Textbook Notes (363,508)
Canada (158,391)
Psychology (1,390)
PSYC 211 (154)
Chapter 8

Chapter 8 Notes.docx

9 Pages
Unlock Document

McGill University
PSYC 211
Yogita Chudasama

Chapter 8: Control of Movement Notes taken by: Ashley Brown Contact for mistakes: [email protected] Control of Movement by the Brain: Movement can be initiated many ways such as different reflexes (rapid stretch of muscle triggering monosynaptic stretch reflex, stumble triggering righting reflexes, etc.) or a stimuli initiated a learned sequence of movements aka there is no single starting point for neural mechanisms that control movement - several different motor systems that can operate at the same time Organization of the Motor Cortex Primary motor cortex lies on precentral gyrus which is just rostral to the central sulcus - when neurons from this region are activated causes movements of particular parts of the body - shows somatotopic organization aka topographically organized mapping of parts of the body that are represented in a particular region of the brain o Found by Penfield and Rasmussen o Lots of space for fingers and parts involving speech - commands for movement originate here and are assisted and modified by the basal ganglia and cerebellum - brief stimulation causes brief movements and prolonged stimulation causes more complex movements Principal cortical input to the primary motor cortex is the frontal association cortex which is located rostral to it Both the supplementary motor area and the premotor cortex which are just rostral to the primary motor cortex are especially important in the control of movement because they receive sensory information from the parietal and temporal lobs and then send efferent axons to it - Supplementary motor area (SMA) is located on the medial surface of the brain o Involved in learning sequences of movements o The pre-SMA which is just rostral to the SMA is though to be involved in the desire to move - The premotor cortex is on the lateral surface of the brain The axons between the primary somatosensory cortex and primary motor cortex basically trade - e.g. somatosensory neurons that respond to a touch on the back of the thumb send axons to motor neurons that cause thumb extension and the ones that respond to touch on the ball of the thumb send axons to motor neurons that correspond to thumb flexion - this enables rapid feedback Cortical Control of Movement: The Descending Pathways Neurons in the primary motor cortex control movements by 2 groups of descending tracts - Lateral Group includes the corticospinal tract, the corticobulbar tract, the rubrospinal tract o Primarily involved in control of independent limb movements, particularly those of hands and fingers - Ventromedial Group includes the vestibulospinal tract, the tectospinal tract, the reticulospinal tract, and the ventral corticospinal tract o Control more automatic movements: gross movements of the muscles of the trunk and coordinated trunk and limb movements involved in posture and locomotion Planning and Initiating Movements: Role of the Motor Association Cortex The SMA and premotor cortex are involved in planning of movements and they execute them through their connections with the primary motor cortex. - show activation when executing sequences - also involved in imitating the actions of others and further, understanding the functions of other people’s behaviors - both receive info from association areas of the parietal and temporal cortex (about what is happening and where it is happening) The Supplementary Motor Area The SMA plays a critical role in behavioral sequences - damage disrupts the ability to execute well learned sequences of reponses - Every single study basically says they can still do the individual movements but they can’t do the previously learned sequence when the SMA is damaged, o humans have like a second of sequence still working after damage though (monkeys don’t) o SMA involved in planning of the elements yet to come in the sequences of movements not the actual execution The pre-SMA which is just rostral to the SMA appears to be involved in control of spontaneous movement or at least in perception of control and thought to be involved in the desire to move Most important input to the SMA comes from the parietal lobe - information from here permits the pre-SMA to detect that a decision to move has been made Lesions of the prefrontal cortex disrupt people’s plan for voluntary action - they will react to events but show deficits in initiating behavior, suggesting prefrontal cortex is important source in those decisions The Premotor Cortex  involved in learning and executing complex movements that are guided by sensory information - Studies show that premotor cortex is involved in using arbitrary stimuli to indicate what movement should be made or information that is not directly related to the movement that it signals (like with language, when someone says chair we can point to chair, same as with someone said “une chaise” we would still point to the chair) o One with monkeys showed that when they had a lesion to the premotor cortex they could move their hand toward nonarbitrary stimuli like a light but previously learned left and right movements to arbitrary green and red lights Imitating and Comprehending Movements: Role of the Mirror Neuron System Mirror neurons are located in the ventral premotor cortex and inferior parietal lobule (IPL) that respond when the individual makes a particular movement or sees another individual making that movement - play a role in the ability to imitate another’s movements - activated when both watching and imitating movements - also activated by sounds that indicate the occurrence of a familiar action o audiovisual neurons respond to the sounds of particular actions and to the sight of those actions  reminds animal of the action the sound represents. This interaction works both ways and is very quick. - help us understand the actions of other because activation of motor neurons gives rise to the recognition of the action, aka their intentions o one study found that mirror neurons not only encode the action but the intent of that action Control of Reaching and Grasping A lot of behavior involves interacting with objects in our environment, much of which involve reaching for something and doing something with it. Two main types of these interactions: (1) reaching and (2) grasping. - different brain mechanism are involved in these two actions Reaching - Mostly controlled by vision - Connections b/t the parietal lobe (endpoint of dorsal stream) and the frontal lobe play a critical role - Parietal reach region: a region in the medial posterior parietal cortex that plays a critical role in control of pointing or reaching with the hands Grasping - The anterior part of the intraparietal sulcus (aIPS) is involved in controlling hand and finger movements involved in grasping the target object o In the posterior parietal cortex o When messed up subjects couldn’t properly grip things even though they could when the hand area of M1 or other parts of parietal lobe were inactivated o Gets input from dorsal stream of visual association cortex o Also involved in recognition of grasping movements as well as their execution Deficits of Skilled Movements: The Apraxias Damage to frontal or parietal cortex on the left side of the brain can produce a category of deficits called apraxia, which is difficulty in carrying out purposeful movements, in the absence of paralysis or muscular weakness - can’t imitate movements or produce them in response to verbal instructions or demonstrate the movements that would be made in using a familiar tool or utensil - Four major types of apraxia o Limb apraxia: problems with movements of the arms, hands, and fingers o Oral apraxia: problems with movements in the muscles used in speech o Apraxic agraphia: a particular type of writing deficit o Constructional apraxia: difficulty in drawing or constructing objects Limb Apraxia Characterized by movement of the wrong part of the limb, incorrect movement of the correct part, or correct movements in the incorrect sequence - assessed by asking patients to perform certain movements, most difficulty is normally involving pantomiming particular acts without the presence of objects that are normally acted upon o it is easier for them to copy movements of instructor than come up with them Damage to the left parietal hemisphere causes limb apraxia of both hands but not damage to the right because the right hemisphere is involved with extrapersonal space and the left is involved with one’s own body - also in a study posterior regions of the right hemisphere tracked movements in space while the left parietal lobe organized the movements that would be made in response Frontal lobe more important for recognizing the meaning of gestures that are being imitated by frontal and parietal lobe activity Limb Apraxia can be caused by three types of lesions: - Lesions in the anterior corpus callosum - Lesions of the motor cortex in the left frontal lobe - Lesions in and around the intraparietal sulcus of the left parietal 
 lobe Constructional Apraxia Constructional apraxia is defined as difficulty in drawing pictures or diagrams or in making geometrical constructions of elements such as building blocks or sticks - caused by damage to the right parietal lobe - no difficulty in making most types of skilled movements with their arms and hands - no troub
More Less

Related notes for PSYC 211

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.