Motor Control of Normal, Reach, Grasp (1) PDF

Neural Contributions to Reach, Grasp, and Manipulation DPT 425 Functional Neuroscience Fall 2024 Objectives: Students will describe the upper extremity functions Students will describe the neural contributions to UE Reach, Grasp and manipulation Primary resource fo...

Neural Contributions to Reach, Grasp, and Manipulation DPT 425 Functional Neuroscience Fall 2024 Objectives: Students will describe the upper extremity functions Students will describe the neural contributions to UE Reach, Grasp and manipulation Primary resource for this information is Shumway-Cook and Woollacott Motor control text, Chapter 17  Introduction Upper-Extremity (UE)Function Basis for fine motor skills Plays role in gross motor skills Recovery of function important aspect of retraining motor control Contextual factors impact upper-extremity function Environment and individual UE Function is integrated into most self-care, work, household activities.  International Classification of Function (ICF) Self care (dressing, feeding) Individual capabilities domestic life (cooking cleaning) Activities in real world situations Tasks Reach, Grasp and Manipulate 4  Sensorimotor Processing for Eye Head and hand coordination Constraints of individual Movement Type of task (strategy) Task Specific environmental constraints Individual Environment Goal is to understand how Individuals’ CNS control UE movements. In most cases UE tasks require high attentional demands What is going on in the Brain? Individuals need to focus attention using eye, head and neck coordination Visual cortex: Posterior Parietal Association area: Sensory Processing Somatosensory Cortex Prefrontal area: Dorsolateral frontal association: Pre motor cortex: Primary motor cortex: Basal Ganglia: Motor Processing Cerebellum: Spinal cord: carries motor command to the motor neurons Motor neurons: activate hand and forearm muscles Sensory receptors on fingers and hand Spinal cord pathways: Dorsal column/medial lemniscus Somatosensory Cortex Sensory Processing What about the limbic system?  Hedmann’s Model for movement observation analysis Reaction Time = CNS Anticipatory Processing time Motor Control Principles (SC&W PP 466) Feedforward and Feedback control See motor control lecture; Motor program theory Equal to open and close loop control concepts. Visual system is highly involved helping in feedforward (Anticipatory control) Somatosensation is highly involved helping in feedback (Reactive control) Locating a Target Reach and grasp: kinematics Feedforward versus Feedback Control of Movement Efficient reaching: both feedback and feedforward control processes Feedforward (anticipatory) control: takes advantage of previous experience to predict consequences of sensory information received Feedback control: input from sensory systems being compared to reference signal, representing a desired state of the system (reactive) Reactive control: When the disturbance cause deviation from the desired state 11  Locating a Target Eye–Head–Trunk Coordination Vision: object location and to guide movements of the hand Reaching to objects located in far visual field requires of eye, head, and trunk movements Interactions between Eye Movements and Hand Movements Eye and hand movements interact with and influence each other Proprioceptive signals from eye muscles contribute to ability to localize targets in extrapersonal space  Reach and Grasp Kinematics of Reach and Grasp Ability to adapt how we reach is a critical part of upper-extremity function Task constraints and goals affect reaching phase of movement Velocity profile: Velocity of arm versus time Changes based on the task goal Grasping or pointing. Think of this as invariant features of a reaching task (Motor program theory) Neural control of Reach and grasp Review from Cognitive lecture. Association cortices - perceptions and planning Review from Cognitive lecture. Sensory system What is happening around me? Where am I in space? How are my joints positions relationship to each other? Body Position Map: Somatosensory Sensory information used proactively to help plan movements Sensory information use feedback determine accuracy of movement and for correcting errors  Schematic of visual pathway: information is transmitted via both serial and parallel pathways: the Where and What Streams of visual processing. Review from Where Stream: Cognitive and Location in space & movement Visual Dorsal pathway to posterior parietal lectures. cortex Action Pathway What Stream: SWC &W Shape and form Object recognition Ventral pathway to inferior temporal cortex Perceptual Pathway Clinical implication Clinicians should assess perceptual and action components of visual guided reaching They are have different neural substrates Patients may have impairments in only one or both. Understanding the essential features of an object to be grasps is as important as modifying grasp to accommodate the feature. Interventions should train both perceptual and action components of the movement. Posterior Association Areas Review from Cognitive lecture. Spatial cognition Mediated by the Posterior Parietal Association area Wide variety of behaviors mediating attention to intrapersonal and extrapersonal space Parietal lobe damage involving the lateral association: Unilateral hemispatial neglect most prominent deficit Facial recognition Mediated by temporal association area Damage can result in prosopagnosia Object Identification What is happening in the Posterior Parietal Cortex? What is Spatial Cognition? Active during sensory and movement related activities Sensorimotor transformation Movement planning and Intentional Maps Early motor planning Eye, head, trunk and limb maps are active Formation of internal models Body representation Coordinate Transformations  Role of Sensory information in Anticipatory (Feedforward) control of Reach and grasp Visual Somatosensory Locating and determining the Determination of initial position initial direction of the reach and initial coordination of limb Information on the characteristic segments. of the object to be grasps. E.g. how the body and limb is initially position Vision important in referencing hand location and object location. Decrease accuracy when an individual can not see hand Vision may be import in integrate Visual and proprioceptive Maps Role of Sensory Feedback to Reach and grasp Visual Somatosensory Attain final accuracy May not be need for simple movement Visual feedback reaching is more But essential for complex movement or accurate, but slower finely regulated movements Without feedback, faster but less Plays important role when limb deviates accurate. from plan path (error detection) Visual feedback does not play Cutaneous and proprioception required for much role in grasp accurate grasp and within hand manipulation control However, think about visual guided continuous object manipulation E.g. solving a rubrics cube  Motor System in Reach and Grasping Execution of Movement Premotor and Primary Motor Cortex receives inputs from PPC Intention or goal, location- direction of movement Hand formation and orientation: objective characteristics E.g. neurons in PPC and motor cortex have been shown to encode for grasp type. Evidences suggest that PPC encodes in visual reference or coordinates and Premotor encodes more in body reference or coordinates  Two Separate Descending Pathways for Reach and grasp Motor development of reaching occurs early and grasp and hand manipulation develops late Relates to maturation of the corticospinal tract Individuals with corticospinal injury can show impairments in grasp and manipulation, but transport is intact. “Transport” component: Reach related to distance and location Shoulder and elbow pathways Proximal control may include midbrain and brainstem structures: reticulospinal and rubrospinal tracts Grasp “hand precision” component Wrist and hand pathways Relay on corticospinal pathways. Musculoskeletal contributions Complex relationship between neural and musculoskeletal systems. Changes in ROM, strength or muscle tone will change neural command Movement compensation Think of motor compensation in reaching when elbow extension range of motion is limited Think of motor compensation when elbow extensors are weak. How does scapular control play a role in reaching and grasping? How does the scapular play a role in arm movement versus arm stabilization. Postural support of reaching and grasping Postural system maintains upright orientation and alignment of postural segments during arm movement in anticipatory and feedback control Anticipatory postural adjustments Reactive postural adjustments We will discuss in week 13. Motor control elements Goal Directed Command Posture Reach Grasp-manipulation Medial activation Rubriospinal Medial spinal tracts Reticulospinal Corticospinal Grasping Patterns Power Grip Precision Finger and thumb pads are Force is transmitted through directed toward the palm to fingers and thumb transmit force Poke Hook grip: hang on Pinch Spherical grasp: hold a ball Clench Cylindrical grasp: hold a can palm Anticipatory Control of grasp and lift Grip formation occurs during The nervous system anticipates transport in anticipation of and adapt grip for different weight grasping and surface characteristics for Hand adapts to size shape and lifting use of the object Finger movements are timed in Cerebellum plays a role in relationship to the transport predicting forces needed to maintain grasp Feedback loops for slip errors for motor adaption and store force predictions Coordination of reach and grasp Reach and grasp are kinematically coupled Invariant features of movement: Timing of transport and hand opening May represent a generalized motor program Rules that are stored in the CNS Other elements of reach, direction, distance speed, grasp types are modulated based on initial conditions of the task (See motor program theory)  Reaction Time (RT) tells us about complexity of movement and time to process in anticipatory control RT is a basic research tool used to RT is a measure of Sensorimotor processing before movement measure discrete tasks like reaching RT Movement Time Response Time Time Stimulus Response Begins Response Ends  Simple versus Choice Reaction Time Choice: increase time for visual processing and selecting motor responses. Fitt’s law of movement Speed versus Accuracy Trade off Movement time increases with distance and accuracy demands Suggests that movement time is dependent on visual processing constraints Theories of Reaching control Distance Programing Theories CNS activate a set of agonist muscle to propel the limb based on perceived distance- heavily relies on initial visual perception of distance of the target. Impulse driven control and then feedback correction Location programing Theories Limb muscles are like springs and the CNS program stiffness of agonist and antagonist based on location of a target Suggest that signals to flexors and extensor to increase or decrease stiffness based on relative flexion or extension of limb and on target location.  Interference between reaching and cognitive tasks Dual Task Paradigm Motor task and Cognitive task, e.g. Reach precision and attending to visual stimulus such as reading Reaction time: movement onset time increases Movement time does not change. Suggest that movement planning is effected, therefore the cognitive task “interferes” with the movement task. Prefrontal Cortex and Limbic System influence Motivation Center Prefrontal Limbic System Activated perception and action Explicit Memory Learning of reaching and grasp Emotion and Drive Plays a role in stopping of an action and choice of action Analyzing behavior in context of goal directed movement Conceptual mapping of Neural control of Reach and Grasp. Consider creating a conceptual map  What might be the elements of the conceptual map? In most cases high attentional demands Visual cortex: So need to focus attention using Sensory Processing eye, head and neck coordination Target Location Target Identification Posterior Parietal Association area: Planning intention and decisions Formulation of internal models: egocentric reference Sensorimotor transformation (visual reference to body reference) Prefrontal area: Dorsolateral frontal association: Determine environmental goal in allocentric space Planning of movement to accomplish goal Pre motor cortex: selection of motor plan and sequence Motor Processing Primary motor cortex: command of movements. Basal Ganglia: judges grasps force and sequence Cerebellum: correct movement errors and maintain grip force (Sensory Feedback loops from spinocerebellar tracts and inferior olive) Spinal cord: carries motor command to the motor neurons Motor neurons: activate hand and forearm muscles Somatosensory receptors on fingers send message that cup is being grasps. Dorsal column/medial lemniscus carries message back to the sensory cortex. Sensory Cortex; Receives feedback the at cup has been grasps. Example of conceptual Map Egocentric spatial frame: Integration of body scheme in relationship to visual perception of the environment. Mapping interpersonal space to extrapersonal space Allocentric spatial frame: Perceptual identification in the environment. The environmental goal would be to change something in the allocentric space. Motor Control elements and motor learning are held in similar regions of brain Extrapolate reaching and grasping research identified mechanisms to other UE tasks Pick up a spoon and feeding Biomechanics Class Task analysis Overhead throwing