Inactivation of the anterior cingulate reveals enhanced reliance on cortical networks for remote spatial memory retrieval after sequential memory processing.

One system consolidation model suggests that as time passes, ensembles of cortical neurons form strong connections to represent remote memories. In this model, the anterior cingulate cortex (ACC) serves as a cortical region that represents remote memories. However, there is debate as to whether remote spatial memories go through this systems consolidation process and come to rely on the ACC. The present experiment examined whether increasing the processing demand on the hippocampus, by sequential training on two spatial tasks, would more fully engage the ACC during retrieval of a remote spatial memory. In this scenario, inactivation of the ACC at a remote time point was hypothesized to produce a severe memory deficit if rats had been trained on two, sequential spatial tasks. Rats were trained on a water maze (WM) task only or a WM task followed by a radial arm maze task. A WM probe test was given recently or remotely to all rats. Prior to the probe test, rats received an injection of saline or muscimol into the ACC. A subtle deficit in probe performance was found at the remote time point in the group trained on only one spatial task and treated with muscimol. In the group trained on two spatial tasks and treated with muscimol, a subtle deficit in probe performance was noted at the recent time point and a substantial deficit in probe performance was observed at the remote time point. c-Fos labeling in the hippocampus revealed more labeling in the CA1 region in all remotely tested groups than recently tested groups. Findings suggest that spatial remote memories come to rely more fully on the ACC when hippocampal processing requirements are increased. Results also suggest continued involvement of the hippocampus in spatial memory retrieval along with a progressive strengthening of cortical connections as time progresses.

Isolation and identification of eight microsatellite loci in the Cherokee darter (Etheostoma scotti) and their variability in other members of the genera Etheostoma, Ammocrypta, and Percina.

The Cherokee darter Etheostoma scotti is a federally threatened fish endemic to the Etowah River system of northwest Georgia. In order to analyse the population structure and genetic diversity of this fish, eight tetranucleotide microsatellite genetic markers were developed. The marker set was applied to 13 additional darter species to test cross-species amplification and polymorphism. Successful amplification was obtained for all eight loci in each of the 13 other species of darters, with between seven and eight polymorphic loci per species.

Avian flight without visual reference: preflight spinning produces spatial disorientation.

INTRODUCTION: Birds regularly fly in conditions of reduced visibility where they cannot see the horizon, whereas human pilots under similar conditions are subject to spatial disorientation (SD) and must, therefore, rely on instruments to maintain safe flight. We surmised that pigeons whose eyes were covered and that were rotated in a centrifuge before flight might show signs of SD. METHODS: We built a small centrifuge ("ornifuge") that allowed us to spin a bird around the vertical axis of its head at 1 cps for a specified number of turns and then release it instantly through a trap bottom to fly free. We studied 67 cull racing pigeons once each under four conditions: 1) static with normal vision (Static-See, n = 13); 2) static with eyes covered (Static-Cover, n = 17); 3) spin with normal vision (Spin-See, n = 15); and 4) spin with eyes covered (Spin-Cover, n = 22). Flight behavior immediately on release was observed by the investigators and photographed to document the occurrence of initial hovering, direction of spontaneous rotation if any, and staggering after landing. Birds released with eye-covers flicked them off within a few moments. RESULTS: Both Static-See and Static-Cover birds flew normally. For Spin-See, most flew normally, but 27% hovered momentarily before flying away. Among Spin-Cover birds, abnormal flight was seen in 50% and 72% staggered after landing. DISCUSSION: Spinning in the ornifuge produced abnormal flight behavior in the majority of blind-folded birds. This may provide a model for examining certain aspects of SD experienced by pilots under instrument meteorological conditions and studying the mechanisms that make birds relatively resistant to SD.