Efficient attention to our environment facilitates the decisions that need to be executed in daily life. Filtering critical from noncritical information may require the neural organization of multiple brain regions. Combining lesion techniques and the rodent version of the Wisconsin card sorting task in humans, we show at least two types of attentional processing systems reside in the cingulate and prefrontal cortices depending on task demands requiring shifts of attention within or between sets of meaningful cues, respectively. This neural organization for shifting attention either within or between perceptual dimensions is task dependent, and this type of organization provides evidence of attentional systems that transcend separate modality processing systems while subdividing executive control of attention. The results suggest that the anterior and posterior cingulate cortices are critical when shifting attention to closely related meaningful cues (i.e., within a perceptual dimension or attentional set) by suppressing interference of irrelevant background information, whereas the prefrontal cortex is critical when shifting attention between disparate sets of meaningful cues (i.e., between perceptual dimensions or attentional sets) (Dias et al., 1996a,b; Birrell and Brown, 2000). Based on the theories of Mackintosh (1965Mackintosh ( , 1975; Sutherland and Mackintosh 1971), it is suggested that the cingulate cortex may be important for decreasing attention to irrelevant information. In general, attention deficit disorders affect both children and adults, and current medications may affect the prefrontal and associated parietal cortical systems more or less than the cingulate cortical system.

Calcium elevations after neurotrauma are not only implicated in cell death but may contribute to adaptive plasticity. We now wished to resolve this contradiction by following calcium dynamics after optic nerve crush in vivo. Adult rats received no injury (n = 5), unilateral mild (n = 10) or moderate optic nerve crush (n = 10) (ONC), or axotomy (n = 5). Before surgery, retinal ganglion cells (RGCs) were retrogradely labelled with Oregon Green BAPTA-dextran, a fluorescent calcium marker. Calcium-related fluorescence intensity (FI) was repeatedly measured in individual RGCs in vivo using the in vivo confocal neuroimaging (ICON) method. Four different RGC types were found. Normal RGCs without FI change were found in sham rats and also in both ONC groups. RGCs with mild damage were seen only after mild ONC, showing an initial calcium depression of 26% at day 4 followed by a 169% increase 15 days after ONC. RGCs with moderate damage were found only after moderate ONC and showed calcium hypoactivation followed by a slower return toward baseline and a delayed calcium increase of 72% above baseline. Sixty to sixty-five per cent of the RGCs in both ONC groups and all RGCs in the axotomy group died within 6 days following a fast and massive calcium increase of 316% with a concomitant 156% soma size increase. In conclusion rapid calcium elevation leads to cell death, while an initial calcium depression followed by a delayed and moderate calcium hyperactivation is associated with cell survival. We propose that immediate, massive calcium activation is maladaptive whereas delayed and moderate hyperactivation of surviving cells is adaptive. Implications for pharmacotherapy are discussed.

The basal ganglia (BG) network has been divided into interacting actor and critic components, modulating the probabilities of different state-action combinations through learning. Most models of learning and decision making in the BG focus on the roles of the striatum and its dopaminergic inputs, commonly overlooking the complexities and interactions of BG downstream nuclei. In this study, we aimed to reveal the learning-related activity of the external segment of the globus pallidus (GPe), a downstream structure whose computational role has remained relatively unexplored. Recording from monkeys engaged in a deterministic three-choice reversal learning task, we found that changes in GPe discharge rates predicted subsequent behavioral shifts on a trial-by-trial basis. Furthermore, the activity following the shift encoded whether it resulted in reward or not. The frequent changes in stimulus-outcome contingencies (i.e., reversals) allowed us to examine the learning-related neural activity and show that GPe discharge rates closely matched across-trial learning dynamics. Additionally, firing rates exhibited a linear decrease in sequences of correct responses, possibly reflecting a gradual shift from goal-directed execution to automaticity. Thus, modulations in GPe spiking activity are highest for attentiondemanding aspects of behavior (i.e., switching choices) and decrease as attentional demands decline (i.e., as performance becomes automatic). These findings are contrasted with results from striatal tonically active neurons, which show none of these task-related modulations. Our results demonstrate that GPe, commonly studied in motor contexts, takes part in cognitive functions, in which movement plays a marginal role.basal ganglia | learning | attention | globus pallidus | actor-critic model T he basal ganglia have long been implicated in learning new skills and associations (1). One of the most influential models of these structures distinguishes between two domains: the main axis, whose function is to execute and choose between different actions based on their expected outcome, and the neuromodulators, which act to shape the connectivity within said axis by incorporating information regarding the results of actions on the internal and external state. These components are aptly named the actor and critic, respectively (2).The roles of the striatum, the largest structure in the main axis, and dopamine, the key neuromodulator serving as a critic in the basal ganglia framework, have been thoroughly studied. Dopamine modifies the efficacy of the corticostriatal synapses, as well as the striatal excitability directly, using signals that incorporate both expectation and external gains and losses (3-5). Decades of research have revealed the manner in which signals relaying information concerning expected and actual gains and costs are incorporated in the striatal dynamic system (6-9). However, these dopamine-and striato-centric views often fail to take into account our current understanding of the basal ganglia, which ac...

Awareness of its rich structural pathways has earned the external segment of the globus pallidus (GPe) recognition as a central figure within the basal ganglia circuitry. Interestingly, GPe neurons are uniquely identified by the presence of prominent pauses interspersed among a high-frequency discharge rate of 50-80 spikes/s. These pauses have an average pause duration of 620 ms with a frequency of 13/min, yielding an average pause activity (probability of a GPe neuron being in a pause) of (620 × 13)/(60 × 1000) = 0.13. Spontaneous pause activity has been found to be inversely related to arousal state. The relationship of pause activity with behavioural events remains to be elucidated. In the present study, we analysed the electrophysiological activity of 200 well-isolated GPe pauser cells recorded from four non-human primates (Macaque fascicularis) while they were engaged in similar classical conditioning tasks. The isolation quality of the recorded activity and the pauses were determined with objective automatic methods. The results showed that the pause probability decreased by 9.09 and 10.0%, and the discharge rate increased by 2.96 and 1.95%, around cue and outcome presentation, respectively. Analysis of the linear relationship between the changes in pause activity and discharge rate showed r(2)  = 0.46 and r(2)  = 0.66 upon cue onset and outcome presentation, respectively. Thus, pause activity is a pertinent element in short-term encoding of relevant behavioural events, and has a significant, but not exclusive, role in the modulation of GPe discharge rate around these events.

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