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Results for “Pitch Perception”

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At least 1,621 records · Page 90Linked to original sources

PubMed1992

Mismatch negativity in event-related potentials to auditory stimuli as a function of varying interstimulus interval.

The mismatch negativity, isolated as a component of the event-related brain potential elicited by deviant auditory stimuli, was suggested by Näätänen (1984) as an indirect measure of the inferred neuronal representation of standard stimuli. The purpose of the present study was to determine the duration of the neuronal representation by varying the interstimulus intervals of 1, 6, and 10 seconds within experimental blocks. Mismatch negativities were found to be elicited by deviant stimuli (1500-Hz tones, sequential probability 10%) following standard stimuli (1000-Hz tones) with interstimulus intervals of 1, 6, and 10 s as well. The results suggest a duration of neuronal representation of at least 10 s. The within-block variation of interstimulus interval, the rather low temporal probability of deviants, and their large frequency deviance might explain the present results contradicting earlier findings that suggested a shorter duration of that neuronal representation.

Adult↗

PubMed1993

The effects of between-source discriminability on attended and unattended auditory ERPs.

Event-related potentials (ERPs) for tone pips from attended and unattended sources, which varied on discriminability, were compared with ERPs for the same stimuli recorded during performance of a visual task. This comparison revealed that Nd, the negative shift of attended relative to unattended ERPs, consisted of three components: a negativity in the attended ERP from 100 to 270 ms, a positivity in the unattended ERP from 170 ms to the end of the epoch, and a second negativity in the attended ERP from 270 to 700 ms. In general, the later onset of early Nd with more difficult between-source discriminations could be attributed to the later onset of the positivity in unattended ERPs. A number of hypotheses were advanced for the origin of the unattended positivity: the suppression of the later of two negative components in the 100-220-ms range, an enhanced P2 component, an endogenous positivity, or the resolution of a protracted negativity elicited by preceding attended stimuli.

Adolescent↗

PubMed1994

Effects of stimulus preexposure and intermodality change on electrodermal orienting.

Previous research has indicated that an intermodality change trial presented after a habituation series elicits larger orienting responses than does the first stimulus of that series. Experiment 1 (N = 48) investigated whether this effect was still present if the change stimulus was not novel but was presented once prior to the habituation series. Two groups of subjects were presented with a series of 24 tones or vibrotactile stimuli. Trial 25 was an intermodality change test trial for half of the subjects in each group (change), whereas the remaining subjects received an additional habituation stimulus (no change). Prior to the habituation trials, each subject was exposed once to the test stimulus used in the change condition. Although response magnitude on the test trial was larger in the change condition than in the no-change condition, test trial response magnitude did not exceed that on the first trial of the habituation series. In Experiment 2 (N = 84), one group was preexposed to the test stimulus, another was preexposed to an experimentally irrelevant stimulus, and a third received no stimulus prior to habituation training. Test trial response magnitude was larger than responses to the first stimulus of habituation in the change group that was not exposed to a stimulus prior to habituation but not in the preexposed groups. Preexposure to a stimulus prior to habituation training abolished the intermodality change effect even when the test stimulus was novel. The present results pose problems for noncomparator theories of habituation and support the notion that anticipatory processes are important in orienting and habituation.

Adolescent↗

PubMed1994

Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials.

Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process.

Adult↗

PubMed1997

Magnetic fields elicited by tones and vowel formants reveal tonotopy and nonlinear summation of cortical activation.

A long-latency response component (N1m) and the sustained field (SF) of the auditory evoked magnetic field elicited by two composite stimuli (a two-tone combination and a two-formant vowel) and their individually presented components (a 600-Hz and a 2100-Hz pure tone and two single-vowel formants with formant frequencies matched to the tone frequencies) were recorded using a 37-channel magnetometer. The response to the composite stimuli differed from the linear sum of the responses to the respective components in latency, equivalent dipole moment, and equivalent dipole location, suggesting an interaction among the processes elicited by the constituents of composite stimuli. N1m and SF source locations were more medial for the response to the high tone than to the low tone and more medial for the response to the high vowel formant than to the low vowel formant. The N1m formant sources were more lateral than the N1m tone sources. These findings suggest that, at the level of the auditory cortex, vowels are represented in terms of both the spectral pitches determined by their most prominent harmonics and, within the latency range of the N1m, the virtual pitch determined by the spacing of the harmonics.

Acoustic Stimulation↗

PubMed1992

Audiogenic seizure susceptibility and auditory brainstem responses in rats prenatally exposed to alcohol.

Rats prenatally exposed to alcohol (0%, 17.5%, or 35% ethanol-derived calories) were tested for audiogenic seizure susceptibility on one of postnatal days 18 to 23, then retested 5 days later. Prenatal alcohol exposure did not influence audiogenic seizure susceptibility or severity. There was, however, a significant increase in seizure incidence on the retest day for all groups, suggesting a priming effect. Auditory brainstem response (ABR) data suggested that prenatal alcohol exposure and acoustic trauma (i.e., exposure to an alarm bell used for eliciting audiogenic seizures) induced measurable sensorineural hearing loss, and that the combined exposure to alcohol and acoustic trauma interacted additively to produce greater hearing loss than either alone.

Animals↗

PubMed1998

Implicit and explicit learning in an auditory serial reaction time task.

OBJECTIVE: To explore the role of the motor cortex during implicit and explicit learning. MATERIALS AND METHODS: EEG signals were recorded from 30 channels by measuring task-related desynchronization (TRD) when 10 right-handed naive volunteers performed a variation of the serial reaction task. Stimuli, consisting of 4 pure tones of 500, 1000, 1500, and 2000 HZ, lasting 200 ms, were presented binaurally through a pair of tubephones at 60 dB with a 2-s constant interstimulus interval. A series of 10 repetitive tones represented the test sequence; the random sequence was the control. RESULTS: All subjects developed implicit and explicit knowledge reflected by decreased response time, increased accuracy, and the ability to generate the sequence. Six of 10 subjects demonstrated implicit learning without explicit learning during the first 3 blocks. When subjects acquired full explicit learning, 10 Hz TRD at C3 reached a peak amplitude, declining thereafter. CONCLUSIONS: Properties of the sensorimotor cortex change during learning and these changes are independent of stimulus modality.

Adult↗

PubMed1982