Sustained Visual Attention Performance-Associated Prefrontal Neuronal Activity: Evidence for Cholinergic Modulation

Abstract

Cortical cholinergic inputs are hypothesized to mediate attentional functions. The present experiment was designed to determine the single unit activity of neurons within the medial prefrontal cortex (mPFC) of rats performing a sustained visual attention task. Demands on attentional performance were varied by the presentation of a visual distractor. The contribution of cholinergic afferents of the mPFC to performance-associated unit activity within this area was determined by recording neuronal activity before and after unilateral cholinergic deafferentation using intracortical infusion of the immunotoxin 192 IgG-saporin. Presentation of the visual distractor resulted in a decrease in the detection of brief, unpredictable visual signals. As predicted, the unilateral loss of cholinergic inputs within the recording area of the mPFC did not affect sustained attentional performance. Cholinergic deafferentation, however, resulted in a decrease in the overall firing rate of medial prefrontal neurons and a substantial reduction in the proportion of neurons whose firing patterns correlated with specific aspects of behavioral performance. Furthermore, cholinergic deafferentation attenuated the frequency and amplitude of increased mPFC neuronal firing rates that were associated with the presentation of the visual distractor. The main findings from this experiment suggest that cholinergic inputs to the mPFC strongly influence spontaneous and behaviorally correlated single unit activity and mediate increases in neuronal activity associated with enhanced demands for attentional processing, all of which may be fundamental aspects in the maintenance of attentional performance.

The Pharmacological Characterization of Attentional Processes Using a Two-lever Choice Reaction Time Task in Rats.

“…Behavioral studies with experimental animals demonstrated that some neurotoxin lesions of the basal forebrain-cortical cholinergic system induced profound deficits of attentional processes in a five-choice serial reaction time task, and scopolamine, a muscarinic receptor antagonist, but not mecamylamine, a nicotinic receptor antagonist, impaired attentional processes. 9,[17][18][19][20] Thus these facts suggest that the cholinergic system, especially muscarinic receptors, may be essential for attention and arousal. The low dose (0.3 mg/kg) of methamphetamine significantly shortened the CRT, in agreement with the findings of a previous study.…”

Vigilance, alertness, or sustained attention: physiological basis and measurement

“…There is some conflicting data on whether there is a significant cholinergic effect on sustained attention (Dalley et al, 2004;Gill et al, 2000;Grottick et al, 2003). The cholinergic system has a direct impact on EEG, with cholinergic activity in cortex being related to wakefulness and desynchronization of the EEG (Celesia and Jasper, 1966;Vanderwolf and Robinson, 1981).…”

Null Mutation of the Arginine-Vasopressin Gene in Rats Slows Attentional Engagement and Facilitates Response Accuracy in a Lateralized Reaction Time Task

“…The divided and/or sustained aspects of visual attention are thought to depend upon dorsal frontal cortical regions and the inputs of these structures to the striatum (Buchsbaum et al, 1990;Burk and Mair, 2001;Christakou et al, 2001;Gill et al, 2000;Muir et al, 1996;Passetti et al, 2000), while the initiation and selection of appropriate responses depend upon striatal circuitry and its modulation by dopamine (Brown and Robbins, 1989;Carli et al, 1985Carli et al, , 1989. In rodents and primates, there is no vasopressin input to these forebrain regions (Wang et al, 1997;Young et al, 1999), suggesting that the effects of vasopressin are indirectly mediated by other neuronal systems, such as monoaminergic and/or cholinergic nuclei (Boer et al, 1995;Caffe et al, 1985;Feenstra et al, 1990).…”