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Role of medial septum-diagonal band of Broca neurons in cognitive flexibility

Pang K, Janke K, Servatius RJ (2008) Role of medial septum-diagonal band of Broca neurons in cognitive flexibility. Neuroscience 2008 Abstracts 89.20/SS37. Society for Neuroscience, Washington, DC.

Summary: Cholinergic and GABAergic neurons are major components of the septohippocampal pathway, and comparisons between the two neuronal populations are important for understanding the function of medial septum and vertical limb of the diagonal band (MSDB). Recently, we have been investigating the importance of MSDB neurons in cognitive flexibility. Cognitive flexibility is commonly examined in procedures that require reversal of stimulus-reward associations and those that require shifts in attention set, involving switching attention to different stimulus dimensions. Our recent studies demonstrated that selective damage of GABAergic but not cholinergic MSDB neurons impaired spatial reversal. The present study will determine whether selective lesions of cholinergic or GABAergic MSDB neurons impairs shifting of attentional set. Sprague Dawley rats will be administered saline, GAT1-saporin or 192-IgG saporin into the MSDB to produce no damage, selective GABAergic damage or selective cholinergic damage, respectively. Verification of the lesions will be performed using immunocytochemistry at the end of the study. The behavioral procedure will occur in a plus maze. Rats will start in one of two arms opposite each other (i.e., north and south arms) randomized across trials. On any single trial, the arm opposite the starting arm will be blocked forming a T-maze. Rats will have a choice of entering one of the remaining 2 arms (east or west arms) for food reinforcement. Half of the rats will be reinforced to make an egocentric response (left or right turn) and the other rats will be reinforced to go to a particular arm (east or west; allocentric response) regardless of starting location. After reaching criterion (10 consecutive correct choices), the goal location will be reversed (i.e., left turn to right turn or east to west arm) or shifted to a different dimension (i.e., left turn to east arm or west arm to right turn). It is expected that rats treated with GAT1-saporin, but not 192-saporin, will be impaired on the reversal procedure, similar to previous studies. Impairments in shifting attention set would suggest a global impairment in cognitive flexibility. However, an impairment in the reversal procedure but not shifting of attention set would be similar to recently described deficits in the nucleus basalis magnocellularis using ibotenic acid and 192-IgG saporin lesions (Tait and Brown, Behav Brain Res. 187:100, 2008). The results of this study will provide important insight into the role of the MSDB in learning, attention and cognitive flexibility.

Related Products: 192-IgG-SAP (Cat. #IT-01), GAT1-SAP (Cat. #IT-32)

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