The effect of presentation time on the size of the visual lobe

Abstract

Presentation time has been poorly controlled in studies on the visual lobe, due to the common opinion that a target exerts bottom-up control over the visual system with the effect that data limits are rapidly reached. The visual lobes of 4 subjects were determined with presentation times ranging between 150 and 450 msec and with a self-paced presentation time. The results showed a significant increase in lobe size as presentation time increased. The lobe size at 450 msec was about equally large as at the self-paced condition, suggesting that a data limit may be reached at that value. This result refutes a simple bottom-up sensory explanation of the lobe. Instead, it suggests a contribution of central processing, either bottom-up or top-down, which extends over time. The implications of this result for the role of the lobe while fixating during free search remain to be determined.