Individual differences in the effects of salience and reward on impulse control and action selection.

Impulse control and adequate decision making are vital functions when it comes to detection and adherence to personal goals and societal rules. In the current study we tested the hypothesis that increasing the salience of environmental cues would be most effective in improving impulse control, as assessed by a stop-signal task, in subjects with low environmental susceptibility as indexed by low pre-stimulus EEG alpha power. In addition, we anticipated that an external-reward manipulation improves performance during a Go/No go task, especially in individuals with low task-induced motivation as indexed by low theta/beta power ratios. High salience of stop signals enhanced stopping performance but there was no difference in responsivity to the salience manipulation between participants with high and low EEG alpha power. Individuals with low theta/beta power ratios responded more accurately when rewards were involved. Together these results suggest that increasing the salience of external cues may help impulse control in general, whereas the effectiveness of external-reward manipulations is higher in individuals with low task-induced motivation.

Electromyographic responses to emotional facial expressions in 6-7year olds: a feasibility study.

Preliminary studies have demonstrated that school-aged children (average age 9-10years) show mimicry responses to happy and angry facial expressions. The aim of the present study was to assess the feasibility of using facial electromyography (EMG) as a method to study facial mimicry responses in younger children aged 6-7years to emotional facial expressions of other children. Facial EMG activity to the presentation of dynamic emotional faces was recorded from the corrugator, zygomaticus, frontalis and depressor muscle in sixty-one healthy participants aged 6-7years. Results showed that the presentation of angry faces was associated with corrugator activation and zygomaticus relaxation, happy faces with an increase in zygomaticus and a decrease in corrugator activation, fearful faces with frontalis activation, and sad faces with a combination of corrugator and frontalis activation. This study demonstrates the feasibility of measuring facial EMG response to emotional facial expressions in 6-7year old children.

Evidence for a role of cholecystokinin as neurotransmitter in the guinea-pig enteric nervous system.

Intracellular recordings were made of neurons in the myenteric plexus of the guinea-pig distal ileum. Slow excitatory postsynaptic potentials (sEPSPs) were evoked by electrical stimulation of an interganglionic fibre tract. The effect of cholecystokinin (CCK) receptor antagonists on the sEPSPs was investigated in 11 neurons. Application of the CCK receptor antagonists L-364,718 and L-365,260 (each 250 nM) markedly attenuated the sEPSPs in five of 11 neurons. The amplitude of the sEPSP reduced from 15 +/- 3 to 7 +/- 2 mV and the change in membrane resistance during the sEPSP was reduced from 28 +/- 9 to 11 +/- 8 MS. In six of 11 neurons the CCK antagonists had no effect on the sEPSPs. The results provide evidence that neurally released CCK is involved in the mediation of sEPSPs in some enteric neurons.

CCKA and CCKB receptor subtypes both mediate the effects of CCK-8 on myenteric neurons in the guinea-pig ileum.

The effects of cholecystokinin (CCK-8) on myenteric S neurons were investigated by intracellular recording techniques, with the aim to determine the CCK receptor subtypes involved. CCK-8 (1-1000 nM) evoked concentration-dependent long-lasting excitatory responses in 45 of 54 neurons. CCK receptor antagonists were applied to 15 neurons in which CCK-8 evoked an excitatory response. In 5 of these neurons, application of the CCKA antagonist L-364,718 (100-500 nM) antagonized the action of CCK-8 and the CCKB antagonist L-365,260 (500 nM) had no effect. L-365,260 (100-500 nM) antagonized the CCK-8 induced response in 5 neurons, on which L-364,718 had no effect. In the other 5 neurons each antagonist (500 nM) partly inhibited the CCK-8 evoked excitation and application of both antagonists (500 nM) caused a complete blockade of the response to CCK-8. The selective CCKB receptor agonist CCK-8NS had similar excitatory effects as CCK-8, but only on the neurons in which CCK-8 evoked effects were antagonized by L-365,260. The results demonstrate that the excitatory effects of CCK-8 are mediated by both CCKA and CCKB receptor subtypes. Further, the results indicate that some neurons possess exclusively the CCKA or the CCKB receptor subtype, but others possess both subtypes.

Somal size and location within the ganglia for electrophysiologically identified myenteric neurons of the guinea pig ileum.

The main goal of the present study was to examine the possibility of electrophysiologically identifying the excitable enteric S and AH neurons by use of one single criterion. Intracellular recordings were made from 189 cells of 64 ganglia in isolated preparations of the myenteric plexus of the guinea pig distal ileum. The recordings were made under visual control of the cells by using Hoffman Modulation Contrast optics at high magnification (600x). From photomicrographs, the soma size and the location within the ganglion of the individual (unstained) cells were determined. The cells were classified into three types according to their electrical excitability and the shape of the action potential. Excitable cells were classified as AH cells (n = 84) if the action potential showed a shoulder on the falling phase, otherwise as S cells (n = 56). Cells in which no action potential could be evoked by current injection were classified as nonspiking (NS) cells (n = 49). The three classes of cells showed significant differences with respect to membrane potential, input resistance and fast synaptic input. The AH cells had significantly larger somata (P < 0.01) than the S cells. The NS cells were significantly smaller than the AH and S cells (P < 0.01). AH and S cells were found to be randomly located in the ganglia, whereas the NS cells clustered (P < 0.008) in close proximity to the onsets of internodal strands. We conclude that the shoulder of the action potential can be used as a single criterion to distinguish "on line" S and AH neurons unequivocally.