A pilot study testing a medication algorithm to reduce polypharmacy.

BACKGROUND: Polypharmacy is common in the treatment of persons with severe mental illness, yet it is not an evidence-based practice. To address this, an attempt was made to reduce medications for patients already receiving polypharmacy during an episode of acute psychiatric hospitalization. METHODS: A medication-reduction algorithm was developed , based on the best available evidence regarding indications for and efficacy of medications and principles of collaborative care. A feasibility pilot study was conducted using a matched case-control design for 12 patients treated with the algorithm and 12 patients treated as usual. RESULTS: The intervention patients were discharged on significantly fewer medications than controls; symptom reduction and length of stay did not differ significantly. CONCLUSION: A collaborative approach to reducing polypharmacy may reverse the trend to add medications during hospitalization.

Applicability of quadratic and threshold models to motion discrimination in the rabbit retina.

Computational and behavioral studies suggest that visual motion discrimination is based on quadratic nonlinearities. This raises the question of whether the behavior of motion sensitive neurons early in the visual system is actually quadratic. Theoretical studies show that mechanisms proposed for retinal directional selectivity do not behave quadratically at high stimulus contrast. However, for low contrast stimuli, models for these mechanisms may be grouped into three categories: purely quadratic, quadratic accompanied by a rectification, and models mediated by a high level threshold. We discriminated between these alternatives by analyzing the extracellular responses of ON-OFF directionally selective ganglion cells of the rabbit retina to drifting periodic gratings. The data show that purely-quadratic or high-threshold systems do not account for the behavior of these cells. However, their behavior is consistent with a rectified-quadratic model.

Response properties of cells in rabbit's lateral geniculate nucleus during reversible blockade of retinal on-center channel.

In the vertebrate retina, visual information is segregated into an on channel excited by light increment and a complementary off channel excited by light decrement. We used 2-amino-4-phosphonobutyric acid (APB), which selectively blocks the on channel in the retina (29), to determine the contributions of the on and off pathways to response properties of neurons in the lateral geniculate nucleus (LGN) of anesthetized, paralyzed rabbits. Visually evoked responses were recorded from 46 single cells in the LGN before, during, and after vitreal perfusion with 200-1,000 microM APB. APB reversibly blocked responses of on uniform-field cells and on center concentric-field cells to stationary, flashing spots of light. Responses to off uniform-field cells and off-center concentric-field cells were largely unaffected. APB did not differentially affect responses elicited from the receptive-field centers, as opposed to the surrounds, of on-center concentric-field cells. This finding suggests that these cells are driven exclusively by the on retinal channel and that the center-surround organization of their receptive fields does not result from a convergence of the on and off pathways. We studied a small number of cells that were selective for stimulus direction or motion. In each case, APB eliminated the cell's response to a moving light edge. The surviving response to a moving dark edge retained its original direction or motion preference, suggesting that these response properties do not depend critically on interactions between the on and the off pathways. The findings obtained in the rabbit are reminiscent of the results of similar investigations in the cat (10, 11) and the monkey (25). Taken together, they indicate that in the LGN of several vertebrate species there is a precise segregation vertebrate species there is a precise segregation of on and off information, at least for some functional classes of cells. The combination of on and off information does not seem to play a major role in establishing the response properties observed at this level in the visual system.