Thinking the voice: neural correlates of voice perception

The human voice is the carrier of speech, but also an "auditory face" that conveys important affective and identity information. Little is known about the neural bases of our abilities to perceive such paralinguistic information in voice. Results from recent neuroimaging studies suggest that the different types of vocal information could be processed in partially dissociated functional pathways, and support a neurocognitive model of voice perception largely similar to that proposed for face perception.     

Spatial inattention abolishes voice adaptation

Adaptation to male voices causes a subsequent voice to be perceived as more female, and vice versa. Similar contrastive aftereffects have been reported for phonetic perception, and in vision for face perception. However, while aftereffects in the perception of phonetic features of speech have been reported to persist even when adaptors were processed inattentively, face aftereffects were previously reported to be abolished by inattention to adaptors. Here we demonstrate that auditory aftereffects of adaptation to voice gender are eliminated when the male and female adaptor voices are spatially unattended. Participants simultaneously heard gender-specific male or female adaptor voices in one ear and gender-neutral (androgynous) adaptor voices in the contralateral ear. They selectively attended to the adaptor voices in a designated ear, by either classifying voice gender (Exp. 1) or spoken syllable (Exp. 2). Voice aftereffects were found only if the gender-specific voices were spatially attended, suggesting capacity limits in the processing of voice gender for the unattended ear. Remarkably, gender-specific adaptors in the attended ear elicited comparable aftereffects in test voices, regardless of prior attention to voice gender or phonetic content. Thus, within the attended ear, voice gender was processed even when it was irrelevant for the task at hand, suggesting automatic processing of gender along with linguistic information. Overall, voice gender adaptation requires spatial, but not dimensional, selective attention.     

Neural correlates of perceptual narrowing in cross‐species face‐voice matching

Integrating the multisensory features of talking faces is critical to learning and extracting coherent meaning from social signals. While we know much about the development of these capacities at the behavioral level, we know very little about the underlying neural processes. One prominent behavioral milestone of these capacities is the perceptual narrowing of face–voice matching, whereby young infants match faces and voices across species, but older infants do not. In the present study, we provide neurophysiological evidence for developmental decline in cross‐species face–voice matching. We measured event‐related brain potentials (ERPs) while 4‐ and 8‐month‐old infants watched and listened to congruent and incongruent audio‐visual presentations of monkey vocalizations and humans mimicking monkey vocalizations. The ERP results indicated that younger infants distinguished between the congruent and the incongruent faces and voices regardless of species, whereas in older infants, the sensitivity to multisensory congruency was limited to the human face and voice. Furthermore, with development, visual and frontal brain processes and their functional connectivity became more sensitive to the congruence of human faces and voices relative to monkey faces and voices. Our data show the neural correlates of perceptual narrowing in face–voice matching and support the notion that postnatal experience with species identity is associated with neural changes in multisensory processing ( Lewkowicz & Ghazanfar, 2009 ).     

人声加工的神经机制

人声是人类听觉环境中最熟知和重要的声音, 传递着大量社会相关信息。与视觉人脸加工类似, 大脑对人声也有着特异性加工。研究者使用电生理、脑成像等手段找到了对人声有特异性反应的脑区, 即颞叶人声加工区(TVA), 并发现非人类动物也有类似的特异性加工区域。人声加工主要涉及言语、情绪和身份信息的加工, 分别对应于三条既相互独立又相互作用的神经通路。研究者提出了双通路模型、多阶段模型和整合模型分别对人声的言语、情绪和身份加工进行解释。未来研究需要进一步讨论人声加工的特异性能否由特定声学特征的选择性加工来解释, 并深入探究特殊人群(如自闭症和精神分裂症患者)的人声加工的神经机制。     

Neural correlates for learning to read Roman numerals

This study examined the neuronal correlates of reading Roman numerals and the changes that occur with extensive practice. Subjects were scanned by functional Magnetic Resonance Imaging (fMRI) three times the first day of the experiment and once following two to three months of practice. This allowed comparison of brain activations with varying levels of practice on the same day and across the two to three months of training. The results revealed that upon learning that the alphabetical symbols had numeric meaning subjects immediately activated a network of brain areas, many of which have been previously implicated in numerical processing. Subsequent practice led to a change in the pattern of neuronal activity in only a single region of the mid-dorsolateral prefrontal cortex in the left hemisphere. Implications of these findings are argued with regard to the prevalent neuronal model for the implementation of elementary numerical abilities.     

Neural correlates of consciousness reconsidered

It is widely accepted among philosophers that neuroscientists are conducting a search for the neural correlates of consciousness, or NCC. Chalmers (2000) conceptualized this research program as the attempt to correlate the contents of conscious experience with the contents of representations in specific neural populations. A notable claim on behalf of this interpretation is that the neutral language of "correlates" frees us from philosophical disputes over the mind/body relation, allowing the science to move independently. But the experimental paradigms and explanatory canons of neuroscience are not neutral about the mechanical relation between consciousness and the brain. I argue that NCC research is best characterized as an attempt to locate a causally relevant neural mechanism and not as an effort to identify a discrete neural representation, the content of which correlates with some actual experience. It might be said that the first C in "NCC" should stand for "causes" rather than "correlates."     

Neural correlates of the first-person-perspective

Human self-consciousness depends on the metarepresentation of mental and bodily states as one's own mental and bodily states. First-person-perspective taking is not sufficient, but necessary for human self-consciousness. To assign a first-person-perspective is to center one's own multimodal experiential space upon one's own body, thus operating in an egocentric reference frame. The brain regions involved in assigning first-person-perspective comprise medial prefrontal, medial parietal and lateral temporoparietal cortex. These empirical findings complement recent neurobiologically oriented theories of self-consciousness which focus on the relation between the subject and his/her environment by supplying a neural basis for its key components.     

Neural correlates of metonymy resolution

Metonymies are exemplary models for complex semantic association processes at the sentence level. We investigated processing of metonymies using event-related functional magnetic resonance imaging (fMRI).During an 1.5 Tesla fMRI scan, 14 healthy subjects (12 female) read 124 short German sentences with either literal (like “Africa is arid”), metonymic (“Africa is hungry”), or nonsense (“Africa is woollen”) content. Sentences were constructed so that they obey certain grammatical, semantic, and plausibility conditions and were matched for word frequency, semantic association, length and syntactic structure. We concentrated on metonymies that were not yet fossilised; we also examined a wide variety of metonymic readings.Reading metonymies relative to literal sentences revealed signal changes in a predominantly left-lateralised fronto-temporal network with maxima in the left and right inferior frontal as well as left middle temporal gyri. Left inferior frontal activation may reflect both inference processes and access to world knowledge during metonymy resolution.     

Neural correlates of person recognition

Rapidly identifying known individuals is an essential skill in human society. To elucidate the neural basis of this skill, we monitored brain activity while experimental participants demonstrated their ability to recognize people on the basis of viewing their faces. Each participant first memorized the faces of 20 individuals who were not known to the participants in advance. Each face was presented along with a voice simulating the individual speaking their name and a biographical fact. Following this learning procedure, the associated verbal information could be recalled accurately in response to each face. These learned faces were subsequently viewed together with new faces in a memory task. Subjects made a yes-no recognition decision in response to each face while also covertly retrieving the person-specific information associated with each learned face. Brain activity that accompanied this retrieval of person-specific information was contrasted to that when new faces were processed. Functional magnetic resonance imaging in 10 participants showed that several brain regions were activated during blocks of learned faces, including left hippocampus, left middle temporal gyrus, left insula, and bilateral cerebellum. Recordings of event-related brain potentials in 10 other participants tracked the time course of face processing and showed that learned faces engaged neural activity responsible for person recognition 300-600 msec after face onset. Collectively, these results suggest that the visual input of a recently learned face can rapidly trigger retrieval of associated person-specific information through reactivation of distributed cortical networks linked via hippocampal connections.     

The acoustic bases of human voice identity processing in dogs

Animal Cognition - Speech carries identity-diagnostic acoustic cues that help individuals recognize each other during vocal–social interactions. In humans, fundamental frequency, formant...     

Examinations of identity invariance in facial expression adaptation

Faces provide a wealth of information essential to social interaction, including both static features, such as identity, and dynamic features, such as emotional state. Classic models of face perception propose separate neural-processing routes for identity and facial expression (Bruce & Young, 1986), but more recent models suggest that these routes are not independent of each other (Calder & Young, 2005). Using a perceptual adaptation paradigm in the present study, we attempted to further examine the nature of the relation between the neural representations of identity and emotional expression. In Experiment 1, adaptation to the basic emotions of anger, surprise, disgust, and fear resulted in significantly biased perception away from the adapting expression. A significantly decreased aftereffect was observed when the adapting and the test faces differed in identity. With a statistical model that separated surface texture and reflectance from underlying expression geometry, Experiment 2 showed a similar decrease in adaptation when the face stimuli had identical underlying prototypical geometry but differed in the static surface features supporting identity. These results provide evidence that expression adaptation depends on perceptual features important for identity processing and thus suggest at least partly overlapping neural processing of identity and facial expression.     

Neural correlates of attention to emotional facial expressions in dysphoria

The present study investigated whether dysphoric individuals have a difficulty in disengaging attention from negative stimuli and/or reduced attention to positive information. Sad, neutral and happy facial stimuli were presented in an attention-shifting task to 18 dysphoric and 18 control participants. Reaction times to neutral shapes (squares and diamonds) and the event-related potentials to emotional faces were recorded. Dysphoric individuals did not show impaired attentional disengagement from sad faces or facilitated disengagement from happy faces. Right occipital lateralisation of P100 was absent in dysphoric individuals, possibly indicating reduced attention-related sensory facilitation for faces. Frontal P200 was largest for sad faces among dysphoric individuals, whereas controls showed larger amplitude to both sad and happy as compared with neutral expressions, suggesting that dysphoric individuals deployed early attention to sad, but not happy, expressions. Importantly, the results were obtained controlling for the participants' trait anxiety. We conclude that at least under some circumstances the presence of depressive symptoms can modulate early, automatic stages of emotional processing.     

Neural correlates and causal mechanisms

What Joseph Neisser calls for is exactly right: more philosophy of science will help us better understand and refine the idea of neural correlates of consciousness (NCC). But (i) the key bit of philosophy of science Neisser appeals to is itself in need of clarification; (ii) the orthodox NCC definition is more resourceful than Neisser allows, and (iii) it is possible to resist the phenomenological conception of conscious experience that fuels some of Neisser's argument.     

Neural correlates of spatial term use

The current research used event-related brain potentials (ERPs) to assess the processes underlying online apprehension of the spatial term above. Constituent steps defined within G. D. Logan and D. D. Sadler's (1996) computational theory of apprehension were associated with distinct modulations of ERPs. Specifically, finding the relevant objects was associated with an amplitude modulation of P3; competition in assigning directions to space was associated with modulation of a frontal slow wave; and computing and comparing the spatial relation was associated with modulation of a parietal slow wave. These modulations were differentially influenced by the type of reference frame used to define the spatial term and by the participant's response. The current study supports this decompositional approach to apprehension and provides a means of assessing each step independently.     

Neural correlates of rumination in depression

Rumination, or recursive self-focused thinking, has important implications for understanding the development and maintenance of depressive episodes. Rumination is associated with the worsening of negative mood states, greater affective responding to negative material, and increased access to negative memories. The present study was designed to use fMRI to examine neural aspects of rumination in depressed and healthy control individuals. We used a rumination induction task to assess differences in patterns of neural activation during ruminative self-focus as compared with a concrete distraction condition and with a novel abstract distraction condition in 14 participants who were diagnosed with major depressive disorder and 14 healthy control participants. Depressed participants exhibited increased activation in the orbitofrontal cortex, subgenual anterior cingulate, and dorsolateral prefrontal cortex as compared with healthy controls during rumination versus concrete distraction. Neural activity during rumination versus abstract distraction was greater for depressed than for control participants in the amygdala, rostral anterior cingulate/medial prefrontal cortex, dorsolateral prefrontal cortex, posterior cingulate, and parahippocampus. These findings indicate that ruminative self-focus is associated with enhanced recruitment of limbic and medial and dorsolateral prefrontal regions in depression. Supplemental materials for this article may be downloaded from http://cabn.psychonomic-journals.org/content/supplemental.     

Neural correlates of transformational apparent motion

Transformational apparent motion (TAM) arises when a shape that is abruptly flashed on and off next to a static shape of similar color or texture appears as a protrusion that extends and retracts smoothly from the static object. Here we report that the strength of the TAM percept can be predicted from the waveform of visual evoked potentials (VEPs) measured while observers rated their percepts. The VEPs at pattern onset and offset are maximally symmetric when the static inducer and the flashing patches of the display are of the same contrast. VEP symmetry is affected by how the two patches can be matched as a single surface and may reflect the relative contribution of different motion and object detection systems in visual cortex.     

Neural correlates of arithmetic calculation strategies

Recent research into math cognition has identified areas of the brain that are involved in number processing (Dehaene, Piazza, Pinel, & Cohen, 2003) and complex problem solving (Anderson, 2007). Much of this research assumes that participants use a single strategy; yet, behavioral research finds that people use a variety of strategies (LeFevre et al., 1996; Siegler, 1987; Siegler & Lemaire, 1997). In the present study, we examined cortical activation as a function of two different calculation strategies for mentally solving multidigit multiplication problems. The school strategy, equivalent to long multiplication, involves working from right to left. The expert strategy, used by “lightning” mental calculators (Staszewski, 1988), proceeds from left to right. The two strategies require essentially the same calculations, but have different working memory demands (the school strategy incurs greater demands). The school strategy produced significantly greater early activity in areas involved in attentional aspects of number processing (posterior superior parietal lobule, PSPL) and mental representation (posterior parietal cortex, PPC), but not in a numerical magnitude area (horizontal intraparietal sulcus, HIPS) or a semantic memory retrieval area (lateral inferior prefrontal cortex, LIPFC). An ACT-R model of the task successfully predicted BOLD responses in PPC and LIPFC, as well as in PSPL and HIPS.     

Neural processing of vocal emotion and identity

The voice is a marker of a person's identity which allows individual recognition even if the person is not in sight. Listening to a voice also affords inferences about the speaker's emotional state. Both these types of personal information are encoded in characteristic acoustic feature patterns analyzed within the auditory cortex. In the present study 16 volunteers listened to pairs of non-verbal voice stimuli with happy or sad valence in two different task conditions while event-related brain potentials (ERPs) were recorded. In an emotion matching task, participants indicated whether the expressed emotion of a target voice was congruent or incongruent with that of a (preceding) prime voice. In an identity matching task, participants indicated whether or not the prime and target voice belonged to the same person. Effects based on emotion expressed occurred earlier than those based on voice identity. Specifically, P2 (approximately 200 ms)-amplitudes were reduced for happy voices when primed by happy voices. Identity match effects, by contrast, did not start until around 300 ms. These results show an early task-specific emotion-based influence on the early stages of auditory sensory processing.     

Goal-directedness and personal identity as correlates of life outcomes

Although much research has been conducted on goal setting, researchers have not examined goal-directedness or propensity to set goals as a stable human characteristic in adults. In this study, a survey was developed and distributed to 104 adult participants to assess their goal-directedness, personal identity, and various life outcomes. A theoretical model was developed and tested using structural equation modeling that proposed that both goal-directedness and personal identity should positivcly influence important life outcomes. Analysis showed that goal-directedness and personal identity are positively related to personal well-being, salary, and marital satisfaction. Further, personal identity was positively related to job satisfaction but, contrary to related research, goal-directedness did not predict job satisfaction.     

Neural correlates of acquired color category effects

Category training can induce category effects, whereby color discrimination of stimuli spanning a newly learned category boundary is enhanced relative to equivalently spaced stimuli from within the newly learned category (e.g., categorical perception). However, the underlying mechanisms of these acquired category effects are not fully understood. In the current study, Event-Related Potentials (ERPs) were recorded during a visual oddball task where standard and deviant colored stimuli from the same or different novel categories were presented. ERPs were recorded for a test group who were trained on these novel categories, and for an untrained control group. Category effects were only found for the test group on the trained region of color space, and only occurred during post-perceptual stages of processing. These findings provide new evidence for the involvement of cognitive mechanisms in acquired category effects and suggest that category effects of this kind can exist independent of early perceptual processes.