Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Tommaso Tosato (Donders Series 613)

6 June 2023

Promotor: prof. dr. P. Fries
Copromotor: dr. G. Rohenkohl (Universidade de São Paulo, Brazilië)

Quantifying and testing for phase-locking in behavioral reports

Rhythmic modulations of cognitive processes, such as perception, attention, decision-making, and movement, have been a subject of intense research. These rhythms are believed to reflect the dynamics of neural processing and to coordinate sensory and motor functions.
This thesis primarily focuses on the analysis methods and statistical testing used in this field of research. To compare the performance of different methods, datasets are simulated based on a plausible model, which produces data resembling actual psychophysical experiments. The sensitivity, specificity, and D-prime of each method are quantified, enabling direct method comparison. The importance of correctly interpreting the spectrum for inferring periodicity and distinguishing between periodic and aperiodic modulations is highlighted. Additionally, the potential for certain preprocessing steps to introduce distortions in the spectra is discussed.
The thesis also presents empirical data resulting from a psychophysical experiment testing for modulations of visual detection accuracy phase-locked to a button press. The results reveal a significant 17 Hz modulation in specific subsets of trials and participants, suggesting that the button press resets a 17 Hz brain rhythm that only transpires in behavior during specific internal states of the participants (characterized, for example, by lower attentional engagement or a more conservative decision criterion).
In conclusion, this thesis provides insights into the detection and characterization of phase-locked modulations in behavioral reports and emphasizes the importance of proper methodology for advancing our understanding.