Transcranial doppler assessment of cerebral flow velocity during perception and recognition of melodies

Music listening after stroke: beneficial effects and potential neural mechanisms

Music is an enjoyable leisure activity that also engages many emotional, cognitive, and motor processes in the brain. Here, we will first review previous literature on the emotional and cognitive effects of music listening in healthy persons and various clinical groups. Then we will present findings about the short- and long-term effects of music listening on the recovery of cognitive function in stroke patients and the underlying neural mechanisms of these music effects. First, our results indicate that listening to pleasant music can have a short-term facilitating effect on visual awareness in patients with visual neglect, which is associated with functional coupling between emotional and attentional brain regions. Second, daily music listening can improve auditory and verbal memory, focused attention, and mood as well as induce structural gray matter changes in the early poststroke stage. The psychological and neural mechanisms potentially underlying the rehabilitating effect of music after stroke are discussed.

Functional brain mapping and its applications to neurosurgery

Functional brain mapping may be useful for both preoperative planning and intraoperative neurosurgical decision making. "Gold standard" functional studies such as direct electrical stimulation and recording are complemented by newer, less invasive techniques such as functional magnetic resonance imaging. Less invasive techniques allow more areas of the brain to be mapped in more subjects (including healthy subjects) more often (including pre- and postoperatively). Expansion of the armamentarium of tools allows convergent evidence from multiple brain mapping techniques to bear on pre- and intraoperative decision making. Functional imaging techniques are used to map motor, sensory, language, and memory areas in neurosurgical patients with conditions as diverse as brain tumors, vascular lesions, and epilepsy. In the future, coregistration of high resolution anatomic and physiological data from multiple complementary sources will be used to plan more neurosurgical procedures, including minimally invasive procedures. Along the way, new insights on fundamental processes such as the biology of tumors and brain plasticity are likely to be revealed.

Functional neuroimaging of semantic and episodic musical memory

The distinction between episodic and semantic memory has become very popular since it was first proposed by Tulving in 1972. So far, very few neuropsychological, psychophysical, and imaging studies have related to the mnemonic aspects of music, notably on the long-term memory features, and practically nothing is known about the functional anatomy of long-term memory for music. Numerous functional imaging studies have shown that retrieval from semantic and episodic memory is subserved by distinct neural networks. For instance, the HERA model (hemispheric encoding/retrieval asymmetry) ascribes to the left prefrontal cortex a preferential role in the encoding process of episodic material and the recall of semantic information, while the right prefrontal cortex would preferentially operate in the recall of episodic information. However, these results were essentially obtained with verbal and visuo-spatial material. We have done a study to determine the neural substrates underlying the semantic and episodic components of music using familiar and nonfamiliar melodic tunes. Two distinct patterns of activations were found: bilateral activation of the middle and superior frontal areas and precuneus for episodic memory, and activation of the medial and orbital frontal cortex bilaterally, left angular gyrus, and the anterior part of the left middle and superior temporal gyri for semantic memory. We discuss these findings in light of the available neuropsychological data obtained in brain-damaged subjects and functional neuroimaging studies.

Cerebral blood flow velocity changes during meaningful and meaningless gestures - a functional transcranial Doppler study

The aim of the study was to use functional transcranial Doppler to investigate the possibility of revealing different activation patterns during healthy subjects' performance of meaningful and meaningless actions. Mean flow velocity (MFV) changes were recorded in middle cerebral arteries (MCAs) of 26 normal subjects during a rest phase and during performance of meaningful and meaningless actions. The meaningful task consisted of pouring sugar into a cup with a teaspoon. The meaningless action was an arm movement similar to that necessary for pouring sugar in a cup but without any tool and thus without a goal. Performing actions with or without meaning was associated with different patterns of MFV changes, as documented by the triple interaction condition x performing arm x side of recording [F(1, 25)=10.977; P=0.003]. During the meaningful action, MFV in MCAs increased significantly more than during the meaningless action. During the meaningless action, the MFV increase was significantly higher in the contralateral than in the ipsilateral MCA to the arm performing the task and the meaningful action determined a bilateral MFV increase only when the task was performed with the left arm. When the same task was performed with the right arm, the MFV increase was significantly higher in the contralateral than in the ipsilateral MCA. These findings suggest that the content of an action can influence MFV changes and further confirm the usefulness of transcranial Doppler in neuropsychological investigation.

Lateralization of Cerebral Blood Flow Velocity Changes During Auditory Stimulation: A Functional Transcranial Doppler Study

Transcranial Doppler ultrasonography (TCD) permits the assessment of cognitively induced cerebral blood flow velocity (BFV) changes. We sought to investigate the lateralization of BFV acceleration induced by auditory stimulation and speech in a normal population. TCD monitoring of BFV in the middle cerebral arteries (MCA) was performed in 30 normal right-handed volunteers (average age = 31.7 years). Noise stimulation, speech, and instrumental music were administered during 60 sec to both ears by means of earphones. Auditory stimulation induced a significant BFV increase in the ipsilateral MCA compared to BFV during the preceding rest periods. Left MCA BFV increased by an average of 7.1% (noise), 8.4% (language), and 5.2% (melody) over baseline values, and right MCA BFV increased 5.1%, 3.1%, and 4.2%, respectively. Speech stimulation produced a significant increase in BFV in the left hemisphere MCA (from 49.86 to 54.03 cm/sec; p < .0001). Left MCA BFV response to speech stimulation may reflect the dominance of the left hemisphere in language processing by right-handed individuals. Due to the high temporal resolution of TCD we were able show a habituation effect during the 60-sec stimulation period.

The investigation of functional brain lateralization by transcranial Doppler sonography

Functional transcranial Doppler sonography (fTCD) adds to the techniques of functional imaging. fTCD measures cerebral perfusion changes related to neural activation in a way comparable to functional magnetic resonance tomography. fTCD contends itself with comparison of averaged, event-related blood flow velocity changes within the territories of two cerebral arteries, for example the left versus the right middle cerebral artery. It can thus serve to evaluate the functional lateralization of higher cognitive functions like hemispheric language dominance (HLD). We present typical applications of fTCD by summarizing studies employing the technique. Then, the physical and physiological underpinnings of fTCD are reviewed. After a brief description of a prototype paradigm for assessing HLD, a detailed outline of the fTCD data analysis is presented. Caveats for fTCD, like other functional imaging techniques, are that the validity of results depends on adequate control of the task parameters, particularly cooperation and reference conditions. We complete the review with examinations of the reliability and validity of the fTCD technique. We conclude that fTCD can be employed to substitute the invasive amobarbital procedure to determine language lateralization in individual patients before undergoing brain surgery. Because of its easy applicability, robustness and mobility, fTCD can also be used to examine many subjects (including children) to obtain representative data on the variability of lateralization of higher cognitive functions, or to scan for atypical patterns of lateralization.

Semantic and episodic memory of music are subserved by distinct neural networks

Numerous functional imaging studies have shown that retrieval from semantic and episodic memory is subserved by distinct neural networks. However, these results were essentially obtained with verbal and visuospatial material. The aim of this work was to determine the neural substrates underlying the semantic and episodic components of music using familiar and nonfamiliar melodic tunes. To study musical semantic memory, we designed a task in which the instruction was to judge whether or not the musical extract was felt as "familiar." To study musical episodic memory, we constructed two delayed recognition tasks, one containing only familiar and the other only nonfamiliar items. For each recognition task, half of the extracts (targets) were presented in the prior semantic task. The episodic and semantic tasks were to be contrasted by a comparison to two perceptive control tasks and to one another. Cerebral blood flow was assessed by means of the oxygen-15-labeled water injection method, using high-resolution PET. Distinct patterns of activations were found. First, regarding the episodic memory condition, bilateral activations of the middle and superior frontal gyri and precuneus (more prominent on the right side) were observed. Second, the semantic memory condition disclosed extensive activations in the medial and orbital frontal cortex bilaterally, the left angular gyrus, and predominantly the left anterior part of the middle temporal gyri. The findings from this study are discussed in light of the available neuropsychological data obtained in brain-damaged subjects and functional neuroimaging studies.

Functional transcranial Doppler sonography as a tool in psychophysiological research

Functional transcranial Doppler sonography (fTCD) allows the noninvasive and uncomplicated registration of intracranial blood flow parameters under defined conditions of stimulation. Although local distribution patterns of regional blood perfusion can be measured with high spatial resolution through neuroimaging methods (e.g., PET or SPECT), these methods are limited by their low temporal resolution. The high temporal resolution provided by fTCD, however, allows the recording of the dynamic component of cerebral blood perfusion by continuously measuring the cerebral blood flow velocity in the basal cerebral arteries. Hence, this method is especially appropriate for the investigation of fast neuronal activation processes, which are generally accompanied by changes in local blood perfusion. In this review, we present methodical issues regarding fTCD, as well its application in the field of psychology, especially psychophysiology. The relevant studies available to date investigate processes of attention and perception, higher cognitive functions, and emotional and psychomotor processes. Considering the current state of methodology and research, fTCD can be seen to be an important complement to the other psychophysiological methods for studying brain function.

A paradox in the laterality of melody processing

Melody lateralisation has been examined extensively, using well known behavioural techniques--dichotic/monaural listening and dual tasks. The literature using these techniques has produced paradoxical results for the lateralisation of melody processing particularly with non-musicians. Research using the dichotic/monaural listening paradigm suggests right hemisphere processing for non-musicians while the dual task paradigm has suggested a left hemisphere dominance. The current study utilises both monaural listening and dual task techniques within trials. The results replicated the paradox in the literature. The dichotic/monaural listening melody measure (d') suggest right hemisphere processing of melodies for both musicians and non-musicians. In contrast, the dual task measure suggests left hemisphere processing for the non-musicians and bilateral processing for the musicians. Both measures were collected from the same stimulus presentations and are therefore paradoxical particularly for the non-musicians. Irrespective of which task participants are primarily attending, both laterality measures should produce internally consistent patterns if they are measuring the same aspects of melody processing. Although the paradox for the musicians may be resolved by postulating an attentional bias towards the tapping task, no such explanation is possible for the non-musicians. In light of the paradoxical findings produced by these two measures, their utility for providing unambiguous information about lateralisation of mental processing is questionable.

Music and cerebral hemodynamics

Previous studies performed by positron emission tomography and Transcranial Doppler (TCD) found a different cerebral activation during musical stimuli in musicians compared to non-musicians. The aim of our study is to evaluate by means of TCD, possible different pattern of cerebral activation during the performance of different musical tasks in musicians, non-musicians and lyrical singers. Our findings show a left hemispheric activation in musicians and a right one in non-musicians. Preliminary data on lyrical singers' activation patterns need further confirmation with a larger population. These data could be related to a different approach to music listening in musicians (analytical) and non-musicians who are supposed to have an emotional approach to music.

Spatial Perception and Mental Rotation Produce Gender Differences in Cerebral Hemovelocity

Abstract We sought to determine if gender differences in cerebral blood flow velocity emerge while persons performed cognitive tasks known to favor men, e.g., tests of spatial abilities. Bilateral measures were obtained simultaneously from the middle cerebral artery (VMCA) by transcranial Doppler sonography while men and women college students performed 31-s thinking tasks. Tests of spatial ability included (1) three spatial visualizing tasks (finding words among sets of letters, locating pictures hidden within a complex scene, and finding embedded geometric patterns), and (2) a mental rotation task. Two nonspatial visualizing control tasks were looking at (1) a list of words and (2) a set of pictures. Women had significantly faster global VMCAs than men during all tasks except looking at pictures. Two tasks (looking at pictures, mental rotation) produced hemispheric asymmetry (right > left) in women only. Gender differences in the number of correct responses occurred for finding words (women > men) and mental rotation (paradoxically, men > women) but not the other tests of spatial abilities. Our study shows that transcranial Doppler sonography provides noninvasive, real-time physiological indices of gender differences in spatial abilities.

Determination of language dominance: Wada test confirms functional transcranial Doppler sonography

OBJECTIVE

To determine the efficacy of the invasive Wada test in determining language dominance, and to validate the functional transcranial Doppler sonography (fTCD) examination in patients.

BACKGROUND

Previous work shows that simultaneous bilateral fTDC may identify cognitive hemispheric dominance in healthy individuals.

METHOD

fTDC and the Wada test were performed prospectively in 14 patients with various diseases (tumors, cerebrovascular events, head injury, intractable epilepsy). fTDC hemispheric dominance was determined based on the hemispheric blood flow velocity shift for language and visuospatial tasks.

RESULTS

fTDC was performed easily in patients. One patient could not be examined by fTDC because of absent temporal bone window for ultrasonic transmission. Two Wada tests were inconclusive due to patient somnolence. One of these patients suffered from right frontal tumor and had aphasia remitted under steroids when examined. fTDC indicated a bilateral language dominance. In the remaining 11 patients the correlation between fTDC and Wada language lateralization indices was 0.75 (p = 0.008). If a post hoc cutoff score was taken for the fTDC language lateralization index, in eight patients, both fTDC and Wada testing determined the left hemisphere to be dominant for language; in the other three patients, language function was bilateral in both examinations.

CONCLUSION

Although the current results are preliminary and require replication in a larger sample, fTDC seems to be able to assess hemispheric language dominance not only in healthy individuals, but also in patients. It might become an alternative noninvasive or complementary tool to the Wada test, particularly in patients in whom the Wada test is impractical or gives inconclusive results.

Cerebrovascular ultrasound

Rapid progress in noninvasive ultrasound techniques has resulted in a wide variety of clinical applications for assessment of both extracranial and intracranial arterial diseases. Recent highlights in cerebrovascular ultrasound research include imaging methods for characterization of intracranial aneurysms, use of echocontrast agents for improved evaluation of acute stroke patients and transient response harmonic imaging for depiction of brain perfusion. The important role of transcranial Doppler microembolism detection in carotid endarterectomy has been defined, new approaches to noninvasive Doppler measurement of intracranial pressure are progressing, and the clinical indications for transcranial Doppler monitoring of intracranial vasospasm to prevent secondary stroke have expanded. New functional transcranial Doppler applications, which are complementary to positron emission tomography and functional magnetic resonance imaging studies, are evolving for evaluation of functional recovery after stroke; investigation of perfusion asymmetries during complex spatial tasks; assessment of hemispheric dominance in surgical candidates for epilepsy surgery; and elucidation of temporal patterns of regional neuronal activity. With increasing sophistication of cerebrovascular ultrasound methodology, it is essential that standards for data acquisition and interpretation be established. Three recent consensus meetings have provided detailed recommendations on quantification of carotid artery stenosis, on characterization of carotid artery plaques and on microembolism detection by transcranial Doppler.

The cerebral haemodynamics of music perception. A transcranial Doppler sonography study

The perception of music has been investigated by several neurophysiological and neuroimaging methods. Results from these studies suggest a right hemisphere dominance for non-musicians and a possible left hemisphere dominance for musicians. However, inconsistent results have been obtained, and not all variables have been controlled by the different methods. We performed a study with functional transcranial Doppler sonography (fTCD) of the middle cerebral artery to evaluate changes in cerebral blood flow velocity (CBFV) during different periods of music perception. Twenty-four healthy right-handed subjects were enrolled and examined during rest and during listening to periods of music with predominant language, rhythm and harmony content. The gender, musical experience and mode of listening of the subjects were chosen as independent factors; the type of music was included as the variable in repeated measurements. We observed a significant increase of CBFV in the right hemisphere in non-musicians during harmony perception but not during rhythm perception; this effect was more pronounced in females. Language perception was lateralized to the left hemisphere in all subject groups. Musicians showed increased CBFV values in the left hemisphere which were independent of the type of stimulus, and background listeners showed increased CBFV values during harmony perception in the right hemisphere which were independent of their musical experience. The time taken to reach the peak of CBFV was significantly longer in non-musicians when compared with musicians during rhythm and harmony perception. Pulse rates were significantly decreased in non-musicians during harmony perception, probably due to a specific relaxation effect in this subgroup. The resistance index did not show any significant differences, suggesting only regional changes of small resistance vessels but not of large arteries. Our fTCD study confirms previous findings of right hemisphere lateralization for harmony perception in non-musicians. In addition, we showed that this effect is more pronounced in female subjects and in background listeners and that the lateralization is delayed in non-musicians compared with musicians for the perception of rhythm and harmony stimuli. Our data suggest that musicians and non-musicians have different strategies to lateralize musical stimuli, with a delayed but marked right hemisphere lateralization during harmony perception in non-musicians and an attentive mode of listening contributing to a left hemisphere lateralization in musicians.

Blood flow velocities in three cerebral arteries in the same subjects modulate during thinking

College students (n = 22) engaged in thinking activities while simultaneous bilateral velocity (V) measures are obtained from their middle, anterior, and posterior cerebral arteries (MCA, ACA, and PCA). The study follows a 3 x 2 x 6 factorial design with repeated measures on artery insonated (MCA, ACA, and PCA), hemisphere (right and left), and six experimental phases, within which an initial 62-second baseline (BL) period is followed by five 31-second thinking tasks (short-term remembering, generating an image, making decisions, and solving language and math problems). VMCA is faster than BL during each thinking task (range, 4.9%-8.5%; p < 0.001), but changes in VACA, VPCA, and all hemispheric differences are not significant. A stronger degree of increase is present for VMCA than (1) both VACA and VPCA during short-duration remembering, making decisions, and working math problems, and (2) VACA, which in turn is stronger than VPCA when generating images and constructing new words. The authors' study shows that transcranial Doppler neuroimaging conveniently provides physiological indices of thinking from three cerebral arteries of the same subjects.