Lutz Jäncke

The musician's brain as a model of neuroplasticity.

Studies of experience-driven neuroplasticity at the behavioural, ensemble, cellular and molecular levels have shown that the structure and significance of the eliciting stimulus can determine the neural changes that result. Studying such effects in humans is difficult, but professional musicians represent an ideal model in which to investigate plastic changes in the human brain. There are two advantages to studying plasticity in musicians: the complexity of the eliciting stimulus — music — and the extent of their exposure to this stimulus. Here, we focus on the functional and anatomical differences that have been detected in musicians by modern neuroimaging methods.

In vivo evidence of structural brain asymmetry in musicians.

Certain human talents, such as musical ability, have been associated with left-right differences in brain structure and function. In vivo magnetic resonance morphometry of the brain in musicians was used to measure the anatomical asymmetry of the planum temporale, a brain area containing auditory association cortex and previously shown to be a marker of structural and functional asymmetry. Musicians with perfect pitch revealed stronger leftward planum temporale asymmetry than nonmusicians or musicians without perfect pitch. The results indicate that outstanding musical ability is associated with increased leftward asymmetry of cortex subserving music-related functions.

Increased corpus callosum size in musicians.

Using in-vivo magnetic resonance morphometry it was investigated whether the midsagittal area of the corpus callosum (CC) would differ between 30 professional musicians and 30 age-, sex- and handedness-matched controls. Our analyses revealed that the anterior half of the CC was significantly larger in musicians. This difference was due to the larger anterior CC in the subgroup of musicians who had begun musical training before the age of 7. Since anatomic studies have provided evidence for a positive correlation between midsagittal callosal size and the number of fibers crossing through the CC, these data indicate a difference in interhemispheric communication and possibly in hemispheric (a)symmetry of sensorimotor areas. Our results are also compatible with plastic changes of components of the CC during a maturation period within the first decade of human life, similar to those observed in animal studies.

Recognition of emotional prosody and verbal components of spoken language: an fMRI study

This study examined the neural areas involved in the recognition of both emotional prosody and phonemic components of words expressed in spoken language using echo-planar, functional magnetic resonance imaging (fMRI). Ten right-handed males were asked to discriminate words based on either expressed emotional tone (angry, happy, sad, or neutral) or phonemic characteristics, specifically, initial consonant sound (bower, dower, power, or tower). Significant bilateral activity was observed in the detection of both emotional and verbal aspects of language when compared to baseline activity. We found that the detection of emotion compared with verbal detection resulted in significant activity in the right inferior frontal lobe. Conversely, the detection of verbal stimuli compared with the detection of emotion activated left inferior frontal lobe regions most significantly. Specific analysis of the anterior auditory cortex revealed increased right hemisphere activity during the detection of emotion compared to activity during verbal detection. These findings illustrate bilateral involvement in the detection of emotion in language while concomitantly showing significantly lateralized activity in both emotional and verbal detection, in both the temporal and frontal lobes.

A Process Model of the Formation of Spatial Presence Experiences

In order to bridge interdisciplinary differences in Presence research and to establish connections between Presence and “older” concepts of psychology and communication, a theoretical model of the formation of Spatial Presence is proposed. It is applicable to the exposure to different media and intended to unify the existing efforts to develop a theory of Presence. The model includes assumptions about attention allocation, mental models, and involvement, and considers the role of media factors and user characteristics as well, thus incorporating much previous work. It is argued that a commonly accepted model of Spatial Presence is the only solution to secure further progress within the international, interdisciplinary and multiple-paradigm community of Presence research.

Motor cortex and hand motor skills: Structural compliance in the human brain

Recent studies in humans and nonhuman primates have shown that the functional organization of the human sensorimotor cortex changes following sensory stimulation or following the acquisition of motor skills. It is unknown whether functional plasticity in response to the acquisition of new motor skills and the continued performance of complicated bimanual movements for years is associated with structural changes in the organization of the motor cortex. Professional musicians, especially keyboard and string players, are a prototypical group for investigating these changes in the human brain. Using magnetic resonance images, we measured the length of the posterior wall of the precentral gyrus bordering the central sulcus (intrasulcal length of the precentral gyrus, ILPG) in horizontal sections through both hemispheres of right‐handed keyboard players and of an age‐ and handedness‐matched control group. Lacking a direct in vivo measurement of the primary motor cortex in humans, we assumed that the ILPG is a measure of the size of the primary motor cortex. Left‐right asymmetry in the ILPG was analyzed and compared between both groups. Whereas controls exhibited a pronounced left‐larger‐than‐right asymmetry, keyboard players had more symmetrical ILPG. The most pronounced differences in ILPG between keyboard players and controls were seen in the most dorsal part of the presumed cortical hand representation of both hemispheres. This was especially true in the nondominant right hemispheres. The size of the ILPG was negatively correlated with age of commencement of musical training in keyboard players, supporting our hypothesis that the human motor cortex can exhibit functionally induced and long‐lasting structural adaptations. Hum. Brain Mapping 5:206–215, 1997.

Plaque Ulceration and Lumen Thrombus Are the Main Sources of Cerebral Microemboli in High-grade Internal Carotid Artery Stenosis

BACKGROUND AND PURPOSE Previous work has shown that rates of cerebral microemboli downstream of high-grade internal carotid artery stenosis are higher in recently symptomatic compared with asymptomatic patients. In addition, microembolic rates decline after carotid endarterectomy. We conducted a prospective investigation of 40 consecutive asymptomatic or recently symptomatic patients undergoing carotid endarterectomy for 70% to 95% internal carotid artery stenosis to determine the relationship between microembolic rate and pathoanatomic features of the carotid plaque. METHODS Transcranial Doppler monitoring including automated emboli detection was performed preoperatively to assess the rate of cerebral microemboli of the ipsilateral middle cerebral artery. The corresponding endarterectomy specimens were evaluated histologically with respect to the occurrence of plaque fissuring, intraplaque hemorrhage, plaque ulceration, or intraluminal thrombosis. RESULTS There were strong associations between plaque ulceration, intraluminal thrombosis, and downstream cerebral microemboli (P < or = .005, respectively). There were no correlations of microembolism with plaque fissuring or intraplaque hemorrhage (P = .82 and P = .28, respectively). CONCLUSIONS We conclude that ulceration and luminal thrombosis of the atheromatous plaque are the main sources of downstream cerebral microemboli in patients with high-grade internal carotid artery stenosis. Our data support the view that these pathoanatomic features may also play a key role in symptom development.

Phonetic perception and the temporal cortex.

Recent functional neuroimaging studies have emphasized the role of the different areas within the left superior temporal sulcus (STS) for the perception of various speech stimuli. We report here the results of three independent studies additionally demonstrating hemodynamic responses in the vicinity of the planum temporale (PT). In these studies we used consonant-vowel (CV) syllables, tones, white noise, and vowels as acoustic stimuli in the context of whole-head functional magnetic resonance imaging, applying a long TR to attenuate possible masking effects by the scanner noise. To summarize, we obtained the following results for the contrasts comparing hemodynamic responses obtained during the perception of CV syllables compared to tones or white noise: (i) stronger activation in the vicinity of the left PT with two distinct foci of activation, one in a lateral position and the other more medial in the vicinity of Heschls sulcus; (ii) stronger activation in the vicinity of the right PT; and (iii) stronger bilateral activation within the mid-STS. Further contrasts revealed the following findings: (iv) stronger bilateral activation to CV syllables than to vowels in the medial PT, (v) stronger left-sided activation to CV syllables than to vowels in the mid-STS, and (vi) stronger activation to CV syllables with voiceless initial consonants than to CV syllables with voiced initial consonants in the left medial PT. The results are compatible with the hypothesis that the STS contains neurons specialized for speech perception. However, these results also emphasize the role of the PT in the analysis of phonetic features, namely the voice-onset-time. Yet this does not mean that the PT is solely specialized for phonetic analysis. We hypothesize rather that the PT contains neurons specialized for the analysis of rapidly changing cues as was suggested by P. Tallal et al. (1993, Ann. N. Y. Acad. Sci. 682: 27-47).

Women and men exhibit different cortical activation patterns during mental rotation tasks

The strongest sex differences on any cognitive task, favoring men, are found for tasks that require the mental rotation of three-dimensional objects. A number of studies have explored functional brain activation during mental rotation tasks, and sex differences have been noted in some. However, in these studies there was a substantial confounding factor because male and female subjects differed in overall performance levels. In contrast, our functional brain activation study examined cortical activation patterns for males and females who did not differ in overall level of performance on three mental rotation tasks. This allowed us to eliminate any confounding influences of overall performance levels. Women exhibited significant bilateral activations in the intraparietal sulcus (IPS) and the superior and inferior parietal lobule, as well as in the inferior temporal gyrus (ITG) and the premotor areas. Men showed significant activation in the right parieto-occitpital sulcus (POS), the left intraparietal sulcus and the left superior parietal lobule (SPL). Both men and women showed activation of the premotor areas but men also showed an additional significant activation of the left motor cortex. No significant activation was found in the inferior temporal gyrus. Our results suggest that there are genuine between-sex differences in cerebral activation patterns during mental rotation activities even when performances are similar. Such differences suggest that the sexes use different strategies in solving mental rotation tasks.

Interhemispheric asymmetry of the human motor cortex related to handedness and gender.

Most people are right-handed, preferring the right hand for skilled as well as unskilled activities, but a notable proportion are mixed-handed, preferring to use the right hand for some actions and the left hand for others. Assuming a structural/functional correlation in the motor system we tested whether asymmetries in hand performance in consistent right and left handers as well as in mixed handers are associated with anatomical asymmetries in the motor cortex. In vivo MR morphometry was used for analyzing interhemispheric asymmetry in the depth of the central sulcus in the region of cortical hand representation of 103 healthy subjects. Subjects were tested both for hand preference and hand performance. As expected, left-right differences in hand performance differed significantly between consistent right, consistent left and mixed handers and were independent on gender. Male consistent right handers showed a significant deeper central sulcus on the left hemisphere than on the right. Anatomical asymmetries decreased significantly from male consistent right over mixed to consistent left handers. Sixty two per cent of consistent left handers revealed a deeper central sulcus on the right than on the left hemisphere, but for the group as a whole this rightward asymmetry was not significant. No interhemispheric asymmetry was found in females. Thus, anatomical asymmetry was associated with handedness only in males, but not in females, suggesting sex differences in the cortical organization of hand movements.