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PubMed1997

Representations of graphomotor trajectories in the human parietal cortex: evidence for controlled processing and automatic performance.

The aim of this study was to identify the cerebral areas activated during kinematic processing of movement trajectories. We measured regional cerebral blood flow (rCBF) during learning, performance and imagery of right-hand writing in eight right-handed volunteers. Compared with viewing the writing space, increases in rCBF were observed in the left motor, premotor and frontomesial cortex, and in the right anterior cerebellum in all movement conditions, and the increases were related to mean tangential writing velocity. No rCBF increases occurred in these areas during imagery. Early learning of new ideomotor trajectories and deliberately exact writing of letters both induced rCBF increases in the cortex lining the right intraparietal sulcus. In contrast, during fast writing of overlearned trajectories and in the later phase of learning new ideograms the rCBF increased bilaterally in the posterior parietal cortex. Imagery of ideograms that had not been practised previously activated the anterior and posterior parietal areas simultaneously. Our results provide evidence suggesting that the kinematic representations of graphomotor trajectories are multiply represented in the human parietal cortex. It is concluded that different parietal subsystems may subserve attentive sensory movement control and whole-field visuospatial processing during automatic performance.

Adult↗
PubMed1994

Effect of visual experience on locational judgements after perspective change in small-scale space.

Congenitally blind, late blind and blindfold sighted adults overlearned an object-array within a square frame by touch, and judged, facing the midpoint of the frame, the near/far/left/right locations of objects from sides and diagonally from corners. One-half were first guided to points (A-condition), the rest were first asked to imagine themselves as being at points (I-condition). Group and condition did not, but group and observation point did, interact. Lack of visual experience added to RTs and total times and increased errors especially at diagonal stations. Congenitally blind subjects differed from both late blind and blindfold sighted subjects. However, a section of the congenitally blind subjects attained the level of blindfold sighted subjects. The sequence A-I speeded up judgements in all groups. Group did not interact with size of space. Congenitally blind subjects reportedly resorted to holistic representations, but had specific limitations in using them at diagonal stations. Orientation skills of the congenitally blind in far space could be improved by practising perspective taking in near space.

Adult↗
PubMed1991

Do older people know how good they are?

Information and procedures that have been overlearned during a lifetime form a body of 'crystallized' intelligence that is relatively unaffected by ageing. Thus in spite of marked decrements in their 'fluid' memory abilities it is possible that older people may retain knowledge about the limitations and characteristics of their own memory ('metamemory'). To test whether efficiency of metamemory is, indeed, independent of age-related decline in fluid intelligence, 320 people aged from 50 to 79 years were asked to predict their probable performance on four simple memory tasks which had been carefully explained to them. They then experienced the tasks and their predictions were compared with their actual performances. Actual task performance was modestly predicted by chronological age and by AH 4 and Mill Hill IQ test scores but not by subjective self-ratings of everyday memory and cognitive efficiency (the Broadbent CFQ, and the Sunderland & Harris MQ). The data suggest that absolute levels of prediction of performance were associated with self-confidence and were best predicted by scores on the Beck depression scale and by fluid IQ test scores. There was also evidence that individuals with higher test scores gave more accurate as well as more optimistic predictions of their own abilities. Taken together these results suggest that the accuracy of individuals' assessments of their own abilities does alter with age-related changes in fluid IQ, but probably more radically by age-related changes in self-regard and in life-style.

Activities of Daily Living↗
PubMed1983

Retrieval of information from long-term memory.

Information is represented in long-term memory as a network of associations among concepts. Information is retrieved by spreading activation from concepts in working memory through the network structure. The time required to retrieve information is a function of the level of activation that it achieves. Fanning of multiple paths from a node dissipates the activation the node sends down any path and increases retrieval time. Fan effects are reduced as subjects overlearn the material or when they can change their task from a recognition judgment to a consistency judgment.

Face↗
PubMed1997

Anatomy of motor learning. I. Frontal cortex and attention to action.

We used positron emission tomography to study new learning and automatic performance in normal volunteers. Subjects learned sequences of eight finger movements by trial and error. In a previous experiment we showed that the prefrontal cortex was activated during new learning but not during during automatic performance. The aim of the present experiment was to see what areas could be reactivated if the subjects performed the prelearned sequence but were required to pay attention to what they were doing. Scans were carried out under four conditions. In the first the subjects performed a prelearned sequence of eight key presses; this sequence was learned before scanning and was practiced until it had become overlearned, so that the subjects were able to perform it automatically. In the second condition the subjects learned a new sequence during scanning. In a third condition the subjects performed the prelearned sequence, but they were required to attend to what they were doing; they were instructed to think about the next movement. The fourth condition was a baseline condition. As in the earlier study, the dorsal prefrontal cortex and anterior cingulate area 32 were activated during new learning, but not during automatic performance. The left dorsal prefrontal cortex and the right anterior cingulate cortex were reactivated when subjects paid attention to the performance of the prelearned sequence compared with automatic performance of the same task. It is suggested that the critical feature was that the subjects were required to attend to the preparation of their responses. However, the dorsal prefrontal cortex and the anterior cingulate cortex were activated more when the subjects learned a new sequence than they were when subjects simply paid attention to a prelearned sequence. New learning differs from the attention condition in that the subjects generated moves, monitored the outcomes, and remembered the responses that had been successful. All these are nonroutine operations to which the subjects must attend. Further analysis is needed to specify which are the nonroutine operations that require the involvement of the dorsal prefrontal and anterior cingulate cortex.

Adult↗
PubMed1980

Lateral asymmetry in perceptual judgments of reading disabled, hyperactive and control children.

Three groups of 11 year old boys, classified as reading-disabled/hyperactive, hyperactive, and normal controls, made same-different judgments to pairs of verbal or visuospatial stimuli presented simultaneously to the right or left side of a fixation point. Two experimental paradigms were used, one emphasizing comparison judgments from memory, the other, new comparison judgments. Reading-disabled boys made more errors of judgment than did controls. All subjects exhibited faster reaction times for different judgments of pairs appearing in the left visual field. Reaction times were longer and errors more numerous for judgments made when two stimuli were presented simultaneously, one to each visual field. Differences in performance for the two halves of the visual field are attributed to memory storage effects for overlearned stimuli. The deficiency in interhemispheric comparisons is attributed to immaturity of the cerebral commissures. The reading-disabled group appears to encompass two subgroups with differing modes of information processing.

Child↗
PubMed1983

The lateralization of arithmetic and number processing: a review.

Calculation and number processing require ideographic and semantic operations which may involve the right as well as the left hemisphere. There is often also present a spatial component, whether overt as with column-addition or multiplication procedures, or covert if numbers are recoded into continuously varying analog quantities or magnitudes of a psychophysical or imaginal nature, to facilitate numerical comparison. Again right hemisphere mechanisms may be partly responsible. Evidence for such a minor hemisphere contribution is reviewed in the light of studies with clinical and commissurotomy cases, and normal subjects. Calculation itself is hard to define, as it often seems to reduce to the operation of overlearn, associative, tabular look-up functions and algorithms. Indeed alphabetic comparisons analogous to numerical tasks should generate similar laterality effects in clinical and normal populations.

Brain Damage, Chronic↗
PubMed1999

Cognitive processing speed in Lyme disease.

OBJECTIVE: The goal of this study was to more precisely define the nature of the cognitive processing deficits in the patients with Lyme disease. BACKGROUND: Lyme disease has been associated with cognitive disturbances. METHOD: Sixteen patients who met the Centers for Disease Control's case definition for Lyme disease and 15 age- and education-matched control subjects completed two computerized assessments. The first was a matching procedure that assessed perceptual/motor speed. The second task was an alphabet-arithmetic (AA) test that measured the speed of mental arithmetic. On the matching task, subjects judged as true or false simple identity equations (e.g., B + 0 = B). On the AA task, subjects indicated the veracity of equations of the same form as those of the matching task but which required mental arithmetic (e.g., A + 3 = D). The use of this paradigm permits sensory or motor slowing to be distinguished from slowed cognitive processing speed. Also, the tests do not involve automated or overlearned responses. RESULTS: Lyme disease patients and healthy controls did not differ in perceptual/motor speed. However, Lyme disease patients' response times were significantly longer than those of healthy controls during the AA task, demonstrating specific impairments in mental activation speed. CONCLUSIONS: These results suggest that Lyme disease patients show specific deficits when initiating a cognitive process. These impairments are independent of sensory, perceptual, or motor deficits.

Adult↗
PubMedDate not supplied

[Attention deficits and schizophrenia. Multidisciplinary approaches and the Stroop's test].

Since McGhie & Chapman's (1961) pioneering work, there have been continual attempts to clarify the link between attentional disturbances observable in schizophrenics and their schizophrenic symptoms. Venables (1964, 1977) claims that this diminution is a consequence of a badly controlled arousal, resulting in an inadequate filtering at the level of sensory input. Although the notion of a faulty sensory filter is simple and intellectually satisfying, this idea rapidly met with articulate opposition. Broadbent himself, in 1971, revised his model to take into account the way in which semantic aspects influence selective attention, and proposed the existence of a second stage of information processing, coming after the sensory filter. It became increasingly clear that progress in understanding selective attention would depend upon more centrally-directed approaches. In 1935, Stroop developed an ingenious way of studying selective attention. In his task, an "automatic", overlearned task (reading short words aloud) is put into conflict with a slightly more difficult task (colour-naming): the subject has to name the colour of the ink in which a word is printed, but the word itself is the name of a different colour. For instance, when the word "blue" is written in red ink, the correct response is "red". Typically, subjects find it difficult to inhibit the reading response, and take significantly more time to name a colour that forms an incompatible word than take to name the colour of a row of letters "x". This increased reaction time for the incompatible condition is attributed to an "interference" caused by the verbal information contained in the double stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Attention↗
PubMed1988

Syndromes in developmental dysphasia and adult aphasia.

We have attempted to draw some parallels between syndromes of adult acquired aphasia and of childhood developmental dysphasia. There appear to be two syndromes that are almost exact duplicates in the adults and the children: (a) pure word deafness and verbal auditory agnosia, and (b) aphemia and verbal dyspraxia. Two other syndromes seem to have rather close but not exact counterparts: Broca's aphasia and the phonologic-syntactic deficit syndrome, and transcortical sensory aphasia and the semantic-pragmatic deficit syndrome. There are two dysphasic syndromes, the phonologic production deficit syndrome and the lexical-syntactic deficit syndrome, that do not seem to have close adult counterparts. Neither of these dysphasic syndromes has been defined in adequate linguistic detail, and it is possible that their description may have to be modified when more data become available. Whether these comparisons between dysphasias and aphasias have heuristic value for guiding external validation studies of the clinically defined dysphasic syndromes of preschool children remains to be determined. Our purpose was to formulate hypotheses as to which cerebral systems are likely to be dysfunctional in children with clinically defined dysphasic syndromes. We recognize that the disorders of language acquisition and those of overlearned adult language have fundamental differences, and that plasticity of the child's developing brain introduces further complexities. Nevertheless, it seems reasonable to think that there are constants in brain organization that span all ages. Looking for language deficits common to aphasic adults (whose lesions can usually be delineated with contemporary neuroimaging techniques) and to dysphasic children (in whom there are rarely any neurologic clues) may be a fruitful way to begin to define the cerebral correlates of the children's deficits.

Adult↗
PubMed1985

Cognitive deficits in adolescents who developed diabetes early in life.

A comprehensive battery of neuropsychological tests was administered to 125 adolescents with a history of insulin-dependent diabetes, and to 83 demographically similar nondiabetic control subjects. To test the hypothesis that developing this disease early in life greatly increases the risk of manifesting significant cognitive impairments, diabetic subjects were assigned to an "early-onset" (diagnosis before age 5 years) or a "later-onset" subgroup. Results showed that subjects with early onset of diabetes performed more poorly than either subjects with later onset of diabetes or nondiabetic control subjects on virtually all tests, including measures of intelligence, school achievement, visuospatial ability, memory, motor speed, and eye-hand coordination. Moreover, multiple regression analyses demonstrated that the age at onset and the duration of diabetes seem to affect neuropsychological functioning in very different ways. The duration of the disease best predicted performance on those tests requiring highly overlearned, primarily verbal, skills whereas the age at onset best predicted scores on tests requiring the ability to process relatively unfamiliar, typically nonverbal, information in novel ways. Although the etiology of these deficits remains unclear, there is a possibility that they are secondary to mild brain damage that develops as a consequence of multiple episodes of serious hypoglycemia early in life.

Adolescent↗
PubMed1980

The role of tone height, melodic contour, and tone chroma in melody recognition.

The present experiments assessed the contribution of tone height, melodic contour, and tone chroma to melody recognition. Rather than using highly familiar folk songs as in earlier studies, subjects were taught new melodies. Novel melodies were used to (a) more precisely control potential cues (e.g., rhythm) that are not of present interest, (b) eliminate unison intervals that cannot be transformed appropriately, (c) provide a direct analysis of the nature of confusion errors, (d) test whether recently learned melodies are recognized differently than highly overlearned melodies, and (e) evaluate the extent to which practice in the experimental task alters the process of recognition. The results replicate previous studies using familiar folk songs. Transformations of the original melodies were accurately recognized when tone height was violated, but both melodic contour and tone chroma were maintained. Violating both tone height and contour while maintaining chroma produced extremely poor recognition. Performance was intermediate when just melodic contour was preserved. There is now good evidence to support the idea that melodic contour and tone chroma, in addition to tone height, contribute to recognition of both highly familiar and recently learned melodies.

Humans↗
PubMed1995

Mental acuity of the normal elderly.

The elderly are persons over age 65, now comprising 12% of our population. The normal elderly function normally both in their self care, and also in their social activities of daily living, which we tabulate. The current terms for the normally functioning elderly who show only mild psychological deficits are age-associated memory impairment and age-related cognitive decline, which we define, criticize and tabulate. The psychological deficits of the elderly consist of mild generalized slowing and inaccuracies compared to normal young persons. These deficits are measured by objective psychological tests which mimic real daily living situations--the name-face test, fire alarm test, two delayed recall tests, misplaced objects test, shopping list test, and digit symbol test, which we describe. A longer early formal education is preventive of mental dulling during normal aging. Treating using overlearning, by cognitive training, is significantly beneficial.

Activities of Daily Living↗
PubMed1994

Motor sequence learning: a study with positron emission tomography.

We have used positron emission tomography to study the functional anatomy of motor sequence learning. Subjects learned sequences of keypresses by trial and error using auditory feedback. They were scanned with eyes closed under three conditions: at rest, while performing a sequence that was practiced before scanning until overlearned, and while learning new sequences at the same rate of performance. Compared with rest, both sequence tasks activated the contralateral sensorimotor cortex to the same extent. Comparing new learning with performance of the prelearned sequence, differences in activation were identified in other areas. (1) Prefrontal cortex was only activated during new sequence learning. (2) Lateral premotor cortex was significantly more activated during new learning, whereas the supplementary motor area was more activated during performance of the prelearned sequence. (3) Activation of parietal association cortex was present during both motor tasks, but was significantly greater during new learning. (4) The putamen was equally activated by both conditions. (5) The cerebellum was activated by both conditions, but the activation was more extensive and greater in degree during new learning. There was an extensive decrease in the activity of prestriate cortex, inferotemporal cortex, and the hippocampus in both active conditions, when compared with rest. These decreases were significantly greater during new learning. We draw three main conclusions. (1) The cerebellum is involved in the process by which motor tasks become automatic, whereas the putamen is equally activated by sequence learning and retrieval, and may play a similar role in both. (2) When subjects learn new sequences of motor actions, prefrontal cortex is activated. This may reflect the need to generate new responses. (3) Reduced activity of areas concerned with visual processing, particularly during new learning, suggests that selective attention may involve depressing the activity of cells in modalities that are not engaged by the task.

Adult↗
PubMed1978

The effect of visual deprivation in the rat on transfer effects after form discrimination training.

In 3 experiments the performances of light-reared (LR) and dark-reared (DR) 90-day-old rats were compared on a variety of transfer tests following acquisition of 3 discriminations involving patterns of small squares (dots). Though no significant difference due to rearing condition was found in acquisition of those discriminations consisting of single lines of dots in various orientations, transfer tests did reveal subtle differences in the way LR and DR rats analyze contour information. Significant differences due to rearing were also observed on the acquisition of a complex dot pattern (gradient vs X) and, in spite of overtraining, on subsequent stimulus equivalence tests. Anomalous transfer effects were not observed in any of these test situations.

Animals↗
PubMed1975

Associative recall and formation of stable modes of activity in neural network models.

Models of neural networks with recurrent inhibition are studied, as well as one model which also includes recurrent excitation. The models are intended as possible descriptions of the cerebral cortex. Each network model is composed of neuron models called pyramidal cells and stellate cells in accordance with the names of two types of cells in the cortex. Inputs and outputs of the network are connected to the pyramidal cells while feedback is provided by the stellate cells. Connections within the network are random. During a learning phase the pyramidal cell excitatory synapses become facilitated according to a two-conditional facilitation rule. This is the basis of the model's ability for associative learning. The associative retrieval of information can be studied during a subsequent association phase. This has been done by simulation on a digital computer. It was shown that all of the models considered can be designed to perform a so-called decision-making function. This means that if the associating input pattern is similar to several patterns which occurred during learning the model can decide which similarity is greatest by responding with the appropriate associated pattern. The model also including recurrent excitation differs from the simpler models in that it can become stabilized in so-called stable modes of activity which are self-sustaining and remain even after the input has been turned off. Normally, only one stable mode can be active at a time. However, through careful choice of construction parameters it was possible to obtain a model in which a maximum of two stable modes could be activated independently of each other. Physiological and psychological interpretations are discussed and so are the limitations of the models, which are evident in certain situations.

Cerebral Cortex↗
PubMed1998

Neural network modeling of developmental effects in discrimination shifts.

This paper presents neural network simulations of developmental phenomena in discrimination shifts. The discrimination shift literature is reviewed in order to identify the empirical regularities. Leading theoretical accounts of the development of shift learning are reviewed, and the lack of a thorough account is highlighted. Recent unsuccessful neural network simulations of shift learning are also reviewed. New simulations, using the cascade-correlation algorithm, show that networks can capture the regularities of the discrimination shift literature better than existing psychological theories. Manipulation of the amount of training that networks receive, which affects depth of learning, simulates developmental phenomena. It is suggested that human developmental differences in shift learning arise from spontaneous overtraining by older participants, an interpretation consistent with the overtraining literature.

Adult↗