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PubMed2006

Cortical connections of the auditory cortex in marmoset monkeys: core and medial belt regions.

The auditory cortex of primates contains a core region of three primary areas surrounded by a belt region of secondary areas. Recent neurophysiological studies suggest that the belt areas medial to the core have unique functional roles, including multisensory properties, but little is known about their connections. In this study and its companion, the cortical and subcortical connections of the core and medial belt regions of marmoset monkeys were compared to account for functional differences between areas and refine our working model of the primate auditory cortex. Anatomical tracer injections targeted two core areas (A1 and R) and two medial belt areas (rostromedial [RM] and caudomedial [CM]). RM and CM had topographically weighted connections with all other areas of the auditory cortex ipsilaterally, but these were less widespread contralaterally. CM was densely connected with caudal auditory fields, the retroinsular (Ri) area of the somatosensory cortex, the superior temporal sulcus (STS), and the posterior parietal and entorhinal cortex. The connections of RM favored rostral auditory areas, with no clear somatosensory inputs. RM also projected to the lateral nucleus of the amygdala and tail of the caudate nucleus. A1 and R had topographically weighted connections with medial and lateral belt regions, infragranular inputs from the parabelt, and weak connections with fields outside the auditory cortex. The results indicated that RM and CM are distinct areas of the medial belt region with direct inputs from the core. CM also has somatosensory input and may correspond to an area on the posteromedial transverse gyrus of humans and the anterior auditory field of other mammals.

Acoustic Stimulation↗
PubMed1992

Subdivisions and connections of auditory cortex in owl monkeys.

The organization and connections of auditory cortex in owl monkeys, Aotus trivirgatus, were investigated by combining microelectrode mapping methods with studies of architecture and connections in the same animals. In most experiments, portions of auditory cortex were first explored with microelectrodes, neurons were characterized as responsive or not to auditory stimuli, and best frequencies were determined whenever possible. Most recordings were in cortex previously designated as primary (A-I) and rostral (R) auditory fields (Imig et al. J Comp Neurol 171:111, '77) and in a newly defined rostrotemporal field (RT) located rostral to R. Injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and fluorescent tracers were placed in electrophysiologically identified locations of A-I, R, and RT; the posterolateral (PL) and anterolateral (AL) divisions of a narrow belt of auditory cortex lateral and adjacent to A-I and R; cortex of the superior temporal gyrus lateral and rostrolateral to PL and AL; and regions of prefrontal cortex that receive inputs from auditory cortex. There were several major findings: 1. Best frequencies were most clearly determined for neurons within a densely myelinated strip of cortex on the lower bank and lip of the lateral sulcus. We divided this strip into three fields, A-I, R, and RT, although an alternative interpretation that A-I and R are parts of a single field remains tenable. In some cases, isofrequency contours appeared to continue uninterrupted across fields A-I and R, with lower frequencies represented laterally and higher frequencies represented deeper in the sulcus. In other cases, there was a tendency for high frequencies to be represented caudally and medially, and low frequencies laterally in A-I and rostrally in R, with partial discontinuity in the isofrequency contours. A reversal of the tonotopic gradient appeared in RT with a common low-frequency representation at the caudal border with R, and progressively higher frequencies encountered rostrally. Of the three fields, A-I appears slightly more myelinated than R, and RT slightly less than R. The distinctiveness of the three fields is further demonstrated by the patterns of connections. In particular, A-I and RT are both interconnected with R, but not with each other. Connections between A-I and R are between tonotopically matched locations. 2. A narrow 2-3 mm wide band of cortex lateral to A-I, R, and RT was also responsive to auditory stimuli, but typically neurons were more difficult to activate, and best frequencies were more difficult to determine. No distinctions in myeloarchitecture or CO activity were obvious.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1999

Event-related fMRI of the auditory cortex.

An event-related protocol was designed to permit auditory fMRI studies minimally affected by the echo-planar noise artifact; a long time interval (TR = 10 s) between each cerebral volume acquisition was combined with stroboscopic data acquisition, and event-related curves were reconstructed with a 1-s resolution. The cerebral hemodynamic-response time course to a target auditory stimulus was measured in five individual subjects using this method. Clear bell-shaped event-related responses were observed bilaterally in all individuals in primary auditory cortex (A1) as well as in laterally extending secondary cortical fields. Group-average event-related curves attained their maxima (0.5-0.7%) 3 s after stimulus onset in A1 (4 s for more anterior and lateral regions of auditory cortex), and signal had returned to near-baseline level 6 s after stimulus onset. The stroboscopic event-related method appeared effective in minimizing effects of the interaction between scanning noise and experimental auditory stimulation; it adds useful temporal information to the spatial resolution afforded by fMRI in studies of human auditory function, while allowing presentation of auditory stimuli on a silent background.

Acoustic Stimulation↗
PubMed2005

Electrically evoked hearing perception by functional neurostimulation of the central auditory system.

Perceptional benefits and potential risks of electrical stimulation of the central auditory system are constantly changing due to ongoing developments and technical modifications. Therefore, we would like to introduce current treatment protocols and strategies that might have an impact on functional results of auditory brainstem implants (ABI) in profoundly deaf patients. Patients with bilateral tumours as a result of neurofibromatosis type 2 with complete dysfunction of the eighth cranial nerves are the most frequent candidates for auditory brainstem implants. Worldwide, about 300 patients have already received an ABI through a translabyrinthine or suboccipital approach supported by multimodality electrophysiological monitoring. Patient selection is based on disease course, clinical signs, audiological, radiological and psycho-social criteria. The ABI provides the patients with access to auditory information such as environmental sound awareness together with distinct hearing cues in speech. In addition, this device markedly improves speech reception in combination with lip-reading. Nonetheless, there is only limited open-set speech understanding. Results of hearing function are correlated with electrode design, number of activated electrodes, speech processing strategies, duration of pre-existing deafness and extent of brainstem deformation. Functional neurostimulation of the central auditory system by a brainstem implant is a safe and beneficial procedure, which may considerably improve the quality of life in patients suffering from deafness due to bilateral retrocochlear lesions. The auditory outcome may be improved by a new generation of microelectrodes capable of penetrating the surface of the brainstem to access more directly the auditory neurons.

Auditory Perception↗
PubMed1987

Correlation between auditory evoked responses in the thalamus and species-specific call characteristics. I. Rana catesbeiana (Anura: Ranidae).

This evoked potential study of the bullfrog's auditory thalamic area (an auditory responsive region in the posterior dorsal thalamus) shows that complex processing, distinct from that reported in lower auditory regions, occurs in this center. An acoustic stimulus consisting of two tones, one which stimulates either the low-frequency or the mid-frequency sensitive population of auditory nerve fibers from the amphibian papilla and the other the high-frequency sensitive population of fibers from the basilar papilla, evoked a maximal response. The amplitude of the response to the simultaneous stimulation of the two auditory organs was, in some locations, much larger than the linear sum of the responses to the individual tones presented separately. Bimodal spectral stimuli that had relatively long rise-times (greater than or equal to 100 ms) evoked much larger responses than similar sounds with short rise-times. The optimal rise-times were close to those occurring in the bullfrog's mating call. The response was dependent on the waveform periodicity and harmonic content, with a fundamental frequency of 200 Hz producing a larger response than those with fundamentals of 50, 100 or 300 Hz. Six of the natural calls in the bullfrog's vocal repertoire were tested and the mating call and warning call were found to evoke the best responses. Each of these calls stimulate the two auditory organs simultaneously. The evoked response had a long refractory period which could not be altered by lesioning the efferent telencephalic pathways. The type of spectral and temporal information extracted by the auditory thalamic area suggests that this center is involved in processing complex sounds and likely plays an important role in the bullfrog's detection of some of its vocal signals.

Acoustic Stimulation↗
PubMed1997

The auditory cortex of the house mouse: left-right differences, tonotopic organization and quantitative analysis of frequency representation.

Multi-unit electrophysiological mapping was used to establish the area of the left- and right-hemisphere auditory cortex (AC) of the mouse and to characterize various fields within the AC. The AC of the left hemisphere covered a significantly larger (factor of 1.30) area compared to that of the right side. Based on best-frequency (BF) maps and other neuronal response characteristics to tone and noise bursts, five fields (primary auditory field, anterior auditory field, second auditory field, ultrasonic field, dorsoposterior field) and two small non-specified areas could be delimited on both hemispheres. The relative sizes of these fields and areas were similar on both sides. The primary and anterior auditory fields were tonotopically organized with counter running frequency gradients merging in the center of the AC. These fields covered BF ranges up to about 45 kHz. Higher BFs up to about 70 kHz were represented non-tonotopically in the separate ultrasonic field, part of which may be considered as belonging to the primary field. The dorsoposterior and second auditory fields were non-tonotopically organized and neurons had special response properties. These characteristics of the mouse AC were compared with auditory cortical maps of other mammals.

Acoustic Stimulation↗
PubMed1986

Auditory response properties of neurons in the anterior ectosylvian sulcus of the cat.

The auditory response properties of single neurons in the fundus and banks of the anterior ectosylvian sulcus (AES) were studied with simple dichotic stimuli (viz. noise- and tone-bursts) in cats anaesthetized with alpha-chloralose. Neurons within AES showed simple onset responses, were most commonly excited by stimulation of both ears, and showed either broad tuning or multiple high best frequencies. Some neurons were also tested for visual responsiveness and it was found that auditory cells and visual cells were intermingled within the sulcus. A small percentage of cells responded to both auditory and visual stimulation. Overall, the response properties of AES neurons differed from those of nearby auditory cortical fields. The region of AES studied appears to be outside the recently defined fourth somatosensory area (SIV), but overlaps para-SIV found deeper in the sulcus. It appears that deep within the sulcus and along most of its length there is a population of auditory, somatosensory and visual cells; to delineate this auditory population from the surrounding auditory cortical fields this region has been designated Field AES.

Animals↗
PubMed1989

A study of proteins in the auditory system of rabbits using two-dimensional gels: identification of glial fibrillary acidic protein and vitamin D-dependent calcium binding protein.

Two-dimensional gel electrophoresis and computerized optical densitometry were employed to compare the relative content of proteins across major auditory brain regions in rabbits. Areas examined included the dorsal and ventral cochlear nuclei which receive the primary afferents from the organ of Corti, the lateral superior olivary nucleus which has strong reciprocal relationships with the cochlear nucleus, and the successively more rostral projections of the auditory pathways to inferior colliculus, medial geniculate and auditory cortex. Twelve proteins demonstrated significant decreases and 5 proteins significant increases in content at successively more rostral levels of the auditory system, including 2 proteins which were highly localized to the cochlear nuclei and 2 proteins greatest in amounts in the auditory cortex. One protein which was localized to the cochlear nuclei and lateral superior olive (molecular weight (MW) = 50.3, isoelectric point (pI) = 5.7) was identified as the glial fibrillary acidic protein by reaction of specific antisera on blots. Antisera to the vitamin D-dependent calcium binding protein reacted specifically with one protein (MW = 27.2, pI = 4.8) which was greatest in amount in the lateral superior olive (LSO) versus other auditory regions examined. The significance of these findings rests in the potential for identifying specific markers for cellular elements that are important in auditory function and which might be lost as a consequence of developmental abnormalities or other traumas.

Animals↗
PubMed1994

Detection of stimulus deviance within primate primary auditory cortex: intracortical mechanisms of mismatch negativity (MMN) generation.

Mismatch negativity (MMN) is a cognitive, auditory event-related potential (AEP) that reflects preattentive detection of stimulus deviance and indexes the operation of the auditory sensory ('echoic') memory system. MMN is elicited most commonly in an auditory oddball paradigm in which a sequence of repetitive standard stimuli is interrupted infrequently and unexpectedly by a physically deviant 'oddball' stimulus. Electro- and magnetoencephalographic dipole mapping studies have localized the generators of MMN to supratemporal auditory cortex in the vicinity of Heschl's gyrus, but have not determined the degree to which MMN reflects activation within primary auditory cortex (AI) itself. The present study, using moveable multichannel electrodes inserted acutely into superior temporal plane, demonstrates a significant contribution of AI to scalp-recorded MMN in the monkey, as reflected by greater response of AI to loud or soft clicks presented as deviants than to the same stimuli presented as repetitive standards. The MMN-like activity was localized primarily to supragranular laminae within AI. Thus, standard and deviant stimuli elicited similar degrees of initial, thalamocortical excitation. In contrast, responses within supragranular cortex were significantly larger to deviant stimuli than to standards. No MMN-like activity was detected in a limited number to passes that penetrated anterior and medial to AI. AI plays a well established role in the decoding of the acoustic properties of individual stimuli. The present study demonstrates that primary auditory cortex also plays an important role in processing the relationships between stimuli, and thus participates in cognitive, as well as purely sensory, processing of auditory information.

Acoustic Stimulation↗
PubMed1985

Functioning of the brain-stem auditory pathway in non-retarded autistic individuals.

Functioning of auditory brain-stem pathways was examined in non-retarded autistic individuals (14-28 years of age). Functioning was assessed by recording ERPs (event-related brain potentials) generated by these auditory pathways. These ERPs were evoked by click stimuli and occurred within the first 8 msec following the onset of the click. To assess the ability of these early auditory pathways to process sensory stimuli of varying characteristics, we systematically varied click intensity, rate of stimulation, ear of stimulation, and polarity of clicks. The results show that non-retarded autistic individuals have normal functioning of the brain-stem auditory pathways which generate these ERPs: every autistic subject had normal ERPs. So, disorder in auditory brain-stem pathways which generate these ERPs is not necessary for autism to occur. The dysfunctioning neural systems directly responsible for autism in non-retarded individuals must be sought elsewhere. Ten of the autistic subjects in this study, whom we found to have normal auditory brain-stem ERPs, had previously been found to have abnormalities in longer latency cognitive ERP components (Courchesne et al. 1984, 1985). We conclude, therefore, that those abnormalities in longer latency components are not the downstream consequences of abnormalities in the structures generating the auditory brain-stem ERPs recorded in the present study.

Adolescent↗
PubMed1992

Intermodal selective attention. II. Effects of attentional load on processing of auditory and visual stimuli in central space.

The effect of processing load on event-related brain potentials (ERPs) was investigated in an intermodal selective attention task in which subjects attended selectively to auditory or visual stimuli. Processing load was manipulated by requiring subjects to detect either difficult-to-detect (deviant) or easy-to-detect (DEVIANT) targets in separate blocks of trials. Attention to auditory stimuli was associated with negative (Nda, 90-170 msec) and positive (Pda, 190-270 msec) enhancements in the ERPs to auditory stimuli. The Nda increased in amplitude with increasing processing load. Deviant auditory stimuli occurring among auditory standard stimuli elicited frontally distributed mismatch negativities (MMNs). The MMN persisted during visual attention and was unaffected by visual processing load. However, the MMN to deviants but not DEVIANTS was enhanced in amplitude with auditory attention. Attention to visual stimuli resulted in positive (Pdv, latency 70-130 msec) and negative (Ndv, 170-270 msec) modulations of visual ERPs, that increased with increasing processing load. Prominent visual deviance-related negativities were observed at occipital and infero-temporal scalp sites (latencies 90-290 msec), but only to DEVIANT visual stimuli. The early MMN-like portion of the visual deviance-related negativity was independent of attention, with equal amplitudes during different auditory and visual conditions.

Acoustic Stimulation↗
PubMedDate not supplied

Frequency selectivity in the auditory periphery: similarities between damaged and developing ears.

Single fiber tuning curves (stimulus frequency versus neural threshold curves) were obtained from 198 auditory nerve fibers in 24 kittens between birth and the 16th postnatal day and from 74 auditory nerve fibers in adult cats. Three developmental stages during which adult-like frequency-resolving capacity was acquired were identified. During the early stage of postnatal development, all auditory nerve fibers were essentially untuned and responded to a narrow range of low to middle frequency tone bursts presented at intensities exceeding 110 dB sound pressure level (SPL) re 20 muPa. In the intermediate stage, which occurred during the second postnatal week, auditory nerve fibers tuned to low- and mid-range frequencies acquired adult-like frequency-resolving capacity. Fibers tuned to high frequencies, which were recorded later in development than those tuned to lower frequencies, were as sharply tuned as their adult counterparts, but exhibited a low contrast between thresholds at characteristic frequency (tip) and lower (tail) frequencies (ie, low tip-to-tail ratios). Adult-like tuning curves were observed during the third stage, primarily as a consequence of the acquisition of adult-like tip-to-tail ratios. Our understanding of the cochlear mechanism(s) by which frequency selectivity is produced in adult animals has recently been enhanced by a combined anatomy and physiology investigation conducted by Liberman and Dodds, in which clear anatomic foci of cochlear damage were identified in cats with functionally characterized hearing loss. Similarly, descriptions of anatomic differentiation in the feline auditory end-organ correlate with functional measures of peripheral auditory system development. In this report, anatomic and physiologic similarities between developing and damaged ears are considered in an attempt to better characterized the process whereby normal frequency selectivities and thresholds are developed. Our findings support the notion that anatomic changes in the cochlea during development, primarily the development of adult-like anatomic relations between the tectorial membrane and sensory cells, underlie the acquisition of adult-like auditory nerve fiber tuning.

Age Factors↗
PubMed1995

The temporal relationship between the brainstem and primary cortical auditory evoked potentials.

Many methods are employed in order to define more precisely the generators of an evoked potential (EP) waveform. One technique is to compare the timing of an EP whose origin is well established with that of one whose origin is less certain. In the present article, the latency of the primary cortical auditory evoked potential (PCAEP) was compared to each of the seven subcomponents which compose the brainstem auditory evoked potential (BAEP). The data for this comparison was derived from a retrospective analysis of previous recordings of the PCAEP and BAEP. Central auditory conduction time (CACT) was calculated by subtracting the latency of the cochlear nucleus BAEP component (wave III) from that of the PCAEP. It was found that CACT in humans is 12 msec which is more than double that of central somatosensory conduction time. The interpeak latencies between BAEP waves V, VI, and VII and the PCAEP were also calculated. It was deduced that all three waves must have an origin rather more caudally within the central auditory system than is commonly supposed. In addition, it is demonstrated that the early components of the middle latency AEP (No and Na) largely reside within the time domain between the termination of the BAEP components and the PCAEP which would be consistent with their being far field reflections of midbrain and subcortical auditory activity. It is concluded that as the afferent volley ascends the central auditory pathways, it generates not a sequence of high frequency BAEP responses but rather a succession of slower post-synaptic waves. The only means of reconciling the timing of the BAEP waves with that of the PCAEP is to assume that the generation of all the BAEP components must be largely restricted to a quite confined region within the auditory nerve and the lower half of the pons.

Animals↗
PubMed1983

Auditory cortical field projections to the basal ganglia of the cat.

Projections to the basal ganglia from four auditory cortical fields in the cat were studied by combining microelectrode-mapping of the neurons' best frequencies with autoradiographic and histochemical tract-tracing techniques. Each auditory field is a source of projections to the homolateral basal ganglia. The distribution of labeling within the basal ganglia is related to the cortical field in which the injection site is located. The dorsal portion of the putamen and adjacent caudate nucleus are connected with cortical fields situated anteriorly and dorsally, while the ventral portion of the putamen and adjacent lateral amygdaloid nucleus are related to auditory fields situated posteriorly and ventrally. Injections of two different tracers into different best-frequency loci of one cortical field provided evidence that low best-frequency neurons project medially within the basal ganglia while high best-frequency neurons project more laterally. We concluded that there was a basic similarity among patterns of terminations in the basal ganglia from axons that originate in different auditory cortical fields. When the source of a projection was confined to a restricted portion of an auditory cortical field, labeling appeared as dense patches of silver grains separated from each other by areas of less dense labeling. Often, these patches were distributed within a sheet of tissue, elongated both dorsoventrally and anteroposteriorly. Loci having the same best-frequency representation, but situated in different auditory cortical fields, project upon overlapping but not coextensive portions of a single sheet of tissue. Thus the projections from geographically distant cortical loci possessing similar best-frequency representations are notably distinguished on a topographic basis. By comparison, two adjacent sheets of tissue were labeled when two injections were made into the low best-frequency and high best-frequency representations of the same auditory field. Double-injection, double-tracer experiments revealed that adjacent sheets of tissue received projections from different best-frequency loci. These observations suggested a degree of tonotopic organization to this projection system which was equipoise to the evidence obtained for a topographic organization.

Animals↗
PubMed1995

Auditory input to the pedunculopontine nucleus: II. Unit responses.

The pedunculopontine nucleus (PPN) has been implicated in sleep-wake control, arousal responses, and motor functions. The PPN also has been implicated in the generation of the P1 middle-latency auditory-evoked potential. The present study was undertaken to determine the nature of the responsiveness of single neurons in and around the PPN following auditory stimulation. Somatosensory responsiveness also was tested in some cells. These results demonstrate a) the presence of a significant proportion of PPN neurons that respond to auditory click stimuli; b) two populations of neurons showing either low threshold/short latency/low habituation or high threshold/longer latency/high habituation; c) the responses of longer latency neurons precede the onset and peak of depth- and vertex-recorded middle-latency auditory-evoked potentials; d) thresholds of longer latency neurons similar to the threshold for wave A in the intact cat, the P13 potential in the intact rat, or the startle reflex; and e) convergent somatosensory and auditory responses at a similar latency in a number of PPN neurons. These findings suggest that neurons in and around the PPN may participate in auditory and somatosensory information processing related to arousal, and may contribute to the manifestation of the P1 auditory middle-latency evoked potential.

Acoustic Stimulation↗
PubMed1991

Auditory image perception and analysis: the basis for hearing.

The premise of this paper is that the auditory system's primary function is its ability to determine the sources of sound. Auditory image perception and analysis are defined as the basis for sound source determination. Few studies in the literature have focused on understanding these abilities and the paper argues that more attention should be paid to auditory image perception and analysis. Four questions are posed for understanding auditory image formation and seven physical variables are described which might be used for auditory image perception. The paper relates auditory image perception and analysis to a number of other topics in the hearing sciences in order to reinforce the argument that auditory image perception and analysis are the basis of hearing.

Acoustic Stimulation↗
PubMed2005

Auditory event related potentials and source current density estimation in phonologic/auditory dyslexics.

OBJECTIVE: To determine the generality of auditory processing impairment in phonologic dyslexics by studying their auditory Event-Related Potentials (ERPs) and the spatio-temporal distribution of their brain activity to auditory linguistic and non-linguistic stimuli with temporal and spectral discriminating cues. METHODS: Fourteen adult phonologic dyslexics and 14 normal reading students, all with high academic achievements, were compared. ERP waveform analysis and current density source estimation (Low resolution Electromagnetic Tomographic Analysis-LORETA) were conducted on 21-channel records from subjects who passively listened or actively discriminated 4 types of auditory stimuli: linguistic and non-linguistic stimuli that differed in spectral or temporal characteristics. RESULTS: Significant differences were found for all ERP latencies (N1, P2, N2, P3) in response to all stimuli, with dyslexics presenting longer latencies compared to normal readers. Current density distributions and their time courses also differed significantly, regardless of stimulus type or attention allocation. Among normal readers, early activity (around N1) was characterized by a rapid change of maximum activity from right to left temporal lobe. Later activity (around P3) was characterized by a stable temporal activity with bilaterally synchronous peak activity. Among the dyslexics, the early N1 activity was stable with left hemisphere prominence, with no alternation between the hemispheres, while the later P3 activity peaked earlier in the right hemisphere than in the left. CONCLUSIONS: Dyslexics were different from controls in processing all auditory stimuli: verbal and non-verbal stimuli with temporal as well as with spectral discriminating cues. The differences mainly consisted of latency and time courses of current density distributions, beginning as early as N1 and extending to the late P3. SIGNIFICANCE: Differences in processing auditory stimuli by phonologic dyslexics are not restricted to linguistic (phonological) stimuli, supporting a general auditory processing impairment in phonologic dyslexia.

Acoustic Stimulation↗
PubMed1999

The role of auditory cortex in retention of rhythmic patterns as studied in patients with temporal lobe removals including Heschl's gyrus.

This experiment examined the participation of the auditory cortex of the temporal lobe in the perception and retention of rhythmic patterns. Four patient groups were tested on a paradigm contrasting reproduction of auditory and visual rhythms: those with right or left anterior temporal lobe removals which included Heschl's gyrus (HG), the region of primary auditory cortex (RT-A and LT-A); and patients with right or left anterior temporal lobe removals which did not include HG (RT-a and LT-a). Estimation of lesion extent in HG using an MRI-based probabilistic map indicated that, in the majority of subjects, the lesion was confined to the anterior secondary auditory cortex located on the anterior-lateral extent of HG. On the rhythm reproduction task, RT-A patients were impaired in retention of auditory but not visual rhythms, particularly when accurate reproduction of stimulus durations was required. In contrast, LT-A patients as well as both RT-a and LT-a patients were relatively unimpaired on this task. None of the patient groups was impaired in the ability to make an adequate motor response. Further, they were unimpaired when using a dichotomous response mode, indicating that they were able to adequately differentiate the stimulus durations and, when given an alternative method of encoding, to retain them. Taken together, these results point to a specific role for the right anterior secondary auditory cortex in the retention of a precise analogue representation of auditory tonal patterns.

Adult↗