Multiphasic Value Biases: Raw EEG Data

Raw EEG data from paper:

Corbett, Martinez-Rodriguez, Judd, O'Connell & Kelly (2022), Multiphasic Value Biases in Fast-Paced Decisions.

Perceptual decisions are biased toward higher-value options when overall  gains can be improved. When stimuli demand immediate reactions, the  neurophysiological decision process dynamically evolves through distinct  phases of growing anticipation, detection and discrimination, but how  value biases are exerted through these phases remains unknown. Here, 17 participants performed a motion direction discrimination task under high speed pressure, in which one alternative was more valuable than the other. By  parsing motor preparation dynamics in human electrophysiology, we  uncovered a multiphasic pattern of countervailing biases operating in  speeded decisions. Anticipatory preparation of higher-value actions  began earlier, conferring a “starting point”-advantage at stimulus  onset, but the delayed preparation of lower-value actions was steeper,  conferring a value-opposed buildup rate bias. This, in turn, was  countered by a transient deflection toward the higher value action  evoked by stimulus detection. 

Raw 128 channel EEG (Biosemi BDF files).

8 external channels:

1-      Above left eye

2-      Below left eye

3-      Left mastoid 

4-      Right mastoid 

5-      Left thumb EMG distal 

6-      Left thumb EMG proximal 

7-      Right thumb EMG distal 

8-      Right thumb EMG proximal

Naming convention: ParticipantRegimeBlockNo.bdf

or Participant_RegimeBlockNo.bdf

e.g. P1_H1.bdf or P29L2.bdf

Regimes: H: High coherence blocked. L: Low coherence blocked. I (or HL for P1): Interleaved.

Files with N in the filename are 'neutral' practice blocks with no value bias (not used in the analyses).

Note P22 had 2 sessions for the H and L regimes. The second of these sessions has the naming format:

P22Regime3BlockNo.bdf, 

where the '3' denotes session 3.

Task code (MATLAB/Psychtoolbox) available with the behavioural dataset.

Event trigger descriptions:

StartTask = 1

Fixation on = 4;

Cue on = [8 9 7]; % [high-on-left, high-on-right, neutral]

 Dots on = [24 25]; % [dots left dots right]

Response = [20 21]; % [left-button right-button]