Task 4

Question 1

What are reflexes?

Answer 1

Automatic movements that are mediated by the brain stem. It starts as early as 25 weeks of gestation.

Question 2

What are postural reflexes?

Answer 2

• Postural reactions are not considered as true reflexes; they develop after birth & take up to 3.5 years to fully develop.
• They are “reflexes” that resist displacement of the body caused by gravity or acceleratory forces & function to maintain upright posture, restore posture if disturbed, and provide suitable postural background for performance.
• They require cortical integration of spinal cord, medulla, midbrain, cerebral cortex and cerebellum

Question 3

What are grasping reflexes?

Answer 3

Palmar (palms)
plantar(sole of feet) reflex

Question 4

What is the palmar reflex and when does it disappear?

Answer 4

Palmar reflexes are automatic closure movements of the hand when touched. They disappear between 6 to 12 months.

Question 5

What is the plantar reflex and when does it disappear?

Answer 5

Plantar reflexes are automatic flexion and adduction of the feet when touched. They also disappear between 6 to 12 months

Question 6

What is the moro reflex and when does it disappear?

Answer 6

Moro reflexes are automatic movement involving throwing back head, extended legs and arms, then pulling them back in. they are present in the 25-30 weeks gestation & disappear by 6 months postnatally.

Question 7

Why do infants have reflexes?

Answer 7

The appearance of grasping reflex in early infants are due to the insufficient control of the brain on the spinal reflex center

Question 8

Why do infants eventually lose reflexes?

Answer 8

As the infant ages & the brain matures, the reflexes disappear due to cortical control

Question 9

Lesions to certain brain regions can lead to the reappearance of the palmar grasping reflex.

Name these brain regions.

Answer 9

non-primary motor areas (e.g. frontal love, medial.lateral cortex anterior to motor area – supplementary motor area (SMA), premotor cortex, and cingulate motor cortex)

Question 10

Studies show that lesions to the non-primary motor areas, such as the Supplementary Motor Area (SMA), can lead to the reappearance of palmar reflexes.

What is the function of SMA?

Answer 10

it is involved in the control of movements

Question 11

What is the function of the cingulate motor cortex?

Answer 11

The cingulate cortex is an important interface between emotional regulation, sensing and action. It has strong reciprocal connections to the orbitofrontal cortex (OFC), the basal ganglia, and insula, and many other brain regions making it an important physical and functional interface between regions.

Question 12

One of the reasons that reflexes disappear is due to the control of the spinal reflex center by higher brain mechanisms (e.g. SMA, cingulate motor cortex).

Give another reason why reflexes disappear infants.

Answer 12

Non-primary motor areas in spinal cord are responsible for its circuitry through interneurons. Interneurons modulate spinal reflexes. Thus, as the brain matures, grasping reflexes will be replaced by voluntary grasping.

Question 13

Spastic hemilplegia/quadriplegia is a disorder caused by brain lesions. Brain lesion leads to one type of reflex being sustained.

Name this reflex

Answer 13

Plantar

Question 14

One of the characteristics of cerebral palsy is its weak palmar responses and retention of plantar reflexes.

Name the two subtypes of cerebral palsy and their associated reflexes.

Answer 14

Spastic:
Retention of Palmar reflex
No moro, galant, and assymetrical tonic neck reflexes in the 1st month of life. It appears around 1 year 6 months.

Athetoid: retention of plantar reflex

Question 15

In which disorder do we see plantar reflexes in 20 year olds?

Answer 15

Down Syndrome

Question 16

At what age can infants predict the reappearance of an occluded object that is moving linearly? What eye movements are involved?

Answer 16

4 months

They use their smooth pursuit eye tracking to track the un-occluded object. But switch to saccades when occluded

Question 17

To what extent do infants have an active role in their movement & associated development?

Answer 17

Action Perspective: Movement are goal-driven

Actions dependent on:
i. Central nervous system
ii. Dynamic interactions with environment
iii. Biometrics of the body: perception, cognition & motivation are constrained by it.
iv. Emergence of new forms of actions are dependent on multiple developments.

Development of brain mechanisms involved in action controls

Question 18

Which brain areas are involved in the representation of motion over occlusion?

Answer 18

Posterior parietal cortex, prefrontal cortex, and temporal cortex are involved in representation of motion over occlusion

Cerebellum is important for predictive motor control