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Marine Mammal Physiology: Requisites for Ocean Living
Optic flow: The pattern of visual motion elicited on the retina of a moving observer.
Optokinetic eye movements: The optokinetic nystagmus is a basic motion stabilizing
reflex. During optokinetic stimulation, the eye makes a pursuit eye movement in
direction of the motion stimulus during which the external motion is ideally nullified. The pursuit eye movement is followed by a fast saccade against stimulus
direction in order to re-center the eye in the orbit.
Particle image velocimetry: Particle image velocimetry is a technique to visualize water
movements and to measure water velocities.
Path integration: Path integration describes a process during which an organism is continuously documenting distances traveled and directions taken during a trip which
provides an estimate of its current position relative to a start position and allows
integrating a homing vector which will lead the organism back to its starting point.
Pelagic prey: Prey that lives in the free water column.
Positive reinforcement: An event that increases the probability of a response to reoccur
in the future.
Primary reinforcer: A stimulus that is inherently reinforcing as it satisfies biological
needs such as hunger.
Psychometric function: A psychometric function is plotting the correct choices (mostly
in percent) as a function of the stimulus parameter that is varied during testing.
Psychophysics: Psychophysics is the discipline that links sensation and perception to
physical stimuli.
Pupil/pupillary opening: The pupil is the aperture in the iris that allows the light to enter
the eye.
Pursuit eye movements: Pursuit eye movements function to closely follow a moving object.
Random dot display: In a random dot display, a specific number of dots is displayed that
can either move completely randomly or with a certain percentage of coherence.
Retina: Photosensitive layer in the backside of the eye which transforms light into nerve
impulses.
Rhodopsin: Rhodopsin is one of the visual pigments within the photoreceptor cells of the
retina.
Rod, cone: Rods and cones are photoreceptors found within the retina that absorb photons. Rods are very sensitive and function in dim light (scotopic vision), whereas
cones are less sensitive and function in bright light (photobic vision). Usually color
vision is based on the presence of different cone types.
Saccade: A fast (up to 1000°/s) eye movement.
Secondary reinforcer: A stimulus that is associated with the primary reinforcer and thus
acquires reinforcing properties.
Staircase method/method of limits: In a staircase method, the intensity of the stimulus is decreased step by step by one unit until the experimental subject ceases to
respond correctly. At this point, the transition point, stimulus intensity is again
increased by one unit until the experimental subject starts to answer correctly.
Tapetum: Reflective layer behind the retina that reflects photons that were not absorbed
by the retina on the first passage back enabling absorption during the second passage of the retina. The tapetum thus increases the sensitivity of the eye.
Two-alternative-forced choice experiment: In a two-alternative forced choice experiment, the experimental subject has to discriminate between two stimuli. Its task
is to always choose the positive stimulus but reject/ignore the negative stimulus.
Vision: Vision is mediated by the eyes and describes an organism’s ability to process the
information contained in light.
Marine Mammal Physiology: Requisites for Ocean Living
Optic flow: The pattern of visual motion elicited on the retina of a moving observer.
Optokinetic eye movements: The optokinetic nystagmus is a basic motion stabilizing
reflex. During optokinetic stimulation, the eye makes a pursuit eye movement in
direction of the motion stimulus during which the external motion is ideally nullified. The pursuit eye movement is followed by a fast saccade against stimulus
direction in order to re-center the eye in the orbit.
Particle image velocimetry: Particle image velocimetry is a technique to visualize water
movements and to measure water velocities.
Path integration: Path integration describes a process during which an organism is continuously documenting distances traveled and directions taken during a trip which
provides an estimate of its current position relative to a start position and allows
integrating a homing vector which will lead the organism back to its starting point.
Pelagic prey: Prey that lives in the free water column.
Positive reinforcement: An event that increases the probability of a response to reoccur
in the future.
Primary reinforcer: A stimulus that is inherently reinforcing as it satisfies biological
needs such as hunger.
Psychometric function: A psychometric function is plotting the correct choices (mostly
in percent) as a function of the stimulus parameter that is varied during testing.
Psychophysics: Psychophysics is the discipline that links sensation and perception to
physical stimuli.
Pupil/pupillary opening: The pupil is the aperture in the iris that allows the light to enter
the eye.
Pursuit eye movements: Pursuit eye movements function to closely follow a moving object.
Random dot display: In a random dot display, a specific number of dots is displayed that
can either move completely randomly or with a certain percentage of coherence.
Retina: Photosensitive layer in the backside of the eye which transforms light into nerve
impulses.
Rhodopsin: Rhodopsin is one of the visual pigments within the photoreceptor cells of the
retina.
Rod, cone: Rods and cones are photoreceptors found within the retina that absorb photons. Rods are very sensitive and function in dim light (scotopic vision), whereas
cones are less sensitive and function in bright light (photobic vision). Usually color
vision is based on the presence of different cone types.
Saccade: A fast (up to 1000°/s) eye movement.
Secondary reinforcer: A stimulus that is associated with the primary reinforcer and thus
acquires reinforcing properties.
Staircase method/method of limits: In a staircase method, the intensity of the stimulus is decreased step by step by one unit until the experimental subject ceases to
respond correctly. At this point, the transition point, stimulus intensity is again
increased by one unit until the experimental subject starts to answer correctly.
Tapetum: Reflective layer behind the retina that reflects photons that were not absorbed
by the retina on the first passage back enabling absorption during the second passage of the retina. The tapetum thus increases the sensitivity of the eye.
Two-alternative-forced choice experiment: In a two-alternative forced choice experiment, the experimental subject has to discriminate between two stimuli. Its task
is to always choose the positive stimulus but reject/ignore the negative stimulus.
Vision: Vision is mediated by the eyes and describes an organism’s ability to process the
information contained in light.