Introduction To Cortical Control Of Motor Function PDF

OCC313 Biomedical Science Topic 3 INTRODUCTION TO CORTICAL CONTROL OF MOTOR FUNCTION Dr.Safaa Elkholi The Cerebrum is divided by a longitudinal fissure into 2 hemispheres, each containing 4 discrete lobes. (see slides following) The frontal, temporal, parietal, and occipit...

OCC313 Biomedical Science Topic 3 INTRODUCTION TO CORTICAL CONTROL OF MOTOR FUNCTION Dr.Safaa Elkholi The Cerebrum is divided by a longitudinal fissure into 2 hemispheres, each containing 4 discrete lobes. (see slides following) The frontal, temporal, parietal, and occipital lobes cover the brain's surface; the insula sometimes described as a 5 lobe th is hidden under the Sylvian fissure Cerebral Lobes: Areas of the brain Broca's area is a part of the cerebral cortex that helps to ensure that language is produced in a fluent way, while Wernicke's area is a part of the cerebral cortex that makes sure the language makes sense Although specific functions are attributed to each lobe, most activities require coordination of multiple areas in both hemispheres. – For example, although the occipital lobe is essential to visual processing, parts of the parietal, temporal, and frontal lobes on both sides also process complex visual stimuli. ▪Function is extensively lateralized.  Visual, tactile, and motor activities of the left side of the body are directed predominantly by the right hemisphere and vice versa. ▪Certain complex functions involve both hemispheres but are directed predominantly by one (cerebral dominance).  For example, the left hemisphere is typically dominant for language, and the right is dominant for spatial attention. Longitudinal fissure The cerebral cortex contains the primary sensory and motor areas as well as multiple association areas. The primary sensory areas receive somesthetic, auditory, visual, olfactory, and gustatory stimuli from specialized sensory organs and peripheral receptors. Cerebral cortex Functions: site of intellect, memory, language higher functions (e.g. intellect, language, memory) appear to be spread across several cortical areas there may be some specialization of functions, e.g. language, in one or other hemisphere (lateralization) motor areas control voluntary movements (skeletal muscles)  Motor Areas Primary motor cortex is in precentral gyrus of each hemisphere in posterior portion of frontal lobe. Here are the cell bodies of upper motor neurons of voluntary motor pathways. A chain of neurons conveys impulses (i.e. instructions) from motor cortex to skeletal muscles. Pathway crosses from one side to the other (decussates) in medulla: thus L motor cortex controls activity of R arm, leg. Skeletal muscles of each part of the body are controlled by a specific part of the motor cortex (on opposite side of body). Damage to motor cortex → loss of voluntary movement in corresponding, contralateral part of body. Sensory areas register sensations, and interpret them together with: sensory association areas. These put together data from different sources, interpret them in the light of experience in order to determine response. Each hemisphere is mainly concerned with the motor and sensory functions of opposite side of body. Most motor fibres decussate on their way down from the motor cortex and most sensory pathways decussate on their way up to the sensory cortex. Sensory stimuli are further processed in association areas that relate to one or more senses. The primary motor cortex generates volitional body movements; motor association areas help plan and execute complex motor activity. Specific parts of the cortex control specific motor and sensory functions on the contralateral side of the body. The amount of cortical space given to a body part varies; eg, the area of the cortex that controls the hand is larger than the area that controls the shoulder. The map of these parts is called the homunculus (“little person”). Motor Homunculus Frontal lobes: Reminder The frontal lobes are anterior to the central sulcus. They are essential for planning and executing learned and purposeful behaviors; they are also the site of many inhibitory functions. There are several functionally distinct areas in the frontal lobes: – The primary motor cortex is the most posterior part of the precentral gyrus. – The primary motor cortex on one side controls all moving parts on the contralateral side of the body – 90% of motor fibers from each hemisphere cross the midline in the brain stem. – Thus, damage to the motor cortex of one hemisphere causes weakness or paralysis mainly on the contralateral side of the body. Cerebellum Second largest part of brain. Located behind brainstem, and below occipital lobes of cerebrum. Controls subconscious skeletal muscle contractions required for smooth coordinated movements and balance: voluntary motor activity is initiated in motor cortex of cerebrum cerebellum receives this information, i.e. it “knows” what voluntary muscles “should be doing” sensory information related to movement travels into CNS from periphery and ascends spinal cord toward sensory areas of cortex... cerebellum also receives this information, i.e. it “knows” what voluntary muscles are “actually doing” by comparing the two sets of information, cerebellum ensures that movement occurs smoothly if muscles are not behaving as they “should be”, i.e. movement is not smooth, cerebellum informs cerebrum, which adjusts output of motor cortex accordingly Damage to cerebellum leads to uncoordinated movements. Spinal cord tracts Brodmann’s areas Function Brodmann Area Vision Primary 17 Secondary 18,19,20,21,37 Auditory Primary 41 Secondary 22,42 Body Senses Primary 1,2,3 Secondary 5,7 Sensory, tertiary 7,22,37,39,49 Motor Primary 4 Secondary 6 Eye movement 8 Speech 44 Motor, tertiary 9,10,11,45,46,47 SENSORY PATHWAYS: TRANSMITTING SOMATIC SIGNALS INTO THE CNS Dorsal column: Medial lemniscal system Anterolateral system PROJECTION OF DORSAL COLUMN-MLS TO THE SOMATOSENSORY CORTEX  Discriminates shape, texture, Discriminates among head or size of objects positions and head movements Distinguishes intensity of light, shape, size and location of objects Conscious discrimination of loudness and pitch of sounds Cortical Area Function Somatosensory association Stereognosis and memory of the tactile and spatial Visual association Analysis of motion, color, control of visual fixation Auditory association Classification of sounds  Primary Motor Cortex and Motor Planning Areas of the Cerebral Cortex Young children develops the primary motor cortex in the sensorimotor stage 1. Primary Motor Cortex FUNCTIONAL ORGANIZATION OF THE PRIMARY MOTOR CORTEX  Voluntarily controlled movements Initiation of movement Orientation planning Bimanual and sequential movements Control of trunk and girdle muscles Motor programming of speech Anticipatory postural adjustments (usually in left hemisphere only) Area analogous to Broca’s in opposite hemisphere: Planning nonverbal communication (emotional gestures, tone of voice, usually in the right hemisphere)  Traumatic Brain Injuries Focal Injury Coup/Counter coup Injury Diffuse Axonal injury  https://www.youtube.com/watch?v=tgChTe ALF7g There is a strong link between degenerative brain disease and serious head trauma, suggests a study, published in the journal Brain. According to the data, 80 per cent of men in the test group, all of whom played sports, exhibited symptoms of chronic traumatic encephalopathy (CTE), a degenerative brain disease which can cause depression, dementia, and memory loss. McKee AC, Stein TD, Nowinski CJ, Stern RA, Daneshvar DH, Alvarez VE, Lee H -S, Hall GF, Wojtowicz SM, Baugh CM, Riley DO, Kubilus CA, Cormier KA, Jacobs MA, Martin BR, Abraham CR, Ikezu T, Reichard RR, Wolozin BL, Budson AE, Goldstein LE, Kowall NW, Cantu RC. “The Spectrum of Disease in Chronic Traumatic Encephalopathy,” Brain, 2012. The BU Center for the Study of Traumatic Encephalopathy notes CTE is caused when brain trauma triggers degeneration of brain tissue and a build-up of the protein called tau. Changes can be found months, years, or even decades after the injury occurred.  GLASGOW COMA SCALE The Glasgow Coma Scale is the most widely used scoring system used in quantifying level of consciousness following traumatic brain injury. Simple Relatively high degree of inter-rater reliability Correlates well with outcome following severe brain injury.  Glasgow Coma Score Eye Opening (E) Verbal Response (V) Motor Response (M) 4=Spontane 5=Normal 6=Normal ous conversation 5=Localizes to 3=To voice 4=Disoriented pain 2=To pain conversation 4=Withdraws 1=None 3=Words, but not to pain coherent 3=Decorticate 2=No posture words......only 2=Decerebrate sounds 1=None 1=None https://www.youtube.com/watch?v=v6qpE QxJQO4 Total = E+V+M Limitations of GLASGOW COMA SCALE Endotracheal tube Other factors which alter the patients level of consciousness interfere with the scale's ability to accurately reflect the severity of a traumatic brain injury. Shock Hypoxemia Drug use Alcohol intoxication Metabolic disturbances  Post Traumatic Amnesia (PTA) PTA is a condition in which the person with a brain injury is unable to store or retrieve new information. Persons in PTA may demonstrate: Disorientation Impaired attention Memory failure for day-to-day events Illusions Misidentification of family, friends and medical staff Agitation Poor social skills Impulsiveness  Post Traumatic Amnesia (PTA) The duration of PTA appears to be a sensitive and reliable index of severity of head injury. The longer the PTA The stronger the probability of extensive damage https://www.youtube.com/watch?v=nalhhZ hYYY0  Epilepsy What is a seizure? A seizure is a sudden surge of electrical activity in the brain that usually affects how a person feels or acts for a short time. Auditory hallucination Pins and needles for a few seconds Blanking out for a few seconds Muscle twitch a few times  Types of seizure Generalized seizures (begin with an electrical discharge that involves both sides of the brain at once.) Tonic-clonic seizure https://www.youtube.com/watch?v=OcJOQQvieR8 Tonic seizure Atonic seizure Myoclonic seizure Absence seizure Partial seizures (begin with an electrical discharge from a limited area.) Simple partial seizure Complex partial seizure https://www.youtube.com/watch?v=gUzTE_sG2e Q Simple partial seizur From the diagram A simple partial seizure with motor symptoms. here the neuronal discharge begins in the motor strip in the right hemisphere of the brain, affecting first one muscle then another on the left side of the body as it spreads. In…  – (a) first the fingers then the hand and arm are jerking, in – (b) it has spread to the upper shoulder. in – (c) the woman's head is drawn towards her shoulder. in – (d) the leg is drawn up. the woman remains conscious – But unable to prevent her muscles' response to the excessive stimulation they are receiving from her brain. https://www.youtube.com/watch?v=j JWfHHqfSbk