Last night, I headed to the beautiful Bell House in the Gowanus section of Brooklyn for the latest Secret Science Club lecture, featuring neurologist Dr Anne Churchland of the Cold Spring Harbor laboratories. Dr Churchland seeks to bridge the gap between our knowledge of sensorimotor reflexes and more complex behavior. Specifically, she studies the decision-making process.
Since time immemorial, humans have wondered what makes us who we are and what makes us decide to do what we do. Disease states and drugged states played some role in elucidating the mysteries of the brain, but the brain was largely unknowable. Now that we have the ability to measure neuronal activity, and to perturb neuron groups, we can begin to understand the neural circuits which give rise to behavior. The ability to understand the brain's "circuitry" can also help us solve clinical problems, such as depression, which has a major cost. Approximately one in seventeen individuals in the U.S. suffers from severe mental illness.
Dr Churchland covered the topic of reflexive behavior, ranging from such simple, easily understood behaviors as the knee-jerk reflex to the more complex vestibulo ocular reflex, which stabilizes images when one moves one's head. Dr Churchland ran us through some tests to demonstrate the vestibulo-ocular reflex, having us move our fingers in front of our eyes and asking us if the image were blurred (she joked about how the beer-guzzling audience would naturally see blurred images).
She then showed us some headlines from the popular press which made a butchery of neuroscience, including the embarrassing NY Times Headline "You Love Your iPhone. Literally.", which cited activation of the insular cortex as evidence of "love" when one handled one's iPhone... though the insular cortex plays a role in disgust responses as well as love.
Dr Churchland posed the question, "Why is understanding the brain so hard?" One reason for this difficulty is the complexity of the brain- the brain is composed of eighty-six billion neurons, which form various structures within the brain. Another difficulty is that introspections about brain function are misleading. Dr Churchland used the game of chess as an example of incorrect intuitions about brain functions... while most laypersons believe that understanding the various chess moves is more difficult than understanding how the actual pieces are physically moved- in 1997, a computer was able to outplay a chess grandmaster , but the development of artificial intelligences which can manipulate objects is in its infancy (Dr Churchland showed a tragicomic video of a robot hand trying to pick up a coffee cup). Additionally, brains do different things in different animals. Dr Churchland cited bats and mice as two mammals with very different brains. One can look to see how problems are solved in animals- this works well for kidneys and hearts, which are very similar in different animals, but brains are much more diverse. A model system has to be chosen carefully due to the evolution of brains to serve different needs for different ecological niches.
Dr Churchland's major goal is to bridge the gap between sensorimotor reflexes and complex behaviors. Reflexes are "locked in" timewise- when one's knee is tapped with a mallet, the reflex occurs in an inflexible timeline. Complex decisions take place on a more flexible time scale, and integrate many systems of sensory input. Dr Churchland cited the purchase of a car as an example- one uses various sensory inputs to evaluate a vehicle, and there is no stereotypical time scale on which a final decision is made.
Dr Churchland went on to demostrate multisensory integration, and the differences between our processing of stimuli. Auditory stimuli are not very good in a spatial sense- it is often hard to pinpoint where a sound is coming from. Visual stimuli are very good at spatial resolution. As an example of this disparity, Dr Churchland cited a ventriloquist, who is able to exploit our poor auditory special recognition by providing a deceptive visual stimulus- we are "fooled" by the dummy's mouth moving, so it seems like the sound is emanating from the dummy. As a more glaring example, she pointed to the speakers around the room, from which her voice was emanating, and noted that none of us had any problem perceiving her as the source of her voice.
The visual system is not particularly good at timing, while the auditory system is much better at it- by flashing a dot once, but sending out two "beeps" in rapid succession, she was able to "fool" the audience into believing that two dots were flashed.
Subjects weigh incoming information according to its reliability- Dr Churchland cited a 2002 paper by Ernst and Banks (PDF) which dealt with the integration of visual and haptic (touch) stimuli- when deceptive visual stimuli are presented, a subject can use touch to correct perception. The brain can change from one stimulus to another moment-to-moment, with regards to environmental statistics- multisensory integration is geared towards a statistically optimal condition.
In her lab, Dr Churchland uses rodents as subjects- rodents are able to judge stimuli rates to be high or low. A subject was confronted by an array of LEDs and speakers and would respond to the auditory and visual stimuli in order to gain a reward, a drink of water. A low stimuli rate would indicate that the rat would be rewarded by placing its snout in the left-hand dispenser, a high stimuli rate would indicate the right-hand dispenser. Twelve "events" per second was chosen as the arbitrary "cutoff" between high and low rates. While the task that had to be performed by the rat was unnatural, it nevertheless tapped into natural neural pathways. A rat could be trained to shape its decision making behavior (at this point, Dr Churchland showed a hilarious "training" montage accompanied by the song The Eye of the Tiger). After showing video of the rat performing the necessary tasks, Dr Churchland called for a volunteer from the audience, and a game fellow named Issac was brought up to the stage to undergo the same "test" as the rats. He scored a whopping 85% success rate, better than any rat. For his efforts, Dr Churchland awarded him with a packet of string cheese.
Of course, studying behavior is only the first step in the "journey"- imaging of the brain was conducted while the rat was engaged in the decision making process. To supplement brain imagine, tetrodes fifteen microns in diameter were placed in the rats' skulls to measure neural activity. There was evidence of neurons firing in the posterior parietal cortex, which is imaged in this video, which indicates that the PPC plays a role in decision making.
In the Q&A some bastard in the audience asked Dr Churchland how the rats dealt with conflicting stimuli, say a high rate visual stimulus combined with a low rate auditory stimulus. She indicated that, in the case of conflict stimuli, the more reliable stimulus was the basis of the decision- a bright visual stimulus would be weighted more heavily than a low auditory stimulus. Another questioner in the audience asked about the role of glia in the brain, and Dr Churchland indicated that the glia play a "scaffolding" role- they help to define the structure of the brain.
Once again, last night's lecture was another triumph of the Secret Science Club. Dr Churchland gave a great presentation about the workaday aspects of a scientist's research, and gave a wonderful view into the efforts to increase our knowledge about the "divide" between simple reflexive behavior and complex behavior. For a brief taste of the subject of the lecture, here's a video of Dr Churchland discussing research that she had conducted using primates as subjects: