Figure 6.

Spike-Field Phase Relationship for the Gamma Range as a Function of Contrast and Attention

Each recording site contributes three vectors, obtained from three different parts of the gamma frequency band (36–40, 40–44, and 44–48 Hz). The reason for this is that the phase angle from the three frequency bands cannot be averaged (a random phase angle would average to 0). Columns show different attention conditions; rows, different stimulus conditions. During spontaneous activity no specific angle for the spike-field phase relationship was apparent. Upon stimulus presentation spike-field phase relationships concentrated at ∼−0.65π. Attention had no significant influence on the median spike-field phase relationship. The red vector and number insets give the median spike-field phase relationship.