Left Anterior Superior Temporal Sulcus Research Articles

Cortical thickness and surface area of left anterior temporal areas affects processing of phonological cues to morphosyntax

Lack of methods to experimentally assess the perceptual processing of sound features and allow one to measure differences in phonological proficiency has been a limitation for speech processing studies in native speakers. Tonal features associated with Swedish word-stems, word accents, which cue grammatical suffixes, constitute, however, such sound features that can be exploited to generate measures of reliance on morphosyntactically relevant phonological information during word processing. Specifically, there is a natural variance between native speakers in response time (RT) difference between phonologically valid and invalid word accent-suffix combinations that can be used to quantify perceptual phonological proficiency. This study uses ultra-high field magnetic resonance imaging (MRI) to investigate word accents as phonological cues to morphosyntactic meaning. The study adds to the understanding of the neural basis for both morphosyntactically relevant phonological cues by reporting correlations between differences in listeners’ RT for validly and invalidly cued suffixes and cortical thickness in left anterior and middle temporal gyrus, and the left anterior superior temporal sulcus as well as cortical surface area in the left middle and inferior temporal gyri. The cortical areas studied are known constituents of the ventral speech processing stream, necessary for word and phrase recognition.

Coin, telephone, and handcuffs: Neural correlates of social knowledge of inanimate objects

A variety of objects are made to serve social functions. The use of these objects has greatly enriched and expanded our social behaviors. How do our brains represent the social knowledge of inanimate objects such as coins, telephones, and handcuffs? According to a recent version of the grounded theory, social knowledge of inanimate objects might be grounded in the mentalizing network, as the social functions of inanimate objects are closely associated with the intentions of the people using them. However, there is also evidence that the mentalizing network may only get activated when a human/mental agent is detected. Using fMRI, we explored the neural correlates of social knowledge of inanimate objects by comparing the brain activation evoked by high-sociality object nouns (e.g., banknote) with that evoked by low-sociality object nouns (e.g., battery). The left anterior superior temporal sulcus, a classic part of the mentalizing network, showed higher activation for the high-sociality inanimate object nouns than for the low-sociality ones in the whole-brain analysis. Several other areas of the mentalizing network showed sensitivity to object sociality in small volume correction and/or region-of-interest analyses. Our findings indicate that social knowledge of inanimate objects is supported by brain areas in the mentalizing network.

Close yet independent: Dissociation of social from valence and abstract semantic dimensions in the left anterior temporal lobe.

The anterior temporal lobe (ATL) is engaged in various types of semantic dimensions. One consistently reported dimension is social information, with abstract words describing social behaviors inducing stronger activations in the ATL than nonsocial words. One potential factor that has been systematically confounded in this finding is emotional valence, given that abstract social words tend to be associated with emotional feelings. We investigated which factors drove the ATL sensitivity using a 2 (social/nonsocial) × 2 (valenced/neutral) factorial design in an fMRI study with relatively high spatial resolutions. We found that sociality and valence were processed in different ATL regions without significant interactions: The social effect was found in the left anterior superior temporal sulcus (aSTS), whereas the valence effect activated small clusters in the bilateral temporal poles (TP). In the left ATL, the social- and valence-related clusters were distinct from another superior ATL area that exhibited a general "abstractness" effect with little modulation of sociality or valence. These subregions exhibited distinct whole-brain functional connectivity patterns during the resting state, with the social cluster functionally connected to the default mode network, the valence cluster connected to the adjacent temporal regions and amygdala, and the abstractness cluster connected to a distributed network including a set of language-related regions. These results of activation profiles and connectivity patterns together indicate that the way in which the left ATL supports semantic processing is highly fine-grained, with the neural substrate for social semantic effects dissociated from those for emotional valence and abstractness.

Neuroanatomical correlates of forgiving unintentional harms

Mature moral judgments rely on the consideration of a perpetrator’s mental state as well as harmfulness of the outcomes produced. Prior work has focused primarily on the functional correlates of how intent information is neurally represented for moral judgments, but few studies have investigated whether individual differences in neuroanatomy can also explain variation in moral judgments. In the current study, we conducted voxel-based morphometry analyses to address this question. We found that local grey matter volume in the left anterior superior temporal sulcus, a region in the functionally defined theory of mind or mentalizing network, was associated with the degree to which participants relied on information about innocent intentions to forgive accidental harms. Our findings provide further support for the key role of mentalizing in the forgiveness of accidental harms and contribute preliminary evidence for the neuroanatomical basis of individual differences in moral judgments.

Person-Based Versus Generalized Impulsivity Disinhibition in Frontotemporal Dementia and Alzheimer Disease.

While much disinhibition in dementia results from generalized impulsivity, in behavioral variant frontotemporal dementia (bvFTD) disinhibition may also result from impaired social cognition. To deconstruct disinhibition and its neural correlates in bvFTD vs. early-onset Alzheimer's disease (eAD). Caregivers of 16 bvFTD and 21 matched-eAD patients completed the Frontal Systems Behavior Scale disinhibition items. The disinhibition items were further categorized into (1) "person-based" subscale which predominantly associated with violating social propriety and personal boundary and (2) "generalized-impulsivity" subscale which included nonspecific impulsive acts. Subscale scores were correlated with grey matter volumes from tensor-based morphometry on magnetic resonance images. In comparison to the eAD patients, the bvFTD patients developed greater person-based disinhibition ( P < 0.001) but comparable generalized impulsivity. Severity of person-based disinhibition significantly correlated with the left anterior superior temporal sulcus (STS), and generalized-impulsivity correlated with the right orbitofrontal cortex (OFC) and the left anterior temporal lobe (aTL). Person-based disinhibition was predominant in bvFTD and correlated with the left STS. In both dementia, violations of social propriety and personal boundaries involved fronto-parieto-temporal network of Theory of Mind, whereas nonspecific disinhibition involved the OFC and aTL.

Semantic retrieval during overt picture description: Left anterior temporal or the parietal lobe?

Retrieval of semantic representations is a central process during overt speech production. There is an increasing consensus that an amodal semantic ‘hub’ must exist that draws together modality-specific representations of concepts. Based on the distribution of atrophy and the behavioral deficit of patients with the semantic variant of fronto-temporal lobar degeneration, it has been proposed that this hub is localized within both anterior temporal lobes (ATL), and is functionally connected with verbal ‘output’ systems via the left ATL. An alternative view, dating from Geschwind's proposal in 1965, is that the angular gyrus (AG) is central to object-based semantic representations. In this fMRI study we examined the connectivity of the left ATL and parietal lobe (PL) with whole brain networks known to be activated during overt picture description. We decomposed each of these two brain volumes into 15 regions of interest (ROIs), using independent component analysis. A dual regression analysis was used to establish the connectivity of each ROI with whole brain-networks. An ROI within the left anterior superior temporal sulcus (antSTS) was functionally connected to other parts of the left ATL, including anterior ventromedial left temporal cortex (partially attenuated by signal loss due to susceptibility artifact), a large left dorsolateral prefrontal region (including ‘classic’ Broca's area), extensive bilateral sensory-motor cortices, and the length of both superior temporal gyri. The time-course of this functionally connected network was associated with picture description but not with non-semantic baseline tasks. This system has the distribution expected for the production of overt speech with appropriate semantic content, and the auditory monitoring of the overt speech output. In contrast, the only left PL ROI that showed connectivity with brain systems most strongly activated by the picture-description task, was in the superior parietal lobe (supPL). This region showed connectivity with predominantly posterior cortical regions required for the visual processing of the pictorial stimuli, with additional connectivity to the dorsal left AG and a small component of the left inferior frontal gyrus. None of the other PL ROIs that included part of the left AG were activated by Speech alone. The best interpretation of these results is that the left antSTS connects the proposed semantic hub (specifically localized to ventral anterior temporal cortex based on clinical neuropsychological studies) to posterior frontal regions and sensory-motor cortices responsible for the overt production of speech.

Implicit false-belief processing in the human brain

Eye-movement patterns in ‘Sally–Anne’ tasks reflect humans' ability to implicitly process the mental states of others, particularly false-beliefs — a key theory of mind (ToM) operation. It has recently been proposed that an efficient ToM system, which operates in the absence of awareness (implicit ToM, iToM), subserves the analysis of belief-like states. This contrasts to consciously available belief processing, performed by the explicit ToM system (eToM). The frontal, temporal and parietal cortices are engaged when humans explicitly ‘mentalize’ about others' beliefs. However, the neural underpinnings of implicit false-belief processing and the extent to which they draw on networks involved in explicit general-belief processing are unknown. Here, participants watched ‘Sally–Anne’ movies while fMRI and eye-tracking measures were acquired simultaneously. Participants displayed eye-movements consistent with implicit false-belief processing. After independently localizing the brain areas involved in explicit general-belief processing, only the left anterior superior temporal sulcus and precuneus revealed greater blood-oxygen-level-dependent activity for false- relative to true-belief trials in our iToM paradigm. No such difference was found for the right temporal–parietal junction despite significant activity in this area. These findings fractionate brain regions that are associated with explicit general ToM reasoning and false-belief processing in the absence of awareness.

The Pathways for Intelligible Speech: Multivariate and Univariate Perspectives

An anterior pathway, concerned with extracting meaning from sound, has been identified in nonhuman primates. An analogous pathway has been suggested in humans, but controversy exists concerning the degree of lateralization and the precise location where responses to intelligible speech emerge. We have demonstrated that the left anterior superior temporal sulcus (STS) responds preferentially to intelligible speech (Scott SK, Blank CC, Rosen S, Wise RJS. 2000. Identification of a pathway for intelligible speech in the left temporal lobe. Brain. 123:2400–2406.). A functional magnetic resonance imaging study in Cerebral Cortex used equivalent stimuli and univariate and multivariate analyses to argue for the greater importance of bilateral posterior when compared with the left anterior STS in responding to intelligible speech (Okada K, Rong F, Venezia J, Matchin W, Hsieh IH, Saberi K, Serences JT,Hickok G. 2010. Hierarchical organization of human auditory cortex: evidence from acoustic invariance in the response to intelligible speech. 20: 2486–2495.). Here, we also replicate our original study, demonstrating that the left anterior STS exhibits the strongest univariate response and, in decoding using the bilateral temporal cortex, contains the most informative voxels showing an increased response to intelligible speech. In contrast, in classifications using local “searchlights” and a whole brain analysis, we find greater classification accuracy in posterior rather than anterior temporal regions. Thus, we show that the precise nature of the multivariate analysis used will emphasize different response profiles associated with complex sound to speech processing.

A Head View-Invariant Representation of Gaze Direction in Anterior Superior Temporal Sulcus

SummaryHumans show a remarkable ability to discriminate others' gaze direction, even though a given direction can be conveyed by many physically dissimilar configurations of different eye positions and head views. For example, eye contact can be signaled by a rightward glance in a left-turned head or by direct gaze in a front-facing head. Such acute gaze discrimination implies considerable perceptual invariance. Previous human research found that superior temporal sulcus (STS) responds preferentially to gaze shifts [1], but the underlying representation that supports such general responsiveness remains poorly understood. Using multivariate pattern analysis (MVPA) of human functional magnetic resonance imaging (fMRI) data, we tested whether STS contains a higher-order, head view-invariant code for gaze direction. The results revealed a finely graded gaze direction code in right anterior STS that was invariant to head view and physical image features. Further analyses revealed similar gaze effects in left anterior STS and precuneus. Our results suggest that anterior STS codes the direction of another's attention regardless of how this information is conveyed and demonstrate how high-level face areas carry out fine-grained, perceptually relevant discrimination through invariance to other face features.

Cortical processing of head- and eye-gaze cues guiding joint social attention

Previous fMRI experiments showed an involvement of the STS in the processing of eye-gaze direction in joint attention. Since head-gaze direction can also be used for the assessment of another person's attentional focus, we compared the mechanisms underlying the processing of head- and eye-gaze direction using a combined psychophysical and fMRI approach. Subjects actively followed the head- or eye-gaze direction of a person in a photograph towards one of seven possible targets by moving their eyes. We showed that the right posterior superior temporal sulcus (STS) as well as the right fusiform gyrus (FSG) were involved in both processing of head- as well as eye-gaze direction. Another finding was a bilateral deactivation of a distinct area in the middle STS (mSTS) as well as the left anterior STS (aSTS), that was stronger when subjects followed eye-gaze direction than when they followed head-gaze direction. We assume that this deactivation is based on an active suppression of information arising from the distracting other directional cue, i.e. head-gaze direction in the eye-gaze direction task and eye-gaze direction in the head-gaze direction task.These results further support the hypothesis that the human equivalent of the gaze sensitive area in monkeys lies in more anterior parts of the STS than previously thought.

A Multisensory Cortical Network for Understanding Speech in Noise

In noisy environments, listeners tend to hear a speaker's voice yet struggle to understand what is said. The most effective way to improve intelligibility in such conditions is to watch the speaker's mouth movements. Here we identify the neural networks that distinguish understanding from merely hearing speech, and determine how the brain applies visual information to improve intelligibility. Using functional magnetic resonance imaging, we show that understanding speech-in-noise is supported by a network of brain areas including the left superior parietal lobule, the motor/premotor cortex, and the left anterior superior temporal sulcus (STS), a likely apex of the acoustic processing hierarchy. Multisensory integration likely improves comprehension through improved communication between the left temporal-occipital boundary, the left medial-temporal lobe, and the left STS. This demonstrates how the brain uses information from multiple modalities to improve speech comprehension in naturalistic, acoustically adverse conditions.

Individual differences in the theory of mind and superior temporal sulcus

We investigated the brain area with regard to individual differences in the theory of mind. Using functional magnetic resonance imaging, we examined the brain area in which signal intensity was apparently related to performance of a theory-of-mind task on multiple regression analysis. A significant relation was observed between performance of theory-of-mind task and activation in the left anterior superior temporal sulcus. We could not find such an activation in the superior temporal sulcus and the temporo-parietal junction area. The present findings provide new evidence that the anterior superior temporal sulcus might dictate individual differences in theory of mind.

Neural correlates of intelligibility in speech investigated with noise vocoded speech—A positron emission tomography study

Functional imaging studies of speech perception in the human brain have identified a key role for auditory association areas in the temporal lobes (bilateral superior temporal gyri and sulci) in the perceptual processing of the speech signal. This is extended to suggest some functional specialization within this bilateral system, with a particular role for the left anterior superior temporal sulcus (STS) in processing intelligible speech. In the current study, noise-vocoded speech was used to vary the intelligibility of speech parametrically. This replicated the finding of a selective response to intelligibility in speech in the left anterior superior temporal sulcus, in contrast to the posterior superior temporal sulcus, which showed a response profile insensitive to the degree of intelligibility. These results are related to theories of functional organization in the human auditory system, which have indicated that there are separate processing streams, with different functional roles, running anterior and posterior to primary auditory cortex. Specifically, it is suggested that an anterior stream processing intelligibility can be distinguished from a posterior stream associated with transient representations, important in spoken repetition and working memory.

Syntactic and Semantic Modulation of Neural Activity during Auditory Sentence Comprehension

In previous functional neuroimaging studies, left anterior temporal and temporal-parietal areas responded more strongly to sentences than to randomly ordered lists of words. The smaller response for word lists could be explained by either (1) less activation of syntactic processes due to the absence of syntactic structure in the random word lists or (2) less activation of semantic processes resulting from failure to combine the content words into a global meaning. To test these two explanations, we conducted a functional magnetic resonance imaging study in which word order and combinatorial word meaning were independently manipulated during auditory comprehension. Subjects heard six different stimuli: normal sentences, semantically incongruent sentences in which content words were randomly replaced with other content words, pseudoword sentences, and versions of these three sentence types in which word order was randomized to remove syntactic structure. Effects of syntactic structure (greater activation to sentences than to word lists) were observed in the left anterior superior temporal sulcus and left angular gyrus. Semantic effects (greater activation to semantically congruent stimuli than either incongruent or pseudoword stimuli) were seen in widespread, bilateral temporal lobe areas and the angular gyrus. Of the two regions that responded to syntactic structure, the angular gyrus showed a greater response to semantic structure, suggesting that reduced activation for word lists in this area is related to a disruption in semantic processing. The anterior temporal lobe, on the other hand, was relatively insensitive to manipulations of semantic structure, suggesting that syntactic information plays a greater role in driving activation in this area.

Neural Substrates of Phonemic Perception

The temporal lobe in the left hemisphere has long been implicated in the perception of speech sounds. Little is known, however, regarding the specific function of different temporal regions in the analysis of the speech signal. Here we show that an area extending along the left middle and anterior superior temporal sulcus (STS) is more responsive to familiar consonant-vowel syllables during an auditory discrimination task than to comparably complex auditory patterns that cannot be associated with learned phonemic categories. In contrast, areas in the dorsal superior temporal gyrus bilaterally, closer to primary auditory cortex, are activated to the same extent by the phonemic and nonphonemic sounds. Thus, the left middle/anterior STS appears to play a role in phonemic perception. It may represent an intermediate stage of processing in a functional pathway linking areas in the bilateral dorsal superior temporal gyrus, presumably involved in the analysis of physical features of speech and other complex non-speech sounds, to areas in the left anterior STS and middle temporal gyrus that are engaged in higher-level linguistic processes.

Distinct unimodal and multimodal regions for word processing in the left temporal cortex

How are word recognition circuits organized in the left temporal lobe? We used functional magnetic resonance imaging (fMRI) to dissect cortical word-processing circuits using three diagnostic criteria: the capacity of an area (1) to respond to words in a single modality (visual or auditory) or in both modalities, (2) to modulate its response in a top-down manner as a function of the graphemic or phonemic emphasis of the task, and (3) to show repetition suppression in response to the conscious repetition of the target word within the same sensory modality or across different modalities. The results clarify the organization of visual and auditory word-processing streams. In particular, the visual word form area (VWFA) in the left occipitotemporal sulcus appears strictly as a visual unimodal area. It is, however, bordered by a second lateral inferotemporal area which is multimodal [lateral inferotemporal multimodal area (LIMA)]. Both areas might have been confounded in past work. Our results also suggest a possible homolog of the VWFA in the auditory stream, the auditory word form area, located in the left anterior superior temporal sulcus.

Residual naming after damage to the left temporal pole: a PET activation study

Normal subjects activate the left temporal polar cortex when they name persons, and subjects with damage to the left temporal pole due to left anterior temporal lobectomy are impaired in the retrieval of the proper names of persons. Eight such subjects were studied in a PET activation experiment to address the neural systems supporting their residual naming. We hypothesized that there would be increased activity, relative to normal controls, in the surround of the damaged region, the homologous right temporal pole, or both. Neither the group nor individual target subjects showed significantly increased activity in the lesion surround or in the right temporal pole. Several other regions that are activated by normals during the retrieval of the proper names of persons and which were undamaged in the target subjects (left anterior superior temporal sulcus, mesial frontal cortex, and anterior cingulate) were nevertheless significantly less activated by the target subjects, a finding that suggests that damage to the left temporal pole alters the function of a large-scale system needed for the retrieval of proper nouns. There was increased activity in early visual cortices, suggesting intensification of visual processing to compensate for the defective preferred name retrieval processing.

The response of left temporal cortex to sentences.

The meaning of a sentence differs from the sum of the meanings of its constituents. Left anterior temporal cortex responds to sentences more strongly than to unconnected words. We hypothesized that the anterior temporal response to sentences is due to this difference in meaning (compositional semantics). Using positron emission tomography (PET), we studied four experimental conditions (2 x 2 factorial design): In one condition, subjects read normal sentences. In a second condition, they read grammatically correct sentences containing numerous semantic violations (semantically random sentences). In a third condition, we scrambled the word order within the normal sentences, and, in a fourth condition, the word order was scrambled within the semantically random sentences. The left anterior temporal pole responded strongly to sentences compared to scrambled versions of sentences. A similar although weaker response occurred in the left anterior superior temporal sulcus and the left posterior middle temporal gyrus. A subset of voxels within the left anterior temporal pole responded more to semantically random sentences and their scrambled versions than to normal sentences and the corresponding scrambled versions (main effect of semantic randomness). Finally, the grammatical and the semantic factor interacted in a subset of voxels within the anterior temporal pole: Activity was higher when subjects read normal sentences compared to their scrambled versions but not for semantically random sentences compared to their corresponding scrambled versions. The effects of grammar and meaning and, most importantly, the interaction between grammatical and semantic factors are compatible with the hypothesis that the left anterior temporal pole contributes to the composition of sentence meaning.