Biomedical subjects

Terence W Picton

Publications and source records attributed to Terence W Picton.

At least 19 recordsLinked to original sources

PubMed2006

Enhanced anterior-temporal processing for complex tones in musicians.

OBJECTIVE: To examine how auditory brain responses change with increased spectral complexity of sounds in musicians and non-musicians. METHODS: Event-related potentials (ERPs) and fields (ERFs) to binaural piano tones were measured in musicians and non-musicians. The stimuli were C4 piano tones and a pure sine tone of the C4 fundamental frequency (f0). The first piano tone contained f0 and the first eight harmonics, the second piano tone consisted of f0 and the first two harmonics and the third piano tone consisted of f0. RESULTS: Subtraction of ERPs of the piano tone with only the fundamental from ERPs of the harmonically rich piano tones yielded positive difference waves peaking at 130 ms (DP130) and 300 ms (DP300). The DP130 was larger in musicians than non-musicians and both waves were maximally recorded over the right anterior scalp. ERP source analysis indicated anterior temporal sources with greater strength in the right hemisphere for both waves. Arbitrarily using these anterior sources to analyze the MEG signals showed a DP130m in musicians but not in non-musicians. CONCLUSIONS: Auditory responses in the anterior temporal cortex to complex musical tones are larger in musicians than non-musicians. SIGNIFICANCE: Neural networks in the anterior temporal cortex are activated during the processing of complex sounds. Their greater activation in musicians may index either underlying cortical differences related to musical aptitude or cortical modification by acoustical training.

Acoustic Stimulation↗

PubMed2006

Age-related changes in transient and oscillatory brain responses to auditory stimulation in healthy adults 19-45 years old.

The capacity of the human cerebral cortex to track fast temporal changes in auditory stimuli is related to the development of language in children and to deficits in speech perception in the elderly. Although maturation of temporal processing in children and its deterioration in the elderly has been investigated previously, little is known about naturally occurring changes in auditory temporal processing between these limits. The present study examined age-related (19-45 years) changes in 3 electrophysiological measures of auditory processing: 1) the late transient auditory evoked potentials to tone onset, 2) the auditory steady-state response (ASSR) to a 40-Hz frequency-modulated tone, and 3) the envelope following response (EFR) to sweeps of amplitude-modulated white noise from 10 to 100 Hz. With increasing age, the latency of the auditory P1-N1 complex decreased, the oscillatory (ASSR) response became larger and more stable, and the resonant peak of the EFR increased from 38 Hz at 19 years to 46 Hz at 45 years. Source analysis localized these changes to the auditory regions of the temporal lobe. These results indicate persistent adaptation of cortical auditory processes into middle adulthood. We speculate that experience-driven myelination and/or refinement of inhibitory circuits may underlie these changes.

Adult↗

PubMed2006

Human auditory steady-state responses to changes in interaural correlation.

Steady-state responses were evoked by noise stimuli that alternated between two levels of interaural correlation rho at a frequency fm. With rho alternating between +1 and 0, responses at fm dropped steeply above 4 Hz, but persisted up to 64 Hz. Two time constants of 47 and 4.4 ms with delays of 198 and 36 ms, respectively, were obtained by fitting responses to a transfer function based on symmetric exponential windows. The longer time constant, possibly reflecting cortical integration, is consistent with perceptual binaural "sluggishness". The shorter time constant may reflect running cross-correlation in the high brainstem or primary auditory cortex. Responses at 2fm peaked with an amplitude of 848+/-479 nV (fm=4 Hz). Investigation of this robust response revealed that: (1) changes in rho and lateralization evoked similar responses, suggesting a common neural origin, (2) response was most dependent on stimulus frequencies below 1000 Hz, but frequencies up to 4000 Hz also contributed, and (3) when rho alternated between [0.2-1] and 0, response amplitude varied linearly with rho, and the physiological response threshold was close to the average behavioral threshold (rho=0.31). This steady-state response may prove useful in the objective investigation of binaural hearing.

Acoustic Stimulation↗

PubMed2006

Effects of focal frontal lesions on response inhibition.

This study examined the performance of 38 normal subjects and 43 patients with focal lesions of the frontal lobes on a simple go-nogo task where the probability of the nogo stimulus was either 75% or 25%. Patients with lesions to the superior medial parts of the frontal lobes, in particular to the left superior portion of Brodmann area 6 (which includes the supplementary motor areas and the premotor areas for the right hand) had an increased number of false alarms (incorrect responses to the nogo stimulus). These results indicate that area 6 is specifically involved in the inhibition of response. Patients with lesions to the right anterior cingulate (areas 24 and 32) were slower and more variable in their reaction time. These findings could be explained by an inability to sustain stimulus-response contingencies. Lesions to the right ventrolateral prefrontal cortex (Brodmann areas 44, 45, 47) also increased the variability of response, perhaps by disrupting monitoring performance.

Brain Damage, Chronic↗

PubMed2006

Envelope following responses to natural vowels.

Envelope following responses to natural vowels were recorded in 10 normal hearing people. Responses were recorded to individual vowels (/a/, /i/, /u/) with a relatively steady pitch, to /[symbol: see text]/ with a variable and steady pitch, and to a multivowel stimulus (/[symbol: see text]ui/) with a steady pitch. Responses were analyzed using a Fourier analyzer, so that recorded responses could follow the changes in the pitch. Significant responses were detected for all subjects to /a/, /i/ and /u/ with the time required to detect a significant response ranging from 6 to 66 s (average time: 19 s). Responses to /[symbol: see text]/ and /[symbol: see text]ui/ were detected in all subjects, but took longer to demonstrate (average time: 73 s). These results support the use of a Fourier analyzer to measure envelope following responses to natural speech.

Acoustic Stimulation↗

PubMed2006

Cortical oscillations related to processing congruent and incongruent grapheme-phoneme pairs.

In this study, we investigated changes in cortical oscillations following congruent and incongruent grapheme-phoneme stimuli. Hiragana graphemes and phonemes were simultaneously presented as congruent or incongruent audiovisual stimuli to native Japanese-speaking participants. The discriminative reaction time was 57 ms shorter for congruent than incongruent stimuli. Analysis of MEG responses using synthetic aperture magnetometry (SAM) revealed that congruent stimuli evoked larger 2-10 Hz activity in the left auditory cortex within the first 250 ms after stimulus onset, and smaller 2-16 Hz activity in bilateral visual cortices between 250 and 500 ms. These results indicate that congruent visual input can modify cortical activity in the left auditory cortex.

Acoustic Stimulation↗

PubMed2006

Scalp topography and intracerebral sources for ERPs recorded during auditory target detection.

The goal of this study was to measure the scalp topography of the event-related potentials (ERPs) during the detection of improbable auditory targets and to determine the intracerebral sources of these potentials. ERPs were recorded when subjects listened to a sequence of spoken words and detected occasional (p = 0.2) targets defined either by the gender of the speaker (male/female) or the meaning of the word (animate/inanimate). Waveforms were evaluated in relation to category (target versus standard) and task (voice versus semantic). Dipole source analysis was performed using locations obtained from fMRI. Fronto-central negative waves (N450 and N600 ms) generated by sources in both the auditory cortex and frontal regions were larger for semantic tasks and larger over the left hemisphere. A large parieto-occipital positive wave (P700) occurring with a peak latency about 150 ms before the reaction time was mainly generated in the left temporo-parietal regions for the semantic task and bilaterally for the voice task. About 300 ms after the P700, a highly lateralized right temporo-parietal positive wave P1000r occurred with a source in the right temporo-parietal area. These results indicate three distinct physiological processes underlie the detection of auditory targets. Perceptual discrimination is related to interactions between the frontal and temporal regions, stimulus-response association occurs in the temporo-parietal regions and post-perceptual processing in the right temporo-parietal region.

Acoustic Stimulation↗

PubMed2006

Simultaneous latency estimations for distortion product otoacoustic emissions and envelope following responses.

The purpose of this research was to simultaneously estimate processing delays in the cochlea and brainstem using the same acoustic stimuli. Apparent latencies were estimated from ear canal measurements of 2f1-f2 distortion product otoacoustic emissions (DPOAEs), and scalp recordings of the f2-f1 envelope following response (EFR). The stimuli were equal level tone pairs (65 dB SPL) with the upper tone f2 set at either 900 or 1800 Hz to fix the initiation site of the DPOAE and EFR. The frequency of f1 was swept continuously between frequency limits chosen to keep the EFR response between 150 and 170 Hz. The average DPOAE latencies were 9.6 and 6.2 ms for f2 =900 and 1800 Hz, and the corresponding EFR latencies were 12.4 and 8.8 ms. In a control condition, a third (suppressor) tone was added near the DPOAE response frequency to evaluate whether the potential source at fdp was contributing significantly to the measured emission. DPOAE latency is the sum of both inward and outward cochlear delays. The EFR apparent latency is the sum of inward cochlear delay and neural processing delay. Neural delay was estimated as approximately 5.3 ms for both frequencies of stimulation.

Acoustic Stimulation↗

PubMed2006

Effects of attention on neuroelectric correlates of auditory stream segregation.

A general assumption underlying auditory scene analysis is that the initial grouping of acoustic elements is independent of attention. The effects of attention on auditory stream segregation were investigated by recording event-related potentials (ERPs) while participants either attended to sound stimuli and indicated whether they heard one or two streams or watched a muted movie. The stimuli were pure-tone ABA--patterns that repeated for 10.8 sec with a stimulus onset asynchrony between A and B tones of 100 msec in which the A tone was fixed at 500 Hz, the B tone could be 500, 625, 750, or 1000 Hz, and--was a silence. In both listening conditions, an enhancement of the auditory-evoked response (P1-N1-P2 and N1c) to the B tone varied with Deltaf and correlated with perception of streaming. The ERP from 150 to 250 msec after the beginning of the repeating ABA- patterns became more positive during the course of the trial and was diminished when participants ignored the tones, consistent with behavioral studies indicating that streaming takes several seconds to build up. The N1c enhancement and the buildup over time were larger at right than left temporal electrodes, suggesting a right-hemisphere dominance for stream segregation. Sources in Heschl's gyrus accounted for the ERP modulations related to Deltaf-based segregation and buildup. These findings provide evidence for two cortical mechanisms of streaming: automatic segregation of sounds and attention-dependent buildup process that integrates successive tones within streams over several seconds.

Adult↗

PubMed2005

Keeping time: effects of focal frontal lesions.

This study examined the performance of 32 normal subjects and 39 patients with focal lesions of the frontal lobes on two simple timing tasks-responding in time with a tone that regularly repeated at a rate of once every 1.5s, and then maintaining the same regular response rhythm without any external stimulus. The hypothesis was that lesions to the right prefrontal cortex would disrupt timing performance. The two main findings were (1) an abnormally high variability in the timing performance (both self-timed and tone-timed) of patients with lesions to the right lateral frontal lobe, particularly involving Brodmann area 45 and subjacent regions of the basal ganglia; (2) an increase in the variability of timing performance as the task continued in patients with lesions to the superior medial regions of the frontal lobe. These findings indicate that the right lateral frontal lobe is crucially involved in the ongoing control of timed behavior, either because of its role in generating time intervals or in monitoring the passage of these intervals. In contrast, the superior medial regions of the frontal lobe are necessary to maintain consistent timing performance over prolonged periods of time.

Acoustic Stimulation↗

PubMed2005

EEG spectral dynamics during discrimination of auditory and visual targets.

This study measured the changes in the spectrum of the EEG (electroencephalogram) and in the event-related potentials (ERPs) as subjects detected an improbable target in a train of standard stimuli. The intent was to determine how these measurements are related, and to what extent the ERPs might represent phase-locked changes in EEG rhythms. The experimental manipulations were the stimulus modality (auditory or visual), the discriminability of the target, and the presence or absence of distraction. The ERPs showed sensory-evoked potentials that were specific to the modality and a target-evoked P300 wave that was later in the visual modality than in the auditory, and later and smaller when the discrimination was more difficult. The averaged EEG spectrograms showed that targets increased the frontal theta activity, decreased posterior and central alpha and beta activity, and decreased the central gamma activity. The scalp topography of the changes in the alpha and beta activity indicated a posterior desynchronization specific for the visual task and occurring with both targets and standards and a more widespread desynchronization for targets in either modality. Increased phase synchronization occurred during the event-related potentials, but modeling demonstrated that this can be seen when an evoked potential waveform is simply added to the background EEG. However, subtracting the spectrogram of the average ERP from the average spectrogram of the single trials indicated that phase-resetting of the background EEG rhythms can occur during the ERP. The idea that the ERPs and the EEG rhythms "share generators" can explain these findings.

Acoustic Stimulation↗

PubMed2005

Multiple frontal systems controlling response speed.

This study evaluated a model of attention that postulates several distinct component processes, each mediated by specific neural systems in the human frontal lobes. A series of reaction time (RT) tests (simple, choice, and prepare) examined the hypothesis that different attentional processes are related to distinct regions within the frontal lobes. These tests were given to 38 patients with frontal lesions and 38 age-matched control subjects. Lesions were localized both by general regions (superior medial, inferior medial, left and right lateral) and by individual architectonic areas. Lesions in the superior medial (SM) frontal lobes, particularly involving areas 24 and 32 on the right, were associated with slow RT in all tests and with failure to decrease RT after a warning signal. Lesions in the right lateral (RL) frontal lobe, centred in area 9/46v, prevented the decrease in RT with increasing foreperiod that was seen in normal subjects and in patients with lesions elsewhere in the frontal lobes. The ability to energize a response for rapid RT, either generally or specifically following a warning stimulus, is sensitive to lesions of the right SM. Monitoring of stimulus occurrence and response behaviour in order to enhance the speed of response to upcoming stimuli is sensitive to RL lesions.

Adult↗

PubMed2005

Recording human evoked potentials that follow the pitch contour of a natural vowel.

We investigated whether pitch-synchronous neural activity could be recorded in humans, with a natural vowel and a vowel in which the fundamental frequency was suppressed. Small variations of speech periodicity were detected in the evoked responses using a fine structure spectrograph (FSS). A significant response (P < 0.001) was measured in all seven normal subjects even when the fundamental frequency was suppressed, and it very accurately tracked the acoustic pitch contour (normalized mean absolute error < 0.57%). Small variations in speech periodicity, which humans can detect, are therefore available to the perceptual system as pitch-synchronous neural firing. These findings suggest that the measurement of pitch-evoked responses may be a viable tool for objective speech audiometry.

Adult↗

PubMed2005

Estimating audiometric thresholds using auditory steady-state responses.

Human auditory steady-state responses (ASSRs) were recorded using stimulus rates of 78-95 Hz in normal young subjects, in elderly subjects with relatively normal hearing, and in elderly subjects with sensorineural hearing impairment. Amplitude-intensity functions calculated relative to actual sensory thresholds (sensation level or SL) showed that amplitudes increased as stimulus intensity increased. In the hearing-impaired subjects this increase was more rapid at intensities just above threshold ("electrophysiological recruitment") than at higher intensities where the increase was similar to that seen in normal subjects. The thresholds in dB SL for recognizing an ASSR and the intersubject variability of these thresholds decreased with increasing recording time and were lower in the hearing impaired compared to the normal subjects. After 9.8 minutes of recording, the average ASSR thresholds (and standard deviations) were 12.6 +/- 8.7 in the normal subjects, 12.4 +/- 11.9 dB in the normal elderly, and 3.6 +/- 13.5 dB SL in the hearing-impaired subjects.

Adult↗

PubMed2004

Auditory steady-state responses and word recognition scores in normal-hearing and hearing-impaired adults.

OBJECTIVE: The number of steady-state responses evoked by the independent amplitude and frequency modulation (IAFM) of tones has been related to the ability to discriminate speech sounds as measured by word recognition scores (WRS). In the present study IAFM stimulus parameters were adjusted to resemble the acoustic properties of everyday speech to see how well responses to these speech-modeled stimuli were related to WRS. DESIGN: We separately measured WRS and IAFM responses at a stimulus intensity of 70 dB SPL in three groups of subjects: young normal-hearing, elderly normal-hearing, and elderly hearing-impaired. We used two series of IAFM stimuli, one with modulation frequencies near 40 Hz and the other with modulation frequencies near 80 Hz. The IAFM stimuli, consisting of four carrier frequencies each independently modulated in frequency and amplitude, could evoke up to eight separate responses in one ear. We recorded IAFM responses and WRS measurements in quiet and in the presence of speech-masking noise at 67 dB SPL or 70 dB SPL. We then evaluated the hearing-impaired subjects with and without their hearing aids to see whether an improvement in WRS would be reflected in an increased number of responses to the IAFM stimulus. RESULTS: The correlations between WRS and the number of IAFM responses recognized as significantly different from the background were between 0.70 and 0.81 for the 40 Hz stimuli, between 0.73 and 0.82 for the 80 Hz stimuli, and between 0.76 and 0.85 for the combined assessment of 40 and 80 Hz responses. Response amplitudes at 80 Hz were smaller in the hearing-impaired than in the normal-hearing subjects. Response amplitudes for the 40 Hz stimuli varied with the state of arousal and this effect made it impossible to compare amplitudes across the different groups. Hearing aids increased both the WRS and the number of significant IAFM responses at 40 Hz and 80 Hz. Masking decreased the WRS and the number of significant responses. CONCLUSIONS: IAFM responses are significantly correlated with WRS and may provide an objective tool for examining the brain's ability to process the auditory information needed to perceive speech.

Adult↗

PubMed2004

Recording auditory steady-state responses in young infants.

OBJECTIVES: This study examined the auditory steady-state responses evoked by amplitude-modulated (AM), mixed-modulated (MM), exponentially-modulated (AM2), and frequency-modulated (FM) tones in 50 newborn infants (within 3 days of birth) and in 20 older infants (within 3-15 wk of birth). Our hypothesis was that MM and AM2 tonal stimuli would evoke larger responses than either the AM or FM tones, and that this increased size would make the responses more readily detectable. DESIGN: Multiple auditory steady-state responses were recorded to four tonal stimuli presented simultaneously to each ear at 50 dB SPL. The carrier frequencies of the stimuli were 500, 1000, 2000, and 4000 Hz and the modulation rates were between 78 and 95 Hz. Recordings lasting 12 minutes were obtained for each of the three types of modulation: 100% AM, MM (100% AM and 20% FM) and AM2. In six infants, responses to 20% FM were also recorded. RESULTS: In newborn infants, MM and AM2 stimuli produced responses that were on average 15% larger than AM stimuli. For AM, MM, and AM2 stimuli, the percentage of significant responses was 67%, 73%, 76%, respectively. Responses to FM stimuli were clearly evident in newborn infants and were about half the amplitude of the AM responses. Responses recorded in the older infants were 17% larger when evoked by MM and AM2 stimuli, rather than AM stimuli. Responses in the older infants were, on average, 32% larger and showed a higher incidence of significant responses than for infants in the first 3 days of life. For AM, MM, and AM2 stimuli, the percentage of significant responses was 82%, 82%, 84%, respectively. In both newborn and older infants, the overall percentage of significant responses was decreased by the 500 Hz results, which showed lower amplitudes and were less frequently detected than responses evoked by other frequencies. CONCLUSIONS: The responses to MM and AM2 tones were larger than those evoked by AM tones. Using these stimuli will increase the reliability and efficiency of evoked potential audiometry in infancy. Responses at 50 dB SPL are more easily detected at 3-15 wk of age than in the first few days after birth. Comprehensive frequency-specific testing of hearing using steady-state responses will likely be more accurate if postponed until after the immediate neonatal period.

Auditory Perception↗

PubMed2004

Human temporal auditory acuity as assessed by envelope following responses.

Temporal auditory acuity, the ability to discriminate rapid changes in the envelope of a sound, is essential for speech comprehension. Human envelope following responses (EFRs) recorded from scalp electrodes were evaluated as an objective measurement of temporal processing in the auditory nervous system. The temporal auditory acuity of older and younger participants was measured behaviorally using both gap and modulation detection tasks. These findings were then related to EFRs evoked by white noise that was amplitude modulated (25% modulation depth) with a sweep of modulation frequencies from 20 to 600 Hz. The frequency at which the EFR was no longer detectable was significantly correlated with behavioral measurements of gap detection (r = -0.43), and with the maximum perceptible modulation frequency (r = 0.72). The EFR techniques investigated here might be developed into a clinically useful objective estimate of temporal auditory acuity for subjects who cannot provide reliable behavioral responses.

Acoustic Stimulation↗

PubMed2004

Avoiding electromagnetic artifacts when recording auditory steady-state responses.

Electromagnetic artifacts can occur when recording multiple auditory steady-state responses evoked by sinusoidally amplitude modulated (SAM) stimuli. High-intensity air-conducted stimuli evoked responses even when hearing was prevented by masking. Additionally, high-intensity bone-conducted stimuli evoked responses that were completely different from those evoked by air-conducted stimuli of similar sensory level. These artifacts were caused by aliasing since they did not occur when recordings used high analog-digital (AD) conversion rates or when high frequencies in the electroencephalographic (EEG) signal were attenuated by steep-slope low-pass filtering. Two possible techniques can displace aliased energy away from the response frequencies: (1) using an AD rate that is not an integer submultiple of the carrier frequencies and (2) using stimuli with frequency spectra that do not alias back to the response frequencies, such as beats or "alternating SAM" tones. Alternating SAM tones evoke responses similar to conventional SAM tones, whereas beats produce significantly smaller responses.

Acoustic Stimulation↗