Categorical and spatial modes of representation in young children's recall.
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Conservation acquisition, maintenance, and generalization by mentally retarded children using equality-rule training.
To teach conservation to mildly retarded, preoperational preadolescents (9 to 12 years old), a number-representational system was used to mediate the invariance of quantity as part of "equality-rule" training. Before viewing a perceptually misleading configuration of either two equal quantities or two unequal quantities entailing the dimensions of number or length, participants learned that equality involved the assignment of two identical numbers and inequality the assignment of two different numbers. These numbers were then applied to the actual quantities and became the basis for rule statements that were rehearsed, memorized, and subject-generated each time the quantities were transformed into a new configuration. Following equality training, correct judgments and verbal justifications of conservation were high (M greater than or equal to 85%) during both immediate and delayed post-tests and for near-generalization (number and length) and far-generalization (weight, liquid substance, and solid substance) tasks. In contrast, the post-test levels of comparable participants given learning-set (LS) training, LS plus verbal-rule training (a combination of statements about identity, negation, and compensation), or no training at all were substantially and significantly lower. Equality training is of theoretical and practical interest because of its potential to teach a symbolic representational rule that directly and meaningfully articulates the quantitative properties of objects and counteracts the overreliance on task-specific and faulty perceptual cues inherent in the conservation task.
Child↗
GAD67-positive puncta: contributors to learning-dependent plasticity in the barrel cortex of adult mice.
We have previously shown that a classical aversive conditioning paradigm involving stimulation of a row of facial vibrissae (whiskers) in the mouse produced expansion of the cortical representation of the activated vibrissae ("trained row"). This was demonstrated by labeling with 2-deoxyglucose (2DG) in layer IV of the barrel cortex. We have also shown that functional reorganization of the S1 cortex is accompanied by increases in the density of small GABAergic cells, and in GAD67 mRNA in the hollows of barrels representing the "trained row". The aim of this study was to determine whether GAD67-positive puncta (boutons) are affected by learning. Unbiased optical disector counting was applied to sections from the mouse barrel cortex that had been immunostained using a polyclonal antibody against GAD67. Quantification of the numerical density of GAD67-positive boutons was performed for four groups of mice: those that had been given aversive conditioning, pseudoconditioned mice with random application of the unconditioned stimulus, mice that had received only whisker stimulation, and naive animals. This study is the first to demonstrate that learning-dependent modification of mature somatosensory cortex is associated with a 50% increase in GAD67-positive boutons in the hollows of "trained" barrels compared with those of control barrels. Sensory learning seems to mobilize the activity of the inhibitory transmission system in the cortical region where plastic changes were previously detected by 2DG labeling.
Afferent Pathways↗
The influence of intentional and incidental learning on acquiring spatial knowledge during navigation.
In order to study the influence of intentional and incidental learning conditions on route learning, young adults walked a route through a university building. Half of the participants focused their attention on the route (intentional learning condition), while the other half did not (incidental learning condition). Five tests of spatial knowledge were employed: a route-length-estimation, landmark recognition, landmark ordering, map-drawing and navigation task. The intentional group performed better than the incidental group on the map-drawing and navigation task. No difference between the intentional and incidental group was found on the landmark-recognition and landmark-ordering task. Moreover, the intentional group overestimated the walking distance, while the incidental group underestimated it. These results suggest that route knowledge (landmark recognition and landmark ordering) requires less effortful processing than survey knowledge (developing a map-like representation and actual navigation).
Adult↗
Précis of How children learn the meanings of words.
Normal children learn tens of thousands of words, and do so quickly and efficiently, often in highly impoverished environments. In How Children Learn the Meanings of Words, I argue that word learning is the product of certain cognitive and linguistic abilities that include the ability to acquire concepts, an appreciation of syntactic cues to meaning, and a rich understanding of the mental states of other people. These capacities are powerful, early emerging, and to some extent uniquely human, but they are not special to word learning. This proposal is an alternative to the view that word learning is the result of simple associative learning mechanisms, and it rejects as well the notion that children possess constraints, either innate or learned, that are specifically earmarked for word learning. This theory is extended to account for how children learn names for objects, substances, and abstract entities, pronouns and proper names, verbs, determiners, prepositions, and number words. Several related topics are also discussed, including naïve essentialism, children's understanding of representational art, the nature of numerical and spatial reasoning, and the role of words in the shaping of mental life.
Child Language↗
Healthy living in Nunavut: an on-line nutrition course for inuit communities in the Canadian arctic.
OBJECTIVES: It is recognized that empowerment of Indigenous Peoples through training and education is a priority. The objective was to design a course that would provide an innovative training approach to targeted workers in remote communities and enhance learning related to the Nunavut Food Guide, traditional food and nutrition, and diabetes prevention. STUDY DESIGN: A steering committee was established at the outset of the project with representation from McGill University and the Government of Nunavut (including nutritionists, community nurses and community health representatives (CHRs), as well as with members of the target audience. Course content and implementation, as well as recruitment of the target audience, were carried out with guidance from the steering committee. METHODS: An 8-week long course was developed for delivery in January - March, 2004. Learning activities included presentation of the course content through stories, online self-assessment quizzes, time-independent online discussions and telephone-based discussions. Invitations were extended to all prenatal nutrition program workers, CHRs, CHR students, home-care workers, Aboriginal Diabetes Initiative workers and public health nurses in Nunavut. RESULTS: Ninety-six health-care workers registered for Healthy Living in Nunavut, with 44 actively participating, 23 with less active participation and 29 who did not participate. CONCLUSIONS: Despite having to overcome numerous technological, linguistic and cultural barriers, approximately 40% of registrants actively participated in the online nutrition course. The internet may be a useful medium for delivery of information to target audiences in the North.
Arctic Regions↗
Material-specific long-term memory representations of faces and spatial positions: evidence from slow event-related brain potentials.
Motivated by models that propose material-specific cortical long-term memory representations we expected different topographies of event-related slow waves of the EEG during cued retrieval of two distinct types of information (faces and spatial positions), which are assumed to be processed and stored in topographically distinct cortical areas, i.e., in either the ventral or the dorsal visual pathway. Seventeen participants learned associations either between words and spatial positions or between words and faces. Each word was associated with either one or two positions or faces. In a cued recall test, one day later, participants saw two words and had to decide whether these were linked to each other via an associated spatial position or a face. Slow event-related potentials (ERPs) of the EEG were recorded from 61 scalp electrodes during both acquisition and recall. Response times increased monotonically with the number of faces and positions to be reactivated. Negative slow ERPs showed a comparable topography during anticipation learning and cued recall, but dissociated topographically for positions and faces. The maximum of the negativity increased when items were presented repetitively (compared to the first presentation) during learning, and also with the number of the to-be-reactivated associations during retrieval. These results are consistent with an information-processing model that assumes material-specific cortical representations of episodic memory contents, which are established as localized cortical cell assemblies during encoding, and which are being reactivated during recall.
Adult↗
Plastic cortical changes induced by learning to communicate with non-speech sounds.
With Morse code, an acoustic message is transmitted using combinations of tone patterns rather than the spectrally and temporally complex speech sounds that constitute the spoken language. Using MEG recordings of the mismatch negativity (MMN, an index of permanent auditory cortical representations of native language speech sounds), we probed the dominant hemisphere for the developing Morse code representations in adult Morse code learners. Initially, the MMN to the Morse coded syllables was, on average, stronger in the hemisphere opposite to the one dominant for the MMN to native language speech sounds. After a training period of 3 months, the pattern reversed, however: the mean Morse code MMN became lateralized to the hemisphere that was predominant for the speech-sound MMN. This suggests that memory traces for the Morse coded acoustic language units develop within the hemisphere that already accommodates the permanent traces for natural speech sounds. These plastic changes manifest, presumably, the close associations formed between the neural representations of the tone patterns and phonemes.
Acoustic Stimulation↗
From basis functions to basis fields: vector field approximation from sparse data.
Recent investigations (Poggio and Girosi 1990b) have pointed out the equivalence between a wide class of learning problems and the reconstruction of a real-valued function from a sparse set of data. However, in order to process sensory information and to generate purposeful actions living organisms must deal not only with real-valued functions but also with vector-valued mappings. Examples of such vector-valued mappings range from the optical flow fields associated with visual motion to the fields of mechanical forces produced by neuromuscular activation. In this paper, I discuss the issue of vector-field processing from a broad computational perspective. A variety of vector patterns can be efficiently represented by a combination of linearly independent vector fields that I call "basis fields". Basis fields offer in some cases a better alternative to treating each component of a vector as an independent scalar entity. In spite of its apparent simplicity, such a component-based representation is bound to change with any change of coordinates. In contrast, vector-valued primitives such as basis fields generate vector field representations that are invariant under coordinate transformations.
Animals↗
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↗
Injury- and use-related plasticity in the primary sensory cortex of adult mammals: possible relationship to perceptual learning.
1. Restricted cochlear lesions in adult animals result in a reorganization of auditory cortex such that the cortical region deprived of its normal input by the lesion is occupied by expanded representations of adjacent cochlear loci (and thus of the frequencies represented at those loci). Analogous injury-induced reorganization is seen in somatosensory, visual and motor cortices of adult animals after restricted peripheral lesions. 2. Rather than constituting a central compensation for the peripheral loss, such reorganization appears to be an extreme form of changes in cortical organization that occur as a consequence of altered patterns of input such as arise from differential use of restricted regions of receptor surfaces ('use-related' reorganization). Thus, the frequency organization of auditory cortex is modified in animals trained to perform a frequency discrimination task and analogous changes in the frequency selectivity of cortical neurons are produced by classical conditioning procedures. 3. Recent evidence from the visual system suggests that changes similar to those involved in injury- and use-related cortical reorganization may underlie some forms of what has been called 'perceptual learning', the improvement in sensory/ perceptual discriminative performance with practice. Some forms of such learning are highly specific to the particular stimuli used in training (i.e. do not generalize to other stimuli), suggesting that the improved performance reflects a change in neural circuitry at a relatively early level of sensory processing. The limited available evidence supports the occurrence of such learning in the auditory system. 4. Recent studies using functional imaging and related techniques indicate that injury- and use-related reorganization occurs in human sensory and motor cortex.
Animals↗
Hippocampal place cells can develop distinct representations of two visually identical environments.
The pattern separation ability of hippocampal place cells was tested in an environment in which two visually identical rectangular compartments (Box A and Box B) were connected by a hidden door. Small ensembles of neurons were recorded with tetrodes while the rat searched for randomly distributed loci for reinforcing brain stimulation. The first recording session in Box A was conducted after the rat had explored the environment for the first time for 30 min. Immediately thereafter, a hidden door between Box A and Box B was opened to let the rat into the unexplored compartment, and a 5-min recording session was run with the door concealed. A rearrangement of place fields in Box B was observed in 18/20 neurons and in 5/6 ensembles. Most place fields did not change between two successive sessions in Box B. When the rat returned to Box A, the ensembles of neurons were as likely to adopt the original Box A firing field pattern as the more recent Box B pattern. In order to control for the influence of extra-arena cues, the rat was gradually lifted in a closed bucket from Box A into Box B while the whole arena was rotated by 90 degrees. All but one neuron and all the ensembles followed the intra-arena cues. Both rotated Box B and Box A firing field patterns were represented but Box B pattern was stronger among the neuronal ensembles. These findings indicate that hippocampal place cells not only can develop distinct representations of two visually identical environments but also can selectively reactivate either one of these representations depending on the rat's recent experience.
Animals↗
Task-specific recruitment of dorsal and ventral visual areas during tactile perception.
Many studies have found that visual cortical areas are active during tactile perception. Here we used positron emission tomographic (PET) scanning in normally sighted humans to show that extrastriate cortical regions are recruited in a task-specific manner during perceptual processing of tactile stimuli varying in two dimensions. Mental rotation of tactile Forms activated a focus around the anterior part of the left intraparietal sulcus. Since prior studies have reported activity nearby during mental rotation of visual stimuli, this focus appears to be associated with the dorsal visual (visuospatial) pathway. Discrimination between tactile Forms activated the right lateral occipital complex, an object-selective region in the ventral visual (visual Form) pathway. Thus, tactile tasks appear to recruit cortical regions that are active during corresponding visual tasks. Activation of these areas in both visual and tactile tasks could reflect visual imagery during tactile perception, activity in multisensory representations, or both.
Adult↗
On cross-modal similarity: the perceptual structure of pitch, loudness, and brightness.
Examined how pitch and loudness correspond to brightness. In the Experiment 1, 16 Ss identified which of 2 lights more resembled each of 16 tones; in Experiment 2, 8 of the same 16 Ss rated the similarity of lights to lights, tones to tones, and lights to tones. (1) Pitch and loudness both contributed to cross-modal similarity, but for most Ss pitch contributed more. (2) Individuals differed as to whether pitch or loudness contributed more; these differences were consistent across matching and similarity scaling. (3) Cross-modal similarity depended largely on relative stimulus values. (4) Multidimensional scaling revealed 2 perceptual dimensions, loudness and pitch, with brightness common to both. A simple quantitative model can describe the cross-modal comparisons, compatible with the view that perceptual similarity may be characterized through a malleable spatial representation that is multimodal as well as multidimensional.
Attention↗
Temporally graded, context-specific retrograde amnesia and its alleviation by context preexposure: effects of postconditioning exposures to morphine in the rat.
Five experiments studied retrograde impairments in Pavlovian fear conditioning following prolonged exposure to the opioid receptor agonist morphine. Injections of morphine commencing 1-7 days but not 14 days after conditioning produced amnesia for that conditioning episode. This amnesia was (a) selective such that morphine impaired freezing to the conditioning context but not to the auditory conditioned stimulus, (b) independent of the interval between the last injection of morphine and test, and (c) accompanied by a failure of contextual discrimination. Context preexposure protected context conditioning and discrimination from the amnestic effects of morphine. These results show that retrograde deficits in contextual fear conditioning are mediated by failures to consolidate a contextual representation.
Acoustic Stimulation↗
Perceptual representation as a mechanism of lexical ambiguity resolution: An investigation of span and processing time.
In 2 experiments, the authors investigated the ability of high- and low-span comprehenders to construe subtle shades of meaning through perceptual representation. High- and low-span comprehenders responded to pictures that either matched or mismatched a target object's shape as implied by the preceding sentence context. At 750 ms after hearing the sentence describing the target object, both high- and low-span comprehenders had activated a contextually appropriate perceptual representation of the target object. However, only high-span comprehenders had perceptually represented the contextually appropriate meaning immediately upon hearing the sentence, whereas low-span comprehenders required more processing time before the perceptual representation was activated. The results are interpreted in a framework of co-occurring lexical representations and perceptual-motor representations.
Aptitude↗
A study of the effect of structural information and familiarity in form perception.
Two experiments were carried out to investigate the influence of structural information and familiarity on the processing of visual forms. Pairs of "well" structured and nameable and "poorly" structured and non-nameable fragmented forms were employed as stimuli. The effects of structure and familiarity were assessed by manipulating the visual hemifield of presentation and the task. In Experiment 1 stimuli were judged as being either in the same orientation or mirror-reversed, a task that does not require high-level semantic information to be processed. Experiment 2 required physically identical forms to be matched, which may use either physical or name information. In Experiment 1 "same" judgements were equivalent for both types of stimuli, and "different" judgements were longer for the "poorly" structured (non-nameable) forms. In Experiment 2 there was little overall difference between "well" and "poorly" structured forms, though response times to "well" structured (nameable) forms were slowed for right-visual-field presentations. It is suggested that familiarity may not be sufficient to provide a perceptual advantage for nameable forms, as the advantage for nameable stimuli was confined to "same" judgements in Experiment 1 and response times were shorter for non-nameable stimuli in Experiment 2. Rather, performance depends upon factors such as the computation of global shape (due to structural properties of collinearity and closure) and on the use of different kinds or representations (physical versus name) in matching.
Adult↗
An integrate-and-fire model of prefrontal cortex neuronal activity during performance of goal-directed decision making.
The orbital frontal cortex appears to be involved in learning the rules of goal-directed behavior necessary to perform the correct actions based on perception to accomplish different tasks. The activity of orbitofrontal neurons changes dependent upon the specific task or goal involved, but the functional role of this activity in performance of specific tasks has not been fully determined. Here we present a model of prefrontal cortex function using networks of integrate-and-fire neurons arranged in minicolumns. This network model forms associations between representations of sensory input and motor actions, and uses these associations to guide goal-directed behavior. The selection of goal-directed actions involves convergence of the spread of activity from the goal representation with the spread of activity from the current state. This spiking network model provides a biological implementation of the action selection process used in reinforcement learning theory. The spiking activity shows properties similar to recordings of orbitofrontal neurons during task performance.
Action Potentials↗