Samuel G Ewing

Learn More
Deep brain stimulation of the ventral striatum is an effective treatment for a variety of treatment refractory psychiatric disorders yet the mechanism of action remains elusive. We examined how five days of stimulation affected rhythmic brain activity in freely moving rats in terms of oscillatory power within, and coherence between, selected limbic regions(More)
Although numerous studies have implicated stress in the pathophysiology of schizophrenia, less is known about how the effects of stress interact with genetic, developmental, and/or environmental determinants to promote disease progression. In particular, it has been proposed that in humans, stress exposure in adolescence could combine with a predisposition(More)
BACKGROUND Despite there being a relatively large number of methods papers which detail specifically the development of stimulation devices, only a small number of reports involve the application of these devices in freely moving animals. To date multiple preclinical neural stimulators have been designed and described but have failed to make an impact on(More)
A number of studies have implicated disruptions in prepulse inhibition (PPI) of the startle response in both schizophrenia patients and animal models of this disorder. These disruptions are believed to reflect deficits in sensorimotor gating and are ascribed to aberrant filtering of sensory inputs leading to sensory overload and enhanced "noise" in neural(More)
Existing antipsychotic drugs are most effective at treating the positive symptoms of schizophrenia but their relative efficacy is low and they are associated with considerable side effects. In this study deep brain stimulation of the ventral hippocampus was performed in a rodent model of schizophrenia (MAM-E17) in an attempt to alleviate one set of(More)
To effectively study the mechanisms by which deep brain stimulation (DBS) produces its therapeutic benefit and to evaluate new therapeutic indications, it is vital to administer DBS over an extended period of time in awake, freely behaving animals. To date multiple preclinical stimulators have been designed and described. However, these stimulators have(More)
This study explores the regions activated by deep brain stimulation of the mediodorsal thalamic nucleus through examination of immediate early genes as markers of neuronal activation. Stimulation was delivered unilaterally with constant current 100 μs duration pulses at a frequency of 130 Hz delivered at an amplitude of 200 μA for 3h. Brains were removed,(More)
We present a novel approach to the removal of artifacts generated by deep brain stimulation equipment in neural recordings. We show it is possible to free a recording of its stimulation artifacts by under-sampling the data with a scheme which does not include any of the unwanted artifacts; using cubic-spline interpolation to up-sample the resulting signal.(More)
Existing antipsychotic drugs are most effective in the treatment of the positive symptoms of schizophrenia. However, they are associated with considerable side effects and have relatively low efficacy. Diminished inhibitory control in the hippocampus has been suggested to lead to hyperactivation of the dopamine system thus underpinning the(More)
Deep brain stimulation (DBS) of several targets induces beneficial responses in approximately 60% of patients suffering from treatment-resistant depression (TRD). The remaining 40% indicate that these stimulation sites do not bear therapeutic relevance for all TRD patients and consequently DBS-targets should be selected according to individual symptom(More)