The major finding of the present study is that HR subjects displayed lower theta power compared to LR participants across several comparisons (see Figs 3 and 4 and Table 4). Specifically, as shown in Fig 3, compared to the LR subjects, the HR subjects from younger male and older female subgroups showed lower theta power during loss and gain conditions, while the older HR males and younger HR females showed a decrease only during the loss condition. Further, these differences between the risk groups were more robustly displayed by male compared to female subjects. To our knowledge, this is the first study that has examined reward related ERO theta in HR subjects during a monetary gambling paradigm. This finding of lower ERO theta power during reward processing in HR subjects can be viewed in the light of previous reward related ERP studies which have reported lower amplitudes in N2 during Balloon Analogue Risk Task [24] and in P3 during a visual discrimination task [26]. As the time range of theta power (200–500 ms) used in the present study includes the
