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Biomedical subjects

K Hecox

Publications and source records attributed to K Hecox.

17 recordsLinked to original sources
PubMed1999

Neuropsychological and behavioral status of children with complex partial seizures.

Neuropsychological and behavioral status were examined in 57 children aged 7 to 16 years with complex partial seizures (CPS) and compared with 27 sibling control children of the same age. Epilepsy had a significant effect on both cognitive and behavioral adjustment measures. Children with CPS had significant impairment across all seven cognitive domains assessed, reflective of a profile of relatively diffuse and generalized cognitive dysfunction. Age at onset of recurrent seizures was the strongest and most consistent predictor of adequacy of cognitive functioning; earlier age at onset was associated with poorer cognitive status. Children with CPS also had more problems compared with sibling control children on measures of social and school competence and internalizing behavior problems, but not externalizing behaviors. Further, frequency of seizure activity in the past year, rather than age at seizure onset, emerged as the strongest predictor of these behavioral difficulties. These findings are discussed in the context of understanding the impact of CPS on cognition and behavioral adjustment, and identifying the contribution of various aspects of the neurodevelopmental course of CPS to these issues.

Achievement↗
PubMed1996

Auditory evoked brain stem responses to trains of stimuli in human adults.

OBJECTIVE: This study describes the effect of train length, interstimulus interval, intertrain interval (ITI), and stimulus duration on the transition from the unadapted to the adapted wave V auditory evoked brain stem response (ABR). DESIGN: ABRs were recorded to stimuli presented at two different rates: a slow rate characterizing the unadapted response and a fast rate characterizing the adapted response. Trains of stimuli (a sequence of stimuli separated by intervals of silence) also were presented. Different stimulus parameters defining the trains were varied. RESULTS: Given a sufficiently long ITI, the latency prolongation to the first three or four stimuli in a train was rapid. It was similar for trains differing in number of stimuli. After the first three or four stimuli, there was a more gradual latency prolongation as a function of stimulus number. Shorter ITIs had the effect of prolonging the latencies to all the stimuli in the trains, reducing the rate of latency prolongation over the first few stimuli, and causing responses to trains of different length to differ (e.g., two click train responses were shorter latency than four click train responses). An unexpected result was the latency prolongation of wave Vs after the presentation of the stimulus trains. CONCLUSIONS: In response to a train of clicks, there seems to be a rapid increase in wave V latency to the first few clicks in the train followed by a more gradual latency prolongation to subsequent clicks in the train.

Adult↗
PubMed1995

A comparison of binaural interactions using traditional and maximum length sequence evoked response paradigms.

OBJECTIVE: Two paradigms, the traditional binaural interaction (BI) paradigm and a maximum length sequence (MLS) BI paradigm were evaluated to investigate BI effects. DESIGN: Evoked response BI effects were assessed at different levels of the auditory pathway in two experiments. Each experiment consisted of three conditions: a traditional BI paradigm using conventional stimuli, a traditional BI paradigm using MLS stimuli, and a MLS BI paradigm using MLS techniques to recover kernels reflecting BIs. Eleven normal-hearing young adults served as subjects. RESULTS: There was evidence for BI effects on the auditory evoked brain stem response (ABR) and the middle latency response (MLR) using the traditional BI paradigm and conventional stimuli. With the same paradigm and MLS stimuli there was evidence for BI effects on the MLR but not the ABR. The more robust conventional effects may be explained by the larger amplitude evoked responses recorded conventionally due to the slower stimulation rates and more efficient signal to noise enhancement. BI effects were observed for both the ABR and MLR by recording BI kernels in the MLS BI paradigm. CONCLUSIONS: MLS BI kernels can be recorded in normal hearing adults. The MLS BI paradigm offers three potential advantages in recording binaural effects; avoidance of some of the methodological problems associated with traditional BI paradigms, faster stimulus rates permitting a more complete characterization of binaural rate effects, and more rapid data collection.

Acoustic Stimulation↗
PubMed1994

Distortion-product otoacoustic emission input/output functions as a function of frequency in human adults.

Two issues concerning distortion-product otoacoustic emission (DPE) input/output functions were addressed in the present study. The first was to characterize those functions from threshold to 65 dB SPL. The second concerned the extent to which DPE input/output functions vary as a function of frequency. DPE input/output functions were generated at 20 frequencies from 537 to 10,009 Hz from eight normal-hearing subjects. Replicate functions were generated within an experimental session and with more than 4 months separating sessions. Given the impressive reproducibility of the DPE measurements, the input/output functions recorded can be interpreted as the consequences of stable physiologic processes and not unimportant variability (measurement noise). These input in dB/output in dB functions were generally linear functions with slopes less than unity indicating compression of the DPE output as a function intensity of the input. The slopes of the DPE input/output functions increased as a function of frequency to approaching one at the highest frequencies tested. DPE magnitudes tended to be more similar across frequencies at high intensities. At the lower intensities, DPE magnitudes varied as a function of input frequency, explaining the difference in slope of the input/output functions. There were a small number of markedly nonmonotonic, nonlinear functions. The functions presented included a greater number of intensities and frequencies and were less susceptible to explanations implicating the variability of the measurements than previous studies. The results, however, were quite consistent with those studies.

Acoustic Stimulation↗
PubMed1992

Distortion-product otoacoustic emissions in human newborns and adults.

Cubic distortion-product otoacoustic emissions (DPEs) may have clinical and research applications. We reliably recorded DPEs at some frequencies in all of the normal-hearing human adults and newborns tested. Adult and newborn DPEs were of comparable amplitude, with the exception that a prominent dip between 1 and 3 kHz in the adult data was less evident in the newborn data. DPE amplitude was a linear function of the intensity of the eliciting primary stimuli. The slopes of the linear input-output functions increased with increasing frequency. Except at the highest frequencies assessed, adult input-output functions were steeper than newborn input-output functions.

Acoustic Stimulation↗
PubMed1992

Maximum length sequence auditory evoked brainstem responses in human newborns and adults.

Experiment 1 investigated developmental differences at high stimulus rates by using maximum length sequences (MLSs) and cross-correlation techniques to recover auditory evoked brainstem responses (ABRs). Reliable MLS ABRs were recorded in all of the newborns tested at the highest rate presented (minimum interpulse interval = 1.1 msec). Interpreting developmental rate effects from latency and amplitude shifts is problematic. Identification of higher order kernals offers new information concerning developmental rate effects. Kernel slices were measured at lower rates in more adults than newborns, suggesting that the newborn auditory system is less sensitive to temporal nonlinearities than the mature auditory system. This runs counter to developmental rate studies using conventional stimuli. Experiment 2 investigated developmental differences at high rates due to varying stimulus intensities. MLS wave V intensity functions were less steep than conventional wave V intensity functions. MLS thresholds were also higher than conventional thresholds (primarily due to the newborn data). Without equating for signal-to-noise ratio, it is difficult to make unambiguous conclusions concerning the observed developmental differences.

Acoustic Stimulation↗
PubMed1985

An X-linked recessive basal ganglia disorder with mental retardation.

We report a previously apparently undescribed, X-linked recessive basal ganglia disorder segregating in three generations of one family. The affected patients were variably mentally retarded, although some showed strengths in oral reading and memory. Most affected males had frontal bossing and increased head circumference with large calvaria in relation to facial bones. Their height and weight did not differ from that of other relatives; testicular size was average, chromosomes were normal, and results of laboratory investigations for known metabolic disorders were normal. All patients examined had neurological impairment, including persistent frontal lobe reflexes, cogwheel rigidity, postural changes, and Parkinsonian-type tremors. Some had strabismus; several had seizures. Although carriers of the condition were not consistently abnormal, two had suggestive signs. No definitive indication of the disorder was documented in infancy in any affected male, and it is possible that this could be due to lack of careful prospective clinical evaluation rather than to the absence of symptoms in early life.

Basal Ganglia Diseases↗
PubMed1983

Rise-fall time effects on the brainstem auditory evoked response: mechanisms.

Experiments were conducted to assess the contribution of place mechanisms to the effect of rise--fall time on wave V of the human brainstem auditory evoked response (BAER). Noise bursts of 4- and 10-ms duration were presented at various rise-fall times (0, 1, 2, and 5 ms). Subtractive high-pass masking techniques were used to determine the effect of rise time as a function of derived-band frequency. In general, increasing rise time prolonged wave V latency but did not affect amplitude. Rise-time effects did not depend on derived-band frequency and similar effects were seen in the unmasked conditions. In addition, narrowing the derived band did not alter the observed effects on latency and amplitude. Signal envelope showed no effects on traveling wave velocity. These results suggest that place mechanisms contribute little to changes in the BAER associated with rise--fall time.

Acoustic Stimulation↗
PubMed1983

The effect of broadband noise on the human brainstem auditory evoked response. I. Rate and intensity effects.

A series of experiments investigated the effects of continuous broadband noise (ipsilateral) on wave V of the click-evoked brainstem auditory evoked response (BAER). In general, a broadband noise masker increases the latency and decreases the amplitude of wave V. Varying both click and noise intensity, it was found that noise levels above about 40 dB SPL increase the latency and decrease the amplitude of wave V, regardless of click intensity. The effects of noise on wave V amplitude appear constant across click intensity, whereas the effects of a constant noise level on wave V latency decrease at higher click intensities. Both masking and adaptation increase wave V latency, but their combined effects are occlusive: rate-induced wave V latency shift decreases in the presence of continuous broadband noise. The clinical and theoretical implications of these findings are discussed.

Adaptation, Physiological↗
PubMed1983

The effect of broadband noise on the human brainstem auditory evoked response. II. Frequency specificity.

A series of experiments evaluated the effects of broadband noise (ipsilateral) on wave V of the brainstem auditory evoked response (BAER) elicited by tone bursts or clicks in the presence of high-pass masking noise. Experiment 1 used 1000- and 4000-Hz, 60-dB nHL tone bursts in the presence of broadband noise. With increasing noise level, wave V latency shift was greater for the 1000-Hz tone bursts, while amplitude decrements were similar for both tone-burst frequencies. Experiment 2 varied high-pass masker cutoff frequency and the level of subtotal masking in the presence of 50-dB nHL clicks. The effects of subtotal masking on wave V (increase in latency and decrease in amplitude) increased with increasing derived-band frequency. Experiment 3 covaried high-pass masker cutoff frequency and subtotal masking level for 1000- and 4000-Hz tone-burst stimuli. The effect of subtotal masking on wave V latency was reduced for both tone-burst frequencies when the response-generating region of the cochlear partition was limited by high-pass maskers. The results of these three experiments suggest that most of the wave V latency shift associated with increasing levels of broadband noise is mediated by a place mechanism when the stimulus is a moderate intensity (60 dB nHL), low-frequency (1000 Hz) tone burst. However, the interpretation of the latency shifts produced by broadband noise for 4000-Hz tone-burst stimuli is made more complex by multiple technical factors discussed herein.

Acoustic Stimulation↗
PubMed1979

Brain stem auditory evoked potentials in patients with congenital atresia.

The purpose of this paper is to illustrate the value of the brain stem auditory evoked response in the definitive assessment of newborn and older infants with congenital malformations of the auditory system. Clinical cases selected illustrate the methodology required in the evaluation and demonstrate how the technique can facilitate immediate and appropriate medical and habilitative services.

Adult↗