An electronic stimulus randomizer

A circuit is described which enables two stimuli to be presented in random sequence with either equal or different probabilities. The choice of stimuli is determined by sampling the condition of a two-state circuit. Experimental tests of randomness have been satisfactory.     

A system for behavioral evaluation of the visual capacities of cats

An automated testing apparatus for evaluating the visual capacities of cats is described. It features ease of training, reliability, and flexibility in the type of stimuli that can be presented. For presentation of complex visual stimuli, a closed circuit television display system has been devised that is compatible with the behavioral testing apparatus.     

Retrosplenial cortex lesion affected segregation of spatial information in place avoidance task in the rat

Retrosplenial cortex (RSC) together with the hippocampus is a component of the spatial memory circuit. To elucidate the role of the RSC in spatial memory formation in the immediate presence of both relevant and irrelevant spatial stimuli, we used a new place avoidance task, in which rats learn to avoid shock in an unmarked place. In the present study, we manipulated the relevance of distal "Room" stimuli and local "Arena" stimuli for place avoidance. Rats with ibotenate lesions of RSC, control sham lesions (Csl) and intact control rats (Cint) initially learned the (Room&Arena)+ task variant in which both Room and Arena stimuli are relevant for defining the shock sector. Afterwards, different subsets of rats from each group were trained in the following task variants: (i) Room+Arena-, in which the arena continuously rotated so that Room stimuli were relevant and Arena stimuli were irrelevant for avoiding shock; (ii) Arena+, in which the arena and shock sector rotated in a dark room so that Arena stimuli were relevant and Room stimuli were irrelevant for avoiding shock; (iii) Room+, in which the arena was covered in shallow water so that only Room stimuli were relevant for avoiding the shock sector whether the arena was stationary or rotating. We found that damage of RSC impaired the Room+Arena- variant that required relevant and irrelevant stimuli to be segregated. Importantly, the same lesions spared task variants that did not require segregation. Our results suggest an involvement of retrosplenial cortex in the segregation of spatial information.     

Apparent motion display

A control circuit is described which drives recurrently alternating projection tachistoscope shutters or lights for the study of apparent motion. The device, easily constructed, provides reliable variation in temporal duration of stimuli and the interval between their presentation.     

Peripheral vision monitor: Presenting displays at known positions in the visual periphery

The peripheral vision monitor is an inexpensive device that ensures that visual stimuli can be successfully projected to a given extrafoveal location. The apparatus extinguishes the display lighting system when the observer attempts to view a region intended to be viewed only in peripheral vision, reinstating the illumination when that region is again in the peripheral field. This is achieved by focusing a small spot of light on the scleral-corneal boundary of the observer’s eye and detecting the reflected light with a photocell and circuit. Illumination changes produced at the photocell are used to trigger the display lighting.     

An external millisecond timer for the Apple Macintosh with applications to cross-modal lexical priming

The circuit and program described in this report allow researchers to use Macintosh personal computers to conduct research that requires timing with millisecond accuracy. This is accomplished with external response keys and an external clock that sends characters through the Macintosh’s serial port. For researchers interested in cross-modal lexical priming tasks, a tachistoscopic slide shutter is incorporated to allow for accurately timed presentation of visual stimuli. Because the visual display and response keys are external to the computer, display and reaction times are not subject to the timing constraints inherent to the keyboard or the Macintosh Event Manager. All circuit diagrams and code are in the public domain.     

A programmable multiple-tone generator

A simple tone generator that allows software control of auditory stimuli is described. The circuit provides for the simultaneous generation, timing, and amplification of three different tones. Its low cost, ease of construction, and versatility make it an attractive alternative to conventional auditory stimulus hardware.     

An EEG coherence test of the frontal dorsal versus ventral hypothesis in N-back working memory

We examined Goldman-Rakic's conceptualization of working memory (WM) involving modality-specific reverbatory circuits using electrophysiological measures. An n-back WM task, with either spatial information or object information to be remembered, was administered with EEG coherence used to provide a functional measure of corticocortical communication. Support was not found for modality-specific WM systems in this task. Instead, results suggest that there is a circuit that connects dorsal frontal with dorsal parietal areas which is activated during all levels of the WM vigilance task, regardless of the type of stimuli involved. Data also suggest that left frontal areas are sensitive to the level of difficulty of the WM task (0,1,2, and 3-back), as well as familiarity of task demands. Overall, our results support a model that conceptualizes a unitary WM system rather than a system composed of separate WM circuits for different modalities.     

Simultaneous electronic recording of video and digital information on the video channel of a VTR or VCR

A technique is described that permits precise synchronization of video recorded behavior with discrete stimuli and responses. These discrete events are recorded as digital data on the video channel of a video recorder on a horizontal line that lies above the visible video information. These data may be observed in single-frame playback mode by underscanning the playback monitor. A circuit is described for computerized decoding of the digital data. Because each video field is uniquely coded, an updating of the data is possible 60 times each second. The described technique has several advantages over current approaches for synchronizing discrete stimulus and response events with video recorded behavior.     

Rehearsal in Spatial Working Memory: Evidence From Neuroimaging

A variety of biological evidence has identified a frontal-parietal circuit underlying spatial working memory for visual stimuli. But the question remains, how do these neural regions accomplish the goal of maintaining location information on-line? We tested the hypothesis that the active rehearsal of spatial information in working memory is accomplished by means of focal shifts of spatial selective attention to memorized locations. Spatial selective attention has been shown to cause changes in the early visual processing of stimuli that appear in attended locations. Thus, the hypothesis of attention-based rehearsal predicts similar modulations of visual processing at memorized locations. We used functional magnetic resonance imaging to observe posterior visual activations during the performance of a spatial working memory task. In line with the hypothesis, spatial rehearsal led to enhanced activation in the early visual areas contralateral to the memorized locations.     

Mechanisms of attention: a developmental study

A model of selective attention is proposed which contains a number of properties. First, stimuli which are irrelevant to the subjects' task can be analyzed to semantic levels automatically, and such stimuli can produce intrusion/interference effects. Second, two mechanisms by which selection is achieved are habituation to, and inhibition of, these irrelevant stimuli. A series of studies demonstrates that both the ability to process automatically irrelevant stimuli and the habituation mechanisms of attention are observable by Grade 2, whereas the inhibitory mechanism is not always evident at this stage. It is suggested that the greater distractability of children in certain situations may be due in part to the underutilization of this inhibitory mechanism. We further propose that children may be able to employ inhibitory mechanisms in more familiar perceptual-motor tasks.     

Sensitivity to reward and punishment in major depressive disorder: Effects of rumination and of single versus multiple experiences

In the current study, we examined the postulation that rumination makes it difficult for depressed individuals to learn the exact probability that different stimuli will be associated with punishment. To do so, we induced rumination or distraction in depressed and never-depressed participants and then measured punishment and reward sensitivity with a probabilistic selection task. In this task, participants first learn the probability that different stimuli will be associated with reward and punishment. During a subsequent test phase in which novel combinations of stimuli are presented, participants’ sensitivity to reward is tested by measuring their tendency to select the stimuli that were most highly rewarded during training, and their sensitivity to punishment is tested by measuring their tendency to not select the stimuli that were most highly punished during training. Compared with distraction, rumination led depressed participants to be less sensitive to the probability that stimuli will be associated with punishment and relatively less sensitive to punishment than reward. Never-depressed participants and depressed participants who were distracted from rumination were as sensitive to reward as they were to punishment. The effects of rumination on sensitivity to punishment may be a mechanism by which rumination can lead to maladaptive consequences.     

Extending a class of motion stimuli to study multiattribute texture perception

We present a class of stimuli that makes it possible to study the interaction of visual attributes in forming textural patterns. These stimuli are obtained in a simple manner from a class of motion stimuli that we described earlier (Papathomas & Gorea, 1988). The main advantages of the texture stimuli presented in this paper are: (1) each attribute can be arranged simultaneously with, but independently of, other attributes, (2) an arbitrary number of attributes can be used, (3) the interaction of attributes can be studied systematically, (4) direct comparison of two attributes is possible with stimuli in which the two are arranged to form competing patterns, and (5) because of the similarity to the motion stimuli, the relationship between texture and motion mechanisms can be investigated.     

Neural and molecular mechanisms of microcognition in Limax

Various non-mammalian model systems are being explored in the search for mechanisms of learning and memory storage of sufficient generality to contribute to the understanding of mammalian learning mechanisms. The terrestrial mollusk Limax maximus is one such model system in which mammalian-quality learning has been documented using odors as conditioned stimuli. The Limax odor information-processing circuits incorporate several system design features also found in mammalian odor-processing circuits, such as the use of cellular and network oscillations for making odor computations and the use of nitric oxide to control network oscillations. Learning and memory formation has been localized to a particular central circuit, the procerebral lobe, in which selective gene activation occurs through odor learning. Since the isolated Limax brain can perform odor learning in vitro, the circuits and synapses causally linked to learning and memory formation are assessable for further detailed analysis.     

The structure of equivalence classes

THE STRUCTURE OF EQUIVALENCE CLASSES CAN BE COMPLETELY DESCRIBED BY FOUR PARAMETERS: class size, number of nodes, the distribution of "singles" among nodes, and directionality of training. Class size refers to the number of stimuli in a class. Nodes are stimuli linked by training to at least two other stimuli. Singles are stimuli linked by training to only one other stimulus. The distribution of singles refers to the number of singles linked by training to each node. Directionality of training refers to the use of stimuli as samples and as comparison stimuli in training. These four parameters define the different ways in which the stimuli in a class can be organized, and thus provide a basis for systematically characterizing the properties of stimuli in a given equivalence class. The four parameters can also be used to account for the development of individual differences that are commonly characterized in terms of "understanding" and connotative meaning.Methods are described for generating all possible combinations of parameter values, and a formula is introduced which specifies all of the parameter values for an equivalence class. Its utility for interrelating experimental procedures is demonstrated by analyzing a number of representative experiments that have addressed equivalence-class formation.     

USING A CHOICE ASSESSMENT TO PREDICT REINFORCER EFFECTIVENESS

A choice assessment has been found to be a more accurate method of identifying preferences than is single-item presentation. However, it is not clear whether the effectiveness of reinforcement varies positively with the degree of preference (i.e., whether the relative preference based on the results of a choice assessment predicts relative reinforcer effectiveness). In the current study, we attempted to address this question by categorizing stimuli as high, middle, and low preference based on the results of a choice assessment, and then comparing the reinforcing effectiveness of these stimuli using a concurrent operants paradigm. High-preference stimuli consistently functioned as reinforcers for all 4 clients. Middle-preference stimuli functioned as reinforcers for 2 clients, but only when compared with low-preference stimuli. Low-preference stimuli did not function as reinforcers when compared to high- and middle-preference stimuli. These results suggest that a choice assessment can be used to predict the relative reinforcing value of various stimuli, which, in turn, may help to improve programs for clients with severe to profound disabilities.     

Differential Conditioning Based on a Difference in the Predictability of Reinforcement

A Pavlovian procedure containing a set of several alternative reliable trial stimuli and a set of several alternative unreliable trial stimuli was used to determine if reliability of outcome, per se, would differentially condition additional trial stimuli that either preceded or followed those original trial stimuli in a serial conditioning paradigm. The reinforcing effectiveness of the antecedent stimuli themselves was later tested in a higher-order conditioning design. It was found that different rates could be established to the different antecedent stimuli in the absence of a difference in the probability of reinforcement. Further, stimuli paired with those antecedent stimuli in the higher-order conditioning test also exhibited a difference in rate. It was concluded that a combination of a stimulus that is always followed by food and another that is never followed by food are, in net, a more effective reinforcer than a common stimulus that has the same overall probability of reinforcement but which is followed by both outcomes.     

Superordinate categorization via learned stimulus equivalence: quantity of reinforcement, hedonic value, and the nature of the mediator

Three experiments examined superordinate categorization via stimulus equivalence training in pigeons. Experiment 1 established superordinate categories by association with a common number of food pellet reinforcers, plus it established generalization to novel photographic stimuli. Experiment 2 documented generalization of choice responding from stimuli signaling different numbers of food pellets to stimuli signaling different delays to food reinforcement. Experiment 3 indicated that different numbers of food pellets did not substitute as discriminative stimuli for the photographic stimuli with which the food pellets had been paired. The collective results suggest that the effective mediator of superordinate categories that are established via learned stimulus equivalence is not likely to be an accurate representation of the reinforcer, neither is it likely to be a distinctive response that is made to the discriminative stimulus. Motivational or emotional mediation is a more likely account.     

The natural egocenter: An experimental account of locating the self

A lot of research suggests that people have an understanding of what they consider their ‘self’ and where it is located, namely near the head and upper torso. We assess whether these interpretations of the location of the self, which are based on subjective ratings, can be confirmed with an objective measure. Therefore, we used a paradigm in which neutral stimuli are associated with the self and a prioritization of the newly self-associated stimuli is interpreted as an integration of the stimuli into the self. Remarkably, only when the to-be-associated stimuli were presented close to the head and upper torso they were integrated and prioritized, but not when the stimuli were presented far away from these regions. The results indicate an influence of the distance between to-be-associated stimuli and the head/upper torso, thereby suggesting an implicit location of the self in this area, which does not depend on external beliefs.     

The psychodynamic of panic attacks: A useful integration of psychoanalysis and neuroscience1

This article tries to explain, in the light of some neuroscientific and psychoanalytical considerations, the repetitive pattern of panic attacks. Freud considered the panic attack as an ‘actual neurosis’ not involving any conflictual process. Recent neuroscientific findings indicate that psychosomatic reactions, set off by a danger situation, depend on the primitive circuit of fear (including the amygdala) characterised by its speed, but lack accurate responses and may also be activated by harmless stimuli perceived erroneously as dangerous. The traumatic terror is stored in implicit memory and may be set off by a conditioned stimulus linked to a previous danger situation. In the panic attack, the traumatic event is created by the imagination and this construction (a micro‐delusion), built in loneliness and anxiety, has the same power as the real trauma. A mutual psychosomatic short‐circuit between body and psyche, in which terror reinforces the somatic reactions and the psychic construction, is established. Therefore, it is important to highlight these constructions in order to analyse and transform them. In the second part of the article the author reviews the main psychoanalytical theories about panic attacks, stressing how, in his opinion, panic attack is a consequence of the breakdown of the defence organisation at various levels and may appear during periods of life crisis. Two patients suffering from a deficit of personal identity are presented. The various organisations and the different levels (biological, neuroscientific, associative, traumatic) of the panic attack determine different kinds of therapeutic approaches (pharmacological, cognitive and psychoanalytical). While the psychopharmacological treatment is aimed at reducing the neurovegetative reaction and the cognitive method is attempting to correct the associative and perceptive processes of fear signals, psychoanalytical therapy represents both a specific means to free patients from panic attacks as well as an indispensable route for their emotional growth.