The tail-elicited tail withdrawal reflex of Aplysia is mediated centrally at tail sensory-motor synapses and exhibits sensitization across multiple temporal domains

The defensive withdrawal reflexes of Aplysia californica have provided powerful behavioral systems for studying the cellular and molecular basis of memory formation. Among these reflexes the tail-elicited tail withdrawal reflex (T-TWR) has been especially useful. In vitro studies examining the monosynaptic circuit for the T-TWR, the tail sensory-motor (SN-MN) synapses, have identified the induction requirements and molecular basis of different temporal phases of synaptic facilitation that underlie sensitization in this system. They have also permitted more recent studies elucidating the role of synaptic and nuclear signaling during synaptic facilitation. Here we report the development of a novel, compartmentalized semi-intact T-TWR preparation that allows examination of the unique contributions of processing in the SN somatic compartment (the pleural ganglion) and the SN-MN synaptic compartment (the pedal ganglion) during the induction of sensitization. Using this preparation we find that the T-TWR is mediated entirely by central connections in the synaptic compartment. Moreover, the reflex is stably expressed for at least 24 h, and can be modified by tail shocks that induce sensitization across multiple temporal domains, as well as direct application of the modulatory neurotransmitter serotonin. This preparation now provides an experimentally powerful system in which to directly examine the unique and combined roles of synaptic and nuclear signaling in different temporal domains of memory formation.     

Near-term fetuses process temporal features of speech

The perception of speech and music requires processing of variations in spectra and amplitude over different time intervals. Near-term fetuses can discriminate acoustic features, such as frequencies and spectra, but whether they can process complex auditory streams, such as speech sequences and more specifically their temporal variations, fast or relatively slow acoustic variations, is unclear. We recorded the cardiac activity of 82 near-term fetuses (38 weeks GA) in quiet sleep during a silent control condition and four 15 s streams presented at 90 dB SPL Leq: two piano melodies with opposite contours, a natural Icelandic sentence and a chimera of the sentence--all its spectral information was replaced with broadband noise, leaving its specific temporal variations in amplitude intact without any phonological information. All stimuli elicited a heart rate deceleration. The response patterns to the melodies were the same and differed significantly from those observed with the Icelandic sentence and its chimera, which did not differ. The melodies elicited a monophasic heart rate deceleration, indicating a stimulus orienting reflex while the Icelandic and its chimera evoked a sustained lower magnitude response, indicating a sustained attentional response or more focused information processing. A conservative interpretation of the data is that near-term fetuses can perceive sound streams and the rapid temporal variations in amplitude that are specific to speech sounds with no spectral variations at all.     

General-purpose content

In this paper, I consider the objection, raised by Radu Bogdan, that a teleological theory of content is unable to ascribe content to a general-purpose, doxastic system. I begin by giving some attention to the notion of general-purpose representation, and suggest that this notion can best be understood as what I term "interest-independent" representation. I then outline Bogdan's objection in what I take to be its simplest form. I attempt to counter the objection by explaining how a teleologist might ascribe content in a particular case - the case of a perceptual judgement whose content is learned. I reject the idea that the teleologist can appeal to the way in which the subject has used the judgement, or its constituent concepts, in the past, on the grounds that it is possible for the subject to produce judgements and concepts that never help her to satisfy any of her interests. Instead, my account depends on the idea that the process of learning is regulated by a mechanism whose function is to produce a harmony between the information carried by perceptual judgements and the way in which they are used in inference.     

Effects of postidentification feedback on eyewitness identification and nonidentification confidence

Two experiments investigated new dimensions of the effect of confirming feedback on eyewitness identification confidence using target-absent and target-present lineups and (previously unused) unbiased witness instructions (i.e., "offender not present" option highlighted). In Experiment 1, participants viewed a crime video and were later asked to try to identify the thief from an 8-person target-absent photo array. Feedback inflated witness confidence for both mistaken identifications and correct lineup rejections. With target-present lineups in Experiment 2, feedback inflated confidence for correct and mistaken identifications and lineup rejections. Although feedback had no influence on the confidence-accuracy correlation, it produced clear overconfidence. Confidence inflation varied with the confidence measure reference point (i.e., retrospective vs. current confidence) and identification response latency.     

What are theories for? Concept use throughout the continuum of dinosaur expertise

Although it is now well established that object concepts are situated within broader systems of theoretical knowledge, it is less clear how theories influence the use of object concepts at various points throughout the continuum of expertise. Two studies were conducted to investigate the impact of specific theories (concerning dinosaurs) and overarching framework theories (of biology) on children's and adults' performance on categorization tasks involving familiar and less familiar concepts. Although expertise increased the quantity of deep feature knowledge possessed by children and increased their understanding of biologically adaptive relations among features, few aspects of children's performance generalized beyond highly familiar dinosaurs. Children's specific theories related to dinosaurs were empirically constrained and relatively dissociated from other types of biological knowledge. The interaction of specific concept knowledge with broader framework theories of biology throughout the continuum of expertise is considered.     

Generalization of deferred imitation during the first year of life

Infants first generalize across contexts and cues at 3 months of age in operant tasks but not until 12 months of age in imitation tasks. Three experiments using an imitation task examined whether infants younger than 12 months of age might generalize imitation if conditions were more like those in operant studies. Infants sat on a distinctive mat in a room in their home (the context) while an adult modeled actions on a hand puppet (the cue). When they were tested 24 h later, 6-month-olds generalized imitation when either the mat or the room (but not both) differed, whereas 9-month-olds generalized when both the mat and the room differed. In addition, 9-month-olds who imitated immediately also generalized to a novel test cue, whereas 6-month-olds did not. These results parallel results from operant studies and reveal that the similarity between the conditions of encoding and retrieval-not the type of task-determines whether infants generalize. The findings offer further evidence that memory development during infancy is a continuous function.     

Computer-Presented Video Prompting for Teaching Microwave Oven Use to Three Adults with Developmental Disabilities

We evaluated the use of a video prompting procedure for teaching three adults with developmental disabilities to make popcorn using a microwave oven. Training, using a 10-step task analysis, was conducted in the kitchen of the participant’s vocational training program. During baseline, participants were instructed to make popcorn, but were given no further instructions or prompts. Video prompting consisted of first watching a video clip of a step being performed and then giving participants the opportunity to imitate that step. This prompting procedure was introduced in a delayed multiple-probe across subjects design. Following acquisition, video prompting was removed and maintenance in the absence of video prompting was assessed at 2, 6, and 10 weeks. Two of the three participants acquired the task when video prompting was introduced and performed at 80–100% correct during follow-up sessions. These data suggest that video prompting may be an effective instructional strategy for teaching daily living skills to adults with developmental disabilities.     

Index

Other Index

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An analysis of response,direction, and place learning in an open field and T maze

Rats were trained to locate food in a response, direction, or place problem on an open field located at 2 positions. In Experiment 1, both the response and direction groups solved the problem. The place group failed to solve the task in approximately 300 trials. Experiment 2 demonstrated that rats need distinguishable start points to solve a place problem when neither a response nor a direction solution is available. Findings from Experiment 3 suggest that a combination of path traveled and distinct cues help to differentiate start points. Experiment 4 replicated the findings using a T maze. These results suggest "place" solutions are difficult for rats. The data are discussed with respect to conditional learning and modern spatial mapping theory.