Biomedical subjects

Michel Habib

Publications and source records attributed to Michel Habib.

8 recordsLinked to original sources

PubMed2006

Behavioural and event-related potentials evidence for pitch discrimination deficits in dyslexic children: improvement after intensive phonic intervention.

Although it is commonly accepted that dyslexic children have auditory phonological deficits, the precise nature of these deficits remains unclear. This study examines potential pitch processing deficit in dyslexic children, and recovery after specific training, by measuring event-related brain potentials (ERPs) and behavioural responses to pitch manipulations within natural speech. In two experimental sessions, separated by 6 weeks of training, 10 dyslexic children, aged 9-12, were compared to reading age-matched controls, using sentences from children's books. The pitch of the sentence's final words was parametrically manipulated (either congruous, weakly or strongly incongruous). While dyslexics followed a training focused on phonological awareness and grapheme-to-phoneme conversion, controls followed a non-auditory training. Before training, controls outperformed dyslexic children in the detection of the strong pitch incongruity. Moreover, while strong pitch incongruities were associated with increased late positivity (P300 component) in controls, no such pattern was found in dyslexics. Most importantly, pitch discrimination performance was significantly improved, and the amplitude of the late positivity to the strong pitch incongruity enhanced, for dyslexics after a relatively brief period of training, so that their pattern of response more closely resemble those of controls.

Auditory Perceptual Disorders↗

PubMed2004

Athymhormia and disorders of motivation in Basal Ganglia disease.

The author proposes a general model of human motivation as a separate function at the interface between emotion and action, which can be ascribed to subcortical circuits that are mainly centered on a subset of the basal ganglia and on their limbic connections. It is argued that the long-standing historical understatement of the notion of motivation in neurology is not only due to the complexity of the issue, which has proven hard to disentangle from other domains of dysfunction, but also to the persistence of some misleading conceptual orientations in the way neurologists have considered the brain mechanisms of goal-directed action, torn between a nonspecific "activation" view and an exclusively cognitive conception of motivation. How combining early clinical intuitions of some psychiatrists, careful clinical observations of neurological patients, and data derived from experimental studies in animals provide the basis for a coherent model of human motivation and its specific impairment in clinical neurology is explained. Clinical implications that can be drawn from such a model for some neuropsychiatric conditions are proposed.

Aged↗

PubMed2003

[Semiology of behavioral disorders caused by cerebral injury].

Behavioural and emotional changes, often referred to as pseudo-psychiatric symptoms, vary according to lesional sites. The study of different types of frontal syndromes provide the largest part of this chapter, including depression and pseudo-depression, mania, emotional indifference, anosognosia, desinhibition. Temporal lobe syndromes are less frequent, at the exception of various consequences of temporal lobe epilepsy. The Klüver and Bucy syndrome is classical but fortunately rare. The French literature as recently emphasised a special syndrome associating loss of motivation, lack of spontaneous mental activity and reduced emotionality (athymhormic syndrome) specifically associated to bilateral basal ganglia lesions. Finally, the syndrome of alexithymia, often considered but a personality trait may also appear as a consequence of callosal lesions.

Brain Diseases↗

PubMed2003

Rewiring the dyslexic brain.

Overcoming learning disorders is now becoming a realistic goal for neuroscientists and therapists. Seven years after their twin papers in Science suggesting the efficacy of intensive auditory training in children with language learning impairment, the Tallal-Merzenich team now report convincing evidence of just what such training programs can change in these children's brain. With the help of functional imaging, they demonstrate significant reorganization in both hemispheres after only eight weeks of daily training.

Journal Article↗

PubMed2002

Temporal processing and phonological impairment in dyslexia: effect of phoneme lengthening on order judgment of two consonants.

The evidence of supporting phonological deficit as a cause of developmental dyslexia has been accumulating rapidly over the past 2 decades, yet the exact mechanisms underlying this deficit remain controversial. Some authors assume that a temporal processing deficit is the source of the phonological disorder observed in dyslexic children. Others maintain that the phonological deficit in dyslexia is basically linguistic, not acoustic, in nature. Three experiments were conducted and tested the impact of the temporal alteration and the impact of complex syllabic structure on consonant order judgments. Thirteen phonological dyslexics (age 10-13) and 10 controls matched for chronologial age were compared on a Temporal Order Judgment (TOJ) task using the succession of two consonants (/p/ /s/) within a cluster. In order to test the possible relevance of the temporal deficit hypothesis, the task also included two additional conditions where either the two stimuli were artificially slowed or two phonological structures were opposed (CCV and CVCV). As expected, the TOJ performance was significantly poorer in dyslexics than in controls. Moreover, in the "slowed speech" condition dyslexics' performance improved to reach the normal controls' level, whereas manipulating the phonological structure complexity provided no significant improvement. Finally dyslexics' performances, especially on the slowed condition, were found correlated with several tests of phonological processing. These results lend support to the general temporal deficit theory of dyslexia.

Adolescent↗

PubMed2002

Interhemispheric sensorimotor integration in pointing movements: a study on dyslexic adults.

In addition to reading disorders, numerous deficits have been found to be associated with dyslexia, suggesting that various neurological factors might be involved in its etiology. In the present study, we focused on three of the deficits which have been thought to accompany and to a certain extent, to explain dyslexia: an abnormal pattern of hemispheric asymmetry, abnormal hemispheric communication, and abnormal motor control. The aim of the present study was to determine whether adults with reading difficulties perform differently from control subjects in a visuo-manual pointing task, in which the subject was required to point with the right or the left hand to targets appearing to the right or left of a central fixation point. A total of 14 dyslexic adults and 14 control adults participated in this experiment. Motor control was assessed based on the time taken to perform the pointing task, hemispheric asymmetry in terms of the inter-hand differences in the reaction and movement times, and hemispheric communication based on the interhemispheric transfer time under crossed conditions, where the hand and the target were not on the same side. The results showed that neither hemispheric asymmetry nor interhemispheric transfer differed between dyslexic and control adults. However, the dyslexics were significantly slower when performing the pointing task. These results are in agreement with the hypothesis that dyslexia may involve a mild motor deficit.

Adult↗

PubMed2002

An electrophysiological study of dyslexic and control adults in a sentence reading task.

Event-related potentials and cued-recall performance were used to compare dyslexic and control adult subjects. Sentences that ended either congruously or incongruously were presented visually, one word at a time, at fast (stimulus-onset-asynchrony (SOA)=100 ms) or slow (SOA=700 ms) rates of presentation. Results revealed (1) a large effect of presentation rate that started with the N1-P2 components and lasted for the entire recording period, (2) larger N400 components for dyslexic than control subjects, at slow presentation rates, to both congruous and incongruous endings and (3) a large ERPs difference related to memory (Dm effect) that did not differentiate controls from dyslexics but was larger at slow than at fast rates of presentation. These findings indicate that the reading impairment observed in the present group of adult dyslexics is more likely to result from difficulties integrating the meaning of words within a sentence context than from pure sensory processing deficits.

Adult↗

PubMedDate not supplied

Phonological training in children with dyslexia using temporally modified speech: a three-step pilot investigation.

Three separate studies were successively carried out to investigate the usefulness of intensively training children with dyslexia with daily exercizes based on the temporal processing theory of dyslexia, according to which these children would be specifically unable to process brief and rapidly changing auditory stimuli. The speech modification, similar for the three studies, was close to that proposed by Merzenich et al. (1996) and Tallal et al. (1996), including both artificial slowing of natural speech stimuli and amplification of brief, unstable portions of the speech signal. In the first study, 12 children, aged 10-12 years, received either such modified speech or normal speech for 1 h a day, 5 days a week, over 5 weeks, and they were assessed on phonological tasks before, during and after training. A significant advantage for the modified speech group was found both in pre-post-training improvement and in day-to-day progression on phonological performance. In a second study, 29 children with dyslexia, aged 5-12, received a similar training, but for only 15 min a day, 7 days a week, over 6 weeks, part at the speech therapist office, part in their own homes. The finding of comparable improvement in a more 'natural' environment and in children over a wider age range indicates both the efficacy and feasibility of the method in usual clinical practice. However, this study also showed that one of four children did not improve as expected, prompting a third study where 23 other children underwent specific tasks presumably exploring various aspects of temporal processing in order to find predictors of training efficacy. A 'temporal order judgement' (TOJ) task was found best correlated with post-training improvement, suggesting that one use this task for selecting the best candidates for temporo-phonological training. Moreover, such correlation provided further argument in favour of the temporal deficit theory of dyslexia, not only by showing a link between a purely temporal task and ultimate phonological performance, but also by demonstrating that TOJ performance itself improves after phonological training. Finally, and taken together, these studies provide further justification for a rational, indication-based temporo-phonological treatment of dyslexia. Possible neural substrates of the relevant mechanisms are discussed in the light of recent experimental and brain-imaging studies.

Child↗