APRAXIA: Neuropsychological-Information Processing Models Kenneth M. Heilman M.D. The James E. Rooks Jr. Distinguished Professor of Neurology, University of Florida, College of Medicine

Definition Exclusionary: The loss of the ability to perform purposeful skilled movements when this deficit can not be explained by motor deficits (e.g., weakness), sensory defects, movements disorders (tremor, ataxia, chorea, athetosis, ballismus, myoclonus etc) or certain cognitive disorders (e.g., poor comprehension). Inclusionary: There are 5 major types of apraxia and each are defined by the task demands and types of errors.

Types of Limb Apraxia 1. Limb-kinetic 2. Ideomotor 3. Dissociation and Conduction 4. Ideational 5. Conceptual

LIMB-KINETIC APRAXIA Testing: 1) pegboard; 2) pincher grasp to pick up small coins; 3) coin rotation. Error Type: Loss of finger deftness or dexterity. Loss of the ability to perform independent, but coordinated precise finger movements. Pathophysiology: Injury to corticospinal system and/or convexity premotor cortex. Left hemisphere dominance.

IDEOMOTOR APRAXIA Testing: 1. Performance of transitive movement to command (e.g., show me how you would slice bread with a knife. 2. Imitation of transitive movements. 3. Use of actual tools and implements 4. Discrimination between correct and incorrect postures and movements.

IDEOMOTOR APRAXIA…CON’T Error Types 1. Postural Errors: a) Incorrect posture; b) Body-part as tool. 2. Movement Errors: a) Movement of incorrect join or joints; b) Poor joint coordination. 3. Orientation Error: Not properly directing action toward target. 4. Timing-Speed Errors:

PATHOPHYSIOLOGY 1. Callosal Lesions 2. Left Hemisphere Lesions A) Geschwind and Kaplan, right arm normal, left impaired to command only…possible language disconnection (see Fig.)‏ B) Watson and Heilman, right arm normal, left arm impaired to command, imitation, and use of actual objects…disconnection of movement representations. 2. Left Hemisphere Lesions A) Asymbolia – apraxia and aphasia can be dissociated B) Geschwind Intrahemispheric disconnection-cannot explain impaired imitation and actual object use (see Fig). C) Heilman-Rothi- lateralized movement representations in left parietal lobe (see Fig).

CALLOSAL APRAXIA-VERBAL DISCONNECTION LT RT PMC MC SSC Lexical- Sematics VAA VC

Geschwind’s Model of Ideomotor Apraxia Right Premotor Cortex Right Motor Cortex Wernicke’s area Left Motor Cortex Left Premotor Cortex Auditory cortex

Heilman-Rothi Model SMA Premotor Cortex Object Recognition Motor Units Movement Formula Convexity Premotor Cortex Lexicon

IDEOMOTOR APRAXIA SMA Premotor Cortex Object Recognition Units LT MOTOR CORTEX Movement Formula Convexity Premotor Cortex Lexicon

Conceptual Apraxia Definition: A loss of mechanical knowledge, such that a patient cannot select the proper tools to perform a tasks, or does not understand the mechanical advantage offered by tools.

Conceptual Apraxia Continued Testing: 1) Tool Selection (e.g., Patient is shown incomplete task, such a partially driven in nail and tools such as a hammer, screwdriver, hand saw, wrench, and can opener. The patient is asked to point to the tool need to complete the task. 2) Alternate Tools (e.g., The hammer is taken away and the patient is asked, “What tool would you use now?” 3) Developing Tools (e.g., The patient is shown a wooden block with an eye hook on top which is sitting on the bottom of a plexiglass tube. The patient is given a wire and asked to retrieve block. The patient needs to make hook.)‏

Conceptual Apraxia Continued Errors: Inability to correctly perform the tests mentioned above. Pathophysiology: Loss of action-tool semantics. In the right handed people this knowledge is stored in the left hemisphere and functional imaging suggests that the left parietal lobe might also be important for storing these representations.

Conceptual Apraxia Lexical Action-Tool Semantics Semantics SMA Premotor Cortex Motor Cortex Movement Formula Object Recognition Units Convexity Premotor Cortex Motor Neurons

Dissociation Apraxia Definition: Inability to perform correct pantomimes to a modality specific stimulus. Testing: Pantomime to command, seeing tool or object, feeling tool or object and imitation. Error Types: Failure in one modality (e.g.,command), but normal performance in other modalities (e.g., seeing tool.)‏ Pathophysiology: Disconnection of intact movement representations from modality specific input (see figure).

Dissociation Apraxia SMA Premotor Cortex Object Recognition Motor Units Motor Cortex Movement Formula Convexity Premotor Cortex Lexical Semantics

Dissociation and Conduction Apraxias: A=Verbal dissociation apraxia; B= Visual dissociation apraxia;; C=Conduction apraxia ; Lexical Semantics Action-Tool Semantics A SMA Premotor Cortex Motor Cortex Verbal command B Movement Formula Object Recognition Units Convexity Premotor Cortex Visual Ass’n Cortex V5 View tool C View Pantomime

Ideational Apraxia Definition: Loss of the ability to order a series of acts to achieve a goal. Testing: Present patient with items needed to complete a task such as making a sandwich (bread, lettuce, tomatoes, cheese, mayo, ham, and a knife). The ask patient to make sandwich. Errors: Patient makes errors in ordering a series of acts (e.g., cuts bread in half before putting on the ham etc. Pathophysiology: Not fully investigated

PRAXIS SYSTEMS Right Hemisphere CORPUS CALLOSUM To spinal cord MOTOR CORTEX Right Hemisphere PREMOTOR CORTEX CORPUS CALLOSUM OBJECT UNITS ACTION SEMANTICS PREMOTOR COREX Visual input MOVEMENT REPRESENTATIONS MOTOR CORTEX Visual gesture input LEXICAL- SEMANTICS Auditory input To spinal cord

SUMMARY: a=dissociation apraxia; b=conceptual apraxia; c=ideomotor apraxia; d=limb-kinetic apraxia; e = conduction apraxia Lexical - Semantics b Action-Tool Semantics c SMA Premotor Cortex a Motor Cortex c Object Recognition Units a Movement Formula Convexity Premotor Cortex d d d c e V-5