PEH 315 Motor Learning

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Rafe Simpson
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2 Tap the index finger of your right hand. It's a simple maneuver, yet carrying it out requires a vastly complicated series of actions. First, the image of the words on the screen (telling you to tap your finger) enters your eyes and strikes the retinas. The retinas then convert the image into electrical impulses. These impulses are sent to your brain. Your brain "sees" the words and gives meaning to them. Your brain then decides whether or not to carry out what it has read. If it decides yes, your brain's motor cortex, a small area that exists on the outer part of your brain, calls for messages to be sent through your spinal cord and down your arm to the muscles that control the finger. Only then does the finger move.

3 The motor cortex located on the left side of the brain controls movement on the right side of the body.

4 What would you do if you were a doctor and had patients who were missing pieces of their skulls? If you were Eduard Hitzig, a German doctor working at a military hospital in the 1860s, you'd conduct some experiments. Hitzig, working on patients who had pieces of their skulls blown away in battle, stimulated exposed brains with wires connected to a battery. By doing so, he discovered that weak electric shocks, when applied to areas at the back of the brain, caused the patients' eyes to move.

5 Later, around 1870, Hitzig teamed up with another doctor, Gustav Fritsch. Setting up a makeshift lab in Fritsch's house, the two stimulated the brains of live dogs. They found that not only could they cause crude movements of the dogs' bodies, but that specific areas of the brain controlled specific movements.

6 Soon after, John Hughlings Jackson, an English scientist, took the work of Fritsch and Hitzig further. Based on his observations of his wife's epilectic seizures, Jackson believed that the seizures were electrical discharges within the brain. The discharges started at one point and radiated out from that point. This suggested that the brain was divided into different sections, and that each section controlled the motor function (or movement) of a different part of the body. And since the pattern never varied, the way the brain is organized must also be set.

7 Wilder Penfield, a pioneering brain surgeon, mapped the motor cortex using mild electric current. Wilder Penfield took the next exploratory voyage into the brain starting in the 1940s. While operating on epileptic patients, Penfield applied electric currents to the surface of patients' brains in order to find problem areas. Since the patients were awake during the operations, they could tell Penfield what they were experiencing. Probing some areas triggered whole memory sequences. For one patient, Penfield triggered a familiar song that sounded so clear, the patient thought it was being played in the operating room.

8 During these operations, Penfield watched for any movement of the patients' bodies. From this information, he was able to map the motor cortex,.

10 The cartoon-like drawings in the illustration show how much of the brain's motor cortex is devoted to controlling specific body parts. The reason that some body parts are depicted larger than others (for example, the hand is larger than the shoulder) is that there are more muscles controlling those areas.

13 Psychobiologist Roger Sperry (born 1913) discovered that human beings are of two minds. He found that the human brain has specialized functions on the right and left, and that the two sides can operate practically independently. In the early 1960s, Sperry and colleagues, including Michael Gazzaniga, conducted extensive experiments on an epileptic patient who had had his corpus collosum, the "bridge" between the left and right hemispheres of the brain, split so that the connection was severed.

14 At first the patient seemed quite normal, but experimentation showed certain activities such as naming objects or putting blocks together in a prescribed way could only be done when using one side of the brain or the other. (Since the right eye connects to the left brain, the left hand to the right brain, and so on throughout the body, the stimulus would be given to the side of the body opposite the brain hemisphere being tested.) These abilities were not absolute, but it seemed that the left hemisphere specialized in language processes and the right is dominant in visual-construction tasks.

15 Motor Learning Major Areas of the Brain Involved in movement

16 Motor Learning ML is the process of improving the motor skills, the smoothness and accuracy of movements. It is obviously necessary for complicated movements such as speaking, playing the piano and climbing trees, but it is also important for calibrating simple movements like reflexes, as parameters of the body and environment change over time. The cerebellum and basal ganglia are critical for motor learning.

18 Areas of the Brain By recording the activity of neurons in different brain regions and by studying the effects of lesions in various brain sites, it has been demonstrated that there are important functional distinctions among brain centers. In the domain of motor control, some centers are involved in relatively low-level aspects of the control of movement and posture, such as the direction and force of single limb movement, whereas others are involved in higher-level aspects, such as planning extended sequences of actions.

20 Areas of the Brain Cerebellum Basal Ganglia Motor Cortex Pre-motor Cortex Supplementary Motor Cortex Parietal Cortex

21 Areas Cerebellum

22 To make the various segments of your hand and arm deploy smoothly, you need an internal "clock" that can precisely regulate the sequence and duration of the elementary movements of each of these segments. That clock is the cerebellum.

23 Cerebellum primitive brain

24 Cerebellum Regulation of Muscle Tone input from muscle spindles, vision, hearing, touch and balance. Damage = flaccid tone Coordination ataxia parts of the CNS that coordinate movement dysarthria, nystagmus, Sequencing - palm up, palm down Timing - agonistic and antagonistic muscle firings Learning

25 As so often in neurobiology, to understand exactly what the cerebellum does, we can observe patients in whom part of this structure has been destroyed (by a tumour or a stroke, for example). When these patients try to grasp an object, their hands start moving late, advance unsteadily, and either stop before reaching their target, or, often, accelerate past it. In terms of posture, people with damaged cerebellums characteristically display balance problems similar to those found in people who are drunk.

26 In a healthy person, the cerebellum first receives information about the intended movement from the sensory and motor cortexes. Then it sends information back to the motor cortex about the required direction, force, and duration of this movement

27 Basal Ganglia The term "basal ganglia" refers to a group of several structures in the brain:

28 The basal ganglia are involved in a complex loop that connects them to various areas of the cortex. The information from the frontal, prefrontal, and parietal areas of the cortex passes through the basal ganglia, then returns to the supplementary motor area via the thalamus. The basal ganglia are thus thought to facilitate movement by channelling information from various regions of the cortex to the SMA. The basal ganglia may also act as a filter, blocking the execution of movements that are unsuited to the situation. Not all of the circuits involving the basal ganglia are motor circuits, however. Many are instead involved in memorizing and in cognitive and emotional processing. A great deal about the basal ganglia remains unknown. They seem to play a far larger role than just their contribution to motor control.

Basal Ganglia Contributes to activation & retrieval of movement plans Scale the amplitude of movements Movement problems associated with area -

29 Basal Ganglia Contributes to activation & retrieval of movement plans Scale the amplitude of movements Movement problems associated with area - Huntingdon s Disease clumsiness, uncontrollable movements, dementia Parkinson s Disease shuffling gait, resting tremors, initiation of movements

30 This role of the basal ganglia in initiating and regulating motor commands becomes clearly apparent in people whose basal ganglia have been damaged, such as patients with Parkinson's disease. These patients display difficulty in starting the movements they have planned, as well as trembling and slowness once they do begin them.

31 Motor Cortex Localization of Brain function Trigger center rather than planning Force and direction Long-loop Reflexes

32 Pre-motor cortex It helps to guide body movements by integrating sensory information, and it controls the muscles that are closest to the body's main axis. Proximal muscles trunk & shoulders Orienting the body and readying the postural muscles for forthcoming movements Selected movement trajectories

33 Supplementary MC The SMA is involved in planning complex movements and in co-ordinating movements involving both hands. Planning & Production of Complex sequences of movement bimanual coordination Blood flow to SMC even when imagined Activity seen 1 sec before movement begins Suggests planning

Parietal Cortex Spatial attention drawing diagrams (Spatial Facility) Code spatially relevant behavioral intentions Apraxia (Greek for an act, work, or deed) is a neurological disorder characterized

34 Parietal Cortex Spatial attention drawing diagrams (Spatial Facility) Code spatially relevant behavioral intentions Apraxia (Greek for an act, work, or deed) is a neurological disorder characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire to and the physical ability to perform the movements. Ideational - pantomine Ideomotor - imitate

Cerebellum and Basal Ganglia

Cerebellum and Basal Ganglia 1 Contents Cerebellum and Basal Ganglia... 1 Introduction... 3 A brief review of cerebellar anatomy... 4 Basic Circuit... 4 Parallel and climbing fiber input has a very different