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Biomedical subjects

Kathryn Martin

Publications and source records attributed to Kathryn Martin.

8 recordsLinked to original sources
PubMed2006

Abnormalities in central auditory maturation in children with language-based learning problems.

OBJECTIVE: To examine maturation of the central auditory pathways in children with language-based learning problems (LP). METHODS: Cortical auditory evoked potentials (CAEPs) recorded from 26 children with LP were compared to CAEPs recorded from 38 typical children. CAEP responses were recorded in response to a speech sound, /uh/, which was presented in a stimulus train with decreasing inter-stimulus intervals (ISIs) of 2000, 1000, 560, and 360 ms. RESULTS: We identified three atypical morphological categories of CAEP responses in the LP group. Category 1 responses revealed delayed P1 latencies and absent N1/P2 components. Category 2 responses revealed typical P1 responses, but delayed N1 and P2 responses. Category 3 responses revealed generally low-amplitude CAEP responses. A fourth sub-group of LP children had normal CAEP responses. CONCLUSIONS: Overall, the majority of children with LP had abnormal CAEP responses. These children fell into distinct categories based on the abnormalities in maturational patterns of their CAEP responses. SIGNIFICANCE: We describe a rate sensitive stimulation paradigm which may be used to identify and categorize LP children who exhibit abnormal patterns of central auditory maturation.

Acoustic Stimulation↗
PubMed2006

Minimization of cochlear implant stimulus artifact in cortical auditory evoked potentials.

OBJECTIVE: To compare two methods of minimizing cochlear implant artifact in cortical auditory evoked potential (CAEP) recordings. METHODS: Two experiments were conducted. In the first, we assessed the use of independent component analysis (ICA) as a pre-processing filter. In the second, we explored the use of an optimized differential reference (ODR) for minimizing artifacts. RESULTS: Both ICA and the ODR can minimize the artifact and allow measurement of CAEP responses. CONCLUSIONS: When using a large number of recording electrodes ICA can be used to minimize the implant artifact. When using a single electrode montage an optimized differential reference is adequate to minimize the artifact. SIGNIFICANCE: The use of an optimized differential reference could allow cortical evoked potentials to be used in routine clinical assessment of auditory pathway development in children and adults fit with cochlear implants.

Artifacts↗
PubMed2006

Central auditory development in children with bilateral cochlear implants.

OBJECTIVE: To examine the time course of maturation of P1 latencies in infant sequential and simultaneous bilateral cochlear implant recipients. DESIGN: Retrospective case series. SETTING: Pediatric collaborative cochlear implant program. PATIENTS: Four children who received bilateral cochlear implants prior to age 2 years. INTERVENTION: Cortical auditory evoked potential was completed to determine the latency of the P1 response in 4 children with bilateral cochlear implants. MAIN OUTCOME MEASURES: Longitudinal development of the latency of the P1 cortical auditory evoked potential in children who received bilateral cochlear implants prior to age 2 years. RESULTS: In 2 patients who received sequential bilateral implants, P1 latencies recorded from the first implanted ear were within normal limits after 3 to 6 months of implant use. By comparison, P1 latencies from the second implanted ear reached normal limits as early as 1 month after implant use. In 2 patients who received simultaneous bilateral implants, P1 latencies from both ears were also within normal limits in a very short time frame (ie, by 1 month poststimulation). CONCLUSIONS: Our data suggest a high degree of plasticity of the central auditory pathways after early bilateral implantation. We find that P1 latencies provide a clinically useful biomarker of central auditory system development in children after cochlear implantation.

Auditory Cortex↗
PubMed2005

Developmental changes in refractoriness of the cortical auditory evoked potential.

OBJECTIVE: This study examined morphological changes in the cortical auditory evoked potential (CAEP) waveform as a function of varying stimulation rate. Stimuli were presented in a paradigm which indirectly assesses the refractory properties of the underlying neuronal generators. METHODS: CAEPs were recorded in 50 normal-hearing children (3-12 years) and 10 young adults (24-26 years). A speech sound was presented in a stimulus train with sequentially decreasing inter-stimulus intervals (ISIs) of 2000, 1000, 560, and 360ms. Latencies and amplitudes of the P1, N1, and P2 components at the Cz electrode were examined as a function of stimulus rate and age. RESULTS: Results revealed significant changes in the CAEP as a function of age and stimulation rate. At younger ages the N1-P2 component was elicited only at the slowest stimulation rates, and was more clearly apparent at successively faster stimulation rates as age increased. CONCLUSIONS: We have described a stimulus paradigm that allows examination of the development of refractoriness by highlighting the interaction between age and rate on CAEP morphology. SIGNIFICANCE: Complex maturational patterns of CAEP components are best understood when the effects of both age and stimulus rate on the CAEP waveform are considered.

Acoustic Stimulation↗
PubMed2005

P1 latency as a biomarker for central auditory development in children with hearing impairment.

We used the latency of the P1 cortical auditory-evoked potential (CAEP) as a biomarker for the development of central auditory pathways in three children who received intervention through hearing aids and/or cochlear implants. Our goal was to examine the clinical feasibility of using the latency of the P1 CAEP as an objective tool to evaluate whether acoustic amplification for hearing-impaired children has provided sufficient stimulation for normal development of central auditory pathways. If clinicians have such a marker, then they can more confidently make a decision about whether to provide a child with a cochlear implant following an appropriate hearing-aid trial. Using the same marker, clinicians will also be able to monitor the maturation of central auditory pathways once electrical stimulation is initiated.

Auditory Pathways↗
PubMed2004

Central auditory maturation and babbling development in infants with cochlear implants.

OBJECTIVE: To examine the relationship between the maturation of central auditory pathways and the development of canonical (speechlike) babbling in infants with cochlear implants. DESIGN: Comparison of the latencies of the P1 cortical auditory evoked potential and vocalizations produced by subjects before they were fitted with a cochlear implant and at several time points within the first year after implantation. SUBJECTS: Two congenitally deaf children who were implanted with a multichannel cochlear implant at ages 13 and 14 months. INTERVENTIONS: P1 response latencies were recorded in response to a /ba/ stimulus before implantation and at several time points following implantation. Vocalizations produced by the subjects while interacting with their caregiver were audiorecorded twice before implantation and at monthly sessions following implantation. RESULTS: Subjects showed a rapid decrease in P1 latencies resulting in normal P1 latencies within about 3 months after implantation. Before implantation, the vocalizations were primarily of a precanonical nature. After 3 months' experience with the implants, the proportion of canonical vocalizations increased dramatically relative to the number of precanonical utterances. CONCLUSIONS: Results of this study suggest that the development of P1 response latencies and the development of early communicative behaviors may follow a similar developmental trajectory in children implanted early. Although preliminary, these findings indicate that the development of early communicative behaviors following implantation may be positively influenced by the rate of plastic changes in central auditory pathways.

Auditory Pathways↗
PubMedDate not supplied

Comparison of a fixed-dose combination of 40 mg telmisartan plus 12.5 mg hydrochlorothiazide with 40 mg telmisartan in the control of mild to moderate hypertension.

This study investigated whether a fixed-dose combination of 40 mg of the angiotensin II antagonist telmisartan plus 12.5 mg of the diuretic hydrochlorothiazide (HCTZ) was superior to 40 mg telmisartan in patients with mild to moderate hypertension who failed to respond adequately to 40 mg telmisartan monotherapy. One hundred forty-six patients were withdrawn before randomization. Nonresponders (n = 327) were double blind and randomized to 40 mg telmisartan + 12.5 mg HCTZ (n = 160) or 40 mg telmisartan (n = 167). After 8 weeks of treatment, 40 mg telmisartan + 12.5 mg HCTZ lowered diastolic blood pressure (DBP) by an additional 3.5 mm Hg (P <.01) and systolic blood pressure (SBP) by 7.4 mm Hg (P <.01) compared with 40 mg telmisartan. Most of the additional effect of the combination was seen after 4 weeks of treatment. At week 8, blood pressure was normalized (SBP <140 mm Hg and DBP <90 mm Hg) in 51.6% of patients on 40 mg telmisartan + 12.5 mg HCTZ compared with 23.5% on 40 mg telmisartan (P <.05). The combination of 40 mg telmisartan + 12.5 mg HCTZ normalized DBP in 64.8% of patients, whereas 40 mg telmisartan normalized DBP in 40.1% (P <.05). SBP decreased by > or =10 mm Hg from baseline in 63.5% of patients receiving the fixed-dose combination compared with 42.6% of those receiving 40 mg telmisartan (P <.05). Both treatments were well tolerated. Adverse events were predominantly mild, transient, and considered unrelated to therapy. These findings indicate that a fixed-dose combination of 40 mg telmisartan + 12.5 mg HCTZ is clinically and statistically superior to 40 mg telmisartan in patients with mild to moderate hypertension failing to respond to 40 mg telmisartan alone.

Adult↗