Secondary motor area: Supplementary motor cortex

Question 1

Localization

Answer 1

• Frontal lobe: area 6 medial and superolateral part, area 24 in cingulate gyrus
• topographic representation of the body

Question 2

Characteristics

Answer 2

• agranular cortex (Betz cells)
• somatotopia (face rostral, leg caudal)
• anterior to face representation: vocalization and speech

Question 3

Function

Answer 3

• control of movement in complex skilled motor activity
• temporal organization of sequential movements
• retrieval of motor memory
• direct the primary motor area in its execution

Question 4

Afferents to supplementary motor cortex

Answer 4

• From ipsi- and contralateral primary motor cortex, premotor cortex, frontal eye field (reciprocal)
• From thalamus VLa (receives fibers from int. globus pallidus) substantia nigra
• Callosal projections from the contralateral supplementary motor cortex
• From thalamus VPS and VPL cutaneous and proprioceptive information

Question 5

Efferents from supplementary motor cortex

Answer 5

str. pyramidale - pyramidal cell axon

Corticospinal tract (contribution: 40% of tract fibers from frontal lobe) – fibers terminate on spinal interneurons

–> to primary motor cortex (str. granulosum externum II)

–> to premotor cortex - str. gran. ext. (II), to contralateral supplementary motor cortex

–> Reticular formation