Nikolaos Aggelopoulos

Cholinergic effects on cognition in the primate brain

Introduction and Scientific Aims

Acetylcholine is a neuronal transmitter and neuromodulator that has documented effects on attentional tasks [1, 2] via muscarinic receptors [3]. Muscarinic receptors are also believed to have a role in cortical plasticity [4]. The aim of this project is to demonstrate the effects of the muscarinic antagonist scopolamine in a categorization task involving attention and learning.

Methods

Two monkeys have been fully trained using operant conditioning in a categorization task to use levers to indicate which category a stimulus belongs to. Muscarinic mechanisms were antagonised by systemic administration of scopolamine. Neurons of the basal cholinergic forebrain nuclei were identified prior to their stimulation in order to test the role of cholinergic mechanisms in cortical plasticity during this task.

Results and preliminary conclusions

The categorization of novel stimuli, that is the ability to assign a new stimulus to a category, was impaired by a muscarinic receptor block (Aggelopoulos et al, 2011). Neuronal recordings from the basal cholinergic forebrain have revealed neurons with a capacity to respond to a great range of visual stimuli, including also non-coherent images, that were paired with a reward.

Supervised students and collaborators

Alexander Rauch, collaborator; Ceren Batal, Master student on a lab rotation

Fig.1. Novel stimuli were presented varying in coherence (examples on the left panel). The categorization of novel stimuli was impaired by a muscarinic receptor block by scopolamine (cyan curve, right).

References

1. Sarter, M., Bruno, J.P. Neuroscience 95, 933-952 (2000) .

2. Furey, M.L. et al Neuropsychopharmacology 33, 913-923 (2008).

3. Herrero, J.L., et al Nature 454, 1110-1114 (2008)

4. Miasnikov AA, McLin D 3rd, Weinberger NM. Neuroreport. 12, 1537-42 (2001).

5. Aggelopoulos NC, Liebe S, Logothetis NK & Rainer G: Frontiers in Behavioral Neuroscience 5(73):1-10 (2011)