How is reading, a cultural invention, coded by neural populations in the human brain? The neural ... more How is reading, a cultural invention, coded by neural populations in the human brain? The neural code for written words must be abstract, because we can recognize words regardless of their location, font and size. Yet it must also be exquisitely sensitive to letter identity and letter order. Most existing coding schemes are insufficiently invariant or incompatible with the constraints of the visual system. We propose a tentative neuronal model according to which part of the occipito-temporal 'what' pathway is tuned to writing and forms a hierarchy of local combination detectors sensitive to increasingly larger fragments of words. Our proposal can explain why the detection of 'open bigrams' (ordered pairs of letters) constitutes an important stage in visual word recognition.
The aim of this study was to establish whether a patient-administered medical risk-related histor... more The aim of this study was to establish whether a patient-administered medical risk-related history (MRRH) for dental patients was valid. The MRRH, which was developed in the Netherlands, has now been tested in Belgium, where it was ...
Fast, parallel word recognition, in expert readers, relies on sectors of the left ventral occipit... more Fast, parallel word recognition, in expert readers, relies on sectors of the left ventral occipito-temporal pathway collectively known as the visual word form area. This expertise is thought to arise from perceptual learning mechanisms that extract informative features from the input strings. The perceptual expertise hypothesis leads to two predictions: (1) parallel word recognition, based on the ventral visual system, should be limited to words displayed in a familiar format (foveal horizontal words with normally spaced letters); (2) words displayed in formats outside this field of expertise should be read serially, under supervision of dorsal parietal attention systems. We presented adult readers with words that were progressively degraded in three different ways (word rotation, letter spacing, and displacement to the visual periphery). Behaviorally, we identified degradation thresholds above which reading difficulty increased non-linearly, with the concomitant emergence of a word length effect on reading latencies reflecting serial reading strategies. fMRI activations were correlated with reading difficulty in bilateral occipito-temporal and parietal regions, reflecting the strategies required to identify degraded words. A core region of the intraparietal cortex was engaged in all modes of degradation. Furthermore, in the ventral pathway, word degradation led to an amplification of activation in the posterior visual word form area, at a level thought to encode single letters. We also found an effect of word length restricted to highly degraded words in bilateral occipitoparietal regions. Those results clarify when and how the ventral parallel visual word form system needs to be supplemented by the deployment of dorsal serial reading strategies.
The coagulation activity level at which oral surgery procedures can be performed in anticoagulate... more The coagulation activity level at which oral surgery procedures can be performed in anticoagulated patients without triggering bleeding complications and without enhancing the risk of developing thrombo-embolic events remains controversial. The objective of the present study was to evaluate blood loss following dental extractions at different levels of anticoagulation and to determine its effect on wound closure rates. Blood loss was measured following the removal of four front teeth in warfarinized rabbits. Immediate blood loss was evaluated by determining the tooth socket bleeding times and by using a technique based on hemoglobin determinations. Long-term blood loss was assessed by comparison of labeled red-blood-cell disappearance curves. The results showed that blood loss following dental extractions was significantly greater in animals anticoagulated at a therapeutic level than in non-anticoagulated control animals. Determination of blood loss at different levels of anticoagulation clearly demonstrated that complete correction of the coagulation activity was unnecessary. Partial correction (INR values of 1.6-1.8) allowed extractions to be performed without extensive blood loss. With this technique of partial correction, the period of interruption of the anticoagulation could be kept very short, and the risk of postoperative bleeding complications was minimal. Wound closure rates were negatively influenced in anticoagulated animals.
Several publications have reported an increased susceptibility for root caries after periodontal ... more Several publications have reported an increased susceptibility for root caries after periodontal therapy. It has been suggested that newly exposed roots were less resistant to cariogenic species. This study examined the hypothesis that the increased susceptibility could also be related to an intra-oral microbial shift during the initial phase of the periodontal therapy from a perio-pathogenic to a more cariogenic flora. 10 patients with severe periodontitis were followed for 8 months after thorough scaling and root planing in combination with optimal plaque control. At baseline and after 4 and 8 months, samples were taken from the saliva, the tongue dorsum and the supragingival interdental spaces. These samples were cultured both aerobically and anaerobically in order to determine the total number of colony forming units (CFU) per sample as well as the number of CFU of Streptococcus mutans and Lactobacillus species. Oral hygiene parameters were recorded at the same visits. Finally, at baseline and at the 8 months follow-up, changes in caries activity and periodontal health were registered. Although the total number of aerobic and anaerobic CFU in samples from the tongue and the saliva remained nearly constant over the entire observation period (variations within 0.5 log), significant (p< or =0.05) increases in the number of S. mutans could be detected, especially at month 8. The significant decrease in the total number of anaerobic CFU in samples from the teeth was not associated with a reduction in the number of S. mutans, so that also for this niche the relative proportion of the latter increased. The number of lactobacilli species for the different niches showed only negligible changes (within 0.5 log values), except for samples from the teeth for which a small (1 log), but statistically significant (p<0.01), reduction could be detected. The periodontal conditions improved for all patients, but the caries activity could not be arrested. These findings seem to indicate that the increased caries susceptibility after periodontal therapy might partially be explained by a significant increase in the number of S. mutans due to ecological changes within the oral cavity. The clinical consequence of this observation would be to advocate a more strict caries preventive program during initial periodontal therapy.
International Journal of Oral and Maxillofacial Surgery, 2005
The aim of the present study was to perform a retrospective study of autogeneously transplanted t... more The aim of the present study was to perform a retrospective study of autogeneously transplanted teeth in order to examine the influence of clinical criteria such as the type of the donor tooth, the root length at the time of transplantation, donor eruption stage and others on the overall success rate of the transplantation. The material of this study consisted of 194 patients in whom 273 teeth were transplanted. The mean age at the time of autotransplantation was 18.1 years with a standard deviation of 7.5 years. Transplantations were performed in two hospitals. The follow-up period varied from 15 days to 11 years, and the mean follow-up time was 3.8 years. 58/273 teeth showed one or other form of resorption, 37/273 teeth showed ankylosis, 30/273 showed no important changes in pulp chamber size, 104/273 showed major discoloration after transplantation, 92/273 teeth showed positive results for cold test after transplantation and 26/273 teeth showed clinically unacceptable pocket depth. Clinical and radiological evaluations were performed. An association was found between successful transplantation and donor tooth type (P<0.01), root length at the time of transplantation (P<0.0001) and recipient tooth site (P=0.03). There was a borderline association between successful transplantation and donor eruption stage (P=0.05). In conclusion, autotransplantation of teeth performed with a careful surgical procedure at the stage of 1/2-3/4 of their intended or expected root length can render a very useful service to patients.
How is reading, a cultural invention, coded by neural populations in the human brain? The neural ... more How is reading, a cultural invention, coded by neural populations in the human brain? The neural code for written words must be abstract, because we can recognize words regardless of their location, font and size. Yet it must also be exquisitely sensitive to letter identity and letter order. Most existing coding schemes are insufficiently invariant or incompatible with the constraints of the visual system. We propose a tentative neuronal model according to which part of the occipito-temporal 'what' pathway is tuned to writing and forms a hierarchy of local combination detectors sensitive to increasingly larger fragments of words. Our proposal can explain why the detection of 'open bigrams' (ordered pairs of letters) constitutes an important stage in visual word recognition.
The aim of this study was to establish whether a patient-administered medical risk-related histor... more The aim of this study was to establish whether a patient-administered medical risk-related history (MRRH) for dental patients was valid. The MRRH, which was developed in the Netherlands, has now been tested in Belgium, where it was ...
Fast, parallel word recognition, in expert readers, relies on sectors of the left ventral occipit... more Fast, parallel word recognition, in expert readers, relies on sectors of the left ventral occipito-temporal pathway collectively known as the visual word form area. This expertise is thought to arise from perceptual learning mechanisms that extract informative features from the input strings. The perceptual expertise hypothesis leads to two predictions: (1) parallel word recognition, based on the ventral visual system, should be limited to words displayed in a familiar format (foveal horizontal words with normally spaced letters); (2) words displayed in formats outside this field of expertise should be read serially, under supervision of dorsal parietal attention systems. We presented adult readers with words that were progressively degraded in three different ways (word rotation, letter spacing, and displacement to the visual periphery). Behaviorally, we identified degradation thresholds above which reading difficulty increased non-linearly, with the concomitant emergence of a word length effect on reading latencies reflecting serial reading strategies. fMRI activations were correlated with reading difficulty in bilateral occipito-temporal and parietal regions, reflecting the strategies required to identify degraded words. A core region of the intraparietal cortex was engaged in all modes of degradation. Furthermore, in the ventral pathway, word degradation led to an amplification of activation in the posterior visual word form area, at a level thought to encode single letters. We also found an effect of word length restricted to highly degraded words in bilateral occipitoparietal regions. Those results clarify when and how the ventral parallel visual word form system needs to be supplemented by the deployment of dorsal serial reading strategies.
The coagulation activity level at which oral surgery procedures can be performed in anticoagulate... more The coagulation activity level at which oral surgery procedures can be performed in anticoagulated patients without triggering bleeding complications and without enhancing the risk of developing thrombo-embolic events remains controversial. The objective of the present study was to evaluate blood loss following dental extractions at different levels of anticoagulation and to determine its effect on wound closure rates. Blood loss was measured following the removal of four front teeth in warfarinized rabbits. Immediate blood loss was evaluated by determining the tooth socket bleeding times and by using a technique based on hemoglobin determinations. Long-term blood loss was assessed by comparison of labeled red-blood-cell disappearance curves. The results showed that blood loss following dental extractions was significantly greater in animals anticoagulated at a therapeutic level than in non-anticoagulated control animals. Determination of blood loss at different levels of anticoagulation clearly demonstrated that complete correction of the coagulation activity was unnecessary. Partial correction (INR values of 1.6-1.8) allowed extractions to be performed without extensive blood loss. With this technique of partial correction, the period of interruption of the anticoagulation could be kept very short, and the risk of postoperative bleeding complications was minimal. Wound closure rates were negatively influenced in anticoagulated animals.
Several publications have reported an increased susceptibility for root caries after periodontal ... more Several publications have reported an increased susceptibility for root caries after periodontal therapy. It has been suggested that newly exposed roots were less resistant to cariogenic species. This study examined the hypothesis that the increased susceptibility could also be related to an intra-oral microbial shift during the initial phase of the periodontal therapy from a perio-pathogenic to a more cariogenic flora. 10 patients with severe periodontitis were followed for 8 months after thorough scaling and root planing in combination with optimal plaque control. At baseline and after 4 and 8 months, samples were taken from the saliva, the tongue dorsum and the supragingival interdental spaces. These samples were cultured both aerobically and anaerobically in order to determine the total number of colony forming units (CFU) per sample as well as the number of CFU of Streptococcus mutans and Lactobacillus species. Oral hygiene parameters were recorded at the same visits. Finally, at baseline and at the 8 months follow-up, changes in caries activity and periodontal health were registered. Although the total number of aerobic and anaerobic CFU in samples from the tongue and the saliva remained nearly constant over the entire observation period (variations within 0.5 log), significant (p< or =0.05) increases in the number of S. mutans could be detected, especially at month 8. The significant decrease in the total number of anaerobic CFU in samples from the teeth was not associated with a reduction in the number of S. mutans, so that also for this niche the relative proportion of the latter increased. The number of lactobacilli species for the different niches showed only negligible changes (within 0.5 log values), except for samples from the teeth for which a small (1 log), but statistically significant (p<0.01), reduction could be detected. The periodontal conditions improved for all patients, but the caries activity could not be arrested. These findings seem to indicate that the increased caries susceptibility after periodontal therapy might partially be explained by a significant increase in the number of S. mutans due to ecological changes within the oral cavity. The clinical consequence of this observation would be to advocate a more strict caries preventive program during initial periodontal therapy.
International Journal of Oral and Maxillofacial Surgery, 2005
The aim of the present study was to perform a retrospective study of autogeneously transplanted t... more The aim of the present study was to perform a retrospective study of autogeneously transplanted teeth in order to examine the influence of clinical criteria such as the type of the donor tooth, the root length at the time of transplantation, donor eruption stage and others on the overall success rate of the transplantation. The material of this study consisted of 194 patients in whom 273 teeth were transplanted. The mean age at the time of autotransplantation was 18.1 years with a standard deviation of 7.5 years. Transplantations were performed in two hospitals. The follow-up period varied from 15 days to 11 years, and the mean follow-up time was 3.8 years. 58/273 teeth showed one or other form of resorption, 37/273 teeth showed ankylosis, 30/273 showed no important changes in pulp chamber size, 104/273 showed major discoloration after transplantation, 92/273 teeth showed positive results for cold test after transplantation and 26/273 teeth showed clinically unacceptable pocket depth. Clinical and radiological evaluations were performed. An association was found between successful transplantation and donor tooth type (P<0.01), root length at the time of transplantation (P<0.0001) and recipient tooth site (P=0.03). There was a borderline association between successful transplantation and donor eruption stage (P=0.05). In conclusion, autotransplantation of teeth performed with a careful surgical procedure at the stage of 1/2-3/4 of their intended or expected root length can render a very useful service to patients.
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Papers by F. Vinckier