Stefan Zysset

Bach Speaks: A Cortical "Language-Network" Serves the Processing of Music

The aim of the present study was the investigation of neural correlates of music processing with fMRI. Chord sequences were presented to the participants, infrequently containing unexpected musical events. These events activated the areas of Broca and Wernicke, the superior temporal sulcus, Heschls gyrus, both planum polare and planum temporale, as well as the anterior superior insular cortices. Some of these brain structures have previously been shown to be involved in music processing, but the cortical network comprising all these structures has up to now been thought to be domain-specific for language processing. To what extent this network might also be activated by the processing of non-linguistic information has remained unknown. The present fMRI-data reveal that the human brain employs this neuronal network also for the processing of musical information, suggesting that the cortical network known to support language processing is less domain-specific than previously believed.

Lipsia—a new software system for the evaluation of functional magnetic resonance images of the human brain

This paper describes the non-commercial software system LIPSIA that was developed for the processing of functional magnetic resonance images (fMRI) of the human brain. The analysis of fMRI data comprises various aspects including filtering, spatial transformation, statistical evaluation as well as segmentation and visualization. In LIPSIA, particular emphasis was placed on the development of new visualization and segmentation techniques that support visualizations of individual brain anatomy so that experts can assess the exact location of activation patterns in individual brains. As the amount of data that must be handled is enormous, another important aspect in the development LIPSIA was the efficiency of the software implementation. Well established statistical techniques were used whenever possible.

The Anterior Frontomedian Cortex and Evaluative Judgment: An fMRI Study

This study investigated the neuronal basis of evaluative judgment. Judgments can be defined as the assessment of an external or internal stimulus on an internal scale and they are fundamental for decision-making and other cognitive processes. Evaluative judgments (I like George W. Bush: yes/no) are a special type of judgment, in which the internal scale is related to the persons value system (preferences, norms, aesthetic values, etc.). We used functional magnetic resonance imaging to examine brain activation during the performance of evaluative judgments as opposed to episodic and semantic memory retrieval. Evaluative judgment produced significant activation in the anterior frontomedian cortex (BA 10/9), the inferior precuneus (BA 23/31), and the left inferior prefrontal cortex (BA 45/47). The results show a functional dissociation between the activations in the anterior frontomedian cortex and in the inferior precuneus. The latter was mainly activated by episodic retrieval processes, supporting its function as a multimodal association area that integrates the different aspects of retrieved and newly presented information. In contrast, the anterior frontomedian cortex was mainly involved in evaluative judgments, supporting its role in self-referential processes and in the self-initiation of cognitive processes.

Near-infrared spectroscopy can detect brain activity during a color-word matching Stroop task in an event-related design

Brain activity can be monitored non‐invasively by near‐infrared spectroscopy (NIRS), which has several advantages in comparison with other imaging methods, such as flexibility, portability, low cost and biochemical specificity. Moreover, patients and children can be repetitively examined. Therefore, the objective of the study was to test the feasibility of NIRS for the event‐related approach in functional brain activation studies with cognitive paradigms. Thus, changes in the concentration of oxy‐, deoxy‐, and total hemoglobin were measured by NIRS in 14 healthy subjects while performing a color–word matching Stroop task in an event‐related design. The hemodynamic response (increase in the concentration of oxy‐/total hemoglobin and decrease in the concentration of deoxy‐hemoglobin) was stronger during incongruent compared to congruent and neutral trials of the Stroop task in the lateral prefrontal cortex bilaterally. This stronger hemodynamic response was interpreted as a stronger brain activation during incongruent trials of the Stroop task, due to interference. A new method for NIRS data evaluation that enables the analysis of the hemodynamic response to each single trial is introduced. Each hemodynamic response was characterized by the parameters gain, lag and dispersion of a Gaussian function fitted by nonlinear regression. Specific differences between the incongruent and neutral condition were found for gain and lag. Further, these parameters were correlated with the behavioral performance. In conclusion, brain activity may be studied by NIRS using cognitive stimuli in an event‐related design. Hum. Brain Mapping 17:61–71, 2002.

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.

Age dependency of the hemodynamic response as measured by functional near-infrared spectroscopy

Aging reduces cerebral blood flow in association cortices during rest. However, the influence of age on functional brain activation is still controversial. The aim of our study was to examine age dependency of brain activation in primary and association cortices. Therefore, changes in the concentration of oxy- and deoxyhemoglobin as well as changes in the redox state of cytochrome-c-oxidase (Cyt-Ox) were measured by functional near-infrared spectroscopy (fNIRS) in the lateral prefrontal and motor cortices during an event-related Stroop interference task. Fourteen young (23.9 +/- 3.1 years old) and 14 elderly subjects (65.1 +/- 3.1) participated in the study. Data revealed two effects of aging on brain activation: (1) Elderly and young subjects used the lateral prefrontal cortex to cope with interference during the Stroop task. In young subjects, the vascular response was higher during incongruent than neutral trials in the entire examined lateral prefrontal cortex. However, in the elderly, all lateral prefrontal regions showed a hemodynamic response but not necessarily a specific interference effect. (2) The hemodynamic response was reduced in elderly subjects in the lateral prefrontal association cortex, but obviously not in the motor cortex. We propose that calculating effect sizes is the only reliable approach to analyze age-related effects in fNIRS studies, because they are independent from the assumed differential pathlength factor. In summary, our findings suggest that aging decreases the hemodynamic response in the frontal association cortex during functional activation, omitting the primary motor cortex.

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 (Brocas 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. Hum Brain Mapp 32:771–783, 2011.

Prefrontal activation due to Stroop interference increases during development-an event-related fNIRS study

Although it is well known that executive processes supported by the frontal lobe develop during childhood and adolescence, only one functional imaging study has used the Stroop task to investigate the relationship between frontal lobe function and cognition from a developmental point of view. Hence, we measured brain activation in the lateral prefrontal cortex of children with functional near-infrared imaging during an event-related, color-word matching Stroop task and compared results with a previous study, conducted with the same paradigm in adults. In children, the Stroop task elicited significant brain activation in the left lateral prefrontal cortex comparable to adults. However, the hemodynamic response occurred later in children than adults. Individual brain activation due to Stroop interference varied much more in children than adults, which was paralleled by a higher behavioral variance in children. Data suggest that children differed in their individual cognitive development independent of their chronological age more than adults. Brain activation due to Stroop interference increased with age in the dorsolateral prefrontal cortex in correlation with an improvement of behavioral performance. In conclusion, our results indicate that neuromaturational processes regarding resolution of Stroop interference may depend on increased ability to recruit frontal neural resources.

Gender differences in the activation of inferior frontal cortex during emotional speech perception

We investigated the brain regions that mediate the processing of emotional speech in men and women by presenting positive and negative words that were spoken with happy or angry prosody. Hence, emotional prosody and word valence were either congruous or incongruous. We assumed that an fRMI contrast between congruous and incongruous presentations would reveal the structures that mediate the interaction of emotional prosody and word valence. The left inferior frontal gyrus (IFG) was more strongly activated in incongruous as compared to congruous trials. This difference in IFG activity was significantly larger in women than in men. Moreover, the congruence effect was significant in women whereas it only appeared as a tendency in men. As the left IFG has been repeatedly implicated in semantic processing, these findings are taken as evidence that semantic processing in women is more susceptible to influences from emotional prosody than is semantic processing in men. Moreover, the present data suggest that the left IFG mediates increased semantic processing demands imposed by an incongruence between emotional prosody and word valence.

An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

This study examines the value of spin-echo-based fMRI for cognitive studies at the main magnetic field strength of 3 T using a spin-echo EPI (SE-EPI) sequence and a Stroop color-word matching task. SE-EPI has the potential advantage over conventional gradient-echo EPI (GE-EPI) that signal losses caused by dephasing through the slice are not present, and hence although image distortion will be the same as for an equivalent GE-EPI sequence, signal voids will be eliminated. The functional contrast in SE-EPI will be lower than for GE-EPI, as static dephasing effects do not contribute. As an auxiliary experiment interleaved diffusion-weighted and non-diffusion-weighted SE-EPI was performed in the visual cortex to further elucidate the mechanims of functional contrast. In the Stroop experiment activation was detected in all areas previously found using GE-EPI. Additional frontopolar and ventral frontomedian activations were also found, which could not be detected using GE-EPI. The experiments from visual cortex indicated that at 3 T the BOLD signal change has contributions from the extravascular space and larger blood vessels in roughly equal amounts. In comparison with GE-EPI the absence of static dephasing effects would seem to result in a superior intrinsic spatial resolution. In conclusion the sensitivity of SE-EPI at 3 T is sufficient to make it the method of choice for fMR studies that require a high degree of spatial localization or where the requirement is to detect activation in regions affected by strong susceptibility gradients.