Sensorimotor Integration

Transcript

0:00 – 0:30  [Basic Definition]  Sensorimotor integration includes diverse processes through which sensory signals influence the activity of the motor control systems.  The reflex is a simple example of sensorimotor integration where sensory signals are communicated to motor neurons without any requirement for communication with the brain.  A more complex example of sensorimotor integration is responding to a command – this requires sensory signals from the auditory system to influence activity of the cortical motor circuits, which in turn drive a behavioral response.

0:30-2:30  

Okay. So we’re going to talk about the neural basis of speech and language to get some sense of why things like this happen. We’ll see that speech and language depend on regions of the temporal association cortex near the auditory cortex that are important for comprehending language. And we’ll also see that speech and language depend on regions of the frontal association cortex near the motor cortical areas that control the mouth and tongue and throat. And we’ll see that speech and language also depend on the pathways that connect those regions.

Language really is a prime example of what we call sensorimotor integration. It’s really a fully integrated function that involves auditory cortex, motor cortex and regions in between, integrated together. So this idea of sensorimotor integration is not really that different in principle, from the idea of sensorimotor transformation, which we talked about in our vestibular lecture.

In that case, there were synaptic chains linking sensation to a movement. In the case of the vestibulo-ocular reflex or the vestibulo-collic reflex, vestibular input ultimately led to changes in muscle activation.

In something as complex as language, it’s not clear that what’s happening can really be understood as something as simple as a transformation, you know, through a chain of synapses. So here, we tend to use this, albeit more vague idea of sensorimotor integration to describe what seems to be happening in processes like this. But it’s still kind of a thorny idea. For years, I heard the term sensorimotor integration and I was like, you know, I don’t quite understand exactly what it means. But then as I progressed in my career, I realized that the field itself doesn’t really understand exactly what it means. It really is sort of a vague idea. But it does seem to capture some of what’s going on here.

2:30-3:00  [Parallel Vocabulary] In introductory classes you learned about many examples of sensorimotor integration, which is an umbrella term that includes a huge variety of pathways.  Here are two examples… The retinal ganglion cells send visual signals to the superior colliculus, which in turn projects to the brainstem motor control centers that influence the control of eye position and can direct the eyes towards a specific point in space.  Similarly, the vestibular afferent cells send signals about head position to the vestibular nuclei, which in turn project to the spinal cord motor control circuits that influence posture and can help to maintain balance during everyday tasks.

3:00-4:00  [Here’s a real world example]  Detailed knowledge of sensorimotor integration plays an important role in clinical neuroscience. Reflexes, like when the pupil constricts in response to bright light, are very basic examples of sensorimotor integration.  Importantly, reflex testing can be combined with knowledge of neural circuits, to test for neural injuries, even if a patient cannot communicate or if that patient is unconscious. For example, the vestibulo-ocular reflex, which is abbreviated VOR, can be used to test function of the brainstem.  Recall that the VOR involves sensory signals about head position that are transmitted to the vestibular nuclei in the brainstem, which in turn transmits signals to the cranial nerve nuclei in the brainstem, which in turn coordinate movement of the eyes.  So, even if a patient cannot communicate, you could test brainstem function by turning the head from side to side and then looking for compensatory eye movements.  A lack of eye movement would suggest brainstem damage, and if you suspect the brain has been injured, it is important to check for this because damage to the brainstem can potentially disrupt the circuits that regulate breathing.

4:00-6:00 [Follow along with this example]

6:00-6:30 [Here are a few readings to help you review]
1) Neuroscience (Purves)

• Chapter 20: “Eye Movements and Sensorimotor Integration”

2) Neuroscience Exploring the Brain (Bear)

• Chapter 13: “Spinal Control of Movement”