Increased Volume and Function of Right Auditory Cortex as a Marker for Absolute Pitch

Absolute pitch (AP) perception is the auditory ability to effortlessly recognize the pitch of any given tone without external reference. To study the neural substrates of this rare phenomenon, we developed a novel behavioral test, which excludes memory-based interval recognition and permits quantification of AP proficiency independently of relative pitch cues. AP- and non-AP-possessing musicians were studied with morphological and functional magnetic resonance imaging (fMRI) and magnetoencephalography. Gray matter volume of the right Heschl's gyrus (HG) was highly correlated with AP proficiency. Right-hemispheric auditory evoked fields were increased in the AP group. fMRI revealed an AP-dependent network of right planum temporale, secondary somatosensory, and premotor cortices, as well as left-hemispheric "Broca's” area. We propose the right HG as an anatomical marker of AP and suggest that a right-hemispheric network mediates AP "perception,” whereas pitch "labeling” takes place in the left hemispher

Leftward Lateralization of Auditory Cortex Underlies Holistic Sound Perception in Williams Syndrome

BACKGROUND: Individuals with the rare genetic disorder Williams-Beuren syndrome (WS) are known for their characteristic auditory phenotype including strong affinity to music and sounds. In this work we attempted to pinpoint a neural substrate for the characteristic musicality in WS individuals by studying the structure-function relationship of their auditory cortex. Since WS subjects had only minor musical training due to psychomotor constraints we hypothesized that any changes compared to the control group would reflect the contribution of genetic factors to auditory processing and musicality. METHODOLOGY/PRINCIPAL FINDINGS: Using psychoacoustics, magnetoencephalography and magnetic resonance imaging, we show that WS individuals exhibit extreme and almost exclusive holistic sound perception, which stands in marked contrast to the even distribution of this trait in the general population. Functionally, this was reflected by increased amplitudes of left auditory evoked fields. On the structural level, volume of the left auditory cortex was 2.2-fold increased in WS subjects as compared to control subjects. Equivalent volumes of the auditory cortex have been previously reported for professional musicians. CONCLUSIONS/SIGNIFICANCE: There has been an ongoing debate in the neuroscience community as to whether increased gray matter of the auditory cortex in musicians is attributable to the amount of training or innate disposition. In this study musical education of WS subjects was negligible and control subjects were carefully matched for this parameter. Therefore our results not only unravel the neural substrate for this particular auditory phenotype, but in addition propose WS as a unique genetic model for training-independent auditory system properties

Increased gray matter volume of the auditory cortex and higher incidence of posterior duplications in WS subjects.

<p>(<b>a</b>) Averaged individual AC landmarks and MEG dipoles (filled circles) (<b>b</b>) Probability maps of HG including local duplications anterior to the first complete Heschl's sulcus. The number of overlapping voxels is color coded, <i>i.e.</i> red means that >80% of the brains overlapped in this voxel. (<b>a,b</b>) Plots in xy-Talairach (TAL) stereotaxic coordinates. (<b>c</b>) Morphometry of whole brain (B, light grey), grey matter (GM, medium grey), left HG (blue) and right HG (red) before and after normalization. ACPC =  plane of anterior and posterior commissure; a =  anterior; p =  posterior; r =  right; l =  left; aSTG =  anterior supratemporal gyrus; HG =  Heschl's Gyrus; D =  complete posterior HG duplication; PT =  planum temporale; B =  total brain volume; GM =  gray matter.</p

Demographic and psychoacoustic data.

<p>Sound perception: Index δ =  (<i>SP</i> - <i>H</i>)/(<i>SP</i>+<i>H</i>) according to the number of perceived holistic (<i>H</i>) and spectral (<i>SP</i>) items of the sound perception test <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012326#pone.0012326-Schneider1" target="_blank">[1]</a>. Age (years), musical expertise (hours of training per day) and sound perception index (δ) are presented as mean ± standard error (s.e.m.). ANOVA: <i>p-</i>value of WS vs. control group of spectral listeners (C<i>_SP</i>) and WS vs. control group of holistic listeners (C<i>_H</i>).</p

MEG source activity.

<p>Source activity: Dipole amplitudes of auditory evoked P50responses (nAm). Dipole localization: normalized y-coordinate in anterior-posterior direction (mm). ANOVA: <i>p-</i>value of WS vs. spectral listeners of control group (C<i>_SP</i>) and WS vs. holistic listeners of control group (C<i>_H</i>).</p

Holistic sound perception and functional leftward lateralization in WS.

<p>(<b>a</b>) Sound perception index (δ) of spectral (C<i>_SP</i>: red) and holistic listeners (C<i>_H</i>: blue) of the control group (dark colors) and the WS group (light colors). Mean δ of groups are indicated (arrows). (<b>b–d</b>) Averaged auditory evoked fields (AEFs) of three experimental groups: Left-hemispheric: blue, right-hemispheric: red traces. Peak latency in ms relative to tone onset. (<b>b</b>) Middle latency components of auditory evoked field (mAEF) modeled by one fixed dipole in each hemisphere at |x| = 45, time range 0–200 ms (<b>c–d</b>). Late auditory evoked field modeled by two fixed dipoles in each hemisphere, time range 0 – 500 ms (<b>c</b>) a primary source seeded in the first transverse Heschl's gyrus, and (<b>d</b>) a second source seeded in the posterior part of HG duplications.</p

Increased gyrification of the auditory cortex in WS.

<p>Individual segmentation reveals distinct morphology of right (red) and left (blue) auditory cortex (AC) of WS subjects. In comparison, representative AC examples of one holistic listener (C_H) and one spectral listener (C_SP) of the control group are depicted. Lateral pitch sensitive regions of the HG are highlighted and complete posterior duplications are marked (D), if present. The position of the anterior commissure is indicated as a black line. Sulcus intermedius (*); medial duplication (+).</p

Bilateral fMRI activation of the auditory cortex including posterior duplications.

<p>Group BOLD activations of WS subjects in response to auditory stimulation are projected onto one individual WS brain in (<b>a</b>) sagittal, (<b>b</b>) coronal and (<b>c</b>) transverse planes. The cross line depicts the position of left HG. (<b>d</b>) Group BOLD-activations and MEG dipoles are projected onto an individual AC surface mesh. (A =  anterior, P =  posterior, R =  right, L =  left).</p

Diagnostic benefits of presurgical fMRI in patients with brain tumours in the primary sensorimotor cortex

Reliable imaging of eloquent tumour-adjacent brain areas is necessary for planning function-preserving neurosurgery. This study evaluates the potential diagnostic benefits of presurgical functional magnetic resonance imaging (fMRI) in comparison to a detailed analysis of morphological MRI data