Hippocampal low-frequency stimulation and chronic mild stress similarly disrupt fear extinction memory in rats

Disruptions of fear extinction-related potentiation of synaptic efficacy in the connection between the hippocampus (HPC) and the medial prefrontal cortex (mPFC) have been shown to impair the recall of extinction memory. This study was undertaken to examine if chronic mild stress (CMS), which is known to alter induction of HPC–mPFC long-term potentiation, would also interfere with both extinction-related HPC–mPFC potentiation and extinction memory. Following fear conditioning (5 tone-shock pairings), rats were submitted to fear extinction (20 tone-alone presentations), which produced an increase in the amplitude of HPC–mPFC field potentials. HPC low-frequency stimulation (LFS), applied immediately after training, suppressed these changes and induced fear return during the retention test (5 tone-alone presentations). CMS, delivered before fear conditioning, did not interfere with fear extinction but blocked the development of extinction-related potentiation in the HPC–mPFC pathway and impaired the recall of extinction. These findings suggest that HPC LFS may provoke metaplastic changes in HPC outputs that may mimic alterations associated with a history of chronic stress.     

Audiovisual presentation demonstrates that selective adaptation in speech perception is purely auditory

MRC Institute of Hearing Research, University of Nottingham, Nottingham NG72RD, England Both auditory and phonetic processes have been implicated by previous results from selective adaptation experiments using speech stimuli. It has proved difficult to dissociate their individual contributions because the auditory and phonetic structure of conventional acoustical stimuli are mutually predictive. In the present experiment, the necessary dissociation was achieved by using an audiovisual adaptor consisting of an acoustical [b?] synchronized to a video recording of a talker uttering the syllable [g?]. This stimulus was generally identified as one of the dentals [d?] or [??]. It produced an adaptation effect, measured with an acoustical [b?-d?] test continuum, identical in size and direction to that produced by an acoustical [b?]—an adaptor sharing its acoustical structure—and opposite in direction to that produced by an acoustical [d?]—an adaptor sharing its perceived phonetic identity. Thus, the result strongly suggests that auditory rather than phonetic levels of processing are influenced in selective adaptation.     

A Bayesian formulation of behavioral control

Helplessness, a belief that the world is not subject to behavioral control, has long been central to our understanding of depression, and has influenced cognitive theories, animal models and behavioral treatments. However, despite its importance, there is no fully accepted definition of helplessness or behavioral control in psychology or psychiatry, and the formal treatments in engineering appear to capture only limited aspects of the intuitive concepts. Here, we formalize controllability in terms of characteristics of prior distributions over affectively charged environments. We explore the relevance of this notion of control to reinforcement learning methods of optimising behavior in such environments and consider how apparently maladaptive beliefs can result from normative inference processes. These results are discussed with reference to depression and animal models thereof.     

Erratum to: A Simple Method for Comparing Complex Models: Bayesian Model Comparison for Hierarchical Multinomial Processing Tree Models Using Warp-III Bridge Sampling

Psychometrika - The article A SIMPLE METHOD FOR COMPARING COMPLEX MODELS:     

Adult visual experience promotes recovery of primary visual cortex from long-term monocular deprivation

Prolonged visual deprivation from early childhood to maturity is believed to cause permanent visual impairment. However, there have been case reports of substantial improvement of binocular vision in human adults following lifelong visual impairment or deprivation. These observations, together with recent findings of adult ocular dominance plasticity in rodents, led us to re-examine whether adult primary visual cortex (V1) is capable of any recovery following long-term monocular deprivation starting in development. Using mice as a model, we find that monocular deprivation from early development to mature ages (well past the critical period) severely impaired binocular vision by reducing the amplitude of responses elicited by stimulation of the deprived eye. Surprisingly, we find little effect on nondeprived eye responses. Restoration of binocular vision in mature adults yields modest but significant improvement of visual responses in V1. Remarkably, we find that when binocular vision is followed by occlusion of the nondeprived eye, visual responses in V1 recover almost fully, as measured by visual evoked potential amplitude, spatial frequency threshold, and single-unit activity. We conclude that adult V1 can recover from long-term deprivation when provided with an optimal regimen of visual experience.