Middle Superior Temporal Sulcus Research Articles

Phonological repetition-suppression in bilateral superior temporal sulci

Evidence has accumulated that posterior superior temporal sulcus (STS) is critically involved in phonological processing during speech perception, although there are conflicting accounts regarding the degree of lateralization. The current fMRI experiment aimed to identify phonological processing during speech perception through repetition-suppression effects. Repetition-suppression occurs when brain activity decreases from repetitive presentation of stimulus characteristics, in regions of cortex that process those characteristics. We manipulated the degree of phonological repetition among words in short lists to obtain systematic decreases in brain response, indicative of phonological processing. The fMRI experiment presented seventeen participants with recorded wordlists, of low, medium, or high phonological repetition, defined by how many phonemes were shared among words. Bilaterally, middle STS demonstrated activity differences consistent with our prediction of repetition-suppression, as responses decreased systematically with each increase in phonological repetition. Phonological repetition-suppression in bilateral STS converges with neuroimaging evidence for phonological processing, and word deafness resulting from bilateral superior temporal lesions.

Neuronal substrates of gaze following in monkeys

Human and non-human primates follow the gaze of their respective conspecific to identify objects of common interest. Whereas humans rely on eye-gaze for such purposes, monkeys preferentially use head-gaze information. Functional magnetic resonance imaging (fMRI) studies have delineated an area in the human superior temporal sulcus (STS), which is specifically activated when subjects actively follow the eye-gaze of others. Similarly, using fMRI, we have identified an analogous region in the monkey's middle STS responding to gaze following. Hence, although humans and monkeys might rely on different directional cues guiding their attention, they seem to deploy a similar and possibly homologous cortical area to follow the gaze of a conspecific. Our results support the idea that the eyes developed a new social function in human evolution, most likely to support cooperative mutual social interactions building on a phylogenetically old STS module for the processing of head cues.

The correlates of subjective perception of identity and expression in the face network: An fMRI adaptation study

The recognition of facial identity and expression are distinct tasks, with current models hypothesizing anatomic segregation of processing within a face-processing network. Using fMRI adaptation and a region-of-interest approach, we assessed how the perception of identity and expression changes in morphed stimuli affected the signal within this network, by contrasting (a) changes that crossed categorical boundaries of identity or expression with those that did not, and (b) changes that subjects perceived as causing identity or expression to change, versus changes that they perceived as not affecting the category of identity or expression. The occipital face area (OFA) was sensitive to any structural change in a face, whether it was identity or expression, but its signal did not correlate with whether subjects perceived a change or not. Both the fusiform face area (FFA) and the posterior superior temporal sulcus (pSTS) showed release from adaptation when subjects perceived a change in either identity or expression, although in the pSTS this effect only occurred when subjects were explicitly attending to expression. The middle superior temporal sulcus (mSTS) showed release from adaptation for expression only, and the precuneus for identity only. The data support models where the OFA is involved in the early perception of facial structure. However, evidence for a functional overlap in the FFA and pSTS, with both identity and expression signals in both areas, argues against a complete independence of identity and expression processing in these regions of the core face-processing network.

Recognizing people by their voices: An fMRI-study of healthy people and patients after stroke

Theoretical Background: The recognition of a familiar voice is an accomplishment of the human brain that allows us to reliably identify familiar people without seeing them in person. Of note, human voice recognition is a distinct speech process and appears not to be connected to linguistic or semantic language comprehension. Whereas language comprehension and speech functions are regulated by the left hemisphere (Cabeza & Nyberg, 2000), Belin and Zatorre (2003) found a right hemisphere dominance for voice recognition processes. More specifically, the right anterior superior temporal sulcus (STS) and its connections to the prefrontal and medial temporal cortex are involved in the recognition of a familiar voice (von Kriegstein & Giraud, 2004). These findings lead us to the assumption that patients with left hemisphere lesions, and an aphasic syndrome should have no problems in recognizing a familiar voice. Preliminary support comes from a behavioral study by Kneidl (2006), who could demonstrate that the voice recognition performance of aphasic patients with left brain damage is comparable to healthy subjects. Yet to our knowledge, there is still no experimental imaging study on voice recognition processes in aphasic patients with left hemisphere lesions. The aim of the study was twofold. First, we wanted to replicate the finding of a comparable performance of aphasic patients to healthy controls in voice recognition. Second, we wanted to test the assumption of a similar activation in the right STS in aphasic patients compared to healthy control subjects when listening to familiar voices. Method: Subjects were four right-handed patients with left-hemisphere lesions as well as nine right-handed healthy controls matched for age and education. Patients were tested on neuropsycho-logical functions as well as anxiety and depressive symptoms. We used an event-related fMRI-paradigm to measure cerebral activity during identification of familiar and unfamiliar voices. Changes in activity were measured through BOLD-function. Stimuli consisted of 30 mono- and disyllabic words and non-words spoken by one relative of each subject (husband or wife) and four unknown speakers. All stimuli were presented binaurally through earphones in a pseudo-random order. Participants had to respond to a known or unknown voice with a left or right key press using the index or middle finger of the right hand. They received no feedback on the correctness of their response. All stimuli were presented once within a block in random order. Subjects completed four blocks, separated by short rests. Preliminary Results: Error rate was almost three times higher for aphasic patients than for controls (45.9% and 15.4%, U=-2.00, p=.011, two-tailed). There were no differences in omission errors (U=15.5, p=.71) between the two groups. The number of correct responses in the patient group was comparable between words and non-words (Z=.92, p=.36) and familiar and non-familiar-voices (Z=1.10, p=.27). There was an increased activation of the right middle STS (BA 22) for words spoken by a familiar voice compared to an unfamiliar voice. Conclusion: Recognition of a familiar voice involves a network. In contrast to our expectations, aphasic patients showed a decreased ability to recognize a familiar voice.

Cochlear Implant Benefits in Deafness Rehabilitation: PET Study of Temporal Voice Activations

Cochlear implants may improve the medical and social prognosis of profound deafness. Nevertheless, some patients have experienced poor results without any clear explanations. One correlate may be an alteration in cortical voice processing. To test this hypothesis, we studied the activation of human temporal voice areas (TVA) using a well-standardized PET paradigm adapted from previous functional MRI (fMRI) studies. A PET H(2)(15)O activation study was performed on 3 groups of adult volunteers: normal-hearing control subjects (n = 6) and cochlear-implanted postlingually deaf patients with >2 y of cochlear implant experience, with intelligibility scores in the "Lafon monosyllabic task" >80% (GOOD group; n = 6) or <20% (POOR group; n = 6). Relative cerebral blood flow was measured in 3 conditions: rest, passive listening to human voice, and nonvoice stimuli. Compared with silence, the activations induced by nonvoice stimuli were bilaterally located in the superior temporal regions in all groups. However these activations were significantly and similarly reduced in both cochlear implant groups, whereas control subjects showed supplementary activations. Compared with nonvoice, the voice stimuli induced bilateral activation of the TVA along the superior temporal sulcus (STS) in both the control and the GOOD groups. In contrast, these activations were not detected in the POOR group, which showed only left unilateral middle STS activation. These results suggest that PET is an adequate method to explore cochlear implant benefits and that this benefit could be linked to the activation of the TVA.

Spatiotemporal dynamics of audiovisual speech processing

The cortical processing of auditory-alone, visual-alone, and audiovisual speech information is temporally and spatially distributed, and functional magnetic resonance imaging (fMRI) cannot adequately resolve its temporal dynamics. In order to investigate a hypothesized spatiotemporal organization for audiovisual speech processing circuits, event-related potentials (ERPs) were recorded using electroencephalography (EEG). Stimuli were congruent audiovisual /ba/, incongruent auditory /ba/ synchronized with visual /ga/, auditory-only /ba/, and visual-only /ba/ and /ga/. Current density reconstructions (CDRs) of the ERP data were computed across the latency interval of 50–250 ms. The CDRs demonstrated complex spatiotemporal activation patterns that differed across stimulus conditions. The hypothesized circuit that was investigated here comprised initial integration of audiovisual speech by the middle superior temporal sulcus (STS), followed by recruitment of the intraparietal sulcus (IPS), followed by activation of Broca’s area [Miller, L.M., d’Esposito, M., 2005. Perceptual fusion and stimulus coincidence in the cross-modal integration of speech. Journal of Neuroscience 25, 5884–5893]. The importance of spatiotemporally sensitive measures in evaluating processing pathways was demonstrated. Results showed, strikingly, early (< 100 ms) and simultaneous activations in areas of the supramarginal and angular gyrus (SMG/AG), the IPS, the inferior frontal gyrus, and the dorsolateral prefrontal cortex. Also, emergent left hemisphere SMG/AG activation, not predicted based on the unisensory stimulus conditions was observed at approximately 160 to 220 ms. The STS was neither the earliest nor most prominent activation site, although it is frequently considered the sine qua non of audiovisual speech integration. As discussed here, the relatively late activity of the SMG/AG solely under audiovisual conditions is a possible candidate audiovisual speech integration response.

The neural mechanism associated with the processing of onomatopoeic sounds

This event-related fMRI study was conducted to examine the blood-oxygen-level-dependent responses to the processing of auditory onomatopoeic sounds. We used a sound categorization task in which the participants heard four types of stimuli: onomatopoeic sounds, nouns (verbal), animal (nonverbal) sounds, and pure tone/noise (control). By discriminating between the categories of target sounds (birds/nonbirds), the nouns resulted in activations in the left anterior superior temporal gyrus (STG), whereas the animal sounds resulted in activations in the bilateral superior temporal sulcus (STS) and the left inferior frontal gyrus (IFG). In contrast, the onomatopoeias activated extensive brain regions, including the left anterior STG, the region from the bilateral STS to the middle temporal gyrus, and the bilateral IFG. The onomatopoeic sounds showed greater activation in the right middle STS than did the nouns and environmental sounds. These results indicate that onomatopoeic sounds are processed by extensive brain regions involved in the processing of both verbal and nonverbal sounds. Thus, we can posit that onomatopoeic sounds can serve as a bridge between nouns and animal sounds. This is the first evidence to demonstrate the way in which onomatopoeic sounds are processed in the human brain.

The voices of wrath: brain responses to angry prosody in meaningless speech

We report two functional magnetic resonance imaging experiments showing enhanced responses in human middle superior temporal sulcus for angry relative to neutral prosody. This emotional enhancement was voice specific, unrelated to isolated acoustic amplitude or frequency cues in angry prosody, and distinct from any concomitant task-related attentional modulation. Attention and emotion seem to have separate effects on stimulus processing, reflecting a fundamental principle of human brain organization shared by voice and face perception.

Age-dependent plasticity in the superior temporal sulcus in deaf humans: a functional MRI study

BackgroundSign-language comprehension activates the auditory cortex in deaf subjects. It is not known whether this functional plasticity in the temporal cortex is age dependent. We conducted functional magnetic-resonance imaging in six deaf signers who lost their hearing before the age of 2 years, five deaf signers who were >5 years of age at the time of hearing loss and six signers with normal hearing. The task was sentence comprehension in Japanese sign language.ResultsThe sign-comprehension tasks activated the planum temporale of both early- and late-deaf subjects, but not that of hearing signers. In early-deaf subjects, the middle superior temporal sulcus was more prominently activated than in late-deaf subjects.ConclusionsAs the middle superior temporal sulcus is known to respond selectively to human voices, our findings suggest that this subregion of the auditory-association cortex, when deprived of its proper input, might make a functional shift from human voice processing to visual processing in an age-dependent manner.