Journal of neurophysiology
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To provide a fundamental basis for understanding decision-making and decision confidence, we analyze a neuronal spiking attractor-based model of decision-making. The model predicts probabilistic decision-making with larger neuronal responses and larger functional magnetic resonance imaging (fMRI) blood-oxygen-level-dependent (BOLD) responses on correct than on error trials because the spiking noise-influenced decision attractor state of the network is consistent with the external evidence. Moreover, the model predicts that the neuronal activity and the BOLD response will become larger on correct trials as the discriminability ΔI increases and confidence increases and will become smaller as confidence decreases on error trials as ΔI increases. ⋯ In an fMRI study of an olfactory decision-making task, we confirm these predictions for cortical areas including medial prefrontal cortex and the cingulate cortex implicated in choice decision-making, showing a linear increase in the BOLD signal with ΔI on correct trials, and a linear decrease on error trials. These effects were not found in a control area, the orbitofrontal cortex, where reward value useful for the choice is represented on a continuous scale but that is not implicated in the choice itself. This provides a unifying approach to decision-making and decision confidence and to how spiking-related noise affects choice, confidence, synaptic and neuronal activity, and fMRI signals.
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The aim of the present research was to investigate the influences of cognition on temporal processing of olfactory information in a health-relevant context. We investigated whether expecting an odor to cause adverse health effects alters perception of that odor. An irritation-free odor (Study 1: H(2)S; Study 2: phenyl ethyl alcohol [PEA]) was presented after which participants expected to experience either adverse sensory irritation (caused by intranasal CO(2) presentation) in one condition or no adverse effects in another condition, depending on a previously presented visual cue. ⋯ When the odor was PEA, only the N1 amplitude was increased. These results, obtained with OERP, provide converging evidence for comparable conclusions regarding the influence of cognition on odor perception reached with functional magnetic resonance imaging. Furthermore, the results suggest that a priori hedonic valence of an odor affects how susceptible the olfactory percept is to modulation via expectations.
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Whereas studies of somatotopic representation of touch have been useful to distinguish multiple somatosensory areas within primary (SI) and secondary (SII) somatosensory cortex regions, no such analysis exists for the representation of pain across nociceptive modalities. Here we investigated somatotopy in the operculo-insular cortex with noxious heat and pinprick stimuli in 11 healthy subjects using high-resolution (2 × 2 × 4 mm) 3T functional magnetic resonance imaging (fMRI). Heat stimuli (delivered using a laser) and pinprick stimuli (delivered using a punctate probe) were directed to the dorsum of the right hand and foot in a balanced design. ⋯ For pinprick stimuli, we also found somatotopy in the contralateral posterior insula (hand, 9 ± 10 mm anterior to foot, P < 0.05). Furthermore, the response to heat stimulation of the hand was 11 ± 12 mm anterior to the response to pinprick stimulation of the hand in the contralateral (left) anterior insula (P < 0.05). These results indicate the existence of multiple somatotopic representations for pain within the operculo-insular region in humans, possibly reflecting its importance as a sensory-integration site that directs emotional responses and behavior appropriately depending on the body site being injured.
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Intradermal cheek injection of pruitogens or algogens differentially elicits hindlimb scratching or forelimb wiping, suggesting that these behaviors distinguish between itch and pain. We studied whether pruritogens and algogens excite separate or overlapping populations of primary afferent and second-order trigeminal neurons in mice. Calcium imaging of primary sensory trigeminal ganglion (TG) cells showed that 15.4% responded to histamine, 5.8% to the protease-activated receptor (PAR)-2 agonist, 13.4% to allyl isothiocyanate (AITC), and 36.7% to capsaicin. ⋯ A minority of AITC-responsive Vc neurons responded to pruritogens, whereas most responded to capsaicin. These data indicate that most primary and higher-order trigeminal sensory neurons are activated by both pruritic and algesic stimuli, although a minority exhibit selectivity. The results are discussed in terms of population codes for itch and pain that result in distinct behavioral responses of hindlimb scratching and forelimb wiping that are mediated at lumbar and cervical segmental levels, respectively.
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Sphingosine 1-phosphate (S1P) through its interaction with a family of G protein-coupled receptors (S1PR) is proving to have a significant impact on the activation of a variety of cell types, most notably those cells mediating the inflammatory response. Previously, we showed that S1P enhanced the excitability of small diameter sensory neurons, and mRNA for S1PR(1-4) was expressed in sensory neurons. These initial findings did not determine which S1PR subtype(s) mediated the increased excitability. ⋯ Approximately 50% of the neurons exhibited a significant increase in excitability after exposure to SEW2871 and subsequent S1P produced no additional increase; ∼25% were not affected by SEW2871 but S1P significantly increased excitability; and ∼25% of the neurons were not sensitized by either SEW2871 or S1P. RT-PCR measurements obtained from single neurons showed that 50% of the small diameter neurons expressed the mRNA for S1PR(1). These results indicate that S1PR(1) plays a prominent, although not exclusive, role in mediating the enhancement of excitability produced by S1P.