Butt AE, Kinney-Hurd BL, Flesher MM, Amodeo DA, Horn LR, Greenfield V, Lladones R, Hernandez G, Loson L (2008) Selective cholinergic lesions of the nucleus basalis magnocellularis disrupt attention in appetitive trace conditioning. Neuroscience 2008 Abstracts 686.14/SS65. Society for Neuroscience, Washington, DC.
Summary: Pavlovian trace conditioning, but not delay conditioning, is a form of declarative memory that requires attention and depends on the medial prefrontal cortex and hippocampus. We have previously shown that selective lesions of the cholinergic basal forebrain projections to the neocortex and to hippocampus disrupt trace conditioning but not delay conditioning. The current experiment examines the contribution of the cortical cholinergic projections of the nucleus basalis magnocellularis (NBM) to the behavioral impairments previously observed following complete basal forebrain lesions involving both the NBM and the hippocampally-projecting medial septum (MS). We hypothesized that selective lesions of the cholinergic NBM neurons would disrupt trace conditioning in a manner similar to that observed following basal forebrain lesions. Additionally, because cholinergic modulation of prefrontal cortex mediates attention in other tasks, we hypothesized that increasing demands on attention in trace conditioning would exacerbate NBM lesion-induced impairments. Rats with bilateral 192 IgG-saporin lesions of the NBM and sham lesion control animals were tested in the trace conditioning paradigm either in the presence or absence of an attention-demanding visual distractor (intermittent, unpredictable flashing light). Rats received 60 trials per day for 10 days, where each trial consisted of a 10 s white noise CS, followed 10 s later by the delivery of a sucrose pellet unconditioned stimulus (US). Conditioned responding was assessed by measuring approach to the food cup. Approach during the CS itself was considered to be non-adaptive, while approach during the trace interval was classified as adaptive responding. Contrary to our hypothesis, results showed that NBM lesions failed to impair acquisition of trace conditioning in the absence of additional attentional demands. These findings suggest that the trace conditioning impairment previously observed following complete basal forebrain lesions were due either to damage to the hippocampally-projecting MS or to a cumulative effect of combined NBM and MS damage. The presence of the visual distractor, however, disrupted acquisition performance in the current experiment as hypothesized. The NBM lesion group in the distracted condition showed excessive non-adaptive responding during CS presentation as compared to controls. The increased attentional load caused by the visual distractor appears to have caused a disinhibition of non-adaptive responding in the NBM lesion group. These results suggest that cholinergic modulation of neocortex is involved in mediating attention during trace conditioning.
Related Products: 192-IgG-SAP (Cat. #IT-01)