Biomedical subjects

Holle Kirchner

Publications and source records attributed to Holle Kirchner.

5 recordsLinked to original sources

PubMed2006

Animals roll around the clock: the rotation invariance of ultrarapid visual processing.

The processing required to categorize faces and animals is not only rapid but also remarkably resistant to inversion. It has been suggested that this sort of categorization performance could be achieved using the global distribution of orientations within the image, which interestingly is unchanged by inversion. Here, we presented subjects with two natural scenes at 16 different orientations that were simultaneously flashed in the left and right hemifield and we asked them to make a saccade to the side containing an animal. We report that human performance is surprisingly rotation invariant as reaction times were similar and accuracy remarkably stable across orientations. The results imply that this form of rapid object detection could not depend on the global distribution of orientations within the image. One alternative is that subjects are instead using local combinations of features that are diagnostic for the presence of an animal.

Adult↗

PubMed2005

Ultra-rapid object detection with saccadic eye movements: visual processing speed revisited.

Previous ultra-rapid go/no-go categorization studies with manual responses have demonstrated the remarkable speed and efficiency with which humans process natural scenes. Using a forced-choice saccade task we show here that when two scenes are simultaneously flashed in the left and right hemifields, human participants can reliably make saccades to the side containing an animal in as little as 120 ms. Low level differences between target and distractor images were unable to account for these exceptionally fast responses. The results suggest a very fast and unexpected route linking visual processing in the ventral stream with the programming of saccadic eye movements.

Adult↗

PubMed2005

Cognitive control can modulate intersensory facilitation: speeding up visual antisaccades with an auditory distractor.

Although saccadic reaction times to a visual stimulus are facilitated if an auditory accompanying stimulus is presented at the same location, this intersensory facilitation effect (IFE) has not been explored for antisaccades (saccades directed opposite to a visual target). In this study participants were asked to make an antisaccade opposite to a point of light presented right or left of fixation while accompanied by an auditory stimulus either at the same or at the opposite location with different stimulus onset asynchronies. Antisaccade reaction times for unimodal auditory and bimodal stimuli were shorter than for unimodal visual stimulation, in line with prosaccade studies. The auditory accompanying stimulus afforded antisaccade reaction times approximately as fast as prosaccades in the direction of a visual target, especially when it was presented 40 ms before the spatially congruent visual target. Moreover, predictiveness of the target position facilitated performance only when the auditory stimulus was presented at the opposite location and 40 ms before the visual target (interstimulus contingency effect). We conclude that intersensory facilitation is a mandatory, bottom-up process, but in the particular case of a response conflict due to a visual target, IFE can be shown to be modulated by the predictability of the target location.

Acoustic Stimulation↗

PubMed2005

Interstimulus contingency facilitates saccadic responses in a bimodal go/no-go task.

The saccadic response to a suddenly appearing visual target stimulus is faster when an accessory auditory stimulus is presented in its spatiotemporal proximity. This multisensory facilitation of reaction time is usually considered a mandatory bottom-up process. Here, we report that it can be modulated by the predictability of the target location provided by an accessory stimulus, thereby indicating a form of top-down processing. Subjects were asked to make a saccade in the direction of a visual target randomly appearing left or right from fixation. An accessory auditory stimulus was presented either at the same location or opposite to the target, with the probability varying over blocks of presentation. Thus, the auditory stimulus contained probabilistic information about the target location (interstimulus contingency). A certain percentage of the trials were catch trials in which the auditory accompanying stimulus (Experiment 1) or the visual target (Experiment 2) was presented alone and the subjects were asked to withhold their response. In particular with visual catch trials, varying the predictability of target location resulted in reaction time facilitation in the bimodal trials, with both high (80%) and low predictability (20%), but only when both stimuli were presented within a small time window (40 ms). As subjects could not possibly follow the task instructions in this short period explicitly, we conclude that they utilized the interstimulus contingency information implicitly, thus revealing an extremely fast involuntary top-down control on saccadic eye movements.

Acoustic Stimulation↗

PubMed2004

Predictiveness of a visual distractor modulates saccadic responses to auditory targets.

We are faster to orient our eyes toward a visual target that also produces a sound. Conversely, the response to an auditory target is prolonged if a visual distractor is presented at a spatially incongruent position. Here, participants exhibited faster saccadic reaction times when an auditory target was more likely to be presented opposite to a visual distractor than when the stimuli only rarely occurred in spatial disparity. In contrast to experiments with visual targets and an auditory distractor, a spatially congruent visual distractor did not facilitate the response to an auditory target. We interpret the results in terms of an ocular inhibition process to suppress an automatic orienting response to the location of the visual distractor. This process is shown to be modulated by the predictability of target location.

Acoustic Stimulation↗