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Biomedical subjects

M Steinschneider

Publications and source records attributed to M Steinschneider.

26 records · Page 2Linked to original sources
PubMed1992

Demonstration of mismatch negativity in the monkey.

In humans, deviant auditory stimuli elicit an event-related potential (ERP) component, termed "mismatch negativity" (MMN), that reflects the operation of a cortical detector of infrequent stimulus change. Epidural auditory ERPs were recorded from 3 cynomolgous monkeys in response to soft and loud clicks. "Oddball" loud or soft stimuli elicited a long-duration frontocentral negativity, peaking at approximately 85 msec, that was superimposed upon cortically generated obligatory ERP components. These data suggest that monkeys might serve as a heuristically valuable system in which to study the neurochemical and neuroanatomical substrates of early context-dependent ERP generation.

Acoustic Stimulation↗
PubMed1990

Tonotopic features of speech-evoked activity in primate auditory cortex.

To further clarify the neural mechanisms underlying the cortical encoding of speech sounds, we have recorded multiple unit activity (MUA) in the primary auditory cortex (A1) and thalamocortical (TC) radiations of an awake monkey to 3 consonant-vowel syllables, /da/, /ba/ and /ta/, that vary in their consonant place of articulation and voice onset time (VOT). In addition, we have examined the responses to the syllables' isolated formants and formant pairs. Response features are related to the cortical tonotopic organization, as determined by examining the responses to selected pure tones. MUA patterns that differentially reflect the spectral characteristics of the steady-state formant frequencies and formant transition onset frequencies underlying consonant place of articulation occur at sites with similarly differentiated tone responses. Whereas the detailed spectral characteristics of the speech sounds are reflected in low frequency cortical regions, both low and high frequency areas generate responses that reflect their temporal characteristics of fundamental frequency and VOT. Formant interactions modulate the responses to the whole syllables. These interactions may sharpen response differences that reflect consonant place of articulation. Response features noted in A1 also occur in TC fibers. Thus, differences in the encoding of speech sounds between the thalamic and cortical levels may include further opportunities for formant interactions within auditory cortex. One effect could be to heighten response contrast between complex stimuli with subtle acoustical differences.

Acoustic Stimulation↗
PubMed1982

Speech evoked activity in the auditory radiations and cortex of the awake monkey.

To determine whether phonetic features of human speech are reflected in activity patterns of the auditory cortex and its thalamic afferents, concurrent recordings of multiple unit activity (MUA) and averaged evoked potentials (AEP) to 3 synthetic syllables: /da/,/ba/ and /ta/, were performed in awake monkeys. Using clicks, responses from thalamocortical axons and cortical cells were differentiated on the basis of their response latency, spatial distribution, and relationships to AEP components. Voice onset time was reflected in MUA time-locked to consonant release and voicing onset, and phase-locked to the syllables' fundamental frequency. Place of articulation was reflected in discriminative 'on' and phase-locked responses occurring to the formant transitions of the syllables. Duration of the voiced formant transitions was represented by an accentuation of the phase-locked responses occurring to this period. Activity of thalamocortical fibers and cortical cells differed. Thalamocortical fibers were more responsive to speech sounds, as well as responding more frequently with a phase-locked response pattern. Cortical cells responded with sustained activity to a greater degree. Responses to identical portions of the vowels were biased by the preceding consonant. The spatial extent and timing of the responses demonstrate that speech sounds are processed along parallel, but not synchronous, channels. Relevance to human psychoacoustical phenomena is discussed.

Acoustic Stimulation↗
PubMed1980

Phase-locked cortical responses to a human speech sound and low-frequency tones in the monkey.

Concurrent recordings of average evoked potentials (AEP) and multiple unit activity (MUA) in monkey primary cortex to the syllable/da/, low-frequency tones, and clicks were performed. The AEP in response to the syllable consisted of a periodic alternation superimposed upon slower phasic deflections. All components inverted across the superior temporal plane, indicating their auditory cortical origin. The periodic activity was phase-locked to the syllable's fundamental frequency at a latency of approximately 11 msec. MUA displayed a similar pattern of periodic activity, but with a shorter interval between stimulus and response peaks. This phase-locked MUA occurred only at regions of AEP polarity inversion. Phase-locked activity was also observed in the cortical AEP to 100 and 250 Hz, but not to 500 Hz tonal stimulation. MUA phase-locked to the stimulus frequency only occurred at 100 Hz. Both the periodic and slow components of the AEP were volume-conducted to the dorsal cortical surface. This finding suggests the possibility that similar cortical responses to speech sounds can be recorded from the human scalp.

Animals↗
PubMedDate not supplied

Cellular generators of the cortical auditory evoked potential initial component.

Cellular generators of the initial cortical auditory evoked potential (AEP) component were determined by analyzing laminar profiles of click-evoked AEPs, current source density, and multiple unit activity (MUA) in primary auditory cortex of awake monkeys. The initial AEP component is a surface-negative wave, N8, that peaks at 8-9 msec and inverts in polarity below lamina 4. N8 is generated by a lamina 4 current sink and a deeper current source. Simultaneous MUA is present from lower lamina 3 to the subjacent white matter. Findings indicate that thalamocortical afferents are a generator of N8 and support a role for lamina 4 stellate cells. Relationships to the human AEP are discussed.

Acoustic Stimulation↗
PubMedDate not supplied

Classification of complex features of febrile seizures: interrater agreement.

As part of a prospective study of febrile seizures, three independent pediatric neurologists rated each of 100 febrile seizures for the presence of complex features: focality, long duration (greater than or equal to 10 min), and occurrence of multiple seizures. Seizure descriptions were assembled from all information available in the medical record and from a semistructured interview of a person who had witnessed the seizure. Interrater agreement assessed by kappa indicated excellent agreement with regard to whether the seizures were multiple or prolonged (kappa greater than or equal to 0.85) and fair to good agreement with regard to focality (kappa = 0.61-0.78). Disagreement occurred most often regarding assessment of focality. Reasons for disagreement included variation in interpretation of lateral eye deviation, staring episodes, and motor asymmetries in the context of a bilateral convulsion.

Child↗