How does the preparation of an eye movement alter the shape of a broad sensitivity profile at the eye movement target? And how does this affect sensitivities to single spatial frequencies on the profile? In a new paper, to appear in Cortex, we set out to provide a holistic description of pre-saccadic sensitivity modulations by characterizing them as a gradual reshaping of the sensitivity profile at the saccade target.
While previous studies measured pre-saccadic sensitivity modulations within a narrow range of spatial frequencies (SFs), and in situations in which the SF content of the saccade target was perfectly predictable, we probed sensitivities to a wide SF range from 1.0 to 5.5 cycles per degree (cpd). The features of the probe stimulus were unpredictable up until its appearance. We fitted observers’ response accuracies with a log-parabolic (i.e., inverted U-shaped) function. At an eccentricity of 10 degrees of visual angle, and long before saccade onset, the sensitivity profile peaked at 0.6 cpd and dropped off towards lower and higher SFs with broad bandwidth. During saccade preparation, the peak of the profile increased and shifted towards higher SFs while the bandwidth of the profile decreased. As a consequence of this reshaping process, and in accordance with previous findings, saccade preparation enhanced sensitivity to higher SFs more than sensitivity to lower SFs within the range of 1 to 2.5 cpd. Even higher SFs, however, profited less from saccade preparation. We conclude that the extent of pre-saccadic sensitivity enhancement to a particular SF is governed by its position on a broader sensitivity profile which reshapes substantially during saccade preparation. The shift of the profile’s peak towards higher SFs increases resolution at the saccade target even when the features of relevant visual information are unpredictable.
The paper is expected to appear soon in Cortex:
Kroell, L. M. & Rolfs, M. (2021). The peripheral sensitivity profile at the saccade target reshapes during saccade preparation, Cortex, in press. [pdf]