Marcus Herdener

The effect of appraisal level on processing of emotional prosody in meaningless speech

In visual perception of emotional stimuli, low- and high-level appraisal processes have been found to engage different neural structures. Beyond emotional facial expression, emotional prosody is an important auditory cue for social interaction. Neuroimaging studies have proposed a network for emotional prosody processing that involves a right temporal input region and explicit evaluation in bilateral prefrontal areas. However, the comparison of different appraisal levels has so far relied upon using linguistic instructions during low-level processing, which might confound effects of processing level and linguistic task. In order to circumvent this problem, we examined processing of emotional prosody in meaningless speech during gender labelling (implicit, low-level appraisal) and emotion labelling (explicit, high-level appraisal). While bilateral amygdala, left superior temporal sulcus and right parietal areas showed stronger blood oxygen level-dependent (BOLD) responses during implicit processing, areas with stronger BOLD responses during explicit processing included the left inferior frontal gyrus, bilateral parietal, anterior cingulate and supplemental motor cortex. Emotional versus neutral prosody evoked BOLD responses in right superior temporal gyrus, bilateral anterior cingulate, left inferior frontal gyrus, insula and bilateral putamen. Basal ganglia and right anterior cingulate responses to emotional versus neutral prosody were particularly pronounced during explicit processing. These results are in line with an amygdala-prefrontal-cingulate network controlling different appraisal levels, and suggest a specific role of the left inferior frontal gyrus in explicit evaluation of emotional prosody. In addition to brain areas commonly related to prosody processing, our results suggest specific functions of anterior cingulate and basal ganglia in detecting emotional prosody, particularly when explicit identification is necessary.

Enhancing BOLD response in the auditory system by neurophysiologically tuned fMRI sequence

Auditory neuroscience has not tapped fMRIs full potential because of acoustic scanner noise emitted by the gradient switches of conventional echoplanar fMRI sequences. The scanner noise is pulsed, and auditory cortex is particularly sensitive to pulsed sounds. Current fMRI approaches to avoid stimulus-noise interactions are temporally inefficient. Since the sustained BOLD response to pulsed sounds decreases with repetition rate and becomes minimal with unpulsed sounds, we developed an fMRI sequence emitting continuous rather than pulsed gradient sound by implementing a novel quasi-continuous gradient switch pattern. Compared to conventional fMRI, continuous-sound fMRI reduced auditory cortex BOLD baseline and increased BOLD amplitude with graded sound stimuli, short sound events, and sounds as complex as orchestra music with preserved temporal resolution. Response in subcortical auditory nuclei was enhanced, but not the response to light in visual cortex. Finally, tonotopic mapping using continuous-sound fMRI demonstrates that enhanced functional signal-to-noise in BOLD response translates into improved spatial separability of specific sound representations.

Differential patterns of multisensory interactions in core and belt areas of human auditory cortex

The auditory cortex is anatomically segregated into a central core and a peripheral belt region, which exhibit differences in preference to bandpassed noise and in temporal patterns of response to acoustic stimuli. While it has been shown that visual stimuli can modify response magnitude in auditory cortex, little is known about differential patterns of multisensory interactions in core and belt. Here, we used functional magnetic resonance imaging and examined the influence of a short visual stimulus presented prior to acoustic stimulation on the spatial pattern of blood oxygen level-dependent signal response in auditory cortex. Consistent with crossmodal inhibition, the light produced a suppression of signal response in a cortical region corresponding to the core. In the surrounding areas corresponding to the belt regions, however, we found an inverse modulation with an increasing signal in centrifugal direction. Our data suggest that crossmodal effects are differentially modulated according to the hierarchical core-belt organization of auditory cortex.

Functional changes of the reward system underlie blunted response to social gaze in cocaine users

Significance Social interaction deficits in drug users likely impede treatment, increase the burden of the affected families, and consequently contribute to the high costs for society associated with addiction. However, the neural origin contributing to altered social interaction in drug users is unknown thus far. The present study illuminates the nature of basic social interaction deficits as exemplified by social gaze behavior in cocaine users by applying behavioral, psychophysiological, and functional brain-imaging methods. The results suggest that basal social interaction impairments probably arise from blunted social reward processing that was again related to impaired real-life social behavior in cocaine users. These results point to the importance of reinstatement of social reward in the treatment of stimulant addiction. Social interaction deficits in drug users likely impede treatment, increase the burden of the affected families, and consequently contribute to the high costs for society associated with addiction. Despite its significance, the neural basis of altered social interaction in drug users is currently unknown. Therefore, we investigated basal social gaze behavior in cocaine users by applying behavioral, psychophysiological, and functional brain-imaging methods. In study I, 80 regular cocaine users and 63 healthy controls completed an interactive paradigm in which the participants’ gaze was recorded by an eye-tracking device that controlled the gaze of an anthropomorphic virtual character. Valence ratings of different eye-contact conditions revealed that cocaine users show diminished emotional engagement in social interaction, which was also supported by reduced pupil responses. Study II investigated the neural underpinnings of changes in social reward processing observed in study I. Sixteen cocaine users and 16 controls completed a similar interaction paradigm as used in study I while undergoing functional magnetic resonance imaging. In response to social interaction, cocaine users displayed decreased activation of the medial orbitofrontal cortex, a key region of reward processing. Moreover, blunted activation of the medial orbitofrontal cortex was significantly correlated with a decreased social network size, reflecting problems in real-life social behavior because of reduced social reward. In conclusion, basic social interaction deficits in cocaine users as observed here may arise from altered social reward processing. Consequently, these results point to the importance of reinstatement of social reward in the treatment of stimulant addiction.

Altered lateralisation of emotional prosody processing in schizophrenia

Alterations of cerebral lateralisation in schizophrenia have been reported consistently, and a reduced left-lateralisation has been suggested for language functions. Speech contains non-verbal information, e.g. prosody, and on a behavioural level, the extraction of emotional information from prosody is often impaired in schizophrenia. A previous functional magnetic resonance imaging study suggests increased left-lateralisation in schizophrenia during prosody processing, but did not disentangle effects of speech processing as such and emotional prosody processing. Here, we used meaningless syllables spoken with neutral, angry or fearful speech melody and measured blood oxygen level-dependent (BOLD) responses in 15 in-patients with schizophrenia and 15 healthy control participants matched for age and gender. Lateralisation indices were calculated for responses to emotional versus neutral prosody, and for all types of prosody versus baseline. Compared to control participants, patients with schizophrenia showed an increased right-lateralisation of emotional and non-emotional prosody processing in the temporal and parietal cortex. This right-lateralisation was increased in patients with reduced right-handedness and decreased in patients with stronger negative symptoms, particularly affective blunting, and with longer hospitalisation. Although patients with schizophrenia performed worse in emotion identification, this deficit was not related to lateralisation indices. Enhanced right-lateralisation to prosody resembles previous findings on laterality changes in speech processing and might suggest a common underlying cause in the organization of language functions.

Jazz Drummers Recruit Language-Specific Areas for the Processing of Rhythmic Structure

Rhythm is a central characteristic of music and speech, the most important domains of human communication using acoustic signals. Here, we investigated how rhythmical patterns in music are processed in the human brain, and, in addition, evaluated the impact of musical training on rhythm processing. Using fMRI, we found that deviations from a rule-based regular rhythmic structure activated the left planum temporale together with Brocas area and its right-hemispheric homolog across subjects, that is, a network also crucially involved in the processing of harmonic structure in music and the syntactic analysis of language. Comparing the BOLD responses to rhythmic variations between professional jazz drummers and musical laypersons, we found that only highly trained rhythmic experts show additional activity in left-hemispheric supramarginal gyrus, a higher-order region involved in processing of linguistic syntax. This suggests an additional functional recruitment of brain areas usually dedicated to complex linguistic syntax processing for the analysis of rhythmical patterns only in professional jazz drummers, who are especially trained to use rhythmical cues for communication.

Spatial representations of temporal and spectral sound cues in human auditory cortex

Natural and behaviorally relevant sounds are characterized by temporal modulations of their waveforms, which carry important cues for sound segmentation and communication. Still, there is little consensus as to how this temporal information is represented in auditory cortex. Here, by using functional magnetic resonance imaging (fMRI) optimized for studying the auditory system, we report the existence of a topographically ordered spatial representation of temporal sound modulation rates in human auditory cortex. We found a topographically organized sensitivity within auditory cortex to sounds with varying modulation rates, with enhanced responses to lower modulation rates (2 and 4 Hz) on lateral parts of Heschls gyrus (HG) and faster modulation rates (16 and 32 Hz) on medial HG. The representation of temporal modulation rates was distinct from the representation of sound frequencies (tonotopy) that was orientated roughly orthogonal. Moreover, the combination of probabilistic anatomical maps with a previously proposed functional delineation of auditory fields revealed that the distinct maps of temporal and spectral sound features both prevail within two presumed primary auditory fields hA1 and hR. Our results reveal a topographically ordered representation of temporal sound cues in human primary auditory cortex that is complementary to maps of spectral cues. They thereby enhance our understanding of the functional parcellation and organization of auditory cortical processing.

BOLD correlates of edge detection in human auditory cortex

Edges are important cues defining coherent auditory objects. As a model of auditory edges, sound on- and offset are particularly suitable to study their neural underpinnings because they contrast a specific physical input against no physical input. Change from silence to sound, that is onset, has extensively been studied and elicits transient neural responses bilaterally in auditory cortex. However, neural activity associated with sound onset is not only related to edge detection but also to novel afferent inputs. Edges at the change from sound to silence, that is offset, are not confounded by novel physical input and thus allow to examine neural activity associated with sound edges per se. In the first experiment, we used silent acquisition functional magnetic resonance imaging and found that the offset of pulsed sound activates planum temporale, superior temporal sulcus and planum polare of the right hemisphere. In the planum temporale and the superior temporal sulcus, offset response amplitudes were related to the pulse repetition rate of the preceding stimulation. In the second experiment, we found that these offset-responsive regions were also activated by single sound pulses, onset of sound pulse sequences and single sound pulse omissions within sound pulse sequences. However, they were not active during sustained sound presentation. Thus, our data show that circumscribed areas in right temporal cortex are specifically involved in identifying auditory edges. This operation is crucial for translating acoustic signal time series into coherent auditory objects.

Clinical potential of methylphenidate in the treatment of cocaine addiction: a review of the current evidence

Background Cocaine use continues to be a public health problem, yet there is no proven effective pharmacotherapy for cocaine dependence. A promising approach to treating cocaine dependence may be agonist-replacement therapy, which is already used effectively in the treatment of opioid and tobacco dependence. The replacement approach for cocaine dependence posits that administration of a long-acting stimulant medication should normalize the neurochemical and behavioral perturbations resulting from chronic cocaine use. One potential medication to be substituted for cocaine is methylphenidate (MPH), as this stimulant possesses pharmacobehavioral properties similar to those of cocaine. Aim To provide a qualitative review addressing the rationale for the use of MPH as a cocaine substitute and its clinical potential in the treatment of cocaine dependence. Methods We searched MEDLINE for clinical studies using MPH in patients with cocaine abuse/dependence and screened the bibliographies of the articles found for pertinent literature. Results MPH, like cocaine, increases synaptic dopamine by inhibiting dopamine reuptake. The discriminative properties, reinforcing potential, and subjective effects of MPH and cocaine are almost identical and, importantly, MPH has been found to substitute for cocaine in animals and human volunteers under laboratory conditions. When taken orally in therapeutic doses, its abuse liability, however, appears low, which is especially true for extended-release MPH preparations. Though there are promising data in the literature, mainly from case reports and open-label studies, the results of randomized controlled trials have been disappointing so far and do not corroborate the use of MPH as a substitute for cocaine dependence in patients without attention deficit hyperactivity disorder. Conclusion Clinical studies evaluating MPH substitution for cocaine dependence have provided inconsistent findings. However, the negative findings may be explained by specific study characteristics, among them dosing, duration of treatment, or sample size. This needs to be considered when discussing the potential of MPH as replacement therapy for cocaine dependence. Finally, based on the results, we suggest possible directions for future research.

Neural correlates of pre‐attentive processing of pattern deviance in professional musicians

Pre‐attentive registration of aberrations in predictable sound patterns is attributed to the temporal cortex. However, electrophysiology suggests that frontal areas become more important when deviance complexity increases. To play an instrument in an ensemble, professional musicians have to rely on the ability to detect even slight deviances from expected musical patterns and therefore have highly trained aural skills. Here, we aimed to identify the neural correlates of experience‐driven plasticity related to the processing of complex sound features. We used functional magnetic resonance imaging in combination with an event‐related oddball paradigm and compared brain activity in professional musicians and non‐musicians during pre‐attentive processing of melodic contour variations. The melodic pattern consisted of a sequence of five tones each lasting 50 ms interrupted by silent interstimulus intervals of 50 ms. Compared to non‐musicians, the professional musicians showed enhanced activity in the left middle and superior temporal gyri, the left inferior frontal gyrus and in the right ventromedial prefrontal cortex in response to pattern deviation. This differential brain activity pattern was correlated with behaviorally tested musical aptitude. Our results thus support an experience‐related role of the left temporal cortex in fast melodic contour processing and suggest involvement of the prefrontal cortex. Hum Brain Mapp, 2009.