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Biomedical subjects

Z Bohdanecký

Publications and source records attributed to Z Bohdanecký.

At least 19 recordsLinked to original sources
PubMed1995

Changing difficulty level in a one-dimensional tracking task and corresponding heart rate changes.

Subjects were required to track a target consisting of two vertical bars moving with either a constant or a sinusoidally modulated speed across an oscilloscope screen with a joystick-controlled light-spot. Either target size (distance between bars-size guided tasks) or velocity of the target movement (velocity guided tasks), varied throughout different tasks determined by subject's performance. The target's initial movement period was either 2 or 3 seconds. The following parameters were studied: time on-target intervals, time off-target intervals, number of tracking errors, heart rate and tracking error incidence over the cardiac cycle. Time on-target intervals were longer for the velocity guided tasks than for the size guided ones. The same was true for time off-target intervals. Values for both types of intervals decreased gradually over the fixed sequence of tasks for velocity but not for size guided tasks. Heart rate was higher in the size guided task. Tracking error incidence did not depend on the phase of cardiac cycle.

Adult↗
PubMed1994

A computerized modification of Sternberg memory test with additional perceptual distraction.

We describe a package of programs in Turbo Pascal which enables us to present six different versions of the modified Sternberg memory test and to evaluate the subject's performance. The program starts presenting a brief series of randomly generated visual stimuli (digits/colors) which are to be memorized, followed by the target stimulus. The series could either include the target or not. Noise in the form of colors or digits could be added to the stimuli. The reaction times of 'yes' or 'no' responses are evaluated separately and presented in numerical and graphic forms.

Algorithms↗
PubMed1993

EEG changes related to one-dimensional hand-tracking.

Central and occipital EEGs were recorded during one-dimensional eye-hand tracking in humans. A negative slow potential shift followed the commitment of tracking errors at electrode O1 and their correction both at O1 and C3. Error commitments were also followed by a relative decrease in alpha and beta-band power at O1, whereas their corrections followed a decrease in beta-band power at O2 and C3.

Adult↗
PubMed1991

Cardiac frequency, phase and errors in one-dimensional sensorimotor tracking.

One dimensional manual tracking was investigated in relation to actual heart rate and phase of cardiac cycle. Higher heart rate was combined with increased tracking error incidence and decreased successful tracking time (light spot inside target). Error incidence was time-locked with respect to the phase of cardiac cycle.

Electrocardiography↗
PubMed1988

Upright faces seem to have longer duration of presentation than inverted ones.

Nontemporal variables were shown to influence subjective duration. Some of these variables are known to alter recognition performance. We suggested that the ease of pattern recognition underlies the effect exerted by some nontemporal stimuli characteristics on brief duration estimation. In order to test this assumption, recognition was manipulated by presenting facial stimuli in upright and inverted position. Upright faces are known to be recognized easier than inverted ones. The results showed that the upright faces were judged to last longer than the invprted ones when presented for the same time intervals within the range of 10 to 70 ms. It was concluded that recognition performance might play an essential role in the effect of some nontemporal variables on brief duration perception.

Facial Expression↗
PubMed1987

Tracking errors related to cardiac cycle: a new approach.

One-dimensional manual tracking was investigated in relation to cardiac activity. The task of the subjects was, by means of a joy-stick, to maintain a spotlight between two vertical lines moving horizontally across an oscilloscope screen. Error incidence was time-locked with respect to the cardiac cycle. Error rate was higher for faster (2-s trial periods) than for slower (3-s trial periods) target movement. Using linear-ramp and sinusoidal movements, it was demonstrated that error incidence is associated with positive and negative cardiac acceleration.

Adult↗