Beyond the Peak – Tactile Temporal Discrimination Does Not Correlate with Individual Peak Frequencies in Somatosensory Cortex

Abstract

The human sensory systems constantly receive input from different stimuli. Whether these stimuli are integrated into a coherent percept or segregated and perceived as separate events, is critically determined by the temporal distance of the stimuli. This temporal distance has prompted the concept of temporal integration windows or perceptual cycles. Although this concept has gained considerable support, the neuronal correlates are still discussed. Studies suggested that neuronal oscillations might provide a neuronal basis for such perceptual cycles, i.e., the cycle lengths of alpha oscillations in visual cortex and beta oscillations in somatosensory cortex might determine the length of perceptual cycles. Specifically, recent studies reported that the peak frequency (the frequency with the highest spectral power) of alpha oscillations in visual cortex correlates with subjects’ ability to discriminate two visual stimuli. In the present study, we investigated whether peak frequencies in somatosensory cortex might serve as the correlate of perceptual cycles in tactile discrimination. Despite several different approaches, we were unable to find a significant correlation between individual peak frequencies in the alpha- and beta-band and individual discrimination abilities. In addition, analysis of Bayes factor provided evidence that peak frequencies and discrimination thresholds are unrelated. The results suggest that perceptual cycles in the somatosensory domain are not necessarily to be found in the peak frequency, but in other frequencies. We argue that studies based solely on analysis of peak frequencies might thus miss relevant information.

EEG Alpha Power Predicts the Temporal Sensitivity of Multisensory Integration

“…In our task, the temporal factor is explicitly probed and a discriminatory response is required. Similar to our results, in the same tactile temporal discrimination task as described above (Baumgarten et al, 2016), this relationship was absent across participants (Baumgarten et al, 2017) despite a within-participant relationship between alpha frequency and temporal sensitivity (Baumgarten et al, 2016). One reason this relationship was absent in our data could be that the TOJ task is a much harder and cognitively demanding task than the sound-induced flash illusion used by Cecere et al (2015) and Keil & Senkowski (2017).…”

No changes in parieto‐occipital alpha during neural phase locking to visual quasi‐periodic theta‐, alpha‐, and beta‐band stimulation

“…Further, considering that our stimulation was only quasi‐rhythmic, i.e., occurred within a band around but not at the centre frequency may have weakened a pull effect additionally. Work on the role of intrinsic rhythms in tactile perception has led to the argument that focussing on individual peak frequencies only may neglect effects on rhythmic activity beyond the peak (Baumgarten, Schnitzler, & Lange, ). Also note that the EEG is likely dominated by a strong parieto‐occipital alpha generator.…”

No changes in parieto-occipital alpha during neural phase locking to visual quasi-periodic theta-, alpha-, and beta-band stimulation

“…occurred within a band around but not at the centre frequency may have weakened a pull effect additionally. Lastly, work on the role of intrinsic rhythms in tactile perception has led to the argument that focussing on individual peak frequencies only may neglect effects on rhythmic activity beyond the peak (Baumgarten et al, 2017). Also note that the EEG is likely dominated by a strong parieto-occipital alpha generator.…”