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PubMed2004

Perfusion SPECT in cochlear implantation and promontory stimulation.

BACKGROUND: Recent studies of profoundly deaf patients with cochlear implants have demonstrated that these patients are able to process sound in the auditory cortex in a similar way to normal subjects. However, there are large variations in outcome. Various clinical criteria are used for subject selection and the decision as to which ear is to be implanted involves electrical stimulation of the promontory which is used to confirm the persistence of auditory neurones and fibres that can be utilized by the cochlear implant. In this study we have used SPECT with Tc-HMPAO to investigate activation of the auditory cortex in cochlear implantees post-surgery. In addition we also investigated whether electrical stimulation of the promontory does produce change in blood flow in the auditory cortex in pre-surgery candidates, which would indicate viable auditory networks that can be utilized by a cochlear implant device. METHODS AND RESULTS: Image analysis was performed with SPM99. Results of a simple subtraction paradigm indicated bilateral activation of auditory cortex and Wernicke's area in the post-implant group during auditory stimulus (speech) and bilateral activation of the ventral lateral posterior thalamus and bilateral auditory association cortex BA21/22/42, in the pre-implant group during electrical stimulus but no activation of the primary auditory cortex. A conjunction analysis used to investigate the common areas of activation across both groups during the stimulus condition showed that there was a common bilateral activation of the primary auditory cortex in both groups (BA22/41/42). In addition, analysis of a subset of the seven post-implant subjects who did not comprehend the speech in our study showed an activation (Pu<0.05, where Pu is the peak voxel threshold, uncorrected for multiple comparisons) in the left auditory cortex that extended into area BA22 synonymous with Wernicke's area. This supports the theory that this region has a sensory role.

Adult↗
PubMed2000

A cortical region sensitive to auditory spectral motion.

The functional architecture of human auditory cortex is still poorly understood compared with that of visual cortex, yet anatomical and electrophysiological studies in non-human primates suggest that the auditory cortex also might be functionally specialized, in a model of parallel and hierarchical organization. In particular, spectral changes such as the formant transitions of speech, or spectral motion (SM) by analogy with visual motion, could be processed in specialized cortical regions. In this study, positron emission tomography (PET) was used to identify which auditory cortical region are involved in SM analysis. We found that a bilateral secondary auditory cortical region, located in the caudal-lateral belt of auditory cortex, was more sensitive to auditory stimuli containing spectral changes than to matched stimuli with a stationary spectral profile. This result suggests that analogies between sensory systems could prove useful in the research into the functional organization of the auditory cortex.

Acoustic Stimulation↗
PubMed2002

Human cortical representation of virtual auditory space: differences between sound azimuth and elevation.

Sounds convolved with individual head-related transfer functions and presented through headphones can give very natural percepts of the three-dimensional auditory space. We recorded whole-scalp neuromagnetic responses to such stimuli to compare reactivity of the human auditory cortex to sound azimuth and elevation. The results suggest that the human auditory cortex analyses sound azimuth, based on both binaural and monaural localization cues, mainly in the hemisphere contralateral to the sound, whereas elevation in the anterior space and in the lateral auditory space in general, both strongly relying on monaural spectral cues, are analyzed in more detail in the right auditory cortex. The binaural interaural time and interaural intensity difference cues were processed in the auditory cortex around 100-150 ms and the monaural spectral cues later around 200-250 ms.

Acoustic Stimulation↗
PubMed1986

[Local cerebral blood flow and glucose metabolism in experimental meningeal carcinomatosis].

Patients with meningeal carcinomatosis often evolve signs of impairment in higher mental function. Yet, common findings of histological observation are only a sheet of tumor cells on the cortical surface, and no intracerebral mass are noted. To elucidate mechanism of mental disturbances in meningeal carcinomatosis, local cerebral blood flow and glucose metabolism were evaluated in a model of experimental meningeal carcinomatosis. Viable cells (1 X 10(4) of Walker 256 tumor were inoculated into cisterna magna of Wistar rats. Animals were used for autoradiographic study at 1 to 12 days after tumor inoculation. Local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) were measured with quantitative autoradiographic technique using 14C-iodoantipyrine and 14C-deoxyglucose as a tracer, respectively. In the early stage of tumor growth (1 to 3 days after tumor inoculation), reduction of LCGU was averaged to be 31% in the cerebral cortex and 28% in the deep structures, whereas reduction of LCBF was 28% in cerebral cortex and 19% in deep structures on average. In the late stage of tumor growth (4 to 12 days after tumor inoculation), average reduction of LCGU was 57% in the cerebral cortex and 47% in the deep structures. On the other hand, reduction of LCBF was averaged to be 42% in the cerebral cortex and 38% in the deep structures in the late stage of the disease. Reduction of LCGU and LCBF was especially evident in the sensory cortices such as parietal cortex, visual cortex and auditory cortex, and in the auditory centers of the brain stem such as medial geniculate body and inferior colliculus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

The role of predictive models in the formation of auditory streams.

Sounds provide us with useful information about our environment which complements that provided by other senses, but also poses specific processing problems. How does the auditory system distentangle sounds from different sound sources? And what is it that allows intermittent sound events from the same source to be associated with each other? Here we review findings from a wide range of studies using the auditory streaming paradigm in order to formulate a unified account of the processes underlying auditory perceptual organization. We present new computational modelling results which replicate responses in primary auditory cortex [Fishman, Y.I., Arezzo, J.C., Steinschneider, M., 2004. Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration. J. Acoust. Soc. Am. 116, 1656-1670; Fishman, Y. I., Reser, D. H., Arezzo, J.C., Steinschneider, M., 2001. Neural correlates of auditory stream segregation in primary auditory cortex of the awake monkey. Hear. Res. 151, 167-187] to tone sequences. We also present the results of a perceptual experiment which confirm the bi-stable nature of auditory streaming, and the proposal that the gradual build-up of streaming may be an artefact of averaging across many subjects [Pressnitzer, D., Hupé, J. M., 2006. Temporal dynamics of auditory and visual bi-stability reveal common principles of perceptual organization. Curr. Biol. 16(13), 1351-1357.]. Finally we argue that in order to account for all of the experimental findings, computational models of auditory stream segregation require four basic processing elements; segregation, predictive modelling, competition and adaptation, and that it is the formation of effective predictive models which allows the system to keep track of different sound sources in a complex auditory environment.

Acoustic Stimulation↗
PubMed2000

A combined functional in vivo measure for primary and secondary auditory cortices.

Auditory evoked magnetic fields are reliable physiological in vivo markers of activity generated in auditory cortices. In recent years, several components of auditory evoked fields have been demonstrated with specific topographies within the auditory cortex in man. Their differential elicitation and analyses has rendered the discrimination of neural activities in primary vs. secondary auditory cortical fields possible. This in vivo measure may be of interest in a number of (neuro)psychiatric and neuropsychological disorders with central auditory deficits, in which in vivo anatomical measures do not allow a clear distinction of primary vs. secondary auditory cortex involvement. To help better understand the pathophysiology of such disorders, we developed and introduce a combined measure of steady-state field (SSR) and the N1 component of the transient evoked field. The acoustic stimulus for this paradigm consists of a 500-ms tone burst with 39-Hz amplitude modulation of the carrier frequency. This combined stimulation allows assessment of both auditory cortex components in one brief examination to be well tolerated by patients. We examined the source locations of SSR and N1 component with separate classical stimulation and combined stimulation within-session in healthy volunteer subjects. We demonstrate here that the distinct sources of steady-state (primary auditory cortex) and N1 (secondary auditory cortex) responses can be reliably measured without significant spatial distortion with this combined stimulation paradigm.

Acoustic Stimulation↗
PubMed1998

Auditory evoked neuromagnetic response in cerebrovascular diseases: a preliminary study.

OBJECTIVES: Magnetoencephalography (MEG) measures aspects of the function of the auditory cortex of the human brain with high spatial resolution. The objective was to determine whether MEG also accurately identifies the auditory cortex of the brain in patients with ischaemic stroke. METHODS: The auditory evoked magnetic field (AEF) was examined after stimuli of 1 kHz tone bursts in 24 stroke patients without apparent infarcts in the auditory cortex, and compared the topography of sources of 50 ms (P50m) and 100 ms latency deflections (N100m), the most prominent components of middle and long latency AEFs, with that of 12 normal subjects. Cerebral haemodynamics in and around the auditory cortex were evaluated using PET. RESULTS: In nine of 24 stroke patients, the accurate magnetic sources of P50m or N100m were not identified. The distribution of P50m sources varied more widely than N100m. Eight of these nine patients had severe stenotic lesions in the carotid or middle cerebral arterial trunks. Patients with abnormal P50m responses had decreased supratemporal and hemispheric blood flow compared with patients with normal P50m responses. CONCLUSIONS: These findings suggest that large vessel disease with disturbed cerebral haemodynamics in and near the auditory cortex tend to affect AEFs, especially the middle latency components. This is the first combined study of MEG and PET to show a significant correlation between AEF responses in stroke patients and their PET indices.

Adult↗
PubMed2002

Superior temporal gyrus volumes in maltreated children and adolescents with PTSD.

BACKGROUND: The structure and function of the superior temporal gyrus (STG), a structure involved in receptive and nonverbal auditory and language processing, is understudied in posttraumatic stress disorder (PTSD). Event-related potential abnormalities were previously reported in PTSD, implicating the existence of dysfunction in the primary auditory cortex and adjacent anterior auditory cortex of the STG in adult PTSD. METHODS: Anatomic magnetic resonance imaging (MRI) volumetric analysis of the superior temporal gyrus were performed in 43 maltreated children and adolescents with PTSD and 61 nonmaltreated healthy control subjects. RESULTS: Unadjusted STG gray matter volumes were larger in maltreated subjects with PTSD than in control subjects, whereas STG white matter volumes were smaller in maltreated subjects with PTSD than in control subjects. After adjusting for differences in cerebral volume, right, left, and total superior temporal gyrus volumes were relatively larger in PTSD subjects compared with control subjects. After covarying for differences in cerebral gray matter volumes, regression analysis showed that PTSD subjects had significantly greater STG gray matter volumes in most, and in particularly right-sided STG measurements. Furthermore, findings of significant side-by-diagnosis interactions for STG and STG gray but not white matter STG volumes suggest that there is a more pronounced right > left asymmetry in total and posterior STG volumes but a loss of the left > right asymmetry seen in total, anterior, and posterior STG gray matter volumes in PTSD subjects compared with control subjects. CONCLUSIONS: These STG findings may suggest developmental alterations in maltreatment-related pediatric PTSD.

Adolescent↗
PubMed1988

Parahippocampal projections to posterior auditory association cortex (area Tpt) in Old-World monkeys.

Retrograde and anterograde tracing methods were used to study the connections between the parahippocampal gyrus and the posterior auditory association cortex (area Tpt) in the Old-World monkey. Nine monkeys received injections of tritiated amino acids in different areas of the parahippocampal gyrus, and three monkeys received injections of the retrograde tracer fast blue in area Tpt of the auditory association cortex. It was observed that the medial part of the posterior portion of the parahippocampal gyrus (area TH) gives rise to projections that terminate in layers I-III of area Tpt. Using complementary retrograde tracing experiments, the cells of origin for this projection were identified in layers V and VI of area TH. The findings reveal a direct structural coupling between auditory association cortices and a temporal region thought to play a role in learning and memory. These connections may form part of a neural system in the monkey that is related to acoustic learning and memory. Homologous systems in humans may be involved in auditory learning and language acquisition.

Amino Acids↗
PubMed2005

The C50m response: conditioned magnetocerebral activity recorded from the human brain.

Recent advances in neuroimaging technology now permit a precise determination of the dynamics of specific neural activity underlying human associative learning. We used magnetoencephalography (MEG) to characterize the dynamics of conditioned responses (CRs) within auditory cortex during habituation, delay and trace conditioning training, and delay conditioning extinction. Conditioned stimuli (CS) were visually presented geometric figures, and unconditioned stimuli (US) were aversive noise bursts. CS+ stimuli were paired with the US on 50% of presentations: CS- stimuli were never paired with the US. Auditory cortex was activated following the paired CS+ at an average of 49-62 ms following US onset. Our data support the presence of a differential conditioned response (C50m) in auditory cortex following the unpaired CS+ at an average of 30-61 ms after US omission. The current source strength of the auditory C50m was subsequently quantified for the unpaired CS+ and CS- during training, the unpaired CS+ during extinction, and habituation. During delay and trace training, the C50m was stronger for the unpaired CS+ than for the CS-, and was also stronger for the unpaired CS+ during training compared to both habituation and extinction. This is the first description of magnetocerebral conditioning in normal human auditory cortex. The C50m activity in auditory cortex elicited by visual stimuli constitutes a direct observation of associative neural plasticity within the human auditory cortex.

Adult↗
PubMed2006

Sound localization during homotopic and heterotopic bilateral cooling deactivation of primary and nonprimary auditory cortical areas in the cat.

Although the contributions of primary auditory cortex (AI) to sound localization have been extensively studied in a large number of mammals, little is known of the contributions of nonprimary auditory cortex to sound localization. Therefore the purpose of this study was to examine the contributions of both primary and all the recognized regions of acoustically responsive nonprimary auditory cortex to sound localization during both bilateral and unilateral reversible deactivation. The cats learned to make an orienting response (head movement and approach) to a 100-ms broad-band noise stimulus emitted from a central speaker or one of 12 peripheral sites (located in front of the animal, from left 90 degrees to right 90 degrees , at 15 degrees intervals) along the horizontal plane after attending to a central visual stimulus. Twenty-one cats had one or two bilateral pairs of cryoloops chronically implanted over one of ten regions of auditory cortex. We examined AI [which included the dorsal zone (DZ)], the three other tonotopic fields [anterior auditory field (AAF), posterior auditory field (PAF), ventral posterior auditory field (VPAF)], as well as six nontonotopic regions that included second auditory cortex (AII), the anterior ectosylvian sulcus (AES), the insular (IN) region, the temporal (T) region [which included the ventral auditory field (VAF)], the dorsal posterior ectosylvian (dPE) gyrus [which included the intermediate posterior ectosylvian (iPE) gyrus], and the ventral posterior ectosylvian (vPE) gyrus. In accord with earlier studies, unilateral deactivation of AI/DZ caused sound localization deficits in the contralateral field. Bilateral deactivation of AI/DZ resulted in bilateral sound localization deficits throughout the 180 degrees field examined. Of the three other tonotopically organized fields, only deactivation of PAF resulted in sound localization deficits. These deficits were virtually identical to the unilateral and bilateral deactivation results obtained during AI/DZ deactivation. Of the six nontonotopic regions examined, only deactivation of AES resulted in sound localization deficits in the contralateral hemifield during unilateral deactivation. Although bilateral deactivation of AI/DZ, PAF, or AES resulted in profound sound localization deficits throughout the entire field, the cats were generally able to orient toward the hemifield that contained the acoustic stimulus, but not accurately identify the location of the stimulus. Neither unilateral nor bilateral deactivation of areas AAF, VPAF, AII, IN, T, dPE, nor vPE had any effect on the sound localization task. Finally, bilateral heterotopic deactivations of AI/DZ, PAF, or AES yielded deficits that were as profound as bilateral homotopic cooling of any of these sites. The fact that deactivation of any one region (AI/DZ, PAF, or AES) was sufficient to produce a deficit indicated that normal function of all three regions was necessary for normal sound localization. Neither unilateral nor bilateral deactivation of AI/DZ, PAF, or AES affected the accurate localization of a visual target. The results suggest that hemispheric deactivations contribute independently to sound localization deficits.

Acoustic Stimulation↗
PubMed1990

Interconnections of the auditory cortical fields of the cat with the cingulate and parahippocampal cortices.

The interconnections of the auditory cortex with the parahippocampal and cingulate cortices were studied in the cat. Injections of the anterograde and retrograde tracer WGA-HRP were performed, in different cats (n = 9), in electrophysiologically identified auditory cortical fields. Injections in the posterior zone of the auditory cortex (PAF or at the PAF/AI border) labeled neurons and axonal terminal fields in the cingulate gyrus, mainly in the ventral bank of the splenial sulcus (a region that can be considered as an extension of the cytoarchitectonic area Cg), and posteriorly in the retrosplenial area. Labeling was also present in area 35 of the perirhinal cortex, but it was sparser than in the cingulate gyrus. Following WGA-HRP injection in AII, no labeling was found in the cingulate gyrus, but a few neurons and terminals were labeled in area 35. In contrast, no or very sparse labeling was observed in the cingulate and perirhinal cortices after WGA-HRP injections in the anterior zone of the auditory cortex (AI or AAF). A WGA-HRP injection in the cingulate gyrus labeled neurons in the posterior zone of the auditory cortex, between the posterior ectosylvian and the posterior suprasylvian sulci, but none was found more anteriorly in regions corresponding to AI, AAF and AII. The present data indicate the existence of preferential interconnections between the posterior auditory cortex and the limbic system (cingulate and parahippocampal cortices). This specialization of posterior auditory cortical areas can be related to previous observations indicating that the anterior and posterior regions of the auditory cortex differ from each other by their response properties to sounds and their pattern of connectivity with the auditory thalamus and the claustrum.

Animals↗
PubMed2005

Magnetoencephalography and positron emission tomography studies of a patient with auditory agnosia caused by bilateral lesions confined to the auditory radiations.

The aim of this study was to investigate auditory cortex function in the context of auditory stimuli in a patient with auditory agnosia due to bilateral lesions confined to the auditory radiations. A male patient experienced mild left temporal hemiplegia because of right putaminal hemorrhage at the age of 43 years. Thereafter he recovered completely but hypertension persisted. When he was 53 years old, he suffered left putaminal hemorrhage and went into a coma. After recovering from the coma and right hemiplegia he could hear but could not discriminate speech sounds. Brain CT and MRI demonstrated small bilateral lesions confined to the auditory radiations. Magnetoencephalography demonstrated the disappearance of middle latency responses and auditory-evoked potential studies showed a very small Pa peak. In contrast, a positron emission tomography study demonstrated a marked increase in blood flow in the bilateral auditory cortex in response to both click and monosyllable stimuli. It is speculated that the auditory cortex receives functional projections from the cochlea via non-specific pathways in the cerebral hemispheres.

Agnosia↗
PubMed2002

Modulatory effect of cortical activation on the lemniscal auditory thalamus of the Guinea pig.

In the present study, we investigated the point-to-point modulatory effects from the auditory cortex to the thalamus in the guinea pig. Corticofugal modulation on thalamic neurons was studied by electrical activation of the auditory cortex. The modulation effect was sampled along the frontal or sagittal planes of the auditory thalamus, focusing on the ventral division (MGv) of the medial geniculate body (MGB). Electrical activation was targeted at the anterior and dorsocaudal auditory fields, to which the MGv projects and from which it assumptively receives reciprocal projections. Of the 101 MGv neurons examined by activation of the auditory cortex through passing pulse trains of 100-200 microA current into one after another of the three implanted electrodes (101 neurons x 3 stimulation sites = 303 cases), 208 cases showed a facilitatory effect, 85 showed no effect, and only 10 cases (7 neurons) showed an inhibitory effect. Among the cases of facilitation, 63 cases showed a facilitatory effect >100%, and 145 cases showed a facilitatory effect from 20-100%. The corticofugal modulatory effect on the MGv of the guinea pig showed a widespread, strong facilitatory effect and very little inhibitory effect. The MGv neurons showed the greatest facilitations to stimulation by the cortical sites, with the closest correspondence in BF. Six of seven neurons showed an elevation of the rate-frequency functions when the auditory cortex was activated. The comparative results of the corticofugal modulatory effects on the MGv of the guinea pig and the cat, together with anatomical findings, hint that the strong facilitatory effect is generated through the strong corticothalamic direct connection and that the weak inhibitory effect might be mainly generated via the interneurons of the MGv. The temporal firing pattern of neuronal response to auditory stimulus was also modulated by cortical stimulation. The mean first-spike latency increased significantly from 15.7 +/- 5.3 ms with only noise-burst stimulus to 18.3 +/- 4.9 ms (n = 5, P < 0.01, paired t-test), while the auditory cortex was activated with a train of 10 pulses. Taking these results together with those of previous experiments conducted on the cat, we speculate that the relatively weaker inhibitory effect compared with that in the cat could be due to the smaller number of interneurons in the guinea pig MGB. The corticofugal modulation of the firing pattern of the thalamic neurons might enable single neurons to encode more auditory information using not only the firing rate but also the firing pattern.

Acoustic Stimulation↗
PubMed1997

Regional differences in synaptogenesis in human cerebral cortex.

The formation of synaptic contacts in human cerebral cortex was compared in two cortical regions: auditory cortex (Heschl's gyrus) and prefrontal cortex (middle frontal gyrus). Synapse formation in both cortical regions begins in the fetus, before conceptual age 27 weeks. Synaptic density increases more rapidly in auditory cortex, where the maximum is reached near postnatal age 3 months. Maximum synaptic density in middle frontal gyrus is not reached until after age 15 months. Synaptogenesis occurs concurrently with dendritic and axonal growth and with myelination of the subcortical white matter. A phase of net synapse elimination occurs late in childhood, earlier in auditory cortex, where it has ended by age 12 years, than in prefrontal cortex, where it extends to midadolescence. Synaptogenesis and synapse elimination in humans appear to be heterochronous in different cortical regions and, in that respect, appears to differ from the rhesus monkey, where they are concurrent. In other respects, including overproduction of synaptic contacts in infancy, persistence of high levels of synaptic density to late childhood or adolescence, the absolute values of maximum and adult synaptic density, and layer specific differences, findings in the human resemble those in rhesus monkeys.

Auditory Cortex↗
PubMed2006

The neurochemical basis of human cortical auditory processing: combining proton magnetic resonance spectroscopy and magnetoencephalography.

BACKGROUND: A combination of magnetoencephalography and proton magnetic resonance spectroscopy was used to correlate the electrophysiology of rapid auditory processing and the neurochemistry of the auditory cortex in 15 healthy adults. To assess rapid auditory processing in the left auditory cortex, the amplitude and decrement of the N1m peak, the major component of the late auditory evoked response, were measured during rapidly successive presentation of acoustic stimuli. We tested the hypothesis that: (i) the amplitude of the N1m response and (ii) its decrement during rapid stimulation are associated with the cortical neurochemistry as determined by proton magnetic resonance spectroscopy. RESULTS: Our results demonstrated a significant association between the concentrations of N-acetylaspartate, a marker of neuronal integrity, and the amplitudes of individual N1m responses. In addition, the concentrations of choline-containing compounds, representing the functional integrity of membranes, were significantly associated with N1m amplitudes. No significant association was found between the concentrations of the glutamate/glutamine pool and the amplitudes of the first N1m. No significant associations were seen between the decrement of the N1m (the relative amplitude of the second N1m peak) and the concentrations of N-acetylaspartate, choline-containing compounds, or the glutamate/glutamine pool. However, there was a trend for higher glutamate/glutamine concentrations in individuals with higher relative N1m amplitude. CONCLUSION: These results suggest that neuronal and membrane functions are important for rapid auditory processing. This investigation provides a first link between the electrophysiology, as recorded by magnetoencephalography, and the neurochemistry, as assessed by proton magnetic resonance spectroscopy, of the auditory cortex.

Acoustic Stimulation↗
PubMed1984

Temporal lobe lesions and perception of species-specific vocalizations by macaques.

Japanese macaques were trained to discriminate two forms of their coo vocalization before and after unilateral and bilateral ablation of the temporal cortex. Unilateral ablation of the left superior temporal gyrus, including auditory cortex, resulted in an initial impairment in the discrimination, but similar unilateral ablation of the right superior temporal gyrus had no effect. Bilateral temporal lesions including auditory cortex completely abolished the ability of the animals to discriminate their coos. Neither unilateral nor bilateral ablation of cortex dorsal to and sparing the auditory cortex had any effect on the discrimination. The perception of species-specific vocalizations by Japanese macaques seems to be mediated by the temporal cortex, with the left hemisphere playing a predominant role.

Animals↗
PubMed2005

Development of auditory evoked fields in human fetuses and newborns: a longitudinal MEG study.

OBJECTIVE: To investigate the maturation of the auditory cortex by non-invasive recording of auditory evoked magnetic fields in human fetuses and newborns with the relatively novel and completely non-invasive technology of MEG. METHODS: Serial recordings were performed every 2 weeks on 18 fetuses beginning from week 27 of gestational age until term with a follow-up recording on the newborn. Auditory stimulation consisted of tone bursts in an oddball design with standard tones and deviant tones. RESULTS: In 52 of 63 fetal and in all of the neonatal recordings an auditory evoked magnetic field was obtained. A decrease in latency with increasing age of the subjects was observed in the combined analysis of fetuses and neonates. CONCLUSIONS: With advanced study using MEG, 83% of the measurements showed auditory evoked fields in fetuses that correspond with existing literature in electrophysiology in the past. These findings indicate that MEG is a technique that can be used to investigate maturation of the auditory cortex based on auditory evoked fields in fetuses and neonates. SIGNIFICANCE: Maturational changes have been examined in the past. With the use of this novel technique, applied to a serial study, it is possible to trace the development of auditory responses in utero and newborns.

Adult↗