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Selective deficit of auditory localisation in patients with visuospatial neglect.

Possible auditory deficits in neglect were examined by comparing the performance of four right brain-damaged (RBD) patients with left visuospatial neglect, versus four RBD patients without neglect, in three auditory tasks. The first task required speeded discrimination of sound elevation, by moving a central lever up or down according to the vertical position of a peripheral target sound, regardless of its side. The other two auditory tasks were non-spatial, requiring either speeded pitch discrimination (moving the central lever up for high pitch, down for low pitch) or speeded target detection. Neglect patients' performance was impaired with respect to RBD controls only when the auditory task required spatial coding of the target sound (the up/down spatial discrimination). This demonstrates a selective deficit of auditory space perception in neglect patients. This auditory spatial deficit was more pronounced for left than right sounds. Since auditory space perception was impaired in the vertical dimension, the observed deficit cannot be attributed to a systematic rightward shift in sound localisation. Instead, the results suggest increased spatial uncertainty in sound localisation by neglect patients, particularly for auditory targets on the contralesional side. These findings are related to multimodal coding of space in the parietal cortex, which was damaged in the neglect patients, but not in the RBD controls.

Adult↗

Impaired processing of prosodic and musical patterns after right hemisphere damage.

The distinction between the processing of musical information and segmental speech information (i.e., consonants and vowels) has been much explored. In contrast, the relationship between the processing of music and prosodic speech information (e.g., intonation) has been largely ignored. We report an assessment of prosodic perception for an amateur musician, KB, who became amusic following a right-hemisphere stroke. Relative to matched controls, KB's segmental speech perception was preserved. However, KB was unable to discriminate pitch or rhythm patterns in linguistic or musical stimuli. He was also impaired on prosodic perception tasks (e.g., discriminating statements from questions). Results are discussed in terms of common neural mechanisms that may underlie the processing of some aspects of both music and speech prosody.

Aged↗

The effect of musicianship on pitch memory in performance matched groups.

We compared brain activation patterns between musicians and non-musicians (matched in performance score) while they performed a pitch memory task (using a sparse temporal sampling fMRI method). Both groups showed bilateral activation of the superior temporal, supramarginal, posterior middle and inferior frontal gyrus, and superior parietal lobe. Musicians showed more right temporal and supramarginal gyrus activation while non-musicians had more right primary and left secondary auditory cortex activation. Since both groups' performance were matched, these results probably indicate processing differences between groups that are possibly related to musical training. Non-musicians rely more on brain regions important for pitch discrimination while musicians prefer to use brain regions specialized in short-term memory and recall to perform well in this pitch memory task.

Acoustic Stimulation↗

Neural characteristics of successful and less successful speech and word learning in adults.

A remarkable characteristic of the human nervous system is its ability to learn to integrate novel (foreign) complex sounds into words. However, the neural changes involved in how adults learn to integrate novel sounds into words and the associated individual differences are largely unknown. Unlike English, most languages of the world use pitch patterns to mark individual word meaning. We report a study assessing the neural correlates of learning to use these pitch patterns in words by English-speaking adults who had no previous exposure to such usage. Before and after training, subjects discriminated pitch patterns of the words they learned while blood oxygenation levels were measured using fMRI. Subjects who mastered the learning program showed increased activation in the left posterior superior temporal region after training, while subjects who plateaued at lower levels showed increased activation in the right superior temporal region and right inferior frontal gyrus, which are associated with nonlinguistic pitch processing, and prefrontal and medial frontal areas, which are associated with increased working memory and attentional efforts. Furthermore, we found brain activation differences even before training between the two subject groups, including the superior temporal region. These results demonstrate an association between range of neural changes and degrees of language learning, specifically implicating the physiologic contribution of the left dorsal auditory cortex in learning success.

Acoustic Stimulation↗

Word and tone working memory deficits in schizophrenia.

BACKGROUND: Verbal memory deficits have been reported in many studies of patients with schizophrenia. We evaluated the specificity of these deficits by comparing patients and control subjects on several verbal and nonverbal auditory memory tests. METHODS: Performance of stable, medicated outpatients with DSM-III-R diagnoses of schizophrenia (N = 38) was compared with that of healthy subjects (N = 39) on a word list immediate recall task, tone delayed discrimination tasks, and word and tone serial position tasks. Before memory testing, patients were divided into 2 groups based on their ability to perform normally on a screening test requiring pitch discrimination and sustained attention. RESULTS: The nonverbal tests were more difficult for control subjects than the verbal tests. Despite this, patients who performed normally on the screening test of perception and attention performed normally on both nonverbal tests but had highly significant deficits on both verbal tests (P<.001 and P = .02). Patients who performed poorly on the screening test had highly significant performance deficits on all the memory tests. CONCLUSIONS: One subgroup of patients with schizophrenia has a selective deficit in verbal memory despite normal motivation, attention, and general perceptual function. Another group has deficits in multiple aspects of cognitive function suggestive of failure in early stages of information processing.

Adult↗

Neuroelectric correlates of hemispheric asymmetry: spectral discrimination and stimulus competition.

In an effort to explore further the role of the right hemisphere in auditory processing, this study utilized brain event-related potentials (ERPs) to investigate hemispheric asymmetry for the processing of complex spectral tones. Subjects participated in two pitch discrimination tasks, one diotic, the other dichotic. ERP components were recorded from 28 electrodes on the scalp and analyzed via individual/group average area measurements. Results showed that ERPs recorded in response to the dichotic target pairs exhibited a larger P3 area when the target tone was presented to the left ear, while the N1 area showed no significant difference. ERPs recorded in the diotic condition showed a larger P3 area and smaller N1 area compared to the dichotic conditions. Finally, all experimental tasks showed that topographic hemispheric activation patterns were asymmetric to the right hemisphere. Findings support the notion that ERP topographic asymmetries may be dependent on specific cognitive task demands (e.g., diotic vs. dichotic modes of presentation). In addition, the data suggest that the P3 component may better reflect interaural advantages for complex tones than the N1 component and may, therefore, be a more sensitive indicator of hemispheric specialization.

Adult↗

Time estimation in schizophrenia: an fMRI study at adjusted levels of difficulty.

fMRI was performed in nine male schizophrenia patients and 15 healthy male controls during an auditory time estimation (timing), a frequency (i.e. pitch) discrimination task, and rest. An adaptive psychophysical approach, the weighted up-down method, was used to adjust individual performance to a level of 75% probability for correct answers. Although performing on the same level of individual difficulty, schizophrenia patients revealed less activations in prefrontal cortex and caudate nucleus, comparing time vs rest. Timing specific differences (i.e. timing vs pitch) between patients and controls were found in the posterior putamen, anterior thalamus, and right medial prefrontal cortex, with patients showing relative hypoactivity. Impairment in time estimation in schizophrenia might be mediated by specific fronto-thalamo-striatal dysfunction.

Adult↗

Effects of language experience and stimulus complexity on the categorical perception of pitch direction.

Whether or not categorical perception results from the operation of a special, language-specific, speech mode remains controversial. In this cross-language (Mandarin Chinese, English) study of the categorical nature of tone perception, we compared native Mandarin and English speakers' perception of a physical continuum of fundamental frequency contours ranging from a level to rising tone in both Mandarin speech and a homologous (nonspeech) harmonic tone. This design permits us to evaluate the effect of language experience by comparing Chinese and English groups; to determine whether categorical perception is speech-specific or domain-general by comparing speech to nonspeech stimuli for both groups; and to examine whether categorical perception involves a separate categorical process, distinct from regions of sensory discontinuity, by comparing speech to nonspeech stimuli for English listeners. Results show evidence of strong categorical perception of speech stimuli for Chinese but not English listeners. Categorical perception of nonspeech stimuli was comparable to that for speech stimuli for Chinese but weaker for English listeners, and perception of nonspeech stimuli was more categorical for English listeners than was perception of speech stimuli. These findings lead us to adopt a memory-based, multistore model of perception in which categorization is domain-general but influenced by long-term categorical representations.

Acoustic Stimulation↗

Muscle tension patterns during auditory attention.

Although there is much evidence demonstrating muscle tension changes during mental work, there are few data concerning muscle tension patterns during effortful attention to simple sensory stimuli. In the present study, sensory attention was evoked by a pitch discrimination task at three levels of difficulty, with a digit retention task administered for comparison. Twenty-four females each performed both tasks at all levels of difficulty, while the EKG, and the corrugator supercilii, frontalis, lip, jaw, chin, and forearm area EMG were recorded. As expected, heart rate decreased significantly with increasing difficulty of the pitch task. A pattern of facial EMG responses accompanied the pitch task, which included significant increases in corrugator and frontalis, and decreases in the jaw as a function of difficulty, and time within trials. The tension pattern observed during sensory intake is discussed in terms of its relation to emotional expressions and motor theories of attention.

Acoustic Stimulation↗

Pitch memory, labelling and disembedding in autism.

BACKGROUND: Autistic musical savants invariably possess absolute pitch ability and are able to disembed individual musical tones from chords. Enhanced pitch discrimination and memory has been found in non-savant individuals with autism who also show superior performance on visual disembedding tasks. These experiments investigate the extent that enhanced disembedding ability will be found within the musical domain in autism. METHOD: High-functioning children with autism, together with age- and intelligence-matched controls, participated in three experiments testing pitch memory, labelling and chord disembedding. RESULTS: The findings from experiment 1 showed enhanced pitch memory and labelling in the autism group. In experiment 2, when subjects were pre-exposed to labelled individual tones, superior chord segmentation was also found. However, in experiment 3, when disembedding performance was less reliant on pitch memory, no group differences emerged and the children with autism, like controls, perceived musical chords holistically. CONCLUSION: These findings indicate that pitch memory and labelling is superior in autism and can facilitate performance on musical disembedding tasks. However, when task performance does not rely on long-term pitch memory, autistic children, like controls, succumb to the Gestalt qualities of chords.

Adolescent↗

Some relationships between intelligence and auditory discrimination.

Some of the earliest scientific attempts to understand the nature of intelligence investigated differences in sensory discrimination and reaction time. There is once again interest in the relations between such simple abilities and intelligence, partly as a result of the application of information-processing paradigms to the study of intelligence. Correlations in the range of .3 to .8 have been reported between psychometric measures of intelligence and performance on simple cognitive, sensory, and motor tasks. The current study reports correlations between scores on a battery of auditory discrimination tasks and measures of intelligence and academic aptitude in two samples of college students. The correlations between the intellectual and academic aptitude measures and the total percent correct on the auditory battery ranged from 45 to 59. These results are consistent with recent findings of significant relationships between simple sensory, cognitive, and motor abilities and psychometric intelligence as well as with much earlier reports by Spearman (1904) and others of relationships between pitch discrimination and intelligence. An implication of these findings is that intelligence is a potential confounding variable in studies of the auditory perceptual abilities of various clinical populations.

Auditory Perception↗

Vibrotactile frequency discrimination at short durations.

This experiment investigated how frequency discrimination of a sinusoidal, mechanical vibration applied to the tip of the right index finger is affected by shortening the duration of the stimuli from 200 ms to 30 ms. Using a standard stimulus of 100 Hz at 30 dB above threshold, seven comparison frequencies (at intervals of 10 Hz) were judged as higher or lower in frequency according to the method of constant differences. Vibrotactile stimuli were matched for subjective intensity across both frequency and duration. Difference limens for vibrotactile frequency were found to decline slightly from 200 ms to 50 ms (attributable to practice) and to increase noticeably at 30 ms. This result is discussed in relation to the seemingly contradictory results for auditory pitch discrimination.

Adult↗

Electrical stimulation of the superior olivary complex can produce cortical evoked potential and behavioral discrimination correlates of pitch perception in the rat.

Patterned electrical stimulation of the superior olivary complex (SOC) which simulated the neural frequency following response (FFR) extracellular potential was used as a stimulus in behavioral frequency discrimination and cortical evoked potential studies. Behavioral judgments of SOC stimulation frequency were found to be as accurate as those obtained for 80 dB acoustic stimuli within the spectral band of the FFR (200 to 3800 Hz). Cortical evoked potentials elicited by acoustic and electrical stimulation of the SOC were then compared for preservation of waveform similarity. Frequency dependent similarity was observed in slow wave events elicited by stimuli with frequencies in the FFR band. A 3 msec time lag was found between acoustic and SOC stimulation produced waveforms which can be accounted for by forward stimulation of the auditory pathway. Our study supports the idea that integrated extracellular waveforms of the FFR index low frequency representations in the auditory brainstem, perhaps by selecting patches of SOC cell transmembrane potential changes. Because bilateral cochlear damage did not prevent behavioral discrimination of SOC electrical stimulation, feedback to the ear is not necessary for perceptual significance of simulated FFR extracellular field potentials in the SOC.

Acoustic Stimulation↗

Auditory temporal processing impairment: neither necessary nor sufficient for causing language impairment in children.

Fourteen twin pairs, aged 8 to 10 years, were tested 3 times over 12 months; they included 11 children with language impairment (LI), 11 control children matched on nonverbal ability and age, and 6 co-twins who did not meet criteria for LI or control status. Thresholds were estimated for detecting a brief backward-masked tone (BM), detection of frequency modulation (FM), and pitch discrimination using temporal cues (deltaf0). Both BM and FM thresholds improved with training, and by the 2nd test session, FM thresholds were in the adult range. There were marked individual differences on BM and deltaf0 and, for both tasks, performance correlated with Tallal's Auditory Repetition Task administered 2 years previously. However, no auditory measure gave significant differences between LI and control groups; performance was influenced more by nonverbal than language ability. Some children did have a stable pattern of poor performance on certain auditory tasks, but their good FM detection raised questions about whether processing of auditory temporal information is abnormal. We found no evidence that auditory deficits are a necessary or sufficient cause of language impairments.

Adult↗

Tone-versus FM--induced patterns of excitation and suppression in the 14-C-2-deoxyglucose labeled auditory "cortex" of the guinea fowl.

The primary auditory "cortex" field L, of the Guinea fowl is a three layer tonotopically organized structure. Isofrequency planes as shown with the 2-deoxyglucose (2DG) method cut across these layers and with their second dimension extend in rostro-caudal direction. The input layer L2 exhibits "spontaneous" labeling due to high spontaneous activity of input terminals and units throughout the hearing range. The labeling is stronger locally along a rostro-caudal isofrequency contour of L2 after tone or narrow band FM stimulation. With tone stimuli the layers L1 and L3 are labeled within an isofrequency plane except for the rostral half of the field whereas frequency modulated tones do label these two layers throughout the corresponding isofrequency plane. FM stimuli in addition lead to a reduction of spontaneous labeling in frequency planes adjacent to those which are covered by the stimuli. Since these effects correlate with known inhibitory effects of such stimuli it is argued that the 2 DG method can identify the suppression of activity of neurons in suitable structures.

Animals↗

Calculating psychoacoustic parameters of amplitude modulated narrow noise bands.

A simple model is suggested enabling the comprehensive calculation of pschoacoustic parameters (absolute modulation thresholds, modulation difference limens, and the subjective magnitude of supraliminal modulation differences) for amplitude modulated narrow noise bands. A comparison of experimental and model data reveals good agreement.

Adult↗

Estimates of human cochlear tuning at low levels using forward and simultaneous masking.

Auditory filter shapes were derived from psychophysical measurements in eight normal-hearing listeners using a variant of the notched-noise method for brief signals in forward and simultaneous masking. Signal frequencies of 1, 2, 4, 6, and 8 kHz were tested. The signal level was fixed at 10 dB above absolute threshold in the forward-masking conditions and fixed at either 10 or 35 dB above absolute threshold in the simultaneous-masking conditions. The results show that filter equivalent rectangular bandwidths (ERBs) are substantially narrower in forward masking than has been found in previous studies using simultaneous masking. Furthermore, in contrast to earlier studies, the sharpness of tuning doubles over the range of frequencies tested, giving Q(ERB) values of about 10 and 20 at signal frequencies of 1 and 8 kHz, respectively. It is argued that the new estimates of auditory filter bandwidth provide a more accurate estimate of human cochlear tuning at low levels than earlier estimates using simultaneous masking at higher levels, and that they are therefore more suitable for comparison to cochlear tuning data from other species. The data may also prove helpful in defining the parameters for nonlinear models of human cochlear processing.

Acoustic Stimulation↗

Right frontotemporal activation by tonal memory in dyslexia, an O15 PET Study.

A prior study documented the failure of dyslexic men to activate left temporoparietal cortex during phonologic processing. Because of reports of an anomalous right planum temporale in developmental dyslexia, the functional implications of which are unknown, this study examined the ability of dyslexics to activate right temporal cortex. Regional cerebral blood flow was measured in 15 right-handed dyslexic men during rest and during a tonal memory task expected to activate right-sided cortex in controls. A matched control sample (n = 18) showed significant activation of several right frontotemporal regions as well as of left temporal cortex. In contrast, severely dyslexic men activated fewer right frontotemporal regions, while making many more errors than controls, but showed normal activation of left mid to anterior temporal cortex. These results support hypothesized underlying deficits in rapid temporal processing and possible involvement of right (in addition to left) temporal cortex in severe dyslexia.

Adult↗