User:Niubrad

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I'm a neurobiology grad student at San Diego State University. I am currently doing research with mirror neurons, using functional MRI scanning techniques. I also work in a teratology lab where we look for treatments for fetal alcohol spectrum disorders.

Wikipedia is my friend.

Over the past century scientists have made significant progress in developing theories of why humans think, act, and feel the way they do. Our understanding of behavior and cognition can be thought of as series of discoveries that have helped to bridge the gap between what we know, what we predict, and what we observe. Psychology is a relatively new science, partially do to the complex nature of the human mind, and until recently the physical apparatus of the brain was largely excluded from texts equating behavior and cognition. The separation between mind and body, however, would not remain and as new discoveries surfaced, the gap between psychologist and biologist became less distinct. Neuroscience laid the foundation for a new paradigm of psychology that began the arduous task of understanding the complexities of the human brain. Aided by advanced technology, we are now able to “look” inside of the brains of living organisms (including humans) while they think and act just as they would in everyday life. So what was once considered an extraordinary pursuit, is now being pushed farther than we could have ever anticipated only 20 years ago. While traveling the world, one can find extraordinary diversity in the experiences in which they partake; on the other hand, the people whom they encounter are remarkably similar. They are curious; they strive for love and acceptance, and feel pain when removed from such necessities. They look after one another, and have a strong devotion to justice. Yet, they will also do harm for power and resources, and discriminate against others that belong to a group they do not identify with. I ask myself how individuals can be so similar, yet display such variability in their actions. When are such behaviors a product of the environment and what is biology's roll in these actions? So when considering the topic for this essay, I aimed to explore an area of neuroscience that investigates the neural correlates of understanding one another. The following review will cover two fairly new discoveries in the world of neuroscience; mirror neurons and place cells. Along with defining the anatomy and function of these two neurological entities (NEs), the text will cite examples of cases where these structures become damaged or disabled, in order to give the reader a broader scope of how they work. The common thread between these two NEs is their ability to account for specific behavioral phenomena on a cellular level, a concept that has been met with both inquiry and reservation. Some researchers have qualms (many of them justified) about the precise nature of explaining the complexities of behavior with such a reductionist approach. Nevertheless, they pose an exciting question for future research; can we understand behavior by studying individual neurons? Mirror neurons were first discovered in area F5 of the macaque monkey premotor cortex in a somewhat serendipitous fashion. DiPellegrino (1992) quite candidly sums up the unexpected findings in his write-up about the experiment, which took place in the Rizzolatti lab in Parma, Italy:

Our original aim in the present experiment was to study the activity of F5 neurons in a behavioral situation in which we could separate stimulus-associated responses from the activity related to movements. For this purpose a macaque monkey was trained to retrieve objects of different size and shape from a testing box with a variable delay after a stimulus presentation. After the initial recording experiments, we incidentally observed that some of the experimenter’s actions, such as picking up the food or placing it inside the testing box, activated a relatively large proportion of F5 neurons in the absence of any overt movement of the monkey. The purpose of this communication is to describe some of the essential features of this surprising new class of premotor neurons.

What they had found was a link between an executed behavior and the ability to recognize the identical behavior performed by another individual. More precisely, specific neuronal excitations were recorded by an implanted microelectrode when a monkey performed a particular action (i.e. reaching to grab a peanut); the very same neuron would excite the electrode when the monkey observed the same action performed by another individual (DiPellegrino et al.1992). Since the initial discovery of these visuomotor F5 neurons, much work has been done in order to elucidate their specific properties. Two types of visuomotor neurons, canonical and mirror, have been defined by Rizzolatti and Luppino (2001). Canonical neurons were shown to respond when a monkey is presented with an object, and mirror neurons responded when the monkey witnessed an object-directed action. Mirror neurons are subsequently divided into two types: strictly congruent, in which the same neuron fires during the observation of an action and execution of the same action, and broadly congruent which are neurons that fires during the observation of an action but do not necessarily fire for the execution of the same motor performance (do not confuse with canonical which fire upon viewing and object and broadly congruent which fire upon viewing an action) (Gallese et al. 1996). Kohler and colleagues (2002) report that mirror neurons can recognize a given movement made by a demonstrator even when the monkey is unable to see part of the movement. A neuron responds when a demonstrator reaches for an object; however when the demonstrator reaches for nothing, the neuron will not respond. Interestingly, when an object is hidden behind a screen, and the researcher reaches behind the screen, the neuron will respond even though the subject could not see what was happening behind the screen. Premotor mirror neurons can reason in this way, meaning that the motor representation of an action performed by others can be internally generated, even when the visual description of the action is incomplete (Umilta et al. 2001). Such a result suggests that mirror neuron activation could be at the root of action recognition. Mirror neurons are specialized to respond only when a biological effector (such as a hand or mouth) interacts with an object, and will fail to respond at the sight of an object alone, the interaction between two non-biological objects (such as a pincher grabbing a ball), or a biological effector performing actions that are not object oriented (such as reaching for an object that isn’t there) (Rizzolatti & Craighero, 2004). The exclusive role of responding to biological effector may provide evidence that mirror neurons mediate action understanding, that is, the understanding of others behavior: Buccino (2003) points out that each time an individual sees an action done by another individual, neurons representing that specific action are activated in the observer’s premotor cortex. This automatically induced motor representation of the observed action corresponds to that which is spontaneously generated during active action and whose outcome the acting individual knows. Thus, there is a good chance that the mirror system transforms visual information into knowledge (Rizzolatti et al 2001). It may be a portentous claim that DiPellegrino makes regarding these findings as evidence that premotor neurons can retrieve movements not only on the basis of stimulus characteristics, but also on the basis of the meaning of the observed actions. However, the notion that communicative actions derived from object-directed actions is not a new one. Vygotski (1934) postulates that the evolution of pointing movements was a likely derivative of attempts of children to grasp objects out of reach. And, as Kohler demonstrated, mirror neurons discharge only when the monkey feels that the action has a purpose. Even when the object is hidden behind a screen, the neuron will discharge, thus breaking spatial relations between the target and the effector. If spatial relationships are insignificant in the ability to understand the meaning of an action, the precondition for understanding pointing is a capacity already present in the primate lineage.

Bibliography:

Di Pellegrino, G., Fadiga, L., Fogassi, L., Gallese, V., & Rizzolatti, G. (1992) Understanding motor events: a neurophysiological study. Exp Brain Res, 91 176-180

Rizzolatti, G., Luppino, G., (2001). The cortical motor system. Neuron 31:889–901

Rizzolatti, G., Craighero, L., (2004). Review: The mirror-neuron system. Annu Rev Neurosci. 27:196-192

Gallese, V., Fadiga, L., Fogassi, L., & Rizzolatti, G. (1996). Action recognition in the premotor cortex. Exp Brain Res, 119. 593-609

Umilta, M. A., Kohler, E., Gallese, V., Fogassi, L., & Fadiga, L. (2001). I know what you are doing: A neurophysiological study. Neuron, 32. 91-101

Kohler, E., Keyseres, C., Umilta, M. A., Fogassi, L., Gallese, V., & Rizzolatti, G. (2002). Hearing sounds, understanding actions: action representation in mirror neurons. Science, 297. 846-848