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PubMed1995

Learning-related changes in hippocampal field potentials.

It is commonly believed that learning is based on modifications of synaptic strength. Much of the evidence for this comes from the observation that blockade of processes necessary for induction of long-term potentiation in the hippocampus also blocks certain forms of learning. As such correlations may have many causes, an understanding of the mechanisms for memory formation might also profit from direct recording of cellular activity in learning tasks. Field potential recording represents one such approach. Although changes in field potentials are unlikely to uncover modifications in synaptic strength related to the storage of memory, any general facilitation (or reduction) of synaptic transmission taking place in populations of neurons during the acquisition stage might be picked up by a field measure. One problem related to the approach is that field potentials are heavily affected by non-learning factors. It is shown that field potentials in the hippocampus are highly sensitive to changes in brain temperature and that a significant part of the increase in field excitatory postsynaptic potentials (f-EPSPs) during learning reflects warming of the brain. Temperature-related changes in synaptic transmission do not affect the efficiency of spatial learning, as the acquisition of a water-maze task is equally efficient at low (30-32 degrees C) and high (37-39 degrees C) brain temperatures. Subtraction of the temperature component of the field potential alterations during learning in an exploration task shows that exploration is accompanied by a temperature-independent synaptic potentiation as well. Both the f-EPSP and the population spike are increased, and both decay gradually within 15-20 min. It is important to find out whether this potentiation reflects learning-related processes and whether such a potentiation is useful to the brain given the apparent 'noise' caused by temperature-related physiological changes.

Animals↗
PubMed1995

Unilateral injury of posterior parietal cortex and spatial learning in hooded rats.

The influences of bilateral or unilateral injuries within the posterior parietal cortex (PPC) upon spatial learning in a water maze were examined in three experiments. Place-learning and response-learning were investigated in a four-alley 'Greek-cross' shaped water maze with extra-maze visual cues available. No differences were detected on any of several measures sensitive to learning between the lesion groups on the place-learning task. Microanalysis of behavior within trials revealed that animals with either bilateral or right unilateral PPC injuries committed significantly more total errors, initial alley entrance ('reference memory') errors, and re-entry ('working memory') errors in the response-learning paradigm than did either the control or left PPC-injured rats. No differences were detected between the latter two groups on these measures. Unilateral lesions resulted in asymmetrical placing responses ipsilateral to the injury 10 days after surgery whereas bilateral injuries resulted in asymmetrical placing with mixed directionality. The acquisition of the response-learning problem in the absence of visual cues was studied on animals prepared with unilateral lesions and housed post-operatively either in isolation or in a 'complex environment.' In the absence of visual cues both right and left PPC-injured rats committed more errors than sham controls, and differential post-surgical housing did not attenuate these impairments. These same animals were trained on the landmark navigation task. Although no differences appeared between the lesion groups, a generalized but transient facilitation of learning was observed in animals housed in the 'complex' environment. Unilateral injuries placed in sham controls failed to disturb retention of the landmark navigation strategy. Because none of the PPC-injured animals were deficient in the landmark task, a result which is contrary to observations in other laboratories, the influence of post-surgical recovery interval upon acquisition of the landmark navigation strategy was explored. Animals were prepared with right PPC injuries and trained following either a 5 or 35 day recovery interval. Only those animals limited to the short recovery interval proved to have a spatial deficit in the landmark task. It is concluded that injuries in the PPC of either hemisphere disturb egocentric spatial functions. However, animals with left PPC injuries are able to compensate by using allocentric visual cues if they are available. It is due to the special role played by the right PPC in complex visuospatial functions that animals with this injury are unable to compensate.

Animals↗
PubMed1990

Facilitating a match between teaching and learning styles.

As a result of educator/student interactions within a particular course, both parties anticipate that some learning will occur, some change in behaviour will have taken place and some personal growth will be evident. In order to facilitate such change every educator ought to reflect on personal practice and ask 'Is what I am doing helping the student to learn?' The answer to this question firstly should come from the student and secondly should further prompt the educator to ask 'Do I need to change my style of teaching to match the learning needs of these students?' In searching for an answer to these questions it is suggested that the teacher would need to reflect on just what constitutes teaching and learning styles. Then one might need to investigate the possibility of matching teaching style with the students' learning styles. This paper looks at the perceived need to identify different approaches to learning and the potential for matching teaching and learning styles. It is suggested that a facilitative approach to teaching, such as that used at Macarthur Institute of Higher Education in Australia, will accomodate students' learning needs.

Curriculum↗
PubMedDate not supplied

Automatic learning strategies and their application to electrophoresis analysis.

Automatic learning plays an important role in image analysis and pattern recognition. A taxonomy of automatic learning strategies is presented; this categorization is based on the amount of inferences the learning element must perform to bridge the gap between environmental and system knowledge representation level. Four main categories are identified and described: rote learning, learning by deduction, learning by induction, and learning by analogy. An application of learning by induction to medical image analysis is then exposed. It consists in the classification of two-dimensional gel electrophoretograms into meaningful distinct classes, as well in their conceptual description.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1992

A neural network model of adaptively timed reinforcement learning and hippocampal dynamics.

A neural model is described of how adaptively timed reinforcement learning occurs. The adaptive timing circuit is suggested to exist in the hippocampus, and to involve convergence of dentate granule cells on CA3 pyramidal cells, and N-methyl-D-aspartate (NMDA) receptors. This circuit forms part of a model neural system for the coordinated control of recognition learning, reinforcement learning, and motor learning, whose properties clarify how an animal can learn to acquire a delayed reward. Behavioral and neural data are summarized in support of each processing stage of the system. The relevant anatomical sites are in thalamus, neocortex, hippocampus, hypothalamus, amygdala and cerebellum. Cerebellar influences on motor learning are distinguished from hippocampal influences on adaptive timing of reinforcement learning. The model simulates how damage to the hippocampal formation disrupts adaptive timing, eliminates attentional blocking and causes symptoms of medial temporal amnesia. Properties of learned expectations, attentional focussing, memory search and orienting reactions to novel events are used to analyze the blocking and amnesia data. The model also suggests how normal acquisition of subcortical emotional conditioning can occur after cortical ablation, even though extinction of emotional conditioning is retarded by cortical ablation. The model simulates how increasing the duration of an unconditioned stimulus increases the amplitude of emotional conditioning, but does not change adaptive timing; and how an increase in the intensity of a conditioned stimulus 'speeds up the clock', but an increase in the intensity of an unconditioned stimulus does not. Computer simulations of the model fit parametric conditioning data, including a Weber law property and an inverted U property. Both primary and secondary adaptively timed conditionings are simulated, as are data concerning conditioning using multiple interstimulus intervals (ISIs), gradually or abruptly changing ISIs, partial reinforcement and multiple stimuli that lead to time-averaging of responses. Neurobiologically testable predictions are made to facilitate further tests of the model.

Animals↗
PubMed1994

Reinforcement learning control.

Reinforcement learning refers to improving performance through trial-and-error. Despite recent progress in developing artificial learning systems, including new learning methods for artificial neural networks, most of these systems learn under the tutelage of a knowledgeable 'teacher' able to tell them how to respond to a set of training stimuli. Learning under these conditions is not adequate, however, when it is costly, or even impossible, to obtain this kind of training information. Reinforcement learning is attracting increasing attention in computer science and engineering because it can be used by autonomous systems to learn from their experiences instead of from knowledgeable teachers, and it is attracting attention in computational neuroscience because it is consonant with biological principles. Recent research has improved the efficiency of reinforcement learning and has provided some striking examples of its capabilities.

Animals↗
PubMed2004

Variables influencing medical student learning in the operating room.

BACKGROUND: The operating room (OR) is an important venue where surgeons do much of medical student teaching and yet there has been little work evaluating variables that influence learning in this unique environment. We designed this study to identify variables that affected medical student learning in the OR. METHODS: We developed a questionnaire based on surgery faculty observations of learning in the OR. The medical students completed the questionnaire on 114 learning episodes in the OR. Pearson correlation coefficient was used to establish the strength of association between various variables and the student's overall perception of learning. RESULTS: The students evaluated 27 variables that might impact their learning in the OR. Strong correlations were identified between the attending physician's attitude, interactions and teaching ability in the OR and the environment being conducive to learning. CONCLUSIONS: Surgical faculty behavior is a powerful determinant of student perceptions of what provides for a favorable learning environment in the OR.

Behavior↗
PubMed2005

The effect of old age on supra-span learning of visuo-spatial sequences under incidental and intentional encoding instructions.

Recent findings [Turcotte, Gagnon, & Poirier, 2005. The effect of old age on the learning of supra-span sequences. Psychology and Aging, 20, 251-260.] indicate that incidental learning of visuo-spatial supra-span sequences through immediate serial recall declines with old age (Hebb's paradigm). In this study, we examined whether strategies induced by awareness of the repeated sequence might explain age differences. Young (18-35 years old) and older (65-80 years old) participants underwent either incidental or intentional learning instructions. Results indicated that older adults demonstrated reduced learning of the repeated sequence under both incidental and intentional instructions. In comparison, young adults showed superior learning of the repeated sequence in both conditions but intentional instructions triggered faster and greater learning in this age group. The results strongly indicated that knowledge of the repeated sequence enhanced learning only in the group of young adults. Older adults were unable to translate the knowledge of the repetition into elaborate strategies that would increase recall of the repeated sequence. Other findings suggest that incidental learning in young adults was mediated by both non-conscious and conscious recollection processes.

Adolescent↗
PubMed2004

Characterization of motor skill and instrumental learning time scales in a skilled reaching task in rat.

Successful motor skill learning requires repetitive training interrupted by rest periods. In humans, improvement occurs within and between training sessions reflecting fast and slow components of motor learning [Karni A, Meyer G, Rey-Hipolito C, Jezzard P, Adams MM, Turner R, et al. The acquisition of skilled motor performance: fast and slow experience-driven changes in primary motor cortex. Proc Natl Acad Sci USA 1998;95:861-8]. Here, these components are characterized in male and female rats using a model of skilled forelimb reaching and are compared to time scales of instrumental learning. Twenty female and 14 male adult Long-Evans rats were pre-trained to operate a motorized door (via a sensor in the opposite cage wall) to access a food pellet by tongue. Latencies between pellet removal and door opening were recorded as measures of instrumental learning. After criterion performance was achieved, skilled forelimb reaching was requested by increasing the pellet-window distance to 1.5cm. Reaching success was recorded per trial. Mean latencies decreased exponentially over sessions and no improvement within-session was found. Skill learning over eight training sessions followed an exponential course in females and a sigmoid course in males. Females acquired the skill significantly faster than males starting at higher baseline levels (P < 0.001) but reaching similar plateaus. Within-session improvement was found during the sessions 1-3 in females and 1-4 in males. Performance at the end of session 1 was not carried over to session 2. Learning curves of individual animals were highly variable. These findings confirm in rat that motor skill learning has fast and slow components. No within-session improvement is seen in instrumental learning.

Animals↗
PubMed2006

Mechanisms of same/different concept learning in primates and avians.

Mechanisms of same/different concept learning by rhesus monkeys, capuchin monkeys, and pigeons were studied in terms of how these species learned the task (e.g., item-specific learning versus relational learning) and how rapidly they learned the abstract concept, as the training set size was doubled. They had similar displays, training stimuli, test stimuli, and contingencies. The monkey species learned the abstract concept at similar rates and more rapidly than pigeons, thus showing a quantitative difference across species. All species eventually showed full concept learning (novel-stimulus transfer equivalent to baseline: 128-item set size for monkeys; 256-item set for pigeons), thus showing a qualitative similarity across species. Issues of stimulus regularity/symmetry, generalization from item pairs, and familiarity processing were not considered to be major factors in the final performances, converging on the conclusion that these species were increasingly controlled by the sample-test relationship (i.e., relational processing) leading to full abstract-concept learning.

Animals↗
PubMed2004

Abnormal activity patterns in premotor cortex during sequence learning in autistic patients.

BACKGROUND: Evidence for frontal abnormality in autism has accumulated in recent years. Our own studies have shown abnormal activation in prefrontal cortex during finger tapping and visuomotor coordination. Studies in healthy adults suggest reduced premotor and increased prefrontal activity during advanced learning stages. We examined hemodynamic changes during visuomotor learning in autistic patients. METHODS: We studied eight high-functioning autistic patients and eight control subjects during learning of an 8-digit sequence over a period of 8 min, using functional magnetic resonance imaging. RESULTS: Autistic patients showed overall less prefrontal activation during late visuomotor learning; however, the main finding was a complementary one of enhanced activation in right pericentral and premotor cortex. In the autism group, Brodmann areas 3, 4, and 6 of the right hemisphere became more involved during late learning stages (trials 25-48), compared with early stages (trials 1-24). This effect was not seen in the control group. CONCLUSIONS: Our findings suggests that in autistic patients 1) primary sensorimotor and premotor cortex, which is normally predominant in early stages of visuomotor learning, plays an atypical role in later stages, even when learning is evident; and 2) handedness and side of execution interact with asymmetry of visuomotor learning activations, contrary to what is seen in normal adults.

Adult↗
PubMed2006

Alterations in spatial learning and memory after forced exercise.

Exercise has been shown to influence learning and memory. Most studies were performed with a voluntary running paradigm (e.g. running wheel) in mice. However, such effects of exercise on learning and memory are less well demonstrated using a forced running paradigm (e.g. treadmill). The present study was designed to examine the effects of 12 weeks of forced treadmill running on learning and memory performance in rats. We have previously shown that forced running resulted in qualitative and quantitative changes in the cholinergic neurons of the horizontal diagonal band of Broca (HDB) in the septum. This study was conducted in order to determine whether or not these changes occur simultaneously with enhanced learning and memory. The one-day version of the Morris water maze (MWM) test [Frick, K.M., Stillner, E.T., Berger-Sweeney, J., 2000. Mice are not little rats: species differences in a one-day water maze task. NeuroReport 11, 3461-3465] was used to test spatial learning and memory after the exercise period. Our data showed that runners displayed better spatial learning and memory when compared to nonrunners. This was evidently shown by a reduction in the time required for spatial acquisition (p<0.05) and superior probe trial performance (p<0.05). A shorter distance swam by the runners also suggested improved learning over the nonrunners (p<0.05). In an attempt to revalidate our earlier quantitative results, we used design-based stereology (DBS) to estimate the number of cholinergic neuronal profile population in the medial septum and diagonal band (MSDB). We confirmed that forced running increased the cholinergic neuronal profile subpopulation in the HDB (Coefficient of Error<0.2). Taken together, these results indicate that forced exercise could influence learning and memory with a concomitant increase in the number of cholinergic neurons in the HDB.

Acetylcholinesterase↗
PubMed2006

Tracking pattern learning with single-trial event-related potentials.

OBJECTIVE: The main aim was to track the dynamics of pattern-learning using single-trial event-related potentials (ERPs). A new 'learning-oddball' paradigm was employed presenting eight random targets (the 'no-pattern') followed by eight regular targets (the 'pattern'). In total, six repetitions of the 'no-pattern' followed by the 'pattern' were presented. METHODS: We traced the dynamics of learning by measuring responses to 16 (eight random-eight regular) targets. Since this alternation of the 'no-pattern' followed by the 'pattern' was repeated six times, we extracted single-trial responses to all 96 targets to determine if learning occurred more rapidly with each repetition of the 'pattern.' RESULTS: Following random targets, ERPs contained a marked P3-N2 component that decreased to regular targets, whereas a contingent negative variation (CNV) appeared. ERP changes could be best described by sigmoid 'learning' curves. Single-trial analyses showed that learning occurred more rapidly over repetitions and suggested that the CNV developed prior to the decay of the N2-P3 component. CONCLUSIONS: We show a new paradigm-analysis methodology to track learning processes directly from brain signals. SIGNIFICANCE: Single-trial ERPs analyses open a wide range of applications. Tracking the dynamic structure of cognitive functions may prove crucial in the understanding of learning and in the study of different pathologies.

Acoustic Stimulation↗
PubMed2005

Implicit motor learning of a balancing task.

This study examined the implicit learning of a balancing task. Three treatment conditions were constructed using different motor learning strategies. In two of the treatment conditions, explicit learning of the balancing task was impeded by using either an analogy or an errorless learning technique. In the third treatment condition, participants learnt the task by discovery learning, which typically results in explicit knowledge. It was hypothesised that in the analogy and errorless learning conditions, learning of the balancing task would be implicit in character. Three criteria of implicit learning were used to test this hypothesis; the accumulation of few explicit rules, robustness under secondary task loading and durability over time. Although the discovery learners acquired more explicit rules, all groups appear to have acquired the skill implicitly, in that all groups were robust to imposition of a concurrent task load and over time. Indeed, balance performance with a concurrent verbal task was better than balance performance alone. Discussion focuses on the contribution of verbal and non-verbal processes to balancing.

Adult↗
PubMed2006

Music increases frontal EEG coherence during verbal learning.

Anecdotal and some empirical evidence suggests that music can enhance learning and memory. However, the mechanisms by which music modulates the neural activity associated with learning and memory remain largely unexplored. We evaluated coherent frontal oscillations in the electroencephalogram (EEG) while subjects were engaged in a modified version of Rey's Auditory Verbal Learning Test (AVLT). Subjects heard either a spoken version of the AVLT or the conventional AVLT word list sung. Learning-related changes in coherence (LRCC) were measured by comparing the EEG during word encoding on correctly recalled trials to the immediately preceding trial on which the same word was not recalled. There were no significant changes in coherence associated with conventional verbal learning. However, musical verbal learning was associated with increased coherence within and between left and right frontal areas in theta, alpha, and gamma frequency bands. It is unlikely that the different patterns of LRCC reflect general performance differences; the groups exhibited similar learning performance. The results suggest that verbal learning with a musical template strengthens coherent oscillations in frontal cortical networks involved in verbal encoding.

Acoustic Stimulation↗
PubMed2006

Stochastic complexities of general mixture models in variational Bayesian learning.

In this paper, we focus on variational Bayesian learning of general mixture models. Variational Bayesian learning was proposed as an approximation of Bayesian learning. While it has provided computational tractability and good generalization in many applications, little has been done to investigate its theoretical properties. The asymptotic form was obtained for the stochastic complexity, or the free energy in the variational Bayesian learning of a mixture of exponential-family distributions, which is the main contribution this paper makes. We reveal that the stochastic complexities become smaller than those of regular statistical models, which implies that the advantages of Bayesian learning are still retained in variational Bayesian learning. Moreover, the derived bounds indicate what influence the hyperparameters have on the learning process, and the accuracy of the variational Bayesian approach as an approximation of true Bayesian learning.

Animals↗
PubMed2005

Feed-forward associative learning for volitional movement control.

One of the most difficult problems in motor learning is determining the source of a learning signal, sometimes called an error signal. This problem is hidden in the adaptations of simple reflexive movements by attributing its source to sensory organs. The feed-forward associative motor learning theory proposed here attributes the source to the movement system itself. When a subject performs a corrective movement after his primary movement, the proposed neural learning device learns to associate the primary motor command with the corrective motor command by using a place-coding system. In the subsequent trials, the primary movement will involve a correction due to the participation of this mechanism, thus resulting in better performance. The theory assumes three conditions, namely, that a motor center and the learning device share the same place-encoded motor information; the motor center issues a command and a learning signal simultaneously from the same unit; and a learning signal issued with a corrective command has a heterosynaptic interaction with the previous primary command. The cerebellum is a reasonable candidate for the device satisfying these conditions. The reaction time of a corrective movement, usually 100-300 ms, almost satisfies the coincidence condition for long-term depression of the granule-to-Purkinje synapses. As an application, this theory is demonstrated to account for behavioral results regarding saccadic adaptation.

Association Learning↗
PubMed2004

Voxel-based morphometry of comorbid schizophrenia and learning disability: analyses in normalized and native spaces using parametric and nonparametric statistical methods.

We employed voxel-based morphometry (VBM) to compare the distributions of grey matter found in structural magnetic resonance imaging (MRI) brain scans of patients with comorbid learning disability with schizophrenia, schizophrenia alone, learning disability alone, and normal controls. Our primary aim was to replicate a previous region of interest (ROI) finding that comorbids and schizophrenics belong to the same population. Nonparametric analysis in normalized space showed no significant differences in grey matter distribution between the comorbid and schizophrenia groups. Furthermore, this analysis showed significant grey matter reductions in the comorbid and schizophrenia groups when compared to the learning-disabled or the normal controls. Parametric analysis localized the significant grey matter reductions between the normal controls and the comorbid and schizophrenia groups to the prefrontal and temporal lobes. It also identified an area of increased grey matter, on the inferior aspect of the postcentral gyrus, in the learning-disabled alone compared to the other groups. Native space parametric and nonparametric analyses, based on modulation of the normalized scans, confirmed the similarity in grey matter distribution of the comorbid and schizophrenia groups. Results confirm the ROI finding that in native space the learning-disabled group possesses the least and normal controls the most grey matter for the cohort. An increase in the basal ganglia of patients with schizophrenia vs. the learning-disabled, probably attributable to antipsychotic medication, was identified in the native space analysis. The native space results did not however register statistically significant temporal lobe reductions found under normalized analysis between schizophrenics and normal controls. This may be attributable to minor physical anomalies (MPA) in the schizophrenic cranium. Overall, these VBM results replicate previous ROI findings and are compatible with the view that comorbid learning disability with schizophrenia is a severe form of schizophrenia, rather than a consequence of learning disability. VBM has the facility to compare grey matter distributions in this structurally diverse cohort.

Adult↗