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Biomedical subjects

D J Marcus

Publications and source records attributed to D J Marcus.

7 recordsLinked to original sources
PubMed2000

Diminished motor timing control in children referred for diagnosis of learning problems.

Disabled readers exhibit motor timing control (MTC) deficits in bimanual coordination relative to average readers. This article evaluates to what extent poor MTC is specific to reading or if it is related to learning problems in general. Children (7 to 11 years of age) referred for learning impairment (LI; n = 100) and same-age children nonlearning impaired (NLI; n = 243) performed a paced finger-tapping task. Greater variability of interresponse intervals was associated with poorer reading, spelling, and arithmetic achievement. The LI group performed more poorly than the NLI group, a difference that persisted even after adjusting for reading skill. Poor MTC is associated with poor reading but may also be a characteristic of children referred for learning problems, possibly signaling increased vulnerability of underlying neural integrative processes relevant to the child's adaptation to academic demands, including reading.

Attention↗
PubMed1996

Phonemic restoration and integration during dichotic listening.

In a series of experiments, evidence was obtained for phonemic restoration when a word with the segment /s/ excised and replaced by silence and a comparable noise segment were presented dichotically. What has been called phonemic integration was also demonstrated by presenting the excised /s/ and the word with the /s/ removed and replaced by silence dichotically. Phonemic restoration and integration effects tended to be enhanced when barely audible versions of the excised /s/ or noise segment replaced the silence. Finally, phonemic integration was obtained when words with an excised CV syllable or VC rime were present dichotically together with the remainder of the word.

Dichotic Listening Tests↗
PubMed1982

Pseudoseizures: diagnostic evaluation.

A prospective study of pseudoseizures using prolonged video-electroencephalographic (EEG) recording was carried out in 60 patients. Of 33 patients with episodes of uncertain mechanism, a diagnosis based on recorded episodes was made in 18 (55%). Twelve (36%) had pseudoseizures; 6 (18%) had epileptic seizures. Ten additional patients had epileptiform EEGs compatible with epilepsy. Of 27 patients with presumably uncontrolled epileptic seizures, 4 (15%) had recorded pseudoseizures. Prediction of the nature of the episode by the admitting neurologist was accurate in 67% of cases. Determination from observations of unit personnel and neurologists was correct in less than 80% of episodes. These data suggest that pseudoseizures occur frequently in patients being evaluated for epilepsy or suspected epilepsy. The clinical differentiation between epileptic seizures and pseudoseizures is often inaccurate. This differentiation is facilitated by prolonged video-EEG recording.

Adolescent↗
PubMedDate not supplied

Acute effects of phenytoin on peripheral nerve function in the rat.

The acute effect of intraperitoneal injection of phenytoin on rat peripheral nerve was studied. Conduction velocities in the ventral caudal nerve were measured hourly and phenytoin blood levels were obtained 4 to 5 hours after injection. Conduction velocity decreased by 23% in the 25 phenytoin-treated animals from a control value of 30.0 plus or minus 1.3m/sec (mean plus or minus SEM) to a 4-hour value of 23.0 plus or minus 1.3 m/sec (P less than 0.001). The phenytoin blood level 4 hours after injection was 45.0 plus or minus 1.3 micrograms/ml. Amplitudes of evoked muscle action potentials in the treated group decreased by 37% from control values. High levels of phenytoin induce prompt slowing of nerve conduction velocity within hours, which may be mediated by mechanisms similar to those responsible for toxic central effects.

Action Potentials↗
PubMedDate not supplied

Processing of rapid auditory stimuli in school-age children referred for evaluation of learning disorders.

Tallal hypothesized that reading disabled children have a domain-general deficit in processing rapidly occurring auditory stimuli that degrades speech perception, thereby limiting phonologic awareness and thus reading acquisition. She predicted they would be disproportionately affected by rapidly presented auditory stimuli. In this study, one hundred 7- to 11-year-old children with learning impairment (LI) and 243 non-learning impaired (NLI) children were evaluated on a two-tone auditory discrimination paradigm. LI committed more errors, but effects of timing were comparable. The same result was obtained for a subsample of good and poor readers. Task performance predicted reading, spelling, and calculation. Neural processes underlying perception of speech and other auditory stimuli may be less effective in poor readers; however, contrary to Tallal's hypothesis, rate may not be specifically affected.

Achievement↗