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Failure to transfer a digging response to a detour problem in young rats with lesions to the "general learning system".

Recent lesion studies on young rats suggest that the components of the rodent's general learning system (GLS; a group of brain structures essential for normal acquisition of a wide range of laboratory tasks, include the regions of the caudatoputamen, globus pallidus, ventrolateral thalamus, substantia nigra, ventral tegmental area, superior colliculus, median raphe, and pontine reticular formation). The current study provides evidence that young GLS-lesioned rats, like mentally retarded humans, may be suffering from a disturbance in some superordinate ability (executive functioning) that controls the use of learning strategies in general and the transfer of learning in particular. Specifically, thirsty rats were initially trained to traverse a narrow runway to reach a goal box containing water. When a portion of the runway was blocked with sawdust, all of the sham-operated control rats succeeded in burrowing through the sawdust to gain access to the goal box, whereas most of our GLS-lesioned rats failed to do so even though they "knew how" to dig. Neocortically damaged rats showed a similar though significantly smaller deficit. Although other interpretations are possible, these data give tentative support to the view that this impairment in transfer reflects a defect in executive processing.

Animals↗

Do ability-performance relationships differentiate age and practice effects in visual search?

Relationships between abilities and performance in visual search were investigated for young and old adults. Ss received extensive practice on category search task. A consistent version allowed development of an automatic attention response; a varied version allowed general performance improvements. Transfer conditions assessed learning. General ability, induction, semantic knowledge, working memory, perceptual speed, semantic memory access, and psychomotor speed were assessed. LISREL models revealed that general ability and semantic memory access predicted initial performance for both ages. Improvements on both the consistent and varied tasks were predicted by perceptual speed. Ability-performance relationships indexed performance changes but were not predictive of learning (i.e., automatic process vs. general efficiency). Qualitative differences in the ability-transfer models suggest age differences in learning.

Adolescent↗

State-dependent learning produced by chlordiazepoxide and its transfer at different dose levels.

In Experiment I, the rat was given 15 mg/kg of chlordiazepoxide (CDP) and trained on a black-white discrimination task, motivated by electric shocks; the same animal, when given saline, was treated similarly with the reversed cue relationship on different and usually alternate sessions. Training was continued until a learning criterion under both drug and saline states and then tested with only one of five testing CDP doses (2.5, 5, 10, 20 and 25 mg/kg). During training, the rat made more errors under drug than under saline but there were little differences in starting and running times at least during the last sessions. In the transfer test, choice responses showed a bi-directional gradient around the training dose as in stimulus generalization gradient. Experiment II was identical to Experiment I, except that the same drug was tested at all five transfer doses and the resulting transfer gradient was a simple monotonic increasing function of dose levels. Discrepancy between the two experiments was discussed.

Animals↗

Primary visual cortex and memory. Retinal position specificity and lack of size constancy at early stages of learning a visual memory task in the macaque.

Two monkeys were trained in a novel version of a delayed match-to-sample (DMS) task. They were required to fixate on a small spot at the center of the monitor and distinguish whether two gratings presented one after the other with delays up to 1.5 s in a specific visual field location were similar or not. It was found that such learning fails to transfer readily to other retinal locations. In fact, the learning was sensitive even to very small retinal displacements of the visual stimuli. Such acute retinal position specificity implies that at least a component of the learning in this particular memory task occurs at an early visual area such as the striate cortex, which has a fine-grain topographical representation. Furthermore, at early stages of learning the DMS task, when the monkeys had not generalized the learning to stimuli of different sizes, they failed to show size constancy. That is, when the display was placed at a different distance but with the same absolute size, the performance dropped. The performance was almost fully restored when, at the new display location, stimuli were changed to fit the original retinal size. This indicates that a crucial component of the learning does occur at a site even prior to size constancy. These results show that, under certain situations, an early visual area such as the primary visual cortex may be involved even in complex behaviours such as a memory task as more than just a feature-detecting area or a relay station.

Animals↗

Integrating some mind and brain views of transference: the phenomena.

Because understanding the underpinnings of transferential learning allows the analyst to more effectively exploit transference in the clinical situation, as well as to advance psychoanalytic theory, the functions and mechanisms of transference phenomena in learning are subjected to an interdisciplinary analysis. Through transference the brain creates hierarchical databases that make emotional sense of the world, especially the world of human relationships. Transference plays a role in defense and resistance clinically; less explored but equally important is the adaptive potential of transference and its effect on an individual's readiness for structural change through the activation of working memory. Most investigators within psychoanalysis have not considered the importance of similarity judgments and memory priming, especially as these help to explain why transference and its proper handling are effective in treatment. Yet there are complex relationships among transference, similarity judgment, and memory priming that tie together psychoanalysis, cognitive psychology, and neurophysiology. Evidence increasingly suggests a relationship between transference and the transfer of knowledge between various content domains (databases) of mind and brain, which is essential to cognitive and emotional learning. There are indications as well that transference decisively facilitates learning readiness ("windows") in general by means of two of its components: free association and spontaneous (self-initiated) activity. The important question of which mind/brain mechanisms motivate transference is not yet understood comprehensively. However, Vygotsky's work on the zone of proximal development (ZPD), M.Stern's teleonomic theory, schema theory, and neural network theory offer further insights into what motivates transference.

Free Association↗

Independent perceptual learning in monocular and binocular motion systems.

Eye-transfer tests, external noise manipulations, and observer models were used to systematically characterize learning mechanisms in judging motion direction of moving objects in visual periphery (Experiment 1) and fovea (Experiment 2) and to investigate the degree of transfer of the learning mechanisms from trained to untrained eyes. Perceptual learning in one eye was measured over 10 practice sessions. Subsequent learning in the untrained eye was assessed in five transfer sessions. We characterized the magnitude of transfer of each learning mechanism to the untrained eye by separately analyzing the magnitude of subsequent learning in low and high external noise conditions. In both experiments, we found that learning in the trained eye reduced contrast thresholds uniformly across all of the external noise levels: 47 +/- 10% and 62 +/- 8% in experiments 1 and 2, respectively. Two mechanisms, stimulus enhancement and template retuning, accounted for the observed performance improvements. The degree of transfer to the untrained eye depended on the amount of external noise added to the signal stimuli: In high external noise conditions, learning transferred completely to the untrained eye in both experiments. In low external noise conditions, there was only partial transfer of learning: 63% in experiment 1 and 54% in experiment 2. The results suggest that template retuning, which is effective in high external noise conditions, is mostly binocular, whereas stimulus enhancement, which is effective in low external noise displays, is largely monocular. The two independent mechanisms underlie perceptual learning of motion direction identification in monocular and binocular motion systems.

Fixation, Ocular↗

Resolution-dependent self-supervised transfer in chest radiograph classification.

BACKGROUND: Self-supervised learning (SSL) has improved visual representation learning, but its value in chest radiography remains uncertain. DINOv3 extends earlier SSL models through Gram-anchored self-distillation and explicit high-resolution adaptation. Whether these changes improve transfer learning for chest radiograph classification has not been established. METHODS: We benchmarked DINOv3 against DINOv2 and supervised ImageNet initialization across seven chest radiograph datasets comprising 816,183 radiographs from pediatric and adult cohorts. ViT-B/16 and ConvNeXt-B were evaluated under full fine-tuning at 224 × 224 and 512 × 512 pixels, with targeted 1024 × 1024 experiments on three cohorts. Additional analyses examined parameter-efficient adaptation, synthetic label corruption, external validation, frozen 7B features, and computational efficiency. The primary outcome was the mean area under the receiver operating characteristic curve across labels. RESULTS: In adult cohorts, DINOv3 did not consistently outperform DINOv2 at 224 × 224 pixels, but became the strongest initialization at 512 × 512 pixels, especially with ConvNeXt-B. Gains were greatest for small focal and boundary-dependent abnormalities, whereas large-structure findings changed little. The pediatric cohort showed no significant benefit from DINOv3, higher resolution, or backbone choice. Scaling to 1024 × 1024 rarely improved performance and markedly increased computational cost. ConvNeXt-B remained superior to ViT-B/16 under both full and parameter-efficient adaptation. External validation preserved the 512 × 512 DINOv3 advantage, whereas synthetic label corruption showed that this benefit should not be interpreted simply as superior noise robustness. Frozen DINOv3-7B features underperformed relative to fully adapted 86 to 89M-parameter backbones. CONCLUSIONS: For adult chest radiograph classification, DINOv3 provides its most reliable benefit at 512 × 512 pixels, particularly with ConvNeXt-B. Fully adapted mid-sized models at 512 × 512 pixels provided the best performance-cost trade-off in our benchmark.

Journal Article↗

The locus of visual-motor learning at the task or manipulator level: implications from intermanual transfer.

To assess the functional locus of visual-motor learning, the computational concepts of "task level" programming (determination of the trajectory of a hand during arm reaching in the Cartesian coordinates) and "manipulator level" programming (determination of the joint coordinates) was adopted. Because the former is likely to be hand nonspecific and the latter is hand specific, it is assumed that learning at the task level should be transferred to the unpracticed hand, whereas that at the manipulator level it should not. Under this assumption, the paradigm of intermanual transfer was used in an aiming task under rotated visual feedback. Nearly 100% intermanual transfer from the practiced hand to the unpracticed hand in the performance time of aiming was found, concluding that the locus of visual-motor learning should be at the task level rather than at the manipulator level.

Adolescent↗

Transfer of a discrimination by pigeons (Columba livia) between pictured locations and the represented environments.

In Experiment 1, pigeons (Columba livia) were trained in a successive slide presentation procedure to discriminate between pictures of 2 ends of a room and then trained to find food in the actual room. A congruent-transfer (CT) group learned the spatial discrimination more quickly than an incongruent-transfer (IT) group. In Experiment 2's replication we used a simultaneous slide presentation procedure and added a control group. The IT group required significantly more trials than the CT or control groups. In Experiment 3, order of the training conditions was reversed. CT and IT conditions had no effect on the speed of acquisition of the discrimination. This indicates that pigeons acquire a representation of spatial locations from pictures, which can then direct behavior, but the direction of transfer observed was unidirectional. This suggests that a discrimination between spatial locations may not be accurately represented in pictorial form.

Animals↗

Effect of foot-shock intensity on amount of memory retrieval in rats by emotionally important stimuli in a drug-dependent learning escape design.

Drug-dependent learning (lack of transfer between drug states) was demonstrated and disrupted in an escape learning, forced choice T-maze task. A drug-dependent learning (DDL) group was trained to escape foot shock (0.65 mA) while in a drug (chlordiazepoxide hydrochloride) state. These rats subsequently responded randomly on non-shock test trials in the non-drug state, but continued to respond significantly (P less than 0.02) above random level when in the training drug state. Four transfer groups were also trained in the Drug state, but with a 1 kHz auditory tone simultaneously paired with foot shock. Each Transfer group received a different (0.10, 0.65, 3.5, and 4.5 mA) foot shock intensity during training. The auditory tone continued to be sounded during testing with no foot shock, and percentage correct turns, first-trial correct turns, and latency scores were significantly (P less than 0.01) different from the DDL group's performance. The results were interpreted as demonstrating that an emotionally-important auditory stimulus could initiate a memory retrieval process that could overcome a physiological state. This memory retrival process was not modified by wide variations in foot shock intensity.

Acoustic Stimulation↗

Side-specificity of olfactory learning in the honeybee: generalization between odors and sides.

Honeybees (Apis mellifera) can be trained to associate an odor stimulus with a sucrose reward. The neural structures involved in the detection and integration of olfactory stimuli are represented bilaterally in the brain. Little is known about the respective roles of the two sides of the brain in olfactory learning. Does each side learn independently of the other, or do they communicate, and if so, to what extent and at what level of neural integration? We addressed these questions using the proboscis extension response (PER) conditioning paradigm applied in a preparation that allows the separation of the two input sides during olfactory stimulations. Bees conditioned to two odorants A and B, one being learned on each side (A+/B+ training), showed in extinction tests rather unspecific responses: They responded to both odorants on both sides. This could be attributable to either a transfer of the learned information between sides, or to a generalization between odorants on each side. By subjecting bees to conditioning on one side only (A+/0 training), we found that the learned information is indeed transferred between sides. However, when bees were trained explicitly to give opposite values to the two odorants on the two sides (A+B-/B+A- training), they showed clear side-specific response patterns to these odorants. These results are used in the elaboration of a functional model of laterality of olfactory learning and memory processing in the honeybee brain.

Animals↗

Factors influencing the energetics of electron and proton transfers in proteins. What can be learned from calculations.

A protein structure should provide the information needed to understand its observed properties. Significant progress has been made in developing accurate calculations of acid/base and oxidation/reduction reactions in proteins. Current methods and their strengths and weaknesses are discussed. The distribution and calculated ionization states in a survey of proteins is described, showing that a significant minority of acidic and basic residues are buried in the protein and that most of these remain ionized. The electrochemistry of heme and quinones are considered. Proton transfers in bacteriorhodopsin and coupled electron and proton transfers in photosynthetic reaction centers, 5-coordinate heme binding proteins and cytochrome c oxidase are highlighted as systems where calculations have provided insight into the reaction mechanism.

Bacteriorhodopsins↗

Task analysis in curriculum design: a hierarchically sequenced introductory mathematics curriculum.

A method of systematic task analysis is applied to the problem of designing a sequence of learning objectives that will provide an optimal match for the child's natural sequence of acquisition of mathematical skills and concepts. The authors begin by proposing an operational definition of the number concept in the form of a set of behaviors which, taken together, permit the inference that the child has an abstract concept of "number". These are the "objectives" of the curriculum. Each behavior in the defining set is then subjected to an analysis that identifies hypothesized components of skilled performance and prerequisites for learning these components. On the basis of these analyses, specific sequences of learning objectives are proposed. The proposed sequences are hypothesized to be those that will best facilitate learning, by maximizing transfer from earlier to later objectives. Relevant literature on early learning and cognitive development is considered in conjunction with the analyses and the resulting sequences. The paper concludes with a discussion of the ways in which the curriculum can be implemented and studied in schools. Examples of data on individual children are presented, and the use of such data for improving the curriculum itself, as well as for examining the effects of other treatment variables, is considered.

Journal Article↗