prenatel

• Dialect


  A regional or social variety of a language distinguished by pronunciation, grammar, or vocabulary, especially a variety of speech differing from the standard literary language or speech pattern of the culture in which it exists
• Conception marks the beginning of development
• Zygote


  A one-celled organism created when the father's sperm cell penetrates the mother's ovum (egg)
• All body cells except gametes (eggs or sperm) contain 23 pairs of chromosomes
• Gender determination


  The gender of the offspring is determined by the type of sex chromosome in the sperm that fertilizes the ovum; if it is Y bearing, the offspring will be male, and if it is X bearing, the offspring will be female
• Germinal stage

  1. Cells in the zygote divide rapidly, and the mass of cells moves slowly along the mother's fallopian tube to the uterus, where it is implanted in the uterine lining

  2. Placenta is formed during implantation
• Embryonic stage


  Most of the vital organs and body systems form
• Fetal stage

  1. Cells continue to divide, body structures become functional, and the fetus becomes capable of movement

  2. When a fetus is from 22 to 26 weeks old, it may survive if birth occurs, but chances for survival increase the closer the term is to 36 weeks
• Prenatal risks


  • Maternal malnutrition
  • Teratogens (agents or substances that can produce developmental malformations)
  • Drugs (alcohol, cocaine, marijuana, nicotine)
  • Tobacco use
• Fetal alcohol syndrome


  A complex of birth defects including retardation, lower birth weight, and distinct facial features—a flat nose, wide-set eyes, lack of an indentation on the upper lip (philtrum), and a thin upper lip
• Cocaine-exposed infant


  One who is hyperactive, so sensitive to environmental stimulation that it can't tolerate being held, and possibly retarded
• Electrooculography (EOG)


  Measurement of the movements of the eyeballs within the orbits
• Visual modality


  • Among the most important exteroceptive sensory modalities for humans
  • Visual processing is a very complex, multistep procedure
• Foveal area of the retina


  Area where the highest visual acuity can be achieved

  
• Fixation of an object of interest in the visual field


  1. Accomplished by moving the head and/or the eyes (i.e. the eyeballs within the orbits of the skull)

  2. Also called visual tracking
• Eyeball movements


  • Not completely continuous
  • Consist of minor repetitive, involuntary, quick movements called microsaccades
  • Overall activity can be controlled voluntarily
• Extrinsic eye muscles


  Six tiny striated muscles that move the eyeball within the orbit
• Movements of the two eyeballs


  Synchronized to provide the brain with two, only slightly different images of the visual field (requirement of stereo vision)
• Neural impulses to eye muscles


  • Reach through cranial nerves VI, IV, and III
  • Motor centers located in the frontal lobe of the cortex and in the brainstem

  
• Human eyeball


  A dipole with the positive terminal in front of the cornea and the negative terminal behind the retina

  
• Potential between eyeball terminals


  Approximately 0.4-1.0 mV, generated by the hyperpolarizations and depolarizations of the nerve cells in the retina

  
• Measurement of EOG

  1. Pairs of electrodes placed on the temporal side of the two orbits (to measure horizontal movements) and above and below the right eye (for vertical movements)

  2. Eyeball movement induces a positive or negative change in voltage proportional to the movement
• EOG signal


  • Linearly proportional to the movement (approx. 20 mV/degree)
  • Typical accuracy 1.5-2°
  • Measurable range up to ±70° both vertically and horizontally
  • Frequency domain of interest 0-15 Hz if only direction of gaze is to be determined
  • Slowly returns to baseline (zero) in several minutes under constant fixation
  • Movement of facial muscles and/or the jaw can introduce artefacts and additional noise
• Classic EOG method is rarely used today if determination of direction of gaze is the major goal
• Pupillography


  Assessment of the changes of size of the pupils, under the control of the autonomous nervous system
• Pupil changes


  1. Sympathetic activation dilates the pupils, parasympathetic activation constricts the pupils

  2. Recorded by analogue and digital photographing and television scanning
• Task evoked pupillary response


  Change in the diameter of the pupils in response to a stimulus
• Startle response or startle reflex


  Eye blink in response to a sudden unexpected stimulus, assessed via EMG
• Electrooculography (EOG)


  Measurement of the movements of the eyeballs within the orbits
• Visual modality


  • Among the most important exteroceptive sensory modalities for humans
  • Visual processing is a very complex, multistep procedure
• Foveal area of the retina


  Area where the highest visual acuity can be achieved

  
• Fixation of an object of interest in the visual field


  1. Accomplished by moving the head and/or the eyes (i.e. the eyeballs within the orbits of the skull)

  2. Also called visual tracking

  
• Eyeball movements


  • Not completely continuous
  • Consist of minor repetitive, involuntary, quick movements called microsaccades
  • Overall activity can be controlled voluntarily
• Extrinsic eye muscles


  Six tiny striated muscles that move the eyeball within the orbit

  
• Movements of the two eyeballs


  Synchronized to provide the brain with two, only slightly different images of the visual field (requirement of stereo vision)

  
• Neural impulses to eye muscles


  • Reach through cranial nerves VI, IV, and III
  • Motor centers located in the frontal lobe of the cortex and in the brainstem

  
• Human eyeball


  A dipole with the positive terminal in front of the cornea and the negative terminal behind the retina
• Potential between eyeball terminals


  Approximately 0.4-1.0 mV, generated by the hyperpolarizations and depolarizations of the nerve cells in the retina

  
• Measurement of EOG


  1. Pairs of electrodes placed on the temporal side of the two orbits (to measure horizontal movements) and above and below the right eye (for vertical movements)

  2. Eyeball movement induces a positive or negative change in voltage proportional to the movement
• EOG signal


  • Linearly proportional to the movement (approx. 20 mV/degree)
  • Typical accuracy 1.5-2°
  • Measurable range up to ±70° both vertically and horizontally
  • Frequency domain of interest 0-15 Hz if only direction of gaze is to be determined
  • Slowly returns to baseline (zero) in several minutes under constant fixation
  • Movement of facial muscles and/or the jaw can introduce artefacts and additional noise