Researchers in Stone Professor of Psychology Douglas A. Weldon's laboratory are studying the neurophysiological basis of attention this summer. For this experiment, Aliscia Thomas '04 and Matthew Silver '05 will monitor rats performing behavioral tasks in order to observe the activity of single neurons in an area of the midbrain called the superior colliculus. Using computer programs, the researchers will then determine correlations between neuronal activity and particular behavioral events.
The superior colliculus is involved in attentional processing. This area of the brain has anatomical connections with other brain locations to allow it to retrieve sensory information to send to motor systems in order to produce coordinated orientation movements. Over the past several years, Weldon and a series of Hamilton students have determined that neurons in the rat superior colliculus show bursts of activity when the animals receive reward in a behavioral task. The present study is a continuation of the senior project research conducted by Jennifer DiNieri '03. It is designed to determine whether that activity is related to sensory stimulation or motor behaviors associated with the task, or whether it reflects some higher processing involved in responding to the reinforcement. According to Weldon: "The properties of neurons are dynamic and change their function as animals encounter significant events in their environment. We are documenting these changes in an attempt to understand attentional processing in the mammalian nervous system."
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Aliscia and Professor Weldon |
Each rat is trained in a variable ratio operant conditioning task that involves pushing down a bar and inserting the snout in a food cup. During half of the trials, a pellet of food falls down a slide into the food dish. When the rat sticks its nose into the food dish, a sensor triggers an auditory cue, and on some trials a puff of air is presented to the rat's nose. Neural activity is recorded in response to each of the rat's actions throughout the experiment. By requiring the animal to make equivalent movements in the presence and absence of reward, the experiment will be able to dissociate the movements involved in the task from the processing of the presence of the reinforcement. Similarly, since some trials involve extra tactile stimulation (the puff of air) while others do not, it will be possible to determine whether the neurons show an increase in sensitivity to touch in the presence of the reinforcement.
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| Professor Weldon and Matt working with the data. |
Thomas and Silver are both involved in all aspects of the research; both are involved in training the animals, collecting the data and performing the computer analyses. In general, Thomas has become the expert at constructing the microelectrodes used to record the neuronal activity. Silver has been using his skills in computer programming to work on upgrading the existing programs to control the experimental equipment and analyze data.
Silver is majoring in neuroscience. His work is funded by the Dean's Summer Research Fund. Thomas is also majoring in neuroscience. She received a stipend from the GE Fund. The GE Fund supports summer research for minority students and women in under-represented areas of the sciences and mathematics at Hamilton College.
