Frank Baumgart

A movement-sensitive area in auditory cortex.

It is important to recognize sound patterns, regardless of their position and motion. The ability to locate sound sources and track their motion involves various levels of the auditory pathways,. Motion and pattern analysis may first be spatially separated in the auditory cortex. We have examined this by using functional magnetic resonance imaging (fMRI) and find a higher-order field in the right auditory cortex that is activated by sound motion significantly more than other fields of the auditory cortex. This area distinguishes whether a sound pattern is moving or stationary.

Electrodynamic headphones and woofers for application in magnetic resonance imaging scanners

Electrodynamic speakers compatible with (functional) magnetic resonance imaging (MRI) are described. The speakers magnets are removed, their function is replaced by the scanners magnetic field, resulting in an uncommon but efficient operation. The method can be used with headphones as well as woofers. Functional MRI is not associated with any known biological risks, but as a method for visualization of task-specific activation of brain regions it is undesirably noisy. Thus, it requires both noise protection and efficient sound transmission systems for delivering acoustic stimuli to subjects. Woofers could possibly be used in active noise-control systems. The speakers described in this paper can be used for either task.

Functional magnetic resonance imaging of a human auditory cortex area involved in foreground–background decomposition

Auditory foreground–background decomposition is a pattern recognition process which combines simultaneous and sequential grouping in complex sound sequences. Using functional magnetic resonance imaging with reduced scanner noise and stimulation through a new type of earphones, we investigated the possibility that this process activates topographically distinct areas of human auditory cortex. A basic matching‐to‐sample task with variable tones (sequential grouping) caused significant activity in three separate landmark‐related territories on the supratemporal plane. A similar task in the presence of a strongly masking acoustic background pattern to challenge simultaneous grouping led to the distinction of the subterritory in which foreground signal‐related or task‐related signal properties were exclusively seen. In contrast to the remainder of territories the level of activity and the periodicity of the signal time‐course was resistant to the masking influence of the background.

GABA-ergic Modulation of Prefrontal Spatio-temporal Activation Pattern during Emotional Processing: A Combined fMRI/MEG Study with Placebo and Lorazepam

Various prefrontal cortical regions have been shown to be activated during emotional stimulation, whereas neurochemical mechanisms underlying emotional processing in the prefrontal cortex remain unclear. We therefore investigated the influence of the GABA-A potentiator lorazepam on prefrontal cortical emotionalmotor spatio-temporal activation pattern in a combined functional magnetic resonance imaging/magnetoencephalography study. Lorazepam led to the reversal in orbito-frontal activation pattern, a shift of the early magnetic field dipole from the orbito-frontal to medial prefrontal cortex, and alterations in premotor/motor cortical function during negative and positive emotional stimulation. It is concluded that negative emotional processing in the orbito-frontal cortex may be modulated either directly or indirectly by GABA-A receptors. Such a modulation of orbito-frontal cortical emotional function by lorazepam has to be distinguished from its effects on cortical motor function as being independent from the kind of processing either emotional or nonemotional.

Lateralized processing of speech prosodies in the temporal cortex: a 3-T functional magnetic resonance imaging study

Prosodic modulation of speech provides information about emotional states of speakers (affective prosodies) or serves as syntactic markers to change linguistic aspects of speech (linguistic prosodies). Previous electrophysiological investigations and studies on patients with right or left hemisphere damage showed nonuniform results with respect to lateralization of prosodic processing. In this study 20 healthy right-handed volunteers were investigated with functional magnetic resonance imaging of the acoustically responsive areas on the supratemporal plane while detecting phonemes as control targets or prosodies in strings of nonsense syllables and adjectives, the latter randomly intonated in a declarative, interrogative, commanding, happy, or sad fashion. In control task A the phoneme /a/ was detected in the syllables. In control task B the phoneme /a/ was detected in the adjectives, and in the experimental task C the sad intonations (affective) and in the experimental task D the interrogative intonations (linguistic) had to be detected in the same material. In task A intensity-weighted volumes of activated voxels were not different in the two hemispheres (laterality index 0). In task B with an irrelevant phoneme detection with respect to prosodic material, the population split into two subgroups with similar right or left hemispheric lateralization of activity leading to an absolute laterality index of 26.8 across all subjects. During detection of affective prosodies (task C), lateralization was maintained yet the absolute laterality index reduced to 14.5, while there was no lateralization during detection of linguistic prosodies. The sum of activations in the two hemispheres was the same across all tasks and subgroups, which suggests that the lateralizations occurring with presentation and detection of prosodic material depend on a redistribution of activity between hemispheres.

Activation of Human Auditory Cortex in Retrieval Experiments: An fMRI Study

In a previous functional magnetic resonance (fMRI) study, a subdivision of the human auditory cortex into four distinct territories was achieved. One territory (T1a) exhibited functional specialization in terms of a foreground-background decomposition task involving matching-to-sample monitoring on tone sequences. The present study more specifically determined whether memory-guided analysis of tone sequences is part of the T1a specialization. During the encoding periods, an arbitrary and unfamiliar four-tone-sequence (melody) played by one instrument was presented. The melody-instrument-combination was different in each period. During subsequent retrieval periods, learned and additional combinations were presented, and the tasks were either to detect the target melodies (experiment I) or the target instruments (experiment II). T1a showed larger activation during the melody retrieval. The results generally suggest that (1) activation of T1a during retrieval is determined less by the sound material than by the executed task, and (2) more specifically, that memory-guided sequential analysis in T1a is dominant over recognition of characteristic complex sounds.

Anomalous Auditory Cortex Activations in Colored Hearing Synaesthetes: An fMRI-Study.

Color percept induction in synaesthetes by hearing words was previously shown to involve activation of visual and specifically color processing cortex areas. While this provides a rationale for the origin of the anomalous color percept the question of mechanism of this crossmodal activation remains unclear. We pursued this question with fMRI in color hearing synaesthetes by exposing subjects to words and tones. Brain activations in word condition accompanied by highly reliable color percepts were compared with activations in tone condition with only occasional color percepts and both contrasted to activations in normal subjects under the same stimulus conditions. This revealed that already the tone condition similar to the word condition caused abnormally high activations in various cortical areas even though synaesthetic percepts were more rare. Such tone activations were significantly larger than in normal subjects in visual areas of the right occipital lobe, the fusiform gyrus, and the left middle temporal gyrus and in auditory areas of the left superior temporal gyrus. These auditory areas showed strong word and tone activation alike and not the typically lower tone than word activation in normal subjects. Taken together these results are interpreted in favour of the disinhibited feedback hypothesis as the neurophysiological basis of genuine synaesthesia.

Orbitofrontal Cortical Dysfunction and “Sensori-motor Regression”: A Combined Study of fMRI and Personal Constructs in Catatonia

Objective A close relationship between subjective experience and neurophysiological mechanisms could provide a new foundation for neurobiological correlates underlying psychodynamic processes in neuropsychiatric diseases. Pursuing a novel methodological approach by combining both techniques we investigated catatonia a psychomotor syndrome with uncontrollable anxieties and akinesia i.e., “immobilization by anxieties” which, psychodynamically, can be characterized as a “sensori-motor regression” reflecting a basic somatic defense mechanism. However psychological and physiological mechanisms of generation of such “sensori-motor regression” in catatonia remain unclear. We therefore investigated in a combined study operationalized subjective psychological characteristics using Repertory-Grid Technique as well as prefrontal cortical activation pattern during emotional-motor stimulation using functional magnetic resonance imaging (fMRI). Method We investigated 18 catatonic patients with an underlying affective or schizoaffective psychosis and compared them with age, sex, diagnosis, and medication matched non-catatonic psychiatric controls (n = 69), and healthy controls (n = 32). Subjective operationalized psychological characteristics were investigated using the Repertory Grid Technique (GRID) for personal constructs of the “self” in an acute and a post-acute state. In addition 10 catatonic patients, 10 psychiatric controls and 10 healthy controls underwent emotional stimulation with motor reaction during functional magnetic resonance imaging (fMRI). Results Subjective operationalized psychological characteristics of both the acute and post-acute state could be characterized by significant lack of social contact, decreased self-esteem, and reduced emotional arousal compared to non-catatonic psychiatric and healthy controls. fMRI revealed significant dysfunctional activation patterns in orbitofrontal cortex and alterations in medial prefrontal and premotor cortex during negative emotional stimulation which correlated significantly (p = 0.0082–0.042) with affective, behavioral, and motor alterations in catatonia as well as with the GRID dimensions of self-esteem, emotional arousal, and social contact. Conclusions Subjective operationalized psychological characteristics demonstrate the central importance of lack of emotional control as well as of alterations in interactions between emotional, social, and motor functions in catatonia. Orbitofrontal cortical dysfunction and related alterations in medial prefrontal and premotor cortical activity may account for lack of emotional control with consecutive “sensori-motor regression” as an “immobilization by anxieties” in catatonia. In general one may conclude that orbitofrontal cortical dysfunction may be closely related with regression to somatic defense mechanisms as paradigmatically observed in catatonia.