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At least 523 records · Page 29Linked to original sources
PubMed1990

Connectionist models of recognition memory: constraints imposed by learning and forgetting functions.

Multilayer connectionist models of memory based on the encoder model using the backpropagation learning rule are evaluated. The models are applied to standard recognition memory procedures in which items are studied sequentially and then tested for retention. Sequential learning in these models leads to 2 major problems. First, well-learned information is forgotten rapidly as new information is learned. Second, discrimination between studied items and new items either decreases or is nonmonotonic as a function of learning. To address these problems, manipulations of the network within the multilayer model and several variants of the multilayer model were examined, including a model with prelearned memory and a context model, but none solved the problems. The problems discussed provide limitations on connectionist models applied to human memory and in tasks where information to be learned is not all available during learning.

Attention↗
PubMed2006

Effector-related sequence learning in a bimanual-bisequential serial reaction time task.

In a bimanual-bisequential version of the serial reaction time (SRT) task participants performed two uncorrelated key-press sequences simultaneously, one with fingers of the left hand and the other with fingers of the right hand. Participants responded to location-based imperative stimuli. When two such stimuli appeared in each trial, the results suggest independent learning of the two sequences and the occurrence of intermanual transfer. Following extended practice in Experiment 2, transfer of acquired sequence knowledge was not complete. Also in Experiment 2, when only one stimulus appeared in each trial specifying the responses for both hands so that there was no basis for separate stimulus-stimulus or separate response-effect learning, independent sequence learning was again evident, but there was no intermanual transfer at all. These findings suggest the existence of two mechanisms of sequence learning, one hand-related stimulus-based and the other motor-based, with only the former allowing for intermanual transfer.

Adult↗
PubMed1993

Working memory in learning disability subgroups.

The purpose of this study was to investigate (a) the degree to which working memory differences between learning-disabled and nondisabled children reflect a specific or generalized deficit, and (b) whether limitations in the enhancement of learning-disabled student's working memory performance are attributable to process or storage functions. To this end, performances of reading-disabled, math-disabled, chronological age (CA)-matched, and achievement-matched children were compared on verbal and visual-spatial working memory measures under initial, gain, and maintenance conditions. The results indicated that: (a) learning-disabled subtypes were not differentiated by their performance on verbal and visual-spatial working memory measures; and (b) learning-disabled children's working memory performance was inferior to CA-matched and superior to achievement-matched counterparts across initial, gain, and maintenance conditions. The results suggest that learning-disabled children suffer generalized working memory deficits, possibly due to storage constraints in the executive system.

Attention↗
PubMed1999

Preschoolers' recognition of numerical equivalence: sequential sets.

The present study was designed to investigate whether 3- to 5-year-olds can recognize numerical equivalence for comparisons involving sequentially presented sets. The relation between accurate numerical-equivalence judgments and acquisition of the conventional counting system also was explored. The results indicate that children recognize numerical equivalence for static sets earlier than for sequential sets. Furthermore, memory for the number of sequentially presented objects emerges earlier than memory for the number of sequential events. Finally, conventional counting ability is linked to success on comparisons involving sequential sets but not on those involving static sets. The implications of these findings for models of nonverbal quantification are discussed.

Child Development↗
PubMed2006

Path information effects in visual and proprioceptive spatial learning.

Objects in an environment are often encountered sequentially during spatial learning, forming a path along which object locations are experienced. The present study investigated the effect of spatial information conveyed through the path in visual and proprioceptive learning of a room-sized spatial layout, exploring whether different modalities differentially depend on the integrity of the path. Learning object locations along a coherent path was compared with learning them in a spatially random manner. Path integrity had little effect on visual learning, whereas learning with the coherent path produced better memory performance than random order learning for proprioceptive learning. These results suggest that path information has differential effects in visual and proprioceptive spatial learning, perhaps due to a difference in the way one establishes a reference frame for representing relative locations of objects.

Adolescent↗
PubMed2006

Pigeons' memory for sequences of light flashes: reliance on temporal properties and evidence for delay interval/gap confusion.

In Experiment 1, pigeons were trained to discriminate between sequences of two and four light flashes (illumination of the feeder). Retention functions obtained with dark delays exhibited a choose-many bias at a 1-s delay and a choose-few bias at delays of 4 and 8s. Retention functions obtained with illuminated delays only displayed a slight choose-few bias. In Experiment 2, additional birds were trained with the same sample sequences. However, the intertrial interval was illuminated by the houselight for Group Light, and it was dark for Group Dark. The acquisition data suggested that multiple temporal features of the light flash sequences controlled choice responding. For both groups, the retention functions were similar to those obtained in Experiment 1. In Experiment 3, baseline training with a 1-s dark delay eliminated the choose-many bias, but a significant choose-few bias at extended dark delays was still observed. Pigeons discriminate light flash sequences by relying on temporal properties of the sequence rather than using an event switch to count flashes. The biased-forgetting effects obtained in these studies appear to be primarily due to confusion between the delay interval and the gap between light flashes.

Animals↗
PubMed2004

Bilateral lesion of the cerebellar-dentate nucleus impairs egocentric sequential learning but not egocentric navigation in the rat.

The involvement of the cerebellum in procedural learning is demonstrated in visuomotor-sequence tasks, as lesion of this area impedes the acquisition of new sequences. Likewise, the lateral cerebellum appears to be involved in the acquisition of new sequences, but not in the execution of learned sequences. In contrast, the dentate nucleus participates only in the execution of learned visuomotor sequences. In previous studies, disruption of the procedural elements of spatial navigation following cerebellar or dentate lesions has been reported. However, as praxic strategies (egocentric learning) are included in the procedural elements of the navigation, the participation of the cerebellar-dentate nucleus in egocentric procedural learning processes has not been evaluated. Therefore, using colchicine, bilateral lesions were made in the cerebellar-dentate nucleus of Sprague-Dawley rats, and these rats were given two tasks: egocentric-based motor sequence learning in the radial maze and egocentric navigation in the Morris water maze. The lesioned rats were unable to use the sequential information in the short term and showed delayed long-term acquisition, which was probably due to the inability to detect the sequence. No effects on the egocentric navigation task were observed. Our results indicate that the cerebellar-dentate nucleus is involved in the detection of egocentric sequential information but not in the use of this information in the navigation process. Further, they show differential involvement of the cerebellar-dentate nucleus in the execution of learned visuomotor sequences, as the dentate lesion disrupted the acquisition of new egocentric-motor-based sequences.

Analysis of Variance↗
PubMed1975

Hand preference in sequential and spatial discrimination tasks.

Hand preference in sensorimotor discrimination tasks was tested on 80 right handed subjects in four experiments. One set of experiments compared the abilities of the two hands to perform sequential tasks. The other set compared spatial abilities of the two hands. Within each set one experiment involved unimanual performance, and the other bimanual performance. The results showed that subjects performed better with their right hand on the bimanual sequential task, and better with their left hand on the bimanual spatial task. No hand preference was found in the unimanual tasks. The results are interpreted as reflecting the differential sensorimotor dominance of the left and right hemispheres for sequential and spatial tasks respectively.

Discrimination Learning↗
PubMedDate not supplied

Retardation of cognitive aging by life-long diet restriction: implications for genetic variance.

Long-term moderate dietary restriction (DR) has been reported to extend life spans, delay the onset and decrease the incidence of a broad spectrum of age-associated diseases; however, its effect on cognition is still unclear. Our previous results indicated that long-term DR failed to retard cognitive and psychomotor aging in the inbred strain, Fischer-344 rats. In the present experiment, an anti-aging effect of DR on various types of cognitive and sensorimotor behaviors was found in F1 hybrid Fischer-344 x Brown Norway (F-344xBN) rats, while no effect of DR was detected in the second parental inbred strain, Brown-Norway (BN) rats. These findings show that the lack of an effect of DR on cognitive aging, which was previously found in Fischer-344 rats, is not a universal phenomenon. Instead, the effect of DR may depend upon the genetic makeup of the animals. Thus, a more diverse genetic milieu, such as in hybrid rats, relative to inbred rats, may increase the susceptibility to an effect of DR on age-related cognitive decline.

Aging↗
PubMed2004

Sex-related differences in time estimation and the role of expectancy.

In this study, using auditory sequences, the authors designed an examination with three phases of stimulus-driven attention that is based on the possibility that involuntarily time shifts of attention are caused by nonunique stimulus properties. The purpose was to investigate whether attending and temporal expectancies are influenced by stimulus's properties and by sex. In each phase, an auditory stimulus train was presented, and the participant was asked to tap rhythmically in order to anticipate every fifth stimulus (or, in the third phase, the lack of it). The time between button pressing and stimulus onset was measured using a computer. Time estimation was accepted as a false response if the subject responded before 150 ms or 150 ms later from onset stimulus time. Error numbers were greater in Phase 3 and there was no significant difference between the male and female subjects for any of the phases when error numbers were compared. On the other hand, males pressed the button more accurately than females. Time estimation performance was affected by sex and expectancy-related motor responses are very important for time estimation.

Acoustic Stimulation↗
PubMed1990

The effect of increased incentive on free recall by learning-disabled and nondisabled children.

Immediate free recall by learning-disabled and nondisabled children was compared under two incentive conditions. Recall of the first few words of each list by disabled children and younger nondisabled children was lower than that by older nondisabled children, and receiving a monetary reward increased early list item recall by older disabled and nondisabled learners. These findings suggest that elaborative encoding processes, such as rehearsal, are impaired in younger disabled and nondisabled children and that receiving a reward increased elaborative encoding by older children. Similar recall of the last few list items by all groups suggests that attention and immediate memory are comparable in disabled and nondisabled children of different ages. Receiving a reward increased recall of the last few list items by younger disabled and nondisabled children, suggesting that a reward increased attention, immediate memory, or both, in these groups. Because receiving a reward increased recall equally in all groups, lower motivation did not appear to be responsible for the lower recall by younger nondisabled children and learning-disabled children.

Attention↗
PubMed2005

Stimulus similarity decrements in children's working memory span.

Two experiments investigated the impact of the relationship between processing and storage stimuli on the working memory span task performance of children aged 7 and 9 years of age. In Experiment 1, two types of span task were administered (sentence span and operation span), and participants were required to recall either the products of the processing task (sentence-final word, arithmetic total) or a word or digit unrelated to the processing task. Experiment 2 contrasted sentence span and operation span combined with storage of either words or digits, in tasks in which the item to be remembered was not a direct product of the processing task in either condition. In both experiments, memory span was significantly greater when the items to be recalled belonged to a different stimulus category from the material that was processed, so that in sentence span tasks, number recall was superior to word recall, and in operation span tasks, word recall was superior to number recall. Explanations of these findings in terms of similarity-based interference and response competition in working memory are discussed.

Age Factors↗
PubMed1995

Practitioner review: verbal working memory development and its disorders.

Working memory refers to the systems responsible for the temporary storage and manipulation of information during the performance of cognitive tasks. There is a good deal of evidence that verbal short-term memory functions as a working memory system. We review advances in our understanding of the nature and limitations of verbal short-term memory and the reasons for its development with age, and go on to consider the common association between impairments of verbal short-term memory and other impairments of cognitive development. We conclude by considering the relationship between short-term memory development and cognitive development.

Adolescent↗