Browsing by Subject "radial arm maze"

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    Nicotine Use in Schizophrenia: a part of the cure or the disease?
    (2012-03-16) Berg, Sarah A.; Chambers, R. Andrew; Czachowski, Cristine L.; Grahame, Nicholas J.; Breier, Alan, 1953-
    Nicotine use among individuals with schizophrenia occurs at extremely high rates. The prevailing theory is that individuals with schizophrenia smoke as a form of self-medication to ameliorate sensory and cognitive deficits. However, these individuals also have enhanced rates of addiction to several drugs of abuse and may therefore smoke as a result of enhanced addiction liability. The experiments described herein explored these two hypotheses by assessing the effect that nicotine has on working memory, addiction vulnerability (locomotor sensitization and self-administration), and nicotinic acetylcholine receptor (nAChR) expression as well as the developmental expression of these characteristics in the neonatal ventral hippocampal (NVHL) neurodevelopmental animal model of schizophrenia. The results from these studies indicate that NVHLs had working memory impairments in both adolescence and adulthood, with nicotine having a negligible effect. Additionally, NVHLs displayed enhanced locomotor sensitization to nicotine which emerged in adulthood as well as an enhanced acquisition of nicotine self-administration, administering more nicotine overall. These behavioral differences cannot be attributed to nAChR expression as nicotine upregulated nAChR to a similar extent between NVHL and SHAM control animals. These data indicate that the enhanced rates of nicotine use among individuals with schizophrenia may occur as a result of an enhanced vulnerability to nicotine addiction.
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    Temporal Dynamics of Hippocampal and Medial Prefrontal Cortex Interactions During the Delay Period of a Working Memory-Guided Foraging Task
    (Oxford University Press, 2017-11-01) Myroshnychenko, Maxym; Seamans, Jeremy K.; Phillips, Anthony G.; Lapish, Christopher C.; Psychology, School of Science
    Abstract: Connections between the hippocampus (HC) and medial prefrontal cortex (mPFC) are critical for working memory; however, the precise contribution of this pathway is a matter of debate. One suggestion is that it may stabilize retrospective memories of recently encountered task-relevant information. Alternatively, it may be involved in encoding prospective memories, or the internal representation of future goals. To explore these possibilities, simultaneous extracellular recordings were made from mPFC and HC of rats performing the delayed spatial win-shift on a radial maze. Each trial consisted of a training-phase (when 4 randomly chosen arms were open) and test phase (all 8 arms were open but only previously blocked arms contained food) separated by a 60-s delay. Theta power was highest during the delay, and mPFC units were more likely to become entrained to hippocampal theta as the delay progressed. Training and test phase performance were accurately predicted by a linear classifier, and there was a transition in classification for training-phase to test-phase activity patterns throughout the delay on trials where the rats performed well. These data suggest that the HC and mPFC become more strongly synchronized as mPFC circuits preferentially shift from encoding retrospective to prospective information