Psychological and Brain Sciences Brown Bag Seminar: Matthew Broschard
Psychological and Brain Sciences Departmental Brown Bag Seminar
Matthew Broschard, Neuroscience of Learning Lab, Psychological & Brain Sciences, The University of Iowa
"Role of the Prefrontal Cortex in Visual Category Learning"
Abstract: The COVIS (COmpetition between Verbal and Implicit Systems) model postulates two systems in human category learning. The declarative system uses the prefrontal cortex (PFC) to learn rule-based (RB) category tasks in which there is one relevant sensory dimension that can be used to establish a category rule, whereas the procedural system uses corticostriatal circuits to learn information integration (II) tasks in which multiple dimensions are relevant. Humans and monkeys, but not pigeons, learn RB tasks faster than II tasks. The absence of a learning rate difference in pigeons has been attributed to their lacking a PFC. A major gap in this comparative analysis, however, is the lack of data from a non-primate mammalian species, such as rats, that have a PFC but a less differentiated PFC than primates. We first trained rats to learn RB and II tasks to see whether this learning advantage extents to non-primate mammals. Similar to pigeons, no differences in learning rate and category generalization were observed between RB and II groups, highlighting the limitations of executive function in rats. However, fitting the Generalized Context Model (GCM) to the data revealed that rats used selective attention to learn the RB tasks but diffuse attention to learn the II tasks. Furthermore, lesions of the medial PFC in rats impaired learning, generalization, and rule switching for only RB tasks. The findings suggest that rats have a PFC-mediated learning system that uses selective attention, but this system is limited compared to primates. Investigating this system may provide insight regarding the functional similarity and shortcomings between rodent and primate PFC.