Dissociable and Paradoxical Roles of Rat Medial and Lateral Orbitofrontal Cortex in Visual Serial Reversal Learning.

Much evidence suggests that reversal learning is mediated by cortico-striatal circuitries with the orbitofrontal cortex (OFC) playing a prominent role. The OFC is a functionally heterogeneous region, but potential differential roles of lateral (lOFC) and medial (mOFC) portions in visual reversal learning have yet to be determined. We investigated the effects of pharmacological inactivation of mOFC and lOFC on a deterministic serial visual reversal learning task for rats. For reference, we also targeted other areas previously implicated in reversal learning: prelimbic (PrL) and infralimbic (IL) prefrontal cortex, and basolateral amygdala (BLA). Inactivating mOFC and lOFC produced opposite effects; lOFC impairing, and mOFC improving, performance in the early, perseverative phase specifically. Additionally, mOFC inactivation enhanced negative feedback sensitivity, while lOFC inactivation diminished feedback sensitivity in general. mOFC and lOFC inactivation also affected novel visual discrimination learning differently; lOFC inactivation paradoxically improved learning, and mOFC inactivation had no effect. We also observed dissociable roles of the OFC and the IL/PrL. Whereas the OFC inactivation affected only perseveration, IL/PrL inactivation improved learning overall. BLA inactivation did not affect perseveration, but improved the late phase of reversal learning. These results support opponent roles of the rodent mOFC and lOFC in deterministic visual reversal learning.

Indicaciones y tratamiento de las fracturas periprotésicas de cadera / Periprosthetic hip fracture indications and treatment

periprotésicas femorales tras artroplastia de cadera con el objetivo de poder hacer recomendaciones terapéuticas según la localización, estabilidad del implante y reserva ósea. Material y métodos: ocurridas en nuestro Servicio entre los años 2.000 y 2.005 sistematizándolas según la clasificación de Vancouver. La causa más frecuente fueron los traumatismos de baja energía y el factor de riesgo más constante la presencia de osteopenia. Se encontraron 7 tipo AG, 3 tipo AL, 22 tipo B1, 12 tipo B2, 6 tipo B3 y 4 tipo C. Se realizó tratamiento ortopédico en todas las AG y algunas B1, revisión de la artroplastia en todas las AL, B2 y B3 y reducción abierta y síntesis en todas las C y algunas B1. Resultados: Se evidenció una alta tasa de complicaciones postquirúrgicas por lo que se insiste en su prevención mediante una cuidadosa técnica quirúrgica que evite las consecuencias catastróficas de estas fracturas

Objective: A review is presented of 54 femoral periprosthetic fractures following hip arthroplasty, with the purpose of defining treatment recommendations according to the location, stability of the implant, and bone reserve. Material and methods: A study was made of the periprosthetic fractures recorded in our Service between 2000-2005, with systematization according to the Vancouver classification. The most frequent cause of fracture was low-energy traumatism, while the most constant risk factor was the presence of osteopenia. We recorded 7 type AG, 3 type AL, 22 type B1, 12 type B2, 6 type B3 and 4 type C fractures. Orthopedic treatment was provided in all AG and in some B1 fractures, with arthroplasty revision surgery in all AL, B2 and B3 fractures, and open reduction and synthesis in all C and in some B1 fractures. Results: A high postoperative complications rate was observed. Emphasis is therefore placed on the need for prevention by applying a careful surgical technique to avoid the catastrophic consequences of these fractures