Premotor cortex brainstem and emotional motor system Domina

Premotor cortex, brainstem and emotional motor system Domina Petric, MD

Premotor cortex includes anterior portion of precentral gyrus and posterior parts of superior, middle and inferior frontal gyri. Premotor cortex gives rise to descending projections to lower motor neurons. It is a mosaic of areas with modular organisation.

Premotor cortex, medial part �Medial division of the premotor cortex corresponds as supplementary motor area (SMA). �There is a part of medial premotor cortex that is involved in the expression of emotional behavior. �There is also a part of medial premotor cortex concerned with organising bimanual activites. �There is a division concerned with governing voluntary saccadic eye movements (frontal eye field).

Premotor cortex, lateral part �In the lateral premotor cortex are present areas that are concerned with organising movements guided by sensory information, including social interactions. �Inferior lateral part is concerned with social communication. �Broca´s area is located in the posterior inferior lateral part of the premotor cortex: this area organizes the vocal motor apparatus for production of speech.

Premotor cortex, lateral part Near the Broca´s area are parts of premotor cortex concerned with production of speech in written form.

Mirror motor neurons There is activation of mirror motor neurons when we do some movement and when we observe another person doing the same movement. Mirror motor neurons are located in lateral premotor cortex. These neurons are important in understanding the intention of some motor act.

II. BRAINSTEM UPPER MOTOR NEURONS

Vestibulospinal tracts Reticular formation extends throughout the entire brainstem. Lateral and medial vestibulospinal tract: adjustment of posture. Lateral vestibulospinal tract from lateral vestibular nuclei goes ipsilaterally and terminates in the spinal cord cell group concerned with extensor muscles tone (primarily in the lower extremities).

Vestibulospinal tracts Medial vestibulospinal tract is bilateral and terminates among medial lower motor neuronal columns, mainly found in the cervical region of the spinal cord: vestibulocervical reflexes.

Reticulospinal tract �Visceral and somatic motor control. �Mesencephalic and rostral pontine reticular formation modulates forebrain activity. �Caudal pontine and medullary reticular formation is concerned with premotor coordination of lower somatic and visceral motor neuronal pools. �Reticulospinal system is concerned primarily with making anticipatory adjustments of posture.

Superior colliculus It is a motor structure that integrates sensory information from vision, audition, pain and temperature sensation.

III. EMOTIONAL MOTOR SYSTEMS

Volitional movement: descending pyramidal and extrapyramidal projections from motor cortex and brainstem Emotional expression: descending extrapyramidal projections from limbic centers of ventro-medial forebrain and hypothalamus Lateral: fine control of distal muscles of extremities Medial: gain setting, rhythmical reflexes Medial: posture and proximal muscles of extremities Lateral: specific emotional behaviors Corticobulbar pathway Pyramidal pathway Brainstem reticular formation Motor neuron pools Motor neurons of cranial nerve nuclei and ventral horn of the spinal cord Muscle contraction and movement Autonomic preganglionic neurons Activation of smooth muscles and glands

Literature https: //www. coursera. org/learn/m edical-neuroscience/lecture: Leonard E. White, Ph. D, Duke University