Learning enhances behaviorally relevant representations in apical dendrites

Learning alters cortical representations and improves perception. Apical tuft dendrites in Layer 1, which are unique in their connectivity and biophysical properties, may be a key site of learning-induced plasticity. We used both two-photon and SCAPE microscopy to longitudinally track tuft-wide calcium spikes in apical dendrites of Layer 5 pyramidal neurons as mice learned a tactile behavior. Mice were trained to discriminate two orthogonal directions of whisker stimulation. Reinforcement learning, but not repeated stimulus exposure, enhanced tuft selectivity for both directions equally, even though only one was associated with reward. Selective tufts emerged from initially unresponsive or low-selectivity populations. Animal movement and choice did not account for changes in stimulus selectivity. Enhanced selectivity persisted even after rewards were removed and animals ceased performing the task. We conclude that learning produces long-lasting realignment of apical dendrite tuft responses to behaviorally relevant dimensions of a task.

Blockade of β-Adrenergic Receptors by Propranolol Disrupts Reconsolidation of Drug Memory and Attenuates Heroin Seeking

Persistent traces of drug reward memories contribute to intense craving and often trigger relapse. A number of pharmacological interventions on drug-associated memories have shown significant benefits in relapse prevention at a preclinical level but their translational potential is limited due to deleterious side effects. Propranolol, a non-specific β-adrenergic receptors antagonist, is known for its ability to erase maladaptive memories associated with nicotine or cocaine in rodents and humans. However, little is known about its effect on reconsolidation of heroin memory and heroin seeking. In the present study, rats with a history of intravenous heroin self-administration received the propranolol treatment (10 mg/kg; i.p.) at different time windows with or without CS (conditioned stimulus) exposure. Our results showed that propranolol, when administered immediately after CS exposure but not 6 h later, can significantly attenuate cue-induced and drug-primed reinstatement of heroin seeking, suggesting that propranolol has the ability to disrupt heroin memory and reduce relapse. The propranolol treatment without retrieval of drug memory had no effect on subsequent reinstatement of heroin seeking, suggesting that its interfering effects are retrieval-dependent. Importantly, the effects of propranolol were long lasting as rats showed diminished drug seeking even 28 days after the treatment. Altogether, our study suggests that propranolol can interfere with reconsolidation of heroin memory and reduce subsequent drug seeking, making it an attractive therapeutic candidate for the treatment of opioid addiction and relapse prevention.

Vestibular attenuation to random-waveform galvanic vestibular stimulation during standing and treadmill walking

The ability to move and maintain posture is critically dependent on motion and orientation information provided by the vestibular system. When this system delivers noisy or erred information it can, in some cases, be attenuated through habituation. Here we investigate whether multiple mechanisms of attenuation act to decrease vestibular gain due to noise added using supra-threshold random-waveform galvanic vestibular stimulation (GVS). Forty-five participants completed one of three conditions. Each condition consisted of two 4-min standing periods with stimulation surrounding a 1-h period of either walking with stimulation, walking without stimulation, or sitting quietly. An instrumented treadmill recorded horizontal forces at the feet during standing and walking. We quantified response attenuation to GVS by comparing vestibular stimulus-horizontal force gain between conditions. First stimulus exposure caused an 18% decrease in gain during the first 40 s of standing. Attenuation recommenced only when subjects walked with stimulation, resulting in a 38% decrease in gain over 60 min that did not transfer to standing following walking. The disparity in attenuation dynamics and absent carry over between standing and walking suggests that two mechanisms of attenuation, one associated with first exposure to the stimulus and another that is task specific, may act to decrease vestibulomotor gain.

Training Novices to Discriminate Retinal Diseases Using Perceptual Learning

Perceptual learning refers to the enhanced ability of users to pick up information from a class of stimuli and is achieved through rapid, repeated stimulus exposure with feedback. Classifying optical coherence tomography images of age-related macular degeneration (AMD) scans as either the wet or dry subtype is an extremely difficult perceptual task that typically requires years of training. The purpose of this study was to develop techniques to quickly train users to classify AMD retinal scan images as wet or dry. To determine whether gamification techniques might aid perceptual learning, half of the participants received a gamified feedback during training while the other half received informational feedback only. Results demonstrated significant improvement in AMD image classification for both the gamified and non-gamified groups, even on retinal scans never encountered during training. Participants in the gamified group, however, had higher levels of intrinsic motivation for the task.

Meta-Analysis on Mediated Contact and Prejudice

This paper presents a meta-analysis of 79 cases (N = 21,857) testing the effectiveness of mediated intergroup contact on prejudice. Positive mediated contact decreased (r = −.23; 95% CI, −.29 to −.17), whereas negative mediated contact increased prejudicial attitudes (r = .31; 95% CI, .24 to .38) and intergroup anxiety and empathy were both significant mediators of these relationships. Furthermore, the data revealed no significant differences between parasocial and vicarious effects, positive and negative mediated-contact effects, or the effects of the duration of mediated-contact stimulus exposure on prejudice. However, the data did reveal experiments to have stronger effects than survey research. These and other results are discussed along with implications, limitations, and future research directions.

Exploring website gist through rapid serial visual presentation

Background Users can make judgments about web pages in a glance. Little research has explored what semantic information can be extracted from a web page within a single fixation or what mental representations users have of web pages, but the scene perception literature provides a framework for understanding how viewers can extract and represent diverse semantic information from scenes in a glance. The purpose of this research was (1) to explore whether semantic information about a web page could be extracted within a single fixation and (2) to explore the effects of size and resolution on extracting this information. Using a rapid serial visual presentation (RSVP) paradigm, Experiment 1 explored whether certain semantic categories of websites (i.e., news, search, shopping, and social networks/blogs) could be detected within a RSVP stream of web page stimuli. Natural scenes, which have been shown to be detectable within a single fixation in the literature, served as a baseline for comparison. Experiment 2 examined the effects of stimulus size and resolution on observers’ ability to detect the presence of website categories using similar methods. Results Findings from this research demonstrate that users have conceptual models of websites that allow detection of web pages from a fixation’s worth of stimulus exposure, when provided additional time for processing. For website categories other than search, detection performance decreased significantly when web elements were no longer discernible due to decreases in size and/or resolution. The implications of this research are that website conceptual models rely more on page elements and less on the spatial relationship between these elements. Conclusions Participants can detect websites accurately when they were displayed for less than a fixation and when the participants were allowed additional processing time. Subjective comments and stimulus onset asynchrony data suggested that participants likely relied on local features for the detection of website targets for several website categories. This notion was supported when the size and/or resolution of stimuli were decreased to the extent that web elements were indistinguishable. This demonstrates that schemas or conceptualizations of websites provided information sufficient to detect websites from approximately 140 ms of stimulus exposure.