Neuroarchitecture of verbal and tonal working memory in nonmusicians and musicians.

Working memory (WM) for auditory information has been thought of as a unitary system, but whether WM for verbal and tonal information relies on the same or different functional neuroarchitectures has remained unknown. This fMRI study examines verbal and tonal WM in both nonmusicians (who are trained in speech, but not in music) and highly trained musicians (who are trained in both domains). The data show that core structures of WM are involved in both tonal and verbal WM (Broca's area, premotor cortex, pre-SMA/SMA, left insular cortex, inferior parietal lobe), although with significantly different structural weightings, in both nonmusicians and musicians. Additionally, musicians activated specific subcomponents only during verbal (right insular cortex) or only during tonal WM (right globus pallidus, right caudate nucleus, and left cerebellum). These results reveal the existence of two WM systems in musicians: A phonological loop supporting rehearsal of phonological information, and a tonal loop supporting rehearsal of tonal information. Differences between groups for tonal WM, and between verbal and tonal WM within musicians, were mainly related to structures involved in controlling, programming and planning of actions, thus presumably reflecting differences in action-related sensorimotor coding of verbal and tonal information.

A traffic perimetry test that adheres to the European visual field requirements.

PURPOSE: European visual requirements for driving generally follow the standards of the European Union (EU), but the lack of a uniform perimetry algorithm leads to differing practices in enforcing visual field regulations. The purpose of this study was to develop a perimetry algorithm for group 1 driving licenses (car and motorcycle) that adheres to the European requirements. METHODS: We determined the features of a traffic perimetry algorithm complying with the EU directive 2009/113/EC and the underlying scientific report by the Eyesight Working Group. The final algorithm was a binocular, supra-threshold test with 37 central and 86 peripheral test points within 140º x 40º. It was created as a custom test for an Octopus 900 perimeter and tested on participants with known visual field defects. Findings were compared with the Esterman program in reference to British and Norwegian regulations, which both recommend the Esterman program for assessing fitness to drive but differ in definition of negative and positive results. RESULTS: Twenty-five participants were examined. In comparison with the traffic perimetry algorithm, sensitivity and specificity of the British regulations were 0.78 (95% confidence interval (CI) 0.40-0.97) and 1.00 (95% CI 0.79-1.00). Similarly, sensitivity and specificity of the Norwegian regulations were 0.89 (95% CI 0.52-1.00) and 0.81 (95% CI 0.54-0.96). CONCLUSION: The lack of a perimetry algorithm that conforms to the scientific recommendations challenges the fundamental right of European drivers for legal equality. This study demonstrates a binocular supra-threshold test that adheres to the European visual field requirements for group 1 driving licenses.

Neural substrates of incongruity-resolution and nonsense humor.

By means of functional magnetic resonance imaging the present paper analyzes the neural correlates of processing and appreciating incongruity-resolution and nonsense cartoons. Furthermore, the relation between experience seeking and these neural substrates was investigated as this personality characteristic is known to influence humor appreciation. In the processing of incongruity-resolution stimuli the incongruity of the joke is largely resolvable, whereas in nonsense stimuli it is only partially resolvable and more incongruity remains. The anterior medial prefrontal cortex, bilateral superior frontal gyri and temporo-parietal junctions (TPJ) show more activation during processing of incongruity-resolution than of nonsense cartoons. These differences indicate that processing of incongruity-resolution cartoons requires more integration of multi-sensory information and coherence building, as well as more mental manipulation and organization of information. In addition, less self-reference might be established in nonsense cartoons as it is more absurd and more often deals with impossible situations. Higher experience-seeking scores correlate with increased activation in prefrontal, posterior temporal regions and the hippocampus. This might be due to a more intense exploration of the humorous stimuli as experience seekers tend to search novel mental stimulation. Furthermore, experience seeking was positively associated with brain reactivity towards processing nonsense in contrast to incongruity-resolution stimuli, which is in line with behavioral studies that showed a preference for nonsense humor by experience seekers.

Hypercapnia-induced effects on image contrast based on intermolecular double-quantum coherences.

Intermolecular double-quantum coherences (iDQCs) are well known to be sensitive to magnetic-field perturbations inside tissues. However, the exact relation between iDQC contrast in magnetic resonance imaging (MRI) and the underlying physiology is less well understood. To investigate parameters that influence iDQC signal changes observed during neuronal activation, carbogen-inhalation experiments were performed to produce a pure hemodynamic response without affecting oxidative metabolism. Eight human volunteers were studied at 2.9 T using gradient-recalled echo (GRE) and spin-echo (SE) variants of a single-shot sequence selecting iDQCs. Results were compared with conventional recordings of the blood oxygen level-dependent (BOLD) effect. Maps of voxels responding to the carbogen challenge showed similar distributions for iDQC and conventional MRI after adjustment for different sensitivities. Strong diffusion weighting of iDQC sequences and transverse relaxation effects suggested quantitative suppression of intravascular signal contributions. A particular susceptibility to local gradients during the evolution period (in which iDQCs evolve at twice the Larmor frequency) plus a strong relaxation weighting during the detection period due to the use of a long echo time (for refocusing of the dipolar signal) produced iDQC signal changes up to 21.7% +/- 2.5%. These results agreed quantitatively with computations based on the balloon model of BOLD-weighted MRI without requiring further assumptions.

Neuroplasticity of sign language: implications from structural and functional brain imaging.

PURPOSE: The present study was designed to investigate the neural correlates of German Sign Language (Deutsche Gebärdensprache; DGS) processing. In particular, was expected the impact of the visuo-spatial mode in sign language on underlying neural networks compared to the impact of the interpretation of linguistic information. METHODS: For this purpose, two groups of participants took part in a functional MRI study at 3 Tesla. One group consisted of prelingually deafened users of DGS, the other group of hearing non-signers naïve to sign language. The two groups were presented with identical video sequences comprising DGS sentences in form of dialoges. To account for substantial interindividual anatomical variability observed in the group of deaf participants, the brain responses in the two groups of subjects were analyzed with two different procedures. RESULTS: Results from a multi-subject averaging approach were contrasted with an analysis, which can account for the considerable inter-individual variability of gross anatomical landmarks. The anatomy-based approach indicated that individuals' responses to proper DGS processing was tied up with a leftward asymmetry in the dorsolateral prefrontal cortex, anterior and middle temporal gyrus, and visual association cortices. In contrast, standard multi-subject averaging of deaf individuals during DGS perception revealed a less lateralized peri- and extrasylvian network. Furthermore, voxel-based analyses of the brains' morphometry evidenced a white-matter deficit in the left posterior longitudinal and inferior uncinate fasciculi and a steeper slope of the posterior part of the left Sylvian Fissure (SF) in the deaf individuals. CONCLUSION: These findings may imply that the cerebral anatomy of deaf individuals has undergone structural changes as a function of monomodal visual sign language perception during childhood and adolescence.

Regional impairment of cerebrovascular reactivity and BOLD signal in adults after stroke.

BACKGROUND AND PURPOSE: Comparative studies across populations using functional magnetic resonance imaging (fMRI) rely on a similar relationship between blood oxygen level-dependent (BOLD) signal and neural activity. However, in elderly and patients with cerebrovascular disease, impaired cerebrovascular dynamics and neurovascular coupling may explain differences in BOLD contrast across populations and brain regions. The purpose of the study was to determine whether poststroke patients have regional heterogeneities of cerebrovascular reactivity (CVR) and their potential influence on voxel-wise motor-related BOLD signal. METHODS: Using fMRI, 8 fully recovered patients from stroke in the frontal lobe without cortical lesion in the regions of interest located in the primary sensorimotor cortex (SMC), supplementary motor area (SMA), and cerebellum (CRB) were compared with 8 healthy subjects. Motor-related BOLD signal changes (%SC) were evaluated during simple unimanual and bimanual tasks, and CVR was evaluated during hyperventilation (HV). Analyses were performed using Lipsia software in SMC, SMA, and CRB. RESULTS: In controls, amplitudes of BOLD signal were symmetrical in all regions of interest during all motor tasks and HV. In patients, %SC was decreased in SMC and SMA of the lesioned hemisphere despite their apparent anatomical integrity for all tasks. Impaired CVR was a predictor of impaired motor-related BOLD response in the SMC during contralateral movements (beta=-1.87; R=-0.75; P=0.03). CONCLUSIONS: These preliminary findings suggest that CVR heterogeneities may account for task-related BOLD signal changes in patients after stroke.

Distinct fMRI responses to laughter, speech, and sounds along the human peri-sylvian cortex.

In this event-related fMRI study, 12 right-handed volunteers heard human laughter, sentential speech, and nonvocal sounds in which global temporal and harmonic information were varied whilst they were performing a simple auditory target detection. This study aimed to delineate distinct peri-auditory regions which preferentially respond to laughter, speech, and nonvocal sounds. Results show that all three types of stimuli evoked blood-oxygen-level-dependent responses along the left and right peri-sylvian cortex. However, we observed differences in regional strength and lateralization in that (i) hearing human laughter preferentially involves auditory and somatosensory fields primarily in the right hemisphere, (ii) hearing spoken sentences activates left anterior and posterior lateral temporal regions, (iii) hearing nonvocal sounds recruits bilateral areas in the medial portion of Heschl's gyrus and at the medial wall of the posterior Sylvian Fissure (planum parietale and parietal operculum). Generally, the data imply a differential regional sensitivity of peri-sylvian areas to different auditory stimuli with the left hemisphere responding more strongly to speech and with the right hemisphere being more amenable to nonspeech stimuli. Interestingly, passive perception of human laughter activates brain regions which control motor (larynx) functions. This observation may speak to the issue of a dense intertwining of expressive and receptive mechanisms in the auditory domain. Furthermore, the present study provides evidence for a functional role of inferior parietal areas in auditory processing. Finally, a post hoc conjunction analysis meant to reveal the neural substrates of human vocal timbre demonstrates a particular preference of left and right lateral parts of the superior temporal lobes for stimuli which are made up of human voices relative to nonvocal sounds.

Where action impairs visual encoding: an event-related fMRI study.

Behavioral experiments revealed an impairment in a perceptual task when a motor task has to be planned in parallel. In two event-related fMRI experiments healthy participants performed a GO-NOGO motor task and a visual identification task. Thus, we were able to investigate the influence of a motor task on visual identification. The paradigm allowed to compare visually identical trials with and without a concurrently performed motor response. In Experiment 1, the visual task focused on shape identification, whereas in Experiment 2, the visual task focused on color identification. We found an action-dependent BOLD response modulation in extrastriate visual areas (V3, V3A in Experiment 1 and additionally V4 in Experiment 2). Thus, results demonstrate that the planning of an action has modulatory effects in brain areas concerned with early processes in visual encoding.

Rule learning in a serial reaction time task: an fMRI study on patients with early Parkinson's disease.

In the present study, we investigated implicit rule learning in patients with Parkinson's disease (PD) and healthy participants. Functional magnetic resonance imaging (fMRI) and a variant of the serial reaction time task were employed to examine the performance of previously learned regular sequences. Participants responded to successively appearing visual stimuli by pressing spatially corresponding keys. Unbeknownst to them, a cycling 12-item sequence was presented. In order to measure rule learning independently from initial visuomotor learning, participants were trained with the sequence prior to scanning. In the fMRI session, alternating blocks of regular and random stimuli were performed. Imaging revealed activations in the frontomedian and posterior cingulate cortex during performance of sequence blocks as opposed to random blocks. The magnitude of activations in these two areas was correlated with the behavioral index for rule learning. As has been reported earlier, the frontomedian cortex may be involved in the prediction of future stimuli and anticipation of corresponding actions, whereas the posterior cingulate activation may rather be related to memory retrieval. Additional activations of the right putamen and the inferior frontal sulcus were not related to behavioral performance. In patients with early PD, the behavioral data showed reduced training effects during pretraining, but intact rule learning during the fMRI session. Imaging revealed highly similar frontomedian and posterior cingulate activations in patients and controls, in the absence of significant striatal and inferior frontal activations in patients. Our findings support the view that in early PD, with the lateral striatofrontal dopaminergic projections being affected, medial dopaminergic projections involved in the application of previously learned rules may still be spared.

Functional specialization within the anterior medial prefrontal cortex: a functional magnetic resonance imaging study with human subjects.

This study investigated the functional neuroanatomy of the anterior medial prefrontal cortex (aMPFC). Previous studies have shown that the aMPFC is involved in evaluative judgment and self-referential processes. Specifically, different sections of the aMPFC are differentially influenced by attention demanding processes. Whereas the dorsal section is supposed to be involved in self-referential processes, the ventral section is assumed to be attenuated during attention demanding processes. The present study investigates the involvement of the dorsal and ventral aMPFC in evaluative judgment by using functional magnetic resonance imaging with spin-echo echo-planar-imaging. Processes involved in evaluative judgment are attention-demanding, self-referential and activate regions in the dorsal and ventral section of the aMPFC. Attention demanding tasks do not necessarily lead to an attenuation of the ventral section of the aMPFC, a region mainly involved in emotional and affective processing.

Traumatic brain injury affects the frontomedian cortex--an event-related fMRI study on evaluative judgments.

Traumatic brain injuries represent the leading cause of death and disability in young adults in industrialized countries. Recently, it has been suggested that dysfunctions of the frontomedian cortex, which enables social cognition, are responsible for clinical deficits in the long-term. To validate this hypothesis, we examined brain activation in seven young adults suffering from diffuse axonal injury during a cognitive task that specifically depends on frontomedian structures, namely evaluative judgments, contrasted with semantic memory retrieval. Brain activation in patients was compared with healthy age and gender matched control subjects using event-related functional magnetic resonance imaging. Evaluative judgments were related to a neural network discussed in the context of self-referential processing and theory of mind. More precisely, the neural network consisted of frontomedian regions, the temporal pole, and the posterior superior temporal gyrus and sulcus/angular gyrus. Patients showed higher activations in this network and the inferior frontal gyrus, whereas healthy control subjects activated more dopaminergic structures, namely the ventral tegmental area, during evaluative judgments. One possible interpretation of the data is that deficits in the ventral tegmental area, and consequently the mesocorticolimbic projection system, have to be compensated for by higher brain activations in the frontomedian and anterior cingulate cortex in patients with diffuse axonal injury. In conclusion, our study supports the hypothesis that traumatic brain injury is characterized by frontomedian dysfunctions, which may be responsible for clinical deficits in the long-term and which might be modified by rehabilitative strategies in the future.

Cognitive humor processing: different logical mechanisms in nonverbal cartoons--an fMRI study.

Although recent fMRI studies on humor have begun to elucidate cognitive and affective neural correlates, they weren't able to distinguish between different logical mechanisms or steps of humor processing, i.e., the detection of an incongruity and its resolution. This fMRI study aimed to focus in more detail on cognitive humor processing. In order to investigate pure incongruity resolution without preprocessing steps, nonverbal cartoons differing in their logical mechanisms were contrasted with nonhumorous pictures containing an irresolvable incongruity. The logical mechanisms were: (1) visual puns (visual resemblance, PUNs); (2) semantic cartoons (pure semantic relationships, SEMs); and (3) Theory of Mind cartoons (which require additionally mentalizing abilities, TOMs). Thirty cartoons from each condition were presented to 17 healthy subjects while acquiring fMR images. The results reveal a left-sided network involved in pure incongruity resolution: e.g., temporo-parietal junction, inferior frontal gyrus and ventromedian prefrontal cortex. These areas are also involved in processing of SEMs, whereas PUNs show more activation in the extrastriate cortex and TOMs show more activation in so-called mentalizing areas. Processing of pictures containing an irresolvable incongruity evokes activation in the rostral cingulate zone, which might reflect error processing. We conclude that cognitive processing of different logical mechanisms depends on separate neural networks.

Brain activity in hunger and satiety: an exploratory visually stimulated FMRI study.

OBJECTIVE: To explore neuroanatomical sites of eating behavior, we have developed a simple functional magnetic resonance imaging (fMRI) paradigm to image hunger vs. satiety using visual stimulation. METHODS AND PROCEDURES: Twelve healthy, lean, nonsmoking male subjects participated in this study. Pairs of food-neutral and food-related pictures were presented in a block design, after a 14-h fast and 1 h after ad libitum ingestion of a mixed meal. Statistically, a general linear model for serially autocorrelated observations with a P level<0.001 was used. RESULTS: During the hunger condition, significantly enhanced brain activity was found in the left striate and extrastriate cortex, the inferior parietal lobe, and the orbitofrontal cortices. Stimulation with food images was associated with increased activity in both insulae, the left striate and extrastriate cortex, and the anterior midprefrontal cortex. Nonfood images were associated with enhanced activity in the right parietal lobe and the left and right middle temporal gyrus. A significant interaction in activation pattern between the states of hunger and satiety and stimulation with food and nonfood images was found for the left anterior cingulate cortex, the superior occipital sulcus, and in the vicinity of the right amygdala. DISCUSSION: These preliminary data from a homogenous healthy male cohort suggest that central nervous system (CNS) activation is not only altered with hunger and satiety but that food and nonfood images have also specific effects on regional brain activity if exposure takes place in different states of satiety. Wider use of our or a similar approach would help to establish a uniform paradigm to map hunger and satiety to be used for further experiments.

Cross-cultural music phrase processing: an fMRI study.

The current study used functional magnetic resonance imaging (fMRI) to investigate the neural basis of musical phrase boundary processing during the perception of music from native and non-native cultures. German musicians performed a cultural categorization task while listening to phrased Western (native) and Chinese (non-native) musical excerpts as well as modified versions of these, where the impression of phrasing has been reduced by removing the phrase boundary marking pause (henceforth called "unphrased"). Bilateral planum temporale was found to be associated with an increased difficulty of identifying phrase boundaries in unphrased Western melodies. A network involving frontal and parietal regions showed increased activation for the phrased condition with the orbital part of left inferior frontal gyrus presumably reflecting working memory aspects of the temporal integration between phrases, and the middle frontal gyrus and intraparietal sulcus probably reflecting attention processes. Areas more active in the culturally familiar, native (Western) condition included, in addition to the left planum temporale and right ventro-medial prefrontal cortex, mainly the bilateral motor regions. These latter results are interpreted in light of sensorimotor integration. Regions with increased signal for the unfamiliar, non-native music style (Chinese) included a right lateralized network of angular gyrus and the middle frontal gyrus, possibly reflecting higher demands on attention systems, and the right posterior insula suggesting higher loads on basic auditory processing.

When vocal processing gets emotional: on the role of social orientation in relevance detection by the human amygdala.

Previous work on vocal emotional processing provided little evidence for involvement of emotional processing areas such as the amygdala or the orbitofrontal cortex (OFC). Here, we sought to specify whether involvement of these areas depends on how relevant vocal expressions are for the individual. To this end, we assessed participants' social orientation--a measure of the interest and concern for other individuals and hence the relevance of social signals. We then presented task-irrelevant syllable sequences that contained rare changes in tone of voice that could be emotional or neutral. Processing differences between emotional and neutral vocal change in the right amygdala and the bilateral OFC were significantly correlated with the social orientation measure. Specifically, higher social orientation scores were associated with enhanced amygdala and OFC activity to emotional as compared to neutral change. Given the presumed role of the amygdala in the detection of emotionally relevant information, our results suggest that social orientation enhances this detection process and the activation of emotional representations mediated by the OFC. Moreover, social orientation may predict listener responses to vocal emotional cues and explain interindividual variability in vocal emotional processing.

The role of the posterior superior temporal sulcus in the processing of unmarked transitivity.

Is it living or not? The ability to differentiate between animate and inanimate entities is of considerable value in everyday life, since it allows for the dissociation of individuals that may willfully cause an action from objects that cannot. The present fMRI study aimed to shed light on the neural correlates of animacy at a relational-interpretive level, i.e. on the role of animacy in the establishment of relations between entities that are more or less likely to cause an event and differ in their potential to act volitionally. To this end, we investigated the processing of visually presented transitive German sentences (nominative-accusative structures) in which the factors animacy and argument order were manipulated. The relations between the arguments differed in that the animate subject either acted on an inanimate object (a very natural construction in terms of transitivity) or on an animate object (resulting in a sentence deviating from an unmarked transitive structure). Participants performed an acceptability judgment task. Violations of unmarked transitivity yielded a significant activation increase within the posterior left superior temporal sulcus (pSTS), thus suggesting a specific role of this cortical region in the relational use of animacy information. This result indicates that the influence of animacy as a relational feature differs from the impact of this parameter on the word level and is in line with other neuroimaging studies showing an engagement of the pSTS when a matching between syntax and semantics is required. A comparison between object- and subject-initial conditions further revealed a robust effect of argument order in the pars opercularis of the left inferior frontal gyrus (a subregion of Broca's area), thereby replicating previous findings demonstrating a sensitivity of this region to fine-grained language-specific linearization rules.

Stroop interference, hemodynamic response and aging: an event-related fMRI study.

In a Stroop interference task, subjects are required to name the color of a word, while ignoring the meaning of the word. The increase in time taken to name the color name if the underlying word is incongruent to the color is called Stroop color-word interference effect. With increasing age, reaction time (RT) is slowed. In an functional magnetic resonance imaging (fMRI) study we investigated the effects of aging (subjects from 22 to 75 years of age) on the performance in the color-word matching Stroop task and on the hemodynamic response. The present study shows that middle-aged adults were generally slowed but no increased interference effect occurred. Further, middle-aged adults showed increased activations in several task-related regions, mainly in the inferior frontal junction (IFJ) area (bilaterally) and the presupplementary motor area. For the middle-aged subjects, regions in the inferior frontal gyrus (IFG), the basal putamen and the occipital lobe were additionally recruited, indicating a stronger dependence on compensatory strategies. Further, middle-aged subjects showed generally a greater magnitude of the hemodynamic response, resulting in greater percent signal changes.

Variability of the BOLD response over time: an examination of within-session differences.

Model-based analysis methods for fMRI data assume a priori knowledge of the time course of the hemodynamic response (HR) in reaction to experimental stimuli or events. This knowledge is incorporated into the hemodynamic response function (HRF), which is a common model of the HR. Although it is already known that the HR varies across individuals and brain regions, few studies have investigated how variations within one session affect the results of statistical analysis using the general linear model (GLM). In this study, we formally tested for a possible variation of the BOLD response during prolonged functional measurement (120 min). To provoke performance of simple visual, motor, and cognitive tasks, we opted for a combination of a variant of the Stroop task and rotating L's. In selected regions of interest, time courses were extracted and compared with regard to mean and maximum amplitudes throughout the time of functional measurement. Additionally, parameter estimates derived from the GLM were tested for differences over time. Although differences between conditions were found to be significant, results did not show significant variance due to a within-factor time. Similarly, a temporal change in the relation between conditions, in terms of an interaction between the within-factor time and the within-factor condition, was not detectable by a repeated measures ANOVA. Similar results were obtained for analysis of mean and maximum amplitudes as well as for the analyses of parameter estimates.

Native and non-native reading of sentences: an fMRI experiment.

The processing of syntactic and semantic information in written sentences by native (L1) and non-native (L2) speakers was investigated in an fMRI experiment. This was done by means of a violation paradigm, in which participants read sentences containing either a syntactic, a semantic, or no violation. The results of this study were compared to those of a previous fMRI study, in which auditory sentence processing in L1 and L2 was investigated. The results indicate greater activation for L2 speakers as compared to L1 speakers when reading sentences in several language- and motor-related brain regions. The processing of syntactically incorrect sentences elicited no reliably greater activation in language areas in L2 speakers. In L1 speakers, on the other hand, syntactic processing, as compared to semantic processing, was associated with increased activation in left mid to posterior superior temporal gyrus. In response to the processing of semantically incorrect sentences, both L2 and L1 speakers demonstrated increased involvement of left inferior frontal gyrus. The results of this study were compared to a previously conducted fMRI study, which made use of identical sentence stimuli in the auditory modality. Results from the two studies are in general agreement with one another, although some differences in the response of brain areas very proximal to primary perceptual processing areas (i.e. primary auditory and visual cortex) were observed in conjunction with presentation in the different modalities. The combined results provide evidence that L1 and L2 speakers rely on the same cortical network to process language, although with a higher level of activation in some regions for L2 processing.