The Georgia Health Sciences University Animal Behavior Center has considerable experience testing the short-term memory and attention capabilities of non-human primates. Testing programs are available to GHSU faculty on a collaborative basis, and they are available for contractual agreements with pharmaceutical companies and other external research programs.
Short-term memory and attention capabilities are similar in their (1) neuroanatomical underpinnings, (2) neurochemical regulation, and (3) relevance to a discrete set of human diseases such as Alzheimer's Type Dementia (ATC), attention-deficit hyperactivity disorder (ADHD), and schizophrenia.
A wealth of behavioral data in this area has been documented using delayed-response tasks. Elderly humans perform markedly worse than young subjects on mnemonic facets of such tasks and are more distraction-prone while taking the tests. ATD patients display similar, but more dramatic, memory and attention impairment and both ADHD and schizophrenic patients perform consistently worse on such tasks than their age-matched controls.
Delayed-response testing is a well-established means of examining neurochemical, neuroanatomical and therapeutic aspects of ATD, ADHD and schizophrenia. Behavioral paradigms at the Animal Behavior Center are designed around an automated delayed-response task assessing the function of mnemonic and attention processes. Particularly significant is the fact that each paradigm differs regarding the relative emphasis on these two different, yet interdependent, cognitive constructs.
The Animal Behavior Center also is experienced in stereotaxic implantation of intracranial electrodes and cannulas in rodents and non-human primates.
The basic approaches and procedures of the Animal Behavior Center include:
Delayed Matching-to-Sample (DMTS)
Testing sessions consist of 96 trials five days a week. Test panels, attached to subjects' home cages, have disks that flash red, green and yellow. To begin the test, a sample key is illuminated by one of the colored lights. The sample remains illuminated until the animal responds to the sample key. When the animal presses the key, the light disappears and initiates one of four pre-programmed delay intervals, during which no keys are illuminated. Then, two lights located below the sample key are illuminated. One is the color of the original sample light; the other is a different color. The key remains illuminated until the animal presses a key. If he presses the matching color, he is rewarded; if not, a new trial begins. Delays between illuminating the sample and choice lights vary from 0 to 160 seconds, depending on the skill of the animal and purpose of the test; for instance, DMTS can test not only memory, but also attention by varying the delay interval. Aged rhesus monkeys (20-45 years old) are significantly impaired in DMTS performance compared with younger animals. View how the standard DMTS task works.
DMTS With a Distractor During the Delay Interval
During this test, a random array of flashing colored lights appears on the test panel for a pre-programmed duration during the DMTS delay interval to assess the animal's ability to ignore irrelevant stimuli and retain the information needed to succeed in the test. Aged monkeys perform more poorly on this test and are more distractable than younger monkeys. A significant advantage of this automated distraction paradigm is that, while performing the task, subjects are not exposed to experimenters or other extraneous stimuli, improving experimental control. Drugs used clinically for the treatment of ADHD significantly reverse the distractor-medicated impairment of DMTS performance in monkeys.
DMTS With a Titrated Delay Interval
Another DMTS variation is to titrate the delay interval in response to the monkey's ongoing ability to accurately retain and recall information. In this test, delay intervals are not pre-programmed; the delay interval is determined by a monkey's response to a previous trial. Intervals following a correct match increase in duration so that highly successful monkeys operate at longer delay intervals than less successful monkeys. This test has the advantage, particularly in testing the effects of chronic drug administration, of providing a very selective and sensitive measure of a monkey's maximal performance level over time. Performance can be measured by a single statistic, such as average length of delay interval per session, number of trials to maximal delay and/or duration of maximal delay interval on which performance was significantly greater than chance.
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All of our protocols have been approved by our institutional animal assurances committee and conform to all federal standards for the physical and psychological care and well being of non-human primates.