Re: How the brain is capable of perceiving sensory information and respond?

Hi Alex and Robyn! Excellent question! I'll try to point you in the direction of some good resources that should be easier to understand. The brain is capable of perceiving sensory information because of sensory receptors located throughout your body. Your ears, eyes, nose, tongue, skin, muscle, and insides all contain (to a greater or lesser extent) specialized sensory neurons. These are nerve cells (neurons) that detect particular types of information about their environment. For instance, photoreceptors in the retina are specialized to detect light, hair cells in the cochlea are specialized to detect sounds, some cells in the skin detect touch, and other cells in the skin sense heat/pain. Those sensory neurons (or other, nearby neurons that they connect to) all send connections over a distance to the central nervous system (brain/spinal cord). These neurons, in turn, eventually connect to areas of the brain/spinal cord that are capable of recognizing and interpreting this sensory information. So, the visual cortex (at the back of your head) recognizes changes in photoreceptor activity as visual information. Similarly, the sensory cortex interprets responses of skin cells as tactile stimuli, and differentiates pleasant tactile stimuli from noxious/painful stimuli. What next? Sometimes, the body perceives a sensory stimulus, then has a motor response -- like hearing a sound, recognizing it as your name, then orienting your face towards the sound and saying, "Whaddya want?". This is accomplished by telling the area of the brain that deals with motor output (called, not surprisingly, the motor cortex) to send a signal to the appropriate muscles. At other times, the brain's response to a sensory stimulus is more subtle -- like hearing a sound, and recognizing it as someone else's name, and carrying on with your business. To have what seems like a purely "thinking," non-motor response, your sensory cortex *still* has to talk to other areas of the brain (like language areas or emotional areas or memory areas). It's just that the motor output is absent. A really excellent resource for understanding neuroscience can be found here: http://faculty.washington.edu/chudler/neurok.html Information from this site will probably help you design experiments that test your classmates' ability to perceive different types of sensory information and to respond in motor or non-motor fashions. Hope this helps -- sounds like you have a fun project on your hands! Amanda Kahn amandak@phy.ucsf.edu