Temporal processing deficits of language-learning impaired children ameliorated by training.

Children with language-based learning impairments (LLIs) have major deficits in their recognition of some rapidly successive phonetic elements and nonspeech sound stimuli. In the current study, LLI children were engaged in adaptive training exercises mounted as computer "games" designed to drive improvements in their "temporal processing" skills. With 8 to 16 hours of training during a 20-day period, LLI children improved markedly in their abilities to recognize brief and fast sequences of nonspeech and speech stimuli.

Language comprehension in language-learning impaired children improved with acoustically modified speech.

A speech processing algorithm was developed to create more salient versions of the rapidly changing elements in the acoustic waveform of speech that have been shown to be deficiently processed by language-learning impaired (LLI) children. LLI children received extensive daily training, over a 4-week period, with listening exercises in which all speech was translated into this synthetic form. They also received daily training with computer "games" designed to adaptively drive improvements in temporal processing thresholds. Significant improvements in speech discrimination and language comprehension abilities were demonstrated in two independent groups of LLI children.

A comparison of two radiographic assessment protocols for patients with periodontal disease.

OBJECTIVE: Radiographic assessment of patients with generalised severe periodontitis may be undertaken with a panoramic view and supplementary periapicals. The purpose of this study was to estimate the effective radiation dose from this form of radiographic assessment, and to compare it with an estimate of the dose from a series of periapicals of all the affected teeth. DESIGN: Cross-sectional observational study. SETTING: Departments of Periodontology and Radiology, Glasgow Dental Hospital and School. METHOD: Fifty consecutive patients [were recruited] with sufficiently widespread advanced periodontitis to require at least seven periapical radiographs. [Following new local guidelines, a panoramic view was taken.] The adequacy of the image of every affected tooth and the number of supplementary periapicals required was determined by a panel of four examiners who also calculated the number of periapicals which would have been taken if panoramic radiography had not been available. An effective dose of 0.001 mSv for one periapical and 0.007 mSv for a panoramic view was assumed. RESULTS: The panoramic-plus-periapicals approach delivered an estimated additional effective dose to 86% of patients, in the order of 0.001-0.007 mSv. CONCLUSIONS: Within the parameters of this investigation, the anticipated effective radiation dose from a series of periapical radiographs of all selected teeth would, for the great majority of patients, have been less than the dose from a panoramic-plus-periapicals approach.

Anesthetic state does not affect the map of the hand representation within area 3b somatosensory cortex in owl monkey.

Receptive fields defined for small clusters of neurons within the middle cortical layers of area 3b differed little in size or in the skin locations represented among: alert, nitrous oxide-anesthetized, deep sodium pentobarbital-anesthetized, and ketamine-anesthetized owl monkeys. Repeated recordings from nearly identical cortical loci yielded nearly identical multi-unit receptive fields under different conditions of anesthesia.

Variability in hand surface representations in areas 3b and 1 in adult owl and squirrel monkeys.

Detailed microelectrode maps of the hand representation were derived in cortical areas 3b and 1 from a series of normal adult owl and squirrel monkeys. While overlap relationships were maintained, and all maps were internally topographic, many map features varied significantly when examined in detail. Variable features of the hand representations among different monkeys included a) the overall shapes and sizes of hand surface representations; b) the actual and proportional areas of representations of different skin surfaces and the cortical magnifications of representations of specific skin surfaces, which commonly varied severalfold in area 3b and manyfold in area 1; c) the topographic relationships among skin surface representations, with skin surfaces that were represented adjacently in some monkeys represented in locations many hundreds of microns apart in others; d) the internal orderliness of representations; e) the completeness of representations of the dorsal hand surfaces; and f) the skin surfaces represented along the borders of the hand representation. Owl monkey maps were, in general, internally more strictly topographic than squirrel monkey maps. In both species, area 3b was more strictly topographic and less variable than was area 1. The degree of individual variability revealed in these experiments is difficult to reconcile with the hypothesis that details of cortical maps are ontogenetically specified during a period in early life. Instead, we propose that differences in the details of cortical map structure are the consequence of individual differences in lifelong use of the hands. This conclusion is consistent with earlier studies of the consequences of peripheral nerve transection and digital amputation, which revealed that cortical maps are dynamically maintained and are alterable as a function of use or nerve injury in these monkeys (Merzenich et al., '83a,b, '84a; Merzenich, '86; Jenkins et al., '84; Jenkins and Merzenich, '87).

A primate genesis model of focal dystonia and repetitive strain injury: I. Learning-induced dedifferentiation of the representation of the hand in the primary somatosensory cortex in adult monkeys.

In this study we tested a neuroplasticity/learning origins hypothesis for repetitive strain injuries (RSIs), including occupationally induced focal dystonia. Repetitive movements produced in a specific form and in an appropriate behavioral context cause a degradation of the sensory feedback information controlling fine motor movements, resulting in the "learned" genesis of RSIs. Two adult New World owl monkeys were trained at a behavioral task that required them to maintain an attended grasp on a hand grip that repetitively and rapidly (20 msec) opened and closed over short distances. The monkeys completed 300 behavioral trials per day (1,100 to 3,000 movement events) with an accuracy of 80 to 90%. A movement control disorder was recorded in both monkeys. Training was continued until the performance accuracy dropped to below 50%. We subsequently conducted an electrophysiologic mapping study of the representations of the hand within the primary somatosensory (SI) cortical zone. The hand representation in the true primary somatosensory cortical field, SI area 3b, was found to be markedly degraded in these monkeys, as characterized by (1) a dedifferentiation of cortical representations of the skin of the hand manifested by receptive fields that were 10 to 20 times larger than normal, (2) the emergence of many receptive fields that covered the entire glabrous surface of individual digits or that extended across the surfaces of two or more digits, (3) a breakdown of the normally sharply segregated area 3b representations of volar glabrous and dorsal hairy skin of the hand, and (4) a breakdown of the local shifted-overlap receptive field topography of area 3b, with many digital receptive fields overlapping the fields of neurons sampled in cortical penetrations up to more than four times farther apart than normal. Thus, rapid, repetitive, highly stereotypic movements applied in a learning context can actively degrade cortical representations of sensory information guiding fine motor hand movements. This cortical plasticity/learning-based dedifferentiation of sensory feedback information from the hand contributes to the genesis of occupationally derived repetitive strain injuries, including focal dystonia of the hand. Successful treatment of patients with RSI will plausibly require learning-based restoration of differentiated representations of sensory feedback information from the hand.

Neocortical representational dynamics in adult primates: implications for neuropsychology.

Some evidence for functional reorganization of cortical somatosensory representations in adult primates is reviewed. These examples include representation remodeling in cortical area 3b following digit amputation, digit fusion, local intracortical microstimulation, restricted cortical lesions, or as a consequence of behaviorally controlled stimulation of restricted hand surfaces. We suggest that the profound changes in the cortical representations that have been observed after these and other manipulations must bear consequences for the specific behaviors that depend on the operation of this neural machinery. Furthermore, this lifelong dynamic cortical capacity for neuronal response adaptation by use almost certainly also underlies the progressive representational remodeling that we have recorded following brain lesions.

Experience-induced plasticity of cutaneous maps in the primary somatosensory cortex of adult monkeys and rats.

In a first study, the representations of skin surfaces of the hand in the primary somatosensory cortex, area 3b, were reconstructed in owl monkeys and squirrel monkeys trained to pick up food pellets from small, shallow wells, a task which required skilled use of the digits. Training sessions included limited manual exercise over a total period of a few hours of practice. From an early clumsy performance in which many retrieval attempts were required for each successful pellet retrieval, the monkeys exhibited a gradual improvement. Typically, the animals used various combinations of digits before developing a successful retrieval strategy. As the behavior came to be stereotyped, monkeys consistently engaged surfaces of the distal phalanges of one or two digits in the palpation and capture of food pellets from the smallest wells. Microelectrode mapping of the hand surfaces revealed that the glabrous skin of the fingertips predominantly involved in the dexterity task was represented over topographically expanded cortical sectors. Furthermore, cutaneous receptive fields which covered the most frequently stimulated digital tip surfaces were less than half as large as were those representing the corresponding surfaces of control digits. In a second series of experiments, Long-Evans rats were assigned to environments promoting differential tactile experience (standard, enriched, and impoverished) for 80 to 115 days from the time of weaning. A fourth group of young adult rat experienced a severe restriction of forepaw exploratory movement for either 7 or 15 days. Cortical maps derived in the primary somatosensory cortex showed that environmental enrichment induced a substantial enlargement of the cutaneous forepaw representation, and improved its spatial resolution (smaller glabrous receptive fields). In contrast, tactile impoverishment resulted in a degradation of the forepaw representation that was characterized by larger cutaneous receptive fields and the emergence of non-cutaneous responses. Cortical maps derived in the hemispheres contralateral to the immobilized forelimb exhibited a severe decrease of about 50% in the overall areal extent of the cutaneous representation of the forepaw, which resulted from the invasion of topographically organized cortical zones of non-cutaneous responses, and numerous discontinuities in the representation of contiguous skin territories. The size and the spatial arrangement of the cutaneous receptive fields were not significantly modified by the immobilization of the contralateral forelimb. Similar results were obtained regardless of whether the forelimb restriction lasted 7 or 15 days. These two studies corroborate the view that representational constructs are permanently reshaped by novel experiences through dynamic competitive processes. These studies also support the notion that subject-environment interactions play a crucial role in the maintenance of basic organizational features of somatosensory representations.

Vibrissal roughness discrimination is barrelcortex-dependent.

We have investigated the contribution of the neocortical vibrissal representation within the posterior medial barrel subfield (PMBSF) to the high performance levels obtained by rats in a complex roughness discrimination task mediated by vibrissal inputs. Nine binocularly occluded rats were trained in a two-choice roughness discrimination until they obtained the 85% correct response criteria. Subsequently, the PMBSF was localized by electrophysiological recordings and bilaterally ablated. The locus and extent of the cortical lesions were confirmed by histological analysis after additional training and testing. There was no evidence of task retention after the cortical lesion and barrelless rats were unable to obtain prelesion discriminative performance levels when stimulation was restricted solely to vibrissal cues. After extensive postlesion training, four of these rats were allowed to palpate the discriminanda with their forepaws. Under these conditions rats rapidly reached the 85% correct criterion once again. The present results indicate that the PMBSF is essential for complex tactile discrimination when sensory information is obtained through the vibrissae by active palpation. This deficit is specific for the vibrissal system, the PMBSF is not essential to solve the same tactile discrimination task when the source of the somatosensory information is provided by other non-vibrissal cutaneous sensory receptors.

Development of a computerized system for simultaneous visual discrimination in rats.

In order to automate a simultaneous visual discrimination system, a Sutherland jumping-stand box was modified by adding two lateral alleys which connect the feeder compartment with the starting box. By means of a digital interface, this modified box was connected to an Apple IIe PC. A group of rats (n = 8) was trained. All subjects learned. Advantages relevant to the apparatus design, as well as the benefits derived from the automated procedure are discussed.

Age-dependent capacity for somatosensory cortex reorganization in chronic spinal cats.

Primary somatosensory cortex was mapped in chronic spinal cats that were spinalized (T12) at two weeks and 6 weeks of age. The magnitude of cortical reorganization is age-dependent. In cats spinalized at two weeks, extensive reorganization of the deafferented hindlimb region resulted in a second complete map of intact tactile input from the trunk and forelimb, while in cats transected at 6 weeks of age, trunk afferent input only partially activated the deafferented hindlimb region.

Formation of interdental soft tissue defects after surgical treatment of periodontitis.

This study monitored the development and repair of interdental soft tissue defects following surgical treatment of periodontitis in 21 patients. Open flap curettage was performed at 100 interdental areas with follow-up examinations 1, 3, and 6 months later. Interdental gingival contours were assessed both clinically and indirectly with silicone elastomer impressions from which stone models were obtained; defect depths were then calculated using the Reflex Microscope. Two types of defect were identified at the 1-month follow-up: 13 interdental clefts (mean depth, 1.8 mm); and 30 craters, (mean depth, 1.6 mm). Although clefts tended to persist, craters showed a strong tendency to repair. Thus, at the 6-month follow-up, the depths of clefts and craters were 1.3 mm and 0.7 mm respectively. The development of soft tissue defects did not appear to be related to the use of a periodontal dressing nor did the existence of an underlying bone defect appear to be of etiological importance. Pre-operative probing depths, however, were positively associated with the occurrence of soft tissue craters (P = 0.02). Pre-operatively, the overall mean probing depth and frequency of bleeding on probing were 5.3 mm and 100% respectively. At 6 months, these values were reduced to 2.0 mm and 22%. When clefts, craters, and interdental areas with no soft tissue defect were compared, no significant differences in probing depth reduction or frequency of bleeding were observed at any time point.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative efficacy of the standard flossing procedure and a new floss applicator in reducing interproximal bleeding: a short-term study.

This was a parallel stratified study which examined the effect on gingival health of a new floss holder and applicator, designed to deliver a 25 microliters dose of 0.1% chlorhexidine solution to each interdental embrasure during the flossing procedure. Fifty-two patients with simple chronic gingivitis were stratified according to age, sex, and baseline interdental bleeding score and then assigned to one of three treatment groups. One of the following interdental cleaning agents was used once daily during a 2-week period: conventional floss; a flossing device with chlorhexidine; or a flossing device with placebo solution. Gingival health was assessed using the interdental bleeding index (IBI); i.e., the ratio of bleeding sites to the number of sites tested by stimulation with an interdental cleaner. The percentage reduction in bleeding amounted to 38.3% for conventional floss, 51.5% for the flossing device with chlorhexidine, and 51.4% for the flossing device with placebo. The reductions in both flossing device groups were significantly greater than that of the conventional floss group as determined by one-way ANOVA (F = 4.0; P = 0.024) and multiple range tests. There were no statistically significant differences between the two flossing device groups. There was no difference in patients' perception of ease of use of their respective materials; however, 72% of chlorhexidine users and 94% of placebo users, but only 24% of conventional floss users, felt that their interdental cleaning regimens left their mouths feeling fresher. It is therefore postulated that the pleasant tasting spray may have been an important stimulus to extended use of the new device and may explain its greater effectiveness.

Histopathological and ultrastructural findings in a case of Papillon-Lefèvre syndrome.

Gingiva from a 3-year-old Iranian boy suffering from Papillon-Lefèvre syndrome was examined by light and electron microscopy. Deep pockets associated with predominantly Gram-negative plaque were present. The gingival lesion was dominated by plasma cells, many of which were degenerate. Russell bodies were a prominent feature. No defect of epithelium was detected.

A primate model for studying focal dystonia and repetitive strain injury: effects on the primary somatosensory cortex.

BACKGROUND AND PURPOSE: Job-related repetitive strain injuries (RSIs) are increasing, and current treatment strategies often fail to return injured people to work. This study documented the neural consequences of using two different movement strategies for active, repetitive hand closing and opening. METHODS: Two owl monkeys were trained for 20 weeks to repetitively close a handpiece against an 80-g force (3-400 trials per day, training at 80%-90% accuracy). One monkey used a highly articulated hand-squeezing strategy, and the other monkey used a proximal arm-pulling strategy. Changes in motor performance were analyzed, and the electrophysiological maps of the hand representation on the trained primary sensory cortex (area 3b) were compared with those of untrained control animals and the untrained sides of the trained monkeys. RESULTS: The monkey using the articulated hand-squeezing strategy showed motor deterioration and dedifferentiation of the normally sharply segregated areas of the hand representation in area 3b. Mild degradation of the hand representation was measured in the monkey using the proximal arm-pulling strategy, but there was no motor dysfunction. CONCLUSION AND DISCUSSION: Attended, highly articulated, repetitive finger squeezing degrades the hand representation and interferes with motor control. A proximal, more variable repetitive strategy minimized the sensory degradation and preserved motor control. Restoring the hand representation may be a critical part of treatment for patients with chronic RSI and focal hand dystonia.

Cochlear implantation in children: the problem of head growth.

Successful implantation in children requires that provision be made for later head growth. The timing and magnitude of this growth was determined by measurements made from high-resolution computerized tomographic images of developing temporal bones. The temporal bone scans of 103 children of varying ages were studied. The development of the petrous and squamous portion of the temporal bone was at its greatest in the first 2 years of life. The order of magnitude of growth varied with the different axes measured.

Cross-sectional assessment of caries and periodontitis risk within the same subject.

Dental caries and chronic periodontitis may be synergistically associated, negatively associated, or completely independent. The present report examines this relationship by comparing the susceptibility to chronic periodontitis and caries within the same individual. From an 800-patient sample, a periodontitis risk score was derived by radiographic assessment of bone loss in quarters of optimum bone height and obtaining for each subject a mean score based on all measurable surfaces. Similarly the caries risk was determined radiographically from the total decayed and filled teeth (DFT), as a percentage of the total teeth measured. The Mantel-Haenszel technique was used for analysis of the relationship between periodontitis and caries and data was stratified on four categories of age, sex, and numbers of teeth present. This analysis revealed no systematic patterns, indicating that the risks of caries and periodontal diseases are unrelated (chi 2 = 0.00; 1 df; P greater than 0.50). In addition, a regression analysis, which was controlled for sex and age, indicated a marked lack of association between caries and periodontitis (P = 0.94). Thus, although these common diseases share putative etiologic factors such as oral hygiene practices and dental attendance pattern, the major risk factors are probably quite different.

Cervical marginal fit of proximal amalgam restorations.

This study investigated the relationship between the adaptation, apical location and gap width of the cervical margin of proximal amalgam restorations. Three hundred and seventeen proximal cervical margins were studied in 243 extracted teeth. The restorations were categorized as 'flush fitting'; 'small overhang', or 'large overhang', based on examination with a Cross calculus probe. After trimming the overhangs to make the restorations flush with the tooth surface, the gap width was measured. In addition, the location of the cavity margin was measured relative to the amelocemental junction (ACJ), and the data were further grouped according to whether the restoration finished apical to the ACJ, less than 1.5 mm coronal to it, or more than 1.5 mm coronal to it. All measurements were made with a Reflex Microscope. Analysis of variance with the Scheffé multiple range test indicated that: the mean gap width of large overhanging restorations was significantly greater than that of small overhanging or flush fitting restorations (P < 0.001); the mean gap width of restorations which finished on the root surface was significantly greater than that of those restorations which finished on the enamel surface at more than 1.5 mm from the ACJ (P < 0.002); and large overhanging restorations were located further apically than small overhanging restorations which were, in turn, located further apically than flush fitting restorations (P < 0.0001). Furthermore, discriminant analysis indicated that the location of the cervical margin had more influence on gap width than the presence of an overhang (R2 = 3.6%; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The reasons for the extraction of various tooth types in Scotland: a 15-year follow up.

OBJECTIVES: The aim of this survey was to investigate the reasons for extraction of the various tooth types in Scotland. This study replicated one which was undertaken 15 years earlier. A further aim, therefore, was to identify any changes in the frequency of extraction of each tooth type in the 15 years between the two studies. METHODS: The names of every fourth dentist on the list of the Scottish Dental Practice Board were obtained. Four hundred and twenty-five general dental practitioners were asked to record permanent tooth extractions for 1 week. Data requested for each extraction were: the patient's age, gender and dental attendance pattern, the type of tooth removed and the reason for the extraction. RESULTS: Three hundred and fifty-two dentists participated (a response rate of 82.8%). There were 25% fewer teeth extracted per patient and 30% fewer per dentist than in the 1984 study. In 1999, more teeth of most types were extracted from regular attenders whereas, in 1984, more teeth of all types were extracted from irregular attenders. Premolars and first and second molars were the tooth types most frequently extracted in both surveys. In 1999 premolars were the teeth most commonly removed below 21 years of age, accounting for 57.5% of extractions in this age range. Molars accounted for 33.8% of extractions in this age range compared with 52% in 1984. Overall, caries was found to be the principal reason for loss of all tooth types apart from lower incisors which were extracted mainly for periodontal reasons. However, below 21 years, 84.5% of premolar extractions were performed for orthodontic purposes. CONCLUSIONS: Over the last 15 years, the overall number of extractions has reduced and the proportion of extractions from regular attenders has increased. Proportionately more premolars and fewer molars were extracted from under-21-year-olds. This observation can be explained by an increase in orthodontic extractions or a decline in extractions for caries in this age group. However, when extractions from the population as a whole are considered, caries and its sequelae remains the principal reason for loss of all tooth types other than lower incisors which are extracted mainly for periodontal reasons.

The 'high risk' group in periodontitis.

The high risk concept of periodontitis incorporates the theory that multiple tooth loss from periodontal disease affects a relatively small proportion of the population. This paper reviews and extends the evidence for such a concept by describing the occurrence and distribution of advanced bone loss in a Glasgow population of 800 dental out-patients. In common with other published studies of attachment loss or periodontal bone destruction, advanced bone loss was highly prevalent, affecting 54.1% of 50- to 73-year-olds. However, in parallel with other investigations, a small but with age increasing minority of patients accounted for most of the bone destruction. For example, in the 50- to 73-year-old age group, 28% of patients accounted for 75% of the advanced bone loss seen in that group.