Imaging genetics: Adventures in the dopaminergic system

Talk given as part of the "Introduction to Imaging Genetics" workshop during the 2010 Organization for Human Brain Mapping (OHBM) conference in Barcelona

Decreased Fiber Coherence

<p>Decreased fiber coherences, as observed with DTI, in persistent developmental stutterers compared with a fluent control group. A red dot indicates the peak difference in a coronal (top left), axial (top right), and a sagittal (bottom) slice.</p

Two Different Apparatuses to Prevent Stuttering

<p>On the left is a device by Gardner from 1899 to artificially add weight to the tongue (United States patent number 625,879). On the right is a more complex speech apparatus by Peate from 1912 (United States patent number 1,030,964).</p

Speech Waveforms and Sound Spectrograms of a Male Speaker Saying “PLoS Biology”

<p>The left column shows speech waveforms (amplitude as a function of time); the right column shows a time–frequency plot using a wavelet decomposition of these data. In the top row, speech is fluent; in the bottom row, stuttering typical repetitions occur at the “B” in “Biology.” Four repetitions can be clearly identified (arrows) in the spectrogram (lower right).</p

Grazer Philosophische Studien

<p><b>A.</b> Success rates (SRs) and reaction times (RTs) as a function of expectancy and Flanker compatibility. Error bars indicate standard errors of paired differences [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130492#pone.0130492.ref039" target="_blank">39</a>], computed separately for each expectancy condition. <b>B.</b> Compatibility effects for each expectancy condition, computed as ΔSR = SR_compatible-SR_incompatible and ΔRT = RT_incompatible-RT_compatible. Error bars indicate the Loftus-Masson within-subjects standard error for repeated measures ANOVA [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130492#pone.0130492.ref040" target="_blank">40</a>]. Flanker compatibility effects emerged for SRs and RTs, but these effects did not significantly differ between the three expectancy conditions and no main effect of expectancy was significant.</p

EEG time-frequency analysis.

<p>(<b>A</b>) The upper panel shows spectral power from 5 to 50 Hz averaged over all 57 scalp electrodes for the first four ratings (data for later ratings are missing for some participants, who always responded earlier), baseline corrected to the 500 ms before the first rating. The white, horizontal lines indicate the range of beta frequencies (14–30 Hz). The lower panel shows the power in the beta-band. A general negative trend in the signal and the alternation between de- and increases at every rating are clearly visible. (<b>B</b>) Position of scalp electrodes. The 37 labeled electrodes show the expected effect in the beta band (i.e., lower average signal in the first half of each rating than in the second half) at <i>p</i><.001. Note that all EEG analyses are restricted to ratings at which no response was made.</p

Illustration of the random walk models.

<p>For each of the four models, two separate simulations (light and dark gray) of the trial shown in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003309#pcbi-1003309-g001" target="_blank">Figure 1</a> are depicted using the parameter values of the subject that was closest to the group average (in terms of mean choice rating and mean RT). Green and red lines represent the thresholds for buying and rejecting, respectively. After crossing a threshold the simulation lines are dashed to show how the walk would have proceeded.</p

Model comparison based on the number of ratings.

<p>(<b>A</b>) Relative frequencies of buy (blue) and reject (red) decisions as well as model predictions of M1_standard and M1*_evidence when estimated to predict the number of acquired ratings, separately for the ratings from 1 to 6. (<b>B</b>) Average choice point in terms of rating number (x-axis) and mean RT (y-axis) per participant together with the respective predictions from the models M1_standard and M1*_evidence. Horizontal and vertical lines at the data points represent 95% confidence intervals.</p

Results of the behavioral study.

<p>(<b>A</b>) RT histograms of buy (blue) and reject (red) decisions, and the decision to sample more information (green) together with model predictions of M1*_evidence. The left panels show RTs measured from the onset of the first rating, the right panels show RTs measured from the onset of the rating at which the response was given. Note that the alternating pattern of de- and increases is washed out by the variable latency of the decision to sample more information (in contrast to the fixed duration per rating in the EEG study). (<b>B</b>) Correlation between the threshold parameter and mean RT of the decision to sample more information.</p

Time-frequency analysis and topography of hits compared to misses.

<p>(a) Time-frequency analysis of the difference between detected images (hits) compared to states of undetected images (misses) irrespective of the evoked oscillatory state (pooled over elevated and non-elevated gamma states) for electrodes PO7/PO8. The marked rectangle in the prestimulus period reveals a significant difference between both states (t(9) = 2.51, p = 0.03). No significant changes were found in the alpha (8–12 Hz) or beta band ranges (20–30 Hz). (b) Topographic representation of the prestimulus gamma band differences of detected images compared to undetected images. The maximum difference is localized in the occipital region.</p