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PubMed2000

Acquisition and transfer of new verbal information in amnesia: retrieval and neuroanatomical constraints.

Four experiments examined new associative learning in amnesia by contrasting the performance of 2 amnesic participants-1 (C.C.) with basal forebrain damage and the other (R.H.) with medial temporal lobe damage--and 3 controls. Both amnesic individuals were severely impaired on explicit memory measures but showed intact perceptual priming. On the new associations measures, only C.C., not R.H., exhibited learning by producing correct targets (HIJACKER) in the absence of perceptual cues for them (e.g., STAFF shot ???). When the perceptual cue (e.g., MEDICINE cured _I_C_P) was provided, both C.C. and R.H. showed learning. Transfer to information containing conceptually related targets (e.g., TERRORIST or BELCH) was reliably observed only in C.C. This finding was replicated with further reduction in perceptual overlap across original (LIGHTNING torched JUNGLE) and transfer (LIGHTNING burned WILDERNESS) sentences. Together, these findings delineate the role of experimental conditions, severity of amnesia, and different neuroanatomical structures in mediating new verbal learning in amnesia.

Adult↗
PubMed2004

Possible mechanism for transfer of motor skill learning: implication of the cerebellum.

Transfer of learning takes place whenever our previous knowledge and skills affect the way in which new knowledge and skills are learned. The magnitude of transfer may depend on how prior memory is retrieved so that it may be relevant and usable in the present in terms of internal representation. This review highlights the power of neuroimaging techniques such as positron emission tomography (PET) to identify the underlying neuronal system of intermanual transfer by showing the asymmetry in the system for the same motor skill between hands. The review focuses on cerebellar cross-activation, cerebellar activation contralateral to the active hand, which would contribute to intermanual transfer of monkey tool-use learning, together with the fronto-parietal cortical circuit. Finally, this article proposes the relationship between the cerebellum and the possible mechanism underlying non-specific transfer that allows thinking in a flexible and productive manner.

Animals↗
PubMed2005

Neural control of rhythmic sequences.

We investigated whether the temporal structure of movement sequences can be represented and learned independently of their ordinal structure, and whether some brain regions are particularly important for temporal sequence performance. Using a learning transfer design, we found evidence for independent temporal representations: learning a spatiotemporal sequence facilitated learning its temporal and ordinal structure alone; learning a temporal and an ordinal structure facilitated learning of a sequence where the two were coupled. Second, learning of temporal structures was found during reproduction of sequential stimuli with random ordinal structure, suggesting independent mechanisms for temporal learning. We then used functional magnetic resonance imaging to investigate the neural control of sequences during well-learned performance. The temporal and ordinal structures of the sequences were varied in a 2 x 2 factorial design. A dissociation was found between brain regions involved in ordinal and temporal control, the latter mainly involving the presupplementary motor area, the inferior frontal gyrus and precentral sulcus, and the superior temporal gyri. Finally, in a second fMRI experiment, well-learned temporal sequences were performed with the left or right index fingers, or using rhythmic speech. The overlap in brain activity during performance with the different effectors included a similar set of brain regions as that found in the first fMRI experiment: the supplementary motor area (SMA), the superior temporal gyrus, and the inferior frontal cortex. We thus suggest that this set of regions is important for abstract, movement-independent, temporal sequence control. This organization may be important for increased flexibility in voluntarily timed motor tasks.

Brain Mapping↗
PubMed1969

Alcohol and recall: state-dependent effects in man.

Male vollunteers performed four memory tasks either while sober or lunder effects of alcohol. Twenty-four hours later they were tested under the same or different conditions. In tasks measuiring recall and interference, learning transfer was better when the subject was intoxicated during both sessions than when he was intoxicated only during the learning session. In a task measuring recognition, transfer was not significantly affected by changing state. Thus, alcohol appears to produce "dissociated" or state-dependent effects in man, but not all forms of memory are equally sensitive to the phenomenon.

Alcoholic Intoxication↗
PubMed1985

Visual discrimination learning and interhemispheric transfer in the cat, as affected by 6-hydroxydopamine.

Learning and interhemispheric transfer of visual flux, pattern and form discriminations were studied in the cat after selected exposure of one suprasylvian cortex to 6-hydroxydopamine (6-OHDA). Biochemical assay using High Performance Liquid Chromatography (HPLC) two weeks after 6-OHDA revealed no discernible norepinephrine or dopamine in the treated cortex, but elevated concentrations of these transmitters in the cortex of the opposite hemisphere. Visual discriminations learned before treatment with 6-OHDA were retained at a high level using either the eye on the side of chemical lesion or the eye on the untreated side. An asymmetric deficit in learning new form discriminations was present, however, when the eye on the untreated side was used, in contrast to normal learning using the eye on the side of the hemisphere with depleted adrenergic nerve supply. Once learning was achieved using the lesioned hemisphere transfer of the engram was found to the untreated hemisphere. Thus, the unlesioned hemisphere was unable to learn normally using direct retinal input from the ipsilateral eye, but showed good capacity for learning using indirect visual input from the contralateral eye. This suggests a powerful influence of the callosum on the learning abilities of the two hemispheres, an influence proved by sectioning the callosum. Callosotomy resulted in a reversal of the discriminative capacities seen after 6-OHDA, i.e. the lesioned hemisphere was defective relative to the unlesioned hemisphere.

Animals↗
PubMed1993

Transfer of new learning in memory-impaired patients.

Previous research has produced conflicting evidence concerning transfer of new learning by amnesic patients. The present experiment investigated the hypothesis that different numbers of learning trials account for differences in transfer, such that the greater the number of repetitions of material in identical stimulus contexts the poorer the transfer. Six memory-impaired patients and six control subjects attempted to learn the names of business-related documents in response to descriptive definitions. Learning continued until one of the following criteria was reached: 50% correct, 100% correct, 100% correct plus 10 trials. In a transfer task, subjects were then asked to produce the target responses to altered definitional cues. The results of the experiment demonstrated that, contrary to prediction, transfer improved with numbers of learning trials. Results are consistent with the view that continued study of information allows better integration of new learning with prior knowledge and correspondingly higher levels of transfer. The theoretical implications of the findings are discussed in terms of the declarative/procedural and the episodic/semantic memory distinction. It is suggested that memory-impaired patients are capable of acquiring new semantic information although not at a normal rate. Implications for memory rehabilitation are also outlined.

Adult↗
PubMed2003

The role of sensory preconditioning in memory retrieval by preverbal infants.

Infants' memories are highly specific to their training stimuli; they rarely transfer learned responding. In two experiments, we asked whether sensory preconditioning facilitates the transfer of deferred imitation. In Experiments 1A and 1B, 6-month-olds were simultaneously preexposed to Puppets A and B and then saw target actions modeled on Puppet A. The infants associated the paired puppets and imitated the actions on Puppet B. In Experiment 2, the preexposure procedure was repeated, but the actions were modeled on Puppet A with a toy train in view. The infants also associated Puppet A and the train: Either object effectively reactivated both forgotten memories; thereafter, the infants again imitated the actions on Puppet B. These findings reveal that infants form specific and enduring associations between stimuli they have merely seen together. These associations facilitate the transfer of deferred imitation, both directly and indirectly, through connections to other associations.

Age Factors↗
PubMed1982

Learning, memory, and transfer in profoundly, severely, and moderately mentally retarded persons.

Discrimination learning, memory, and transfer capacity were assessed in representative samples of institutionalized retarded persons in order to provide information on trainability. The 56 subjects were selected from moderately, severely, and two levels of profoundly retarded adults. They learned and relearned three successive two-choice discrimination problems. Generally, the higher functioning subjects, defined by IQ and adaptive behavior learned more rapidly than did the lower functioning subjects. Forgetting was related to IQ/adaptive behavior level. Interproblem transfer was negligible at all levels of retardation, but ceiling effects may have obscured positive transfer in the higher functioning groups. Backward learning curves revealed large differences between lower and higher functioning persons in the presolution trials, but once learning began even profoundly retarded subjects solved these problems as rapidly as did the moderately retarded subjects. Ten of the 56 subjects failed to learn all three problems.

Adult↗
PubMed1998

A temporal intermediate stimulus problem.

Pigeons discriminated the serial position of a target duration among a sequence of 3 stimulus durations; the specific duration sequences changed across trials. In different conditions, the target duration was the shortest, intermediate, or longest duration in the sequence. Conditions involved a series of transitions in which new duration sequences were added to the stimulus set, providing an assessment of transfer. Pigeons learned and transferred the discrimination when the target was the shortest or longest duration. When, however, the target was the intermediate duration, the birds had great difficulty learning the task and exhibited little transfer to novel sequences. These findings are similar to those observed with nontemporal stimuli in a classic discrimination task, the intermediate stimulus problem. They provide an extension of work on relational timing to a more complex situation.

Animals↗
PubMed1987

Effects of selective lesions of fimbria-fornix on learning set in the rat.

The effects of selective partial lesions of the Fimbria-Fornix (FiFx) on reversal and place learning sets were investigated in rats by using a T-maze and a semi-circular multiple discrimination apparatus. Lesions restricted to the Fimbria (Fi) produced a significant deficit in reversal and place learning set, whereas lesions to the Fornix (Fx) only disturbed the learning set based on a reversal procedure. Combined Fi + Fx lesions resulted in impairment in the retention of spatial discrimination tested in the two mazes. Ventral Hippocampal Commissure (vhc) had no significant effect on reversal learning set. These results confirm previous data that the hippocampal formation is involved in learning transfer, and suggest that the Fi and the Fx may play a role in learning set. Our data also confirm previous demonstrations of the ability of rats to rapidly acquire place learning set.

Animals↗
PubMed2000

Learning of visuomotor transformations for vectorial planning of reaching trajectories.

The planning of visually guided reaches is accomplished by independent specification of extent and direction. We investigated whether this separation of extent and direction planning for well practiced movements could be explained by differences in the adaptation to extent and directional errors during motor learning. We compared the time course and generalization of adaptation with two types of screen cursor transformation that altered the relationship between hand space and screen space. The first was a gain change that induced extent errors and required subjects to learn a new scaling factor. The second was a screen cursor rotation that induced directional errors and required subjects to learn new reference axes. Subjects learned a new scaling factor at the same rate when training with one or multiple target distances, whereas learning new reference axes took longer and was less complete when training with multiple compared with one target direction. After training to a single target, subjects were able to transfer learning of a new scaling factor to previously unvisited distances and directions. In contrast, generalization of rotation adaptation was incomplete; there was transfer across distances and arm configurations but not across directions. Learning a rotated reference frame only occurred after multiple target directions were sampled during training. These results suggest the separate processing of extent and directional errors by the brain and support the idea that reaching movements are planned as a hand-centered vector whose extent and direction are established via learning a scaling factor and reference axes.

Adaptation, Physiological↗
PubMed2000

Ipsilateral and contralateral transfer of tactile learning.

We examined the spatial organization of perceptual learning in a cortex-dependent task. Rats learned a tactile task using four whiskers on one side of the snout, all others being clipped. These trained whiskers were then clipped and prosthetic whiskers were attached. Subsequent performance was found to be determined by the location of the prosthetic whiskers. There was partial transfer of learning to neighbouring whisker positions. In addition, there was partial transfer of learning to whisker positions on the other side of the snout, but only if the prosthetic whiskers were symmetrically opposite the trained whiskers. These findings suggest that neural changes underlying perceptual learning are distributed according to the topographic organization of the sensory cortical map.

Animals↗