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At least 1,009 records · Page 56Linked to original sources
PubMed2001

L-n-acetyl-cysteine protection against cisplatin-induced auditory neuronal and hair cell toxicity.

OBJECTIVES: The aim of this study is to determine the efficacy of L-N-acetyl-cysteine (L-NAC) as a protectant for inner ear auditory sensory cells against the toxic effects of cisplatin. STUDY DESIGN: Prospective laboratory study of the otoprotective effect of L-NAC on auditory neurons and hair cells in vitro. METHODS: The study has two arms. The first arm evaluated the neuroprotective effect of L-NAC on early postpartum auditory ganglion cell cultures. Two culture media were used. The two media differed in that one of them was enhanced by the addition of neurotrophins (neurotrophin type 3 and brain-derived neurotrophic factor) and a growth factor (transforming growth factor-beta1). Then the survival of cisplatin-treated auditory neurons was studied before and after pretreatment with protective levels of L-NAC. The second arm of the study evaluated the effect of L-NAC on cisplatin damage initiated to auditory hair cells. Early-postpartum organ of Corti explants were grown in culture. Their rate of survival was studied after exposure to toxic levels of cisplatin. Then, survival of cisplatin-damaged hair cells was studied after they were pretreated with L-NAC. RESULTS: Pretreatment of cultures with L-NAC protected both auditory neurons and hair cells from the effects of exposure to toxic levels of cisplatin. This observed otoprotective effect was dose dependent. CONCLUSIONS: Our in vitro studies have demonstrated that L-NAC protected both auditory neurons and hair cells from the toxic effects of cisplatin. Because it protects both of these inner ear structures, L-NAC may be potentially useful in protecting hearing, in general, from cisplatin-induced damage. In addition, L-NAC has low systemic and mucosal toxicity. It also has a low molecular weight that may allow it to readily cross the round window membrane. All these characteristics make it potentially suitable for transtympanic application for the prevention of the ototoxicity of cisplatin in vivo.

Acetylcysteine↗
PubMed2002

Increased vulnerability of auditory system to noise exposure in mdx mice.

OBJECTIVES: Dystrophin is a cytoskeletal protein mainly found just beneath the sarcolemma. Lack of dystrophin is known to be the cause of Duchenne muscular dystrophy (DMD). Other tissues, including the brain, retina, and cochlear hair cells, also express dystrophin. Recently, a gene (Xp21.2) associated with sensorineural hearing impairment has been mapped within the localization site for dystrophin in two families. Thus, it is reasonable to assume that dystrophin may play a role in auditory function. However, animal studies have produced conflicting results. STUDY DESIGN: An attempt was made to clarify the differences between the auditory systems of dystrophin-deficient mdx mice and control B-10 mice by exposure to noise. METHODS: In the present study, mdx mice and B-10 mice were used. Animals were exposed daily to noise for 1 month, and their auditory functions were evaluated by recording the brainstem auditory evoked potentials (BAEPs). RESULTS: Before noise exposure, the mdx mouse demonstrated normal BAEP threshold when compared with the B-10 mouse. After 1 month of noise exposure, the B-10 mouse showed no apparent change in hearing threshold and BAEP latencies. In contrast, significantly increased hearing threshold and prolonged BAEP peak and interpeak latencies were observed in the mdx mouse after noise exposure. CONCLUSIONS: These results indicate that the mdx mice are more vulnerable to noise damage. This involves not only the peripheral auditory system, but also the brainstem central auditory pathway. Therefore, a significant role for dystrophin in the auditory system, especially under noise stress, is suggested.

Analysis of Variance↗
PubMed2002

Variations in gains in auditory performance from pediatric cochlear implantation.

OBJECTIVE: To investigate variations in gains in auditory performance in children with cochlear implants. STUDY DESIGN: The auditory performance of 98 children was measured with the Category of Auditory Performance survey instrument. All data were collected prospectively. Variables used to explain gain in Category of Auditory Performance were age at implantation, sex, the duration of "untreated" deafness, the year in which implantation occurred, health care inputs, and cause of hearing impairment. The data were analyzed by ordered probabilistic regression analysis. RESULTS: Gain in Category of Auditory Performance was observed to be negatively related to age at implantation, the year in which implantation took place, and the number of medical consultations the child received. None of the other variables were significant determinants of gain in Category of Auditory Performance. CONCLUSION: This study demonstrates the value of examining incremental gain from implantation rather than simply examining outcome levels. It was found that pediatric implantation is subject to diminishing returns. This suggests that further relaxation of entry criteria to implant programs should be undertaken only after careful consideration. The study also confirmed that age at implantation is an important determinant of outcomes. Greater gain in Category of Auditory Performance was experienced by those who underwent implantation at a younger age. This finding has implications for screening, as well as for purchasers and providers of implant services, highlighting the importance of responding in a timely fashion to identified need.

Auditory Threshold↗
PubMed2002

Outcome of cochlear implantation in pediatric auditory neuropathy.

OBJECTIVE: Auditory neuropathy, characterized by absence or abnormality of auditory brainstem responses and normal otoacoustic emissions, is often associated with particularly poor response to amplification. Outcome data from four such pediatric patients who received cochlear implants are discussed. STUDY DESIGN: Four patients from the Carolina Children's Communicative Disorders Program were identified as having received a diagnosis of auditory neuropathy before implantation with a Clarion cochlear implant. Speech data collected after implantation were compared with data from control pediatric implant patients, matched for age at implantation and duration of implant use. Electrically evoked auditory brainstem response data and electrically evoked acoustic reflex data were also obtained. METHODS: Routine clinical procedures were used to obtain speech outcome data. A 75-micros biphasic 21.1-Hz pulse train served as the eliciting stimulus for both evoked auditory brainstem responses and reflex measures, which were obtained contralateral to the implant. RESULTS: Speech data were comparable with those obtained from the general population of pediatric patients receiving cochlear implants at this center. Identifiable evoked auditory brainstem response data were obtained in all subjects on at least two of the three electrodes tested, and variability was comparable with that observed in other children with implants. A robust electrically evoked acoustic reflex with no decay was observed at estimated M-level in all children. CONCLUSION: The data gathered to date suggest that the outcome of cochlear implantation in these four patients is not significantly different from that in other pediatric implant patients. Physiologic data suggest that the implant was able to overcome the desynchronization hypothesized to underlie auditory neuropathy.

Child, Preschool↗
PubMed2003

Auditory brainstem implant in bilateral and completely ossified cochleae.

OBJECTIVE: To report and evaluate the results of auditory brainstem implantation in a case of postmeningitis hearing loss with totally ossified cochleae on both sides. STUDY DESIGN: Case report. SETTING: Tertiary referral center. PATIENT: A 49-year-old man was referred to the authors' department for bilateral total hearing loss subsequent to bacterial meningitis 2 years earlier. Pure tone audiometry, auditory brainstem response tests, and promontory tests did not reveal any cochlear activity. Computed tomography showed bilateral and totally ossified cochleae. Magnetic resonance imaging confirmed the diagnosis by showing no cochlear signal on T2-weighed images and ruled out brainstem and cerebellopontine angle abnormalities. INTERVENTION: A left auditory brainstem implantation was performed through a translabyrinthine route, using a Nucleus 22-channel device. MAIN OUTCOME MEASURES: Word and sentence recognition tests in sound-only and sound plus vision modes. RESULTS: No postoperative complication was observed. Twelve electrodes could be activated, and their tonotopy was defined. Nine other electrodes were inactivated because of an absence of auditory response (4 electrodes) or paresthesia (5 electrodes). At the last follow-up visit, 26 months after the implantation, 50% of disyllabic word scores and 60% of sentence scores were achieved using auditory brainstem implant sound only. These scores reached 80% and 93%, respectively, with lip-reading. CONCLUSION: Auditory brainstem implantation is an efficient means of auditory rehabilitation in cases of bilateral total hearing loss with totally ossified cochleae. It should be considered in cases of predictable failure in cochlear implantation.

Brain Stem↗
PubMed2005

Propofol attenuates responses of the auditory cortex to acoustic stimulation in a dose-dependent manner: a FMRI study.

BACKGROUND: Functional magnetic resonance imaging (fMRI) using blood-oxygen-level-dependent (BOLD) contrasts is a common method for studying sensory or cognitive brain functions. The aim of the present study was to assess the effect of the intravenous anaesthetic propofol on auditory-induced brain activation using BOLD contrast fMRI. METHODS: In eight neurosurgical patients, musical stimuli were presented binaurally in a block design. Imaging was performed under five conditions: no propofol (or wakefulness) and propofol plasma target concentrations of 0.5, 1.0, 1.5, and 2.0 microg ml(-1). RESULTS: During wakefulness we found activations in the superior temporal gyrus (STG) corresponding to the primary and secondary auditory cortex as well as in regions of higher functions of auditory information processing. The BOLD response decreased with increasing concentrations of propofol but remained partially preserved in areas of basic auditory processing in the STG during propofol 2.0 microg ml(-1). CONCLUSIONS: Our results suggest a dose-dependent impairment of central processing of auditory information after propofol administration. These results are consistent with electrophysiological findings measuring neuronal activity directly, thus suggesting a dose-dependent impairment of central processing of auditory information after propofol administration. However, propofol did not totally blunt primary cortical responses to acoustic stimulation, indicating that patients may process auditory information under general anaesthesia.

Acoustic Stimulation↗
PubMed1991

Auditory brainstem and middle latency evoked responses in the clinical evaluation of diabetes.

The measurement of auditory brainstem evoked responses and middle latency evoked responses may improve the evaluation of diabetic neuropathy. Twenty diabetic patients were studied (12 males, 8 females), aged 21 to 63 years with normal hearing, together with 20 age- and sex-matched normal subjects (10 males, 10 females). Auditory brainstem evoked responses were induced by rarefaction clicks of 0.1 ms at a repetition rate of 21.1 CPS and an intensity of 75 dB hearing level. Middle latency evoked responses were induced with clicks of 0.1 ms, a repetition rate of 7.7 CPS and an intensity of 75 dB hearing level. Diagnostic criteria were: a I-V interval latency shift greater than 2SD of the control group for the auditory brainstem evoked response test or the interval difference of wave V greater than 0.2 ms. Middle latency evoked response was diagnostic if the latency of the Pa component was greater than 2SD of normals. Twenty-five per cent of subjects had retrocochlear impairment (absence of I wave) even in the absence of symptoms. The combined technique of auditory brainstem evoked response and middle latency evoked response improved the detection rate of central nervous system dysfunction. Auditory brainstem response is important for detecting desynchronization of the auditory response, whereas middle latency evoked response detects abnormalities in the more rostral regions of the central nervous system. In conclusion, there is a role for auditory brainstem evoked response and middle latency evoked response in the global assessment of diabetic neuropathy.

Brain Stem↗
PubMed2001

Towards a measure of auditory-filter phase response.

This study investigates how the phase curvature of the auditory filters varies with center frequency (CF) and level. Harmonic tone complex maskers were used, with component phases adjusted using a variant of an equation proposed by Schroeder [IEEE Trans. Inf. Theory 16, 85-89 (1970)]. In experiment 1, the phase curvature of the masker was varied systematically and sinusoidal signal thresholds were measured at frequencies from 125 to 8000 Hz. At all signal frequencies, threshold differences of 20 dB or more were observed between the most effective and least effective masker phase curvature. In experiment 2, the effect of overall masker level on masker phase effects was studied using signal frequencies of 250, 1000, and 4000 Hz. The results were used to estimate the phase curvature of the auditory filters. The estimated relative phase curvature decreases dramatically with decreasing CF below 1000 Hz. At frequencies above 1000 Hz, relative auditory-filter phase curvature increases only slowly with increasing CF, or may remain constant. The phase curvature of the auditory filters seems to be broadly independent of overall level. Most aspects of the data are in qualitative agreement with peripheral physiological findings from other mammals, which suggests that the phase responses observed here are of peripheral origin. However, in contrast to the data reported in a cat auditory-nerve study [Carney et al., J. Acoust. Soc. Am. 105, 2384-2391 (1999)], no reversal in the sign of the phase curvature was observed at very low frequencies. Overall, the results provide a framework for mapping out the phase curvature of the auditory filters and provide constraints on future models of peripheral filtering in the human auditory system.

Adult↗
PubMed1995

Time-domain modeling of peripheral auditory processing: a modular architecture and a software platform.

A software package with a modular architecture has been developed to support perceptual modeling of the fine-grain spectro-temporal information observed in the auditory nerve. The package contains both functional and physiological modules to simulate auditory spectral analysis, neural encoding, and temporal integration, including new forms of periodicity-sensitive temporal integration that generate stabilized auditory images. Combinations of the modules enable the user to approximate a wide variety of existing, time-domain, auditory models. Sequences of auditory images can be replayed to produce cartoons of auditory perceptions that illustrate the dynamic response of the auditory system to everyday sounds.

Auditory Perception↗
PubMed1989

Auditory brain stem responses in infants with posthaemorrhagic ventricular dilatation.

Nineteen infants with posthaemorrhagic ventricular dilatation had auditory brain stem responses measured during the period of maximal ventricular dilatation. These showed various patterns ranging from normal, through various abnormalities, to complete absence of responses. When serial auditory brain stem responses were studied in parallel with the evolution of posthaemorrhagic ventricular dilatation it was seen that the abnormalities of auditory brain stem response usually resolved irrespective of the persistence or progression of ventricular dilatation. No correlation was found between cerebrospinal fluid pressure and prolonged interpeak intervals on the auditory brain stem response. In three patients with posthaemorrhagic ventricular dilatation improvement in the auditory brain stem response occurred when cerebrospinal fluid was withdrawn. Intermittent withdrawal of cerebrospinal fluid (by ventricular tap or lumbar puncture) in two of these infants was followed by improvement in the auditory brain stem response after a period of 24 hours (but not sooner). In one infant born at full term improvement in the auditory brain stem response was noted one week after shunting.

Brain Stem↗
PubMed2003

Spectrotemporal structure of receptive fields in areas AI and AAF of mouse auditory cortex.

The mouse is a promising model system for auditory cortex research because of the powerful genetic tools available for manipulating its neural circuitry. Previous studies have identified two tonotopic auditory areas in the mouse-primary auditory cortex (AI) and anterior auditory field (AAF)- but auditory receptive fields in these areas have not yet been described. To establish a foundation for investigating auditory cortical circuitry and plasticity in the mouse, we characterized receptive-field structure in AI and AAF of anesthetized mice using spectrally complex and temporally dynamic stimuli as well as simple tonal stimuli. Spectrotemporal receptive fields (STRFs) were derived from extracellularly recorded responses to complex stimuli, and frequency-intensity tuning curves were constructed from responses to simple tonal stimuli. Both analyses revealed temporal differences between AI and AAF responses: peak latencies and receptive-field durations for STRFs and first-spike latencies for responses to tone bursts were significantly longer in AI than in AAF. Spectral properties of AI and AAF receptive fields were more similar, although STRF bandwidths were slightly broader in AI than in AAF. Finally, in both AI and AAF, a substantial minority of STRFs were spectrotemporally inseparable. The spectrotemporal interaction typically appeared in the form of clearly disjoint excitatory and inhibitory subfields or an obvious spectrotemporal slant in the STRF. These data provide the first detailed description of auditory receptive fields in the mouse and suggest that although neurons in areas AI and AAF share many response characteristics, area AAF may be specialized for faster temporal processing.

Acoustic Stimulation↗
PubMed1978

External nucleus of inferior colliculus: auditory and spinal somatosensory afferents and their interactions.

1. The discharges of 129 units were studied in the external nucleus of the inferior colliculus of 11 anesthetised and paralyzed cats. This region is known to receive fibers from auditory nuclei and the dorsal column nuclei. 2. Stimuli used were pure tone bursts, monaural or binaural, tactile stimulation of the body surface, and electrical stimulation of the dorsal columns (DC) at a low cervical level and of the contralateral and ipsilateral tibial nerves. 3. Forty-six percent of units were only influenced by one type of stimulation (26% auditory, 20% DC). Of the remaining bimodally influenced units, the majority was excited by pure tone stimuli and inhibited by DC stimulation. 4. A small proportion of the total population (18%) was excited by both DC and auditory input, and units sensitive to both tones and tactile stimulation of the skin were rare (4%). 5. Auditory tuning curves were generally very broad compared with those of units in the central nucleus of the inferior colliculus. Similarly, somatic receptive fields were large and usually extended over a whole limb. 6. The majority of tone-responsive units were influenced binaurally (70%); most somatic receptive fields were located on the contralateral fore- or hindlimb (16/18). 7. The results indicate that both auditory and somatosensory information is contained in the discharges of units in the external nucleus of the inferior colliculus. 8. Speculations are made about the role of this nucleus in descending auditory input to the spinal cord and in the comparison of auditory and cutaneous information during sound-evoked coordinated body movements.

Acoustic Stimulation↗
PubMed1994

Topographic representation of auditory space in the superior colliculus of adult ferrets after monaural deafening in infancy.

1. We have investigated the role of monaural cues provided by the outer ear in the construction of a map of auditory space in the superior colliculus. Single-unit recordings were made from the superior colliculus of adult ferrets that were deprived of binaural inputs by surgically ablating the ipsilateral cochlea on postnatal day 21 or 24. 2. The spatial response properties of auditory units in the deeper layers of this nucleus were studied using white-noise bursts presented under free-field conditions in an anechoic chamber. The thresholds of the units recorded in the monaural ferrets were not significantly different from those recorded in the superior colliculus of normal adult ferrets. In both groups the unit thresholds varied by 30-50 dB in each region of the superior colliculus. 3. In normal and monaural ferrets the elevation tuning tended to be sharper than the azimuth tuning. At sound levels of approximately 10 dB above threshold the auditory units recorded in both groups of animals were tuned to a specific region of space that was restricted in azimuth and elevation. The spatial location at which the maximum response was obtained (auditory best position) varied topographically in azimuth along the rostrocaudal axis of the nucleus and in elevation along the mediolateral axis. 4. The azimuthal distribution of best positions associated with each recording location in the superior colliculus of the monaural ferrets and the alignment between this dimension of the auditory map and that of the visual map in the overlying superficial layers were no different from those found at corresponding near-threshold sound levels in normal ferrets. 5. Elevation spatial selectivity was examined in a smaller sample of units. Although elevation best positions shifted downward from the medial to the lateral side of the nucleus in both normal and monaural ferrets, we found that the topography of the auditory representation and its alignment with the visual representation were statistically different in the two groups of animals. 6. Increasing the sound level does not affect the representation of auditory space in normal ferrets. However, when the stimulus level presented to monoaural ferrets was increased, the receptive fields either expanded so that the responses were no longer tuned to any particular region of space, or the responses remained tuned but exhibited a marked shift in the value of the best position.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1998

Large-scale functional connectivity in associative learning: interrelations of the rat auditory, visual, and limbic systems.

Large-scale functional connectivity in associative learning: interrelations of the rat auditory, visual, and limbic systems. J. Neurophysiol. 80: 3148-3162, 1998. Functional relations between specialized parts of the brain may be important determinants of learned behaviors. To study this, we examined the interrelations of the auditory system with several extraauditory structures in two groups of rats having different behavioral histories. Both groups were trained to associate a tone conditional stimulus (CS) with an aversive unconditional stimulus (US). For one group, a light presented with the tone predicted the absence of the US (group TL-). In the other group, the light was a neutral stimulus (group TL0). Fluorodeoxyglucose (FDG) incorporation was measured in the presence of the tone-light compound. Because the tone-light compound was physically identical for both groups, neural differences between groups reflected differences in the learned associative properties of the stimuli. Covariances of FDG uptake in the auditory system and extraauditory structures were examined using partial least squares. Three strong covariance or functional connectivity patterns were identified. The first pattern mainly reflected similarities between groups, with strong interrelations between the subcortical auditory system and the thalamocortical visual system, cerebellum, deep cerebellar nuclei, and midline thalamus. This pattern of interactions may represent part of a common circuit for relaying the associative value of the tone CS to the cerebellum and the midline thalamus. The external nucleus of the inferior colliculus and medial division of the medial geniculate nucleus were associated more strongly with this pattern for group TL-, which was interpreted as representing the change of the associative value of the tone by the light, mediated through extraauditory influences on these two regions. A second pattern involved midbrain auditory regions, superior colliculus, zona incerta, and subiculum and was stronger for group TL0. The relations between midbrain structures may represent the excitatory conditioned response (CR) evoked by the tone in this group. The final pattern was strongest in group TL- and involved interrelations of the thalamocortical auditory system with hippocampus, basolateral amygdala, and hypothalamus. This pattern may represent the learned inhibition of the CR to the tone in the presence of the light. These findings are consistent with behavioral studies suggesting that at least two types of associations are formed during associative learning. One is the sensory relation of the stimuli and another is the relation between the CS and the affective components of the US. These behavioral associations are mapped to the patterns of functional connectivity between auditory and extraauditory regions.

Acoustic Stimulation↗
PubMedDate not supplied

Relationships between human auditory cortical structure and function.

The human auditory cortex comprises multiple areas, largely distributed across the supratemporal plane, but the precise number and configuration of auditory areas and their functional significance have not yet been clearly established. In this paper, we discuss recent research concerning architectonic and functional organisation within the human auditory cortex, as well as architectonic and neurophysiological studies in non-human species, which can provide a broad conceptual framework for interpreting functional specialisation in humans. We review the pattern in human auditory cortex of the functional responses to various acoustic cues, such as frequency, pitch, sound level, temporal variation, motion and spatial location, and we discuss their correspondence to what is known about the organisation of the auditory cortex in other primates. There is some neuroimaging evidence of multiple tonotopically organised fields in humans and of functional specialisations of the fields in the processing of different sound features. It is thought that the primary area, on Heschl's gyrus, may have a larger involvement in processing basic sound features, such as frequency and level, and that posterior non-primary areas on the planum temporale may play a larger role in processing more spectrotemporally complex sounds. Ways in which current knowledge of auditory cortical organisation and different data analysis approaches may benefit future functional neuroimaging studies which seek to link auditory cortical structure and function are discussed.

Animals↗
PubMed2003

Short-term reorganization of auditory analysis induced by phonetic experience.

Sine wave replicas of spoken words can be perceived both as nonphonetic auditory forms and as words, depending on a listener's experience. In this study, brain areas activated by sine wave words were studied with fMRI in two conditions: when subjects perceived the sounds spontaneously as nonphonetic auditory forms ("nïve condition") and after instruction and brief practice attending to their phonetic attributes ("informed condition"). The test items were composed such that half replicated natural words ("phonetic items") and the other half did not, because the tone analogs of the first and third formants had been temporally reversed ("nonphonetic items"). Subjects were asked to decide whether an isolated tone analog of the second formant (T2) presented before the sine wave word (T1234) was included in it. Experience in attending to the phonetic properties of the sinusoids interfered with this auditory matching task and was accompanied by a decrease in auditory cortex activation with word replicas but not with the acoustically matched nonphonetic items. Because the activation patterns elicited by equivalent acoustic test items depended on a listener's awareness of their phonetic potential, this indicates that the analysis of speech sounds in the auditory cortex is distinct from the simple resolution of auditory form, and is not a mere consequence of acoustic complexity. Because arbitrary acoustic patterns did not evoke the response observed for phonetic patterns, these findings suggest that the perception of speech is contingent on the presence of familiar patterns of spectral variation. The results are consistent with a short-term functional reorganization of auditory analysis induced by phonetic experience with sine wave replicas and contingent on the dynamic acoustic structure of speech.

Adolescent↗
PubMed1999

Saccadic performance as a function of the presence and disappearance of auditory and visual fixation stimuli.

Relative to when a fixated stimulus remains visible, saccadic latencies are facilitated when a fixated stimulus is extinguished simultaneously with or prior to the appearance of an eccentric auditory, visual, or combined visual-auditory target. In a study of nine human subjects, we determined whether such facilitation (the "gap effect") occurs equivalently for the disappearance of fixated auditory stimuli and fixated visual stimuli. In the present study, a fixated auditory (noise) stimulus remained present (overlap) or else was extinguished simultaneously with (step) or 200 msec prior to (gap) the appearance of a visual, auditory (tone), or combined visual-auditory target 10 degrees to the left or right of fixation. The results demonstrated equivalent facilitatory effects due to the disappearance of fixated auditory and visual stimuli and are consistent with the presumed role of the superior colliculus in the gap effect.

Acoustic Stimulation↗
PubMed1997

Auditory hallucinations and the temporal cortical response to speech in schizophrenia: a functional magnetic resonance imaging study.

OBJECTIVE: The authors explored whether abnormal functional lateralization of temporal cortical language areas in schizophrenia was associated with a predisposition to auditory hallucinations and whether the auditory hallucinatory state would reduce the temporal cortical response to external speech. METHOD: Functional magnetic resonance imaging was used to measure the blood-oxygenation-level-dependent signal induced by auditory perception of speech in three groups of male subjects: eight schizophrenic patients with a history of auditory hallucinations (trait-positive), none of whom was currently hallucinating; seven schizophrenic patients without such a history (trait-negative); and eight healthy volunteers. Seven schizophrenic patients were also examined while they were actually experiencing severe auditory verbal hallucinations and again after their hallucinations had diminished. RESULTS: Voxel-by-voxel comparison of the median power of subjects' responses to periodic external speech revealed that this measure was reduced in the left superior temporal gyrus but increased in the right middle temporal gyrus in the combined schizophrenic groups relative to the healthy comparison group. Comparison of the trait-positive and trait-negative patients revealed no clear difference in the power of temporal cortical activation. Comparison of patients when experiencing severe hallucinations and when hallucinations were mild revealed reduced responsivity of the temporal cortex, especially the right middle temporal gyrus, to external speech during the former state. CONCLUSIONS: These results suggest that schizophrenia is associated with a reduced left and increased right temporal cortical response to auditory perception of speech, with little distinction between patients who differ in their vulnerability to hallucinations. The auditory hallucinatory state is associated with reduced activity in temporal cortical regions that overlap with those that normally process external speech, possibly because of competition for common neurophysiological resources.

Adult↗