We have reached a significant juncture in Medical Neuroscience as we turn our attention to the organization and function of the sensory systems. We will begin our studies with the somatic sensory systems, which includes subsystems for mechanical sensation and pain/temperature sensation. But before we get there, it is worth considering first some organizing principles that will set the stage for studies of somatic sensation and all the other sensory systems of the body.

This module will provide lessons that are designed to help you understand the basic mechanisms by which light is transduced into electrical signals that are then used to construct visual perceptions in the brain. Your studies of the visual system will benefit you at this point in the course, but also in later studies when we use the visual system as a model for understanding general principles of developmental plasticity. Lastly, it is worth noting how much of the forebrain contains elements of the visual pathways. Thus, injuries and disease in widespread regions of the brain may have a clinically important impact on visual function. All the more reason to learn these lessons well as you progress in Medical Neuroscience.

Our survey of the sensory systems continues as we now turn our attention to the auditory system, the vestibular system, and the chemical sensory systems. As you study this content, notice the similarities and the differences that pertain to the general mechanisms of sensory transduction and the broad organization of the central pathways in each of these sensory systems. In particular, note the similarity in transduction mechanisms for audition and vestibular sensation; and note the “logic” of sensory coding in the chemical sensory systems.

At this juncture in our exploration of motor control, let’s focus on one of the best studied paradigms for understanding the neural control of movement: the eye movement system.

We conclude our survey of movement and motor control by considering the visceral motor system, perhaps better known as the autonomic nervous system. As you study this lesson, consider how the disparate physiology of the viscera has impact not only on the internal state of the body, but also on implicit processing in the forebrain. We will return to this matter when we consider the neurobiology of emotions near the conclusion of Medical Neuroscience

This module represents another turning point in Medical Neuroscience. Now that we have surveyed human neuroanatomy and our sensory and motor systems, we are ready to take a step back and consider how this magnificent central nervous system came to be the way that it is. We will also learn how the brain re-wires itself across the lifespan as genetic specification, experience-dependent plasticity and self-organization continue to interact, re-shaping the structure and function of neural circuits throughout the central nervous system.

It may surprise you to know that in all of our studies of the neural systems for sensation and action, we have yet to properly account for the organization and function of roughly 75% of the entire cerebral mantle. Thus, only 25% of the cerebral cortex is accounted for by the modal sensory and motor cortical areas. The majority of the human cerebral cortex is multi-modal cortex that associates signals derived from one or more modal systems. We now turn our attention to this “associational cortex” as we consider more complex aspects of brain function.

In this concluding module of Medical Neuroscience, we will consider the neurobiology of sleep and the neurobiology of emotion, including addiction. Both topics involve explorations of complex, widely distributed systems in the forebrain and brainstem that modulate states of body and brain.

Please allow me a few more moments of your time to express my thanks for all your efforts to make it through Medical Neuroscience, and to wish you well on all your future endeavors!