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PubMed2006

Learning to smell the roses: experience-dependent neural plasticity in human piriform and orbitofrontal cortices.

It is widely presumed that odor quality is a direct outcome of odorant structure, but human studies indicate that molecular knowledge of an odorant is not always sufficient to predict odor quality. Indeed, the same olfactory input may generate different odor percepts depending on prior learning and experience. Combining functional magnetic resonance imaging with an olfactory paradigm of perceptual learning, we examined how sensory experience modifies odor perception and odor quality coding in the human brain. Prolonged exposure to a target odorant enhanced perceptual differentiation for odorants related in odor quality or functional group, an effect that was paralleled by learning-induced response increases in piriform cortex and orbitofrontal cortex (OFC). Critically, the magnitude of OFC activation predicted subsequent improvement in behavioral differentiation. Our findings suggest that neural representations of odor quality can be rapidly updated through mere perceptual experience, a mechanism that may underlie the development of odor perception.

Adult↗

PubMedDate not supplied

One cow does not an animal make: young children can extend novel words at the superordinate level.

Six match-to-sample picture/object selection experiments were designed to explore children's knowledge about superordinate words (e.g., "food") and how they acquire this knowledge. Three factors were found to influence the learning and extension of superordinate words in 3- to 5-year-old children (N = 230): The number of standards (one versus two), the type of standards presented (from different basic-level categories versus from the same basic-level category), and the nature of the object representations used (pictures versus objects). A different pattern of superordinate word acquisition was found between 3-year-olds and 4- and 5-year-olds. Although 4- and 5-year-olds could learn and extend novel words to superordinate categories in the presence of two picture exemplars from different categories or a single three-dimensional (3-D) exemplar, 3-year-olds could do so only in the presence of two 3-D exemplars. These findings indicate that young children's acquisition of superordinate words is influenced by multiple factors and that there is a developmental progression from multiple exemplars to single exemplars in superordinate word learning.

Child Language↗

PubMed1997

Tactile learning is task specific but transfers between fingers.

Practice-related improvement in visual perception is highly specific for properties of the stimulus used in training. We explored the specificity of such perceptual learning in the human tactile system, using gratings consisting of alternating ridges and groves. Practice effects on grating discrimination showed limited transfer between grating sets defined by spatial variation in either groove width or ridge width, consistent with partially overlapping neural representations of these two spatial parameters. In contrast, substantial interdigital transfer of practice effects occurred for discrimination of gratings varying in either spatial parameter and also for spatial acuity-dependent discrimination of grating orientation. We conclude that tactile learning, although quite as task specific as in other sensory systems, generalizes with considerable facility across fingers, unlike visual learning, which is highly location specific.

Adult↗

PubMed1991

Reverse-Hebb plasticity leads to optimization and association in a simulated visual cortex.

The effects of a variable-phase synaptic modification rule on the experience-dependent development of a simulated visual cortex were investigated. Of interest were the process of optimization of the internal representation with respect to orientation, through which the weakly tuned neurons of visually inexperienced animals attain their tightly tuned adult characteristics, and the process of association by which identical stimuli presented to either eye come to evoke identical cortical representations. In its general form, the synaptic modification rule was Hebbian. However, it was not assumed that positive correlation of presynaptic and postsynaptic activity would lead to an increase in synaptic weight. The relative phase of presynaptic vs. postsynapatic activity that would effect an increase in synaptic weight was a parameter of the modification rule. When this parameter was zero, synaptic modification conformed to the standard Hebbian type. With a value of 180 deg, or the reverse-Hebb condition, negative correlation between presynaptic and postsynaptic activity led to increased synaptic weight. It was found that a synaptic modification rule of the reverse-Hebb type not only optimized the cortical representation, and associated the representations from the two eyes, but was quite stable with respect to retaining the optimized state for long periods of learning.

Animals↗

PubMed1996

Comparison of perioral reflex modulation in the upper and lower lip.

The spatiotemporal organization and specificity of the mechanically evoked, short latency perioral response (R1) was sampled from a group of normal adult humans. Perioral reflex activity was sampled during passive and active static force conditions in the presence of servo-controlled mechanical inputs to lip vermilion. Results confirmed that the sensorimotor apparatus of the lower face is very responsive to low level mechanical inputs and highly dependent on several factors including input site (upper vs. lower lip), amount of glabrous tissue stimulated (contactor array size), and task dynamics (passive vs. active subject-generated lip force). Arguments are presented to support the idea that several features of the peripheral sensory environment encoded by primary trigeminal afferents, including afferent gain, specificity, locus, and spatial summation, collectively provide inputs vital to higher order sensory relays in the development of a central representation and dynamic conformational map of perioral space. These sensorimotor features encoded by trigeminal afferents are presumed important for motor learning and maintenance of oromotor control during speech, suck, mastication and swallow, and gesture.

Adolescent↗

PubMed2005

Stimulus-specific sequence representation in serial reaction time tasks.

Some recent evidence has favoured purely response-based implicit representation of sequences in serial reaction time tasks. Three experiments were conducted using serial reaction time tasks featuring four spatial stimuli mapped in categories to two responses. Deviant items from the expected sequence that required the expected response resulted in increased response latencies. The findings demonstrated a stimulus-specific form of representation that operates in the serial reaction time task. No evidence was found to suggest that the stimulus-specific learning was contingent on explicit knowledge of the sequence. Such stimulus-based learning would be congruent with a shortcut within an information-processing framework and, combined with other research findings, suggests that there are multiple loci for learning effects.

Adult↗

PubMed1995

The "wake-sleep" algorithm for unsupervised neural networks.

An unsupervised learning algorithm for a multilayer network of stochastic neurons is described. Bottom-up "recognition" connections convert the input into representations in successive hidden layers, and top-down "generative" connections reconstruct the representation in one layer from the representation in the layer above. In the "wake" phase, neurons are driven by recognition connections, and generative connections are adapted to increase the probability that they would reconstruct the correct activity vector in the layer below. In the "sleep" phase, neurons are driven by generative connections, and recognition connections are adapted to increase the probability that they would produce the correct activity vector in the layer above.

Algorithms↗

PubMed1996

Networks with lateral connectivity. III. Plasticity and reorganization of somatosensory cortex.

1. Mechanisms underlying cortical reorganizations were studied using a three-layered neural network model with neuronal groups already formed in the cortical layer. 2. Dynamic changes induced in cortex by behavioral training or intracortical microstimulation (ICMS) were simulated. Both manipulations resulted in reassembly of neuronal groups and formation of stimulus-dependent assemblies. Receptive fields of neurons and cortical representation of inputs also changed. Many neurons that had been weakly responsive or silent became active. 3. Several types of learning models were examined in simulating behavioral training, ICMS-induced dynamic changes, deafferentation, or cortical lesion. Each learning model most accurately reproduced features of experimental data from different manipulations, suggesting that more than one plasticity mechanism might be able to induce dynamic changes in cortex. 4. After skin or cortical stimulation ceased, as spontaneous activity continued, the stimulus-dependent assemblies gradually reverted into structure-dependent neuronal groups. However, relationships among individual neurons and identities of many neurons did not return to their original states. Thus a different set of neurons would be recruited by the same training stimulus sequence on its next presentation. 5. We also reproduced several typical long-term reorganizations caused by pathological manipulations such as cortical lesions, input loss, and digit fusion. 6. In summary, with Hebbian plasticity rules on lateral connections, the network model is capable of reproducing most characteristics of experiments on cortical reorganization. We propose that an important mechanism underlying cortical plastic changes is formation of temporary assemblies that are related to receipt of strongly synchronized localized input. Such stimulus-dependent assemblies can be dissolved by spontaneous activity after removal of the stimuli.

Afferent Pathways↗

PubMed2004

Failure to construct and transfer correct representations across probability problems.

Previous studies carried out on "purely random" situations (with dice or poker chips) show the difficulties encountered by people in such situations, however simple they may be. In fact, in this type of situation, prior knowledge guides spontaneous representations, and the "errors" observed could be explained by the activation of "implicit models" which form the basis of erroneous representations. 42 statistically naïve undergraduates were given several variants of a probability problem on which errors are common. In a learning phase, subjects were given four problems involving geometric figures which were pairwise related by complementarity and equivalence relations. In a subsequent transfer phase, they were given a fifth problem involving poker chips, which was structurally isomorphic to the fourth geometric-figures problem. The findings show that people do not realize the relations between problems, and that transfer occurred only for the subset of subjects who performed correctly on the training problems of the learning phase. These results appear to have some significant implications in teaching mathematical concepts.

Adolescent↗

PubMed2001

Conjunctive bias in memory representations of logical connectives.

The paper presents the conjunctive bias in memory-a novel phenomenon that helps to clarify representations of logical connectives. The conjunctive bias is a tendency toward more accurate recall and recognition of conjunctive forms than of forms based on other logical connectives and a tendency to recall and recognize other logical forms as if they were conjunctions. Three experiments, in which participants' memory representations associated with different logical connectives were examined, were conducted to test the conjunctive bias hypothesis. In Experiment 1, participants learned picture-proposition pairs involving either conjunctions or disjunctions and then had to recall each proposition when cued with its picture. In Experiments 2 and 3, recognition memory for conjunctions, disjunctions, and conditionals was examined with an old/new recognition procedure. The findings of these experiments provide evidence for the conjunctive bias. Furthermore, the results of Experiment 3 suggest that corjunctive bias is not simply a pragmatically caused preference for conjunctions. The discussion focuses on the implications of these findings for current theories of deductive reasoning.

Adult↗

PubMed2003

Measurements of the level of surgical expertise using flight path analysis from da Vinci robotic surgical system.

Laparoscopic surgical procedures require precise hand and eye coordination based on a 2-dimensional representation of 3-dimensional space. Currently, no metric exists to guide the educational process while surgeons are still on the learning curve. In this paper, we propose to identify and qualify the patterns of movements recorded from the da Vinci robotic surgical system (Intuitive Surgical, Sunnyvale CA) that are most consistent with mastery and can define levels of proficiency. We have recorded velocities and positions of complex movements made by both novice and expert surgeons using da Vinci system and performed geometric and statistical analysis of the data.

Clinical Competence↗

PubMed1990

The babel of the unconscious.

This paper illustrates our clinical and personal experiences concerning the vast and complex theme of 'Polylingualism in psychoanalysis'. The issue of polylingualism and polyglotism reintroduces some general psychoanalytic hypotheses. For instance, is the nature of the unconscious predominantly pre-verbal, or is it structured as a language? What occurs if some languages are known since very early childhood, and belong to a pre-symbolic structural patrimony closely bound to bodily sensations and concrete experiences? How does the learning of new languages, later on, affect or modify thought processes? How do new and old unconscious 'thing' and 'word' representations interact with each other? What are the related problems regarding repression and memory? Our paper illustrates and discusses problems of communication and comprehension within the clinical situation, in cases when the analytic language is not the mother-tongue of the analyst, or of the patient, or of either of them.

Adult↗

PubMed1993

[The importance of balance, generalization and positivity as cognitive structural rules].

Three formal schemata (the cognitive rules of balance, generalization and positivity) were examined to determine their impact on the retention of information about social configurations. First, under standard conditions (12 relations) better retention for relations stemming from balanced configurations was demonstrated, in accordance with the Heiderian memory hypothesis (Experiment 1). Neither generalization nor positivity were observed. The second experiment, which involved 24 relations, showed both generalization and positivity to be effective. A balance effect therefore appears to be limited to a maximum of about 18-21 to-be-learned relations. Beyond this limit, however, the simpler rules (positivity and generalization) can still have an impact on memory. Thus, learning remains schema-driven and does not become "rote learning". The failure of balance to be effective when a larger amount of material is involved is discussed with reference to two alternatives: interference by the number of relations and interference by the number of triads. The significance of the regarding models of representation for social relations in memory is also discussed.

Adult↗

PubMed2000

How does the brain learn language? Insights from the study of children with and without language impairment.

Neurobiological studies have generated new ways of thinking about development of brain structure and function. Development involves more than just growth from simple to complex structures. The initial over-abundance of neurons and synaptic connections is subsequently pruned of those that are non-functional. In addition, as behavioural and cognitive functions emerge and become automatized, the underlying brain representations are reorganized. In this paper, I shall argue that these different modes of neurodevelopmental change provide a useful metaphor for examining language acquisition. It will be argued that language acquisition can involve learning to ignore and inhibit irrelevant information, as well as forming new ways of representing complex information economically. Modular organization is not present from the outset, but develops gradually. This analysis suggests a new way of assessing specific language impairment (SLI). There has been much debate as to whether children with SLI lack specific modular components of a language processing system. I propose instead that these children persist in using inefficient ways of representing language. Finally, I consider what we know about the neurobiological basis of such a deficit. There is mounting evidence that children with SLI have subtle structural anomalies affecting the language areas of the brain, which are largely genetically determined. We should not, however, conclude that the language difficulties are immutable.

Brain↗

PubMed2002

Motor learning by observation: evidence from a serial reaction time task.

This study sought evidence of observational motor learning, a type of learning in which observation of the skilled performance of another person not only facilitates motor skill acquisition but does so by contributing to the formation of effector-specific motor representations. Previous research has indicated that observation of skilled performance engages cognitive processes similar to those occurring during action execution or physical practice, but has not demonstrated that these include processes involved in effector-specific representation. In two experiments, observer subjects watched the experimenter performing a serial reaction time (SRT) task with a six-item unique sequence before sequence knowledge was assessed by response time and/or free generation measures. The results suggest that: (1) subjects can acquire sequence information by watching another person performing the task (Experiments 1-2); (2) observation results in as much sequence learning as task practice when learning is measured by reaction times (RTs) and more than task practice when sequence learning is measured by free generation performance (Experiment 2, Part 1); and (3) sequence knowledge acquired by model observation can be encoded motorically--that is, in an effector-specific fashion (Experiment 2, Part 2).

Adult↗

PubMed2004

Neural representation of interval time.

Animals can predict the time of occurrence of a forthcoming event relative to a preceding stimulus, i.e. the interval time between those two, given previous learning experience with the temporal contingency between them. Accumulating evidence suggests that a particular pattern of neural activity observed during tasks involving fixed temporal intervals might carry interval time information: the activity of some cortical and subcortical neurons ramps up slowly and linearly during the interval, like a temporal integrator, and peaks around the time at which the event is due to occur. The slope of this climbing activity, and hence the peak time, adjusts to the length of a temporal interval during repetitive experience with it. Various neural mechanisms for producing climbing activity with variable slopes, representing the length of learned intervals, are discussed.

Animals↗

PubMed2006

Comparing distances in mental images constructed from visual experience or verbal descriptions: the impact of survey versus route perspective.

Mental images constructed after visual examination of a spatial configuration or after processing a verbal description of that configuration have been shown to share similar properties, in particular the capacity to preserve metric information contained in the configuration represented. In the present study, we investigated the properties of mental images constructed under learning conditions resulting from the combination of a visual or a verbal mode of acquisition and a survey or route perspective. Participants memorized a virtual environment (a garden containing six objects) under one of four learning conditions: (a) viewing a map of the garden (visual-survey); (b) viewing a video presentation of a journey along the path around the garden (visual-route); (c) listening to a verbal description of the map of the garden (verbal-survey); and (d) listening to a verbal description of the journey around the garden (verbal-route). The participants were then invited to compare the distances separating objects in the garden mentally. Experiment 1, where the pairs of distances to be compared had a common starting point, revealed that the frequency of correct responses was higher, and response times were shorter when participants had learned about the environment visually rather than by a verbal description. The conditions involving a survey perspective resulted in a higher frequency of correct responses and shorter response times than those involving a route perspective. Lastly, a symbolic distance effect was obtained in the first three conditions, in that the greater the difference between the two distances being compared, the higher the frequency of correct responses, and the shorter the response times. Experiment 2, where the pairs of distances had different starting points, replicated these results, although longer response times revealed that the comparison process was more costly. Taken together, these findings support the view that mental spatial representations derived from different sources and adopting different perspectives contain genuine metric properties, except when the verbal modality and the route perspective are combined during learning.

Adolescent↗

PubMed1998

Developing and implementing interprofessional learning in a Faculty of Health Professions.

Interprofessional education enables health professional students to learn together in order to work together. The Faculty of Health Professions at Dalhousie University has developed interprofessional learning within the core curriculum of eight educational programs. An interprofessional coordinator consulted with students and faculty to prepare a collective statement of the purpose, learning models, and implementation principles of interprofessional learning. Planning, implementation, and evaluation of a first interprofessional module, Professional Ethics: Issues of Autonomy, was carried out by the interprofessional Working Group with representation from all programs in the faculty. 437 students (25-30 per session) participated in the first three-hour interprofessional module, which was offered in 16 evening sessions. Evaluation themes included the positive aspect of contact and discussion with students from other health professions, and the need to include medical students. The Faculty of Health Professions is planning to improve upon this first module, introduce other modules, and extend contact with other university faculties and community professionals.

Curriculum↗