Cholinergic neurons, learning, and recovery of function.

Abstract

Two experiments were designed to examine the role of the cholinergic septo-hippocampal projection in spatial and nonspatial learning processes. In Experiment 1 the interaction of individual learning strategies and recovery of function was investigated following medial septal lesions, by assessing individual learning styles and number of trials to recovery on a standard radial eight-arm-maze task. Experiment 2 addressed the relevance of the cholinergic septo-hippocampal pathway in the acquisition of spatially mediated behavior, by employing medial septal lesions, prior to acquisition learning of a modified version of the radial eight-arm-maze task. The data from these two experiments demonstrated that (a) the cholinergic septo-hippocampal projection is important for the acquisition and maintenance of spatial learning strategies, (b) loss of cholinergic function leads to alteration of learning strategies, (c) different learning strategies can be employed to acquire the same behaviors, and (d) the rate of recovery following brain injury can be influenced by preoperative learning strategies.

Plasticity in the Rat Hippocampal Formation following Ibotenic Acid Lesion of the Septal Region: A Quantitative [14C]Deoxyglucose and Acetylcholinesterase Study

“…This observation, and the still decreased AChE staining of the dorsal hippo campus in the 90-day group compared with con trols, provide substantial support for the hypothesis that collateral and sympathohippocampal sprouting could not restore the normal functional activity af ter partial deafferentation. Our results corroborate experiments in which rats demonstrated impair ments 4-6 months after fimbria/fornix transections in spatial learning and working memory (Harrell et al, 1987;Nilsson et al, 1987). The present results provide a further indication that partial structural recovery in the CNS occurs in parallel with partial recovery of function .…”

Fluid Percussion Injury Causes Loss of Forebrain Choline Acetyltransferase and Nerve Growth Factor Receptor Immunoreactive Cells in the Rat

“…In this experiment, we chose to examine the MSN/vnDBB cholinergic neurons because these neurons are thought to play a major role in memory (Harrell et al, 1987). These neurons are consistently deleted in the pathologic analysis of brains from patients with Alzheimer's disease (Davies and Maloney, 1976;Whitehouse et al, 1982;Arendt et al, 1985), a possible explanation for the memory deficits exhibited by Alzheimer's patients.…”

“…The anatomic substrate of memory has been the subject of intense investigation. Neurons located in the hippocampus and ventral forebrain are believed to be partly responsible for spatial memory (Harrell et al, 1987). FPI, an experimental model of TBI, causes working and spatial memory deficits in rats (Lyeth et al, 1990;Smith et al, 1991;Gorman et al,1993).…”

Cholinergic Modulation of Cerebral Cortical Blood Flow Changes Induced by Trauma

“…There is increasing evidence for an important role of cholinergic mechanisms in the control of CBF Kuschinsky et al, 1974;Rovere et al, 1973;Kawamura et al, 1975;Molnar et al, 1991;Dauphin et al, 1991;Scremin, 1991), as well as in processing of sensory information (Metherate et al, 1987;Metherate et al 1990), cortical organization of movement (De Ryck et al 1990), and cognitive function (Luine and Hearns, 1990;Dawson et al, 1991;Chrobak et al, 1988;Harrell et al, 1987;Berger et al, 1979;Bartus et al, 1982). The present investigation was undertaken to test the hypothesis that enhancement or blockade of central cholinergic transmission could alter the CBF patterns associated with traumatic brain injury (TBI).…”