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PubMedDate not supplied

The neurophysiology of auditory perception: from single units to evoked potentials.

Evoked electric potential and magnetic field studies have the immense benefit that they can be conducted in awake, behaving humans and can be directly correlated with aspects of perception. As such, they are powerful objective indicators of perceptual properties. However, given a set of evoked potential and/or evoked field waveforms and their source locations, obtained for an exhaustive set of stimuli and stimulus contrasts, is it possible to determine blindly, i.e. predict, what the stimuli or stimulus contrasts were? If this can be done with some success, then a useful amount of information resides in scalp-recorded activity for, e.g., the study of auditory speech processing. In this review, we compare neural representations based on single-unit and evoked response activity for vowels and consonant-vowel phonemes with distinctions in formant glides and voice onset time. We conclude that temporal aspects of evoked responses can track some of the dominant response features present in single-unit activity. However, N1 morphology does not reliably predict phonetic identification of stimuli varying in voice onset time, and the reported appearance of a double-peak onset response in aggregate recordings from the auditory cortex does not indicate a cortical correlate of the perception of voicelessness. This suggests that temporal aspects of single-unit population activity are likely not inclusive enough for representation of categorical perception boundaries. In contrast to population activity based on single-unit recording, the ability to accurately localize the sources of scalp-evoked activity is one of the bottlenecks in obtaining an accessible neurophysiological substrate of perception. Attaining this is one of the requisites to arrive at the prospect of blind determination of stimuli on the basis of evoked responses. At the current sophistication level of recording and analysis, evoked responses remain in the realm of extremely sensitive objective indicators of stimulus change or stimulus differences. As such, they are signs of perceptual activity, but not comprehensive representations thereof.

Animals↗
PubMed1998

[Auditory perception disorders due to bilateral cortical lesions. An electrophysiology study].

A 78-year-old right handed man with a past history of atrial fibrillation developed in November 1994, a slight right hemiparesis with aphasia which cleared over one month. Head CT scan showed a left middle cerebral artery infarct involving the posterior part of the temporal lobe. In September 1995, a second stroke occurred. Head CT scan revealed a recent right middle cerebral artery infarct within the posterior part of temporal cortex. Auditory agnosia was diagnosed. Auditory evoked potentials recording showed bilateral dysfunction of central auditory pathways mainly over the right hemisphere. Clinical data and evoked potentials suggest that auditory agnosia might be related to the right temporal lobe damage. This later is involved in linguistic processes as suggested by positron emission tomography studies.

Aged↗
PubMed2003

Neural correlates of auditory perception in Williams syndrome: an fMRI study.

Williams syndrome (WS), a neurogenetic developmental disorder, is characterized by a rare fractionation of higher cortical functioning: selective preservation of certain complex faculties (language, music, face processing, and sociability) in contrast to marked and severe deficits in nearly every other cognitive domain (reasoning, spatial ability, motor coordination, arithmetic, problem solving). WS people are also known to suffer from hyperacusis and to experience heightened emotional reactions to music and certain classes of noise. We used functional magnetic resonance imaging to examine the neural basis of auditory processing of music and noise in WS patients and age-matched controls and found strikingly different patterns of neural organization between the groups. Those regions supporting music and noise processing in normal subjects were found not to be consistently activated in the WS participants (e.g., superior temporal and middle temporal gyri). Instead, the WS participants showed significantly reduced activation in the temporal lobes coupled with significantly greater activation in the right amygdala. In addition, WS participants (but not controls) showed a widely distributed network of activation in cortical and subcortical structures, including the brain stem, during music processing. Taken together with previous ERP and cytoarchitectonic studies, this first published report of WS using fMRI provides additional evidence of a different neurofunctional organization in WS people than normal people, which may help to explain their atypical reactions to sound. These results constitute an important first step in drawing out the links between genes, brain, cognition, and behavior in Williams syndrome.

Adolescent↗
PubMed1984

Auditory perception of speech contrasts by subjects with sensorineural hearing loss.

The goal of these studies was to find out how much of the acoustical information in amplified speech is accessible to children with varying degrees of sensorineural hearing loss. Context-varying, forced-choice tests of speech perception were presented, without feedback on performance, to orally trained subjects with better ear, three-frequency average hearing losses in the range 55-123 dB HL. As expected, average performance fell with increasing hearing loss. The values of hearing loss at which scores fell to 50% (after correction for chance) were 75 dB HL for consonant place; 85 dB HL for initial consonant voicing; 90 dB HL for initial consonant continuance; 100 dB HL for vowel place (front-back); 105 dB HL for talker sex; 115 dB HL for syllable pattern; and in excess of 115 dB HL for vowel height. Performance on the speech contrast tests was significantly correlated with the intelligibility of the subjects' own speech and with the open-set recognition of phonemes in monosyllabic words, even when pure-tone threshold was held constant.

Adolescent↗
PubMed2006

Auditory perception with ear and cold weather face protection worn in combination.

The effects on hearing thresholds, sound attenuation, and consonant discrimination of wearing a balaclava under hearing-protecting earmuffs were studied. This combination is commonly worn during cold weather military operations. One group of 20 normal-hearing adults (10 male and 10 female subjects) was tested. Within-subject measurements were made of diffuse-field hearing thresholds from 0.25 kHz to 8 kHz and consonant discrimination in quiet with the ears unoccluded and protected with the earmuffs alone and with the balaclava worn full face or rolled. Attenuation was derived from the protected and unoccluded thresholds at each frequency. When the balaclava was worn full face, attenuation decreased by 16 to 18 dB, relative to the muff alone, below 6.3 kHz. With the balaclava worn as a cap, there was an inverted U-shaped decrement in attenuation of 18 to 27 dB from 0.25 Hz to 4 kHz. Consonant discrimination decreased by 7% with the muffs alone. These findings underscore the importance of assessing protective equipment under the conditions in which it will be worn.

Adolescent↗
PubMed1997

Song transmission and auditory perception of distance in wood warblers (Parulinae)

The influence of breeding habitat on the evolution of song structure was examined in four wood warbler species of the sub-family Parulinae. The effects of song degradation on the ability of territorial paruline males to estimate distance by means of acoustic cues was also investigated. Song transmission characteristics of paruline breeding habitats were compared in southeastern Ontario, Canada; songs native to the habitat in which they were broadcast did not degrade less than foreign songs. The response of territorial paruline males to playback of 'near' (undegraded) and 'far' (degraded) conspecific songs broadcast from the same position within the territory at the same amplitude were then compared. Males responded to near songs as they would to a conspecific territorial intruder and with less intensity to far songs, suggesting that males may use cues from song degradation to estimate distance to vocal conspecifics. Our results from transmission and playback experiments are discussed with respect to the ranging hypothesis, which proposes that selection should favour males that structure songs to minimize their degradation, so that songs function to disrupt or intimidate rivals by providing unreliable distance cues.

Journal Article↗
PubMed2004

New phenomenon of abnormal auditory perception associated with emotional and head trauma: pathological confirmation by SPECT scan.

We report the case of an immigrant who suffered from death threats and head trauma while a prisoner of war in Kuwait. Two months later, he began to hear conversations that had taken place previously. These perceptions occurred spontaneously or were induced by the patient's effortful concentration. The single photon emission computerized tomography (SPECT) scan performed during this abnormal perceptual experience indicated an increase in regional cerebral blood flow in the left temporal lobe and in the brainstem.

Adult↗
PubMed1984

Auditory perception in early lateralized brain damage.

In a study of hemispheric dominance for the perception of speech the performance of 28 young children with congenital or infantile hemiplegia was compared with that of their normal peers and recently brain damage nonaphasic adults. Our results confirm Goodglass's findings that in children with early left hemisphere damage the transfer of dominance for speech processing is completed in childhood, and they show that this process of hemispheric transfer can be completed by 3 years of age. Comparison with results on adults with CVA provides additional evidence that in early lateralized brain cognitive functions normally dominant in one cerebral hemisphere are developed in the alternative hemisphere in a way that apparently does not happen later in life.

Adult↗
PubMed1995

Characterizing the dynamics of auditory perception.

After listening to a sound that is presented repeatedly, subjects report hearing different transforms of the original sound. The frequency of reported transforms is a sensitive index of some speech disorders as well as cognitive flexibility in aging. In this paper, we propose and investigate quantitative measures that characterize the dynamics of this phenomenon, known as the verbal transformation effect. In particular, we show that the distribution of the dwell time, the time spent perceiving a string of a given phonemic form before switching to another form, obeys a power law for normal subjects with an exponent valued between 1 and 2. This result suggests that within this paradigm there is no characteristic time scale for the perceptual process. Additionally, we analyze the correlation properties of the transforms. We suggest that the complexity measures and techniques introduced here might be useful diagnostic tools for a number of speech and cognitive disorders. (c) 1995 American Institute of Physics.

Journal Article↗
PubMed1996

Distinguishing detection from identification in subliminal auditory perception: a review and critique of Merikle's study.

Assertions made by Merikle (1988) regarding audio subliminal messages were tested. Seventeen participants were presented subliminal messages embedded in a white-noise cover, and three signal-to-noise (S/N) detection ratios were examined. Participants were asked to guess message presence and message content, to determine subjective/objective thresholds. Results showed that participants were unable to identify target words presented in this audio subliminal stimulus format beyond chance levels.

Adolescent↗
PubMed1982

The role of temporal factors in auditory perception of consonants and vowels. A study of different age groups.

Two series of speech identification tests were conducted in different age groups, the first test consisting of 11 synthetic speech stimuli varying in vowel length, the second test being composed of 30 natural speech stimuli varying in length of the initial consonant. Categorical perception of different phonemes was demonstrated in both experiments in all age groups. Persons more than 65 years of age showed significantly lower response percentages in both tests than did younger subjects. In the test where natural speech stimuli were used, boundaries of phoneme-category shift were dislocated in the older when compared with results of the younger subjects. Furthermore, speech discrimination was poorer in monaural than in binaural listening condition in the groups of more than 65-year-old persons with signs of age-induced sensorineural hearing loss; in this age group women showed clearly better results than men. These differences could not be demonstrated in the younger age groups.

Adolescent↗