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PubMed1997

Comparison of site specific injections into the basal forebrain on water maze and radial arm maze performance in the male rat after immunolesioning with 192 IgG saporin.

In this study we investigated the effects of 192 IgG saporin injections into the medial septal area (MSA), or nucleus basalis magnocellularis (NBM), and combined injections into the MSA and NBM, on the water maze and radial arm maze performance in the male rat. The results of the present study reveal a dissociation between the effects of 192 IgG saporin injections into the basal forebrain on the performance of two tasks of spatial learning in the rat. Bilateral injections of 192 IgG saporin into the NBM, MSA or combined MSA/NBM failed to disrupt water maze performance when compared to controls. In contrast, injections of 192 IgG saporin into the MSA, NBM or MSA/NBM induced mild impairments on a radial arm maze task. Overall, the disruption of spatial learning observed in this study however was relatively mild compared to deficits in spatial learning reported using less selective lesions of the cholinergic basal forebrain. Consequently, the results of this study suggest that a selective reduction in cholinergic transmission in the basal forebrain is by itself, insufficient to account for the functional impairments observed in spatial learning in the rat. Although our data does support the use of 192 IgG saporin as a selective cholinergic toxin in the basal forebrain, it further suggests that assessment of spatial learning in the rat following 192 IgG saporin lesions of the basal forebrain in combination with lesions to other neurotransmitter systems, may be a more viable approach to the elucidation of the neuropathological mechanisms that are associated with the cognitive deficits seen in Alzheimer's Disease.

Animals↗

PubMed1996

Comparison of site-specific injections into the basal forebrain on water maze and radial arm maze performance in the male rat after immunolesioning with 192 IgG saporin.

In this study, we investigated the effects of 192 IgG saporin injections into the medial septal area (MSA), or nucleus basalis magnocellularis (NBM), and combined injections into the MSA and NBM, on water maze and radial arm maze performance in the male rat. The results of the present study reveal a dissociation between the effects of 192 IgG saporin injections into the basal forebrain on the performance of two tasks of spatial learning in the rat. Bilateral injections of 192 IgG saporin into the NBM, MSA or combined MSA/NBM failed to disrupt water maze performance when compared to controls. In contrast, injections of 192 IgG saporin into the MSA, NBM or MSA/NBM induced mild impairments on a radial arm maze task. Overall, the disruption of spatial learning observed in this study was, however, relatively mild compared to deficits in spatial learning reported using less selective lesions of the cholinergic basal forebrain. Consequently, the results of this study suggest that a selective reduction in cholinergic transmission in the basal forebrain is, by itself, insufficient to account for the functional impairments observed in spatial learning in the rat. Although our data do support the use of 192 IgG saporin as a selective cholinergic toxin in the basal forebrain, they further suggests that assessment of spatial learning in the rat following 192 IgG saporin lesions of the basal forebrain in combination with lesions to other neurotransmitter systems, may be a more viable approach to the elucidation of the neuropathological mechanisms that are associated with the cognitive deficits seen in Alzheimer's disease.

Animals↗

PubMed1993

Spatial learning impairment parallels the magnitude of dorsal hippocampal lesions, but is hardly present following ventral lesions.

The hippocampus plays an essential role in spatial learning. To investigate whether the whole structure is equally important, we compared the effects of variously sized and localized hippocampal aspiration lesions on spatial learning in a Morris water maze. The volume of all hippocampal lesions was determined. Dorsal hippocampal lesions consistently impaired spatial learning more than equally large ventral lesions. The dorsal lesions had to be larger than 20% of the total hippocampal volume to prolong final escape latencies. The acquisition rate and precision on a probe test without platform were sensitive to even smaller dorsal lesions. The degree of impairment correlated with the lesion volume. In contrast, the lesions of the ventral half of the hippocampus spared both the rate and the precision of learning unless nearly all of the ventral half was removed. There was no significant effect of the location (dorsal or ventral) of damage to the overlying neocortex only. In conclusion, the dorsal half of the hippocampus appears more important for spatial learning than the ventral half. The spatial learning ability seems related to the amount of damaged dorsal hippocampal tissue, with a threshold at about 20% of the total hippocampal volume, under which normal learning can occur.

Animals↗

PubMed1999

Retrograde amnesia and selective damage to the hippocampal formation: memory for places and object discriminations.

Using a within-subjects design, rats were trained on two place-memory problems and five object-discrimination problems at different intervals prior to receiving either ibotenate lesions of the hippocampal formation or sham surgery. Places # 1 and 2 were fixed-platform water-maze tasks that were run in different rooms and they were learned during the 14th and 2nd week before surgery, respectively. Object-discrimination problems # 1-5 were learned during the 13th, 10th, 7th, 4th, and 1st week before surgery, respectively. Rats with hippocampal lesions displayed impaired retention of both Place problems with no evidence of a temporal gradient to the impairment. In contrast to their retrograde place-memory deficits, the hippocampal rats displayed normal retention of the five object-discriminations that were learned before surgery. Hippocampal lesions had similar consequences for anterograde learning, as the lesioned rats were impaired in acquisition of a new water-maze problem that was run in a third room (Place #3), whereas they showed normal acquisition of two new object-discriminations. The findings indicate that the hippocampal formation is not required for long-term consolidation of information underlying accurate performance of object-discriminations, and that its critical role in memory for places persists for at least 14 weeks, and probably for as long as those memories exist.

Amnesia, Retrograde↗

PubMed1983

Learning and memory in young and aged Fischer 344 rats.

Changes in learning and memory processes that occur with senescence were investigated in male and female Fischer 344 rats, 3-26 mth of age. Age-related impairments were seen in retention of inhibitory avoidance learning, acquisition of a Y-maze discrimination task, and in a swim escape task with short intertrial training intervals. In contrast, old animals performed better than the young rats in an active avoidance task. No age differences were observed in either open field activity or in flinch or jump thresholds to footshock. These results indicate that impairments in learning and memory processes of aged rats are task-specific, and that memory deficits in old rats are best seen following one-time-only events or with weak training. The behavioral baselines described will help in the design of further research to correlate memory and neurobiological changes observed during the aging process in the rat.

Aging↗

PubMed2006

Contributions of invariants, heuristics, and exemplars to the visual perception of relative mass.

Some potential contributions of invariants, heuristics, and exemplars to the perception of dynamic properties in the colliding balls task were explored. On each trial, an observer is asked to determine the heavier of 2 colliding balls. The invariant approach assumes that people can learn to detect complex visual patterns that reliably specify which ball is heavier. The heuristic approach assumes that observers only have access to simple motion cues. The exemplar-based approach assumes that people store particular exemplars of collisions in memory, which are later retrieved to perform the task. Mathematical models of these theories are contrasted in 2 experiments. Observers may use more than 1 strategy to determine relative mass. Although observers can learn to detect and use invariants, they may rely on either heuristics before the invariant has been learned or exemplars when memory demands and similarity relations allow.

Biomechanical Phenomena↗

PubMed2001

A proposed method for learning from textbooks in the primary grades: use of text structure to guide self-questioning.

A questioning strategy is proposed for teaching primary-level children about text organization or structure, such as cause-effect, comparison-contrast, and problem-solution. Once students can reliably identify different types of organization, they are taught to ask questions appropriate to each type to guide their learning. A cognitive-strategy instruction model is used as the vehicle for teaching children through modeling by a teacher, interactive discussion, and practice with corrective feedback. In addition, students are taught how to monitor the process, so responsibility is transferred from teacher to student. Some questions demand searching for answers in the text. Others are more complex, demanding integration of textual elements and use of personal knowledge for answering questions.

Child↗

PubMedDate not supplied

The effects of hippocampal-area parahippocampalis lesions on discrimination learning in the pigeon.

Three experiments examined the behavioural effects of bilateral ablation of the avian hippocampus-area parahippocampalis (Hp-APH), a region which is considered to be the homologue of the mammalian hippocampal formation. Pigeons with lesions of the Hp-APH were impaired in learning the reversal (but not the acquisition) of a position (left/right) discrimination (Expt. 1). In contrast, lesion birds were unimpaired relative to controls in both the acquisition and reversal of a visual (pattern) discrimination (Expt. 2) in terms of errors to criterion; there was evidence, however, that the pattern of responding differed between groups during reversal. Finally, Hp-APH pigeons were impaired in the acquisition of a conditional discrimination (Expt. 3). The results are compared with the effects of hippocampal ablation in mammals, and their implications for a behavioural homology between the avian Hp-APH and the mammalian hippocampal formation are considered.

Animals↗

PubMed1995

Comparison of executive and visuospatial memory function in Huntington's disease and dementia of Alzheimer type matched for degree of dementia.

Groups of patients with Hungington's disease and probable dementia of Alzheimer type (DAT) matched for level of dementia on the basis of mini mental state examination scores were compared in several tests of visual memory and tests sensitive to frontal lobe dysfunction. Whereas recall of patients with DAT tended to be worse on the Kendrick object learning test, the two groups were equivalent on tests of sensorimotor ability and delayed matching to sample performance. By contrast, the patients with Huntington's disease were significantly worse on tests of pattern and spatial recognition, simultaneous matching to sample, visuospatial paired associates, and on three tests sensitive to frontal lobe dysfunction--namely, the Tower of London test of planning, spatial working memory, and a visual discrimination learning and reversal paradigm. The impairments in these tests, however, did not always qualitatively resemble those seen in patients with frontal lobe damage and may be more characteristic of primary neostriatal deficit. In the visual discrimination paradigm the patients with Hungtington's disease were significantly worse than the patients with DAT at the simple reversal stage, where they displayed significant preservation to the previously rewarded alternative. The results are consistent with the hypothesis that patients with Huntington's disease exhibit deficits in tests sensitive to frontostriatal dysfunction and that this form of intellectual deterioration is qualitatively distinct from that seen in Alzheimer's disease.

Aged↗

PubMed1992

Learning to find the opponent: an ethological analysis of the behavior of paradise fish (Macropodus opercularis) in intra- and interspecific encounters.

In Experiment 1, 15 behavior patterns of male paradise fish (Macropodus opercularis; n = 72) toward a male conspecific, a male of another species, or no stimulus were recorded, both in home and novel situations. In Experiment 2, the same behaviors were recorded in a runway, and the same stimuli were used as reinforcers in the goal box (n = 18). A typical learning curve was seen when the subject found a male paradise fish in the goal box, learning was followed by apparent extinction when another species was found in the goal box, and few signs of learning were seen when the goal box was empty. Performance of the fish in both experiments can be accounted for by a strong aggressive motivation, a less strong but clear general curiosity, and habituation to the experimental procedure. In contrast to recent assertions in the literature, we conclude that aggressive behavior clearly can serve as a reinforcer in an instrumental learning situation.

Aggression↗

PubMed1986

Cognitive and learning profiles of delinquent and learning-disabled adolescents.

The association between juvenile delinquency and learning disabilities has been a focus of considerable discussion and controversy. Nevertheless, only a limited number of investigators have directly contrasted these two populations. In those studies which have examined the link between antisocial behavior and school problems, research methodology has varied, resulting in conflicting evidence and limited consensus. The present study was designed to address this issue by comparing the cognitive and learning profiles of delinquents and learning-disabled adolescents. Specifically, 53 delinquents, 26 learning-disabled adolescents, and 50 average achievers were evaluated with newly developed educational and cognitive inventories. These assessment techniques were used to analyze several functional areas including processing efficiency, problem solving, and response style. Application of discriminant analysis to the cognitive and educational profiles of these adolescents suggested the existence of various subtypes of delinquency. Learning disabilities characterized one of these subgroups. It was concluded that more specific descriptions of the learning profiles of adolescent delinquents holds promise for rehabilitation and, perhaps, prevention of juvenile delinquency.

Achievement↗

PubMed2005

Frequency effects in compound production.

Four experiments investigated the role of frequency information in compound production by independently varying the frequencies of the first and second constituent as well as the frequency of the compound itself. Pairs of Dutch noun-noun compounds were selected such that there was a maximal contrast for one frequency while matching the other two frequencies. In a position-response association task, participants first learned to associate a compound with a visually marked position on a computer screen. In the test phase, participants had to produce the associated compound in response to the appearance of the position mark, and we measured speech onset latencies. The compound production latencies varied significantly according to factorial contrasts in the frequencies of both constituting morphemes but not according to a factorial contrast in compound frequency, providing further evidence for decompositional models of speech production. In a stepwise regression analysis of the joint data of Experiments 1-4, however, compound frequency was a significant nonlinear predictor, with facilitation in the low-frequency range and a trend toward inhibition in the high-frequency range. Furthermore, a combination of structural measures of constituent frequencies and entropies explained significantly more variance than a strict decompositional model, including cumulative root frequency as the only measure of constituent frequency, suggesting a role for paradigmatic relations in the mental lexicon.

Humans↗

PubMed1978

Memory development in learning disabled children: evidence from nonverbal tasks.

The purpose of the present study was to test the developmental lag hypothesis with learning disabled children on two and three dimensional nonverbal task. Twenty-two learning disabled boys in two age groups of 11 each were tested on a probe memory recall procedure. In contrast to generalization of a developmental lag hypothesis, age-equivalent recall in primacy and recency positions reflected patterns similar to those of normal children. Further, a developmental analysis of nonverbal recall revealed constant age-related differences. Results suggested the developmental memory lag interpretation has been confounded with learning disabled children's generalized verbal deficits.

Child↗

PubMed1996

Discrimination learning decreases perceived similarity according to an objective measure.

UNLABELLED: Initial identification discriminations between two sizes and between two slants produced better overall performances on subsequent size and slant same-different discriminations, respectively. This size- and slant-specific transfer was due to an improvement on only the different pairs. Time-duration identification discriminations with the identical stimuli and response assignments improved neither overall same-different performances nor performances on different pairs. A good performance on different pairs relative to same pairs should indicate a low perceived similarity. The literature indicates that A-X and B-Y pairings produce a positive transfer on an A-versus-B discrimination when X and Y are relatively low in similarity, and also indicates that a low perceived (not physical) similarity improves discrimination learning. An increase in salience should have also improved performance on the same pairs. THE CONCLUSION: the initial discriminations decreased the perceived similarity of parts (size or slant). This decrease resembles perceptual contrast. A discrimination between two parts also seems to increase the extent to which each part is apprehended as a separate group. Therefore, the conclusion accords with the position that two groups are associated with contrast, including for visibility.

Adult↗

PubMed2005

[Forgetting : theories and potential mechanisms].

The cellular and molecular mechanisms of learning and memory are extremely complex and not well understood. The mechanisms of forgetting are even further more unclear, but several theories have been formulated to explain their cause and origin. Forgetting has recently been revealed to recruit specific mechanisms and anatomical basis which some components are distinct from those of learning and memory. Forgetting appears to depend essentially on protein phosphatases, enzymes highly abundant in the brain that are able to regulate numerous biochemical targets in neurons. The formation of memory by contrast depends on protein kinases. Memory and forgetting are indeed reciprocally controlled by a balance between kinases et phosphatases that determines the efficacy of learning and the persistence of memory. This review provides a brief account of the main features of forgetting and a summary of the most recent findings on its potential mechanisms.

Humans↗

PubMed1986

Differential use of temporal cues to the /s/-/z/ contrast by native and non-native speakers of English.

This study examined the effect of linguistic experience on perception of the English /s/-/z/ contrast in word-final position. The durations of the periodic ("vowel") and aperiodic ("fricative") portions of stimuli, ranging from peas to peace, were varied in a 5 X 5 factorial design. Forced-choice identification judgments were elicited from two groups of native speakers of American English differing in dialect, and from two groups each of native speakers of French, Swedish, and Finnish differing in English-language experience. The results suggested that the non-native subjects used cues established for the perception of phonetic contrasts in their native language to identify fricatives as /s/ or /z/. Lengthening vowel duration increased /z/ judgments in all eight subject groups, although the effect was smaller for native speakers of French than for native speakers of the other languages. Shortening fricative duration, on the other hand, significantly decreased /z/ judgments only by the English and French subjects. It did not influence voicing judgments by the Swedish and Finnish subjects, even those who had lived for a year or more in an English-speaking environment. These findings raise the question of whether adults who learn a foreign language can acquire the ability to integrate multiple acoustic cues to a phonetic contrast which does not exist in their native language.

Cues↗

PubMed2005

What can a neuron learn with spike-timing-dependent plasticity?

Spiking neurons are very flexible computational modules, which can implement with different values of their adjustable synaptic parameters an enormous variety of different transformations F from input spike trains to output spike trains. We examine in this letter the question to what extent a spiking neuron with biologically realistic models for dynamic synapses can be taught via spike-timing-dependent plasticity (STDP) to implement a given transformation F. We consider a supervised learning paradigm where during training, the output of the neuron is clamped to the target signal (teacher forcing). The well-known perceptron convergence theorem asserts the convergence of a simple supervised learning algorithm for drastically simplified neuron models (McCulloch-Pitts neurons). We show that in contrast to the perceptron convergence theorem, no theoretical guarantee can be given for the convergence of STDP with teacher forcing that holds for arbitrary input spike patterns. On the other hand, we prove that average case versions of the perceptron convergence theorem hold for STDP in the case of uncorrelated and correlated Poisson input spike trains and simple models for spiking neurons. For a wide class of cross-correlation functions of the input spike trains, the resulting necessary and sufficient condition can be formulated in terms of linear separability, analogously as the well-known condition of learnability by perceptrons. However, the linear separability criterion has to be applied here to the columns of the correlation matrix of the Poisson input. We demonstrate through extensive computer simulations that the theoretically predicted convergence of STDP with teacher forcing also holds for more realistic models for neurons, dynamic synapses, and more general input distributions. In addition, we show through computer simulations that these positive learning results hold not only for the common interpretation of STDP, where STDP changes the weights of synapses, but also for a more realistic interpretation suggested by experimental data where STDP modulates the initial release probability of dynamic synapses.

Action Potentials↗

PubMed2003

Phonological memory and vocabulary learning in children with focal lesions.

Eleven children with early focal lesions were compared with 70 age-matched controls to assess their performance in repeating non-words, in learning new words, and in immediate serial recall, a triad of abilities that are believed to share a dependence on serial ordering mechanisms (e.g.,; ). Results for the experimental group were also compared with other assessments previously reported for the same children by. The children with brain injury showed substantial impairment relative to controls in the experimental tasks, in contrast with relatively unimpaired performance on measures of vocabulary and non-verbal intelligence. The relationships between word learning, non-word repetition, and immediate serial recall were similar to those observed in several other populations. These results support previous reports that there are persistent processing impairments following early brain injury, despite developmental plasticity. They also suggest that word learning, non-word repetition, and immediate serial recall may be relatively demanding tasks, and that their relationship is a fundamental aspect of the cognitive system.

Adolescent↗