Biomedical subjects

P M Corballis

Publications and source records attributed to P M Corballis.

3 recordsLinked to original sources

PubMed1995

Shades of gray matter: noninvasive optical images of human brain responses during visual stimulation.

Recent theories about human brain function emphasize the need for imaging methods that allow the study of dynamic interactions among different structures. In this paper, we report on a new technique, based on the measurement of parameters of migration of near-infrared photons, that yields functional images of the human occipital cortex, combining a spatial resolution of 0.5 cm and a temporal resolution of 50 ms. This technique appears to be suitable for studying the dynamics of cortical activation.

Adult↗

PubMed1995

Removing the heart from the brain: compensation for the pulse artifact in the photon migration signal.

Various factors, including variations in the concentration of hemoglobin, determine changes in the transparency of living tissue to near-infrared light. Hence, optical measures have been proposed as a noninvasive method for investigating regional changes in brain activity. However, the amount of near-infrared light traversing a region of the head is also influenced by the periodic changes in blood pressure that occur during the cardiac cycle (pulse). These large changes may obscure smaller, localized events associated with brain activity. We developed a least-squares regression algorithm for compensating for the artifact introduced by the pulse. This procedure takes into account beat-to-beat variability in heart rate and differences in the shape of the pulse among subjects and among recording conditions.

Adult↗

PubMed1993

How apparent motion affects mental rotation: push or pull?

Subjects were timed as they judged whether a small bar perpendicular to one side of a clockhand would point left or right if the hand was pointing upward (i.e., at the 12:00 position). The clockhand was shown in two successive orientations 30 degrees apart, so that it was perceived to jump from one to the other, but the bar was included at only one of the two orientations. Analysis of reaction times as a function of angular orientation showed that the subjects "mentally rotated" the clockhand to the upright position before making their decisions. When the bar appeared on the second presentation, the jump had no significant influence on mental rotation but when it appeared on the first presentation, the estimated orientation from which the clockhand was mentally rotated was "dragged" in the direction of the jump.

Adult↗