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Biomedical subjects

H Pratt

Publications and source records attributed to H Pratt.

186 records · Page 11Linked to original sources
PubMedDate not supplied

Contribution of click frequency bands to the human binaural interaction components.

The purpose of this study was to determine the contribution of click frequency bands (broad-band, >2000 Hz, <2000 Hz and <1000 Hz) to binaural interaction components (BICs) of the human auditory brainstem evoked potentials (ABEPs). The human BICs were studied by subtracting the potentials to binaural clicks from the algebraic sum of monaurally evoked potentials to either ear. Effective frequency bands were derived using clicks alone or clicks with ipsilateral or binaural masking noise, high- or low-pass filtered at different cut-off frequencies. Analysis included single-channel vertex-cervical spinous process VII derivation of BIC and ABEP, as well as estimating the single, centrally located dipole equivalent of the surface activity from three orthogonally positioned electrode pairs, using the three-channel Lissajous' trajectory (3-CLT) analysis. All BIC 3-CLTs included three major components (labeled BdII, BeI, and BeII) approximately corresponding in latency to IIIn, V and VI ABEP peaks. All apex latencies of BIC 3-CLT, except BeI, were longer in response to <2000 Hz and <1000 Hz (low-frequency) effective clicks. Apex amplitude of components BeI and BeII of BIC 3-CLT were smaller with low-frequency effective clicks than with broad-band or high-frequency (>2000 Hz) clicks. We suggest that binaural interaction component BeI is mainly tuned to high frequencies, showing no frequency effect on latency, and decreasing in amplitude with decreasing click high frequency content. In contrast, BdII and BeII of the human BICs are evoked more synchronously by high-frequency binaural inputs, but are also sensitive to low frequencies, increasing in latency according to the cochleotopic activation pattern. These differences between BIC components may reflect their roles in sound localization.

Acoustic Stimulation↗
PubMedDate not supplied

Brain potentials from dyslexic children recorded during short-term memory tasks.

Event Related Potentials (ERPs) from thirty children (9-13 years old); fourteen of whom were dyslexic and sixteen normal-reading controls, were recorded during the performance of a memory scanning task. Visually presented stimuli consisted of either digits (lexical) or unfamiliar (non-lexical) characters. The subjects had to indicate whether a probe stimulus was a member of a preceding memorized set, or not. The memorized sets included 1, 2 or 3 items. Performance accuracies were significantly lower and reaction times longer in the dyslexic group. The significant Group x Lexicality interaction demonstrated P3 amplitudes which were smaller to lexical compared to non-lexical stimuli in dyslexics compared to skilled readers. Brain activity in response to the probes was more prominent over the right scalp in dyslexics, in contrast to controls that had left side prominence. The results suggest that dyslexic children relate to the physical features of stimuli as opposed to skilled readers, who rely more on the linguistic features of the stimuli. We suggest that remembering visually presented items in dyslexics involves different cognitive strategies and brain structures compared to skilled readers.

Adolescent↗
PubMedDate not supplied

Integrative review of effects on children of witnessing domestic violence.

The purpose of this study was to conduct an integrative review of research studies concerning the effects on children of witnessing domestic violence. Databases were selected from MEDLINE, CINAHL, Health, and PsychInfo. Inclusion criteria required primary research in refereed journals during the last two decades that focused on children who had witnessed domestic violence (n = 14 studies). A total of 912 children and their parents comprised the subjects of this review. General agreement existed in this literature that children from families with domestic violence tended to have more difficulties than children from nonviolent families. Multidisciplinary findings revealed that the effects of witnessing violence were serious, varied, and generally framed in emotional and behavioral manifestations. Implications of these effects for clinical nursing research are considerable and merit further study.

Adolescent↗
PubMedDate not supplied

Density spectral array, evoked potentials, and temperature rhythms in the evaluation and prognosis of the comatose patient.

Glasgow Coma Scale (GCS), density spectral array (DSA), EEG, BAEP and circadian temperature rhythm were studied in comatose patients in order to determine level of arousal and appraise the prognostic capability of these combined measures. Subjects were 29 comatose patients in the neurosurgical ICU at the Rambam Medical Center suffering from head trauma, vascular disorders or metastatic growth. Results show that best prognostic capabilities were for DSA, GCS and BAEP, in that order. As a single parameter physiological response to a sound stimulus (increase in EMG, change in EEG frequency and appearance of sharp waves or k-complex) was the single best predictor for outcome, with significant response rates for the good, deficit, vegetative and death outcomes at 83%, 57%, 37% and 18%, respectively. Rectal temperature was analysed for 24 h circadian periodicity. Daily acrophases were found to shift forward or backward on the level of about 2-7 h a day with fluctuations about a stable or unstable mean. The absence of 'free-running rhythms' associated with environmental isolation studies might reflect an ability to respond to environmental Zeitgerbers while unconscious. Temperature oscillations as well as 24 h rhythms were found even in the most severely brain-damaged patients, reflecting the resilience of the circadian oscillators in the brain to trauma.

Adolescent↗