Coincident induction of long-term facilitation at sensory-motor synapses in Aplysia: presynaptic and postsynaptic factors

Induction of long-term synaptic changes at one synapse can facilitate the induction of long-term plasticity at another synapse. Here we show that if Aplysia sensory neuron (SN) somata and their remote motor neuron (MN) synapses are simultaneously exposed to serotonin (5HT) pulses, which at either site alone are insufficient to induce long-term facilitation (LTF), processes activated at these sites interact to induce LTF. Coincident induction of LTF requires: (1) that the synaptic pulse occurs within a brief temporal window of the somatic pulse and (2) that local protein synthesis occurs immediately at the synapse, followed by delayed protein synthesis at the soma. LTF at the SN-MN synapses can also be induced with cell-wide application of repeated pulses of 5HT. However, these two forms of LTF differ mechanistically: (1) coincident LTF requires protein synthesis in the postsynaptic motor neuron, whereas repeated 5HT LTF does not, and (2) repeated 5HT LTF is accompanied by intermediate-term (3 h) facilitation, whereas coincident LTF is not. Thus LTF expressed in the same temporal domain can result from different underlying mechanisms.     

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.     

PKA and PKC are required for long-term but not short-term in vivo operant memory in Aplysia

We investigated the involvement of PKA and PKC signaling in a negatively reinforced operant learning paradigm in Aplysia, learning that food is inedible (LFI). In vivo injection of PKA or PKC inhibitors blocked long-term LFI memory formation. Moreover, a persistent phase of PKA activity, although not PKC activity, was necessary for long-term memory. Surprisingly, neither PKA nor PKC activity was required for associative short-term LFI memory. Additionally, PKA and PKC were not required for the retrieval of short- or long-term memory (STM and LTM, respectively). These studies have identified key differences between the mechanisms underlying nonassociative sensitization, operant reward learning, and LFI memory in Aplysia.     

Eye movements, not hypercompatible mappings, are critical for eliminating the cost of task set reconfiguration

Residual switch costs are notoriously difficult to eliminate. Yet Hunt and Klein (2002) eliminated them in a task that required observers to alternate between 8 trials of prosaccades and 8 trials of antisaccades, as long as there was at least 1 sec between the task cue and the onset of the saccade target. It was proposed that the elimination of residual switch costs occurred because prosaccade responses are computed very rapidly. These so-calledhypercompatible responses bypass memory retrieval stages of the response process, thereby eliminating the source of residual switch costs. Here we tested this hypothesis by requiring observers to alternate between responding with the finger that was vibrated (another task that meets the criteria for hypercompatibility) and responding with the finger of the opposite hand. Residual switch costs were not eliminated, suggesting that their elimination in Hunt and Klein (2002) was due to special properties of the prosaccade—antisaccade task.     

A critical evaluation of software for experiment development in research and teaching

This paper compares several software packages that allow users to create new computer-run experiments, but do not require that users be able to program. Three dimensions are considered: package requirements, ease of learning, and power and flexibility.     

The evidence for interactionism in psychology : A critical analysis of the situation-response inventories

A great deal of the evidence for interactionism in personality psychology arose out of the situation-response (S-R) studies of which there are now over 30. This paper examines closely the evidence for traitism, situationism and interactionism that arises from these studies. Nearly all of the published studies are tabulated, reanalysed and detailed criticisms of the more influential papers are offered. Serious problems are apparent in the methodology and analyses of these studies as well as in the conclusions drawn from them. It is argued that these studies have brought as much confusion as clarity to an area of research bedevilled by both conceptual and methodological problems.     

Explaining the adult careers of dyslexic boys: Variations in critical skills for high-level jobs

Several hundred boys who were diagnosed as dyslexic (specifically reading disabled) in adolescence and who attended a private college preparatory school for dyslexics were followed up in adulthood. The occupations of these men, who were above average in both intelligence and socioeconomic background, were compared to those of both a control group and the general white male population. As hypothesized, the dyslexic men had higher level jobs than the average man but they were much less likely than the controls to become professionals. They rarely entered jobs such as physician, lawyer, or college teacher which require higher degrees; instead most became managers or salesmen. The occupational differences between the dyslexic and control men were related to, but not completely accounted for, by their large differences in educational attainment. Data on the competencies rated as critical to good job performance in different occupations were consistent with the hypothesis that dyslexic men would establish themselves in relatively high-level jobs emphasizing nonacademic rather than academic on-the-job skills. Nondisabled professionals rated getting information through reading among the most critical of the skills required on their jobs. In contrast, managers and salesmen rated reading as less important than nonacademic competencies such as taking initiative and responsibility or being persuasive. The results illustrate the value of knowing more about the particular competencies required in different jobs in order to help members of special groups, particularly those such as dyslexies who have specific and enduring handicaps but who are otherwise intellectually normal.     

A critical reappraisal of the evidence for unconscious abstraction of deterministic rules in complex experimental situations

In a recent experiment (Lewicki et al., 1988) subjects were submitted to a four-choice RT paradigm for 3600 trials. On each of the successive logical blocks of five trials, the first two locations of the target were randomly distributed, and the last three locations were determined by complex rules. Although subjects were unable to verbalize the actual nature of the manipulation, performance on the last trials of each block improved at a faster rate and was better overall than performance on the first trials. In addition, subsequent rules changes on 480 additional trials only affected performance on the last three trials of each block. The present paper demonstrates that contrary to Lewicki et al's assertions this performance pattern requires neither acquisition of tacit knowledge of the composition rules, nor partitioning by the subjects of the sequence into logical blocks of five trials. Rather, the results can be accounted for by the relative frequency of a few simple sequences of target locations. Moreover, this alternative explanation alone correctly anticipates some striking features of fine-grained performance (Lewicki et al., 1988). The discussion focuses on methodological implications of these findings for investigation of unconscious learning, and speculates on what and how people learn when they encounter a complex and structured situation.     

Two critical periods of protein and glycoprotein synthesis in memory consolidation for visual categorization learning in chicks

A protein synthesis inhibitor, anisomycin (ANI), and an inhibitor of glycoprotein synthesis, 2-deoxygalactose (2-D-gal), were used to investigate memory consolidation following visual categorization training in 2-day-old chicks. ANI (0.6 micromole/chick) and 2-D-gal (40 micromoles/chick) were injected intracerebrally at different time intervals from 1 hr before to 23 hr after the training. Retention was tested 24 hr post-training. Both ANI and 2-D-gal injections revealed two periods of memory sensitivity to pharmacological intervention. ANI impaired retention when injected from 5 min before to 30 min after the training or from 4 hr to 5 hr post-training, thus demonstrating that consolidation of long-term memory in this task requires two periods of protein synthesis. 2-D-Gal first produced an amnesia when it was injected in the interval from 5 min before to 5 min after the training. Injections made between 5 min and 5 hr post-training were without effect on the retention. The second period of memory impairment by 2-D-gal started at 5 hr post-training and lasted until 21 hr after the training. Administration of 2-D-gal made 23 hr after the training did not influence retention in the test at either 24 hr or 26 hr. These results are consistent with the hypothesis that two waves of protein and glycoprotein synthesis are necessary for the formation of long-term memory. The prolonged duration of performance impairment by 2-D-gal in the present task might reflect an extended memory consolidation period for a categorization form of learning.     

Prevalence of dual diagnosis in an institution for individuals who are developmentally handicapped

The prevalence of dual diagnosis (developmental handicap with accompanying mental illness) was examined in a population of 71 persons who are institutionalized and developmentally handicapped. The Reiss Screen for Maladaptive Behavior (Reiss, 1988) revealed that 69% of the popula- tion had a dual diagnosis. The incidence of dual diagnosis was not related to level of functioning, although the type of psychopathology varied considerably across levels of functioning. In contrast to findings from the Reiss Screen, previous psychiatric diagnosis indicated a much lower rate of dual diagnosis (26.8%), as did current psychiatric assessment. There was little agreement between the two psychiatric assessments, or between the Reiss Screen and the psychiatric assessments. The Reiss Screen appears to provide information of more practical value for community placement decisions than is provided by the psychiatric assessments. Limitations to the concept of ?dual diagnosis’? for characterizing the mental health needs of persons with a developmental handicap are discussed.     

What friends are for! The use of routine standards in social comparison

Social comparisons are frequently used for self-evaluation. As a consequence, judges have to be efficient in each comparison step. Standard selection, however, is traditionally seen as an elaborate process in which judges deliberately select similar standards. We propose that often judges do not engage in such deliberate selection processes. Instead, they use routine standards--standards that have frequently been used for self-evaluation. Consistent with this assumption, Studies 1-3 demonstrate that student participants activate knowledge about their best friend--a likely routine standard--during self-evaluation. In Study 1, lexical decisions for the best friend's name are facilitated after self-evaluation. In Study 2, participants judge their best friend faster after evaluating themselves on the same dimension. In Study 3, this is even the case if the best friend is dissimilar and consequently undiagnostic. Finally, in Study 4, self-evaluations are primarily influenced by comparison information about an experimentally created routine standard.     

Detection of amplitude modulation and frequency modulation in tactual gratings: a critical bandwidth for active touch

Since most natural surfaces are complex and vary in amplitude and spatial frequency, it might be interesting to consider gratings not in the spatial domain, but in the spatial-frequency domain. Detection thresholds for amplitude modulation (AM) and frequency modulation (FM) in sinusoidal gratings were measured for seven participants. Participants moved their fingers actively across the gratings. Although the two types of modulation are quite different in the spatial domain, they have many features in common in the frequency domain. In previous research (Nefs et al 2001 Perception 30 1263-1274) we measured the discrimination thresholds for amplitude and frequency for sinusoidal gratings. We hypothesised then that these thresholds could be used to predict the discriminability of other types of gratings. In the present study, we did indeed find that the FM and AM detection thresholds can be understood quite well by these discrimination thresholds. The results indicate that the tactual system contains parallel psychophysical channels that filter and integrate the power of stimuli within critical bands. With these results, we are also able to calculate the critical bandwidth for active dynamic touch. We estimated the critical bandwidth surrounding the spatial frequency of 2 cycles cm(-1) to be about 125% of that spatial frequency. This value for the critical band for spatial frequency is incompatible with previous findings for temporal frequencies in vibrotactile research. This indicates that dynamic spatial-frequency discrimination is not likely to be done by temporal frequency.     

Perceptual asymmetries are preserved in memory for highly familiar faces of self and friend

We investigated the effect of familiarity on people's perception of facial likeness by asking participants to choose which of two mirror-symmetric chimeric images (made from the left or right half of a photograph of a face) looked more like an original image. In separate trials the participants made this judgment for their own face and for the face of a close friend; half of them matched to a true image of the original and half matched to a mirror image of the original. In the case of matching to a friend's face presented in the familiar orientation, over 80% of participants chose the left-left composite to be a better likeness to the original, whereas only 62% showed the same left-side bias when matching to a mirror image. The difference is significant, and the result contrasts markedly with a second experiment where participants who were unfamiliar with the faces showed comparable left-side biases when matching to true or mirror reversed images. The result suggests that perceptual asymmetries are retained in our long-term memory for highly familiar faces. While matching to images of self also showed an effect of familiarity, the data in this condition show less evidence of perceptual asymmetry and are discussed in relation to recent research on the representation of one's own face.     

Epigenetic alterations in the lateral amygdala are required for reconsolidation of a Pavlovian fear memory

Epigenetic mechanisms have been widely implicated in synaptic plasticity and in memory consolidation, yet little is known about the role of epigenetic mechanisms in memory reconsolidation processes. In the present study, we systematically examine the role of histone acetylation and DNA methylation in the reconsolidation of an amygdala-dependent Pavlovian fear memory. We first show that the acetylation of histone 3 (H3), but not histone 4 (H4), is regulated following auditory fear memory retrieval in the lateral nucleus of the amygdala (LA). We next show that histone deacetylase (HDAC) inhibition in the LA enhances both retrieval-induced histone acetylation and reconsolidation of an auditory fear memory. Conversely, inhibition of DNA methytransferase (DNMT) activity in the LA significantly impairs both retrieval-related H3 acetylation and fear memory reconsolidation. The effects of HDAC and DNMT inhibitors on fear memory reconsolidation were observed to be time-limited and were not evident in the absence of memory reactivation. Further, memories lost following DNMT inhibition were not observed to be vulnerable to spontaneous recovery, reinstatement, or to a shift in testing context, suggesting that memory impairment was not the result of facilitated extinction. Finally, pretreatment with the HDAC inhibitor was observed to rescue the reconsolidation deficit induced by the DNMT inhibitor. These findings collectively suggest that histone acetylation and DNA methylation are critical for reconsolidation of fear memories in the LA.     

Anomalies in the detection of change: When changes in sample size are mistaken for changes in proportions

Detecting changes, in performance, sales, markets, risks, social relations, or public opinions, constitutes an important adaptive function. In a sequential paradigm devised to investigate detection of change, every trial provides a sample of binary outcomes (e.g., correct vs. incorrect student responses). Participants have to decide whether the proportion of a focal feature (e.g., correct responses) in the population from which the sample is drawn has decreased, remained constant, or increased. Strong and persistent anomalies in change detection arise when changes in proportional quantities vary orthogonally to changes in absolute sample size. Proportional increases are readily detected and nonchanges are erroneously perceived as increases when absolute sample size increases. Conversely, decreasing sample size facilitates the correct detection of proportional decreases and the erroneous perception of nonchanges as decreases. These anomalies are however confined to experienced samples of elementary raw events from which proportions have to be inferred inductively. They disappear when sample proportions are described as percentages in a normalized probability format. To explain these challenging findings, it is essential to understand the inductive-learning constraints imposed on decisions from experience.     

Awareness of the false memory manipulation and false recall for people's names as critical lures in the Deese-Roediger-McDermott paradigm

In the present study, people's names were used as Critical Lures (central concept not on the lists) in the Deese-Roediger-McDermott (DRM) paradigm for studying false recall. Following Mukai, the transparency of false memory manipulation in the paradigm was manipulated to explore its influence on false recall. 80 volunteers (age range 17-30 years, M age = 20.9 yr., SD = 1.6) took part. Analyses showed that making the critical lure inconspicuous did not significantly increase false recall. However, the proportion of falsely recalled Critical Lures was significantly lower and the proportion of critical lures produced on a postrecall test (asking participants to report items that they had thought of but did not recall) was significantly higher when they spontaneously realized the nature of false memory manipulation. However, there was no effect on veridical recall of study items. These results suggest that participants strategically avoided reporting false recall for people's names as Critical Lures even without forewarning about false memory.     

Glutamate receptors in the medial geniculate nucleus are necessary for expression and extinction of conditioned fear in rats

Auditory fear conditioning requires anatomical projections from the medial geniculate nucleus (MGN) of the thalamus to the amygdala. Several lines of work indicate that the MGN is a critical sensory relay for auditory information during conditioning, but is not itself involved in the encoding of long-term fear memories. In the present experiments, we examined whether the MGN plays a similar role in the extinction of conditioned fear. Twenty-four hours after Pavlovian fear conditioning, rats received bilateral intra-thalamic infusions of either with NBQX (an AMPA receptor antagonist; Experiment 1) or MK-801 (an NMDA receptor antagonist; Experiment 1), anisomycin (a protein synthesis inhibitor; Experiment 2) or U0126 (a MEK inhibitor; Experiment 3) immediately prior to an extinction session in a novel context. The next day rats received a tone test in a drug-free state to assess their extinction memory; freezing served as an index of fear. Glutamate receptor antagonism prevented both the expression and extinction of conditioned fear. In contrast, neither anisomycin nor U0126 affected extinction. These results suggest that the MGN is a critical sensory relay for auditory information during extinction training, but is not itself a site of plasticity underlying the formation of the extinction memory.     

Thinking of critical words during study is unnecessary for false memory in the Deese,Roediger, and McDermott procedure

Do participants in the Deese, Roediger, and McDermott (DRM) procedure demonstrate false memory because they think of nonpresented critical words during study and confuse them with words that were actually presented? In two experiments, 160 participants studied eight visually presented DRM lists at a rate of 2 s or 5 s per word. Half of the participants rehearsed silently: the other half rehearsed overtly. Following study, the participants' memory for the lists was tested by recall or recognition. Typical false memory results were obtained for both memory measures. More important, two new results were observed. First, a large majority of the overt-rehearsal participants spontaneously rehearsed approximately half of the critical words during study. Second, critical-word rehearsal at study enhanced subsequent false recall, but it had no effect on false recognition or remember judgments for falsely recognized critical words. Thinking of critical words during study was unnecessary for producing false memory.