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Unilateral lesions of the medial agranular cortex produce a persistent disruption in the organization of food protection behaviors

S. J. WAGNER, M. J. HYLIN, M. M. MARTIN, S. S. WINTER, K. J. BURCHAM,L. M. MCFADDEN, J. V. CORWIN, D. G. WALLACE

Dept Psychology, Northern Illinois Univ., DeKalb, IL, USA

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Seven adult male Long-Evans rats, approximately 90 days old, were housed in pairs and maintained at 90% of free feeding weight. Prior to testing, rats were habituated to an arena and honey roasted almonds for one week. After habituation, rats were tested to establish a baseline. During all sessions, rats were given five trials (one almond/trial). For the first four trials, the dodger consumed the food item in the presence of its cage mate (i.e., the robber). If the food item was taken away by the robber, the experimenter removed the robber from the arena, retrieved the food item, gave it back to the dodger, and placed the robber back in the arena. During the fifth trial, the time required to consume the almond in the absence of the robber was measured after each session. Following pre-testing, rats were randomly assigned to either an AGm aspiration lesion (n=4) or a control (n=3) group. Several measures were used to quantify the organization of food protection behaviors.

Figure 2: Coronal sections stained with cresyl violet from representative control (left) and AGm (right) rats.AGm lesions use the following coordinates: +5.0mm to -2.5 mm A.P. relative to bregma, 2.5mm from the midline.Rats use both external and internal sources of information to organize their

food protection behaviors. Although previous studies have demonstrated that hemidecortication or cholinerergic deaffentation of the cortex disrupts the ability to protect food from an approaching conspecific, as of yet, no studies have examined the effects of more localized lesions. Past findings have characterized the medial agranular cortex (AGm) as a multimodal association area in rats that when damaged, produces deficits in orientation behavior. The current study examined the contribution of the AGm to the organization of food protection behavior.

Acknowledgments: Bethany Barnes

Correspondence:

Steve Wagner sjwagner111@hotmail.com

J. V. Corwin jcorwin@niu.edu

D.G. Wallace dwallace@niu.edu

Web: www.niu.edu/user/tj0dgw1

Figure 1: Dodging behavior was video recorded from an angled mirror. Rats were placed in the plastic cylinder (45 cm in diameter and 61cm in height) that was positioned on a glass shelf (left photo). A digitized representation of a brace and a dodge is provided (right illustration) in which the robber is characterized in red, and the dodger is in blue.

Figure 7: Individual percentage of successful food protection behaviors are plotted for pre-testing, acute, and protracted testing (top). Average percent food protection behaviors are plotted for each phase of testing (below). AGm animals displayed a unilateral deficit during the acute testing phase which transitioned to a bilateral deficit during the protracted phase.

89.5/SS22

Abstract

Methods

Results

ConclusionsFigure 6::There were no group differences observed during pre-testing; however, rats with AGm lesions were significantly less successful in protecting the almond at acute and protracted testing.

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Rats that received AGm lesions had significant impairments in protecting the food item from the robber relative to control rats.

This impairment was initially lateralized in the acute phase The impairment became bilateral at protracted time points

There were no differences in rates to consume the food items between groups during pre-testing, acute and protracted time points.

This implies the disruption in food protection was not mediated by motivational factors

These results may suggest a role for the AGm in the organization of food protection behavior, and they may represent a novel assessment technique for therapeutic interventions related to deficits induced by stroke or neurodegenerative disorders.

Figure 3: No group differences were found in rats’ consumption times during pre-testing, acute, and protracted testing.

Figure 5: The robbers’ approaches were equally distributed across each side for both groups.

Figure 4: There were no group differences in the total food protection behaviors observed across pre-testing, acute, and protracted testing.