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The right human auditory cortex is predominantly involved in the discrimination of the direction of frequency modulated tones
NemoImage
11, Number
5, 2000,
Part 2 of 2 Parts ID
E bL@
PHYSIOLOGY
The Right Human Auditory Cortex is Predominantly Involved in the Discrimination of the Direction of Frequency Modulated Tones Andre Bmchmann,
Henning Scheich
Leibniz Institue for Neurobiology Magdeburg, Brenneckestr. 6, 39118 Magdeburg, Germany Introduction Frequency modulation (FM) is a common feature of acoustic communication signals in many animals and humans. are critical in determining the communicative function of monkey calls (1) and seem to be important elements of (“pitch contour”) (2). Furthermore, lesion studies on animals show that the right but not the left auditory cortex discriminate the direction of FM (3). We investigated the activation of the auditory cortex during discrimination of FM as an important distinctive feature of prosodies in humans. Material
FM components human prosody is necessary to of the direction
& Methods
17 right-handed subjects with normal hearing were scanned in a BRUKER BIOSPEC 3T system. Upward and downward linear FM each covering half an octave were presented in a block design experiment using fMRI compatible electrodynamic headphones (4). Blocks of high (5 to 10 kHz) and low frequencies (0.1 to 3 kHz) alternated with silence. During the first scan subjects had to listen to the stimuli passively, whereas during the second scan of the same session they had to discriminate upward and downward FM. 4 slices (8 mm) were positioned parallel to the sylvian fissure covering the superior temporal plane in both hemispheres. 80 functional images for each slice were collected using a low noise conventional gradient echo sequence (SPL, 58dBA; TE, 30.7 ms; TR, 167 ms; flip angle, 15’) with an in-plane resolution of (2.8*2.8mm*) within 12 min. Auditory cortex territories were defined as regions of interest as described in Scheich et al. (5).
Compared to the passive listening condition, the activation strength during discrimination of FM direction was significantly larger in the right hemisphere. These differences were mainly based on auditory cortex territories T3 (planum temporale) and T2 (secondary auditory cortex) for both low and high center frequencies and Tlb (comprising primary auditory cortex) for low center frequencies (Fig. 1). Furthermore, activation strength of the right hemisphere correlated negatively with the performance in the discrimination condition. Discussion Clinical studies on patients with left and right hemispheric lesions suggest that intact right hemispheric brain regions corresponding to classical speech regions of the left hemisphere are required for the production and comprehension of prosody (2, 6j. The results of the present study suggest a dominant role of the right hemisphere in discriminating FM direction. As FM is an important distinctive feature in prosodies the specialization of the right hemisphere in FM directional discrimination might be a basis for prosody comprehension. References 1. 2. 3. 4. 5. 6.
Moody, D. B. et al. (1986). Exp Biol. 45: 219-232. Ackermann, H. et al. (1993). Fortsch. Neurol. Psychiatr. Ohl, F. W. et al. (1999). Learn. Mem. 6: 347-362. Baumgart, F. et al. (1998). Med. Phys. 25: 2068-2070. Scheich, H. et al. (1998). Eur. J. Neurosci. 10: 803-809. Joanette, Y. et al. (1990). Right Hemisphere and Verbal
61: 241-253.
Communication,
s799
Springer,
p 132-160.
11, Number
5, 2000,
Part 2 of 2 Parts ID
E bL@
PHYSIOLOGY
The Right Human Auditory Cortex is Predominantly Involved in the Discrimination of the Direction of Frequency Modulated Tones Andre Bmchmann,
Henning Scheich
Leibniz Institue for Neurobiology Magdeburg, Brenneckestr. 6, 39118 Magdeburg, Germany Introduction Frequency modulation (FM) is a common feature of acoustic communication signals in many animals and humans. are critical in determining the communicative function of monkey calls (1) and seem to be important elements of (“pitch contour”) (2). Furthermore, lesion studies on animals show that the right but not the left auditory cortex discriminate the direction of FM (3). We investigated the activation of the auditory cortex during discrimination of FM as an important distinctive feature of prosodies in humans. Material
FM components human prosody is necessary to of the direction
& Methods
17 right-handed subjects with normal hearing were scanned in a BRUKER BIOSPEC 3T system. Upward and downward linear FM each covering half an octave were presented in a block design experiment using fMRI compatible electrodynamic headphones (4). Blocks of high (5 to 10 kHz) and low frequencies (0.1 to 3 kHz) alternated with silence. During the first scan subjects had to listen to the stimuli passively, whereas during the second scan of the same session they had to discriminate upward and downward FM. 4 slices (8 mm) were positioned parallel to the sylvian fissure covering the superior temporal plane in both hemispheres. 80 functional images for each slice were collected using a low noise conventional gradient echo sequence (SPL, 58dBA; TE, 30.7 ms; TR, 167 ms; flip angle, 15’) with an in-plane resolution of (2.8*2.8mm*) within 12 min. Auditory cortex territories were defined as regions of interest as described in Scheich et al. (5).
Compared to the passive listening condition, the activation strength during discrimination of FM direction was significantly larger in the right hemisphere. These differences were mainly based on auditory cortex territories T3 (planum temporale) and T2 (secondary auditory cortex) for both low and high center frequencies and Tlb (comprising primary auditory cortex) for low center frequencies (Fig. 1). Furthermore, activation strength of the right hemisphere correlated negatively with the performance in the discrimination condition. Discussion Clinical studies on patients with left and right hemispheric lesions suggest that intact right hemispheric brain regions corresponding to classical speech regions of the left hemisphere are required for the production and comprehension of prosody (2, 6j. The results of the present study suggest a dominant role of the right hemisphere in discriminating FM direction. As FM is an important distinctive feature in prosodies the specialization of the right hemisphere in FM directional discrimination might be a basis for prosody comprehension. References 1. 2. 3. 4. 5. 6.
Moody, D. B. et al. (1986). Exp Biol. 45: 219-232. Ackermann, H. et al. (1993). Fortsch. Neurol. Psychiatr. Ohl, F. W. et al. (1999). Learn. Mem. 6: 347-362. Baumgart, F. et al. (1998). Med. Phys. 25: 2068-2070. Scheich, H. et al. (1998). Eur. J. Neurosci. 10: 803-809. Joanette, Y. et al. (1990). Right Hemisphere and Verbal
61: 241-253.
Communication,
s799
Springer,
p 132-160.