Evidence of lateralized anteromedial temporal structures involvement in musical emotion processing

The right and left anteromedial temporal lobes have been shown to participate in emotion processing. The aim of the study was to further address their role in music emotion perception/recognition, and assessment by two emotional determinants, i.e., arousal (relaxing versus stimulating aspects) and valence (pleasantness degree). Epileptic patients with right or left anterior mesio-temporal resection (including the amygdala), and control subjects were presented with happy musical (chosen highly stimulating) or sad excerpts (chosen to be relaxing), that were either consonant (pleasant) or dissonant (unpleasant). The patients demonstrated an abnormal perception of dissonant music disregarding of the side of the resection; thereby confirming the role of the parahippocampal gyrus in the perception of unpleasantness. Moreover, the pleasantness of musical excerpts, in particular the happy consonant ones, was overestimated by patients with right temporal damage. In contrast, the arousal rating for happy consonant excerpts was reduced only in the group with left-resections. This modified perception of arousal might be related to the decreased ability of those patients to recognize happy and sad music. Indeed, both right and left temporal resections impaired sadness recognition, whereas happiness recognition was only reduced by the left-resections. The main result was that for the first time, the mesio-temporal structures were demonstrated to be asymmetrically involved in positive musical emotion recognition.     

The neural correlate of speech rhythm as evidenced by metrical speech processing

The present study investigates the neural correlates of rhythm processing in speech perception. German pseudosentences spoken with an exaggerated (isochronous) or a conversational (nonisochronous) rhythm were compared in an auditory functional magnetic resonance imaging experiment. The subjects had to perform either a rhythm task (explicit rhythm processing) or a prosody task (implicit rhythm processing). The study revealed bilateral activation in the supplementary motor area (SMA), extending into the cingulate gyrus, and in the insulae, extending into the right basal ganglia (neostriatum), as well as activity in the right inferior frontal gyrus (IFG) related to the performance of the rhythm task. A direct contrast between isochronous and nonisochronous sentences revealed differences in lateralization of activation for isochronous processing as a function of the explicit and implicit tasks. Explicit processing revealed activation in the right posterior superior temporal gyrus (pSTG), the right supramarginal gyrus, and the right parietal operculum. Implicit processing showed activation in the left supramarginal gyrus, the left pSTG, and the left parietal operculum. The present results indicate a function of the SMA and the insula beyond motor timing and speak for a role of these brain areas in the perception of acoustically temporal intervals. Secondly, the data speak for a specific task-related function of the right IFG in the processing of accent patterns. Finally, the data sustain the assumption that the right secondary auditory cortex is involved in the explicit perception of auditory suprasegmental cues and, moreover, that activity in the right secondary auditory cortex can be modulated by top-down processing mechanisms.     

A functional MRI study of happy and sad affective states induced by classical music

The present study investigated the functional neuroanatomy of transient mood changes in response to Western classical music. In a pilot experiment, 53 healthy volunteers (mean age: 32.0; SD = 9.6) evaluated their emotional responses to 60 classical musical pieces using a visual analogue scale (VAS) ranging from 0 (sad) through 50 (neutral) to 100 (happy). Twenty pieces were found to accurately induce the intended emotional states with good reliability, consisting of 5 happy, 5 sad, and 10 emotionally unevocative, neutral musical pieces. In a subsequent functional magnetic resonance imaging (fMRI) study, the blood oxygenation level dependent (BOLD) signal contrast was measured in response to the mood state induced by each musical stimulus in a separate group of 16 healthy participants (mean age: 29.5; SD = 5.5). Mood state ratings during scanning were made by a VAS, which confirmed the emotional valence of the selected stimuli. Increased BOLD signal contrast during presentation of happy music was found in the ventral and dorsal striatum, anterior cingulate, parahippocampal gyrus, and auditory association areas. With sad music, increased BOLD signal responses were noted in the hippocampus/amygdala and auditory association areas. Presentation of neutral music was associated with increased BOLD signal responses in the insula and auditory association areas. Our findings suggest that an emotion processing network in response to music integrates the ventral and dorsal striatum, areas involved in reward experience and movement; the anterior cingulate, which is important for targeting attention; and medial temporal areas, traditionally found in the appraisal and processing of emotions.     

fMRI evidence for dual routes to the mental lexicon in visual word recognition.

Event-related fMRI was used to investigate lexical decisions to words of high and low frequency of occurrence and to pseudowords. The results obtained strongly support dual-route models of visual word processing. By contrasting words with pseudowords, bilateral occipito-temporal brain areas and posterior left middle temporal gyrus (MTG) were identified as contributing to the successful mapping of orthographic percepts onto visual word form representations. Low-frequency words and pseudowords elicited greater activations than high-frequency words in the superior pars opercularis [Brodmann's area (BA) 44] of the left inferior frontal gyrus (IFG), in the anterior insula, and in the thalamus and caudate nucleus. As processing of these stimuli during lexical search is known to rely on phonological information, it is concluded that these brain regions are involved in grapheme-to-phoneme conversion. Activation in the pars triangularis (BA 45) of the left IFG was observed only for low-frequency words. It is proposed that this region is involved in processes of lexical selection.     

How one's favorite song activates the reward circuitry of the brain: personality matters!

The present fMRI study investigates individual differences in human brain activity during listening to one's favorite and one's most unlikeable song. In 33 participants, we found that the contrast of listening to pleasant versus unpleasant music revealed a robust activation of the ventral striatum, the caudate nucleus and the insula across a group of participants. Moreover, we could demonstrate that activity within the ventral striatum was modulated by the subscale ‘self-forgetfulness’ of the character dimension ‘self-transcendence’.     

Identification of human gustatory cortex by activation likelihood estimation

Over the last two decades, neuroimaging methods have identified a variety of taste-responsive brain regions. Their precise location, however, remains in dispute. For example, taste stimulation activates areas throughout the insula and overlying operculum, but identification of subregions has been inconsistent. Furthermore, literature reviews and summaries of gustatory brain activations tend to reiterate rather than resolve this ambiguity. Here, we used a new meta-analytic method [activation likelihood estimation (ALE)] to obtain a probability map of the location of gustatory brain activation across 15 studies. The map of activation likelihood values can also serve as a source of independent coordinates for future region-of-interest analyses. We observed significant cortical activation probabilities in: bilateral anterior insula and overlying frontal operculum, bilateral mid dorsal insula and overlying Rolandic operculum, and bilateral posterior insula/parietal operculum/postcentral gyrus, left lateral orbitofrontal cortex (OFC), right medial OFC, pregenual anterior cingulate cortex (prACC) and right mediodorsal thalamus. This analysis confirms the involvement of multiple cortical areas within insula and overlying operculum in gustatory processing and provides a functional "taste map" which can be used as an inclusive mask in the data analyses of future studies. In light of this new analysis, we discuss human central processing of gustatory stimuli and identify topics where increased research effort is warranted.     

Do brain responses to emotional images and cigarette cues differ? An fMRI study in smokers

Chronic smoking is thought to cause changes in brain reward systems that result in overvaluation of cigarette-related stimuli and undervaluation of natural rewards. We tested the hypotheses that, in smokers, brain circuits involved in emotional processing: (i) would be more active during exposure to cigarette-related than neutral pictures; and (ii) would be less active to pleasant compared with cigarette-related pictures, suggesting a devaluation of intrinsically pleasant stimuli. We obtained whole-brain blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging data from 35 smokers during the presentation of pleasant (erotica and romance), unpleasant (mutilations and sad), neutral, and cigarette-related pictures. Whole-brain analyses showed significantly larger BOLD responses during presentation of cigarette-related pictures relative to neutral ones within the secondary visual areas, the cingulate gyrus, the frontal gyrus, the dorsal striatum, and the left insula. BOLD responses to erotic pictures exceeded responses to cigarette-related pictures in all clusters except the insula. Within the left insula we observed larger BOLD responses to cigarette-related pictures than to all other picture categories. By including intrinsically pleasant and unpleasant pictures in addition to neutral ones, we were able to conclude that the presentation of cigarette-related pictures activates brain areas supporting emotional processes, but we did not find evidence of overall reduced activation of the brain reward systems in the presence of intrinsically pleasant stimuli.     

Bilateral Rolandic operculum processing underlying heartbeat awareness reflects changes in bodily self‐consciousness

Exteroceptive bodily signals (including tactile, proprioceptive and visual signals) are important information contributing to self‐consciousness. Moreover, prominent theories proposed that visceral signals about internal bodily states are equally or even more important for self‐consciousness. Neuroimaging studies have described several brain regions which process signals related to bodily self‐consciousness (BSC) based on the integration of exteroceptive signals (e.g. premotor cortex, angular gyrus, supramarginal gyrus and extrastriate body area), and that another brain region, the insula/operculum which is involved in interoception and interoceptive awareness, processes signals critical for self‐awareness. Providing evidence for the integration of exteroceptive and interoceptive bodily signals, recent behavioral experiments have demonstrated that the manipulation of interoceptive (e.g. cardiac) signals, coupled with exteroceptive (e.g. visual) signals, also modulates BSC. Does this integration occur within or outside the structures described above? To this end, we adapted a recently designed protocol that uses cardio‐visual stimulation to induce altered states of BSC to fMRI. Additionally, we measured neural activity in a classical interoceptive task. We found six brain regions (bilateral Rolandic operculum, bilateral supramarginal gyrus, right frontal inferior operculum and left temporal superior gyrus) that were activated differently during the interoception task as opposed to a control task. The brain regions which showed the highest selectivity for BSC based on our cardio‐visual manipulation were found in the bilateral Rolandic operculum. Given our findings, we propose that the Rolandic operculum processes integrated exteroceptive–interoceptive signals that are necessary for interoceptive awareness as well as BSC.     

Habituation of attentional networks during emotion processing

Dysfunctional emotion processing is a key aspect of many neuropsychiatric disorders. This dysfunction may be due to an abnormal magnitude of neural substrate activation during emotion processing or due to an altered time course of the neural substrate response. To better understand the temporal characteristics of the neural substrate activation underlying implicit emotion processing, nine healthy female controls were repeatedly exposed to pictures of affective faces while performing a gender identification task in an fMRI. As the salience of the stimuli decreased with repeated exposure, brain areas implicated in a right hemispheric spatial attention network (including the posterior parietal cortex (BA 40) and the frontal eye fields (BA 6)) habituated while brain areas lateralized to the left hemisphere (including the angular gyrus (BA 39), posterior superior temporal gyrus (BA 39) and insula (BA 13)) sensitized. These results provide strong evidence that the time course of activation is a critical component when assessing the function of neural substrates underlying emotion processing (specifically whether habituation is altered) in neuro-psychiatric patients.     

Facial expressions: what the mirror neuron system can and cannot tell us

Facial expressions contain both motor and emotional components. The inferior frontal gyrus (IFG) and posterior parietal cortex have been considered to compose a mirror neuron system (MNS) for the motor components of facial expressions, while the amygdala and insula may represent an "additional" MNS for emotional states. Together, these systems may contribute to our understanding of facial expressions. Here we further examine this possibility. In three separate event-related fMRI experiment, subjects had to (1) observe (2) discriminate and (3) imitate facial expressions. Stimuli were dynamic neutral, happy, fearful and disgusted facial expressions, and in Experiments 1 and 2, an additional pattern motion condition. Importantly, during each experiment, subjects were unaware of the nature of the next experiments. Results demonstrate that even passive viewing of facial expressions activates a wide network of brain regions that were also involved in the execution of similar expressions, including the IFG/insula and the posterior parietal cortex. Only a subset of these regions responded more during the observation of facial than pattern motion (bilateral ventral IFG, bilateral STS/MTG, bilateral amygdala, SMA). While the viewing of facial expressions recruited similar brain regions in all three experiments, adding an active task (discrimination, imitation) augmented the magnitude of these activations. Brain activations reflected differences in observed facial expressions, with emotional expressions activating relatively more the insula/frontal operculum, and neutral ones (blowing up the cheeks) the somatosensory cortices (SII). Using movies, fear activated the amygdala and disgust the insula, but other emotions activated these structures to a similar degree.     

Tagging cortical networks in emotion: A topographical analysis

Viewing emotional pictures is associated with heightened perception and attention, indexed by a relative increase in visual cortical activity. Visual cortical modulation by emotion is hypothesized to reflect re‐entrant connectivity originating in higher‐order cortical and/or limbic structures. The present study used dense‐array electroencephalography and individual brain anatomy to investigate functional coupling between the visual cortex and other cortical areas during affective picture viewing. Participants viewed pleasant, neutral, and unpleasant pictures that flickered at a rate of 10 Hz to evoke steady‐state visual evoked potentials (ssVEPs) in the EEG. The spectral power of ssVEPs was quantified using Fourier transform, and cortical sources were estimated using beamformer spatial filters based on individual structural magnetic resonance images. In addition to lower‐tier visual cortex, a network of occipito‐temporal and parietal (bilateral precuneus, inferior parietal lobules) structures showed enhanced ssVEP power when participants viewed emotional (either pleasant or unpleasant), compared to neutral pictures. Functional coupling during emotional processing was enhanced between the bilateral occipital poles and a network of temporal (left middle/inferior temporal gyrus), parietal (bilateral parietal lobules), and frontal (left middle/inferior frontal gyrus) structures. These results converge with findings from hemodynamic analyses of emotional picture viewing and suggest that viewing emotionally engaging stimuli is associated with the formation of functional links between visual cortex and the cortical regions underlying attention modulation and preparation for action. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.     

The emotional power of music: how music enhances the feeling of affective pictures

Music is an intriguing stimulus widely used in movies to increase the emotional experience. However, no brain imaging study has to date examined this enhancement effect using emotional pictures (the modality mostly used in emotion research) and musical excerpts. Therefore, we designed this functional magnetic resonance imaging study to explore how musical stimuli enhance the feeling of affective pictures. In a classical block design carefully controlling for habituation and order effects, we presented fearful and sad pictures (mostly taken from the IAPS) either alone or combined with congruent emotional musical excerpts (classical pieces). Subjective ratings clearly indicated that the emotional experience was markedly increased in the combined relative to the picture condition. Furthermore, using a second-level analysis and regions of interest approach, we observed a clear functional and structural dissociation between the combined and the picture condition. Besides increased activation in brain areas known to be involved in auditory as well as in neutral and emotional visual-auditory integration processes, the combined condition showed increased activation in many structures known to be involved in emotion processing (including for example amygdala, hippocampus, parahippocampus, insula, striatum, medial ventral frontal cortex, cerebellum, fusiform gyrus). In contrast, the picture condition only showed an activation increase in the cognitive part of the prefrontal cortex, mainly in the right dorsolateral prefrontal cortex. Based on these findings, we suggest that emotional pictures evoke a more cognitive mode of emotion perception, whereas congruent presentations of emotional visual and musical stimuli rather automatically evoke strong emotional feelings and experiences.     

Are left fronto-temporal brain areas a prerequisite for normal music-syntactic processing?

An increasing number of neuroimaging studies in music cognition research suggest that “language areas” are involved in the processing of musical syntax, but none of these studies clarified whether these areas are a prerequisite for normal syntax processing in music. The present electrophysiological experiment tested whether patients with lesions in Broca’s area (N = 6) or in the left anterior temporal lobe (N = 7) exhibit deficits in the processing of structure in music compared to matched healthy controls (N = 13). A chord sequence paradigm was applied, and the amplitude and scalp topography of the Early Right Anterior Negativity (ERAN) was examined, an electrophysiological marker of musical syntax processing that correlates with activity in Broca’s area and its right hemisphere homotope. Left inferior frontal gyrus (IFG) (but not anterior superior temporal gyrus – aSTG) patients with lesions older than 4 years showed an ERAN with abnormal scalp distribution, and subtle behavioural deficits in detecting music-syntactic irregularities. In one IFG patient tested 7 months post-stroke, the ERAN was extinguished and the behavioural performance remained at chance level. These combined results suggest that the left IFG, known to be crucial for syntax processing in language, plays also a functional role in the processing of musical syntax. Hence, the present findings are consistent with the notion that Broca’s area supports the processing of syntax in a rather domain-general way.     

Words in melody: an H(2)15O PET study of brain activation during singing and speaking

We used H(2)15O PET to characterize the interaction of words and melody by comparing brain activity measured while subjects spoke or sang the words to a familiar song. Relative increases in activity during speaking vs singing were observed in the left hemisphere, in classical perisylvian language areas including the posterior superior temporal gyrus, supramarginal gyrus, and frontal operculum, as well as in Rolandic cortices and putamen. Relative increases in activity during singing were observed in the right hemisphere: these were maximal in the right anterior superior temporal gyrus and contiguous portions of the insula; relative increases associated with singing were also detected in the right anterior middle temporal gyrus and superior temporal sulcus, medial and dorsolateral prefrontal cortices, mesial temporal cortices and cerebellum, as well as in Rolandic cortices and nucleus accumbens. These results indicate that the production of words in song is associated with activation of regions within right hemisphere areas that are not mirror-image homologues of left hemisphere perisylvian language areas, and suggest that multiple neural networks may be involved in different aspects of singing. Right hemisphere mechanisms may support the fluency-evoking effects of singing in neurological disorders such as stuttering or aphasia.     

Music and language side by side in the brain: a PET study of the generation of melodies and sentences

Parallel generational tasks for music and language were compared using positron emission tomography. Amateur musicians vocally improvised melodic or linguistic phrases in response to unfamiliar, auditorily presented melodies or phrases. Core areas for generating melodic phrases appeared to be in left Brodmann area (BA) 45, right BA 44, bilateral temporal planum polare, lateral BA 6, and pre-SMA. Core areas for generating sentences seemed to be in bilateral posterior superior and middle temporal cortex (BA 22, 21), left BA 39, bilateral superior frontal (BA 8, 9), left inferior frontal (BA 44, 45), anterior cingulate, and pre-SMA. Direct comparisons of the two tasks revealed activations in nearly identical functional brain areas, including the primary motor cortex, supplementary motor area, Broca's area, anterior insula, primary and secondary auditory cortices, temporal pole, basal ganglia, ventral thalamus, and posterior cerebellum. Most of the differences between melodic and sentential generation were seen in lateralization tendencies, with the language task favouring the left hemisphere. However, many of the activations for each modality were bilateral, and so there was significant overlap. While clarification of this overlapping activity awaits higher-resolution measurements and interventional assessments, plausible accounts for it include component sharing, interleaved representations, and adaptive coding. With these and related findings, we outline a comparative model of shared, parallel, and distinctive features of the neural systems supporting music and language. The model assumes that music and language show parallel combinatoric generativity for complex sound structures (phonology) but distinctly different informational content (semantics).     

Distinctive neural signatures for negative sentences in Hindi: an fMRI study

We examined cortical activations using functional magnetic resonance imaging (fMRI) technique in skilled native Hindi readers while they performed a ‘target-probe’ semantic judgment task on affirmative and negative sentences. Hindi, an Indo-Aryan language widely spoken in India, follows subject-object-verb (SOV) order canonically but allows free word order. The common cortical regions involved in affirmative and negative sentence conditions included bilateral inferior frontal gyrus (IFG), left parietal cortex (BA 7/40), left fusiform (BA 37), bilateral supplementary motor area (SMA) (BA 6), bilateral middle temporal gyrus (BA 21), and bilateral occipital area (BA 17/18). While no distinct region was activated for affirmative sentences, we observed activations in the region of bilateral anterior temporal pole for negative sentence. The behavioral results showed no significant mean difference for reaction times (RT) and accuracy measures between affirmative and negative sentences. However, the imaging results suggest the recruitment of anterior temporal pole in processing of negative sentences. Region of interest (ROI) analysis for selected regions showed higher signal intensity for negative sentences possibly indicating the associated inherent difficulty level of processing, especially when integrating information related to negations.     

Stuttered and fluent speech production: an ALE meta-analysis of functional neuroimaging studies

This study reports an activation likelihood estimation (ALE) meta-analysis of imaging studies of chronic developmental stuttering in adults. Two parallel meta-analyses were carried out: (1) stuttered production in the stutterers; (2) fluent production in the control subjects. The control subjects' data replicated previous analyses of single-word reading, identifying activation in primary motor cortex, premotor cortex, supplementary motor area, Rolandic operculum, lateral cerebellum, and auditory areas, among others. The stuttering subjects' analysis showed that similar brain areas are involved in stuttered speech as in fluent speech, but with some important differences. Motor areas were over-activated in stuttering, including primary motor cortex, supplementary motor area, cingulate motor area, and cerebellar vermis. Frontal operculum, Rolandic operculum, and anterior insula showed anomalous right-laterality in stutterers. Auditory activations, due to hearing one's own speech, were essentially undetectable in stutterers. The phenomenon of efference copy is proposed as a unifying account of the pattern activation revealed within this ALE meta-analysis. This provides the basis for a stuttering system model that is testable and should help to advance the understanding and treatment of this disorder.     

Expecting unpleasant stimuli – An fMRI study

Expecting forthcoming events and preparing adequate responses are important cognitive functions that help the individual to deal with the environment. The emotional valence of an event is decisive for the resulting action. Revealing the underlying mechanisms may help to understand the dysfunctional information processing in depression and anxiety that are associated with negative expectation of the future. We were interested in selective brain activity during the expectation of unpleasant visual stimuli. Twelve healthy female subjects were biased to expect and then perceive emotionally unpleasant, pleasant or neutral stimuli during functional magnetic resonance imaging. Expecting unpleasant stimuli relative to expecting pleasant and neutral stimuli resulted in activation of mainly cingulate cortex, insula, prefrontal areas, thalamus, hypothalamus and striatum. While certain areas were also active during subsequent presentation of the emotional stimuli, distinct regions of the anterior cingulate gyrus and the thalamus were solely active during expectation of the unpleasant stimuli. The identified areas may reflect a network for internal adaptation and preparation processes in order to react adequately to expected unpleasant events. They are known as well to be altered in depression. Disorders of this network may be relevant for psychiatric disorders such as depression.     

Spatial and temporal analysis of fMRI data on word and sentence reading

Written language comprehension at the word and the sentence level was analysed by the combination of spatial and temporal analysis of functional magnetic resonance imaging (fMRI). Spatial analysis was performed via general linear modelling (GLM). Concerning the temporal analysis, local differences in neurovascular coupling may confound a direct comparison of blood oxygenation level-dependent (BOLD) response estimates between regions. To avoid this problem, we parametrically varied linguistic task demands and compared only task-induced within-region BOLD response differences across areas. We reasoned that, in a hierarchical processing system, increasing task demands at lower processing levels induce delayed onset of higher-level processes in corresponding areas. The flow of activation is thus reflected in the size of task-induced delay increases. We estimated BOLD response delay and duration for each voxel and each participant by fitting a model function to the event-related average BOLD response. The GLM showed increasing activations with increasing linguistic demands dominantly in the left inferior frontal gyrus (IFG) and the left superior temporal gyrus (STG). The combination of spatial and temporal analysis allowed a functional differentiation of IFG subregions involved in written language comprehension. Ventral IFG region (BA 47) and STG subserve earlier processing stages than two dorsal IFG regions (BA 44 and 45). This is in accordance with the assumed early lexical semantic and late syntactic processing of these regions and illustrates the complementary information provided by spatial and temporal fMRI data analysis of the same data set.     

Expecting unpleasant stimuli--an fMRI study

Expecting forthcoming events and preparing adequate responses are important cognitive functions that help the individual to deal with the environment. The emotional valence of an event is decisive for the resulting action. Revealing the underlying mechanisms may help to understand the dysfunctional information processing in depression and anxiety that are associated with negative expectation of the future. We were interested in selective brain activity during the expectation of unpleasant visual stimuli. Twelve healthy female subjects were biased to expect and then perceive emotionally unpleasant, pleasant or neutral stimuli during functional magnetic resonance imaging. Expecting unpleasant stimuli relative to expecting pleasant and neutral stimuli resulted in activation of mainly cingulate cortex, insula, prefrontal areas, thalamus, hypothalamus and striatum. While certain areas were also active during subsequent presentation of the emotional stimuli, distinct regions of the anterior cingulate gyrus and the thalamus were solely active during expectation of the unpleasant stimuli. The identified areas may reflect a network for internal adaptation and preparation processes in order to react adequately to expected unpleasant events. They are known as well to be altered in depression. Disorders of this network may be relevant for psychiatric disorders such as depression.