Sensory-motor processing in planning and execution of movement

Subhadeep Dutta Gupta M.Phil Scholar

Department of Neurophysiology, NIMHANS

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Sea squirt (Ascidiacea)

Introduction

• Movement is an important feature of living organism.

• All interaction with the surrounding world is through motor

system.

• The motor system continues to develop through maturation

of neuronal circuitry and by learning through different motor

activities during the first 15 years of life.

Hierarchy of motor control:

• Background:

Jackson, (1889) : higher motor centers controlling simple movements.

William James, (1890) : voluntary movement is secondary to reflexive

actions, and involves anticipatory image.

C. Sherrington, (1906) : distinguished between upper & lower motor neurons.

Keele, (1968) : ordered nature of high level motor programs for feed- forward

control of movements.

3 levels in hierarchy of motor control:h Cerebral cortex:

-- primary motor & sensory cortex, premotor cortex, supplementary motor

cortex

-- mediated by Pyramidal system.

Brain Stem:

-- Extrapyramidal system.

Spinal cord:

-- ‘final common pathway’ modulated by higher centre.

-- executive centre for reflexes & pattern generation.

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Organization of the motor system:

Cerebral Cortex: Representation of the motor functions:

• J.H Jackson:

-- Specific part of the cortex has a causal role in movement.

• Fritsch, Hitzig, Ferrier:

-- Electrical stimulation at specific region of the cortex evoked

movements in contralateral body parts.

-- Lesion of that region caused loss of motor control of the specific

body part.

Cerebral Cortex: Sensory & Motor Homunculus:

Cytoarchitecture of motor cortex :

-- Primary motor cortex is agranular.

-- Layer IV (cell-packed granular layer) is very

thin or nearly absent.

-- Layer V (descending output layer) is thicker

& contains the giant Betz cells.

-- These neurons makes up around 30% of the

fibres in the cortico-spinal tract.

Betz cells of layer V

Organization of precentral motor area:

--Principles of Neural Science, 5th Edn

Internal Model:• Postulated neural process that simulates the response of the

motor system in order to estimate the outcome of a motor

command.

• The motor system makes use of internal models in order to

control the musculoskeletal system during rapid, skilled, motor

behaviour.

• Ex – Size Mass estimation-- Science, 269, 1880-1882 (1995).

Processing of sensory information in the cerebral cortex

--Principles of Neural Science, 5th Edn

Cross talk of association areas :

--Principles of Neural Science, 5th Edn

Motor & executive control

Emotional responses

• Parietal Association Cortex: -- key role in the visual guidance of motor behaviour.

-- spatial perception & cognition.

-- suited for such computation as it is connected with visual,

somatosensory & motor areas of cortex.

• Damage: -- Ideomotor apraxia

-- Impaired speech repetition

-- Personal neglect syndrome

‘Binding’

Conceptual representation of feature binding & representation:

Trends in Neurosciences, 2013(36)3

• Temporal Association Cortex:

-- Object recognition and semantic memory.

Inferotemporal neurons :

-- are sensitive to the shape, colour, and texture of an object.

-- insensitive to size and location of the objects.

-- activity is not influenced by the motor behaviour of the animal.

• Damage:

-- semantic dementia Visual object agnosia

Connection between prefrontal & motor cortex:

--Principles of Neural Science, 5th Edn

Emotional & cognitive processes in the PFC controls the motor behaviour

Primary Motor Cortex:

• Primary motor cortex neurons fire 5-100 msec before the onset of a

movement.

• Primary motor cortex encodes the force of a movement (Evarts et

al., 1968).file:///D:/Presentation%20on%20Movement/Videos/1.Force%20of%20movement.swf

• It encodes the direction of movement (Georgopoulas et al., 1982).

-- Many neurons are selective for a particular direction of movement. file:///D:/Presentation%20on%20Movement/Videos/2.Direction%20of%20movement.swf

• It encodes the extent of movement.

• It also encodes the speed of movement. file:///D:/Presentation%20on%20Movement/Videos/3.Speed%20of%20movement.swf

-- Bell shaped curve

• Premotor cortex neurons signal the preparation for movement

(Weinrich and Wise,1982). file:///D:/Presentation%20on%20Movement/Videos/4.Preparation%20of%20movement.swf

-- Motor- set neurons ‘Go’ signal.

• Premotor cortex is sensitive to the behavioural context of a

particular movement (Iacoboni et al., 2005).file:///D:/Presentation%20on%20Movement/Videos/5..Behavioral%20context.swf

• Premotor cortex signals correct and incorrect actions.

Premotor Cortex:

g• Premotor cortex neurons signal various sensory aspects

associated with particular motor acts.

-- Some neurons fire when a subject is performing a particular

action.

-- Same neuron fires selectively when the subject sees someone

performing a particular action.

-- It also fires selectively even without a visual or motor activity.

-- Concept of Mirror & Cannonical Neurons (Rizzolatti et al.,

1996)

Supplementary Motor Area:

• SMA is involved in the transformation of

kinematic to dynamic information.

• SMA responds to sequences of movements

and to mental rehearsal of sequences of

movements (Roland et al., 1980). file:///D:/Presentation%20on%20Movement/Videos/6.Mental%20rehearsal.swf

Descending pathways that mediate motor functions:

--Fundamental Neuroscience; 3rd Edn

Corticospinal system:

The Malleable Motor Map:

-- Annu. Rev. Neurosci. 2000. 23:393–415

Phantom Limb & Mirror Therapy:

Amputated Limb

Intact Limb

Motor control centers in the brain stem:

The major brain stem nuclei sending fibers to the spinal cord.--The Central Nervous System,4th Edn

h• Hans Kuypers classification:

Medial Brain stem pathway

-- Vestibulospinal tract

-- Reticulospinal tract

-- Tectospinal tract

Lateral Brain stem pathway

-- Rubrospinal tract

Experimental evidence:

Transection of the direct pathway in Rhesus monkeys (with intact Indirect pathways):

difficulty in using the distal parts of their limbs.

unable to reach toward & pick up food with their fingers

they used the entire arm to sweep the food toward

them.-- Lawrence & Kuypers, 1968

--Principles of Neural Science, 5th Edn

Motor control at Spinal level: Reflex:

-- Automatic, stereotyped movement in response to stimulation of

peripheral receptors.

-- integrated by centrally generated motor commands into complex

adaptive movements.

Central pattern generator:

• Neural network within CNS that give rise to rhythmic

motor activity independent of sensory inputs.

• Ex- Motor behavior such as respiration, walking, feeding,

swimming, flying.

• Studied extensively in lampreys, snails, leeches, flies,

frogs, chicks etc.

EMG Recording in Lobster:

KKKKKk

k

HHHHHHHHHH

-- The Journal of Neuroscience, 1987, 7(7), 2097-2112.

Lateral Pyloric Neurons (LP)

Pyloric Neurons (PY)

Pyloric Dilator Neurons (PD)

Lateral Ventricular Nerve (lvn)

Generation of Fictive locomotion:HHHHH

HHHHHHH

hHHHHHHHHHH

-- J Neurophysiol 82:2029-2038, 1999.

Mechanism of swimming in lamprey:

Glutamate The membrane depolarizes

Na+ and Ca2+ flow into the cell through the NMDA receptors

Ca2+ activates K+ channels

K+ flows out of the cell

The membrane hyperpolarizes

Ca2+ stops flowing into the cell

K+ channels close

The membrane depolarizes, and the cycle repeats.-- Neurosci. Lett. 89, 31–35., 1987

Rhythmic activity in a spinal interneuron

Sensorimotor integration in movement disorders:

Parkinson’s Disease:

• Classical view:

• -- dysfunction of the basal ganglia-motor cortex

circuits.

• BG involved in:

• somatosensory discrimination

• visual perception

• spatial working memory -- Curr Opin Neurobiol 1997; 7:157-63.

• When external, visual or auditory cues are

provided, substantially improvement of specific

features of Parkinsonian bradykinesia was noted.

• Deficient internal cueing mechanism to

discharge successive stages of a movement

sequence ????

-- Mov Disord 2000; 15: 879-83.

Stroke:

• Sudden focal neurological deficit due to a

cerebrovascular abnormality.

• Decreased plasticity in affected region while an

increase of sensorimotor integration process

happens in non-affected regions.

• Restraint of the intact limb over an extended

period, in combination with a large number of

repetitions of task-specific training of the

affected limb.

Positive outcome

-- Lancet Neurol 2008; 7: 33-40.

Scheme of interaction between different motor centers

-- Fundamental Neuroscience; 3rdEdn

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• Fundamental Neuroscience, 3rd Edition, Larry Squire

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Neuroscience, 1987, 7(7), 2097-2112.

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2009 (62) 45-56.

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Rat Isolated Spinal Cord, J Neurophysiol ,1999, (82) 2029-2038.

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therap. Mov Disord 2000; 15: 879-83.

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of upper limb function in stroke survivors who have received constraint-induced

movement therapy: the EXCITE randomised trial. Lancet Neurol 2008; 7: 33-40.

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integration. Science, 269, 1880-1882 (1995).

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March 2013, Vol. 36, No. 3.

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“All mankind can do is to move things… whether whispering a syllable or felling a forest.”

--Sir Charles Scott Sherrington

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Thank You !!!!