1. Copyright © 2006 by Allyn and Bacon Chapter 8 The Sensorimotor System How You Do What You Do This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or in part, of any images; any rental, lease, or lending of the program.

2. Copyright © 2006 by Allyn and Bacon 3 Principles of Sensorimotor Function Hierarchical organization  Association cortex at the highest level, muscles at the lowest  Parallel structure – signals flow between levels over multiple paths Motor output guided by sensory input Learning (experience) changes the nature and locus of sensorimotor control  Conscious to automatic, for example

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4. 2 Major Areas of Sensorimotor Association Cortex Each composed of several different areas with different functions Some disagreement exists about how to divide the areas up Posterior parietal association cortex Dorsolateral prefrontal association cortex

5. Copyright © 2006 by Allyn and Bacon Posterior Parietal Association Cortex Integrates information about  Body part location  External objects Receives visual, auditory, and somatosensory information Outputs to motor cortex

6. Copyright © 2006 by Allyn and Bacon What affect does damage to the posterior parietal area have? Apraxia – disorder of voluntary movement – problem only evident when instructed to perform an action – usually a consequence of damage to the area on the left Contralateral neglect – unable to respond to stimuli contralateral to the side of the lesion - usually seen with large lesions on the right

7. Copyright © 2006 by Allyn and Bacon Dorsolateral Prefrontal Association Cortex Input from posterior parietal cortex Output to secondary motor cortex, primary motor cortex, and frontal eye field Evaluates external stimuli and initiates voluntary reactions – supported by neuronal responses

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9. Secondary Motor Cortex Input mainly from association cortex Output mainly to primary motor cortex At least 7 different areas  2 supplementary motor areas SMA and preSMA  2 premotor areas dorsal and ventral  3 cingulate motor areas

10. Copyright © 2006 by Allyn and Bacon Motor homunculus

11. Copyright © 2006 by Allyn and Bacon The Motor Homunculus Control of hands involves a network of widely distributed neurons Stereognosis – recognizing by touch – requires interplay of sensory and motor systems Some neurons are direction specific – firing maximally when movement is made in one direction

12. Copyright © 2006 by Allyn and Bacon Cerebellum and Basal Ganglia Interact with different levels of the sensorimotor hierarchy Coordinate and modulate May permit maintenance of visually guided responses despite cortical damage

13. Copyright © 2006 by Allyn and Bacon Basal Ganglia A collection of nuclei Part of neural loops that receive cortical input and send output back via the thalamus Modulate motor output and cognitive functions

14. Copyright © 2006 by Allyn and Bacon 4 Descending Motor Pathways 2 dorsolateral  Corticospinal  Corticorubrospinal 2 ventromedial  Corticospinal  Cortico-brainstem-spinal tract Both corticospinal tracts are direct

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