EEG_bisection

Electrophysiological signatures of temporal context in the bisection task

Cemre Baykan, Xiuna Zhu, Artyom Zinchenko, Hermann J. Müller, Zhuanghua Shi

General and Experimental Psychology, LMU Munich

Background

Despite relatively accurate time judgment, subjective time is susceptible to various contexts, such as sample spacing and frequency. Several electroencephalographic (EEG) components have been linked to timing, including the contingent negative variation (CNV), offset P2, and late positive component of timing (LPCt). However, the specific role of these components in the contextual modulation of perceived time remains unclear. In this study, we conducted two temporal bisection experiments, where participants had to judge if a test duration was close to a short or long standard. Unbeknownst to participants, the sample spacing (Experiment 1) and frequency (Experiment 2) were altered to create short and long contexts while keeping the test range and standards the same in different sessions. The results showed that the bisection threshold shifted toward the ensemble mean and that CNV and LPCt were sensitive to context modulation. Compared to the long context, the CNV climbing rate increased in the short context, and the amplitude and latency of the LPCt were reduced. These findings suggest the CNV represents an expectancy wave for upcoming decision-making, while LPCt reflects the decision-making process, both influenced by the temporal context.

Experimental design

Each trial started with a visual fixation marker and a brief beep (20 ms, 1000 Hz, 60 dB), followed by a blank display of 500 ms, prompting participants to get ready for a new trial. Next, a white-noise stimulus (60 dB) was presented for a given duration randomly selected from experimental stimulus sets. In Experiment 1, immeadiately after the sound presentation, a question mark was shown to prompt participants to respond, while in Experiment 2, there was 300 ms blank between the sound offset and the question mark presentation. At the question mark display, participants were asked to press the right and left arrow keys on the keyboard using two index fingers to respond if the presented stimulus was “short” or “long”.

Using the same temporal bisection experimental design, we carried out two experiments. In both experiments, participants had both short and long context sessions.

Data and Analysis Code Folder Structure

1. /Experiment 1: raw EEG data of Experiment 1 participants
2. /Experiment 2: raw EEG data of Experiment 2 participants
3. /derivates:
   "Behavioral_analysis.Rmd" contains behavioral data analyses,
   "EEG_analysis.Rmd" contains ERP analyses.
   • /data:
     "allData_exp1_beh.csv" contains behavioral data of Exp.1 participants
     "allData_exp2_beh.csv" contains behavioral data of Exp.2 participants
     "allAverageDat_cnv_exp1.csv" contains CNV data of Exp.1
     "allAverageDat_cnv_exp2.csv" contains CNV data of Exp.2
     "allAverageDat_pos_exp1.csv" contains offset positivity data of Exp.1
     "allAverageDat_pos_exp2.csv" contains offset positivity data of Exp.2
     "peak_negative_cnv_exp1.csv" contains CNV peaks data of Exp.1
     "peak_negative_cnv_exp2.csv" contains CNV peaks data of Exp.2
     "peak_positive_offset_exp1.csv" contains offset positivity peaks data of Exp.1
     "peak_positive_offset_exp2.csv" contains offset positivity peaks data of Exp.2
     "width_CNV_exp1.csv" contains CNV end points data of Exp.1
     "width_CNV_exp2.csv" contains CNV end points data of Exp.2
   • /figures: stored figures used in the paper