Intrusion of stereotyped responding in pigeon spatial memory tasks

Pigeons appear predisposed to respond in stereotyped manners in multi-item spatial memory tasks in which the items are simultaneously presented. We discovered this when we attempted to study primacy and recency serial position effects using a delayed matching of key location task (Experiment 1) and when we attempted to develop a keypack analog of the radial-arm maze task (Experiment 4). In Experiment 1 matching accuracy for first-pecked sample was above chance, approximately chance for the second-pecked sample, and below chance for the third-pecked sample. Experiments 2 and 3 showed that the results of Experiment 1 were due to “superstitious” stereotyped responding: When pigeons were allowed to respond to two or three keys in any order and then respond to the same keys again, they responded in the same order on the second occasion. In Experiment 4, the pigeons successfully avoided pecking previously-pecked keys but did so by pecking the keys in a fixed sequence.     

Free-choice preference under uncertainty

Preferences in pigeons for free choice over forced choice under uncertain contingencies were compared with the one under certain contingencies in multiple concurrent-chain schedules of reinforcement. The uncertain condition examined the preference for two alternatives over one alternative when reinforcement probability at the end of the terminal link equalled 0.5, and with all keys in each terminal link lit green (two mixed fixed-interval extinction keys versus one mixed fixed-interval extinction key). Key and schedule arrangement in the certain condition was the same except that a peck on any terminal-link key after the FI interval always produced food. When naive pigeons were first exposed to uncertain contingencies, preference for two lit keys over one lit key was observed, and the preference was confirmed by sequential reversals of the terminal-link contingencies. However, no consistent preference was observed when uncertain condition followed the certain condition. Under certain contingencies, unlike the earlier experiments, very small and inconsistent preferences for free choice were demonstrated. A possible reason for the different preferences in the uncertain conditions was that pigeons may lessen their sensitivity to the circumstances with uncertainty by any history or carry-over effect of the prior contingency.     

Discriminative proprieties of Vary and Repeat contingencies

Pigeons were trained on an arbitrary matching-to-sample task in which Vary and Repeat contingencies served as sample stimuli. During the sample component, two keys were lit red and a four-peck sequence was reinforced if its frequency was less than a certain threshold (Vary sample) or if it comprised one of two target sequences (Repeat sample). During the comparison component, two keys were lit white and green, and correct choices depended on the previous sample contingency. Pigeons learned to emit high and low variability levels during the sample, and correct matching choices were obtained. In two discrimination testing phases, the requirement of variation (Vary sample) or of repetition (Repeat sample) was parametrically manipulated such that behavioral variability became undifferentiated between samples (low sample disparity) and then differentiated (high sample disparity) again. Accurate choices fell to chance under low sample disparity conditions, but improved under high disparity conditions. The results provide evidence that high and low variability levels can be produced in the absence of antecedent cues and that pigeons can accurately report whether they had experienced a Vary or a Repeat contingency, thus indicating that those contingencies may serve discriminative functions.     

Some characteristics of spatial associative memory in the pigeon, Columba livia

Willson and Wilkie (1993) developed a novel procedure to assess pigeons' memory for the spatial location of food. Only one of four locations provided food each daily session. Each location consisted of an illuminated pecking key and grain feeder. Over different days different locations, randomly selected, provided food during a 16-min session. The pigeons tended to revisit the location at which food was found on the previous day thereby demonstrating memory for food-spatial location associations over 24 h. Three experiments were conducted to further investigate this phenomenon. In Experiment 1 the session duration was varied between 4 and 32 min. Longer sessions had no detectable effect on their ability to remember the rewarded location 24 h later, a result that suggests that only brief encounters with food at a particular location are necessary for recall. In Experiment 2 the necessity of an active search for the day's rewarded location was removed; a 5-min period in which only the rewarded key was lit preceded the regular 16-min session. Pecks to the lit key in this 5-min period produced grain on the standard schedule. This manipulation facilitated the pigeons' discovery of food but did not affect their ability to remember the rewarded location, suggesting that the process of search and discovery is not essential to the associative memory process. In Experiment 3, food was available during the complete session (non-depleting condition) or was available only during the first half of the session (depleting condition). No detectable differences in the birds' memory of yesterday's profitable location were found. This suggests that non-depletion of food is not a necessary condition for day-to-day recall of food location. Taken together these findings enlarge our understanding of the spatial associative memory process.     

Some factors affecting pigeons' visual tracking behavior

A novel delayed conditional discrimination procedure was used successfully to investigate some factors affecting pigeons' tracking of visual stimuli. Trials began with the brief illumination of one of the keys (randomly selected) from the left- or right-hand column of a three by three matrix of pecking keys. Then the next key in the same row was briefly lit. Finally, the remaining key in the row was lit along with one (randomly chosen) of the remaining five keys from the left- or right-hand columns. A peck to the former but not the latter key was designated as correct and was rewarded. In Experiment 1 pigeons made correct choices on between 70 and 80 percent of trials, thereby demonstrating an ability to visually track objects. In Experiment 2 tracking accuracy was: a) reduced when either the first or second key in the sequence was omitted, b) improved when the sequence was repeated three times, c) reduced when duration of key illumination was reduced, and d) reduced by delays imposed between keys early but not late in the sequence. It was also found that tracking of vertical and horizontal sequences was approximately equal.     

Auditory Short-Term Memory Activation during Score Reading

Performing music on the basis of reading a score requires reading ahead of what is being played in order to anticipate the necessary actions to produce the notes. Score reading thus not only involves the decoding of a visual score and the comparison to the auditory feedback, but also short-term storage of the musical information due to the delay of the auditory feedback during reading ahead. This study investigates the mechanisms of encoding of musical information in short-term memory during such a complicated procedure. There were three parts in this study. First, professional musicians participated in an electroencephalographic (EEG) experiment to study the slow wave potentials during a time interval of short-term memory storage in a situation that requires cross-modal translation and short-term storage of visual material to be compared with delayed auditory material, as it is the case in music score reading. This delayed visual-to-auditory matching task was compared with delayed visual-visual and auditory-auditory matching tasks in terms of EEG topography and voltage amplitudes. Second, an additional behavioural experiment was performed to determine which type of distractor would be the most interfering with the score reading-like task. Third, the self-reported strategies of the participants were also analyzed. All three parts of this study point towards the same conclusion according to which during music score reading, the musician most likely first translates the visual score into an auditory cue, probably starting around 700 or 1300 ms, ready for storage and delayed comparison with the auditory feedback.     

短时记忆的神经网络模型

提出一个带有指针环路的短时记忆神经网络模型,模型包含两个神经网络,其中一个是与长时记忆共有的存贮内容表达网络,另一个为短时指针神经元环路,由于指针环路仅作为记忆内容的临时指针,因此,仅用很少的存贮单元即可完成各种短时记忆任务,计算机仿真证明,本模型确能表现出短时记忆的存贮容量有限和组块编码两个基本特征。     

Reconciling neuronal representations of schema,abstract task structure,and categorization under cognitive maps in the entorhinal-hippocampal-frontal circuits

Learning leads to a neuronal representation of acquired knowledge. This idea of knowledge representation was traditionally developed as a “cognitive map” of spatial memory represented in the hippocampus. The framework of cognitive mapping has been extended in the past decade to include not only spatial memory, but also non-spatial factual and temporal memory. Following this conceptual advancement, a line of recent neurophysiological research discovered such knowledge representations not only in the hippocampus, but also in the entorhinal cortex and frontal cortex. Although the distinct terms “cognitive map,” “schema,” “abstract task structure” or “categorization” were used in these studies, it is likely that these terms can be reconciled as a common mechanism of learned knowledge representations. Future experimental work will be required to differentiate the parametric nature of knowledge representations across brain areas.     

Integrating neuromorphic action-oriented perceptual inputs to generate a navigation behaviour for a robot

We use neural networks with pointer map architectures to provide simple attentional processing in a robotic task. A pointer map comprises a map of neurons that encode a stimulus. Besides global feedback inhibition, the map receives feedback excitation via a small group of pointer neurons that encode the location of a salient stimulus on the map as a vectorial representation. The pointer neurons are able to apply selective processing to a particular region of the network. The robot uses these properties to manoeuver in relation to an attended object. We implemented a controller composed of two pointer maps, and a motor map. The first pointer map reports the direction of a salient obstacle in a one-dimensional map of distance derived from infrared sensors. The second pointer map reports the direction to potential obstacles in a two-dimensional edge-enhanced image derived from a forward looking CCD-camera. These outputs are applied to a motor map, where they bias the motor control signals issued to the robots wheels, according to navigational intentions.     

Relative numerosity discrimination in the pigeon: further tests of the linear-exponential-ratio model

This study tested a model of how animals discriminate the relative numerosity of stimuli in successive or sequential presentation tasks. In a discrete-trials procedure, pigeons were shown one light for nf times and then another for nl times. Next they received food for choosing the light that had occurred the least-number of times during the sample. At issue were (a) how performance varies with the interval between the two stimulus sets (the interblock interval) and the interval between the end of the sample and the beginning of the choice period (the retention interval); and (b) whether a simple mathematical model of the discrimination process could account for the data. The model assumed that the influence of a stimulus on choice increases linearly when the stimulus is presented, but decays exponentially when the stimulus is absent; choice probability is given by the ratio of the influence values of the two stimuli. The model also assumed that as the retention interval elapses there is an increasing probability that the ongoing discriminative process be disrupted and then the animal responds randomly. Results showed that increasing the interblock intervals reduced the probability of choosing the last stimulus of the sample as the least-frequent one. Increasing the retention interval reduced accuracy without inducing any stimulus bias. The model accounted well for the major trends in the data.     

组蛋白修饰调控植物对胁迫的记忆与警备抗性的研究进展

植物扎根土壤,面对不利的环境胁迫无法逃避。然而,植物已经进化出对环境胁迫的记忆(stress memory)与警备抗性(或防御警备defense priming)等机制适应环境。环境胁迫在短时间内无法改变植物的DNA碱基序列,因此表观遗传被认为是植物对环境胁迫产生记忆和产生防御警备的主要机制,而组蛋白修饰被认为是最重要的机制,为胁迫记忆提供了可能。本文综述了非生物和生物胁迫下植物分别以胁迫记忆和防御警备机制为主导的组蛋白修饰参与抵御不良环境的最新进展,并提出该研究领域存在的问题和今后研究的重点与方向。深入探究组蛋白修饰与植物适应环境胁迫的关系,可为提高植物抗性、植物表型塑造、器官再生和作物改良等方面提供理论和技术指导。     

“Reverse” sexual dichromatism in a Neotropical frog

Sexual dichromatism is widespread among animals, but examples of “reverse” sexual dichromatism, in which females are more brightly colored than males, are extremely rare. We discovered a unique case of reverse sexual dichromatism in the golden rocket frog (Anomaloglossus beebei), a diurnal Neotropical frog. Females are bright “golden” in color, and males are drab tan with brown pigmentation that darkens when they are calling. Here, we document this color variation with calibrated digital photography and further show that there is no evidence for sex‐specific habitat matching; both sexes live in the same well‐lit habitat on green bromeliad leaves. Our results suggest that color variation in this species is an intraspecific signal and provide an important exception to the general expectation that males are more visually conspicuous in species with conventional sex roles.     

Testing for episodic-like memory in rats in the absence of time of day cues: replication of Babb and Crystal

Two experiments were performed to look for evidence of episodic-like memory in rats. On each of a series of trials on an eight-arm radial maze, rats in two groups entered four open arms in Phase 1, with reward pellets on three arms and a favored reward (chocolate in Experiment 1 and cheese in Experiment 2) on the remaining arm. Phase 2 retention tests were given 30 min or 4 h after Phase 1, with all eight arms open. The four arms not entered in Phase 1 all contained reward pellets, and the three arms that contained pellets in Phase 1 were empty. In the replenish short group, the favored reward was replenished at the same location where it was found in Phase 1 at the 30 min retention interval but was absent (Experiment 1) or degraded (Experiment 2) at the 4 h retention interval. In the replenish long group, the favored reward was replenished at the 4 h retention interval but not at the 30 min retention interval. Over a number of daily trials that randomly mixed short and long delays, rats in both experiments learned to return earlier to the arm containing the favored reward at the retention interval when it was replenished than at the retention interval when it was absent or degraded. These results replicate earlier findings [Babb, S.J., Crystal, J.D., 2005, Discrimination of what, when, and where: implications for episodic-like memory in rats. Learn. Mot., 36, 177-189] and provide evidence of episodic-like memory in rats.     

Testosterone modulates performance on a spatial working memory task in male rats

Gonadal hormones have been shown to modulate memory retention in female rats. The current experiments examine the role of testicular hormones in modulating the performance of male rats on two spatial water maze tasks. In the first study, castrated and intact rats were trained on the visible platform and hidden platform versions of the Morris water maze task. Castration did not affect performance on either version of this reference memory task with castrated and intact rats demonstrating similar performance both during acquisition and on post-training probe trials. In the second experiment, castrated and intact rats were tested on a delayed-matching-to-place version of the water maze. Rats received a series of trial pairs in the maze with a hidden platform located in the same pool location on the exposure and retention trials of each pair; between pairs of trials, however, the platform was repositioned to a novel pool location. The interval between trials was either 10- or 60-min and memory retention, taken as the difference between the pathlengths on the exposure and retention trials, declined as the interval increased. Relative to intact males, castrated males demonstrated impaired working memory retention at 60-min but not at 10-min retention intervals. This interval-dependent impairment in working memory retention was reversed by physiologic levels of testosterone replacement. These findings indicate that castration does not significantly affect acquisition or probe trial performance on a classic reference memory task but does impair spatial working memory retention, an effect that is reversed by exogenous testosterone.     

Polymorphism C366G of gene <Emphasis Type="Italic">GRIN2B</Emphasis> and verbal episodic memory: No association with schizophrenia

The present study searched for associations between gene GRIN2B (glutamate receptor, ionotropic, N-methyl-D-aspartate, subunit 2B) and component processes of verbal episodic memory in schizophrenic patients. The Rey Auditory Verbal Learning Test (RAVLT) as a part of a large neuropsychological battery was administered to 302 patients with schizophrenic spectrum disorders (sample PI). Also, 285 patients (sample P2) and 243 healthy controls (sample C2) performed the “10 words” test that measures short-term memory. The GRIN2B rs7301328 (C366G) polymorphism was genotyped for each subject. There were no associations between the polymorphism and any measure of the RAVLT either in the whole PI sample or in a subsample of patients with a severe cognitive deficit. The GRIN2B influenced immediate recall and proactive interference in the “10 words” test in the control group: homozygotes CC recalled fewer words and showed a lower effect of proactive interference than carriers of other genotypes. The results suggest that the C366G polymorphism could influence verbal episodic memory in the general population, but this influence is absent in schizophrenic patients.     

Long-Term Recency in Anterograde Amnesia

Amnesia is usually described as an impairment of a long-term memory (LTM) despite an intact short-term memory (STM). The intact recency effect in amnesia had supported this view. Although dual-store models of memory have been challenged by single-store models based on interference theory, this had relatively little influence on our understanding and treatment of amnesia, perhaps because the debate has centred on experiments in the neurologically intact population. Here we tested a key prediction of single-store models for free recall in amnesia: that people with amnesia will exhibit a memory advantage for the most recent items even when all items are stored in and retrieved from LTM, an effect called long-term recency. People with amnesia and matched controls studied, and then free-recalled, word lists with a distractor task following each word, including the last (continual distractor task, CDFR). This condition was compared to an Immediate Free Recall (IFR, no distractors) and a Delayed Free Recall (DFR, end-of-list distractor only) condition. People with amnesia demonstrated the full long-term recency pattern: the recency effect was attenuated in DFR and returned in CDFR. The advantage of recency over midlist items in CDFR was comparable to that of controls, confirming a key prediction of single-store models. Memory deficits appeared only after the first word recalled in each list, suggesting the impairment in amnesia may emerge only as the participant’s recall sequence develops, perhaps due to increased susceptibility to output interference. Our findings suggest that interference mechanisms are preserved in amnesia despite the overall impairment to LTM, and challenge strict dual-store models of memory and their dominance in explaining amnesia. We discuss the implication of our findings for rehabilitation.     

TIMA Part 2. TIMA-based instructive evolution of macromolecules and organs and structures

In extending a previous paper (TIMA Part 1, Wassermann, 1982) “template induced molecular assembly” (TIMA) is being further explored. It is suggested that TIMA could first have evolved proteins without coevolution of mRNA-like systems, in the absence of tRNAs. Some of these early proteins could, by self-assembly, have built up ribosomes. Ribosomes jointly with amino acids could have served as assembly templates for the TIMA-based evolution of tRNAs. Once tRNAs had evolved, TIMA could have participated, via a modified Mekler (1967) mechanism, in the evolution of new proteins and the coevolution of corresponding mRNA-like strands. TIMA also requires gene duplications and/or random mutations of DNA, to produce partial matching by duplicated and/or randomized DNA sequences of TIMA-generated cDNA which is complementary to the mRNA-like strands. The cDNA could then become incorporated by crossover into the position of the partially matching DNA sequences of, say, duplicate genes in genomes of germ-line cells. Since one requires only partial matching between duplicate (and/or randomly generated) DNA and non-randomly, TIMA-generated cDNA, TIMA theory avoids the need to assume (as in the Baldwin effect) that complete genes were randomly evolved. While rejecting crude Lamarckism, TIMA equally avoids the assumption that genes evolved only by combined random events, gene duplications, and adaptive selection. The resulting theory explains typical pseudo-exogenous adaptations via TIMA. Darwinian selection—now in the guise of “molecular selection” (and favourable environmental adaptive selection where present)—combined with TIMA could account for Waddington's “genetic assimilation”, thereby conceding Lamarck's notion that the environment can help to model heredity (while rejecting crude Lamarckism).     

Periodic majority recoding and reverberatory memory

A scheme involving periodic recoding of the memory trace of a single informational bit of memory, based upon the “voting” of neural channels at the recoding station, is shown to be an efficient means of ensuring the short-term reliability of reverberatory memory. Some features of such a memory are discussed.     

Sleep Supports Memory of Odors in Adults but Not in Children

Sleep supports the consolidation of declarative memory in children and adults. However, it is unclear whether sleep improves odor memory in children as well as adults. Thirty healthy children (mean age of 10.6, ranging from 8–12 yrs.) and 30 healthy adults (mean age of 25.4, ranging from 20–30 yrs.) participated in an incidental odor recognition paradigm. While learning of 10 target odorants took place in the evening and retrieval (10 target and 10 distractor odorants) the next morning in the sleep groups (adults: n = 15, children: n = 15), the time schedule was vice versa in the wake groups (n = 15 each). During encoding, adults rated odors as being more familiar. After the retention interval, adult participants of the sleep group recognized odors better than adults in the wake group. While children in the wake group showed memory performance comparable to the adult wake group, the children sleep group performed worse than adult and children wake groups. Correlations between memory performance and familiarity ratings during encoding indicate that pre-experiences might be critical in determining whether sleep improves or worsens memory consolidation.