http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:7853 Cholinergic neurotransmission has been implicated in memory and attention. We investigated the effect of the non-competitive nicotinic antagonist mecamylamine on three components of attention processes (i.e. alerting, orienting and executive control) in 12 healthy male subjects whilst performing the Attention Network Task (ANT) in a magnetic resonance imaging (MRI) scanner. Participants received 15 mg mecamylamine in a single blind and placebo- controlled randomized procedure 90 min prior to obtaining functional MRI data. Our results confirm previous reports of beneficial effects of cueing (alerting and orienting) and detrimental effects of conflict (executive control) on reaction times when performing the ANT. The functional MRI data confirmed distinct neural networks associated with each of the three attention components. Alerting was associated with increased left temporal lobe activation while orienting increased bilateral prefrontal, right precuneus and left caudate activation. Executive control activated anterior cingulate and precuneus. Mecamylamine slowed overall response time and down-regulated brain activation associated with orienting and to some extent brain activation associated with executive control when compared to placebo. These findings are consistent with nicotinic modulation of orienting attention by cueing and executive control when responding to conflicting information. The latter nicotine antagonist effect may be mediated via cholinergic modulation of dopamine neurotransmission in mesolimbic pathways. 2011-06-06T06:20:29.240Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:7855 Acetylcholine plays a major role in mediating attention processes. We investigated the muscarinic antagonist effect of scopolamine on functional neuro-anatomy of attention and cognition. We assessed 12 healthy volunteers while performing the Attention Network Task on 0.4 mg scopolamine and placebo in a single-blind randomized trial in a 1.5 T magnetic resonance scanner. Neurocognitive measures included verbal learning, verbal memory, verbal fluency, trail making, digit span, a continuous performance task and a planning task (Tower of London). When compared to placebo, scopolamine increased reaction times for conflicting stimulus processing, together with decreasing brain activation in the anterior cingulate cortex (a brain region involved in conflict processing) suggestive of a muscarinic antagonist effect on executive control of attention. Contrary to the notion of a predominantly right-hemispheric lateralization of cognitive processes associated with orienting attention, scopolamine reduced brain activity in left superior and left middle frontal brain areas. Our neuropsychological test data revealed a selective effect of scopolamine on verbal learning and memory while other cognitive domains, such as planning and working memory, were unaffected. These findings are consistent with muscarinic modulation of dopaminergic neurotransmission in frontal attention networks when processing conflicting information. 2011-06-06T06:20:08.144Z ]]>