IHTS diagnosed between 1999 and 2013. Procedures. Clinical information was obtained from an online community of veterinary information aggregation and exchange (Veterinary Information Network, 777 W Covell Boulevard, Davis, CA 95616) and conducted with their approval. Information on breed, sex, age of onset, tremor description, mentation during the event, effect of distractions and drugs, diagnostics, presence of other problems, and outcome was analyzed. Results. IHTS was found in 24 pure breeds. Bulldogs, Labrador Retrievers, Boxers, and Doberman Pinschers comprised 69%; mixed breeds comprised 17%. Average onset age was 29 months (range: 3 months to 12 years). First episode occurred before 48 months of age in 88%. Vertical (35%), horizontal (50%), and rotational (15%) movements were documented. Possible trigger events were found in 21%. Mentation was normal in 93%. Distractions abated the tremor in 87%. Most dogs did not respond to antiepileptic drugs. Conclusions and Clinical Relevance. This retrospective study documents IHTS in many breeds including Labrador Retrievers, Boxers, and mixed breeds.